Neutron interferometry constrains dark energy chameleon fields
Directory of Open Access Journals (Sweden)
H. Lemmel
2015-04-01
Full Text Available We present phase shift measurements for neutron matter waves in vacuum and in low pressure Helium using a method originally developed for neutron scattering length measurements in neutron interferometry. We search for phase shifts associated with a coupling to scalar fields. We set stringent limits for a scalar chameleon field, a prominent quintessence dark energy candidate. We find that the coupling constant β is less than 1.9×107 for n=1 at 95% confidence level, where n is an input parameter of the self-interaction of the chameleon field φ inversely proportional to φn.
Khoury, Justin
2013-01-01
Chameleons are light scalar fields with remarkable properties. Through the interplay of self-interactions and coupling to matter, chameleon particles have a mass that depends on the ambient matter density. The manifestation of the fifth force mediated by chameleons therefore depends sensitively on their environment, which makes for a rich phenomenology. In this article, we review two recent results on chameleon phenomenology. The first result a pair of no-go theorems limiting the cosmological impact of chameleons and their generalizations: i) the range of the chameleon force at cosmological density today can be at most ~Mpc; ii) the conformal factor relating Einstein- and Jordan-frame scale factors is essentially constant over the last Hubble time. These theorems imply that chameleons have negligible effect on the linear growth of structure, and cannot account for the observed cosmic acceleration except as some form of dark energy. The second result pertains to the quantum stability of chameleon theories. We ...
Chameleons with Field Dependent Couplings
Brax, Philippe; Mota, David F; Nunes, Nelson J; Winther, Hans A
2010-01-01
Certain scalar-tensor theories exhibit the so-called chameleon mechanism, whereby observational signatures of scalar fields are hidden by a combination of self-interactions and interactions with ambient matter. Not all scalar-tensor theories exhibit such a chameleon mechanism, which has been originally found in models with inverse power run-away potentials and field independent couplings to matter. In this paper we investigate field-theories with field-dependent couplings and a power-law potential for the scalar field. We show that the theory indeed is a chameleon field theory. We find the thin-shell solution for a spherical body and investigate the consequences for E\\"ot-Wash experiments, fifth-force searches and Casimir force experiments. Requiring that the scalar-field evades gravitational tests, we find that the coupling is sensitive to a mass-scale which is of order of the Hubble scale today.
Quantum Stability of Chameleon Field Theories
Upadhye, Amol; Khoury, Justin
2012-01-01
Chameleon scalar fields are dark energy candidates which suppress fifth forces in high density regions of the universe by becoming massive. We consider chameleon models as effective field theories and estimate quantum corrections to their potentials. Requiring that quantum corrections be small, so as to allow reliable predictions of fifth forces, leads to an upper bound $m 0.0042$\\,eV. An improvement of less than a factor of two in the range of fifth force experiments could test all classical chameleon field theories whose quantum corrections are well-controlled and couple to matter with nearly gravitational strength regardless of the specific form of the chameleon potential.
Tuning the Mass of Chameleon Fields in Casimir Force Experiments
Brax, Ph; Davis, A C; Shaw, D J; Iannuzzi, D
2010-01-01
We have calculated the chameleon pressure between two parallel plates in the presence of an intervening medium that affects the mass of the chameleon field. As intuitively expected, the gas in the gap weakens the chameleon interaction mechanism with a screening effect that increases with the plate separation and with the density of the intervening medium. This phenomenon might open up new directions in the search of chameleon particles with future long range Casimir force experiments.
Neutron Limit on the Strongly-Coupled Chameleon Field
Li, K; Cory, D G; Haun, R; Heacock, B; Huber, M G; Nsofini, J; Pushin, D A; Saggu, P; Sarenac, D; Shahi, C B; Skavysh, V; Snow, W M; Young, A R
2016-01-01
The physical origin of the dark energy that causes the accelerated expansion rate of the universe is one of the major open questions of cosmology. One set of theories postulates the existence of a self-interacting scalar field for dark energy coupling to matter. In the chameleon dark energy theory, this coupling induces a screening mechanism such that the field amplitude is nonzero in empty space but is greatly suppressed in regions of terrestrial matter density. However measurements performed under appropriate vacuum conditions can enable the chameleon field to appear in the apparatus, where it can be subjected to laboratory experiments. Here we report the most stringent upper bound on the free neutron-chameleon coupling in the strongly-coupled limit of the chameleon theory using neutron interferometric techniques. Our experiment sought the chameleon field through the relative phase shift it would induce along one of the neutron paths inside a perfect crystal neutron interferometer. The amplitude of the cham...
Application of the Chameleon Model to EM Field Momentum
Robertson, Glen A.
2008-01-01
The Chameleon scalar field model proposed by Khoury and Weltman presents an alternative mechanism for circumventing the constraints from local tests of gravity by mediating a fifth force for cosmological expansion, which could result in experimental signatures detectable through modest improvements of current laboratory set-ups in the vicinity of oscillating matter. In this paper, the oscillation of a dielectric by a crossed EM field is investigated in light of the Chameleon model. An EM excited Chameleon field-force equation is developed and compared to several EM experiments using the Barium Titanate based dielectric material.
Testing Chameleon Theories with Light Propagating through a Magnetic Field
Brax, P; Davis, A C; Mota, D F; Shaw, D J
2007-01-01
It was recently argued that the observed PVLAS anomaly can be explained by chameleon field theories in which large deviations from Newton's law can be avoided. Here we present the predictions for the dichroism and the birefringence induced in the vacuum by a magnetic field in these models. We show that chameleon particles behave very differently from standard axion-like particles (ALPs). We find that, unlike ALPs, the chameleon particles are confined within the experimental set-up. As a consequence, the birefringence is always bigger than the dichroism in PVLAS-type experiments.
Chameleon field and the late time acceleration of the Universe
Indian Academy of Sciences (India)
Narayan Banerjee; Sudipta Das; Koyel Ganguly
2010-03-01
In the present work, it is shown that a chameleon scalar field having a non-minimal coupling with dark matter can give rise to a smooth transition from a decelerated to an accelerated phase of expansion for the Universe. It is surprising to note that the coupling with the chameleon scalar field hardly affects the evolution of the dark matter sector, which still redshifts as −3.
Neutron limit on the strongly-coupled chameleon field
Li, K.; Arif, M.; Cory, D. G.; Haun, R.; Heacock, B.; Huber, M. G.; Nsofini, J.; Pushin, D. A.; Saggu, P.; Sarenac, D.; Shahi, C. B.; Skavysh, V.; Snow, W. M.; Young, A. R.; Index Collaboration
2016-03-01
The physical origin of the dark energy that causes the accelerated expansion rate of the Universe is one of the major open questions of cosmology. One set of theories postulates the existence of a self-interacting scalar field for dark energy coupling to matter. In the chameleon dark energy theory, this coupling induces a screening mechanism such that the field amplitude is nonzero in empty space but is greatly suppressed in regions of terrestrial matter density. However measurements performed under appropriate vacuum conditions can enable the chameleon field to appear in the apparatus, where it can be subjected to laboratory experiments. Here we report the most stringent upper bound on the free neutron-chameleon coupling in the strongly coupled limit of the chameleon theory using neutron interferometric techniques. Our experiment sought the chameleon field through the relative phase shift it would induce along one of the neutron paths inside a perfect crystal neutron interferometer. The amplitude of the chameleon field was actively modulated by varying the millibar pressures inside a dual-chamber aluminum cell. We report a 95% confidence level upper bound on the neutron-chameleon coupling β ranging from β <4.7 ×106 for a Ratra-Peebles index of n =1 in the nonlinear scalar field potential to β <2.4 ×107 for n =6 , one order of magnitude more sensitive than the most recent free neutron limit for intermediate n . Similar experiments can explore the full parameter range for chameleon dark energy in the foreseeable future.
Searching for Chameleon-like Scalar Fields
Levshakov, S A; Kozlov, M G; Lapinov, A V; Henkel, C; Reimers, D; Sakai, T; Agafonova, I I
2010-01-01
Using the 32-m Medicina, 45-m Nobeyama, and 100-m Effelsberg telescopes we found a statistically significant velocity offset Delta V = 27 +/- 3 m/s (1sigma) between the inversion transition in NH3(1,1) and low-J rotational transitions in N2H+(1-0) and HC3N(2-1) arising in cold and dense molecular cores in the Milky Way. Systematic shifts of the line centers caused by turbulent motions and velocity gradients, possible non-thermal hyperfine structure populations, pressure and optical depth effects are shown to be lower than or about 1 m/s and thus can be neglected in the total error budget. The reproducibility of Delta V at the same facility (Effelsberg telescope) on a year-to-year basis is found to be very good. Since the frequencies of the inversion and rotational transitions have different sensitivities to variations in mu = m_e/m_p, the revealed non-zero Delta V may imply that mu changes when measured at high (terrestrial) and low (interstellar) matter densities as predicted by chameleon-like scalar field m...
Effective field theory analysis of the self-interacting chameleon
Sanctuary, Hillary; Sturani, Riccardo
2010-08-01
We analyse the phenomenology of a self-interacting scalar field in the context of the chameleon scenario originally proposed by Khoury and Weltman. In the absence of self-interactions, this type of scalar field can mediate long range interactions and simultaneously evade constraints from violation of the weak equivalence principle. By applying to such a scalar field the effective field theory method proposed for Einstein gravity by Goldberger and Rothstein, we give a thorough perturbative evaluation of the importance of non-derivative self-interactions in determining the strength of the chameleon mediated force in the case of orbital motion. The self-interactions are potentially dangerous as they can change the long range behaviour of the field. Nevertheless, we show that they do not lead to any dramatic phenomenological consequence with respect to the linear case and solar system constraints are fulfilled.
No-Go Theorems for Generalized Chameleon Field Theories
Wang, Junpu; Khoury, Justin
2012-01-01
The chameleon, or generalizations thereof, is a light scalar that couple to matter with gravitational strength, but whose manifestation depends on the ambient matter density. A key feature is that the screening mechanism suppressing its effects in high-density environments is determined by the local scalar field value. Under very general conditions, we prove two theorems limiting its cosmological impact: i) the Compton wavelength of such a scalar can be at most Mpc at present cosmic density, which restricts its impact to non-linear scales; ii) the conformal factor relating Einstein- and Jordan-frame scale factors is essentially constant over the last Hubble time, which precludes the possibility of self-acceleration. These results imply that chameleon-like scalar fields have a negligible effect on the linear-scale growth history; theories that invoke a chameleon-like scalar to explain cosmic acceleration rely on a form of dark energy rather than a genuine modified gravity effect. Our analysis applies to a broa...
Numerical forecasts for lab experiments constraining modified gravity: the chameleon model
Schlogel, Sandrine; Fuzfa, Andre
2015-01-01
Current acceleration of the cosmic expansion leads to coincidence as well as fine-tuning issues in the framework of general relativity. Dynamical scalar fields have been introduced in response of these problems, some of them invoking screening mechanisms for passing local tests of gravity. Recent lab experiments based on atom interferometry in a vacuum chamber have been proposed for testing modified gravity models. So far only analytical computations have been used to provide forecasts. We derive numerical solutions for chameleon models that take into account the effect of the vacuum chamber wall and its environment. With this realistic profile of the chameleon field in the chamber, we refine the forecasts that were derived analytically. We finally highlight specific effects due to the vacuum chamber that are potentially interesting for future experiments.
Brax, Ph.; van de Bruck, C.; Davis, A. -C.
2007-01-01
We analyse the PVLAS results using a chameleon field whose properties depend on the environment. We find that, assuming a runaway bare potential $V(\\phi)$ and a universal coupling to matter, the chameleon potential is such that the scalar field can act as dark energy. Moreover the chameleon field model is compatible with the CAST results, fifth force experiments and cosmology.
Search for chameleon scalar fields with the axion dark matter experiment.
Rybka, G; Hotz, M; Rosenberg, L J; Asztalos, S J; Carosi, G; Hagmann, C; Kinion, D; van Bibber, K; Hoskins, J; Martin, C; Sikivie, P; Tanner, D B; Bradley, R; Clarke, J
2010-07-30
Scalar fields with a "chameleon" property, in which the effective particle mass is a function of its local environment, are common to many theories beyond the standard model and could be responsible for dark energy. If these fields couple weakly to the photon, they could be detectable through the afterglow effect of photon-chameleon-photon transitions. The ADMX experiment was used in the first chameleon search with a microwave cavity to set a new limit on scalar chameleon-photon coupling βγ excluding values between 2×10(9) and 5×10(14) for effective chameleon masses between 1.9510 and 1.9525 μeV.
Noller, Johannes
2012-01-01
We consider generalized chameleon models where the conformal coupling between matter and gravitational geometries is not only a function of the chameleon field \\phi, but also of its derivatives via higher order co-ordinate invariants. Specifically we consider the first such non-trivial conformal factor A(\\phi,X), where X is the canonical kinetic term for \\phi. The associated phenomenology is investigated and we show that such theories have a new generic mass-altering mechanism, potentially assisting the generation of a sufficiently large chameleon mass in dense environments. The most general effective potential is derived for such derivative chameleon setups and explicit examples are given. Interestingly this points us to the existence of a purely derivative chameleon protected by a shift symmetry for \\phi. We also discuss potential ghost-like instabilities associated with mass-lifting mechanisms and find another, mass-lowering and instability-free, branch of solutions. This suggests that, barring fine-tuning...
Noller, Johannes
2012-07-01
We consider generalized chameleon models where the conformal coupling between matter and gravitational geometries is not only a function of the chameleon field phi, but also of its derivatives via higher order co-ordinate invariants (such as ∂μphi∂μphi,squphi,...). Specifically we consider the first such non-trivial conformal factor A(phi,∂μphi∂μphi). The associated phenomenology is investigated and we show that such theories have a new generic mass-altering mechanism, potentially assisting the generation of a sufficiently large chameleon mass in dense environments. The most general effective potential is derived for such derivative chameleon setups and explicit examples are given. Interestingly this points us to the existence of a purely derivative chameleon protected by a shift symmetry for phi → phi+c. We also discuss potential ghost-like instabilities associated with mass-lifting mechanisms and find another, mass-lowering and instability-free, branch of solutions. This suggests that, barring fine-tuning, stable derivative models are in fact typically anti-chameleons that suppress the field's mass in dense environments. Furthermore we investigate modifications to the thin-shell regime and prove a no-go theorem for chameleon effects in non-conformal geometries of the disformal type.
Brax, Philippe; van de Bruck, Carsten; Davis, Anne-Christine
2007-09-01
We analyze the PVLAS results using a chameleon field whose properties depend on the environment. We find that, assuming a runaway bare potential V(ϕ) and a universal coupling to matter, the chameleon potential is such that the scalar field can act as dark energy. Moreover, the chameleon-field model is compatible with the CERN Axion Solar Telescope results, fifth-force experiments, and cosmology.
Brax, Philippe; van de Bruck, Carsten; Davis, Anne-Christine
2007-09-21
We analyze the PVLAS results using a chameleon field whose properties depend on the environment. We find that, assuming a runaway bare potential V(phi) and a universal coupling to matter, the chameleon potential is such that the scalar field can act as dark energy. Moreover, the chameleon-field model is compatible with the CERN Axion Solar Telescope results, fifth-force experiments, and cosmology.
Chameleon-Photon Mixing in a Primordial Magnetic Field
Schelpe, Camilla A O
2010-01-01
We consider the non-resonant mixing between photons and scalar axion-like particles (ALPs) in a primordial magnetic field, with specific reference to the chameleon scalar field model. This mixing would affect the intensity and polarization state of the cosmic microwave background (CMB) radiation. We find that the average modification to the CMB polarization modes is negligible. However the average modification to the CMB intensity spectrum is more significant and we compare this to high precision measurements of the CMB monopole made by the far infrared absolute spectrophotometer (FIRAS) on board the COBE satellite. The resulting 95% confidence limit on the scalar-photon conversion probability in the primordial field (at 100 GHz) is P < 2.6x10^{-2}. This corresponds to a degenerate constraint on the photon-scalar coupling strength, g, and the magnitude of the primordial magnetic field. Taking the 95% confidence upper bound on the strength of the primordial magnetic field found by Kahniashvili et al., this ...
Alpenglow. A signature for chameleons in axion-like particle search experiments
Energy Technology Data Exchange (ETDEWEB)
Ahlers, M.; Lindner, A.; Ringwald, A.; Schrempp, L.; Weniger, C.
2007-10-15
We point out that chameleon field theories might reveal themselves as an ''afterglow'' effect in axion-like particle search experiments due to chameleon-photon conversion in a magnetic field. We estimate the parameter space which is accessible by currently available technology and find that afterglow experiments could constrain this parameter space in a way complementary to gravitational and Casimir force experiments.In addition, one could reach photon-chameleon couplings which are beyond the sensitivity of common laser polarization experiments. We also sketch the idea of a Fabry-Perot cavity with chameleons which could increase the experimental sensitivity significantly. (orig.)
Chameleonic Theories: A Short Review
Directory of Open Access Journals (Sweden)
Andrea Zanzi
2015-12-01
Full Text Available In the chameleon mechanism, a field (typically scalar has a mass that depends on the matter density of the environment: the larger is the matter density, the larger is the mass of the chameleon. We briefly review some aspects of chameleonic theories. In particular, in a typical class of these theories, we discuss the lagrangian, the role of conformal transformations, the equation of motion and the thin-shell effect. We also discuss f ( R theories and chameleonic quantum gravity.
Hinterbichler, Kurt; Nastase, Horatiu; Rosenfeld, Rogerio
2013-01-01
We attempt to incorporate inflation into a string theory realization of the chameleon mechanism. Previously, it was found that the volume modulus, stabilized by the supersymmetric potential used by Kachru, Kallosh, Linde and Trivedi (KKLT) and with the right choice of parameters, can generically work as a chameleon. In this paper, we ask whether inflation can be realized in the same model. We find that we need a large extra dimensions set-up, as well as a semi-phenomenological deformation of the Kahler potential in the quantum region. We also find that an additional KKLT term is required so that there are now two pieces to the potential, one which drives inflation in the early universe, and one which is responsible for chameleon screening at late times. These two pieces of the potential are separated by a large flat desert in field space. The scalar field must dynamically traverse this desert between the end of inflation and today, and we find that this can indeed occur under the right conditions.
Testing chameleon gravity with the Coma cluster
Terukina, Ayumu; Yamamoto, Kazuhiro; Bacon, David; Koyama, Kazuya; Nichol, Robert C
2013-01-01
We propose a novel method to test the gravitational interactions in the outskirts of galaxy clusters. When gravity is modified, this is typically accompanied by an introduction of an additional scalar degree of freedom, which mediates an attractive fifth force. The presence of an extra gravitational coupling, however, is tightly constrained by local measurements. In chameleon modifications of gravity, local tests can be evaded by employing a screening mechanism that suppresses the fifth force in dense environments. While the chameleon field may be screened in the interior of the cluster, its outer region can still be affected by the extra force, introducing a deviation between the hydrostatic and lensing mass of the cluster. Thus, the chameleon modification can be tested by combining the gas and lensing measurements of the cluster. We demonstrate the operability of our method with the Coma cluster, for which both a lensing measurement and gas observations from the X-ray surface brightness, the X-ray temperatu...
Experimental demonstration of a fifth force due to chameleon field via cold atoms
Zhang, Hai-Chao
2017-01-01
We tested a fifth force using cold atom experiments. The accelerated expansion of the universe implies the possibility of the presence of a scalar field throughout the universe driving the acceleration. This field would result in a detectable force between normal-matter objects. Theory of the chameleon field states that the force should be strong in a thin shell near the surface of a source object but greatly suppressed inside and outside of the source object. We used two atom clouds: one as ...
Has PVLAS Detected the Chameleon?
Brax, P; De van Bruck, C; Brax, Ph.
2007-01-01
We show that the PVLAS anomaly can be understood using a chameleon field whose properties depend on the environment. We find that, assuming a runaway bare potential V(phi) and a universal coupling to matter, the chameleon potential is such that the scalar field can act as dark energy. Moreover the chameleon field model is compatible with the CAST results, fifth force experiments and cosmology.
Energy Technology Data Exchange (ETDEWEB)
Chattopadhyay, Surajit [Pailan College of Management and Technology, Kolkata (India); Pasqua, Antonio [University of Trieste, Department of Physics, Trieste (Italy); Khurshudyan, Martiros [Yerevan State University, Department of Theoretical Physics, Yerevan (Armenia); Potsdam-Golm Science Park, Max Planck Institute of Colloids and Interfaces, Potsdam (Germany)
2014-09-15
Motivated by the work of Yang et al. (Mod. Phys. Lett. A 26:191, 2011), we report on a study of the new holographic dark energy (NHDE) model with energy density given by ρ{sub D} = (3φ{sup 2})/(4ω)(μH{sup 2} + νH) in the framework of chameleon Brans-Dicke cosmology. We have studied the correspondence between the quintessence, the DBI-essence, and the tachyon scalar-field models with the NHDE model in the framework of chameleon Brans-Dicke cosmology. Deriving an expression of the Hubble parameter H and, accordingly, ρ{sub D} in the context of chameleon Brans-Dicke chameleon cosmology, we have reconstructed the potentials and dynamics for these scalar-field models. Furthermore, we have examined the stability for the obtained solutions of the crossing of the phantom divide under a quantum correction of massless conformally invariant fields, and we have seen that the quantum correction could be small when the phantom crossing occurs and the obtained solutions of the phantom crossing could be stable under the quantum correction. It has also been noted that the potential increases as the matter. chameleon coupling gets stronger with the evolution of the universe. (orig.)
Chameleon gravity and satellite geodesy
Morris, J R
2014-01-01
We consider the possibility of the detection of a chameleon effect by an earth orbiting satellite such as LAGEOS, and possible constraints that might be placed on chameleon model parameters. Approximate constraints presented here result from using a simple monopole approximation for the gravitational field of the earth, along with results from the Khoury-Weltman chameleon model, solar system constraints obtained from the Cassini mission, and parameter bounds obtained from the LAGEOS satellite. It is furthermore suggested that a comparison of ground-based and space-based multipole moments of the geopotential could reveal a possible chameleon effect.
Holographic dark energy in Brans-Dicke cosmology with chameleon scalar field
Energy Technology Data Exchange (ETDEWEB)
Setare, M.R., E-mail: rezakord@ipm.i [Department of Science of Bijar, University of Kurdistan, Bijar (Iran, Islamic Republic of); Jamil, Mubasher, E-mail: mjamil@camp.edu.p [Center for Advanced Mathematics and Physics, National University of Sciences and Technology, Rawalpindi 46000 (Pakistan)
2010-06-07
We study a cosmological implication of holographic dark energy in the Brans-Dicke gravity. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named L. Our analysis shows that one can obtain the phantom crossing scenario if the model parameter {alpha} (of order unity) is tuned accordingly. Moreover, this behavior is achieved by treating the Brans-Dicke scalar field as a Chameleon scalar field and taking a non-minimal coupling of the scalar field with matter. Hence one can generate phantom-like equation of state from a holographic dark energy model in non-flat universe in the Brans-Dicke cosmology framework.
A Compendium of Chameleon Constraints
Burrage, Clare
2016-01-01
The chameleon model is a scalar field theory with a screening mechanism that explains how a cosmologically relevant light scalar can avoid the constraints of intra-solar-system searches for fifth-forces. The chameleon is a popular dark energy candidate and also arises in $f(R)$ theories of gravity. Whilst the chameleon is designed to avoid historical searches for fifth-forces it is not unobservable and much effort has gone into identifying the best observables and experiments to detect it. These results are not always presented for the same models or in the same language, a particular problem when comparing astrophysical and laboratory searches making it difficult to understand what regions of parameter space remain. Here we present combined constraints on the chameleon model from astrophysical and laboratory searches for the first time and identify the remaining windows of parameter space. We discuss the implications for cosmological chameleon searches and future small-scale probes.
A compendium of chameleon constraints
Burrage, Clare; Sakstein, Jeremy
2016-11-01
The chameleon model is a scalar field theory with a screening mechanism that explains how a cosmologically relevant light scalar can avoid the constraints of intra-solar-system searches for fifth-forces. The chameleon is a popular dark energy candidate and also arises in f(R) theories of gravity. Whilst the chameleon is designed to avoid historical searches for fifth-forces it is not unobservable and much effort has gone into identifying the best observables and experiments to detect it. These results are not always presented for the same models or in the same language, a particular problem when comparing astrophysical and laboratory searches making it difficult to understand what regions of parameter space remain. Here we present combined constraints on the chameleon model from astrophysical and laboratory searches for the first time and identify the remaining windows of parameter space. We discuss the implications for cosmological chameleon searches and future small-scale probes.
Brax, Philippe
2010-01-01
We analyse the creation of chameleons deep inside the sun and their subsequent conversion to photons near the magnetised surface of the sun. We find that the spectrum of the regenerated photons lies in the soft X-ray region, hence addressing the solar corona problem. Moreover, these back-converted photons originating from chameleons have an intrinsic difference with regenerated photons from axions: their relative polarisations are mutually orthogonal before Compton interacting with the surrounding plasma. Depending on the photon-chameleon coupling and working in the strong coupling regime of the chameleons to matter, we find that the induced photon flux, when regenerated resonantly with the surrounding plasma, coincides with the solar flux within the soft X-ray energy range. Moreover, using the soft X-ray solar flux as a prior, we find that with a strong enough photon-chameleon coupling the chameleons emitted by the sun could lead to a regenerated photon flux in the CAST pipes, which could be within the reach...
Brax, Philippe
2015-01-01
We extend the chameleon models by considering Scalar-Fluid theories where the coupling between matter and the scalar field can be represented by a quadratic effective potential with density-dependent minimum and mass. In this context, we study the effects of the scalar field on Solar System tests of gravity and show that models passing these stringent constraints can still induce large modifications of Newton's law on galactic scales. On these scales we analyse models which could lead to a percent deviation of Newton's law outside the virial radius. We then model the dark matter halo as a Navarro-Frenk-White profile and explicitly find that the fifth force can give large contributions around the galactic core in a particular model where the scalar field mass is constant and the minimum of its potential varies linearly with the matter density. At cosmological distances, we find that this model does not alter the growth of large scale structures and therefore would be best tested on galactic scales, where inter...
Equivalence principle in Chameleon models .
Kraiselburd, L.; Landau, S.; Salgado, M.; Sudarsky, D.
Most theories that predict time and/or space variation of fundamental constants also predict violations of the Weak Equivalence Principle (WEP). Khoury and Weltmann proposed the chameleon model in 2004 and claimed that this model avoids experimental bounds on WEP. We present a contrasting view based on an approximate calculation of the two body problem for the chameleon field and show that the force depends on the test body composition. Furthermore, we compare the prediction of the force on a test body with Eötvös type experiments and find that the chameleon field effect cannot account for current bounds.
Equivalence Principle in Chameleon Models
Kraiselburd, Lucila; Salgado, Marcelo; Sudarsky, Daniel
2013-01-01
Most theories that predict time and/or space variation of fundamental constants also predict violations of the Weak Equivalence Principle (WEP). Khoury and Weltmann proposed the chameleon model in 2004 and claimed that this model avoids experimental bounds on WEP. We present a contrasting view based on an approximate calculation of the two body problem for the chameleon field and show that the force depends on the test body composition. Furthermore, we compare the prediction of the force on a test body with E\\"otv\\"os type experiments and find that the chameleon field effect cannot account for current bounds.
Catastrophic Consequences of Kicking the Chameleon
Erickcek, Adrienne L; Burrage, Clare; Huang, Zhiqi
2013-01-01
The physics of the "dark energy" that drives the current cosmological acceleration remains mysterious, and the dark sector may involve new light dynamical fields. If these light scalars couple to matter, a screening mechanism must prevent them from mediating an unacceptably strong fifth force locally. Here we consider a concrete example: the chameleon mechanism. We show that the same coupling between the chameleon field and matter employed by the screening mechanism also has catastrophic consequences for the chameleon during the Universe's first minutes. The chameleon couples to the trace of the stress-energy tensor, which is temporarily non-zero in a radiation-dominated universe whenever a particle species becomes non-relativistic. These "kicks" impart a significant velocity to the chameleon field, causing its effective mass to vary non-adiabatically and resulting in the copious production of quantum fluctuations. Dissipative effects strongly modify the background evolution of the chameleon field, invalidati...
Search for chameleons with CAST
Directory of Open Access Journals (Sweden)
V. Anastassopoulos
2015-10-01
Full Text Available In this work we present a search for (solar chameleons with the CERN Axion Solar Telescope (CAST. This novel experimental technique, in the field of dark energy research, exploits both the chameleon coupling to matter (βm and to photons (βγ via the Primakoff effect. By reducing the X-ray detection energy threshold used for axions from 1 keV to 400 eV CAST became sensitive to the converted solar chameleon spectrum which peaks around 600 eV. Even though we have not observed any excess above background, we can provide a 95% C.L. limit for the coupling strength of chameleons to photons of βγ≲1011 for 1<βm<106.
Search for chameleons with CAST
Anastassopoulos, V; Aune, S; Barth, K; Belov, A; Bräuninger, H; Cantatore, G; Carmona, J M; Cetin, S A; Christensen, F; Collar, J I; Dafni, T; Davenport, M; Desch, K; Dermenev, A; Eleftheriadis, C; Fanourakis, G; Ferrer-Ribas, E; Friedrich, P; Galán, J; García, J A; Gardikiotis, A; Garza, J G; Gazis, E N; Geralis, T; Giomataris, I; Hailey, C; Haug, F; Hasinoff, M D; Hofmann, D H H; Iguaz, F J; Irastorza, I G; Jacoby, J; Jakobsen, A; Jakovčić, K; Kaminski, J; Karuza, M; Kavuk, M; Krčmar, M; Krieger, C; Krüger, A; Lakić, B; Laurent, J M; Liolios, A; Ljubičić, A; Luzón, G; Neff, S; Ortega, I; Papaevangelou, T; Pivovarov, M J; Raffelt, G; Riege, H; Rosu, M; Ruz, J; Savvidis, I; Solanki, S K; Vafeiadis, T; Villar, J A; Vogel, J K; Yildiz, S C; Zioutas, K; Brax, P; Lavrentyev, I; Upadhye, A
2015-01-01
In this work we present a search for (solar) chameleons with the CERN Axion Solar Telescope (CAST). This novel experimental technique, in the field of dark energy research, exploits both the chameleon coupling to matter ($\\beta_{\\rm m}$) and to photons ($\\beta_{\\gamma}$) via the Primakoff effect. By reducing the X-ray detection energy threshold used for axions from 1$\\,$keV to 400$\\,$eV CAST became sensitive to the converted solar chameleon spectrum which peaks around 600$\\,$eV. Even though we have not observed any excess above background, we can provide a 95% C.L. limit for the coupling strength of chameleons to photons of $\\beta_{\\gamma}\\!\\lesssim\\!10^{11}$ for $1<\\beta_{\\rm m}<10^6$.
Petersen, Hugh
2009-01-01
This article presents an art project inspired by a drawing of a chameleon the author saw in an art-supply catalog. Chameleons prove to be a good subject to highlight shape, color and texture with eigth-graders. In this project, middle- and high-school students draw a chameleon, learn how to use shapes to add to their chameleon drawing, learn how…
Coding for Two Dimensional Constrained Fields
DEFF Research Database (Denmark)
Laursen, Torben Vaarbye
2006-01-01
for the No Isolated Bits constraint. Finally we present a variation of the encoding scheme of bit-stuffing that is applicable to the class of checkerboard constrained fields. It is possible to calculate the entropy of the coding scheme thus obtaining lower bounds on the entropy of the fields considered. These lower....... The important concept of entropy is introduced. In general, the entropy of a constrained field is not readily computable, but we give a series of upper and lower bounds based on one dimensional techniques. We discuss the use of a Pickard probability model for constrained fields. The novelty lies in using...... bounds are very tight for the Run-Length limited fields. Explicit bounds are given for the diamond constrained field as well....
Towards weakly constrained double field theory
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Kanghoon Lee
2016-08-01
Full Text Available We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.
Towards weakly constrained double field theory
Lee, Kanghoon
2016-08-01
We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon) transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.
Towards Weakly Constrained Double Field Theory
Lee, Kanghoon
2015-01-01
We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon) transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X- ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.
Diabatic constrained relativistic mean field approach
L"u, H F; Meng, J
2005-01-01
A diabatic (configuration-fixed) constrained approach to calculate the potential energy surface (PES) of the nucleus is developed in the relativistic mean field model. The potential energy surfaces of $^{208}$Pb obtained from both adiabatic and diabatic constrained approaches are investigated and compared. The diabatic constrained approach enables one to decompose the segmented PES obtained in usual adiabatic approaches into separate parts uniquely characterized by different configurations, to define the single particle orbits at very deformed region by their quantum numbers, and to obtain several well defined deformed excited states which can hardly be expected from the adiabatic PES's.
How to Avoid a Swift Kick in the Chameleons
Padilla, Antonio; Stefanyszyn, David; Walters, Anthony; Weltman, Amanda; Wilson, Toby
2015-01-01
Recently, it was argued that the conformal coupling of the chameleon to matter fields created an issue for early universe cosmology. As standard model degrees of freedom become non-relativistic in the early universe, the chameleon is attracted towards a "surfing" solution, so that it arrives at the potential minimum with too large a velocity. This leads to rapid variations in the chameleon's mass and excitation of high energy modes, casting doubts on the classical treatment at Big Bang Nucleosynthesis. Here we present the DBI chameleon, a consistent high energy modification of the chameleon theory that dynamically renders it weakly coupled to matter during the early universe thereby eliminating the adverse effects of the `kicks'. This is done without any fine tuning of the coupling between the chameleon and matter fields, and retains its screening ability in the solar system. We demonstrate this explicitly with a combination of analytic and numerical results.
How to avoid a swift kick in the chameleons
Padilla, Antonio; Platts, Emma; Stefanyszyn, David; Walters, Anthony; Weltman, Amanda; Wilson, Toby
2016-03-01
Recently, it was argued that the conformal coupling of the chameleon to matter fields created an issue for early universe cosmology. As standard model degrees of freedom become non-relativistic in the early universe, the chameleon is attracted towards a ``surfing'' solution, so that it arrives at the potential minimum with too large a velocity. This leads to rapid variations in the chameleon's mass and excitation of high energy modes, casting doubts on the classical treatment at Big Bang Nucleosynthesis. Here we present the DBI chameleon, a consistent high energy modification of the chameleon theory that dynamically renders it weakly coupled to matter during the early universe thereby eliminating the adverse effects of the `kicks'. This is done without any fine tuning of the coupling between the chameleon and matter fields, and retains its screening ability in the solar system. We demonstrate this explicitly with a combination of analytic and numerical results.
Equivalence Principle in Chameleon Models
Kraiselburd, Lucila; Salgado, Marcelo; Sudarsky, Daniel; Vucetich, Héctor
2015-01-01
Most theories that predict time and(or) space variation of fundamental constants also predict violations of the Weak Equivalence Principle (WEP). Khoury and Weltman proposed the chameleon model in 2004 and claimed that this model avoids experimental bounds on the WEP. In this paper we present a contrasting view based on the analysis of the force between two bodies induced by the chameleon field using a particular approach in which the field due to both the large and the small bodies is obtained by appropriate series expansions in the various regions of interest and the corresponding matching conditions. We found that resulting force depends on the test body\\'{}s composition even when the chameleon coupling constants $\\beta_{i}$ are universal. In particular, we compared the resulting differential acceleration of test bodies made of Be and Al with the corresponding bounds obtained from E\\"otv\\"os type experiments and find that the predictions of the chameleon model are, in general, various orders of magnitude a...
Chameleon effect and the Pioneer anomaly
Anderson, John D
2012-01-01
The possibility that the apparent anomalous acceleration of the Pioneer 10 and 11 spacecraft may be due, at least in part, to a chameleon field effect is examined. A small spacecraft, with no thin shell, can have a more pronounced anomalous acceleration than a large compact body, such as a planet, having a thin shell. The chameleon effect seems to present a natural way to explain the differences seen in deviations from pure Newtonian gravity for a spacecraft and for a planet, and appears to be compatible with the basic features of the Pioneer anomaly, including the appearance of a jerk term. However, estimates of the size of the chameleon effect indicate that its contribution to the anomalous acceleration is negligible. We conclude that any inverse-square component in the anomalous acceleration is more likely caused by an unmodelled reaction force from solar-radiation pressure, rather than a chameleon field effect.
Detecting Chameleons through Casimir Force Measurements
Brax, Philippe; Davis, Anne-Christine; Mota, David F; Shaw, Douglas
2007-01-01
The best laboratory constraints on strongly coupled chameleon fields come not from tests of gravity per se but from precision measurements of the Casimir force. The chameleonic force between two nearby bodies is more akin to a Casimir-like force than a gravitational one: The chameleon force behaves as an inverse power of the distance of separation between the surfaces of two bodies, just as the Casimir force does. Additionally, experimental tests of gravity often employ a thin metallic sheet to shield electrostatic forces, however this sheet mask any detectable signal due to the presence of a strongly coupled chameleon field. As a result of this shielding, experiments that are designed to specifically test the behaviour of gravity are often unable to place any constraint on chameleon fields with a strong coupling to matter. Casimir force measurements do not employ a physical electrostatic shield and as such are able to put tighter constraints on the properties of chameleons fields with a strong matter couplin...
The Chameleon Solid Rocket Propulsion Model
Robertson, Glen A.
2010-01-01
The Khoury and Weltman (2004a and 2004b) Chameleon Model presents an addition to the gravitation force and was shown by the author (Robertson, 2009a and 2009b) to present a new means by which one can view other forces in the Universe. The Chameleon Model is basically a density-dependent model and while the idea is not new, this model is novel in that densities in the Universe to include the vacuum of space are viewed as scalar fields. Such an analogy gives the Chameleon scalar field, dark energy/dark matter like characteristics; fitting well within cosmological expansion theories. In respect to this forum, in this paper, it is shown how the Chameleon Model can be used to derive the thrust of a solid rocket motor. This presents a first step toward the development of new propulsion models using density variations verse mass ejection as the mechanism for thrust. Further, through the Chameleon Model connection, these new propulsion models can be tied to dark energy/dark matter toward new space propulsion systems utilizing the vacuum scalar field in a way understandable by engineers, the key toward the development of such systems. This paper provides corrections to the Chameleon rocket model in Robertson (2009b).
Quartic Chameleons: Safely Scale-Free in the Early Universe
Miller, Carisa
2016-01-01
In chameleon gravity, there exists a light scalar field that couples to the trace of the stress-energy tensor in such a way that its mass depends on the ambient matter density, and the field is screened in local, high-density environments. Recently it was shown that, for the runaway potentials commonly considered in chameleon theories, the field's coupling to matter and the hierarchy of scales between Standard Model particles and the energy scale of such potentials result in catastrophic effects in the early Universe when these particles become nonrelativistic. Perturbations with trans-Planckian energies are excited, and the theory suffers a breakdown in calculability at the relatively low temperatures of Big Bang Nucleosynthesis. We consider a chameleon field in a quartic potential and show that the scale-free nature of this potential allows the chameleon to avoid many of the problems encountered by runaway potentials. Following inflation, the chameleon field oscillates around the minimum of its effective po...
Detecting solar chameleons through radiation pressure
Directory of Open Access Journals (Sweden)
S. Baum
2014-12-01
Full Text Available Light scalar fields can drive the accelerated expansion of the universe. Hence, they are obvious dark energy candidates. To make such models compatible with tests of General Relativity in the solar system and “fifth force” searches on Earth, one needs to screen them. One possibility is the so-called “chameleon” mechanism, which renders an effective mass depending on the local matter density. If chameleon particles exist, they can be produced in the sun and detected on Earth exploiting the equivalent of a radiation pressure. Since their effective mass scales with the local matter density, chameleons can be reflected by a dense medium if their effective mass becomes greater than their total energy. Thus, under appropriate conditions, a flux of solar chameleons may be sensed by detecting the total instantaneous momentum transferred to a suitable opto-mechanical force/pressure sensor. We calculate the solar chameleon spectrum and the reach in the chameleon parameter space of an experiment using the preliminary results from a force/pressure sensor, currently under development at INFN Trieste, to be mounted in the focal plane of one of the X-Ray telescopes of the CAST experiment at CERN. We show, that such an experiment signifies a pioneering effort probing uncharted chameleon parameter space.
Nastase, Horatiu
2013-01-01
We modify the ansatz for embedding chameleon scalars in string theory proposed in [1] by considering a racetrack superpotential with two KKLT-type exponentials $e^{ia\\varrho}$ instead of one. This satisfies all experimental constraints, while also allowing for the chameleon to be light enough on cosmological scales to be phenomenologically interesting.
Chameleons in the Early Universe: Kicks, Rebounds, and Particle Production
Erickcek, Adrienne L; Burrage, Clare; Huang, Zhiqi
2013-01-01
Chameleon gravity is a scalar-tensor theory that includes a non-minimal coupling between the scalar field and the matter fields and yet mimics general relativity in the Solar System. The scalar degree of freedom is hidden in high-density environments because the effective mass of the chameleon scalar depends on the trace of the stress-energy tensor. In the early Universe, when the trace of the matter stress-energy tensor is nearly zero, the chameleon is very light, and Hubble friction prevents it from reaching the minimum of its effective potential. Whenever a particle species becomes non-relativistic, however, the trace of the stress-energy tensor is temporarily nonzero, and the chameleon begins to roll. We show that these "kicks" to the chameleon field have catastrophic consequences for chameleon gravity. The velocity imparted to the chameleon by the kick is sufficiently large that the chameleon's mass changes rapidly as it slides past its potential minimum. This nonadiabatic evolution shatters the chameleo...
Propulsion in the Chameleon Model
Robertson, Glen A.
2008-01-01
The Chameleon model-thin-shell mechanism-proposed by Khoury and Weltman presents a likeness to a stationary warp bubble about masses of significant size and interest to space propulsion. A difference being that the thin-shell mechanism masks the mass of an object from an external Chameleon field comparable to the gravitational field in warp-drive theory. However, the thin-shell mechanism couples to the gravitational field by causing small perturbations limited to an object's effective range, which in essence could act like a warp-bubble under some ``yet to be defined'' conditions where the coupling is made stronger. In this paper, the thin-shell mechanism is discussed and shown to be the underlying physics behind rocket propulsion through the concept of localized oscillating dark matter comprising an increase in the thin-shell localized to a region on one side of an object. This is accomplished by drawing a connection between the localized oscillation of dark matter in this thin-shell region and the rocket equations. As such, it appears that a new physics effect is applied to normal matter; indicating that the results should have been observed decades ago. We argue that the Chameleon Model's thin-shell mechanism is a dark matter/energy field, which has always been in all momentum systems at or above the atomic scale where the mass has some physical significance in respect to the Chameleon model. Therefore, its physical (momentum) effects have already been observed. Further, since the analysis indicates that any motion of an object implies a change to the distribution of dark matter about an object, one can speculate that ``inertia is the change in the dark energy distribution about a mass.'' This being the case, the Chameleon dark matter/energy field about a mass has effects in many aspects of physics, but the laws have not (yet) been formulated to take advantage of the vacuum field aspects, which may provide the connection needed to extend modern rocketry to
Chameleon dark energy and atom interferometry
Elder, Benjamin; Khoury, Justin; Haslinger, Philipp; Jaffe, Matt; Müller, Holger; Hamilton, Paul
2016-08-01
Atom interferometry experiments are searching for evidence of chameleon scalar fields with ever-increasing precision. As experiments become more precise, so too must theoretical predictions. Previous work has made numerous approximations to simplify the calculation, which in general requires solving a three-dimensional nonlinear partial differential equation. This paper calculates the chameleonic force using a numerical relaxation scheme on a uniform grid. This technique is more general than previous work, which assumed spherical symmetry to reduce the partial differential equation to a one-dimensional ordinary differential equation. We examine the effects of approximations made in previous efforts on this subject and calculate the chameleonic force in a setup that closely mimics the recent experiment of Hamilton et al. Specifically, we simulate the vacuum chamber as a cylinder with dimensions matching those of the experiment, taking into account the backreaction of the source mass, its offset from the center, and the effects of the chamber walls. Remarkably, the acceleration on a test atomic particle is found to differ by only 20% from the approximate analytical treatment. These results allow us to place rigorous constraints on the parameter space of chameleon field theories, although ultimately the constraint we find is the same as the one we reported in Hamilton et al. because we had slightly underestimated the size of the vacuum chamber. This computational technique will continue to be useful as experiments become even more precise and will also be a valuable tool in optimizing future searches for chameleon fields and related theories.
Chameleonic equivalence postulate and wave function collapse
Zanzi, Andrea
2014-01-01
A chameleonic solution to the cosmological constant problem and the non-equivalence of different conformal frames at the quantum level have been recently suggested [Phys. Rev. D82 (2010) 044006]. In this article we further discuss the theoretical grounds of that model and we are led to a chameleonic equivalence postulate (CEP). Whenever a theory satisfies our CEP (and some other additional conditions), a density-dependence of the mass of matter fields is naturally present. Let us summarize the main results of this paper. 1) The CEP can be considered the microscopic counterpart of the Einstein's Equivalence Principle and, hence, a chameleonic description of quantum gravity is obtained: in our model, (quantum) gravitation is equivalent to a conformal anomaly. 2) To illustrate one of the possible applications of the CEP, we point out a connection between chameleon fields and quantum-mechanical wave function collapse. The collapse is induced by the chameleonic nature of the theory. We discuss the collapse for a S...
A natural cosmological constant from chameleons
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Horatiu Nastase
2015-07-01
Full Text Available We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero and the coincidence problem (why Λ is comparable to the matter density now.
A natural cosmological constant from chameleons
Energy Technology Data Exchange (ETDEWEB)
Nastase, Horatiu, E-mail: nastase@ift.unesp.br [Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, R. Dr. Bento T. Ferraz 271, Bl. II, Sao Paulo 01140-070, SP (Brazil); Weltman, Amanda, E-mail: amanda.weltman@uct.ac.za [Astrophysics, Cosmology & Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa)
2015-07-30
We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)
Chameleon Dark Energy and Atom Interferometry
Elder, Benjamin; Haslinger, Philipp; Jaffe, Matt; Müller, Holger; Hamilton, Paul
2016-01-01
Atom interferometry experiments are searching for evidence of chameleon scalar fields with ever-increasing precision. As experiments become more precise, so too must theoretical predictions. Previous work has made numerous approximations to simplify the calculation, which in general requires solving a 3-dimensional nonlinear partial differential equation (PDE). In this paper, we introduce a new technique for calculating the chameleonic force, using a numerical relaxation scheme on a uniform grid. This technique is more general than previous work, which assumed spherical symmetry to reduce the PDE to a 1-dimensional ordinary differential equation (ODE). We examine the effects of approximations made in previous efforts on this subject, and calculate the chameleonic force in a set-up that closely mimics the recent experiment of Hamilton et al. Specifically, we simulate the vacuum chamber as a cylinder with dimensions matching those of the experiment, taking into account the backreaction of the source mass, its o...
Brax, Philippe; Tamanini, Nicola
2016-05-01
We extend the chameleon models by considering scalar-fluid theories where the coupling between matter and the scalar field can be represented by a quadratic effective potential with density-dependent minimum and mass. In this context, we study the effects of the scalar field on Solar System tests of gravity and show that models passing these stringent constraints can still induce large modifications of Newton's law on galactic scales. On these scales we analyze models which could lead to a percent deviation of Newton's law outside the virial radius. We then model the dark matter halo as a Navarro-Frenk-White profile and explicitly find that the fifth force can give large contributions around the galactic core in a particular model where the scalar field mass is constant and the minimum of its potential varies linearly with the matter density. At cosmological distances, we find that this model does not alter the growth of large scale structures and therefore would be best tested on galactic scales, where interesting signatures might arise in the galaxy rotation curves.
Propulsion Physics Using the Chameleon Density Model
Robertson, Glen A.
2011-01-01
To grow as a space faring race, future spaceflight systems will require a new theory of propulsion. Specifically one that does not require mass ejection without limiting the high thrust necessary to accelerate within or beyond our solar system and return within a normal work period or lifetime. The Chameleon Density Model (CDM) is one such model that could provide new paths in propulsion toward this end. The CDM is based on Chameleon Cosmology a dark matter theory; introduced by Khrouy and Weltman in 2004. Chameleon as it is hidden within known physics, where the Chameleon field represents a scalar field within and about an object; even in the vacuum. The CDM relates to density changes in the Chameleon field, where the density changes are related to matter accelerations within and about an object. These density changes in turn change how an object couples to its environment. Whereby, thrust is achieved by causing a differential in the environmental coupling about an object. As a demonstration to show that the CDM fits within known propulsion physics, this paper uses the model to estimate the thrust from a solid rocket motor. Under the CDM, a solid rocket constitutes a two body system, i.e., the changing density of the rocket and the changing density in the nozzle arising from the accelerated mass. Whereby, the interactions between these systems cause a differential coupling to the local gravity environment of the earth. It is shown that the resulting differential in coupling produces a calculated value for the thrust near equivalent to the conventional thrust model used in Sutton and Ross, Rocket Propulsion Elements. Even though imbedded in the equations are the Universe energy scale factor, the reduced Planck mass and the Planck length, which relates the large Universe scale to the subatomic scale.
f(R) Gravity and Chameleon Theories
Brax, Philippe; Davis, Anne-Christine; Shaw, Douglas J
2008-01-01
We analyse f(R) modifications of Einstein's gravity as dark energy models in the light of their connection with chameleon theories. Formulated as scalar-tensor theories, the f(R) theories imply the existence of a strong coupling of the scalar field to matter. This would violate all experimental gravitational tests on deviations from Newton's law. Fortunately, the existence of a matter dependent mass and a thin shell effect allows one to alleviate these constraints. The thin shell condition also implies strong restrictions on the cosmological dynamics of the f(R) theories. As a consequence, we find that the equation of state of dark energy in the recent past is constrained to be extremely close to -1. We also examine the potential effects of f(R) theories in the context of the Eot-wash experiments. We show that the requirement of a thin shell for the test bodies is not enough to guarantee a null result on deviations from Newton's law. The constraints which we deduce also forbid any measurable deviation of the ...
Directory of Open Access Journals (Sweden)
Tarald Taraldsen
2007-12-01
Full Text Available We show that under certain circumstances, the Czech locative prepositions (LOC show up as directional prepositions (DIR and vice versa, (under different circumstances the Czech DIR PPs show up as LOC. We argue that such a chameleon life of the PPs is structurally dependent.
Tarald Taraldsen; Lucie Medová
2007-01-01
We show that under certain circumstances, the Czech locative prepositions (LOC) show up as directional prepositions (DIR) and vice versa, (under different circumstances) the Czech DIR PPs show up as LOC. We argue that such a chameleon life of the PPs is structurally dependent.
Towards a UV Completion for Chameleon Scalar Theories
Hinterbichler, Kurt; Nastase, Horatiu
2010-01-01
Chameleons are scalar fields that couple directly to ordinary matter with gravitational strength, but which nevertheless evade the stringent constraints on tests of gravity because of properties they acquire in the presence of high ambient matter density. Chameleon theories were originally constructed in a bottom-up, phenomenological fashion, with potentials and matter couplings designed to hide the scalar from experiments. In this paper, we attempt to embed the chameleon scenario within string compactifications, thus UV completing the scenario. We look for stabilized potentials that can realize a screening mechanism, and we find that the volume modulus rather generically works as a chameleon, and in fact the supersymmetric potential used by Kachru, Kallosh, Linde and Trivedi (KKLT) is an example of this type. We consider all constraints from tests of gravity, allowing us to put experimental constraints on the KKLT parameters.
Laboratory Tests of Chameleon Models
Brax, Philippe; Davis, Anne-Christine; Shaw, Douglas
2009-01-01
We present a cursory overview of chameleon models of dark energy and their laboratory tests with an emphasis on optical and Casimir experiments. Optical experiments measuring the ellipticity of an initially polarised laser beam are sensitive to the coupling of chameleons to photons. The next generation of Casimir experiments may be able to unravel the nature of the scalar force mediated by the chameleon between parallel plates.
Chameleon sequences in neurodegenerative diseases
Energy Technology Data Exchange (ETDEWEB)
Bahramali, Golnaz [Institute of Biochemistry and Biophysics, University of Tehran, Tehran (Iran, Islamic Republic of); Goliaei, Bahram, E-mail: goliaei@ut.ac.ir [Institute of Biochemistry and Biophysics, University of Tehran, Tehran (Iran, Islamic Republic of); Minuchehr, Zarrin, E-mail: minuchehr@nigeb.ac.ir [Department of Systems Biotechnology, National Institute of Genetic Engineering and Biotechnology, (NIGEB), Tehran (Iran, Islamic Republic of); Salari, Ali [Department of Systems Biotechnology, National Institute of Genetic Engineering and Biotechnology, (NIGEB), Tehran (Iran, Islamic Republic of)
2016-03-25
Chameleon sequences can adopt either alpha helix sheet or a coil conformation. Defining chameleon sequences in PDB (Protein Data Bank) may yield to an insight on defining peptides and proteins responsible in neurodegeneration. In this research, we benefitted from the large PDB and performed a sequence analysis on Chameleons, where we developed an algorithm to extract peptide segments with identical sequences, but different structures. In order to find new chameleon sequences, we extracted a set of 8315 non-redundant protein sequences from the PDB with an identity less than 25%. Our data was classified to “helix to strand (HE)”, “helix to coil (HC)” and “strand to coil (CE)” alterations. We also analyzed the occurrence of singlet and doublet amino acids and the solvent accessibility in the chameleon sequences; we then sorted out the proteins with the most number of chameleon sequences and named them Chameleon Flexible Proteins (CFPs) in our dataset. Our data revealed that Gly, Val, Ile, Tyr and Phe, are the major amino acids in Chameleons. We also found that there are proteins such as Insulin Degrading Enzyme IDE and GTP-binding nuclear protein Ran (RAN) with the most number of chameleons (640 and 405 respectively). These proteins have known roles in neurodegenerative diseases. Therefore it can be inferred that other CFP's can serve as key proteins in neurodegeneration, and a study on them can shed light on curing and preventing neurodegenerative diseases.
Search for chameleons with CAST
DEFF Research Database (Denmark)
Anastassopoulos, V.; Arik, M.; Aune, S.
2015-01-01
energy threshold used for axions from 1 keV to 400 eV CAST became sensitive to the converted solar chameleon spectrum which peaks around 600 eV. Even though we have not observed any excess above background, we can provide a 95% C.L. limit for the coupling strength of chameleons to photons of βΥ≤1011...
Constrained gauge fields from spontaneous Lorentz violation
DEFF Research Database (Denmark)
Chkareuli, J. L.; Froggatt, C. D.; Jejelava, J. G.
2008-01-01
Spontaneous Lorentz violation realized through a nonlinear vector field constraint of the type AµAµ=M2 (M is the proposed scale for Lorentz violation) is shown to generate massless vector Goldstone bosons, gauging the starting global internal symmetries in arbitrary relativistically invariant...... theories. The gauge invariance appears in essence as a necessary condition for these bosons not to be superfluously restricted in degrees of freedom, apart from the constraint due to which the true vacuum in a theory is chosen by the Lorentz violation. In the Abelian symmetry case the only possible theory...... proves to be QED with a massless vector Goldstone boson naturally associated with the photon, while the non-Abelian symmetry case results in a conventional Yang-Mills theory. These theories, both Abelian and non-Abelian, look essentially nonlinear and contain particular Lorentz (and CPT) violating...
Cosmological dynamics of extended chameleons
Tamanini, Nicola
2016-01-01
We investigate the cosmological dynamics of the recently proposed extended chameleon models at both background and linear perturbation levels. Dynamical systems techniques are employed to fully characterize the evolution of the universe at the largest distances, while structure formation is analysed at sub-horizon scales within the quasi-static approximation. The late time dynamical transition from dark matter to dark energy domination can be well described by almost all extended chameleon models considered, with no deviations from $\\Lambda$CDM results at both background and perturbation levels. The results obtained in this work confirm the cosmological viability of extended chameleons as alternative dark energy models.
Strongly Coupled Chameleons and the Neutronic Quantum Bouncer
Brax, Philippe; Pignol, Guillaume
2011-09-01
We consider the potential detection of chameleons using bouncing ultracold neutrons. We show that the presence of a chameleon field over a planar plate would alter the energy levels of ultracold neutrons in the terrestrial gravitational field. When chameleons are strongly coupled to nuclear matter, β≳108, we find that the shift in energy levels would be detectable with the forthcoming GRANIT experiment, where a sensitivity of the order of 1% of a peV is expected. We also find that an extremely large coupling β≳1011 would lead to new bound states at a distance of order 2μm, which is already ruled out by previous Grenoble experiments. The resulting bound, β≲1011, is already 3 orders of magnitude better than the upper bound, β≲1014, from precision tests of atomic spectra.
Strongly Coupled Chameleons and the Neutronic Quantum Bouncer
Brax, Philippe
2011-01-01
We consider the potential detection of chameleons using bouncing ultracold neutrons. We show that the presence of a chameleon field over a planar plate would alter the energy levels of ultra cold neutrons in the terrestrial gravitational field. When chameleons are strongly coupled to nuclear matter, $\\beta\\gtrsim 10^8$, we find that the shift in energy levels would be detectable with the forthcoming GRANIT experiment, where a sensitivity of order one percent of a peV is expected. We also find that an extremely large coupling $\\beta\\gtrsim 10^{11}$ would lead to new bound states at a distance of order 2 microns, which is already ruled out by previous Grenoble experiments. The resulting bound, $\\beta\\lesssim 10^{11}$, is already three orders of magnitude better than the upper bound, $\\beta\\lesssim 10^{14}$, from precision tests of atomic spectra.
A Proposed Experimental Search for Chameleons using Asymmetric Parallel Plates
Burrage, Clare; Stevenson, James A
2016-01-01
Light scalar fields coupled to matter are a common consequence of theories of dark energy and attempts to solve the cosmological constant problem. The chameleon screening mechanism is commonly invoked in order to suppress the fifth forces mediated by these scalars, suficiently to avoid current experimental constraints, without fine tuning. The force is suppressed dynamically by allowing the mass of the scalar to vary with the local density. Recently it has been shown that near future cold atoms experiments using atom-interferometry have the ability to access a large proportion of the chameleon parameter space. In this work we demonstrate how experiments utilising asymmetric parallel plates can push deeper into the remaining parameter space available to the chameleon.
Variational Principles for Constrained Electromagnetic Field and Papapetrou Equation
Muminov, A T
2007-01-01
In our previous article [4] an approach to derive Papapetrou equations for constrained electromagnetic field was demonstrated by use of field variational principles. The aim of current work is to present more universal technique of deduction of the equations which could be applied to another types of non-scalar fields. It is based on Noether theorem formulated in terms of Cartan' formalism of orthonormal frames. Under infinitesimal coordinate transformation the one leads to equation which includes volume force of spin-gravitational interaction. Papapetrou equation for vector of propagation of the wave is derived on base of the equation. Such manner of deduction allows to formulate more accurately the constraints and clarify equations for the potential and for spin.
Constraining Galactic Magnetic Field Models with Starlight Polarimetry
Pavel, Michael D
2011-01-01
This paper provides testable predictions about starlight polarizations to constrain the geometry of the Galactic magnetic field, in particular the nature of the poloidal component. Galactic dynamo simulations and Galactic dust distributions from the literature are combined with a Stokes radiative transfer model to predict the observed polarizations and position angles of near-infrared starlight, assuming the light is polarized by aligned anisotropic dust grains. S0 and A0 magnetic field models and the role of magnetic pitch angle are all examined. All-sky predictions are made, and particular directions are identified as providing diagnostic power for discriminating among the models. Cumulative distribution functions of the normalized degree of polarization and plots of polarization position angle vs. Galactic latitude are proposed as tools for testing models against observations.
The Distance Field Model and Distance Constrained MAP Adaptation Algorithm
Institute of Scientific and Technical Information of China (English)
YUPeng; WANGZuoying
2003-01-01
Spatial structure information, i.e., the rel-ative position information of phonetic states in the feature space, is long to be carefully researched yet. In this pa-per, a new model named “Distance Field” is proposed to describe the spatial structure information. Based on this model, a modified MAP adaptation algorithm named dis-tance constrained maximum a poateriori (DCMAP) is in-troduced. The distance field model gives large penalty when the spatial structure is destroyed. As a result the DCMAP reserves the spatial structure information in adaptation process. Experiments show the Distance Field Model improves the performance of MAP adapta-tion. Further results show DCMAP has strong cross-state estimation ability, which is used to train a well-performed speaker-dependent model by data from only part of pho-
How chameleons core dwarfs with cusps
Lombriser, Lucas
2014-01-01
The presence of a scalar field that couples nonminimally and universally to matter can enhance gravitational forces on cosmological scales while restoring general relativity in the Solar neighborhood. In the intermediate regime, kinematically inferred masses experience an additional radial dependence with respect to the underlying distribution of matter, which is caused by the increment of gravitational forces with increasing distance from the Milky Way center. The same effect can influence the internal kinematics of subhalos and cause cuspy matter distributions to appear core-like. Specializing to the chameleon model as a worked example, we demonstrate this effect by tracing the scalar field from the outskirts of the Milky Way halo to its interior, simultaneously fitting observed velocity dispersions of chemo-dynamically discriminated red giant populations in the Fornax and Sculptor dwarf spheroidals. Whereas in standard gravity these observations suggest that the matter distribution of the dwarfs is cored, ...
Lingual structural pattern of juvenile Chameleon, Chameleo chameleon
Directory of Open Access Journals (Sweden)
Ahmed A. El Mansi
2017-06-01
Full Text Available It is belong to the order Squamata, family, Chamaeleonidae. They have characteristic features of tongue protrusion during capturing prey attracts many research works and assay its velocity during protrusion. Yet little studies touched the anatomical and histological feature of the juvenile tongue and especially the middle tongue region involved in the tongue elongation, the present study aimed to focus on the histological structure of the mid-tongue and clarify its role in projection of the tongue as well as the glandular structure, keratinization of lingual epithelium and proliferation capacity of the fore-tongue region in relation with their feeding habits during the juvenile age. Juvenile Chameleo chameleon are collected from Abu Rawash, north of Giza Governorate, Egypt during summer 2015. Three juvenile developmental stages are used in the present study and categorized according to the gross morphological criteria of head, abdomen and limb lengths. The tongue and hyoid apparatus were removed and photographed. Histological, immunohistochemistry of cytokeratin and stem cell factor and scanning electronic microscopic investigations were carried out on the fore-tongue region, meanwhile only histological studies were done for the median tongue region. Morphometric assessments of number and length of lingual papillae and grades of cytokeratin and stem cell expression were done. Histologically, the dorsal lingual mucosa of the fore-tongue possessed different pattern of lingual papillae including finger-like, club, cubical, biforked and multi-branched papillae. The finger-like papillae are more abundant compared to the other types. The lamina propria of anterior median tongue pad are more glandular and exhibited abundant distribution of PAS-positive tubular glands and moderate alcian blue staining affinity of both alveolar and branched alveolar glands. There is no detected keratinization of the lingual epithelium. Stem cell factor appeared denser on
Constraining non-minimally coupled tachyon fields by Noether symmetry
de Souza, Rudinei C
2008-01-01
A model for a spatially flat homogeneous and isotropic Universe whose gravitational sources are a pressureless matter field and a tachyon field non-minimally coupled to the gravitational field is analyzed. Noether symmetry is used to find the expressions for the potential density and for the coupling function, and it is shown that both must be exponential functions of the tachyon field. Two cosmological solutions are investigated: (i) for the early Universe whose only source of the gravitational field is a non-minimally coupled tachyon field which behaves as an inflaton and leads to an exponential accelerated expansion and (ii) for the late Universe whose gravitational sources are a pressureless matter field and a non-minimally coupled tachyon field which plays the role of dark energy and is the responsible of the decelerated-accelerated transition period.
Entropy Bounds for Constrained Two-Dimensional Fields
DEFF Research Database (Denmark)
Forchhammer, Søren Otto; Justesen, Jørn
1999-01-01
The maximum entropy and thereby the capacity of 2-D fields given by certain constraints on configurations are considered. Upper and lower bounds are derived.......The maximum entropy and thereby the capacity of 2-D fields given by certain constraints on configurations are considered. Upper and lower bounds are derived....
Can CMB data constrain the inflationary field range?
Garcia-Bellido, Juan; Scalisi, Marco; Zavala, Ivonne
2014-01-01
We study to what extent the spectral index $n_s$ and the tensor-to-scalar ratio $r$ determine the field excursion $\\Delta\\phi$ during inflation. We analyse the possible degeneracy of $\\Delta \\phi$ by comparing three broad classes of inflationary models, with different dependence on the number of e-foldings $N$, to benchmark models of chaotic inflation with monomial potentials. The classes discussed cover a large set of inflationary single field models. We find that the field range is not uniquely determined for any value of $(n_s, r)$; one can have the same predictions as chaotic inflation and a very different $\\Delta \\phi$. Intriguingly, we find that the field range cannot exceed an upper bound that appears in different classes of models. Finally, $\\Delta \\phi$ can even become sub-Planckian, but this requires to go beyond the single-field slow-roll paradigm.
The peculiar velocity field: constraining the tilt of the Universe
Ma, Yin-Zhe; Feldman, Hume A
2010-01-01
A large bulk flow, which is in tension with the Lambda Cold Dark Matter cosmological model, has been observed \\cite{Watkins08,Feldman09}. In this letter, we provide a physical explanation for this very large bulk flow, based on the assumption that the cosmic microwave background (CMB) rest frame does not coincide with the matter rest frame, resulting in a "tilted Universe". We propose a model that takes into account the relative velocity of CMB frame with respect to to the matter rest frame (hereafter tilted velocity), and use Type Ia Supernovae (SN), ENEAR, SFI++, SMAC, and COMPOSITE galaxy catalogues to constrain this tilted velocity. We find that: (1) the magnitude of the tilted velocity $u$ is around 400 km/s, and its direction is close to what is found by \\cite{Watkins08}; for SN, SMAC and COMPOSITE catalogues, $u=0$ is excluded at the two to three sigma level; (2) the constraints on the magnitude of the tilted velocity can result in the constraints on the duration of inflation, due to the fact that infl...
Can CMB data constrain the inflationary field range?
Garcia-Bellido, Juan; Roest, Diederik; Scalisi, Marco; Zavala, Ivonne
2014-01-01
We study to what extent the spectral index ns and the tensor-to-scalar ratio r determine the field excursion Delta phi during inflation. We analyse the possible degeneracy of Delta phi by comparing three broad classes of inflationary models, with different dependence on the number of e-foldings N, t
Constrained field theories on spherically symmetric spacetimes with horizons
Fernandes, Karan; Lahiri, Amitabha; Ghosh, Suman
2017-02-01
We apply the Dirac-Bergmann algorithm for the analysis of constraints to gauge theories defined on spherically symmetric black hole backgrounds. We find that the constraints for a given theory are modified on such spacetimes through the presence of additional contributions from the horizon. As a concrete example, we consider the Maxwell field on a black hole background, and determine the role of the horizon contributions on the dynamics of the theory.
Constrained field theories on spherically symmetric spacetimes with horizons
Fernandes, Karan; Lahiri, Amitabha
2016-01-01
We apply the Dirac-Bergmann algorithm for the analysis of constraints to gauge theories defined on spherically symmetric black hole backgrounds. As a concrete example, we consider the Maxwell field on a black hole background, and determine the role of the horizon contributions on the dynamics of the theory. We find that the constraints are modified on such spacetimes through the presence of additional contributions from the horizon.
The Chameleon Effect in the Jordan Frame of the Brans--Dicke Theory
Quiros, Israel; Gonzalez, Tame; Horta-Rangel, F Antonio
2015-01-01
In this paper we investigate the chameleon effect in the different conformal frames of the Brans--Dicke theory. Given that, in the standard literature on the subject, the chameleon is described in the Einstein frame almost exclusively, here we pay special attention to the description of this effect in the Jordan and in the string frames. It is shown that, in general, terrestrial and solar system bounds on the mass of the BD scalar field, and bounds of cosmological origin, are difficult to reconcile at once through a single chameleon potential. We point out that, in a cosmological context, provided that the effective chameleon potential has a minimum within a region of constant density of matter, the Brans--Dicke theory transmutes into general relativity with a cosmological constant, in that region. This result, however, can be only locally valid. In cosmological settings de Sitter--general relativity is a global attractor of the Brans--Dicke theory only for the quadratic potential $V(\\phi)=M^2\\phi^2$, or for ...
A new large field inflation constrained by Planck 2015
Ferricha-Alami, M.; Mounzi, Z.; Chakir, H.; Bennai, M.
2016-05-01
In this work we propose a new large field inflation model, parametrized by a parameter β sharing the same features with T-Model. We apply the slow-roll approximation to investigate the inflationary parameters, and we found that they depend on some value of β and the e-folds number Ne. In this context, we have computed and discussed the perturbation of the scalar curvature and determined the energy scale V0, which we found to be in the GUT regime. We also showed that, in our scenario, the various inflationary spectrum perturbation parameters, the spectral index ns, the ratio of tensor to scalar perturbations r and the running d ns/d ln k, perfectly agree with the recent experimental observations in the event β > 0.5 and Ne˜ 45-60. As a result we have reproduced successfully the main part, ns-r, consistent with Planck data.
The human chameleon: Hybrid Jews in cinema
A. Vudka
2016-01-01
This research explores the seditious potential of hybrid Jewish figures in cinema, based on certain thinkers of post WWII French philosophy, feminist and postcolonial theories, and traditional Jewish texts, which in different ways point to a reevaluation of the "chameleon Jew" in positive terms. Whi
The human chameleon: Hybrid Jews in cinema
Vudka, A.
2016-01-01
This research explores the seditious potential of hybrid Jewish figures in cinema, based on certain thinkers of post WWII French philosophy, feminist and postcolonial theories, and traditional Jewish texts, which in different ways point to a reevaluation of the "chameleon Jew" in positive terms. Whi
Speed, Acceleration, Chameleons and Cherry Pit Projectiles
Planinsic, Gorazd; Likar, Andrej
2012-01-01
The paper describes the mechanics of cherry pit projectiles and ends with showing the similarity between cherry pit launching and chameleon tongue projecting mechanisms. The whole story is written as an investigation, following steps that resemble those typically taken by scientists and can therefore serve as an illustration of scientific…
Odontogenesis in the Veiled Chameleon (Chamaeleo calyptratus).
Buchtová, Marcela; Zahradníček, Oldřich; Balková, Simona; Tucker, Abigail S
2013-02-01
Replacement teeth in reptiles and mammals develop from a successional dental lamina. In monophyodont (single generation) species such as the mouse, no successional lamina develops. We have selected a reptilian monophyodont species - the Veiled Chameleon (Chamaeleo calyptratus) - to investigate whether this is a common characteristic of species that do not have replacement teeth. Furthermore, we focus on the sequence of tooth initiation along the jaw, and tooth attachment to the bones. Embryos of the Veiled Chameleon were collected during the first 6 months of incubation (from the 5th to 24th week) at 7-day intervals. After five weeks of incubation, an epithelial thickening was present as a shallow protrusion into the mesenchyme. A week later, the epithelium elongated more deeply into the mesenchyme to form the dental lamina. The formation of all tooth germs along the jaw was initiated from the tip of the dental lamina. Development of a successional dental lamina was initiated during the pre-hatching period but this structure became markedly reduced during juvenile stages. MicroCT analysis showed the presence of a heterodont dentition in young chameleons with multicuspid teeth in the caudal jaw area and simpler monocuspid teeth rostrally. Unlike the pleurodont teeth of most reptilian species, chameleon teeth are acrodontly ankylosed to the bones of the jaw. Odontoblasts produced a layer of predentine that connected the dentine to the supporting bone, with both tooth and bone protruding out of the oral cavity and acting as a functional unit. Chameleons may provide new and useful information to study the molecular interaction at the tooth-bone interface in physiological as well as pathological conditions. Copyright © 2012 Elsevier Ltd. All rights reserved.
Dimitrov, Nikolay Krasimirov; Lazarov, Boyan Stefanov
2015-01-01
We demonstrate a method for incorporating wind measurements from multiple-point scanning lidars into the turbulence fields serving as input to wind turbine load simulations. The measurement values are included in the analysis by applying constraints to randomly generated turbulence fields. A numerical study shows the application of the constrained turbulence method to load simulations on a 10MW wind turbine model, using two example lidar patterns – a 5-point pattern forming a square with a ce...
Evidence for an elastic projection mechanism in the chameleon tongue
Groot, de J.H.; Leeuwen, van J.L.
2004-01-01
To capture prey, chameleons ballistically project their tongues as far as 1.5 body lengths with accelerations of up to 500 m s-2. At the core of a chameleon's tongue is a cylindrical tongue skeleton surrounded by the accelerator muscle. Previously, the cylindrical accelerator muscle was assumed to p
Chameleon Hashes Without Key Exposure Based on Factoring
Institute of Scientific and Technical Information of China (English)
Wei Gao; Xue-Li Wang; Dong-Qing Xie
2007-01-01
Chameleon hash is the main primitive to construct a chameleon signature scheme which provides non-repudiation and non-transferability simultaneously.However, the initial chameleon hash schemes suffer from the key exposure problem: non-transferability is based on an unsound assumption that the designated receiver is willing to abuse his private key regardless of its exposure.Recently, several key-exposure-free chameleon hashes have been constructed based on RSA assumption and SDH (strong Diffie-Hellman) assumption.In this paper, we propose a factoring-based chameleon hash scheme which is proven to enjoy all advantages of the previous schemes.In order to support it, we propose a variant Rabin signature scheme which is proven secure against a new type of attack in the random oracle model.
Description of $^{178}$Hf$^{m2}$ in the constrained relativistic mean field theory
Wei, Zhang; Shuang-Quan, Zhang
2009-01-01
The properties of the ground state of $^{178}$Hf and the isomeric state $^{178}$Hf$^{m2}$ are studied within the adiabatic and diabatic constrained relativistic mean field (RMF) approaches. The RMF calculations reproduce well the binding energy and the deformation for the ground state of $^{178}$Hf. Using the ground state single-particle eigenvalues obtained in the present calculation, the lowest excitation configuration with $K^\\pi=16^+$ is found to be $\
Hidden Symmetries in Second Class Constrained Systems Are New Fields Necessary?
Vytheeswaran, A S
2000-01-01
For many systems with second class constraints, the question posed in the title is answered in the negative. We prove this for a range of systems with two second class constraints. After looking at two examples, we consider a fairly general proof. It is shown that, to unravel gauge invariances in second class constrained systems, it is sufficient to work in the original phase space itself. Extension of the phase space by introducing new variables of fields is not required.
An Upper Bound on the Entropy of Constrained 2d Fields
DEFF Research Database (Denmark)
Forchhammer, Søren; Justesen, Jørn
1998-01-01
An upper bound on the entropy of constrained 2D fields is presented. The constraints have to be symmetric in (at least) one of the two directions. The bound generalizes (in a weaker form) the bound of Calkin and Wilf (see SIAM Journal of Discrete Mathematics, vol.11, p.54-60, 1998) which is valid...... only for processes with symmetric transfer matrices. Results are given for constraints specified by run-length limits and minimum distance between pixels of the same color...
Directory of Open Access Journals (Sweden)
Avichai Lustig
Full Text Available The common chameleon, Chamaeleo chameleon, is an arboreal lizard with highly independent, large-amplitude eye movements. In response to a moving threat, a chameleon on a perch responds with distinct avoidance movements that are expressed in its continuous positioning on the side of the perch distal to the threat. We analyzed body-exposure patterns during threat avoidance for evidence of lateralization, that is, asymmetry at the functional/behavioral levels. Chameleons were exposed to a threat approaching horizontally from the left or right, as they held onto a vertical pole that was either wider or narrower than the width of their head, providing, respectively, monocular or binocular viewing of the threat. We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach. Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions. This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.
Raxworthy, Christopher J.
2016-01-01
The Malagasy giant chameleons (Furcifer oustaleti and Furcifer verrucosus) are sister species that are both broadly distributed in Madagascar, and also endemic to the island. These species are also morphologically similar and, because of this, have been frequently misidentified in the field. Previous studies have suggested that cryptic species are nested within this chameleon group, and two subspecies have been described in F. verrucosus. In this study, we utilized a phylogeographic approach to assess genetic diversification within these chameleons. This was accomplished by (1) identifying clades within each species supported by both mitochondrial and nuclear DNA, (2) assessing divergence times between clades, and (3) testing for niche divergence or conservatism. We found that both F. oustaleti and F. verrucosus could be readily identified based on genetic data, and within each species, there are two well-supported clades. However, divergence times are not contemporary and spatial patterns are not congruent. Diversification within F. verrucosus occurred during the Plio-Pleistocene, and there is evidence for niche divergence between a southwestern and southeastern clade, in a region of Madagascar that shows no obvious landscape barriers to dispersal. Diversification in F. oustaleti occurred earlier in the Pliocene or Miocene, and niche conservatism is supported with two genetically distinct clades separated at the Sofia River in northwestern Madagascar. Divergence within F. verrucosus is most consistent with patterns expected from ecologically mediated speciation, whereas divergence in F. oustaleti most strongly matches the patterns expected from the riverine barrier hypothesis. PMID:27257819
Andriopoulou, M.; Roussos, E.; Krupp, N.; Paranicas, C.; Thomsen, M.; Krimigis, S.; Dougherty, M. K.; Glassmeier, K.-H.
2013-09-01
The position of energetic electron absorption signatures caused by orbiting moons can be a powerful tool for detecting convective electric fields that are present in the magnetospheres of outer planets. In this work we used energetic electron data from the MIMI-LEMMS detector onboard Cassini and studied the so called microsignature events of several Saturnian moons, covering a radial distance between 2.5 and 9.5 Rs. We considered numerical as well as analytical methods and used these events to constrain the properties of the recently discovered convective electric field in Saturn's inner magnetosphere, that was found to have an average strength of 0.2 mV/m and an orientation in the noon-midnight direction. The study of the electric field has been performed on an average scale (using all events) but also on a single-case event scale and its possible sensitivity with respect to radial distance and time has been examined and confirmed. It is also interesting that although the average electric field orientation is found to be at approximately 01-02 hours in local time, regardless of the examined radial distances, we report high variability of the electric field pointing on short spatial and temporal scales of single microsignature events. Additionally, we discuss the possible connection to other convective electric field patterns that might be present in the inner part of the Saturnian magnetosphere. A constrain of the electric field properties from such a work can lead to insights towards revealing the source of such a convection pattern, that has been observed for the first time in the inner magnetosphere of Saturn.
Shell evolution at N=20 in the constrained relativistic mean field approach
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The shell evolution at N = 20, a disappearing neutron magic number observed experimentally in very neutron-rich nuclides, is investigated in the constrained relativistic mean field (RMF) theory. The trend of the shell closure observed experimentally towards the neutron drip-line can be reproduced. The predicted two-neutron separation energies, neutron shell gap energies and deformation parameters of ground states are shown as well. These results are compared with the recent Hartree-Fock-Bogliubov (HFB-14) model and the available experimental data. The perspective towards a better understanding of the shell evolution is discussed.
Fission Barrier for 240Pu in the Quadrupole Constrained Relativistic Mean Field Approach
Institute of Scientific and Technical Information of China (English)
L(U) Hong-Feng; GENG Li-Sheng; MENG Jie
2006-01-01
@@ The fission barrier for 240Pu is investigated beyond the second saddle point in the potential energy surface by the constrained relativistic mean field method with the newly proposed parameter set PK1. The microscopic correction for the centre-of-mass motion is essential to provide the correct potential energy surface. The shell effects that stabilize the nuclei against the fission is also investigated by the Strutinsky method. The shapes for the ground state, fission isomer and saddle-points, etc, are studied in detail.
Description of 178 Hfm2 in the Constrained Relativistic Mean Field Theory
Institute of Scientific and Technical Information of China (English)
ZHANG Wei; PENG Jing; ZHANG Shuang-Quan
2009-01-01
Properties of the ground state of 178 Hf and the isomeric state 178Hfn2 are studied within the adiabatic and diabatic constrained relativistic mean field (RMF) approaches. The RMF calculations reproduce well the binding energy and the deformation for the ground state of 178Hf. Using the ground state single-particle eigenvalues obtained in the present calculation, the lowest excitation configuration with Kπ = 16+ is found to be v(7/2- [514])-1 (9/2+ [624])1 π(7/2+ [404])-1 (9/2-[514])1. Its excitation energy calculated by the RMF theory with time-odd fields taken into account is equal to 2.801 MeV, i.e., close to the 178 Hfm2 experimental excitation energy 2.446 MeV. The self-consistent procedure accounting for the time-odd component of the meson fields is the most important aspect of the present calculation.
Energy Technology Data Exchange (ETDEWEB)
Xu Longdao; Gao Yuliang
1985-09-01
Two variational parameters are included in the most probable constrained effective wave function with the accurate Hamiltonian remained. The third critical field which coincides with the result in paper (1) has been easily obtained through the variational principle.
Constraining the top-Higgs sector of the Standard Model Effective Field Theory
Cirigliano, V; de Vries, J; Mereghetti, E
2016-01-01
Working in the framework of the Standard Model Effective Field Theory, we study chirality-flipping couplings of the top quark to Higgs and gauge bosons. We discuss in detail the renormalization group evolution to lower energies and investigate direct and indirect contributions to high- and low-energy CP-conserving and CP-violating observables. Our analysis includes constraints from collider observables, precision electroweak tests, flavor physics, and electric dipole moments. We find that indirect probes are competitive or dominant for both CP-even and CP-odd observables, even after accounting for uncertainties associated with hadronic and nuclear matrix elements, illustrating the importance of including operator mixing in constraining the Standard Model Effective Field Theory. We also study scenarios where multiple anomalous top couplings are generated at the high scale, showing that while the bounds on individual couplings relax, strong correlations among couplings survive. Finally, we find that enforcing m...
A Modified FCM Classifier Constrained by Conditional Random Field Model for Remote Sensing Imagery
Directory of Open Access Journals (Sweden)
WANG Shaoyu
2016-12-01
Full Text Available Remote sensing imagery has abundant spatial correlation information, but traditional pixel-based clustering algorithms don't take the spatial information into account, therefore the results are often not good. To this issue, a modified FCM classifier constrained by conditional random field model is proposed. Adjacent pixels' priori classified information will have a constraint on the classification of the center pixel, thus extracting spatial correlation information. Spectral information and spatial correlation information are considered at the same time when clustering based on second order conditional random field. What's more, the global optimal inference of pixel's classified posterior probability can be get using loopy belief propagation. The experiment shows that the proposed algorithm can effectively maintain the shape feature of the object, and the classification accuracy is higher than traditional algorithms.
Phase-field simulation of micropores constrained by the dendritic network during solidification
Energy Technology Data Exchange (ETDEWEB)
Meidani, H., E-mail: hossein.meidani@epfl.ch [Computational Materials Laboratory, Institute of Materials, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Jacot, A. [Computational Materials Laboratory, Institute of Materials, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Calcom ESI SA, Parc Scientifique, PSE-A, 1015 Lausanne (Switzerland)
2011-05-15
Highlights: > Direct description of the complex morphology of micropores in using phase-field. > Presence of solid substantially influences the pressure and volume of the pores. > Hydrogen content is an influencing factor that was not considered previously. > Pore curvature depends on the statistical distribution of liquid channel widths. - Abstract: A phase-field model has been developed to describe the morphology of pores constrained by a dendritic solid network, and are forced to adopt complex non-spherical shapes. The distribution of the solid, liquid and gas phases was calculated with a multiphase-field approach which accounts for the pressure difference between the liquid and the gas. The model considers the partitioning of the dissolved gas at interfaces, gas diffusion and capillary forces at the solid/liquid, liquid/gas and gas/solid interfaces. The model was used to study the influence of the dendrite arm spacing (DAS) and the solid fraction on the state of a pore. The calculations show that a pore constrained to grow in a narrow liquid channel exhibits a substantially higher mean curvature, a larger pressure and a smaller volume than an unconstrained pore. Comparisons with simple geometrical models indicate that analytical approaches show a good trend but tend to underestimate the pore curvature, in particular at high solid fractions, where pores have to penetrate the thin liquid channels. For pores spanning over distances larger than the average DAS, the simulations showed that the radius of curvature can vary between two limits, which are given by the size of the narrowest section that the pore needs to pass in order to expand and by the largest sphere that can be fitted in the interdendritic liquid. The pore curvature is therefore a complex non-monotonic function of the DAS, the solid fraction, the hydrogen content and statistical variations of the liquid channel width.
Halo effective field theory constrains the solar 7Be + p → 8B + γ rate
Directory of Open Access Journals (Sweden)
Xilin Zhang
2015-12-01
Full Text Available We report an improved low-energy extrapolation of the cross section for the process Be7(p,γB8, which determines the 8B neutrino flux from the Sun. Our extrapolant is derived from Halo Effective Field Theory (EFT at next-to-leading order. We apply Bayesian methods to determine the EFT parameters and the low-energy S-factor, using measured cross sections and scattering lengths as inputs. Asymptotic normalization coefficients of 8B are tightly constrained by existing radiative capture data, and contributions to the cross section beyond external direct capture are detected in the data at E<0.5 MeV. Most importantly, the S-factor at zero energy is constrained to be S(0=21.3±0.7 eVb, which is an uncertainty smaller by a factor of two than previously recommended. That recommendation was based on the full range for S(0 obtained among a discrete set of models judged to be reasonable. In contrast, Halo EFT subsumes all models into a controlled low-energy approximant, where they are characterized by nine parameters at next-to-leading order. These are fit to data, and marginalized over via Monte Carlo integration to produce the improved prediction for S(E.
Halo effective field theory constrains the solar Beryllium-7 + proton -> Boron-8 + photon rate
Zhang, Xilin; Phillips, D R
2015-01-01
We report an improved low-energy extrapolation of the cross section for the process Beryllium-7+proton -> Boron-8+photon, which determines the Boron-8 neutrino flux from the Sun. Our extrapolant is derived from Halo Effective Field Theory (EFT) at next-to-leading order. We apply Bayesian methods to determine the EFT parameters and the low-energy S-factor, using measured cross sections and scattering lengths as inputs. Asymptotic normalization coefficients of Boron-8 are tightly constrained by existing radiative capture data, and contributions to the cross section beyond external direct capture are detected in the data at E < 0.5 MeV. Most importantly, the S-factor at zero energy is constrained to be S(0)= 21.3 + - 0.7 eV b, which is an uncertainty smaller by a factor of two than previously recommended. That recommendation was based on the full range for S(0) obtained among a discrete set of models judged to be reasonable. In contrast, Halo EFT subsumes all models into a controlled low-energy approximant, w...
Mimics and chameleons in motor neurone disease.
Turner, Martin R; Talbot, Kevin
2013-06-01
The progression of motor neurone disease (MND) is currently irreversible, and the grave implications of diagnosis naturally fuels concern among neurologists over missing a potential mimic disorder. There is no diagnostic test for MND but in reality there are few plausible mimics in routine clinical practice. In the presence of a progressive pure motor disorder, signs such as florid fasciculations, bilateral tongue wasting, the 'split hand', head drop, emotionality, and cognitive or behavioural impairment carry high positive predictive value. MND is clinically heterogeneous, however, with some important chameleon-like presentations and considerable variation in clinical course. Lack of confidence about the scope of such variation, or an approach to diagnosis emphasising investigations over clinical common sense, has the potential to exacerbate diagnostic delay in MND and impede timely planning of the care which is essential to maximising quality of life.
Bahramali, Golnaz; Goliaei, Bahram; Minuchehr, Zarrin; Marashi, Sayed-Amir
2017-02-01
Chameleon proteins are proteins which include sequences that can adopt α-helix-β-strand (HE-chameleon) or α-helix-coil (HC-chameleon) or β-strand-coil (CE-chameleon) structures to operate their crucial biological functions. In this study, using a network-based approach, we examined the chameleon proteins to give a better knowledge on these proteins. We focused on proteins with identical chameleon sequences with more than or equal to seven residues long in different PDB entries, which adopt HE-chameleon, HC-chameleon, and CE-chameleon structures in the same protein. One hundred and ninety-one human chameleon proteins were identified via our in-house program. Then, protein-protein interaction (PPI) networks, Gene ontology (GO) enrichment, disease network, and pathway enrichment analyses were performed for our derived data set. We discovered that there are chameleon sequences which reside in protein-protein interaction regions between two proteins critical for their dual function. Analysis of the PPI networks for chameleon proteins introduced five hub proteins, namely TP53, EGFR, HSP90AA1, PPARA, and HIF1A, which were presented in four PPI clusters. The outcomes demonstrate that the chameleon regions are in critical domains of these proteins and are important in the development and treatment of human cancers. The present report is the first network-based functional study of chameleon proteins using computational approaches and might provide a new perspective for understanding the mechanisms of diseases helping us in developing new medical therapies along with discovering new proteins with chameleon properties which are highly important in cancer.
Constraining the dipolar magnetic field of M82 X-2 by the accretion model
Chen, Wen-Cong
2016-01-01
Recently, ultraluminous X-ray source (ULX) M82 X-2 has been identified to be an accreting neutron star, which has a $P=1.37$ s spin period, and is spinning up at a rate $\\dot{P}=-2.0\\times 10^{-10}~\\rm s\\,s^{-1}$. Interestingly, its isotropic X-ray luminosity $L_{\\rm iso}=1.8\\times 10^{40}~\\rm erg\\,s^{-1}$ during outbursts is 100 times the Eddington limit for a $1.4~\\rm M_{\\odot}$ neutron star. In this Letter, based on the standard accretion model we attempt to constrain the dipolar magnetic field of the pulsar in ULX M82 X-2. Our calculations indicate that the accretion rate at the magnetospheric radius must be super-Eddington during outbursts. To support such a super-Eddington accretion, a relatively high multipole field ($\\ga 10^{13}$ G) near the surface of the accretor is invoked to produce an accreting gas column. However, our constraint shows that the surface dipolar magnetic field of the pulsar should be in the range of $1.0-3.5\\times 10^{12}$ G. Therefore, our model supports that the neutron star in U...
Constraining supernova progenitors: an integral field spectroscopic survey of the explosion sites
Kuncarayakti, H; Anderson, J P; Arimoto, N; Doi, M; Galbany, L; Hamuy, M; Hashiba, Y; Kruehler, T; Maeda, K; Morokuma, T; Usuda, T
2014-01-01
We describe a survey of nearby core-collapse supernova (SN) explosion sites using integral field spectroscopy (IFS) technique, which is an extension of the work described in Kuncarayakti et al. (2013, AJ, 146, 30/31) . The project aims to constrain the SN progenitor properties based on the study of the SN immediate environment. The stellar populations present at the SN explosion sites are studied by means of integral field spectroscopy, which enables the acquisition of both spatial and spectral information of the object simultaneously. The spectrum of the SN parent stellar population gives the estimate of its age and metallicity. With this information, the initial mass and metallicity of the once coeval SN progenitor star are derived. While the survey is mostly done in optical, additionally the utilization of near-infrared integral field spectroscopy assisted with adaptive optics (AO) enables us to examine the explosion sites in high spatial details, down to a few parsecs. This work is being carried out using...
Constraining regular and turbulent magnetic field strengths in M51 via Faraday depolarization
Shneider, Carl; Fletcher, Andrew; Shukurov, Anvar
2014-01-01
We employ an analytical model that incorporates both wavelength-dependent and wavelength-independent depolarization to describe radio polarimetric observations of polarization at $\\lambda \\lambda \\lambda \\, 3.5, 6.2, 20.5$ cm in M51 (NGC 5194). The aim is to constrain both the regular and turbulent magnetic field strengths in the disk and halo, modeled as a two- or three-layer magneto-ionic medium, via differential Faraday rotation and internal Faraday dispersion, along with wavelength-independent depolarization arising from turbulent magnetic fields. A reduced chi-squared analysis is used for the statistical comparison of predicted to observed polarization maps to determine the best-fit magnetic field configuration at each of four radial rings spanning $2.4 - 7.2$ kpc in $1.2$ kpc increments. We find that a two-layer modeling approach provides a better fit to the observations than a three-layer model, where the near and far sides of the halo are taken to be identical, although the resulting best-fit magnetic...
Kishore, P.; Ramesh, R.; Hariharan, K.; Kathiravan, C.; Gopalswamy, N.
2016-11-01
We report on low-frequency radio (85-35 MHz) spectral observations of four different type II radio bursts, which exhibited fundamental-harmonic emission and split-band structure. Each of the bursts was found to be closely associated with a whitelight coronal mass ejection (CME) close to the Sun. We estimated the coronal magnetic field strength from the split-band characteristics of the bursts, by assuming a model for the coronal electron density distribution. The choice of the model was constrained, based on the following criteria: (1) when the radio burst is observed simultaneously in the upper and lower bands of the fundamental component, the location of the plasma level corresponding to the frequency of the burst in the lower band should be consistent with the deprojected location of the leading edge (LE) of the associated CME; (2) the drift speed of the type II bursts derived from such a model should agree closely with the deprojected speed of the LE of the corresponding CMEs. With the above conditions, we find that: (1) the estimated field strengths are unique to each type II burst, and (2) the radial variation of the field strength in the different events indicate a pattern. It is steepest for the case where the heliocentric distance range over which the associated burst is observed is closest to the Sun, and vice versa.
Constraining Eruptive Conditions From Lava Flow Morphometry: A Case Study With Field Evidence
Bowles, Z. R.; Clarke, A.; Greeley, R.
2007-12-01
Volcanism is widely recognized as one of the primary factors affecting the surfaces of solid planets and satellites throughout the solar system. Basaltic lava is thought to be the most common composition based on observed features typical of basaltic eruptions found on Earth. Lava flows are one of the most easily recognizable landforms on planetary surfaces and their features may provide information about eruption dynamics, lava rheology, and potential hazards. More recently, researchers have taken a multi-faceted approach to combine remote sensing, field observations and quantitative modeling to constrain volcanic activity on Earth and other planets. Here we test a number of published models, including empirically derived relationships from Mt. Etna and Kilauea, models derived from laboratory experiments, and theoretical models previously applied to remote sensing of planetary surfaces, against well-documented eruptions from the literature and field observations. We find that the Graetz (Hulme and Felder, 1977, Phil.Trans., 285, 227 - 234) method for estimating effusion rates compares favorably with published eruption data, while, on the other hand, inverting lava flow length prediction models to estimate effusion rates leads to several orders of magnitude in error. The Graetz method also better constrains eruption duration. Simple radial spreading laws predict Hawaiian lava flow lengths quite well, as do using the thickness of the lava flow front and chilled crust. There was no observed difference between results from models thought to be exclusive to aa or pahoehoe flow fields. Interpreting historic conditions should therefore follow simple relationships to observable morphologies no matter the composition or surface texture. We have applied the most robust models to understand the eruptive conditions and lava rheology of the Batamote Mountains near Ajo, AZ, an eroded shield volcano in southern Arizona. We find effusion rates on the order of 100 - 200 cubic
A Proposal for an ALPs-Chameleon Experiments Station
Boyce, James R; Baker, Oliver Keith; Shinn, Michelle
2014-01-01
It is generally accepted that certain astronomical and cosmological observations can be explained by invoking the concepts of Dark Matter and Dark Energy (DM/DE). Applying straightforward extensions of the Standard Model to DM/DE, results in scalar fi?elds and predictions of particles generation via photo-magnetic coupling . Under the right conditions, these particles should be observable in earth-bound laboratory settings. Although many attempts have been made to observe these particles, none have succeeded. Heretofore, most searches have focused on detecting multi-GeV Dark Matter WIMPS. Recently, however, searches have been conducted in the lighter dark matter, sub-eV, WISP mass range. By comparison, little has been done to search for dark energy particles. The ALPs-Chameleon Experiments Stations (ACES) program, described herein, proposes a compact station that would search for both dark sector particles. Finally, it is noted that both "species" of particles - dark energy and dark matter - could be generate...
Constraining the top-Higgs sector of the standard model effective field theory
Cirigliano, V.; Dekens, W.; de Vries, J.; Mereghetti, E.
2016-08-01
Working in the framework of the Standard Model effective field theory, we study chirality-flipping couplings of the top quark to Higgs and gauge bosons. We discuss in detail the renormalization-group evolution to lower energies and investigate direct and indirect contributions to high- and low-energy C P -conserving and C P -violating observables. Our analysis includes constraints from collider observables, precision electroweak tests, flavor physics, and electric dipole moments. We find that indirect probes are competitive or dominant for both C P -even and C P -odd observables, even after accounting for uncertainties associated with hadronic and nuclear matrix elements, illustrating the importance of including operator mixing in constraining the Standard Model effective field theory. We also study scenarios where multiple anomalous top couplings are generated at the high scale, showing that while the bounds on individual couplings relax, strong correlations among couplings survive. Finally, we find that enforcing minimal flavor violation does not significantly affect the bounds on the top couplings.
Cosmic Web and Environmental Dependence of Screening: Vainshtein vs. Chameleon
Falck, Bridget; Zhao, Gong-bo
2015-01-01
Theories which modify general relativity to explain the accelerated expansion of the Universe often use screening mechanisms to satisfy constraints on Solar System scales. We investigate the effects of the cosmic web and the local environmental density of dark matter halos on the screening properties of the Vainshtein and chameleon screening mechanisms. We compare the cosmic web morphology of dark matter particles, mass functions of dark matter halos, mass and radial dependence of screening, velocity dispersions and peculiar velocities, and environmental dependence of screening mechanisms in $f(R)$ and nDGP models. Using the ORIGAMI cosmic web identification routine we find that the Vainshtein mechanism depends on the cosmic web morphology of dark matter particles, since these are defined according to the dimensionality of their collapse, while the chameleon mechanism shows no morphology dependence. The chameleon screening of halos and their velocity dispersions depend on halo mass, and small halos and subhal...
Self-Constrained Euler Deconvolution Using Potential Field Data of Different Altitudes
Zhou, Wenna; Nan, Zeyu; Li, Jiyan
2016-06-01
Euler deconvolution has been developed as almost the most common tool in potential field data semi-automatic interpretation. The structural index (SI) is a main determining factor of the quality of depth estimation. In this paper, we first present an improved Euler deconvolution method to eliminate the influence of SI using potential field data of different altitudes. The different altitudes data can be obtained by the upward continuation or can be directly obtained by the airborne measurement realization. Euler deconvolution at different altitudes of a certain range has very similar calculation equation. Therefore, the ratio of Euler equations of two different altitudes can be calculated to discard the SI. Thus, the depth and location of geologic source can be directly calculated using the improved Euler deconvolution without any prior information. Particularly, the noise influence can be decreased using the upward continuation of different altitudes. The new method is called self-constrained Euler deconvolution (SED). Subsequently, based on the SED algorithm, we deduce the full tensor gradient (FTG) calculation form of the new improved method. As we all know, using multi-components data of FTG have added advantages in data interpretation. The FTG form is composed by x-, y- and z-directional components. Due to the using more components, the FTG form can get more accurate results and more information in detail. The proposed modification method is tested using different synthetic models, and the satisfactory results are obtained. Finally, we applied the new approach to Bishop model magnetic data and real gravity data. All the results demonstrate that the new approach is utility tool to interpret the potential field and full tensor gradient data.
Particle on a torus knot: Constrained dynamics and semi-classical quantization in a magnetic field
Das, Praloy; Pramanik, Souvik; Ghosh, Subir
2016-11-01
Kinematics and dynamics of a particle moving on a torus knot poses an interesting problem as a constrained system. In the first part of the paper we have derived the modified symplectic structure or Dirac brackets of the above model in Dirac's Hamiltonian framework, both in toroidal and Cartesian coordinate systems. This algebra has been used to study the dynamics, in particular small fluctuations in motion around a specific torus. The spatial symmetries of the system have also been studied. In the second part of the paper we have considered the quantum theory of a charge moving in a torus knot in the presence of a uniform magnetic field along the axis of the torus in a semiclassical quantization framework. We exploit the Einstein-Brillouin-Keller (EBK) scheme of quantization that is appropriate for multidimensional systems. Embedding of the knot on a specific torus is inherently two dimensional that gives rise to two quantization conditions. This shows that although the system, after imposing the knot condition reduces to a one dimensional system, even then it has manifested non-planar features which shows up again in the study of fractional angular momentum. Finally we compare the results obtained from EBK (multi-dimensional) and Bohr-Sommerfeld (single dimensional) schemes. The energy levels and fractional spin depend on the torus knot parameters that specifies its non-planar features. Interestingly, we show that there can be non-planar corrections to the planar anyon-like fractional spin.
Energy Technology Data Exchange (ETDEWEB)
Pueyo, Laurent [Johns Hopkins University, Department of Physics and Astronomy, 366 Bloomberg Center 3400 N. Charles Street, Baltimore, MD 21218 (United States); Hillenbrand, Lynne; Hinkley, Sasha; Dekany, Richard; Roberts, Jenny [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Vasisht, Gautam; Roberts, Lewis C. Jr.; Shao, Mike; Burruss, Rick; Cady, Eric [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Oppenheimer, Ben R.; Brenner, Douglas; Zimmerman, Neil [American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States); Monnier, John D. [Department of Astronomy, University of Michigan, 941 Dennison Building, 500 Church Street, Ann Arbor, MI 48109-1090 (United States); Crepp, Justin [Department of Physics, 225 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Parry, Ian [University of Cambridge, Institute of Astronomy, Madingley Road, Cambridge, CB3, OHA (United Kingdom); Beichman, Charles [NASA Exoplanet Science Institute, 770 South Wilson Avenue, Pasadena, CA 91225 (United States); Soummer, Remi [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2012-09-20
We report low-resolution near-infrared spectroscopic observations of the eruptive star FU Orionis using the Integral Field Spectrograph (IFS) Project 1640 installed at the Palomar Hale telescope. This work focuses on elucidating the nature of the faint source, located 0.''5 south of FU Ori, and identified in 2003 as FU Ori S. We first use our observations in conjunction with published data to demonstrate that the two stars are indeed physically associated and form a true binary pair. We then proceed to extract J- and H-band spectro-photometry using the damped LOCI algorithm, a reduction method tailored for high contrast science with IFS. This is the first communication reporting the high accuracy of this technique, pioneered by the Project 1640 team, on a faint astronomical source. We use our low-resolution near-infrared spectrum in conjunction with 10.2 {mu}m interferometric data to constrain the infrared excess of FU Ori S. We then focus on estimating the bulk physical properties of FU Ori S. Our models lead to estimates of an object heavily reddened, A{sub V} = 8-12, with an effective temperature of {approx}4000-6500 K. Finally, we put these results in the context of the FU Ori N-S system and argue that our analysis provides evidence that FU Ori S might be the more massive component of this binary system.
On the Chameleon Brans-Dicke Cosmology
Bisabr, Yousef
2012-01-01
We consider a generalized Brans-Dicke model in which the scalar field has a potential function and is also allowed to couple non-minimally with the matter sector. We assume a power law form for the potential and the coupling functions as the inputs of the model and show that acceleration of the universe can be realized for a constrained range of exponent of the potential function. We also argue that this accelerating phase is consistent with a large and positive Brans-Dicke parameter. In our analysis, the potential plays a more important role with respect to the coupling function in dynamics of the universe as the latter does not contribute to any of the relations characterizing evolution of scale factor of the universe and the scalar field. However, we will show that the coupling function is closely related to magnitude and direction of the energy transfer between matter and the scale field. We use this fact and some thermodynamic aspects of the model to put some constraints on the coupling function. In part...
Angkasa, Syahreza; Jerram, Dougal. A.; Svensen, Henrik; Millet, John M.; Taylor, Ross; Planke, Sverre
2016-04-01
In order to constrain eruption styles at the onset of flood volcanism, field observations were undertaken on basal sections of the Isle of Skye Lava Field, British Paleogene Volcanic Province. This study investigates three specific sections; Camus Ban, Neist Point and Soay Sound which sample a large area about 1500 km2 and can be used to help explain the variability in palaeo-environments at the onset of flood volcanism. Petrological analysis is coupled with petrophysical lab data and photogrammetry data to create detailed facies models for the different styles of initiating flood basalt volcanism. Photogrammetry is used to create Ortho-rectified 3D models which, along with photomontage images, allow detailed geological observations to be mapped spatially. Petrographic analyses are combined with petrophysical lab data to identify key textural variation, mineral compositions and physical properties of the volcanic rocks emplaced during the initial eruptions. Volcanism initiated with effusive eruptions in either subaerial or subaqueous environments resulting in tuff/hyaloclastite materials or lava flow facies lying directly on the older Mesozoic strata. Volcanic facies indicative of lava-water interactions vary significantly in thickness between different sections suggesting a strong accommodation space control on the style of volcanism. Camus Ban shows hyaloclastite deposits with a thickness of 25m, whereas the Soay Sound area has tuffaceous sediments of under 0.1m in thickness. Subaerial lavas overly these variable deposits in all studied areas. The flood basalt eruptions took place in mixed wet and dry environments with some significant locally developed water bodies (e.g. Camus Ban). More explosive eruptions were promoted in some cases by interaction of lavas with these water bodies and possibly by local interaction with water - saturated sediments. We record key examples of how palaeotopography imparts a primary control on the style of volcanism during the
Search for chameleons with an InGrid based X-ray detector at the CAST experiment
Energy Technology Data Exchange (ETDEWEB)
Desch, Klaus; Kaminski, Jochen; Krieger, Christoph; Schmidt, Sebastian [Physikalisches Institut, Universitaet Bonn, Nussallee 12, 53115 Bonn (Germany)
2016-07-01
The CERN Axion Solar Telescope (CAST) searches for axions and also other exotic particles emerging from the Sun. Chameleons, for example, are part of Dark Energy theories. Like Axions they can be converted into soft X-ray photons in a high magnetic field and should result in an X-ray spectrum peaking below 1 keV. Because of their low energy and weak coupling, detectors with low energy threshold and low background rates are mandatory. Both requirements are met by an X-ray detector based on the combination of a Micromegas gas amplification stage with a highly integrated pixel chip which allows to make full use of the Micromegas structure's granularity. It has been demonstrated that these devices can detect even single electrons. Thus, allowing for a topological background suppression as well as for detection of low energy X-ray photons creating only very few primary electrons. After the detection threshold had been evaluated to be low enough to allow for the detection of the carbon K{sub α} line at 277 eV, the detector was mounted at one of CAST's X-ray telescopes and installed along with its infrastructure in 2014. During data taking until end of 2015 background rates of less than 10{sup -4} keV/(cm{sup 2}.s) have been achieved below 2 keV. First preliminary results of the ongoing chameleon analysis and possibly an improved limit for solar chameleons are presented.
Palano, M.; Cannavò, F.; Ferranti, L.; Mattia, M.; Mazzella, M. E.
2011-12-01
We present an improved evaluation of the current strain and stress fields in the Southern Apennines (Italy) obtained through a careful analysis of geodetic, seismological and borehole data. In particular, our analysis provides an updated comparison between the accrued strain recorded by geodetic data, and the strain released by seismic activity in a region hit by destructive historical earthquakes. To this end, we have used nine years of GPS observations (2001-2010) from a dense network of permanent stations, a data set of 73 well-constrained stress indicators (borehole breakouts and focal mechanisms of moderate-to-large earthquakes) and published estimations of the geological strain accommodated by active faults in the region. Although geodetic data are generally consistent with seismic and geological information, previously unknown features of the current deformation in southern Italy emerge from this analysis. The newly obtained GPS velocity field supports the well-established notion of a dominant NE-SW-oriented extension concentrated in a ˜50-km-wide belt along the topographic relief of the Apennines, as outlined by the distribution of seismogenic normal faults. Geodetic deformation is, however, non-uniform along the belt, with two patches of higher strain-rate and shear-stress accumulation in the north (Matese Mountains) and in the south (Irpinia area). Low geodetic strain-rates are found in the Bradano basin and Apulia plateau to the east. Along the Ionian Sea margin of southern Italy, in southern Apulia and eastern Basilicata and Calabria, geodetic velocities indicate NW-SE extension that is consistent with active shallow-crustal gravitational motion documented by geological studies. In the west, along the Tyrrhenian margin of the Campania region, the tectonic geodetic field is disturbed by volcanic processes. Comparison between the magnitude of the geodetic and the seismic strain rates (computed using a long historical seismicity catalogue) allow detecting
Electromagnetic fields generated by constrained rotation of structural blocks in the Earth’s crust
Losseva, T. V.; Kuzmicheva, M. Y.; Spivak, A. A.
2009-12-01
Specific features of low frequency electromagnetic impulses in the subsurface Earth’s crust with a low moisture content are defined by the tectonic activity of the region and its structure as well as the stressed-strained state. Electromagnetic effects related to seismic and deformation processes in rocks are very diverse and their physical nature is different. The electric polarization of rocks deserves special attention, since this mechanism is implied in an explosive loading of rocks or relaxation processes in any hierarchic block geophysical medium [1]. The amplitudes of electromagnetic pulses generated by electric currents in a relaxing block-structured stress-strained medium have been obtained by 3D numerical modeling. The source of currents is formed by electric polarization of solids filled inter-block gaps on the active face of a block which, in turn, rotates constrainedly under relaxation. The electric current impulse is defined by the shape of the seismic impulse of the block under relaxation. The block is embedded in the crust. The full system of Maxwell equations in a conductive medium has been solved. The numerical method used has been developed to describe properly the geometry of strain as well as impressed current and conductivity profiles at every time. The figure below presents the maximal amplitudes of electric fields Emax for different active block sizes L (curves 1, 2, 3) versus the relative distances from the source epicenter x/L. Here circles denote the experimental data obtained for the Kurai tectonic structure [1]. We see that the results of numerical simulations are in good agreement with the results of measurements. This proves the validity of our model for the estimation of electric effects in the low moisture rock medium. References: [1] S.P. Soloviev and A.A. Spivak, Doklady Earth Sciences, 2007, Vol. 417A, No. 9, pp. 1449-1453.
The XMM Cluster Survey: Testing chameleon gravity using the profiles of clusters
Wilcox, Harry; Nichol, Robert C; Rooney, Philip J; Terukina, Ayumu; Romer, A Kathy; Koyama, Kazuya; Zhao, Gong-Bo; Hood, Ross; Mann, Robert G; Hilton, Matt; Manolopoulou, Maria; Sahlen, Martin; Collins, Chris A; Liddle, Andrew R; Mayers, Julian A; Mehrtens, Nicola; Miller, Christopher J; Stott, John P; Viana, Pedro T P
2015-01-01
The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas that fills the potential wells of galaxy clusters. However, it would not influence the weak lensing signal from clusters. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, $z=0.02$, Terukina et al. 2014). In this paper we apply the technique to the stacked profiles of 58 clusters at higher redshifts ($0.1
Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides
Zhao, Jie; Lu, Bing-Nan; Vretenar, Dario; Zhao, En-Guang; Zhou, Shan-Gui
2015-01-01
Background: Potential energy surfaces (PES's) of actinide nuclei are characterized by a two-humped barrier structure. At large deformations beyond the second barrier, the occurrence of a third barrier was predicted by macroscopic-microscopic model calculations in the 1970s, but contradictory results were later reported by a number of studies that used different methods. Purpose: Triple-humped barriers in actinide nuclei are investigated in the framework of covariant density functional theory (CDFT). Methods: Calculations are performed using the multidimensionally constrained relativistic mean field (MDC-RMF) model, with the nonlinear point-coupling functional PC-PK1 and the density-dependent meson exchange functional DD-ME2 in the particle-hole channel. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Results: Two-dimensional PES's of 226,228,230,232Th and 232,235,236,238U are mapped and the third minima on these surfaces are located. Then one-dimensional potential energy curves along the fission path are analyzed in detail and the energies of the second barrier, the third minimum, and the third barrier are determined. The functional DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and 238U . The third minima in 230 ,232Th are very shallow, whereas those in 226 ,228Th and 238U are quite prominent. With the functional PC-PK1 a third barrier is found only in 226 ,228 ,230Th . Single-nucleon levels around the Fermi surface are analyzed in 226Th, and it is found that the formation of the third minimum is mainly due to the Z =90 proton energy gap at β20≈1.5 and β30≈0.7 . Conclusions: The possible occurrence of a third barrier on the PES's of actinide nuclei depends on the effective interaction used in multidimensional CDFT calculations. More pronounced minima are predicted by the DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third well in Th isotopes decreases
Jawad, A.; Chattopadhyay, S.; Bhattacharya, S.; Pasqua, A.
2015-04-01
The objective of this paper is to discuss the Chameleon Brans-Dicke gravity with non-minimally matter coupling of scalar field. We take modified Holographic Ricci dark energy model in this gravity with its energy density in interaction with energy density of cold dark matter. We assume power-law ansatz for scale factor and scalar field to discuss potential as well as coupling functions in the evolving universe. These reconstructed functions are plotted versus scalar field and time for different values of power component of scale factor n. We observe that potential and coupling functions represent increasing behavior, in particular, consistent results for a specific value of n. Finally, we have examined validity of the generalized second law of thermodynamics and we have observed its validity for all values of n. The financial Supported from Department of Science and Technology, Govt. of India under Project Grant No. SR/FTP/PS-167/2011 is thankfully acknowledged by SC
Jagoutz, O. E.
2011-12-01
Geological mapping of exposed arc sections is essential to understand and quantify important continental crust forming processes. There is strong evidence that a wide range of crust formation mechanism occurs in arcs but to identify the most important one(s) detailed field observation and geological mapping at various crustal levels and in different exposed arc section that cover a wide range of earth history is essential. Here I present an up dated map of the Kohistan-Ladakh arc (KLA) that is based on field mapping and remote sensing over the last 10 years. Together with petrological constrained intrusions depth and geochemical data the map lets us constrain the 3 D architecture of an intraoceanic arc. This provides the basis to address a wide range of essential questions related to crust formation in oceanic arcs. Here I will focus on the 3D architecture of the KLA and how it compares to seismically imaged active arcs. I used bulk rock compositions to calculate constrained phase diagrams of the main rock types exposed in Kohistan. From the high temperature mineralogical composition seismic properties are calculated and a schematic 3-D seismic image of the Kohistan arc is compared to those from active arcs.
Directory of Open Access Journals (Sweden)
Avichai Lustig
Full Text Available Lateralization is mostly analyzed for single traits, but seldom for two or more traits while performing a given task (e.g. object manipulation. We examined lateralization in eye use and in body motion that co-occur during avoidance behaviour of the common chameleon, Chamaeleo chameleon. A chameleon facing a moving threat smoothly repositions its body on the side of its perch distal to the threat, to minimize its visual exposure. We previously demonstrated that during the response (i eye use and body motion were, each, lateralized at the tested group level (N = 26, (ii in body motion, we observed two similar-sized sub-groups, one exhibiting a greater reduction in body exposure to threat approaching from the left and one--to threat approaching from the right (left- and right-biased subgroups, (iii the left-biased sub-group exhibited weak lateralization of body exposure under binocular threat viewing and none under monocular viewing while the right-biased sub-group exhibited strong lateralization under both monocular and binocular threat viewing. In avoidance, how is eye use related to body motion at the entire group and at the sub-group levels? We demonstrate that (i in the left-biased sub-group, eye use is not lateralized, (ii in the right-biased sub-group, eye use is lateralized under binocular, but not monocular viewing of the threat, (iii the dominance of the right-biased sub-group determines the lateralization of the entire group tested. We conclude that in chameleons, patterns of lateralization of visual function and body motion are inter-related at a subtle level. Presently, the patterns cannot be compared with humans' or related to the unique visual system of chameleons, with highly independent eye movements, complete optic nerve decussation and relatively few inter-hemispheric commissures. We present a model to explain the possible inter-hemispheric differences in dominance in chameleons' visual control of body motion during avoidance.
Plasmonic nanoparticles tuned thermal sensitive photonic polymer for biomimetic chameleon
Yan, Yang; Liu, Lin; Cai, Zihe; Xu, Jiwen; Xu, Zhou; Zhang, Di; Hu, Xiaobin
2016-08-01
Among many thermo-photochromic materials, the color-changing behavior caused by temperature and light is usually lack of a full color response. And the study on visible light-stimuli chromic response is rarely reported. Here, we proposed a strategy to design a thermo-photochromic chameleon biomimetic material consisting of photonic poly(N-isopropylacrylamide-co-methacrylic acid) copolymer and plasmonic nanoparticles which has a vivid color change triggered by temperature and light like chameleons. We make use of the plasmonic nanoparticles like gold nanoparticles and silver nanoparticles to increase the sensitivity of the responsive behavior and control the lower critical solution temperature of the thermosensitive films by tuning the polymer chain conformation transition. Finally, it is possible that this film would have colorimetric responses to the entire VIS spectrum by the addition of different plasmonic nanoparticles to tune the plasmonic excitation wavelength. As a result, this method provides a potential use in new biosensors, military and many other aspects.
A chameleon catalyst for nonheme iron-promoted olefin oxidation.
Iyer, Shyam R; Javadi, Maedeh Moshref; Feng, Yan; Hyun, Min Young; Oloo, Williamson N; Kim, Cheal; Que, Lawrence
2014-11-18
We report the chameleonic reactivity of two nonheme iron catalysts for olefin oxidation with H2O2 that switch from nearly exclusive cis-dihydroxylation of electron-poor olefins to the exclusive epoxidation of electron-rich olefins upon addition of acetic acid. This switching suggests a common precursor to the nucleophilic oxidant proposed to Fe(III)-η(2)-OOH and electrophilic oxidant proposed to Fe(V)(O)(OAc), and reversible coordination of acetic acid as a switching pathway.
Manipulators inspired by the tongue of the chameleon.
Debray, Alexis
2011-06-01
Chameleons have developed a specialized ballistic tongue which elongates more than six times its rest length at speeds higher than 3.5 m s(-1) and accelerations 350 m s(-2), with a highly flexible mobile part, and which applies no continuous force during forward motion. These characteristics are possible because this tongue consists of two highly specialized systems, an ejection system for the forward motion and an accordion-like system for the retraction. Four manipulators inspired by the tongue of the chameleon and based on this design have been developed, resulting in three characteristics similar to the tongue of the chameleon: extensibility of the manipulator, flexibility of the mobile part, and absence of continuous force during the forward motion. The first manipulator mimics the basic mechanism of the tongue of the chameleon and reproduced its basic performances. A second manipulator performs a catching function at a speed of 3.5 m s(-1) with an acceleration of 573 m s(-2) while elongating seven times its rest length. The design of this manipulator is such that the dc motor used for retraction applies a torque 25 times its rated torque. Moreover, during the retraction, the mobile part of the manipulator moves due to its own inertia, allowing the dc motor to rotate at full velocity. In another manipulator, the addition of an elastomer in the mobile part allows for control of the retraction velocity. A model for these two manipulators compares well with the experimental data. Finally, the addition of wings on the mobile part allows us to take the advantage of aerodynamic effects, which is unusual for manipulators.
DEFF Research Database (Denmark)
Dimitrov, Nikolay Krasimirov; Lazarov, Boyan Stefanov
2015-01-01
We demonstrate a method for incorporating wind measurements from multiple-point scanning lidars into the turbulence fields serving as input to wind turbine load simulations. The measurement values are included in the analysis by applying constraints to randomly generated turbulence fields...
CONSTRAINING THE STRING GAUGE FIELD BY GALAXY ROTATION CURVES AND PERIHELION PRECESSION OF PLANETS
Energy Technology Data Exchange (ETDEWEB)
Cheung, Yeuk-Kwan E.; Xu Feng, E-mail: cheung@nju.edu.cn [Department of Physics, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)
2013-09-01
We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have observable signatures on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of 22 spiral galaxies of varied luminosities and sizes and perihelion precessions of planets in the solar system. The rotation curves of the same group of galaxies are independently fit using a dark matter model with the generalized Navarro-Frenk-White (NFW) profile and the string model. A remarkable fit of galaxy rotation curves is achieved using the one-parameter string model as compared to the three-parameter dark matter model with the NFW profile. The average {chi}{sup 2} value of the NFW fit is 9% better than that of the string model at a price of two more free parameters. Furthermore, from the string model, we can give a dynamical explanation for the phenomenological Tully-Fisher relation. We are able to derive a relation between field strength, galaxy size, and luminosity, which can be verified with data from the 22 galaxies. To further test the hypothesis of the universal existence of the string gauge field, we apply our string model to the solar system. Constraint on the magnitude of the string field in the solar system is deduced from the current ranges for any anomalous perihelion precession of planets allowed by the latest observations. The field distribution resembles a dipole field originating from the Sun. The string field strength deduced from the solar system observations is of a similar magnitude as the field strength needed to sustain the rotational speed of the Sun inside the Milky Way. This hypothesis can be tested further by future observations with higher precision.
Constraining Large-Scale Solar Magnetic Field Models with Optical Coronal Observations
Uritsky, V. M.; Davila, J. M.; Jones, S. I.
2015-12-01
Scientific success of the Solar Probe Plus (SPP) and Solar Orbiter (SO) missions will depend to a large extent on the accuracy of the available coronal magnetic field models describing the connectivity of plasma disturbances in the inner heliosphere with their source regions. We argue that ground based and satellite coronagraph images can provide robust geometric constraints for the next generation of improved coronal magnetic field extrapolation models. In contrast to the previously proposed loop segmentation codes designed for detecting compact closed-field structures above solar active regions, we focus on the large-scale geometry of the open-field coronal regions located at significant radial distances from the solar surface. Details on the new feature detection algorithms will be presented. By applying the developed image processing methodology to high-resolution Mauna Loa Solar Observatory images, we perform an optimized 3D B-line tracing for a full Carrington rotation using the magnetic field extrapolation code presented in a companion talk by S.Jones at al. Tracing results are shown to be in a good qualitative agreement with the large-scalie configuration of the optical corona. Subsequent phases of the project and the related data products for SSP and SO missions as wwll as the supporting global heliospheric simulations will be discussed.
Higher-Derivative Boson Field Theories and Constrained Second-Order Theories
D'Urríes, F J; Villaseñor, E J S; Villase\\~nor, Eduardo J.S.
2001-01-01
As an alternative to the covariant Ostrogradski method, we show that higher-derivative relativistic Lagrangian field theories can be reduced to second differential-order by writing them directly as covariant two-derivative theories involving Lagrange multipliers and new fields. Despite the intrinsic non-covariance of the Dirac's procedure used to deal with the constraints, the explicit Lorentz invariance is recovered at the end. We develop this new setting on the grounds of a simple scalar model and then its applications to generalized electrodynamics and higher-derivative gravity are worked out. For a wide class of field theories this method is better suited than Ostrogradski's for a generalization to 2n-derivative theories
Higher-derivative boson field theories and constrained second-order theories
Energy Technology Data Exchange (ETDEWEB)
Urries, F.J. de [Departamento de Fisica, Universidad de Alcala de Henares, Madrid (Spain) and IMAFF, Consejo Superior de Investigaciones Cientificas, Madrid (Spain)]. E-mail: fernando.urries@uah.es; Julve, J. [IMAFF, Consejo Superior de Investigaciones Cientificas, Madrid (Spain)]. E-mail: julve@imaff.cfmac.csic.es; Sanchez, E.J. [IMAFF, Consejo Superior de Investigaciones Cientificas, Madrid (ES) and Departamento de Matematica, Universidad Europea, Madrid (Spain)]. E-mail: ejesus.sanchez@mat.ind.uem.es
2001-10-26
As an alternative to the covariant Ostrogradski method, we show that higher-derivative (HD) relativistic Lagrangian field theories can be reduced to second differential order by writing them directly as covariant two-derivative theories involving Lagrange multipliers and new fields. Despite the intrinsic non-covariance of the Dirac procedure used to deal with the constraints, the explicit Lorentz invariance is recovered at the end. We develop this new setting on the basis of a simple scalar model and then its applications to generalized electrodynamics and HD gravity are worked out. For a wide class of field theories this method is better suited than Ostrogradski's for a generalization to 2n-derivative theories. (author)
Note on scalars, perfect fluids, constrained field theories, and all that
Diez-Tejedor, Alberto
2013-01-01
The relation of a scalar field with a perfect fluid has generated some debate along the last few years. In this paper we argue that shift-invariant scalar fields can describe accurately the potential flow of an isentropic perfect fluid, but, in general, the identification is possible only for a finite period of time. After that period in the evolution the dynamics of the scalar field and the perfect fluid branch off. The Lagrangian density for the velocity-potential can be read directly from the expression relating the pressure with the Taub charge and the entropy per particle in the fluid, whereas the other quantities of interest can be obtained from the thermodynamic relations.
Note on scalars, perfect fluids, constrained field theories, and all that
Energy Technology Data Exchange (ETDEWEB)
Diez-Tejedor, Alberto
2013-11-25
The relation of a scalar field with a perfect fluid has generated some debate along the last few years. In this Letter we argue that shift-invariant scalar fields can describe accurately the potential flow of an isentropic perfect fluid, but, in general, the identification is possible only for a finite period of time. After that period in the evolution the dynamics of the scalar field and the perfect fluid branch off. The Lagrangian density for the velocity-potential can be read directly from the expression relating the pressure with the Taub charge and the entropy per particle in the fluid, whereas the other quantities of interest can be obtained from the thermodynamic relations.
Higher-derivative scalar field theories as constrained second-order theories
Urries, F J
1998-01-01
As an alternative to the covariant Ostrogradski method, we show that higher-derivative relativistic Lagrangian field theories can be reduced to second differential-order by writing them directly as covariant two-derivative theories involving Lagrange multipliers and new fields. Notwithstanding the intrinsic non-covariance of the Dirac's procedure used to deal with the constraints, the Lorentz invariance is recovered at the end. We develope this new setting for a simple scalar model and then its applications to generalized electrodynamics and higher-derivative gravity are outlined. This method is better suited than Ostrogradski's for a generalization to 2n-derivative theories.
Le Brocq, A. M.; Bentley, M. J.; Hubbard, A.; Fogwill, C. J.; Sugden, D. E.; Whitehouse, P. L.
2011-09-01
The Weddell Sea Embayment (WSE) sector of the Antarctic ice sheet has been suggested as a potential source for a period of rapid sea-level rise - Meltwater Pulse 1a, a 20 m rise in ˜500 years. Previous modelling attempts have predicted an extensive grounding line advance in the WSE, to the continental shelf break, leading to a large equivalent sea-level contribution for the sector. A range of recent field evidence suggests that the ice sheet elevation change in the WSE at the Last Glacial Maximum (LGM) is less than previously thought. This paper describes and discusses an ice flow modelling derived reconstruction of the LGM ice sheet in the WSE, constrained by the recent field evidence. The ice flow model reconstructions suggest that an ice sheet consistent with the field evidence does not support grounding line advance to the continental shelf break. A range of modelled ice sheet surfaces are instead produced, with different grounding line locations derived from a novel grounding line advance scheme. The ice sheet reconstructions which best fit the field constraints lead to a range of equivalent eustatic sea-level estimates between approximately 1.4 and 3 m for this sector. This paper describes the modelling procedure in detail, considers the assumptions and limitations associated with the modelling approach, and how the uncertainty may impact on the eustatic sea-level equivalent results for the WSE.
Wang, Huiyuan; Yang, Xiaohu; Zhang, Youcai; Shi, JingJing; Jing, Y P; Liu, Chengze; Li, Shijie; Kang, Xi; Gao, Yang
2016-01-01
A method we developed recently for the reconstruction of the initial density field in the nearby Universe is applied to the Sloan Digital Sky Survey Data Release 7. A high-resolution N-body constrained simulation (CS) of the reconstructed initial condition, with $3072^3$ particles evolved in a 500 Mpc/h box, is carried out and analyzed in terms of the statistical properties of the final density field and its relation with the distribution of SDSS galaxies. We find that the statistical properties of the cosmic web and the halo populations are accurately reproduced in the CS. The galaxy density field is strongly correlated with the CS density field, with a bias that depend on both galaxy luminosity and color. Our further investigations show that the CS provides robust quantities describing the environments within which the observed galaxies and galaxy systems reside. Cosmic variance is greatly reduced in the CS so that the statistical uncertainties can be controlled effectively even for samples of small volumes...
Cl constrains on shallow plumbing system and pre-eruptive conditions of the Phlegrean Fields.
Zdanowicz, Géraldine; Balcone-Boissard, Hélène; Boudon, Georges; Civetta, Lucia; Orsi, Giovanni; D'Antonio, Massimo
2015-04-01
The bay of Naples is known to concentrate several dangerous volcanoes that erupted a lot of times in prehistorical and historical periods: Vesuvius, Phlegrean Fields and Ischia Island. Phlegrean Fields produced voluminous high-magnitude eruptions including: the Campanian Ignimbrite (39 ka BP), one of the two largest explosive eruptions of the Mediterranean region during the last 200,000 years, with 300 km3 of magma emitted, and the Neapolitan Yellow Tuff (15 ka BP), the second major eruption (40 km3 of magma emitted). The Ischia Island is located in the Bay of Naples and its eruptive history has been recently detailed. We present a geochemical investigation of volatile components on the fallout products of the major explosive eruptions of Phlegrean Fields: the Campanian Ignimbrite (39 ka BP), the Neapolitan Yellow Tuff (15 ka BP), the Pomici Principali (10 ka BP; 0.38 km3 DRE magma), the Agnano Monte-Spina (4.1 ka BP; 0.60 km3 DRE magma); the Astroni 6 (3.8 ka BP; 0.70 km3 DRE magma); the Monte Nuovo (1,538 AD), which is the most recent eruption of the Phlegrean Fields (0.04 km3 DRE magma), and for comparison the Cretaio eruption of the Ischia Island (1,800 a BP; 0.02 km3 DRE magma). Volatiles of magmas (H2O, CO2, SO2, Cl, F) are informative not only because they play a key role in the eruptive dynamic but also because they, and especially chlorine, may allow estimating the pressure of localization of the magma storage and pre-eruptive water content (prior the eruption). In the alkaline magmas involved during the Phlegrean Fields eruptions, H2O is the main volatile species but Cl behaviour is particularly interesting to study. Experimentally, it has been demonstrated that in a pressure, temperature and composition domain a water-saturated magma may be in equilibrium with a fluid phase consisting of a water-rich vapor and a chlorine-rich brine. In that case, the Cl content in magma is buffered. This effect allows determining the pressure of localization of
Zhao, Jie; Niksic, Tamara; Vretenar, Dario; Zhou, Shan-Gui
2016-01-01
Studies of fission dynamics, based on nuclear energy density functionals, have shown that the coupling between shape and pairing degrees of freedom has a pronounced effect on the nonperturbative collective inertia and, therefore, on dynamic (least-action) spontaneous fission paths and half-lives. Collective potentials and nonperturbative cranking collective inertia tensors are calculated using the multidimensionally-constrained relativistic mean-field (MDC-RMF) model. Pairing correlations are treated in the BCS approximation using a separable pairing force of finite range. Pairing fluctuations are included as a collective variable using a constraint on particle-number dispersion. Fission paths are determined with the dynamic programming method by minimizing the action in multidimensional collective spaces. The dynamics of spontaneous fission of $^{264}$Fm and $^{250}$Fm are explored. Fission paths, action integrals and corresponding half-lives computed in the three-dimensional collective space of shape and pa...
Wind field and sex constrain the flight speeds of central-place foraging albatrosses
Wakefield, Ewan D.; Phillips, Richard A.; Matthiopoulos, Jason; Fukuda, Akira; Higuchi, Hiroyoshi; Marshall, Gareth J.; Philip N. Trathan
2009-01-01
By extracting energy from the highly dynamic wind and wave fields that typify pelagic habitats, albatrosses are able to proceed almost exclusively by gliding flight. Although energetic costs of gliding are low, enabling breeding albatrosses to forage hundreds to thousands of kilometers from their colonies, these and time costs vary with relative wind direction. This causes albatrosses in some areas to route provisioning trips to avoid headwind flight, potentially limiting habitat accessibilit...
Field cage development for a time-projection chamber to constrain the nuclear symmetry energy
Estee, J.; Barney, J.; Chajecki, Z.; Famiano, M.; Dunn, J.; Lu, F.; Lynch, W. G.; McIntosh, A. B.; Isobe, T.; Murakami, T.; Sakurai, H.; Shane, R.; Taketani, A.; Tangwancharoen, S.; Tsang, M. B.; Yennello, S.
2012-10-01
The SAMURAI time-projection chamber (sTPC) is being developed for use in the dipole magnet of the newly-commissioned SAMURAI spectrometer at the RIBF facility in Japan. The main scientific objective of the sTPC is to provide constraints on the nuclear symmetry energy at supra-saturation densities. The TPC allows for tracking and identification of light charged particles such as pions, protons, tritons and ^3He. The sTPC must have a Cartesian geometry to match the symmetry of the dipole magnet. The walls of the field cage (FC) detector volume consist of sections of rigid, two-layer circuit boards. Inside and outside copper strips form decreasing equipotentials via a resistor chain, and create a uniform electric field with a maximum of 400 V/cm. The FC volume is hermetically sealed from the enclosure volume to create an insulation volume which can be filled with dry N2 to inhibit corona discharge. I will be presenting the current status of the design and assembly of the sTPC field cage.
Aleksić, J.; Alvarez, E. A.; Antonelli, L. A.; Antoranz, P.; Asensio, M.; Backes, M.; Barres de Almeida, U.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Borla Tridon, D.; Braun, I.; Bretz, T.; Cañellas, A.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Cea Del Pozo, E.; de Lotto, B.; Delgado Mendez, C.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Eisenacher, D.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido, D.; Giavitto, G.; Godinović, N.; Gozzini, S. R.; Hadasch, D.; Häfner, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Jogler, T.; Kellermann, H.; Klepser, S.; Krähenbühl, T.; Krause, J.; Kushida, J.; La Barbera, A.; Lelas, D.; Leonardo, E.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López, R.; López-Oramas, A.; Lorenz, E.; Makariev, M.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moldón, J.; Moralejo, A.; Munar-Adrover, P.; Niedzwiecki, A.; Nieto, D.; Nilsson, K.; Nowak, N.; Orito, R.; Paiano, S.; Paneque, D.; Paoletti, R.; Pardo, S.; Paredes, J. M.; Partini, S.; Perez-Torres, M. A.; Persic, M.; Peruzzo, L.; Pilia, M.; Pochon, J.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puerto Gimenez, I.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamatescu, V.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Treves, A.; Uellenbeck, M.; Vankov, H.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Pfrommer, C.; Pinzke, A.
2012-05-01
Galaxy clusters are being assembled today in the most energetic phase of hierarchical structure formation which manifests itself in powerful shocks that contribute to a substantial energy density of cosmic rays (CRs). Hence, clusters are expected to be luminous gamma-ray emitters since they also act as energy reservoirs for additional CR sources, such as active galactic nuclei and supernova-driven galactic winds. To detect the gamma-ray emission from CR interactions with the ambient cluster gas, we conducted the deepest to date observational campaign targeting a galaxy cluster at very high-energy gamma-rays and observed the Perseus cluster with the MAGIC Cherenkov telescopes for a total of ~85 h of effective observing time. This campaign resulted in the detection of the central radio galaxy NGC 1275 at energies E > 100 GeV with a very steep energy spectrum. Here, we restrict our analysis to energies E > 630 GeV and detect no significant gamma-ray excess. This constrains the average CR-to-thermal pressure ratio to be ≲1-2%, depending on assumptions and the model for CR emission. Comparing these gamma-ray upper limits to models inferred from cosmological cluster simulations that include CRs constrains the maximum CR acceleration efficiency at structure formation shocks to be 4-9 μG, depending on the rate of decline of the magnetic field strength toward larger radii. This range is well below field strengths inferred from Faraday rotation measurements in cool cores. Hence, the hadronic model remains a plausible explanation of the Perseus radio mini-halo.
Schmidt, Volker; Klasen, Linus; Schneider, Juliane; Hübel, Jens; Pees, Michael
2017-03-01
Metarhizium viride has been associated with fatal systemic mycoses in chameleons, but subsequent data on mycoses caused by this fungus in reptiles are lacking. The aim of this investigation was therefore to obtain information on the presence of M. viride in reptiles kept as pets in captivity and its association with clinical signs and pathological findings as well as improvement of diagnostic procedures. Beside 18S ribosomal DNA (rDNA) (small subunit [SSU]) and internal transcribed spacer region 1 (ITS-1), a fragment of the large subunit (LSU) of 28S rDNA, including domain 1 (D1) and D2, was sequenced for the identification of the fungus and phylogenetic analysis. Cultural isolation and histopathological examinations as well as the pattern of antifungal drug resistance, determined by using agar diffusion testing, were additionally used for comparison of the isolates. In total, 20 isolates from eight inland bearded dragons (Pogona vitticeps), six veiled chameleons (Chamaeleo calyptratus), and six panther chameleons (Furcifer pardalis) were examined. Most of the lizards suffered from fungal glossitis, stomatitis, and pharyngitis or died due to visceral mycosis. Treatment with different antifungal drugs according to resistance patterns in all three different lizard species was unsuccessful. Sequence analysis resulted in four different genotypes of M. viride based on differences in the LSU fragment, whereas the SSU and ITS-1 were identical in all isolates. Sequence analysis of the SSU fragment revealed the first presentation of a valid large fragment of the SSU of M. viride According to statistical analysis, genotypes did not correlate with differences in pathogenicity, antifungal susceptibility, or species specificity. Copyright © 2017 American Society for Microbiology.
Recover Act. Verification of Geothermal Tracer Methods in Highly Constrained Field Experiments
Energy Technology Data Exchange (ETDEWEB)
Becker, Matthew W. [California State University, Long Beach, CA (United States)
2014-05-16
The prediction of the geothermal system efficiency is strong linked to the character of the flow system that connects injector and producer wells. If water flow develops channels or “short circuiting” between injection and extraction wells thermal sweep is poor and much of the reservoir is left untapped. The purpose of this project was to understand how channelized flow develops in fracture geothermal reservoirs and how it can be measured in the field. We explored two methods of assessing channelization: hydraulic connectivity tests and tracer tests. These methods were tested at a field site using two verification methods: ground penetrating radar (GPR) images of saline tracer and heat transfer measurements using distributed temperature sensing (DTS). The field site for these studies was the Altona Flat Fractured Rock Research Site located in northeastern New York State. Altona Flat Rock is an experimental site considered a geologic analog for some geothermal reservoirs given its low matrix porosity. Because soil overburden is thin, it provided unique access to saturated bedrock fractures and the ability image using GPR which does not effectively penetrate most soils. Five boreholes were drilled in a “five spot” pattern covering 100 m2 and hydraulically isolated in a single bedding plane fracture. This simple system allowed a complete characterization of the fracture. Nine small diameter boreholes were drilled from the surface to just above the fracture to allow the measurement of heat transfer between the fracture and the rock matrix. The focus of the hydraulic investigation was periodic hydraulic testing. In such tests, rather than pumping or injection in a well at a constant rate, flow is varied to produce an oscillating pressure signal. This pressure signal is sensed in other wells and the attenuation and phase lag between the source and receptor is an indication of hydraulic connection. We found that these tests were much more effective than constant
Recover Act. Verification of Geothermal Tracer Methods in Highly Constrained Field Experiments
Energy Technology Data Exchange (ETDEWEB)
Becker, Matthew W. [California State University, Long Beach, CA (United States)
2014-05-16
The prediction of the geothermal system efficiency is strong linked to the character of the flow system that connects injector and producer wells. If water flow develops channels or “short circuiting” between injection and extraction wells thermal sweep is poor and much of the reservoir is left untapped. The purpose of this project was to understand how channelized flow develops in fracture geothermal reservoirs and how it can be measured in the field. We explored two methods of assessing channelization: hydraulic connectivity tests and tracer tests. These methods were tested at a field site using two verification methods: ground penetrating radar (GPR) images of saline tracer and heat transfer measurements using distributed temperature sensing (DTS). The field site for these studies was the Altona Flat Fractured Rock Research Site located in northeastern New York State. Altona Flat Rock is an experimental site considered a geologic analog for some geothermal reservoirs given its low matrix porosity. Because soil overburden is thin, it provided unique access to saturated bedrock fractures and the ability image using GPR which does not effectively penetrate most soils. Five boreholes were drilled in a “five spot” pattern covering 100 m2 and hydraulically isolated in a single bedding plane fracture. This simple system allowed a complete characterization of the fracture. Nine small diameter boreholes were drilled from the surface to just above the fracture to allow the measurement of heat transfer between the fracture and the rock matrix. The focus of the hydraulic investigation was periodic hydraulic testing. In such tests, rather than pumping or injection in a well at a constant rate, flow is varied to produce an oscillating pressure signal. This pressure signal is sensed in other wells and the attenuation and phase lag between the source and receptor is an indication of hydraulic connection. We found that these tests were much more effective than constant
Dynamical degrees of freedom of constrained quantum field theories (sigma-model)
Energy Technology Data Exchange (ETDEWEB)
Alonso, F.; Julve, J.; Tiemblo, A.; Tresguerres, R.
1985-09-01
A complete Path Integral Quantization scheme is outlined starting from the Hamiltonian of a theory of N-scalar fields with a constraint (phi/sup 2/-r/sup 2/)=0. The process generates secondary constraints which allow us to recover the traditional Lagrangian after some functional integrations. A prescription to impose 2nd class constraints which makes use of the Lagrange's multiplier method allows to obtain a class of finite Green's Functions. These Green's functions can be seen to involve only (N-1) independent sources.
Constraining String Gauge Field by Galaxy Rotation Curve and Planet Perihelion Precession
Cheung, Yeuk-Kwan Edna
2011-01-01
We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have effects on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of twenty-two spiral galaxies of varied luminosities and sizes, and perihelion precessions of planets in the solar system. Remarkable fit of galaxy rotation curves is achieved using the one-parameter string model as contrasted to the three-parameter model of dark matter model with the Navarro-Frenk-White profile. The rotation curves of the same group of galaxies are independently fit using dark matter model with the generalized Navarro-Frenk-White profile and using the string model. The average chi-squared of the NFW fit is 9% better than that of the string model at a price of two more free parameters. From the string model we give a dynamical explanation of Tully-Fisher relation. We are able to derive a relation between field strength, g...
Tsunami-generated magnetic fields may constrain focal mechanisms of earthquakes.
Kawashima, Issei; Toh, Hiroaki
2016-06-29
A geomagnetic observatory named SFEMS is being operated on the deep seafloor in the northwest Pacific since August, 2001. SFEMS is capable of measuring both scalar and vector geomagnetic fields as well as the seafloor instrument's precise attitudes, which makes it a powerful tool in detecting the so-called oceanic dynamo effect. It was found that SFEMS captured clear magnetic signals generated by the giant tsunamis of the 2011 Tohoku Earthquake even for an epicentral distance of larger than 1500 km. Here we report estimates of the focal mechanism of a closer tsunamigenic earthquake in January, 2007 on the seaward slope of the Kuril Trench using tsunami-generated variations in the observed downward magnetic component. Three-dimensional solutions of the tsunami-generated magnetic components were calculated by a new numerical code based on non-uniform thin-sheet approximation and particle motions of seawater using the linear Boussinesq approximation. As a result, a southeast dipping fault alone reproduced the dispersive nature of the downward magnetic component, while any northwest dipping faults could not. This implies that the tsunami-generated electromagnetic fields are useful for determination of focal mechanisms of tsunamigenic earthquakes, since fault dips are one of the most difficult source parameters to estimate even in modern seismology.
The Chameleon Suit--a liberated future for space explorers.
Hodgson, Edward
2003-06-01
Mankind's spacefaring future demands the ability to work freely and frequently in space. Traditional spacesuit systems burden both the spacefarer and the mission, limiting the extent to which this is possible. The spacefarer is burdened by a pressure suit designed for isolation from the environment and a life support system designed to replace everything our environment normally provides. The space mission is burdened by this equipment and the expendable materials to operate and maintain it. We aren't free to work in space as frequently, as long, or in all of the locations envisioned. The NASA Institute for Advanced Concepts (NIAC) has sponsored research on an alternative concept, the "Chameleon Suit", that seeks to liberate future explorers and missions from these limitations. The Chameleon Suit system works with the environment in an adaptive fashion to minimize hardware and expendable materials. To achieve this, functions of the life support system are integrated with the pressure suit using emerging materials and design technology. Technologies under study include shape change polymers and electroemissive materials to modify heat transfer characteristics of the spacesuit "skin" achieving thermoregulation analogous to that in natural biological systems. This approach was shown to be feasible for many space missions during the Phase 1 study program. The current Phase 2 program is investigating more aggressive concepts aimed at eliminating most of the hardware currently included in the spacesuit's life support backpack. This paper describes the concept, study results to date, and possible impacts on future human space exploration.
Constraining local UV field geometry at reionization using Milky Way satellites
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Aubert D.
2012-02-01
Full Text Available We present a new semi-analytical model of the population of satellite galaxies of the Milky Way, aimed at estimating the effect of the geometry of reionization at galaxy scale on the properties of the satellites. In this model reionization can be either: (A externally-driven and uniform, or (B internally-driven, by the most massive progenitor of the Milky Way. In the latter scenario the propagation of the ionisation front and photon dilution introduce a delay in the photo-evaporation of the outer satellites’ gas with respect to the inner satellites. As a consequence, outer satellites experience a longer period of star formation than those in the inner halo. We use simple models to account for star formation, the propagation of the ionisation front, photo-evaporation and observational biases. Both scenarios yield a model satellite population that matches the observed luminosity function and mass-to-light ratios. However, the predicted population for scenario (B is significantly more extended spatially than for scenario (A, by about 0.3 dex in distance, resulting in a much better match to the observations. The survival of the signature left by the local UV field during reionization on the radial distribution of satellites makes it a promising tool for studying the reionization epoch at galaxy scale in the Milky Way and nearby galaxies resolved in stars with forthcoming large surveys.
Smith, Helen R.; Baran, Anthony J.; Hesse, Evelyn; Hill, Peter G.; Connolly, Paul J.; Webb, Ann
2016-11-01
A single habit parameterization for the shortwave optical properties of cirrus is presented. The parameterization utilizes a hollow particle geometry, with stepped internal cavities as identified in laboratory and field studies. This particular habit was chosen as both experimental and theoretical results show that the particle exhibits lower asymmetry parameters when compared to solid crystals of the same aspect ratio. The aspect ratio of the particle was varied as a function of maximum dimension, D, in order to adhere to the same physical relationships assumed in the microphysical scheme in a configuration of the Met Office atmosphere-only global model, concerning particle mass, size and effective density. Single scattering properties were then computed using T-Matrix, Ray Tracing with Diffraction on Facets (RTDF) and Ray Tracing (RT) for small, medium, and large size parameters respectively. The scattering properties were integrated over 28 particle size distributions as used in the microphysical scheme. The fits were then parameterized as simple functions of Ice Water Content (IWC) for 6 shortwave bands. The parameterization was implemented into the GA6 configuration of the Met Office Unified Model along with the current operational long-wave parameterization. The GA6 configuration is used to simulate the annual twenty-year short-wave (SW) fluxes at top-of-atmosphere (TOA) and also the temperature and humidity structure of the atmosphere. The parameterization presented here is compared against the current operational model and a more recent habit mixture model.
Constraining conformal field theories with a higher spin symmetry in d > 3 dimensions
Alba, Vasyl; Diab, Kenan
2016-03-01
We study unitary conformal field theories with a unique stress tensor and at least one higher-spin conserved current in d > 3 dimensions. We prove that every such theory contains an infinite number of higher-spin conserved currents of arbitrarily high spin, and that Ward identities generated by the conserved charges of these currents imply that the correlators of the stress tensor and the conserved currents of the theory must coincide with one of the following three possibilities: a) a theory of n free bosons (for some integer n), b) a theory of n free fermions, or c) a theory of nd-2/2 -forms. For d even, all three structures exist, but for d odd, it may be the case that the third structure (c) does not; if it does exist, it is unclear what theory, if any, realizes it. This is a generalization of the result proved in three dimensions by Maldacena and Zhiboedov [1]. This paper supersedes the previous paper by the authors [2].
Constraining conformal field theories with a higher spin symmetry in d> 3 dimensions
Alba, Vasyl
2015-01-01
We study unitary conformal field theories with a unique stress tensor and at least one higher-spin conserved current in d>3 dimensions. We prove that every such theory contains an infinite number of higher-spin conserved currents of arbitrarily high spin, and that Ward identities generated by the conserved charges of these currents imply that the correlators of the stress tensor and the conserved currents of the theory must coincide with one of the following three possibilities: a) a theory of n free bosons (for some integer n), b) a theory of n free fermions, or c) a theory of n (d-2)/2-forms. For d even, all three structures exist, but for d odd, it may be the case that the third structure (c) does not; if it does exist, it is unclear what theory, if any, realizes it. This is a generalization of the result proved in three dimensions by Maldacena and Zhiboedov [arXiv:1112.1016]. This paper supersedes the previous paper by the authors [arXiv:1307.8092
Sturz, Bradley R; Kilday, Zachary A; Bodily, Kent D
2013-10-01
Environment size has been shown to influence the reliance on local and global geometric cues during reorientation. Unless changes in environment size are produced by manipulating length and width proportionally, changes in environment size are confounded by the amount of the environment that is visible from a single vantage point. Yet, the influence of the amount of the environment that is visible from any single vantage point on the use of local and global geometric cues remains unknown. We manipulated the amount of an environment that was visually available to participants by manipulating field of view (FOV) in a virtual environment orientation task. Two groups of participants were trained in a trapezoid-shaped enclosure to find a location that was uniquely specified by both local and global geometric cues. One group (FOV 50°) had visually less of the environment available to them from any one perspective compared to another group (FOV 100°). Following training, we presented both groups with a control test along with three novel-shaped environments. Testing assessed the use of global geometry in isolation, in alignment with local geometry, or in conflict with local geometry. Results (confirmed by a follow-up experiment) indicated that constraining FOV prevented extraction of geometric properties and relationships of space and resulted in an inability to use either global or local geometric cues for reorientation.
On the anomalous afterglow seen in a chameleon afterglow search
Steffen, Jason H; Baumbaugh, Alan; Chou, Aaron S; Tomlin, Ray
2012-01-01
We present data from our investigation of the anomalous orange-colored afterglow that was seen in the GammeV Chameleon Afterglow Search (CHASE). These data includes information about the broad band color of the observed glow, the relationship between the glow and the temperature of the apparatus, and other data taken prior to and during the science operations of CHASE. While differing in several details, the generic properties of the afterglow from CHASE are similar to luminescence seen in some vacuum compounds. Contamination from this, or similar, luminescent signatures will likely impact the design of implementation of future experiments involving single photon detectors and high intensity light sources in a cryogenic environment.
Diestel, A.; Niemann, R.; Schleicher, B.; Schwabe, S.; Schultz, L.; Fähler, S.
2015-07-01
Ferroic cooling processes that rely on field-induced first-order transformations of solid materials are a promising step towards a more energy-efficient refrigeration technology. In particular, thin films are discussed for their fast heat transfer and possible applications in microsystems. Substrate-constrained films are not useful since their substrates act as a heat sink. In this article, we examine a substrate-constrained and a freestanding epitaxial film of magnetocaloric Ni-Mn-Ga-Co. We compare phase diagrams and entropy changes obtained by magnetic field and temperature scans, which differ. We observe an asymmetry of the hysteresis between heating and cooling branch, which vanishes at high magnetic fields. These effects are discussed with respect to the vector character of a magnetic field, which acts differently on the nucleation and growth processes compared to the scalar character of the temperature.
Solar system and equivalence principle constraints on f(R) gravity by chameleon approach
Capozziello, Salvatore
2007-01-01
We study constraints on f(R) dark energy models from solar system experiments combined with experiments on the violation of equivalence principle. When the mass of an equivalent scalar field degree of freedom (scalaron) is heavy in a region with high density, a spherically symmetric body has a thin-shell so that an effective coupling of the fifth force is suppressed through a chameleon mechanism. We place experimental bounds on the cosmologically viable models recently proposed in literature which have an asymptotic form f(R)=R-lambda R_c [1-(R_c/R)^{2n}] in the regime R>>R_c. From the solar-system constraints on the post-Newtonian parameter gamma, we derive the bound n>0.5, whereas a thin-shell condition for the atmosphere of the Earth as well as the constraints from weak and strong equivalence principles give the bound n>1. This allows a possibility to find the deviation from the LambdaCDM cosmological model around the present epoch. For the model f(R)=R-lambda R_c(R/R_c)^p with 0
Force sensor for chameleon and Casimir force experiments with parallel-plate configuration
Almasi, Attaallah; Iannuzzi, Davide; Sedmik, René I P
2015-01-01
The search for non-Newtonian forces has been pursued following many different paths. Recently it was suggested that hypothetical chameleon interactions, which might explain the mechanisms behind dark energy, could be detected in a high-precision force measurement. In such an experiment, interactions between parallel plates kept at constant separation could be measured as a function of the pressure of an ambient gas, thereby identifying chameleon interactions by their unique inverse dependence on the local mass density. During the past years we have been developing a new kind of setup complying with the high requirements of the proposed experiment. In this article we present the first and most important part of this setup -- the force sensor. We discuss its design, fabrication, and characterization. From the results of the latter we derive limits on chameleon interaction parameters that could be set by the forthcoming experiment. Finally, we describe the opportunity to use the same setup to measure Casimir for...
Schmidt, Volker; Plenz, Bastian; Pfaff, Miriam; Pees, Michael
2012-12-28
The aim of the examination was to gain knowledge on the incidence of Chamaeleomyces granulomatis mycosis in Veiled chameleons (Chamaeleo calyptratus), a disease which has recently been described as a single outbreak in a zoo collection. During a time period of 26 months (September 2009-November 2011) 18 Veiled chameleons presented at the clinic for various reasons were examined for the presence of C. granulomatis. Swabs were taken from tongue and skin lesions of live chameleons and from internal granulomas of deceased chameleons. Mycological culture was performed on Sabouraud dextrose and Potato dextrose agar as described previously. For the first time, the obtained isolates were screened for susceptibility towards different antifungal drugs by use of agar diffusion testing. Fungal species were determined by amplification with different primers, as reported before, and sequencing of parts of the 28S rDNA gene, the 18S rDNA gene, internal transcribed spacer region-1 DNA and 5.8S rDNA gene. Ten cases of disseminated mycosis caused by C. granulomatis were thus documented. These animals were kept in nine different collections of differing owners. Common findings in diseased chameleons were disseminated mycosis, glossitis and dermatitis. Although all isolates were tested sensitive to terbinafine and nystatin. The results of this study clearly show, contrary to a recently published single outbreak in a zoo collection, that disseminated mycosis caused by C. granulomatis in Veiled chameleons is, a common and often fatal infectious disease in this species. The routes of infection or treatment options are still unknown and need further investigation.
Adolescents as chameleons? : social-environmental factors involved in the development of smoking
Harakeh, Zeena
2006-01-01
Why do some adolescents initiate smoking and continue in young adulthood and others do not? Do young people react to their immediate environment and adjust their behavior to this environment, in other words, do young people behave as chameleons? The detrimental consequences of smoking in combination
Adolescents as chameleons? : social-environmental factors involved in the development of smoking
Harakeh, Zeena
2006-01-01
Why do some adolescents initiate smoking and continue in young adulthood and others do not? Do young people react to their immediate environment and adjust their behavior to this environment, in other words, do young people behave as chameleons? The detrimental consequences of smoking in combination
A unique life history among tetrapods: an annual chameleon living mostly as an egg.
Karsten, Kristopher B; Andriamandimbiarisoa, Laza N; Fox, Stanley F; Raxworthy, Christopher J
2008-07-01
The approximately 28,300 species of tetrapods (four-limbed vertebrates) almost exclusively have perennial life spans. Here, we report the discovery of a remarkable annual tetrapod from the arid southwest of Madagascar: the chameleon Furcifer labordi, with a posthatching life span of just 4-5 months. At the start of the active season (November), an age cohort of hatchlings emerges; larger juveniles or adults are not present. These hatchlings grow rapidly, reach sexual maturity in less than 2 months, and reproduce in January-February. After reproduction, senescence appears, and the active season concludes with population-wide adult death. Consequently, during the dry season, the entire population is represented by developing eggs that incubate for 8-9 months before synchronously hatching at the onset of the following rainy season. Remarkably, this chameleon spends more of its short annual life cycle inside the egg than outside of it. Our review of tetrapod longevity (>1,700 species) finds no others with such a short life span. These findings suggest that the notorious rapid death of chameleons in captivity may, for some species, actually represent the natural adult life span. Consequently, a new appraisal may be warranted concerning the viability of chameleon breeding programs, which could have special significance for species of conservation concern. Additionally, because F. labordi is closely related to other perennial species, this chameleon group may prove also to be especially well suited for comparative studies that focus on life history evolution and the ecological, genetic, and/or hormonal determinants of aging, longevity, and senescence.
Katz, Hadas Ketter; Lustig, Avichai; Lev-Ari, Tidhar; Nov, Yuval; Rivlin, Ehud; Katzir, Gadi
2015-07-01
Chameleons perform large-amplitude eye movements that are frequently referred to as independent, or disconjugate. When prey (an insect) is detected, the chameleon's eyes converge to view it binocularly and 'lock' in their sockets so that subsequent visual tracking is by head movements. However, the extent of the eyes' independence is unclear. For example, can a chameleon visually track two small targets simultaneously and monocularly, i.e. one with each eye? This is of special interest because eye movements in ectotherms and birds are frequently independent, with optic nerves that are fully decussated and intertectal connections that are not as developed as in mammals. Here, we demonstrate that chameleons presented with two small targets moving in opposite directions can perform simultaneous, smooth, monocular, visual tracking. To our knowledge, this is the first demonstration of such a capacity. The fine patterns of the eye movements in monocular tracking were composed of alternating, longer, 'smooth' phases and abrupt 'step' events, similar to smooth pursuits and saccades. Monocular tracking differed significantly from binocular tracking with respect to both 'smooth' phases and 'step' events. We suggest that in chameleons, eye movements are not simply 'independent'. Rather, at the gross level, eye movements are (i) disconjugate during scanning, (ii) conjugate during binocular tracking and (iii) disconjugate, but coordinated, during monocular tracking. At the fine level, eye movements are disconjugate in all cases. These results support the view that in vertebrates, basic monocular control is under a higher level of regulation that dictates the eyes' level of coordination according to context. © 2015. Published by The Company of Biologists Ltd.
Static structure of chameleon dark matter as an explanation of dwarf spheroidal galaxy cores
Chanda, Prolay Krishna; Das, Subinoy
2017-04-01
We propose a novel mechanism that explains the cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as a function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards the Galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of the dark matter cloud; thus, an equilibrium static configuration of the dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the Galactic center. For simple scalar-dark matter interaction and quadratic scalar self-interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond a few kpc away from the Galactic center but at closer distance it becomes lighter and Fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultralight scalar, it is possible to obtain a flattened dark matter density profile towards the Galactic center. In our scenario, the fifth force can be neglected at distance r ≥1 kpc from the Galactic center and dark matter can be simply treated as heavy nonrelativistic particles beyond this distance, thus reproducing the success of CDM at large scales.
Minimal constrained supergravity
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N. Cribiori
2017-01-01
Full Text Available We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.
Aleksić, J; Antonelli, L A; Antoranz, P; Asensio, M; Backes, M; de Almeida, U Barres; Barrio, J A; Bastieri, D; González, J Becerra; Bednarek, W; Berdyugin, A; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Boller, A; Bonnoli, G; Tridon, D Borla; Braun, I; Bretz, T; Cañellas, A; Carmona, E; Carosi, A; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Cossio, L; Covino, S; Dazzi, F; De Angelis, A; De Caneva, G; del Pozo, E De Cea; De Lotto, B; Mendez, C Delgado; Ortega, A Diago; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Eisenacher, D; Elsaesser, D; Ferenc, D; Fonseca, M V; Font, L; Fruck, C; López, R J García; Garczarczyk, M; Garrido, D; Giavitto, G; Godinović, N; Gozzini, S R; Hadasch, D; Häfner, D; Herrero, A; Hildebrand, D; Höhne-Mönch, D; Hose, J; Hrupec, D; Jogler, T; Kellermann, H; Klepser, S; Krähenbühl, T; Krause, J; Kushida, J; La Barbera, A; Lelas, D; Leonardo, E; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Makariev, M; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Moldón, J; Moralejo, A; Munar-Adrover, P; Niedzwiecki, A; Nieto, D; Nilsson, K; Nowak, N; Orito, R; Paiano, S; Paneque, D; Paoletti, R; Pardo, S; Paredes, J M; Partini, S; Perez-Torres, M A; Persic, M; Peruzzo, L; Pilia, M; Pochon, J; Prada, F; Moroni, P G Prada; Prandini, E; Gimenez, I Puerto; Puljak, I; Reichardt, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Rügamer, S; Saggion, A; Saito, K; Saito, T Y; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shayduk, M; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Spiro, S; Stamatescu, V; Stamerra, A; Steinke, B; Storz, J; Strah, N; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Tibolla, O; Torres, D F; Treves, A; Uellenbeck, M; Vankov, H; Vogler, P; Wagner, R M; Weitzel, Q; Zabalza, V; Zandanel, F; Zanin, R; Pfrommer, C; Pinzke, A
2011-01-01
Galaxy clusters are being assembled today in the most energetic phase of hierarchical structure formation which manifests itself in powerful shocks that contribute to a substantial energy density of cosmic rays (CRs). Hence, clusters are expected to be luminous gamma-ray emitters since they also act as energy reservoirs for additional CR sources, such as active galactic nuclei and supernova-driven galactic winds. To detect the gamma-ray emission from CR interactions with the ambient cluster gas, we conducted the deepest to date observational campaign targeting a galaxy cluster at very high-energy gamma-rays and observed the Perseus cluster with the MAGIC Cherenkov telescopes for a total of ~85 hr of effective observing time. This campaign resulted in the detection of the central radio galaxy NGC 1275 at energies E > 100 GeV with a very steep energy spectrum. Here, we restrict our analysis to energies E > 630 GeV and detect no significant gamma-ray excess. This constrains the average CR-to-thermal pressure rat...
Terra-Nova, Filipe; Amit, Hagay; Hartmann, Gelvam A.; Trindade, Ricardo I. F.
2016-09-01
Archaeomagnetic field models cover longer timescales than historical models and may therefore resolve the motion of geomagnetic features on the core-mantle boundary (CMB) in a more meaningful statistical sense. Here we perform a detailed appraisal of archaeomagnetic field models to infer some aspects of the physics of the outer core. We characterize and compare the identification and tracking of reversed flux patches (RFPs) in order to assess the RFPs robustness. We find similar behaviour within a family of models but differences among different families, suggesting that modelling strategy is more influential than data set. Similarities involve recurrent positions of RFPs, but no preferred direction of motion is found. The tracking of normal flux patches shows similar qualitative behaviour confirming that RFPs identification and tracking is not strongly biased by their relative weakness. We also compare the tracking of RFPs with that of the historical field model gufm1 and with seismic anomalies of the lowermost mantle to explore the possibility that RFPs have preferred locations prescribed by lower mantle lateral heterogeneity. The archaeomagnetic field model that most resembles the historical field is interpreted in terms of core dynamics and core-mantle thermal interactions. This model exhibits correlation between RFPs and low seismic shear velocity in co-latitude and a shift in longitude. These results shed light on core processes, in particular we infer toroidal field lines with azimuthal orientation below the CMB and large fluid upwelling structures with a width of about 80° (Africa) and 110° (Pacific) at the top of the core. Finally, similar preferred locations of RFPs in the past 9 and 3 kyr of the same archaeomagnetic field model suggest that a 3 kyr period is sufficiently long to reliably detect mantle control on core dynamics. This allows estimating an upper bound of 220-310 km for the magnetic boundary layer thickness below the CMB.
Chou, Ho-Hsiu; Nguyen, Amanda; Chortos, Alex; To, John W. F.; Lu, Chien; Mei, Jianguo; Kurosawa, Tadanori; Bae, Won-Gyu; Tok, Jeffrey B.-H.; Bao, Zhenan
2015-08-01
Some animals, such as the chameleon and cephalopod, have the remarkable capability to change their skin colour. This unique characteristic has long inspired scientists to develop materials and devices to mimic such a function. However, it requires the complex integration of stretchability, colour-changing and tactile sensing. Here we show an all-solution processed chameleon-inspired stretchable electronic skin (e-skin), in which the e-skin colour can easily be controlled through varying the applied pressure along with the applied pressure duration. As such, the e-skin's colour change can also be in turn utilized to distinguish the pressure applied. The integration of the stretchable, highly tunable resistive pressure sensor and the fully stretchable organic electrochromic device enables the demonstration of a stretchable electrochromically active e-skin with tactile-sensing control. This system will have wide range applications such as interactive wearable devices, artificial prosthetics and smart robots.
Evolution of the Brans-Dicke Parameter in Generalized Chameleon Cosmology
Institute of Scientific and Technical Information of China (English)
Mubasher Jami; D.Momeni
2011-01-01
@@ Motivated by an earlier study of Sahoo and Singh[Mod.Phys.Lett.A 17(2002)2409],we investigate the time dependence of the Brans-Dicke parameter ω(t)for an expanding Universe in the generalized Brans-Dicke Chameleon cosmology,and obtain an explicit dependence of ω(t)in different expansion phases of the Universe.Also,we discuss how the observed accelerated expansion of the observable Universe can be accommodated in the present formalism.%Motivated by an earlier study of Sahoo and Singh [Mod. Phys. Lett. A 17(2002)2409], we investigate the time dependence of the Brans-Dicke parameter ui(t) for an expanding Universe in the generalized Brans-Dicke Chameleon cosmology, and obtain an explicit dependence of uj(t) in different expansion phases of the Universe. Also, we discuss how the observed accelerated expansion of the observable Universe can be accommodated in the present formalism.
Kunze, Kerstin E
2014-01-01
Observational limits on $y$- and $\\mu$-type distortions can constrain properties of magnetic fields in the early universe. For a Gaussian, random, and non-helical field, $\\mu$ and $y$ are calculated a function of the present-day strength of the field, $B_0$, smoothed over a certain Gaussian width, $k_c^{-1}$, and spectral index, $n_B$, defined by $P_B(k)\\propto k^{n_B}$. For $n_B=-2.9$ and $k_c^{-1}=1 {\\rm Mpc}$, the COBE/FIRAS limit on $\\mu$ yields $B_0-2.6$. After decoupling, energy dissipation is due to ambipolar diffusion and decaying MHD turbulence, creating a $y$-type distortion. The distortion is completely dominated by decaying MHD turbulence, and is of order $y\\approx 10^{-7}$ for a few nG field smoothed over the damping scale at the decoupling epoch, $k_{d,dec}\\approx 290 (B_0/1 {\\rm nG})^{-1} {\\rm Mpc}^{-1}$. This contribution is as large as those of the known contributions such as reionization and virialized objects at lower redshifts. The projected PIXIE limit on $y$ would exclude $B_0>1.0$ and 0...
Directory of Open Access Journals (Sweden)
Marco Ceccarelli
2015-03-01
Full Text Available In this paper a conceptual kinematic design of a chameleonlike robot with proper mobility capacity is presented for service applications in space stations as result of design considerations with biomimetic inspiration by looking at chameleons. Requirements and characteristics are discussed with the aim to identify design problems and operation features. A study of feasibility is described through performance evaluation by using simulations for a basic operation characterization.
Rhodopsin-like immunoreactivity in the 'all cone' retina of the chameleon (Chameleo chameleo).
Bennis, Mohamed; Molday, Robert S; Versaux-Botteri, Claudine; Repérant, Jacques; Jeanny, Jean-Claude; McDevitt, David S
2005-05-01
Chameleons (Order, Reptilia: Family, Lacertilia) are unique among vertebrates in being able to make independent eye movements. The organisation of their retina, however, closely ressembles that of other diurnal lizards; based on morphological studies, it is typically described as containing only cone photoreceptors. We show here that a subpopulation of the photoreceptors are immunolabelled by an antibody directed against rhodopsin, suggesting the presence of rods. We conclude that in the nonmammalian retina, rods and cones cannot be exclusively distinguished on purely morphological grounds.
PREPARING OF THE CHAMELEON COATING BY THE ION JET DEPOSITION METHOD
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Jakub Skocdopole
2017-07-01
Full Text Available Preparation of chameleon coatings using an Ionized Jet Deposition (IJD technique is reported in the present paper. IJD is a new flexible method for thin film deposition developed by Noivion, Srl. The chameleon coatings are thin films characterised by a distinct change of their tribological properties according to the external conditions. The deposited films of SiC and TiN materials were examined by the Raman spectroscopy, SEM and XPS. The results of the Raman spectroscopy have proved an amorphous structure of SiC films. The data from XPS on TiN films have shown that the films are heavily oxidized, but also prove that the films are composed of TiN and pure Ti. The SEM provided information about the size of grains and particles constituting the deposited films, which is important for tribological properties of the films. Deposition of the chameleon coating is very complex problem and IJD could be ideal method for preparation of this coating.
Mechanisms of spectral tuning in the RH2 pigments of Tokay gecko and American chameleon
Takenaka, Naomi; Yokoyama, Shozo
2009-01-01
At present, molecular bases of spectral tuning in rhodopsin-like (RH2) pigments are not well understood. Here, we have constructed the RH2 pigments of nocturnal Tokay gecko (Gekko gekko) and diurnal American chameleon (Anolis carolinensis) as well as chimeras between them. The RH2 pigments of the gecko and chameleon reconstituted with 11-cis-retinal had the wavelengths of maximal absorption (λmax’s) of 467 and 496 nm, respectively. Chimeric pigment analyses indicated that 76–86%, 14–24%, and 10% of the spectral difference between them could be explained by amino acid differences in transmembrane (TM) helices I~IV, V~VII, and amino acid interactions between the two segments, respectively. Evolutionary and mutagenesis analyses revealed that the λmax’s of the gecko and chameleon pigments diverged from each other not only by S49A (serine to alanine replacement at residue 49), S49F (serine to phenylalanine), L52M (leucine to methionine), D83N (aspartic acid to asparagine), M86T (methionine to thereonine), and T97A (threonine to alanine) but also by other amino acid replacements that cause minor λmax-shifts individually. PMID:17590287
Anderson, Christopher V
2016-01-04
Stretching elastic tissues and using their recoil to power movement allows organisms to release energy more rapidly than by muscle contraction directly, thus amplifying power output. Chameleons employ such a mechanism to ballistically project their tongue up to two body lengths, achieving power outputs nearly three times greater than those possible via muscle contraction. Additionally, small organisms tend to be capable of greater performance than larger species performing similar movements. To test the hypothesis that small chameleon species outperform larger species during ballistic tongue projection, performance was examined during feeding among 20 chameleon species in nine genera. This revealed that small species project their tongues proportionately further than large species, achieving projection distances of 2.5 body lengths. Furthermore, feedings with peak accelerations of 2,590 m s(-2), or 264 g, and peak power output values of 14,040 W kg(-1) are reported. These values represent the highest accelerations and power outputs reported for any amniote movement, highlighting the previously underestimated performance capability of the family. These findings show that examining movements in smaller animals may expose movements harbouring cryptic power amplification mechanisms and illustrate how varying metabolic demands may help drive morphological evolution.
New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR
Carbone, D; Wijers, R A M J; Swinbank, J D; Rowlinson, A; Broderick, J W; Cendes, Y N; Stewart, A J; Bell, M E; Breton, R P; Corbel, S; Eislöffel, J; Fender, R P; Grießmeier, J M; Hessels, J W T; Jonker, P G; Kramer, M; Law, C J; Miller-Jones, J C A; Pietka, M; Scheers, L H A; Stappers, B W; van Leeuwen, J; Wijnands, R; Zarka, P
2014-01-01
We report on the results of a search for radio transients between 115 and 190\\,MHz with the LOw Frequency ARray (LOFAR). Four different fields have been monitored with observational cadences between 15 minutes and several months. These fields have been chosen among the Medium Deep fields observed by the optical survey PanSTARRS. A total of 15 observing runs were performed giving a total survey area of 2275 deg$^2$. We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transient Pipeline (TraP). No credible radio transient candidate has been detected in our survey; however, it enables us to set upper limits on the surface density of radio transient sources at low radio frequencies, where little is yet known compared to frequencies above 1 GHz. To do this we used two new statistical methods. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the snapshot su...
Menichetti, Lorenzo; Kätterer, Thomas; Leifeld, Jens
2016-05-01
Soil organic carbon (SOC) dynamics result from different interacting processes and controls on spatial scales from sub-aggregate to pedon to the whole ecosystem. These complex dynamics are translated into models as abundant degrees of freedom. This high number of not directly measurable variables and, on the other hand, very limited data at disposal result in equifinality and parameter uncertainty. Carbon radioisotope measurements are a proxy for SOC age both at annual to decadal (bomb peak based) and centennial to millennial timescales (radio decay based), and thus can be used in addition to total organic C for constraining SOC models. By considering this additional information, uncertainties in model structure and parameters may be reduced. To test this hypothesis we studied SOC dynamics and their defining kinetic parameters in the Zürich Organic Fertilization Experiment (ZOFE) experiment, a > 60-year-old controlled cropland experiment in Switzerland, by utilizing SOC and SO14C time series. To represent different processes we applied five model structures, all stemming from a simple mother model (Introductory Carbon Balance Model - ICBM): (I) two decomposing pools, (II) an inert pool added, (III) three decomposing pools, (IV) two decomposing pools with a substrate control feedback on decomposition, (V) as IV but with also an inert pool. These structures were extended to explicitly represent total SOC and 14C pools. The use of different model structures allowed us to explore model structural uncertainty and the impact of 14C on kinetic parameters. We considered parameter uncertainty by calibrating in a formal Bayesian framework. By varying the relative importance of total SOC and SO14C data in the calibration, we could quantify the effect of the information from these two data streams on estimated model parameters. The weighing of the two data streams was crucial for determining model outcomes, and we suggest including it in future modeling efforts whenever SO14C
Kuncarayakti, Hanindyo; Aldering, Greg; Arimoto, Nobuo; Maeda, Keiichi; Morokuma, Tomoki; Pereira, Rui; Usuda, Tomonori; Hashiba, Yasuhito
2013-01-01
Integral field spectroscopy of 11 type-Ib/c supernova explosion sites in nearby galaxies has been obtained using UH88/SNIFS and Gemini-N/GMOS. The use of integral field spectroscopy enables us to obtain both spatial and spectral information of the explosion site, allowing the identification of the parent stellar population of the supernova progenitor star. The spectrum of the parent population provides metallicity determination via strong-line method and age estimation obtained via comparison with simple stellar population (SSP) models. We adopt this information as the metallicity and age of the supernova progenitor, under the assumption that it was coeval with the parent stellar population. The age of the star corresponds to its lifetime, which in turn gives the estimate of its initial mass. With this method we were able to determine both the metallicity and initial (ZAMS) mass of the progenitor stars of the type Ib and Ic supernovae. We found that on average SN Ic explosion sites are more metal-rich and you...
Menci, N.; Merle, A.; Totzauer, M.; Schneider, A.; Grazian, A.; Castellano, M.; Sanchez, N. G.
2017-02-01
We show that the measured abundance of ultra-faint lensed galaxies at z≈ 6 in the Hubble Frontier Fields (HFF) provides stringent constraints on the parameter space of (i) dark matter models based on keV sterile neutrinos; (ii) “fuzzy” wavelike dark matter models, based on Bose–Einstein condensates of ultra-light particles. For the case of sterile neutrinos, we consider two production mechanisms: resonant production through mixing with active neutrinos and the decay of scalar particles. For the former model, we derive constraints for the combination of sterile neutrino mass {m}ν and mixing parameter {\\sin }2(2θ ) which provide the tightest lower bounds on the mixing angle (and hence on the lepton asymmetry) derived so far by methods independent of baryonic physics. For the latter we compute the allowed combinations of the scalar mass, its coupling to the Higgs field, and the Yukawa coupling of scalar to sterile neutrinos. We compare our results to independent existing astrophysical bounds on sterile neutrinos in the same mass range. For the case of “fuzzy” dark matter, we show that the observed number density ≈ 1/{{Mpc}}3 of high-redshift galaxies in the HFF sets a lower limit {m}\\psi ≥slant 8\\cdot {10}-22 eV (at the 3-σ confidence level) on the particle mass, a result that strongly disfavors wavelike bosonic dark matter as a viable model for structure formation. We discuss the impact on our results of uncertainties due to systematics in the selection of highly magnified, faint galaxies at high redshift.
Jardani, A.; Revil, A.; BolèVe, A.; Dupont, J. P.
2008-09-01
We propose an algorithm to invert self-potential signals measured at the ground surface of the Earth to localize hydromechanical disturbances or to the pattern of groundwater flow in geothermal systems. The self-potential signals result from the divergence of the streaming current density. Groundwater flow can be either driven by topography of the water table, free convection, or deformation of the medium. The algorithm includes the electrical resistivity distribution of the medium obtained independently by DC resistance tomography or electromagnetic methods or by coding the assumed geology in terms of distribution of the electrical resistivity accounting for the effect of the temperature and salinity distributions and possibly constraints from borehole measurements. Inversion of the distribution of the source current density from ground surface and borehole self-potential measurements is achieved by solving the inverse problem using Tikhonov regularization solutions that are compatible with the physics of the primary flow problem. By introducing assumptions regarding the smoothness or the compactness of the source and the three-dimensional distribution of the electrical resistivity of the system, the inverse problem can be solved in obtaining the three-dimensional distribution of the current source density in the ground. However, an annihilator can be added to the inverted source geometry without affecting the measured self-potential field. Annihilators can be obtained from boundary conditions. Synthetic models and a sandbox experiment are discussed to demonstrate the validity of the algorithm. An application is presented to the geothermal field of Cerro Prieto, Baja California, Mexico, using literature data. Inversion of the self-potential and resistivity data allows observing a plume of hot groundwater rising to the ground surface in the central part of the investigated area and discharging to the ground surface in the southwest part. The temperature anomaly
Figueira, Adelaine M. e. Silva; Davidson, Eric A.; Nagy, R. Chelsea; Riskin, Shelby H.; Martinelli, Luiz A.
2016-10-01
The impacts of large-scale conversion of cattle pastures to cropland on soil carbon (C) and nitrogen (N) stocks are poorly understood in the Amazon region. The objective of this research was to determine whether soybean cultivation on a previously deforested and pastured soil has changed C and N stocks and dynamics. We sampled a chronosequence of soybean fields in 2009 and again in 2013. We hypothesized that detecting statistically significant changes in total soil C and N stocks would be difficult but that fluxes of C and N through the soil would be sufficiently large to significantly decrease the stable isotope ratios of soil organic matter. We observed statistically significant decreases in the 13C and 15N enrichments and C:N ratio. When combined with estimates of crop biomass production, harvest yield, and biological nitrogen fixation, these measurements provided sufficient constraints for C and N budgets to infer modest rates of net change in soil N (+15 to +27 kg N ha-1 yr-1) and soil C (-0.15 to -0.30 Mg C ha-1 yr-1) in the top 10 cm of soil. These results indicate that this intensive soybean cropping system is having minimal impacts on N loss to the environment but likely is a small net source of C to the atmosphere.
New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR.
Carbone, D; van der Horst, A J; Wijers, R A M J; Swinbank, J D; Rowlinson, A; Broderick, J W; Cendes, Y N; Stewart, A J; Bell, M E; Breton, R P; Corbel, S; Eislöffel, J; Fender, R P; Grießmeier, J-M; Hessels, J W T; Jonker, P; Kramer, M; Law, C J; Miller-Jones, J C A; Pietka, M; Scheers, L H A; Stappers, B W; van Leeuwen, J; Wijnands, R; Wise, M; Zarka, P
2016-07-01
We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 min and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg(2). We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline. No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies. We also show that low-frequency radio surveys are more sensitive to steep-spectrum coherent transient sources than GHz radio surveys. We used two new statistical methods to determine the upper limits on the transient surface density. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the transient surface density. Both of these methods provide better constraints than the approach used in previous works. The best value for the upper limit we can set for the transient surface density, using the method assuming a power-law flux distribution, is 1.3 × 10(-3) deg(-2) for transients brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We also calculated for the first time upper limits for the transient surface density for transients of different time-scales. We find that the results can differ by orders of magnitude from previously reported, simplified estimates.
Le Brocq, A.; Bentley, M.; Hubbard, A.; Fogwill, C.; Sugden, D.
2008-12-01
A numerical ice sheet model constrained by recent field evidence is employed to reconstruct the Last Glacial Maximum (LGM) ice sheet in the Weddell Sea Embayment (WSE). Previous modelling attempts have predicted an extensive grounding line advance (to the continental shelf break) in the WSE, leading to a large equivalent sea level contribution for the sector. The sector has therefore been considered as a potential source for a period of rapid sea level rise (MWP1a, 20 m rise in ~500 years). Recent field evidence suggests that the elevation change in the Ellsworth mountains at the LGM is lower than previously thought (~400 m). The numerical model applied in this paper suggests that a 400 m thicker ice sheet at the LGM does not support such an extensive grounding line advance. A range of ice sheet surfaces, resulting from different grounding line locations, lead to an equivalent sea level estimate of 1 - 3 m for this sector. It is therefore unlikely that the sector made a significant contribution to sea level rise since the LGM, and in particular to MWP1a. The reduced ice sheet size also has implications for the correction of GRACE data, from which Antarctic mass balance calculations have been derived.
Kunze, Kerstin E.; Komatsu, Eiichiro
2014-01-01
Primordial magnetic fields that exist before the photon-baryon decoupling epoch are damped on length scales below the photon diffusion and free-streaming scales. The energy injected into the plasma by dissipation of magnetosonic and Alfv&aposen waves heats photons, creating a y-type distortion of the black-body spectrum of the cosmic microwave background. This y-type distortion is converted into a μ-type distortion when elastic Compton scattering is efficient. Therefore, we can use observational limits on y- and μ-type distortions to constrain properties of magnetic fields in the early universe. Assuming a Gaussian, random, and non-helical field, we calculate μ and y as a function of the present-day strength of the field, B0, smoothed over a certain Gaussian width, kc-1, as well as of the spectral index of the power spectrum of fields, nB, defined by PB(k)proptoknB. For a nearly scale-invariant spectrum with nB = -2.9 and a Gaussian smoothing width of kc-1 = 1Mpc, the existing COBE/FIRAS limit on μ yields B0 FIRAS limit on μ excludes a wide range of spectral indices given by nB > -2.6. After decoupling, energy dissipation is due to ambipolar diffusion and decaying MHD turbulence, creating a y-type distortion. The distortion is completely dominated by decaying MHD turbulence, and is of order y ≈ 10-7 for a few nG field smoothed over the damping scale at the decoupling epoch, kd, dec ≈ 290(B0/1nG)-1Mpc-1. The projected PIXIE limit on y would exclude B0 > 1.0 and 0.6 nG for nB = -2.9 and -2.3, respectively, and B0 > 0.6 nG for nB >= 2. Finally, we find that the current limits on the optical depth to Thomson scattering restrict the predicted y-type distortion to be ylesssim10-8.
Directory of Open Access Journals (Sweden)
Kate D. L. Umbers
2012-09-01
Full Text Available A set of polymorphic loci was characterised using an enrichment library for the Australian alpine specialist, the chameleon grasshopper (Kosciuscola tristis, an atypical grasshopper known for its remarkable temperature-controlled colour change. The number of alleles per locus ranged from three to 20 and observed heterozygosity from 0.16 to 0.76. These are the first microsatellite markers for a non-endangered Australian alpine animal and will inform questions of gene flow across the sky islands of this unique and threatened region.
Umbers, Kate D L; Dennison, Siobhan; Manahan, Czarina A; Blondin, Laurence; Pagés, Christine; Risterucci, Ange-Marie; Chapuis, Marie-Pierre
2012-01-01
A set of polymorphic loci was characterised using an enrichment library for the Australian alpine specialist, the chameleon grasshopper (Kosciuscola tristis), an atypical grasshopper known for its remarkable temperature-controlled colour change. The number of alleles per locus ranged from three to 20 and observed heterozygosity from 0.16 to 0.76. These are the first microsatellite markers for a non-endangered Australian alpine animal and will inform questions of gene flow across the sky islands of this unique and threatened region.
Expanding Horizons with Chameleon: Team Missouri’s Innovative Home Automation System
Directory of Open Access Journals (Sweden)
Bryan Glass
2010-06-01
Full Text Available Team Missouri’s 2009 Solar Decathlon entry featured a revolutionary home automation system, Chameleon, promoting both convenience and energy savings. This was accomplished using the typical controls of a convenience based automation system, while maintaining user set points, such as a home’s ambient temperature, in the most energy efficient manner. Environmental features of the system include controls for home heating, ventilation and air conditioning, lighting, windows, shades, appliances, indoor air quality, as well as indoor and outdoor irrigation. Further analysis and refinement to the prototype system displayed at the competition is also presented in this paper.
Agegraphic Chameleon-Tachyon dark energy model: stability and observational tests
Farajollahi, H.; Tayebi, F.; Feizi, Z.
2012-10-01
In this paper interacting chameleon-tachyon model with agegraphic dark energy is revisited. The model in two cases of matter and radiation dominated universe is best fitted with the observational data for distance modulus. Stability of the model is investigated. The model then tested against observational data for Hubble parameter. With respect to the best fitted model parameters, our results show that while both scenarios are in good match with the observational data in low redshifts, the model in radiation dominated case better fits the data in high redshifts.
Murakami-Ramalho, Elizabeth; Piert, Joyce; Militello, Matthew
2008-01-01
In this article, the authors use their personal narratives and collaborative portraits as methods to shed light on the complexities of developing a research identity while journeying through a doctoral program. Using the metaphors of a wanderer, a chameleon, and a warrior, their narratives represent portraits of experiences faced by doctoral…
Testing game theory models: fighting ability and decision rules in chameleon contests.
Stuart-Fox, Devi
2006-06-22
Game theory models of animal contests make many non-mutually exclusive predictions, complicating empirical tests. These predictions regard the relationship between contest parameters and fighting ability, for which body size is usually used as a proxy. However, in many systems, body size may be a limited proxy since multiple traits and contextual factors such as experience influence fighting ability. Using contests between male Cape dwarf chameleons, Bradypodion pumilum, I test alternative game theory models of extended contests. I show how the most likely candidate model can be identified through a process of elimination, based on tests of key predictions. In addition, I present a measure of fighting ability based on multiple traits that allows ability to change as experience changes. In dwarf chameleons, persistence is based on loser thresholds rather than assessment of relative ability, ruling out the sequential assessment model. Winners and losers do not match behaviours in early parts of the contest, arguing against all types of war of attrition models. Although the cumulative assessment model remained as the most likely candidate model, not all specific predictions of this model were upheld.
Using an InGrid Detector to Search for Solar Chameleons with CAST
Desch, Klaus; Krieger, Christoph; Lupberger, Michael
2015-01-01
We report on the construction, operation experience, and preliminary background measurements of an InGrid detector, i.e. a MicroMegas detector with CMOS pixel readout. The detector was mounted in the focal plane of the Abrixas X-Ray telescope at the CAST experiment at CERN. The detector is sensitive to soft X-Rays in a broad energy range (0.3--10 keV) and thus enables the search for solar chameleons. Smooth detector operation during CAST data taking in autumn 2014 has been achieved. Preliminary analysis of background data indicates a background rate of $1-5\\times 10^{-5}\\,\\mathrm{keV}^{-1}\\mathrm{cm}^{-2}\\mathrm{s}^{-1}$ above 2 keV and $\\sim 3\\times 10^{-4}\\,\\mathrm{keV}^{-1}\\mathrm{cm}^{-2}\\mathrm{s}^{-1}$ around 1 keV. An expected limit of $\\beta_\\gamma \\lesssim 5\\times 10^{10}$ on the chameleon photon coupling is estimated in case of absence of an excess in solar tracking data. We also discuss the prospects for future operation of the detector.
Ligon, Russell A.; McGraw, Kevin J.
2013-01-01
Many animals display static coloration (e.g. of feathers or fur) that can serve as a reliable sexual or social signal, but the communication function of rapidly changing colours (as in chameleons and cephalopods) is poorly understood. We used recently developed photographic and mathematical modelling tools to examine how rapid colour changes of veiled chameleons Chamaeleo calyptratus predict aggressive behaviour during male–male competitions. Males that achieved brighter stripe coloration were more likely to approach their opponent, and those that attained brighter head coloration were more likely to win fights; speed of head colour change was also an important predictor of contest outcome. This correlative study represents the first quantification of rapid colour change using organism-specific visual models and provides evidence that the rate of colour change, in addition to maximum display coloration, can be an important component of communication. Interestingly, the body and head locations of the relevant colour signals map onto the behavioural displays given during specific contest stages, with lateral displays from a distance followed by directed, head-on approaches prior to combat, suggesting that different colour change signals may evolve to communicate different information (motivation and fighting ability, respectively). PMID:24335271
Butler, Michael W; Ligon, Russell A
2015-01-01
Stressors frequently increase oxidative damage--unless organisms simultaneously mount effective antioxidant responses. One putative mitigative mechanism is the use of biliverdin, an antioxidant produced in the spleen during erythrocyte degradation. We hypothesized that both wild and captive-bred male veiled chameleons (Chamaeleo calyptratus), which are highly aggressive to conspecifics, would respond to agonistic displays with increased levels of oxidative damage, but that increased levels of biliverdin would limit this increase. We found that even just visual exposure to a potential combatant resulted in decreased body mass during the subsequent 48-hour period, but that hematocrit, biliverdin concentration in the bile, relative spleen size, and oxidative damage in plasma, liver, and spleen were unaffected. Contrary to our predictions, we found that individuals with smaller spleens exhibited greater decreases in hematocrit and higher bile biliverdin concentrations, suggesting a revision to the idea of spleen-dependent erythrocyte processing. Interestingly, individuals with larger spleens had reduced oxidative damage in both the liver and spleen, demonstrating the spleen's importance in modulating oxidative damage. We also uncovered differences in spleen size and oxidative damage between wild and captive-bred chameleons, highlighting environmentally dependent differences in oxidative physiology. Lastly, we found no relationship between oxidative damage and biliverdin concentration, calling into question biliverdin's antioxidant role in this species.
Age-related changes in the tooth-bone interface area of acrodont dentition in the chameleon.
Dosedělová, Hana; Štěpánková, Kateřina; Zikmund, Tomáš; Lesot, Herve; Kaiser, Jozef; Novotný, Karel; Štembírek, Jan; Knotek, Zdeněk; Zahradníček, Oldřich; Buchtová, Marcela
2016-09-01
Chameleon teeth develop as individual structures at a distance from the developing jaw bone during the pre-hatching period and also partially during the post-hatching period. However, in the adult, all teeth are fused together and tightly attached to the jaw bone by mineralized attachment tissue to form one functional unit. Tooth to bone as well as tooth to tooth attachments are so firm that if injury to the oral cavity occurs, several neighbouring teeth and pieces of jaw can be broken off. We analysed age-related changes in chameleon acrodont dentition, where ankylosis represents a physiological condition, whereas in mammals, ankylosis only occurs in a pathological context. The changes in hard-tissue morphology and mineral composition leading to this fusion were analysed. For this purpose, the lower jaws of chameleons were investigated using X-ray micro-computed tomography, laser-induced breakdown spectroscopy and microprobe analysis. For a long time, the dental pulp cavity remained connected with neighbouring teeth and also to the underlying bone marrow cavity. Then, a progressive filling of the dental pulp cavity by a mineralized matrix occurred, and a complex network of non-mineralized channels remained. The size of these unmineralized channels progressively decreased until they completely disappeared, and the dental pulp cavity was filled by a mineralized matrix over time. Moreover, the distribution of calcium, phosphorus and magnesium showed distinct patterns in the different regions of the tooth-bone interface, with a significant progression of mineralization in dentin as well as in the supporting bone. In conclusion, tooth-bone fusion in chameleons results from an enhanced production of mineralized tissue during post-hatching development. Uncovering the developmental processes underlying these outcomes and performing comparative studies is necessary to better understand physiological ankylosis; for that purpose, the chameleon can serve as a useful model
Simulation tests of galaxy cluster constraints on chameleon gravity
Wilcox, Harry; Zhao, Gong-bo; Bacon, David; Koyama, Kazuya; Romer, A Kathy
2016-01-01
We use two new hydrodynamical simulations of $\\Lambda$CDM and $f(R)$ gravity to test the methodology used by Wilcox et al. 2015 (W15) in constraining the effects of a fifth force on the profiles of clusters of galaxies. We construct realistic simulated stacked weak lensing and X-ray surface brightness cluster profiles from these cosmological simulations, and then use these data projected along various lines-of-sight to test the spherical symmetry of our stacking procedure. We also test the applicability of the NFW profile to model weak lensing profiles of clusters in $f(R)$ gravity. Finally, we test the validity of the analytical model developed in W15 against the simulated profiles. Overall, we find our methodology is robust and broadly agrees with these simulated data. We also apply our full Markov Chain Monte Carlo (MCMC) analysis from W15 to our simulated X-ray and lensing profiles, providing consistent constraints on the modified gravity parameters as obtained from the real cluster data, e.g. for our $\\L...
Simulation tests of galaxy cluster constraints on chameleon gravity
Wilcox, Harry; Nichol, Robert C.; Zhao, Gong-Bo; Bacon, David; Koyama, Kazuya; Romer, A. Kathy
2016-10-01
We use two new hydrodynamical simulations of Λ cold dark matter (ΛCDM) and f(R) gravity to test the methodology used by Wilcox et al. (W15) in constraining the effects of a fifth force on the profiles of clusters of galaxies. We construct realistic simulated stacked weak lensing and X-ray surface brightness cluster profiles from these cosmological simulations, and then use these data projected along various lines of sight to test the spherical symmetry of our stacking procedure. We also test the applicability of the NFW profile to model weak lensing profiles of clusters in f(R) gravity. Finally, we test the validity of the analytical model developed in W15 against the simulated profiles. Overall, we find our methodology is robust and broadly agrees with these simulated data. We also apply our full Markov Chain Monte Carlo analysis from W15 to our simulated X-ray and lensing profiles, providing consistent constraints on the modified gravity parameters as obtained from the real cluster data, e.g. for our ΛCDM simulation we obtain |fR0| < 8.3 × 10-5 (95 per cent CL), which is in good agreement with the W15 measurement of |fR0| < 6 × 10-5. Overall, these tests confirm the power of our methodology which can now be applied to larger cluster samples available with the next generation surveys.
Lightweight cryptography for constrained devices
DEFF Research Database (Denmark)
Alippi, Cesare; Bogdanov, Andrey; Regazzoni, Francesco
2014-01-01
Lightweight cryptography is a rapidly evolving research field that responds to the request for security in resource constrained devices. This need arises from crucial pervasive IT applications, such as those based on RFID tags where cost and energy constraints drastically limit the solution...
Directory of Open Access Journals (Sweden)
S. Kim
2011-03-01
Full Text Available We present OH reactivity measurements using the comparative reactivity method with a branch enclosure technique for four different tree species (red oak, white pine, beech and red maple in the UMBS PROPHET tower footprint during the Community Atmosphere Biosphere INteraction EXperiment (CABINEX field campaign in July of 2009. Proton Transfer Reaction-Mass Spectrometry (PTR-MS was sequentially used as a detector for OH reactivity and BVOC including isoprene and monoterpenes (MT, in enclosure air, so that the measurement dataset contains both measured OH reactivity and calculated OH reactivity from well-known BVOC. The results indicate that isoprene and MT, and in one case a sesquiterpene, can account for the measured OH reactivity. Significant discrepancy between measured OH reactivity and calculated OH reactivity from isoprene and MT is found for the red maple enclosure dataset but it can be reconciled by adding reactivity from emission of a sesquiterpene, α-farnesene, detected by GC-MS. This leads us to conclude that no significant unknown BVOC emission contributed to ambient OH reactivity from these trees at least during the study period. This conclusion leads us to explore the contribution from unmeasured isoprene (the dominant OH sink in this ecosystem oxidation products such as hydroxyacetone, glyoxal, methylglyoxal and C4 and C5-hydroxycarbonyl using recently published isoprene oxidation mechanisms (Mainz Isoprene Mechanism II and Leuven Isoprene Mechanism. Evaluation of conventionally unmeasured first generation oxidation products of isoprene and their possible contribution to ambient missing OH reactivity indicates that the ratio of OH reactivity from unmeasured products over OH reactivity from MVK + MACR is strongly dependent on NO concentrations. The unmeasured oxidation products can contribute ~7.2% (8.8% from LIM and 5.6% by MIM 2 when NO = 100 pptv of the isoprene contribution towards total ambient OH reactivity. This amount can
Limousin, M.; Richard, J.; Jullo, E.; Jauzac, M.; Ebeling, H.; Bonamigo, M.; Alavi, A.; Clément, B.; Giocoli, C.; Kneib, J.-P.; Verdugo, T.; Natarajan, P.; Siana, B.; Atek, H.; Rexroth, M.
2016-04-01
We present a strong-lensing analysis of MACSJ0717.5+3745 (hereafter MACS J0717), based on the full depth of the Hubble Frontier Field (HFF) observations, which brings the number of multiply imaged systems to 61, ten of which have been spectroscopically confirmed. The total number of images comprised in these systems rises to 165, compared to 48 images in 16 systems before the HFF observations. Our analysis uses a parametric mass reconstruction technique, as implemented in the Lenstool software, and the subset of the 132 most secure multiple images to constrain a mass distribution composed of four large-scale mass components (spatially aligned with the four main light concentrations) and a multitude of galaxy-scale perturbers. We find a superposition of cored isothermal mass components to provide a good fit to the observational constraints, resulting in a very shallow mass distribution for the smooth (large-scale) component. Given the implications of such a flat mass profile, we investigate whether a model composed of "peaky" non-cored mass components can also reproduce the observational constraints. We find that such a non-cored mass model reproduces the observational constraints equally well, in the sense that both models give comparable total rms. Although the total (smooth dark matter component plus galaxy-scale perturbers) mass distributions of both models are consistent, as are the integrated two-dimensional mass profiles, we find that the smooth and the galaxy-scale components are very different. We conclude that, even in the HFF era, the generic degeneracy between smooth and galaxy-scale components is not broken, in particular in such a complex galaxy cluster. Consequently, insights into the mass distribution of MACS J0717 remain limited, emphasizing the need for additional probes beyond strong lensing. Our findings also have implications for estimates of the lensing magnification. We show that the amplification difference between the two models is larger
Skin pattern structure and function of juvenile ages of Chameleo chameleon
Directory of Open Access Journals (Sweden)
Yosra A. Fouda
2017-03-01
Full Text Available Little is known about the skin structure of juvenile chameleon especially its sensory function of their integumentary structure. Fifteen juvenile Chameleo chameleon are collected from Abu Rawash, Northern area of Giza, Egypt during Summer of 2015. It is belong to the order Squamata, family, Chamaeleonidae. Three ages are used in the present study and categorized according to the morphological criteria of head, abdomen and limb lengths. Dorsal abdominal surfaces are covered with abdominal scales of varying sizes either conical or elliptical-structures, regularly arranged in rows and imbricated with each other. Each scale possessed one cylindrical lenticular epidermal sense organ containing heavy sensillia. Histologically, the scales are characterized by wider conical surfaces and intermingled with another one by hinge region. The epidermal layer of outer scale surface is composed of five-layered stratified squamous epithelium including the stratum germinativum, intermediate zone of stratum spinosum and granulosum, α-keratin layer, β-keratin layer and outer superficial Oberhaütchen. Melanosomes are abundant in the intermediate zone as well as in the peripheral dermal layer underneath stratum germinativum layer. The melanosomes possessed long cellular processes with their content of melanin granules underneath the epidermis. The dermis is composed of upper collagenous and inner compact layer. Semithin sections revealed the presence of fibroblast cells, collagenous fibrils, nerve axons, melanosomes and mast cells in the connective tissue core. Increased immunoreaction of cytokeratin is observed in the epidermal layers of G3; meanwhile, an increased proliferation of epidermal and dermal cells was detected in G1. Transmission electron microscopy exhibited striking formation of dermal sense organs containing neuronal cells of both oligodendrocytes and Schwann cells with myelinated and unmyelinated nerve axons ensheathed externally by thin
The Chameleon framework : practical solutions for memory behavior analysis
Weinberg, Jonathan
2008-01-01
Though the performance of many applications is dominated by memory behavior, our ability to describe, capture, compare, and recreate that behavior is quite limited. This inability underlies much of the complexity in the field of performance analysis: it is fundamentally difficult to relate benchmarks and applications or use realistic workloads to guide system design and procurement. A concise, observable, and machine-independent characterization of memory behavior is needed. This dissertation...
Energy Technology Data Exchange (ETDEWEB)
Coskun, E. [Northern Illinois Univ., DeKalb, IL (United States). Dept. of Mathematical Sciences; Kwong, M.K. [Argonne National Lab., IL (United States)
1995-09-01
Time-dependent Ginzburg-Landau (TDGL) equations are considered for modeling a thin-film finite size superconductor placed under magnetic field. The problem then leads to the use of so-called natural boundary conditions. Computational domain is partitioned into subdomains and bond variables are used in obtaining the corresponding discrete system of equations. An efficient time-differencing method based on the Forward Euler method is developed. Finally, a variable strength magnetic field resulting in a vortex motion in Type II High {Tc} superconducting films is introduced. The authors tackled the problem using two different state-of-the-art parallel computing tools: BlockComm/Chameleon and PCN. They had access to two high-performance distributed memory supercomputers: the Intel iPSC/860 and IBM SP1. They also tested the codes using, as a parallel computing environment, a cluster of Sun Sparc workstations.
Escalera, J B; Bustamante, P; Martin, A
1994-03-01
An approach to reproduce the solubility profile of a drug in several solvent mixtures showing two solubility maxima is proposed in this work. The solubility of sulphamethoxypyridazine was determined at 25 degrees C in several mixtures of varying polarity (hexane:ethyl acetate, ethyl acetate:ethanol and ethanol:water). Sulphamethoxypyridazine was chosen as a model drug because of its proton-donor and proton-acceptor properties. A plot of the mole fraction of the drug vs the solubility parameter of the solvent mixtures shows two solubility peaks. The two peaks found for sulphamethoxypyridazine demonstrate the chameleonic effect as described by Hoy and suggest that the solute-solvent interaction does not vary uniformly from one mixture to another. The different behaviour of the drug in mixtures of two proton-donor and proton-acceptor solvents (alcohol and water), and in mixtures of one proton acceptor (ethyl acetate) and one proton donor-proton acceptor (ethanol) is rationalized in terms of differences in the proton donor-acceptor ability of the solvent mixtures. An approach based on the acidic and basic partial solubility parameters together with the Hildebrand solubility parameter of the solvent mixtures is developed to reproduce the experimental results quantitatively. The equation predicts the two solubility maxima as found experimentally, and the calculated values closely correspond to the experimental values through the range composition of the solvent mixtures. These results show that the chameleonic effect can be described in a quantitative way in terms of Lewis acid-base interactions; this approach can assist the product formulator to choose the proper solvent mixture for a new drug.
Khannoon, Eraqi R; Endlein, Thomas; Russell, Anthony P; Autumn, Kellar
2014-01-22
The striking morphological convergence of hair-like integumentary derivatives of lizards and arthropods (spiders and insects) demonstrates the importance of such features for enhancing purchase on the locomotor substrate. These pilose structures are responsible for the unique tractive abilities of these groups of animals, enabling them to move with seeming ease on overhanging and inverted surfaces, and to traverse inclined smooth substrates. Three groups of lizards are well known for bearing adhesion-promoting setae on their digits: geckos, anoles and skinks. Similar features are also found on the ventral subdigital and distal caudal skin of chameleons. These have only recently been described in any detail, and structurally and functionally are much less well understood than are the setae of geckos and anoles. The seta-like structures of chameleons are not branched (a characteristic of many geckos), nor do they terminate in spatulate tips (which is characteristic of geckos, anoles and skinks). They are densely packed and have attenuated blunt, globose tips or broad, blade-like shafts that are flattened for much of their length. Using a force transducer, we tested the hypothesis that these structures enhance friction and demonstrate that the pilose skin has a greater frictional coefficient than does the smooth skin of these animals. Our results are consistent with friction being generated as a result of side contact of the integumentary filaments. We discuss the evolutionary and functional implications of these seta-like structures in comparison with those typical of other lizard groups and with the properties of seta-mimicking synthetic structures.
Directory of Open Access Journals (Sweden)
Татьяна Борисовна Шатовская
2015-03-01
Full Text Available In this work results of modified Chameleon algorithm are discussed. Hierarchical multilevel algorithms consist of several stages: building the graph, coarsening, partitioning, recovering. Exploring of clustering quality for different data sets with different combinations of algorithms on different stages of the algorithm is the main aim of the article. And also aim is improving the construction phase through the optimization algorithm of choice k in the building the graph k-nearest neighbors
Modeling the microstructural evolution during constrained sintering
DEFF Research Database (Denmark)
Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.
to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number......A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural response...
Trends in PDE constrained optimization
Benner, Peter; Engell, Sebastian; Griewank, Andreas; Harbrecht, Helmut; Hinze, Michael; Rannacher, Rolf; Ulbrich, Stefan
2014-01-01
Optimization problems subject to constraints governed by partial differential equations (PDEs) are among the most challenging problems in the context of industrial, economical and medical applications. Almost the entire range of problems in this field of research was studied and further explored as part of the Deutsche Forschungsgemeinschaft (DFG) priority program 1253 on “Optimization with Partial Differential Equations” from 2006 to 2013. The investigations were motivated by the fascinating potential applications and challenging mathematical problems that arise in the field of PDE constrained optimization. New analytic and algorithmic paradigms have been developed, implemented and validated in the context of real-world applications. In this special volume, contributions from more than fifteen German universities combine the results of this interdisciplinary program with a focus on applied mathematics. The book is divided into five sections on “Constrained Optimization, Identification and Control”...
Modeling the microstructural evolution during constrained sintering
DEFF Research Database (Denmark)
Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini
2014-01-01
as well as the FEM calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of a sample constrained by a rigid substrate is simulated. The constrained sintering result in a larger number of pores near the substrate, as well as anisotropic sintering shrinkage......A numerical model able to simulate solid state constrained sintering is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress...
Modeling the Microstructural Evolution During Constrained Sintering
DEFF Research Database (Denmark)
Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini
2015-01-01
as well as the FEM calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of a sample constrained by a rigid substrate is simulated. The constrained sintering results in a larger number of pores near the substrate, as well as anisotropic sintering shrinkage......A numerical model able to simulate solid-state constrained sintering is presented. The model couples an existing kinetic Monte Carlo model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress...
Evolutionary constrained optimization
Deb, Kalyanmoy
2015-01-01
This book makes available a self-contained collection of modern research addressing the general constrained optimization problems using evolutionary algorithms. Broadly the topics covered include constraint handling for single and multi-objective optimizations; penalty function based methodology; multi-objective based methodology; new constraint handling mechanism; hybrid methodology; scaling issues in constrained optimization; design of scalable test problems; parameter adaptation in constrained optimization; handling of integer, discrete and mix variables in addition to continuous variables; application of constraint handling techniques to real-world problems; and constrained optimization in dynamic environment. There is also a separate chapter on hybrid optimization, which is gaining lots of popularity nowadays due to its capability of bridging the gap between evolutionary and classical optimization. The material in the book is useful to researchers, novice, and experts alike. The book will also be useful...
Kiriushcheva, N; Kuzmin, S V
2011-01-01
We argue that the field-parametrization dependence of Dirac's procedure, for Hamiltonians with first-class constraints not only preserves covariance in covariant theories, but in non-covariant gauge theories it allows one to find the natural field parametrization in which the Hamiltonian formulation automatically leads to the simplest gauge symmetry.
Goda, Makoto
2017-05-01
The wavelength of the light reflected from iridophores depends on the thickness and the spacing of intracellular reflecting platelets. Here, we show that the rapid color change from blue to red of the chameleon sand tilefish Hoplolatilus chlupatyi is mediated by adrenergic stimulation of a novel type of iridophore in which reflecting platelets are concentrated selectively in the periphery of the cell, near the plasma membrane. The color changes are not only observed in vivo but also in pigment cells of isolated scales which respond to increases in K(+) ion concentrations in 0.5 s and to addition of norepinephrine within 1 s. The norepinephrine effect can be blocked by addition of the alpha-adrenergic antagonist phentolamine. The results suggest that adrenergic stimulation leads to changes in reflecting platelet organization in Hoplolatilus chlupatyi iridophores and represents the major mediator of the rapid color change in this fish in vivo. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Cluster abundance in chameleon f(R) gravity I: toward an accurate halo mass function prediction
Cataneo, Matteo; Rapetti, David; Lombriser, Lucas; Li, Baojiu
2016-12-01
We refine the mass and environment dependent spherical collapse model of chameleon f(R) gravity by calibrating a phenomenological correction inspired by the parameterized post-Friedmann framework against high-resolution N-body simulations. We employ our method to predict the corresponding modified halo mass function, and provide fitting formulas to calculate the enhancement of the f(R) halo abundance with respect to that of General Relativity (GR) within a precision of lesssim 5% from the results obtained in the simulations. Similar accuracy can be achieved for the full f(R) mass function on the condition that the modeling of the reference GR abundance of halos is accurate at the percent level. We use our fits to forecast constraints on the additional scalar degree of freedom of the theory, finding that upper bounds competitive with current Solar System tests are within reach of cluster number count analyses from ongoing and upcoming surveys at much larger scales. Importantly, the flexibility of our method allows also for this to be applied to other scalar-tensor theories characterized by a mass and environment dependent spherical collapse.
Ballistic tongue projection in chameleons maintains high performance at low temperature.
Anderson, Christopher V; Deban, Stephen M
2010-03-23
Environmental temperature impacts the physical activity and ecology of ectothermic animals through its effects on muscle contractile physiology. Sprinting, swimming, and jumping performance of ectotherms decreases by at least 33% over a 10 degrees C drop, accompanied by a similar decline in muscle power. We propose that ballistic movements that are powered by recoil of elastic tissues are less thermally dependent than movements that rely on direct muscular power. We found that an elastically powered movement, ballistic tongue projection in chameleons, maintains high performance over a 20 degrees C range. Peak velocity and power decline by only 10%-19% with a 10 degrees C drop, compared to >42% for nonelastic, muscle-powered tongue retraction. These results indicate that the elastic recoil mechanism circumvents the constraints that low temperature imposes on muscle rate properties and thereby reduces the thermal dependence of tongue projection. We propose that organisms that use elastic recoil mechanisms for ecologically important movements such as feeding and locomotion may benefit from an expanded thermal niche.
Is viscous adhesion strong enough to allow prey capture by chameleons?
Brau, Fabian; Zghikh, Leïla-Nastasia; Bels, Vincent; Damman, Pascal
2014-01-01
Predators can be sorted in two main categories: ambush and active foragers. Most iguanian lizards are ambush predators. They remain motionless waiting for active preys to come within the reach of a strike or approach them very slowly. Among them, chameleons have developed the ultimate specialized feeding systems based on the ballistic projection of the tongue combined with a very efficient adhesion able to sustain the large accelerations involved. The projection mechanisms was intensively studied but the mechanism responsible for the strong adhesion between the prey and the tongue remains controversial. Three different mechanisms are proposed in the literature: i) wet or Stefan adhesion where the adhesion strength relies on viscous flow in the thin film of fluid between the tongue and the prey surface; ii) interlocking where the roughness of both prey and tongue surfaces self-adjust to make physical crosslinks as in the hook-and-loop design of Velcro; iii) suction mechanism similar to the one at play in rubbe...
Cluster abundance in chameleon $f(R)$ gravity I: toward an accurate halo mass function prediction
Cataneo, Matteo; Lombriser, Lucas; Li, Baojiu
2016-01-01
We refine the mass and environment dependent spherical collapse model of chameleon $f(R)$ gravity by calibrating a phenomenological correction inspired by the parameterized post-Friedmann framework against high-resolution $N$-body simulations. We employ our method to predict the corresponding modified halo mass function, and provide fitting formulas to calculate the fractional enhancement of the $f(R)$ halo abundance with respect to that of General Relativity (GR) within a precision of $\\lesssim 5\\%$ from the results obtained in the simulations. Similar accuracy can be achieved for the full $f(R)$ mass function on the condition that the modeling of the reference GR abundance of halos is accurate at the percent level. We use our fits to forecast constraints on the additional scalar degree of freedom of the theory, finding that upper bounds competitive with current Solar System tests are within reach of cluster number count analyses from ongoing and upcoming surveys at much larger scales. Importantly, the flexi...
Pratley, Luke; Dehghan, Siamak; Sun, Ming
2013-01-01
We present a multi-wavelength study of the radio galaxy PKS J0334-3900 at the centre of Abell 3135. The spectro-polarimetric radio observations are combined with spectroscopic optical and X-ray data to illustrate the use of Head-Tail radio galaxies to reveal properties of the intracluster medium. ATCA observations at 1.4, 2.5, 4.6 & 8.6 GHz are presented with a detailed analysis of the morphology and spectral indices giving physical parameters to constrain the dynamical history of the galaxy. Using these constraints we produce a simulation of PKS J0334-3900. We find that this Head-Tail morphology can be induced via a combination of orbital motion due to a binary companion and relative motion through the ICM. New Chandra images of A3135 are presented from which we obtain a cluster electron density of n_(e,0) = (1.06 +/- 0.11 x 10^(-3) cm^(-3), a global temperature of 2.4 ^(+0.51)_(-0.38) keV and a lower limit to the radio jet power of PKS J0334-3900 of 1.6 x 10^(44) erg/s. A new redshift analysis of the cl...
Exploring constrained quantum control landscapes
Moore, Katharine W.; Rabitz, Herschel
2012-10-01
The broad success of optimally controlling quantum systems with external fields has been attributed to the favorable topology of the underlying control landscape, where the landscape is the physical observable as a function of the controls. The control landscape can be shown to contain no suboptimal trapping extrema upon satisfaction of reasonable physical assumptions, but this topological analysis does not hold when significant constraints are placed on the control resources. This work employs simulations to explore the topology and features of the control landscape for pure-state population transfer with a constrained class of control fields. The fields are parameterized in terms of a set of uniformly spaced spectral frequencies, with the associated phases acting as the controls. This restricted family of fields provides a simple illustration for assessing the impact of constraints upon seeking optimal control. Optimization results reveal that the minimum number of phase controls necessary to assure a high yield in the target state has a special dependence on the number of accessible energy levels in the quantum system, revealed from an analysis of the first- and second-order variation of the yield with respect to the controls. When an insufficient number of controls and/or a weak control fluence are employed, trapping extrema and saddle points are observed on the landscape. When the control resources are sufficiently flexible, solutions producing the globally maximal yield are found to form connected "level sets" of continuously variable control fields that preserve the yield. These optimal yield level sets are found to shrink to isolated points on the top of the landscape as the control field fluence is decreased, and further reduction of the fluence turns these points into suboptimal trapping extrema on the landscape. Although constrained control fields can come in many forms beyond the cases explored here, the behavior found in this paper is illustrative of
Directory of Open Access Journals (Sweden)
Mohd Fuad Miskon
2015-06-01
Full Text Available Pb, Cd, Cu and Zn in the soft tissue of Nerita chameleon from particular rocky shore sites along the east coast of Peninsular Malaysia were investigated. Samples were measured using ICP-MS with standard configuration. The metal accumulation patterns indicate consistent enrichment of essential metals. Locations with relatively high concentrations of the contaminant metals Pb, Cd and Cu are related to their close proximity to industrial activities and urban sites. Comparison with maximum permissible limits of toxic metals in food indicated the values were well within safety levels.
Choosing health, constrained choices.
Chee Khoon Chan
2009-12-01
In parallel with the neo-liberal retrenchment of the welfarist state, an increasing emphasis on the responsibility of individuals in managing their own affairs and their well-being has been evident. In the health arena for instance, this was a major theme permeating the UK government's White Paper Choosing Health: Making Healthy Choices Easier (2004), which appealed to an ethos of autonomy and self-actualization through activity and consumption which merited esteem. As a counterpoint to this growing trend of informed responsibilization, constrained choices (constrained agency) provides a useful framework for a judicious balance and sense of proportion between an individual behavioural focus and a focus on societal, systemic, and structural determinants of health and well-being. Constrained choices is also a conceptual bridge between responsibilization and population health which could be further developed within an integrative biosocial perspective one might refer to as the social ecology of health and disease.
Institute of Scientific and Technical Information of China (English)
WANG Min; ZHANG Peizhen; SHEN Zhengkang; LIU Jie; SUN Hanrong; GAN Weijun; LI Peng
2006-01-01
Based on continuous GPS observations within China as well as global GPS tracking network,a calculation has been made of far-field coseismic displacements associated with the December, 2004 (Mw= 9.3) and March, 2005 (Mw= 8.7) earthquakes.The far-field coseismic displacements are associated with the 2004 shock range more than 6000-7000 krn in both north-south and east-west dimensions,and depict an undulated wave pattern of contraction and extension. The coseismic displacements associated with the 2005 event, however, are distributed near the epicentral region, and the event itself may be an aftershock of the 2004 earthquake.
Constrained optimization using CODEQ
Energy Technology Data Exchange (ETDEWEB)
Omran, Mahamed G.H. [Department of Computer Science, Gulf University for Science and Technology, P.O. Box 7207, Hawally 32093 (Kuwait)], E-mail: omran.m@gust.edu.kw; Salman, Ayed [Computer Engineering Department, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait)], E-mail: ayed@eng.kuniv.edu.kw
2009-10-30
Many real-world optimization problems are constrained problems that involve equality and inequality constraints. CODEQ is a new, parameter-free meta-heuristic algorithm that is a hybrid of concepts from chaotic search, opposition-based learning, differential evolution and quantum mechanics. The performance of the proposed approach when applied to five constrained benchmark problems is investigated and compared with other approaches proposed in the literature. The experiments conducted show that CODEQ provides excellent results with the added advantage of no parameter tuning.
Energy Technology Data Exchange (ETDEWEB)
Rose, P.T.S.; Manighetti, A.A. [Texaco Ltd., Aberdeen (United Kingdom); Regan, K.J.; Smith, T. [STAG Geological Services Ltd., Aldermaston, Reading (United Kingdom)
2000-08-01
The Captain Field is a large viscous oil accumulation located in the Western Moray Firth. UK Block 13/22a which is being developed by long horizontal wells. The reservoir sand body geometry was defined in the appraisal phase by 20 vertical wells. Seismic attributes were not used because of the poor seismic signal to noise ratio in the reservoir interval. As the development drilling campaign has unfolded, the appraisal sand body geometry model has been significantly refined using a wealth of data from the horizontal wells. During development it has proved cheap to sidetrack horizontal well sections without a requirement to isolate the abandoned hole. This has resulted in significant extra geological data (e.g. top reservoir penetrations, sand thickness data). Integrating this dataset with top reservoir topography derived from seismic and weak internal reservoir seismic reflectors, the sand body geometry model is significantly improved in underdeveloped parts of the field. (Author)
Constrained superfields in supergravity
Energy Technology Data Exchange (ETDEWEB)
Dall’Agata, Gianguido; Farakos, Fotis [Dipartimento di Fisica ed Astronomia “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy)
2016-02-16
We analyze constrained superfields in supergravity. We investigate the consistency and solve all known constraints, presenting a new class that may have interesting applications in the construction of inflationary models. We provide the superspace Lagrangians for minimal supergravity models based on them and write the corresponding theories in component form using a simplifying gauge for the goldstino couplings.
Energy Technology Data Exchange (ETDEWEB)
Kuncarayakti, Hanindyo; Maeda, Keiichi [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Doi, Mamoru; Morokuma, Tomoki; Hashiba, Yasuhito [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Aldering, Greg [Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Arimoto, Nobuo [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Pereira, Rui [CNRS/IN2P3, Institut de Physique Nucleaire de Lyon, 4 Rue Enrico Fermi, F-69622 Villeurbanne Cedex (France); Usuda, Tomonori, E-mail: hanindyo.kuncarayakti@ipmu.jp [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A' ohoku Place, Hilo, HI 96720 (United States)
2013-08-01
Integral field spectroscopy of 11 Type Ib/Ic supernova (SN Ib/Ic) explosion sites in nearby galaxies has been obtained using UH88/SNIFS and Gemini-N/GMOS. The use of integral field spectroscopy enables us to obtain both spatial and spectral information about the explosion site, enabling the identification of the parent stellar population of the SN progenitor star. The spectrum of the parent population provides metallicity determination via strong-line method and age estimation obtained via comparison with simple stellar population models. We adopt this information as the metallicity and age of the SN progenitor, under the assumption that it was coeval with the parent stellar population. The age of the star corresponds to its lifetime, which in turn gives the estimate of its initial mass. With this method we were able to determine both the metallicity and initial (zero-age main sequence) mass of the progenitor stars of SNe Ib and Ic. We found that on average SN Ic explosion sites are more metal-rich and younger than SN Ib sites. The initial mass of the progenitors derived from parent stellar population age suggests that SN Ic has more massive progenitors than SN Ib. In addition, we also found indication that some of our SN progenitors are less massive than {approx}25 M{sub Sun }, indicating that they may have been stars in a close binary system that have lost their outer envelope via binary interactions to produce SNe Ib/Ic, instead of single Wolf-Rayet stars. These findings support the current suggestions that both binary and single progenitor channels are in effect in producing SNe Ib/Ic. This work also demonstrates the power of integral field spectroscopy in investigating SN environments and active star-forming regions.
Directory of Open Access Journals (Sweden)
Emilia eKomulainen
2014-09-01
Full Text Available Genetic anomalies on the JNK pathway confer susceptibility to autism spectrum disorders, schizophrenia and intellectual disability. The mechanism whereby a gain or loss of function in JNK signaling predisposes to these prevalent dendrite disorders, with associated motor dysfunction, remains unclear. Here we find that JNK1 regulates the dendritic field of L2/3 and L5 pyramidal neurons of the mouse motor cortex (M1, the main excitatory pathway controlling voluntary movement. In Jnk1-/- mice, basal dendrite branching of L5 pyramidal neurons is increased in M1, as is cell soma size, whereas in L2/3, dendritic arborization is decreased. We show that JNK1 phosphorylates rat HMW-MAP2 on T1619, T1622 and T1625 (Uniprot P15146 corresponding to mouse T1617, T1620, T1623, to create a binding motif, that is critical for MAP2 interaction with and stabilization of microtubules, and dendrite growth control. Targeted expression in M1 of GFP-HMW-MAP2 that is pseudo-phosphorylated on T1619, T1622 and T1625 increases dendrite complexity in L2/3 indicating that JNK1 phosphorylation of HMW-MAP2 regulates the dendritic field. Consistent with the morphological changes observed in L2/3 and L5, Jnk1-/- mice exhibit deficits in limb placement and motor coordination, while stride length is reduced in older animals. In summary, JNK1 phosphorylates HMW-MAP2 to increase its stabilization of microtubules while at the same time controlling dendritic fields in the main excitatory pathway of M1. Moreover, JNK1 contributes to normal functioning of fine motor coordination. We report for the first time, a quantitative sholl analysis of dendrite architecture, and of motor behavior in Jnk1-/- mice. Our results illustrate the molecular and behavioral consequences of interrupted JNK1 signaling and provide new ground for mechanistic understanding of those prevalent neuropyschiatric disorders where genetic disruption of the JNK pathway is central.
Kuncarayakti, Hanindyo; Aldering, Greg; Arimoto, Nobuo; Maeda, Keiichi; Morokuma, Tomoki; Pereira, Rui; Usuda, Tomonori; Hashiba, Yasuhito
2013-01-01
Thirteen explosion sites of type II-P and II-L supernovae in nearby galaxies have been observed using integral field spectroscopy, enabling both spatial and spectral study of the explosion sites. We used the properties of the parent stellar population of the coeval supernova progenitor star to derive its metallicity and initial mass (c.f. Paper I). The spectrum of the parent stellar population yields the estimates of metallicity via strong-line method, and age via comparison with simple stellar population (SSP) models. These metallicity and age parameters are adopted for the progenitor star. Age, or lifetime of the star, was used to derive initial (ZAMS) mass of the star by comparing with stellar evolution models. With this technique, we were able to determine metallicity and initial mass of the SN progenitors in our sample. Our result indicates that some type-II supernova progenitors may have been stars with mass comparable to SN Ib/c progenitors.
van Griensven, Johan; De Weiggheleire, Anja; Delamou, Alexandre; Smith, Peter G.; Edwards, Tansy; Vandekerckhove, Philippe; Bah, Elhadj Ibrahima; Colebunders, Robert; Herve, Isola; Lazaygues, Catherine; Haba, Nyankoye; Lynen, Lutgarde
2016-01-01
The clinical evaluation of convalescent plasma (CP) for the treatment of Ebola virus disease (EVD) in the current outbreak, predominantly affecting Guinea, Sierra Leone, and Liberia, was prioritized by the World Health Organization in September 2014. In each of these countries, nonrandomized comparative clinical trials were initiated. The Ebola-Tx trial in Conakry, Guinea, enrolled 102 patients by 7 July 2015; no severe adverse reactions were noted. The Ebola-CP trial in Sierra Leone and the EVD001 trial in Liberia have included few patients. Although no efficacy data are available yet, current field experience supports the safety, acceptability, and feasibility of CP as EVD treatment. Longer-term follow-up as well as data from nontrial settings and evidence on the scalability of the intervention are required. CP sourced from within the outbreak is the most readily available source of anti-EVD antibodies. Until the advent of effective antivirals or monoclonal antibodies, CP merits further evaluation. PMID:26261205
Sharp spatially constrained inversion
DEFF Research Database (Denmark)
Vignoli, Giulio G.; Fiandaca, Gianluca G.; Christiansen, Anders Vest C A.V.C.;
2013-01-01
We present sharp reconstruction of multi-layer models using a spatially constrained inversion with minimum gradient support regularization. In particular, its application to airborne electromagnetic data is discussed. Airborne surveys produce extremely large datasets, traditionally inverted...... by using smoothly varying 1D models. Smoothness is a result of the regularization constraints applied to address the inversion ill-posedness. The standard Occam-type regularized multi-layer inversion produces results where boundaries between layers are smeared. The sharp regularization overcomes......, the results are compatible with the data and, at the same time, favor sharp transitions. The focusing strategy can also be used to constrain the 1D solutions laterally, guaranteeing that lateral sharp transitions are retrieved without losing resolution. By means of real and synthetic datasets, sharp...
Hurier, G.
2017-08-01
The Sunyaev-Zel'dovich (SZ) effects are produced by the interaction of cosmic microwave background (CMB) photons with the ionized and diffuse gas of electrons inside galaxy clusters integrated along the line of sight. The two main effects are the thermal SZ (tSZ) produced by thermal pressure inside galaxy clusters and the kinematic SZ (kSZ) produced by peculiar motion of galaxy clusters compared to CMB rest-frame. The kSZ effect is particularly challenging to measure as it follows the same spectral behavior as the CMB, and consequently cannot be separated from the CMB using spectral considerations. In this paper, we explore the feasibility of detecting the kSZ through the computation of the tSZ-CMB-CMB cross-correlation bispectrum for current and future CMB experiments. We conclude that the next generation of CMB experiments will offer the possibility to detect the tSZ-kSZ-kSZ bispectrum at high signal-to-noise ration (S/N). This measurement will constraints the intra-cluster dynamics and the velocity field of galaxy cluster that is extremely sensitive to the growth rate of structures and thus to dark energy properties. Additionally, we also demonstrate that the tSZ-kSZ-kSZ bispectrum can be used to break the degeneracies between the mass-observable relation and the cosmological parameters to set tight constraints, up to 4%, on the Y - M relation calibration.
Energy Technology Data Exchange (ETDEWEB)
Capella, Antonio [Instituto de Matematicas, Universidad Nacional Autonoma de Mexico (Mexico); Mueller, Stefan [Hausdorff Center for Mathematics and Institute for Applied Mathematics, Universitaet Bonn (Germany); Otto, Felix [Max Planck Institute for Mathematics in the Sciences, Leipzig (Germany)
2012-08-15
A mathematical description of transformation processes in magnetic shape memory alloys (MSMA) under applied stresses and external magnetic fields needs a combination of micromagnetics and continuum elasticity theory. In this note, we discuss the so-called constrained theories, i.e., models where the state described by the pair (linear strain, magnetization) is at every point of the sample constrained to assume one of only finitely many values (that reflect the material symmetries). Furthermore, we focus on large body limits, i.e., models that are formulated in terms of (local) averages of a microstructured state, as the one proposed by DeSimone and James. We argue that the effect of an interfacial energy associated with the twin boundaries survives on the level of the large body limit in form of a (local) rigidity of twins. This leads to an alternative (i.e., with respect to reference 1) large body limit. The new model has the advantage of qualitatively explaining the occurrence of a microstructure with charged magnetic walls, as observed in SPP experiments in reference 2. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter Scenarios
Jenke, T; Burgdörfer, J; Chizhova, L A; Geltenbort, P; Ivanov, A N; Lauer, T; Lins, T; Rotter, S; Saul, H; Schmidt, U; Abele, H
2014-01-01
We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of the Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate, that Newton's inverse square law of Gravity is understood at micron distances on an energy scale of~$10^{-14}$~eV. At this level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant~$\\beta > 5.8\\times10^8$ at~95% confidence level~(C.L.), and an attractive (repulsive) dark matter axion-like spin-mass coupling is excluded for the coupling strength $g_sg_p > 3.7\\times10^{-16}$~($5.3\\times10^{-16}$)~at a Yukawa length of~$\\lambda = 20$~{\\textmu}m~(95% (C.L.).
Urns and Chameleons: two metaphors for two different types of measurements
Accardi, Luigi
2013-09-01
-existent properties" (urn metaphor) and measurements consisting in reading "a response to an interaction" (chameleon metaphor). The non-trivial point is that one can prove that, while the urn scheme cannot lead to empirical data outside of classic probability, response based measurements can give rise to non classical statistics. The talk will include entirely classical examples of non classical statistics and potential applications to economic, sociological or biomedical phenomena.
Lectures on Constrained Systems
Date, Ghanashyam
2010-01-01
These lecture notes were prepared as a basic introduction to the theory of constrained systems which is how the fundamental forces of nature appear in their Hamiltonian formulation. Only a working knowledge of Lagrangian and Hamiltonian formulation of mechanics is assumed. These notes are based on the set of eight lectures given at the {\\em Refresher Course for College Teachers} held at IMSc during May-June, 2005. These are submitted to the arxiv for an easy access to a wider body of students.
Constraining entropic cosmology
Energy Technology Data Exchange (ETDEWEB)
Koivisto, Tomi S. [Institute for Theoretical Physics and the Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands); Mota, David F. [Institute of Theoretical Astrophysics, University of Oslo, 0315 Oslo (Norway); Zumalacárregui, Miguel, E-mail: t.s.koivisto@uu.nl, E-mail: d.f.mota@astro.uio.no, E-mail: miguelzuma@icc.ub.edu [Institute of Cosmos Sciences (ICC-IEEC), University of Barcelona, Marti i Franques 1, E-08028 Barcelona (Spain)
2011-02-01
It has been recently proposed that the interpretation of gravity as an emergent, entropic phenomenon might have nontrivial implications to cosmology. Here several such approaches are investigated and the underlying assumptions that must be made in order to constrain them by the BBN, SneIa, BAO and CMB data are clarified. Present models of inflation or dark energy are ruled out by the data. Constraints are derived on phenomenological parameterizations of modified Friedmann equations and some features of entropic scenarios regarding the growth of perturbations, the no-go theorem for entropic inflation and the possible violation of the Bekenstein bound for the entropy of the Universe are discussed and clarified.
Symmetrically Constrained Compositions
Beck, Matthias; Lee, Sunyoung; Savage, Carla D
2009-01-01
Given integers $a_1, a_2, ..., a_n$, with $a_1 + a_2 + ... + a_n \\geq 1$, a symmetrically constrained composition $\\lambda_1 + lambda_2 + ... + lambda_n = M$ of $M$ into $n$ nonnegative parts is one that satisfies each of the the $n!$ constraints ${\\sum_{i=1}^n a_i \\lambda_{\\pi(i)} \\geq 0 : \\pi \\in S_n}$. We show how to compute the generating function of these compositions, combining methods from partition theory, permutation statistics, and lattice-point enumeration.
Space Constrained Dynamic Covering
Antonellis, Ioannis; Dughmi, Shaddin
2009-01-01
In this paper, we identify a fundamental algorithmic problem that we term space-constrained dynamic covering (SCDC), arising in many modern-day web applications, including ad-serving and online recommendation systems in eBay and Netflix. Roughly speaking, SCDC applies two restrictions to the well-studied Max-Coverage problem: Given an integer k, X={1,2,...,n} and I={S_1, ..., S_m}, S_i a subset of X, find a subset J of I, such that |J| <= k and the union of S in J is as large as possible. The two restrictions applied by SCDC are: (1) Dynamic: At query-time, we are given a query Q, a subset of X, and our goal is to find J such that the intersection of Q with the union of S in J is as large as possible; (2) Space-constrained: We don't have enough space to store (and process) the entire input; specifically, we have o(mn), sometimes even as little as O((m+n)polylog(mn)) space. The goal of SCDC is to maintain a small data structure so as to answer most dynamic queries with high accuracy. We present algorithms a...
Directory of Open Access Journals (Sweden)
Frank Glaw
Full Text Available BACKGROUND: One clade of Malagasy leaf chameleons, the Brookesia minima group, is known to contain species that rank among the smallest amniotes in the world. We report on a previously unrecognized radiation of these miniaturized lizards comprising four new species described herein. METHODOLOGY/PRINCIPAL FINDINGS: The newly discovered species appear to be restricted to single, mostly karstic, localities in extreme northern Madagascar: Brookesia confidens sp. n. from Ankarana, B. desperata sp. n. from Forêt d'Ambre, B. micra sp. n. from the islet Nosy Hara, and B. tristis sp. n. from Montagne des Français. Molecular phylogenetic analyses based on one mitochondrial and two nuclear genes of all nominal species in the B. minima group congruently support that the four new species, together with B. tuberculata from Montagne d'Ambre in northern Madagascar, form a strongly supported clade. This suggests that these species have diversified in geographical proximity in this small area. All species of the B. minima group, including the four newly described ones, are characterized by very deep genetic divergences of 18-32% in the ND2 gene and >6% in the 16S rRNA gene. Despite superficial similarities among all species of this group, their status as separate evolutionary lineages is also supported by moderate to strong differences in external morphology, and by clear differences in hemipenis structure. CONCLUSION/SIGNIFICANCE: The newly discovered dwarf chameleon species represent striking cases of miniaturization and microendemism and suggest the possibility of a range size-body size relationship in Malagasy reptiles. The newly described Brookesia micra reaches a maximum snout-vent length in males of 16 mm, and its total length in both sexes is less than 30 mm, ranking it among the smallest amniote vertebrates in the world. With a distribution limited to a very small islet, this species may represent an extreme case of island dwarfism.
Constraining symmetron fields with atom interferometry
Burrage, Clare; Stevenson, James; Thrussell, Ben
2016-01-01
We apply the new constraints from atom-interferometry searches for screening mechanisms to the symmetron model, finding that these experiments exclude a previously unexplored region of parameter space. We discuss the possibility of networks of domain walls forming in the vacuum chamber, and how this could be used to discriminate between models of screening.
Oberacker, V E
2015-01-01
In this manuscript we provide an outline of the numerical methods used in implementing the density constrained time-dependent Hartree-Fock (DC-TDHF) method and provide a few examples of its application to nuclear fusion. In this approach, dynamic microscopic calculations are carried out on a three-dimensional lattice and there are no adjustable parameters, the only input is the Skyrme effective NN interaction. After a review of the DC-TDHF theory and the numerical methods, we present results for heavy-ion potentials $V(R)$, coordinate-dependent mass parameters $M(R)$, and precompound excitation energies $E^{*}(R)$ for a variety of heavy-ion reactions. Using fusion barrier penetrabilities, we calculate total fusion cross sections $\\sigma(E_\\mathrm{c.m.})$ for reactions between both stable and neutron-rich nuclei. We also determine capture cross sections for hot fusion reactions leading to the formation of superheavy elements.
Constrained Sparse Galerkin Regression
Loiseau, Jean-Christophe
2016-01-01
In this work, we demonstrate the use of sparse regression techniques from machine learning to identify nonlinear low-order models of a fluid system purely from measurement data. In particular, we extend the sparse identification of nonlinear dynamics (SINDy) algorithm to enforce physical constraints in the regression, leading to energy conservation. The resulting models are closely related to Galerkin projection models, but the present method does not require the use of a full-order or high-fidelity Navier-Stokes solver to project onto basis modes. Instead, the most parsimonious nonlinear model is determined that is consistent with observed measurement data and satisfies necessary constraints. The constrained Galerkin regression algorithm is implemented on the fluid flow past a circular cylinder, demonstrating the ability to accurately construct models from data.
Constrained space camera assembly
Heckendorn, Frank M.; Anderson, Erin K.; Robinson, Casandra W.; Haynes, Harriet B.
1999-01-01
A constrained space camera assembly which is intended to be lowered through a hole into a tank, a borehole or another cavity. The assembly includes a generally cylindrical chamber comprising a head and a body and a wiring-carrying conduit extending from the chamber. Means are included in the chamber for rotating the body about the head without breaking an airtight seal formed therebetween. The assembly may be pressurized and accompanied with a pressure sensing means for sensing if a breach has occurred in the assembly. In one embodiment, two cameras, separated from their respective lenses, are installed on a mounting apparatus disposed in the chamber. The mounting apparatus includes means allowing both longitudinal and lateral movement of the cameras. Moving the cameras longitudinally focuses the cameras, and moving the cameras laterally away from one another effectively converges the cameras so that close objects can be viewed. The assembly further includes means for moving lenses of different magnification forward of the cameras.
Verde, Licia; Pigozzo, Cassio; Heavens, Alan F; Jimenez, Raul
2016-01-01
We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the $\\Lambda$CDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95\\% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter $\\Omega_{\\rm MR} < 0.006$ and extra radiation parameterised as extra effective neutrino species $2.3 < N_{\\rm eff} < 3.2$ when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond $\\Lambda$CDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way ...
Distance-constrained grid colouring
Directory of Open Access Journals (Sweden)
Aszalós László
2016-06-01
Full Text Available Distance-constrained colouring is a mathematical model of the frequency assignment problem. This colouring can be treated as an optimization problem so we can use the toolbar of the optimization to solve concrete problems. In this paper, we show performance of distance-constrained grid colouring for two methods which are good in map colouring.
Quantizing Constrained Systems New Perspectives
Kaplan, L; Heller, E J
1997-01-01
We consider quantum mechanics on constrained surfaces which have non-Euclidean metrics and variable Gaussian curvature. The old controversy about the ambiguities involving terms in the Hamiltonian of order hbar^2 multiplying the Gaussian curvature is addressed. We set out to clarify the matter by considering constraints to be the limits of large restoring forces as the constraint coordinates deviate from their constrained values. We find additional ambiguous terms of order hbar^2 involving freedom in the constraining potentials, demonstrating that the classical constrained Hamiltonian or Lagrangian cannot uniquely specify the quantization: the ambiguity of directly quantizing a constrained system is inherently unresolvable. However, there is never any problem with a physical quantum system, which cannot have infinite constraint forces and always fluctuates around the mean constraint values. The issue is addressed from the perspectives of adiabatic approximations in quantum mechanics, Feynman path integrals, a...
Power-constrained supercomputing
Bailey, Peter E.
As we approach exascale systems, power is turning from an optimization goal to a critical operating constraint. With power bounds imposed by both stakeholders and the limitations of existing infrastructure, achieving practical exascale computing will therefore rely on optimizing performance subject to a power constraint. However, this requirement should not add to the burden of application developers; optimizing the runtime environment given restricted power will primarily be the job of high-performance system software. In this dissertation, we explore this area and develop new techniques that extract maximum performance subject to a particular power constraint. These techniques include a method to find theoretical optimal performance, a runtime system that shifts power in real time to improve performance, and a node-level prediction model for selecting power-efficient operating points. We use a linear programming (LP) formulation to optimize application schedules under various power constraints, where a schedule consists of a DVFS state and number of OpenMP threads for each section of computation between consecutive message passing events. We also provide a more flexible mixed integer-linear (ILP) formulation and show that the resulting schedules closely match schedules from the LP formulation. Across four applications, we use our LP-derived upper bounds to show that current approaches trail optimal, power-constrained performance by up to 41%. This demonstrates limitations of current systems, and our LP formulation provides future optimization approaches with a quantitative optimization target. We also introduce Conductor, a run-time system that intelligently distributes available power to nodes and cores to improve performance. The key techniques used are configuration space exploration and adaptive power balancing. Configuration exploration dynamically selects the optimal thread concurrency level and DVFS state subject to a hardware-enforced power bound
Williams, Brian; Hudson, Nicolas; Tweddle, Brent; Brockers, Roland; Matthies, Larry
2011-01-01
A Feature and Pose Constrained Extended Kalman Filter (FPC-EKF) is developed for highly dynamic computationally constrained micro aerial vehicles. Vehicle localization is achieved using only a low performance inertial measurement unit and a single camera. The FPC-EKF framework augments the vehicle's state with both previous vehicle poses and critical environmental features, including vertical edges. This filter framework efficiently incorporates measurements from hundreds of opportunistic visual features to constrain the motion estimate, while allowing navigating and sustained tracking with respect to a few persistent features. In addition, vertical features in the environment are opportunistically used to provide global attitude references. Accurate pose estimation is demonstrated on a sequence including fast traversing, where visual features enter and exit the field-of-view quickly, as well as hover and ingress maneuvers where drift free navigation is achieved with respect to the environment.
Constrained inflaton due to a complex scalar
Energy Technology Data Exchange (ETDEWEB)
Budhi, Romy H. S. [Physics Department, Gadjah Mada University,Yogyakarta 55281 (Indonesia); Institute for Theoretical Physics, Kanazawa University,Kanazawa 920-1192 (Japan); Kashiwase, Shoichi; Suematsu, Daijiro [Institute for Theoretical Physics, Kanazawa University,Kanazawa 920-1192 (Japan)
2015-09-14
We reexamine inflation due to a constrained inflaton in the model of a complex scalar. Inflaton evolves along a spiral-like valley of special scalar potential in the scalar field space just like single field inflation. Sub-Planckian inflaton can induce sufficient e-foldings because of a long slow-roll path. In a special limit, the scalar spectral index and the tensor-to-scalar ratio has equivalent expressions to the inflation with monomial potential φ{sup n}. The favorable values for them could be obtained by varying parameters in the potential. This model could be embedded in a certain radiative neutrino mass model.
Constraining Curvatonic Reheating
Hardwick, Robert J; Koyama, Kazuya; Wands, David
2016-01-01
We derive the first systematic observational constraints on reheating in models of inflation where an additional light scalar field contributes to primordial density perturbations and affects the expansion history during reheating. This encompasses the original curvaton model but also covers a larger class of scenarios. We find that, compared to the single-field case, lower values of the energy density at the end of inflation and of the reheating temperature are preferred when an additional scalar field is introduced. For instance, if inflation is driven by a quartic potential, which is one of the most favoured models when a light scalar field is added, the upper bound $T_{\\mathrm{reh}}<5\\times 10^{4}\\,\\mathrm{GeV}$ on the reheating temperature $T_{\\mathrm{reh}}$ is derived, and the implications of this value on post-inflationary physics are discussed. The information gained about reheating is also quantified and it is found that it remains modest in plateau inflation (though still larger than in the singl...
Constrained simulation of the Bullet Cluster
Energy Technology Data Exchange (ETDEWEB)
Lage, Craig; Farrar, Glennys, E-mail: csl336@nyu.edu [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)
2014-06-01
In this work, we report on a detailed simulation of the Bullet Cluster (1E0657-56) merger, including magnetohydrodynamics, plasma cooling, and adaptive mesh refinement. We constrain the simulation with data from gravitational lensing reconstructions and the 0.5-2 keV Chandra X-ray flux map, then compare the resulting model to higher energy X-ray fluxes, the extracted plasma temperature map, Sunyaev-Zel'dovich effect measurements, and cluster halo radio emission. We constrain the initial conditions by minimizing the chi-squared figure of merit between the full two-dimensional (2D) observational data sets and the simulation, rather than comparing only a few features such as the location of subcluster centroids, as in previous studies. A simple initial configuration of two triaxial clusters with Navarro-Frenk-White dark matter profiles and physically reasonable plasma profiles gives a good fit to the current observational morphology and X-ray emissions of the merging clusters. There is no need for unconventional physics or extreme infall velocities. The study gives insight into the astrophysical processes at play during a galaxy cluster merger, and constrains the strength and coherence length of the magnetic fields. The techniques developed here to create realistic, stable, triaxial clusters, and to utilize the totality of the 2D image data, will be applicable to future simulation studies of other merging clusters. This approach of constrained simulation, when applied to well-measured systems, should be a powerful complement to present tools for understanding X-ray clusters and their magnetic fields, and the processes governing their formation.
A dark energy model with higher derivatives of H in the framework of Chameleon Brans-Dicke Cosmology
Pasqua, Antonio
2016-01-01
In this paper, we study some relevant cosmological features of a Dark Energy (DE) model which is function of the Hubble parameter $H$ and its first and second time derivatives in the framework of Chameleon Brans-Dicke (BD) Cosmology. Choosing a particular ansatz for some of the quantities involved, we derive the expressions of some important cosmological quantities, like the Equation of State (EoS) parameter of DE $w_D$, the effective EoS parameter $w_{eff}$, the pressure of DE $p_D$ and the deceleration parameter $q$. Moreover, we study the behavior of statefinder parameters $r$ and $s$, of the cosmographic parameters $j$, $s_{cosmo}$, $l$ and $m$ and of the squared speed of the sound $v_s^2$ for both case corresponding to non interacting and interacting Dark Sectors. We also plot the quantities we have derived and we calculate their values for $t\\rightarrow 0$ (i.e. for the beginning of the Universe history), for $t\\rightarrow \\infty$ (i.e. for far future) and for the present time, indicated with $t_0$.
Propulsion Physics Under the Changing Density Field Model
Robertson, Glen A.
2011-01-01
To grow as a space faring race, future spaceflight systems will requires new propulsion physics. Specifically a propulsion physics model that does not require mass ejection without limiting the high thrust necessary to accelerate within or beyond our solar system and return within a normal work period or lifetime. In 2004 Khoury and Weltman produced a density dependent cosmology theory they called Chameleon Cosmology, as at its nature, it is hidden within known physics. This theory represents a scalar field within and about an object, even in the vacuum. Whereby, these scalar fields can be viewed as vacuum energy fields with definable densities that permeate all matter; having implications to dark matter/energy with universe acceleration properties; implying a new force mechanism for propulsion physics. Using Chameleon Cosmology, the author has developed a new propulsion physics model, called the Changing Density Field (CDF) Model. This model relates to density changes in these density fields, where the density field density changes are related to the acceleration of matter within an object. These density changes in turn change how an object couples to the surrounding density fields. Whereby, thrust is achieved by causing a differential in the coupling to these density fields about an object. Since the model indicates that the density of the density field in an object can be changed by internal mass acceleration, even without exhausting mass, the CDF model implies a new propellant-less propulsion physics model
Constrained multi-degree reduction with respect to Jacobi norms
Ait-Haddou, Rachid
2015-12-31
We show that a weighted least squares approximation of Bézier coefficients with factored Hahn weights provides the best constrained polynomial degree reduction with respect to the Jacobi L2L2-norm. This result affords generalizations to many previous findings in the field of polynomial degree reduction. A solution method to the constrained multi-degree reduction with respect to the Jacobi L2L2-norm is presented.
Geometric constrained variational calculus. II: The second variation (Part I)
Massa, Enrico; Bruno, Danilo; Luria, Gianvittorio; Pagani, Enrico
2016-10-01
Within the geometrical framework developed in [Geometric constrained variational calculus. I: Piecewise smooth extremals, Int. J. Geom. Methods Mod. Phys. 12 (2015) 1550061], the problem of minimality for constrained calculus of variations is analyzed among the class of differentiable curves. A fully covariant representation of the second variation of the action functional, based on a suitable gauge transformation of the Lagrangian, is explicitly worked out. Both necessary and sufficient conditions for minimality are proved, and reinterpreted in terms of Jacobi fields.
Algorithms for degree-constrained Euclidean Steiner minimal tree
Institute of Scientific and Technical Information of China (English)
Zhang Jin; Ma Liang; Zhang Liantang
2008-01-01
A new problem of degree-constrained Euclidean Steiner minimal tree is discussed,which is quite useful in several fields.Although it is slightly different from the traditional degree-constrained minimal spanning tree,it is aho NP-hard.Two intelligent algorithms are proposed in an attempt to solve this difficult problem.Series of numerical examples are tested,which demonstrate that the algorithms also work well in practice.
Constrained and joint inversion on unstructured meshes
Doetsch, J.; Jordi, C.; Rieckh, V.; Guenther, T.; Schmelzbach, C.
2015-12-01
Unstructured meshes allow for inclusion of arbitrary surface topography, complex acquisition geometry and undulating geological interfaces in the inversion of geophysical data. This flexibility opens new opportunities for coupling different geophysical and hydrological data sets in constrained and joint inversions. For example, incorporating geological interfaces that have been derived from high-resolution geophysical data (e.g., ground penetrating radar) can add geological constraints to inversions of electrical resistivity data. These constraints can be critical for a hydrogeological interpretation of the inversion results. For time-lapse inversions of geophysical data, constraints can be derived from hydrological point measurements in boreholes, but it is difficult to include these hard constraints in the inversion of electrical resistivity monitoring data. Especially mesh density and the regularization footprint around the hydrological point measurements are important for an improved inversion compared to the unconstrained case. With the help of synthetic and field examples, we analyze how regularization and coupling operators should be chosen for time-lapse inversions constrained by point measurements and for joint inversions of geophysical data in order to take full advantage of the flexibility of unstructured meshes. For the case of constraining to point measurements, it is important to choose a regularization operator that extends beyond the neighboring cells and the uncertainty in the point measurements needs to be accounted for. For joint inversion, the choice of the regularization depends on the expected subsurface heterogeneity and the cell size of the parameter mesh.
Cosmicflows Constrained Local UniversE Simulations
Sorce, Jenny G; Yepes, Gustavo; Hoffman, Yehuda; Courtois, Helene M; Steinmetz, Matthias; Tully, R Brent; Pomarede, Daniel; Carlesi, Edoardo
2015-01-01
This paper combines observational datasets and cosmological simulations to generate realistic numerical replicas of the nearby Universe. These latter are excellent laboratories for studies of the non-linear process of structure formation in our neighborhood. With measurements of radial peculiar velocities in the Local Universe (cosmicflows-2) and a newly developed technique, we produce Constrained Local UniversE Simulations (CLUES). To assess the quality of these constrained simulations, we compare them with random simulations as well as with local observations. The cosmic variance, defined as the mean one-sigma scatter of cell-to-cell comparison between two fields, is significantly smaller for the constrained simulations than for the random simulations. Within the inner part of the box where most of the constraints are, the scatter is smaller by a factor 2 to 3 on a 5 Mpc/h scale with respect to that found for random simulations. This one-sigma scatter obtained when comparing the simulated and the observatio...
Non-rigid registration by geometry-constrained diffusion
DEFF Research Database (Denmark)
Andresen, Per Rønsholt; Nielsen, Mads
1999-01-01
are not given. We will advocate the viewpoint that the aperture and the 3D interpolation problem may be solved simultaneously by finding the simplest displacement field. This is obtained by a geometry-constrained diffusion which yields the simplest displacement field in a precise sense. The point registration...
2005-11-01
aeolian dynamics and sand mixing in the Gran Desierto : Evidence from Landsat Thematic Mapper images. Journal of Geophysical Research, 95: 15463–15482...Blount, G., Smith, M.O., Adams, J.B., Greeley, R., and Christensen, P.R. (1990) Regional aeolian dynamics and sand mixing in the Gran Desierto : Evidence
Directory of Open Access Journals (Sweden)
Tammy Keren-Rotem
Full Text Available Alternative mating tactics in males of various taxa are associated with body color, body size, and social status. Chameleons are known for their ability to change body color following immediate environmental or social stimuli. In this study, we examined whether the differential appearance of male common chameleon during the breeding season is indeed an expression of alternative mating tactics. We documented body color of males and used computer vision techniques to classify images of individuals into discrete color patterns associated with seasons, individual characteristics, and social contexts. Our findings revealed no differences in body color and color patterns among males during the non-breeding season. However, during the breeding season males appeared in several color displays, which reflected body size, social status, and behavioral patterns. Furthermore, smaller and younger males resembled the appearance of small females. Consequently, we suggest that long-term color change in males during the breeding season reflects male alternative mating tactics. Upon encounter with a receptive female, males rapidly alter their appearance to that of a specific brief courtship display, which reflects their social status. The females, however, copulated indiscriminately in respect to male color patterns. Thus, we suggest that the differential color patterns displayed by males during the breeding season are largely aimed at inter-male signaling.
Constrained Optimization of Discontinuous Systems
Y.M. Ermoliev; V.I. Norkin
1996-01-01
In this paper we extend the results of Ermoliev, Norkin and Wets [8] and Ermoliev and Norkin [7] to the case of constrained discontinuous optimization problems. In contrast to [7] the attention is concentrated on the proof of general optimality conditions for problems with nonconvex feasible sets. Easily implementable random search technique is proposed.
Constrained Inversion of Enceladus Interaction Observations
Herbert, Floyd; Khurana, K. K.
2007-10-01
Many detailed and sophisticated ab initio calculations of the electrodynamic interaction of Enceladus' plume with Saturn's corotating magnetospheric plasma flow have been computed. So far, however, all such calculations have been forward models, that assume the properties of the plume and compute perturbations to the magnetic (and in some cases, flow velocity) field. As a complement to the forward calculations, work reported here explores the inverse approach, of using simplified physical models of the interaction for computationally inverting the observed magnetic field perturbations of the interaction, in order to determine the cross-B-field conductivity distribution near Enceladus, and from that, the neutral gas distribution. Direct inversion of magnetic field observations to current systems is, of course, impossible, but adding the additional constraint of the interaction physics greatly reduces the non-uniqueness of the computed result. This approach was successfully used by Herbert (JGR 90:8241, 1985) to constrain the atmospheric distribution on Io and the Io torus mass density at the time of the Voyager encounter. Work so far has derived the expected result that there is a cone-shaped region of enhanced cross-field conductivity south of Enceladus, through which currents are driven by the motional electric field. That is, near Enceladus' south pole the cross-field currents are localized, but more widely spread at greater distance. This cross-field conductivity is presumably both pickup and collisional (Pedersen and Hall). Due to enforcement of current conservation, Alfven-wing-like currents north of the main part of the interaction region seem to close partly around Enceladus (assumed insulating) and also to continue northward with attenuated intensity, as though there were a tenuous global exosphere on Enceladus providing additional cross-field conductivity. FH thanks the NASA Outer Planets Research, Planetary Atmospheres, and Geospace Science Programs for
Constrained Multiobjective Biogeography Optimization Algorithm
Directory of Open Access Journals (Sweden)
Hongwei Mo
2014-01-01
Full Text Available Multiobjective optimization involves minimizing or maximizing multiple objective functions subject to a set of constraints. In this study, a novel constrained multiobjective biogeography optimization algorithm (CMBOA is proposed. It is the first biogeography optimization algorithm for constrained multiobjective optimization. In CMBOA, a disturbance migration operator is designed to generate diverse feasible individuals in order to promote the diversity of individuals on Pareto front. Infeasible individuals nearby feasible region are evolved to feasibility by recombining with their nearest nondominated feasible individuals. The convergence of CMBOA is proved by using probability theory. The performance of CMBOA is evaluated on a set of 6 benchmark problems and experimental results show that the CMBOA performs better than or similar to the classical NSGA-II and IS-MOEA.
Constrained multiobjective biogeography optimization algorithm.
Mo, Hongwei; Xu, Zhidan; Xu, Lifang; Wu, Zhou; Ma, Haiping
2014-01-01
Multiobjective optimization involves minimizing or maximizing multiple objective functions subject to a set of constraints. In this study, a novel constrained multiobjective biogeography optimization algorithm (CMBOA) is proposed. It is the first biogeography optimization algorithm for constrained multiobjective optimization. In CMBOA, a disturbance migration operator is designed to generate diverse feasible individuals in order to promote the diversity of individuals on Pareto front. Infeasible individuals nearby feasible region are evolved to feasibility by recombining with their nearest nondominated feasible individuals. The convergence of CMBOA is proved by using probability theory. The performance of CMBOA is evaluated on a set of 6 benchmark problems and experimental results show that the CMBOA performs better than or similar to the classical NSGA-II and IS-MOEA.
TAXATION AND FINANCE CONSTRAINED FIRMS
Iris Claus
2006-01-01
This paper develops an open economy model to assess the long-run effects of taxation where firms are finance constrained. Finance constraints arise because of imperfect information between borrowers and lenders. Only borowers (firms) can costlessly observe actual returns from production. Imperfect information and finance constraints magnify the effects of taxation. A reduction (rise) in income taxation increases (lowers) firms' internal funds and their ability to assess external finance to ex...
Impulsive differential inclusions with constrains
Directory of Open Access Journals (Sweden)
Tzanko Donchev
2006-05-01
Full Text Available In the paper, we study weak invariance of differential inclusions with non-fixed time impulses under compactness type assumptions. When the right-hand side is one sided Lipschitz an extension of the well known relaxation theorem is proved. In this case also necessary and sufficient condition for strong invariance of upper semi continuous systems are obtained. Some properties of the solution set of impulsive system (without constrains in appropriate topology are investigated.
Applications of a Constrained Mechanics Methodology in Economics
Janova, Jitka
2011-01-01
This paper presents instructive interdisciplinary applications of constrained mechanics calculus in economics on a level appropriate for undergraduate physics education. The aim of the paper is (i) to meet the demand for illustrative examples suitable for presenting the background of the highly expanding research field of econophysics even at the…
Constraining the Braking Indices of Magnetars
Gao, Z F; Wang, N; Yuan, J P; Peng, Q H; Du, Y J
2015-01-01
Due to the lack of long term pulsed emission in quiescence and the strong timing noise, it is impossible to directly measure the braking index $n$ of a magnetar. Based on the estimated ages of their potentially associated supernova remnants (SNRs), we estimate the values of $n$ of nine magnetars with SNRs, and find that they cluster in a range of $1\\sim$41. Six magnetars have smaller braking indices of $13$ for other three magnetars are attributed to the decay of external braking torque, which might be caused by magnetic field decay. We estimate the possible wind luminosities for the magnetars with $13$ within the updated magneto-thermal evolution models. We point out that there could be some connections between the magnetar's anti-glitch event and its braking index, and the magnitude of $n$ should be taken into account when explaining the event. Although the constrained range of the magnetars' braking indices is tentative, our method provides an effective way to constrain the magnetars' braking indices if th...
Lifetime of the solar nebula constrained by meteorite paleomagnetism
Wang, Huapei; Weiss, Benjamin P.; Bai, Xue-Ning; Downey, Brynna G.; Wang, Jun; Wang, Jiajun; Suavet, Clément; Fu, Roger R.; Zucolotto, Maria E.
2017-02-01
A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation.
Constraining the dark side with observations
Energy Technology Data Exchange (ETDEWEB)
Diez-Tejedor, Alberto [Dpto. de Fisica Teorica, Universidad del PaIs Vasco, Apdo. 644, 48080, Bilbao (Spain)
2007-05-15
The main purpose of this talk is to use the observational evidences pointing out to the existence of a dark side in the universe in order to infer some of the properties of the unseen material. We will work within the Unified Dark Matter models, in which both, Dark Matter and Dark Energy appear as the result of one unknown component. By modeling effectively this component with a classical scalar field minimally coupled to gravity, we will use the observations to constrain the form of the dark action. Using the flat rotation curves of spiral galaxies we will see that we are restringed to the use of purely kinetic actions, previously studied in cosmology by Scherrer. Finally we arrive to a simple action which fits both cosmological and astrophysical observations.
Constraining cosmology with pairwise velocity estimator
Ma, Yin-Zhe; He, Ping
2015-01-01
In this paper, we develop a full statistical method for the pairwise velocity estimator previously proposed, and apply Cosmicflows-2 catalogue to this method to constrain cosmology. We first calculate the covariance matrix for line-of-sight velocities for a given catalogue, and then simulate the mock full-sky surveys from it, and then calculate the variance for the pairwise velocity field. By applying the $8315$ independent galaxy samples and compressed $5224$ group samples from Cosmicflows-2 catalogue to this statistical method, we find that the joint constraint on $\\Omega^{0.6}_{\\rm m}h$ and $\\sigma_{8}$ is completely consistent with the WMAP 9-year and Planck 2015 best-fitting cosmology. Currently, there is no evidence for the modified gravity models or any dynamic dark energy models from this practice, and the error-bars need to be reduced in order to provide any concrete evidence against/to support $\\Lambda$CDM cosmology.
Constraining the Anisotropic Expansion of Universe
Cai, Rong-Gen; Tang, Bo; Tuo, Zhong-Liang
2013-01-01
We study the possibly existing anisotropy in the accelerating expansion Universe with the Union2 Type Ia supernovae data and Gamma-ray burst data. We construct a direction-dependent dark energy model and constrain the anisotropy direction and strength of modulation. We find that the maximum anisotropic deviation direction is $(l,\\,b)=(126^{\\circ},\\,13^{\\circ})$ (or equivalently $(l,\\,b)=(306^{\\circ},\\,-13^{\\circ})$), and the anisotropy level is $g_0=0.030_{+0.010}^{-0.030}$ (obtained using Union2 data, at $1\\sigma$ confidence level). Our results do not show strong evidence for the anisotropic dark energy model. We also discuss potential methods that may distinguish the peculiar velocity field from the anisotropic dark energy model.
On Constrained Facility Location Problems
Institute of Scientific and Technical Information of China (English)
Wei-Lin Li; Peng Zhang; Da-Ming Zhu
2008-01-01
Given m facilities each with an opening cost, n demands, and distance between every demand and facility,the Facility Location problem finds a solution which opens some facilities to connect every demand to an opened facility such that the total cost of the solution is minimized. The k-Facility Location problem further requires that the number of opened facilities is at most k, where k is a parameter given in the instance of the problem. We consider the Facility Location problems satisfying that for every demand the ratio of the longest distance to facilities and the shortest distance to facilities is at most w, where w is a predefined constant. Using the local search approach with scaling technique and error control technique, for any arbitrarily small constant ∈ > 0, we give a polynomial-time approximation algorithm for the ω-constrained Facility Location problem with approximation ratio 1 + √ω + 1 + ∈, which significantly improves the previous best known ratio (ω + 1)/α for some 1 ≤α≤ 2, and a polynomial-time approximation algorithm for the ω-constrained κ-Facility Location problem with approximation ratio ω + 1 + ∈. On the aspect of approximation hardness, we prove that unless NP (C) DTIME(nO(loglogn)), the ω-constrained Facility Location problem cannot be approximated within 1 + √ω-1,which slightly improves the previous best known hardness result 1.243 + 0.316 ln(ω - 1). The experimental results on the standard test instances of Facility Location problem show that our algorithm also has good performance in practice.
Constrained Stochastic Extended Redundancy Analysis.
DeSarbo, Wayne S; Hwang, Heungsun; Stadler Blank, Ashley; Kappe, Eelco
2015-06-01
We devise a new statistical methodology called constrained stochastic extended redundancy analysis (CSERA) to examine the comparative impact of various conceptual factors, or drivers, as well as the specific predictor variables that contribute to each driver on designated dependent variable(s). The technical details of the proposed methodology, the maximum likelihood estimation algorithm, and model selection heuristics are discussed. A sports marketing consumer psychology application is provided in a Major League Baseball (MLB) context where the effects of six conceptual drivers of game attendance and their defining predictor variables are estimated. Results compare favorably to those obtained using traditional extended redundancy analysis (ERA).
Enablers and constrainers to participation
DEFF Research Database (Denmark)
Desjardins, Richard; Milana, Marcella
2007-01-01
with constraining and enabling elements so as to raise participation among otherwise disadvantaged groups. To begin addressing this question, consideration is given to different types of constraints and different types of policies. These are brought together within a broad demand and supply framework, so...... as to construct a tool for analyzing the targeting of adult learning policy, with regard to both its coverage and expected consequences. Our aim is to develop a means for a more in-depth analysis of the match-mismatch of public policy and persisting constraints to participation....
Constraining Lorentz violation with cosmology.
Zuntz, J A; Ferreira, P G; Zlosnik, T G
2008-12-31
The Einstein-aether theory provides a simple, dynamical mechanism for breaking Lorentz invariance. It does so within a generally covariant context and may emerge from quantum effects in more fundamental theories. The theory leads to a preferred frame and can have distinct experimental signatures. In this Letter, we perform a comprehensive study of the cosmological effects of the Einstein-aether theory and use observational data to constrain it. Allied to previously determined consistency and experimental constraints, we find that an Einstein-aether universe can fit experimental data over a wide range of its parameter space, but requires a specific rescaling of the other cosmological densities.
Constrained and regularized system identification
Directory of Open Access Journals (Sweden)
Tor A. Johansen
1998-04-01
Full Text Available Prior knowledge can be introduced into system identification problems in terms of constraints on the parameter space, or regularizing penalty functions in a prediction error criterion. The contribution of this work is mainly an extension of the well known FPE (Final Production Error statistic to the case when the system identification problem is constrained and contains a regularization penalty. The FPECR statistic (Final Production Error with Constraints and Regularization is of potential interest as a criterion for selection of both regularization parameters and structural parameters such as order.
Method of constrained global optimization
Energy Technology Data Exchange (ETDEWEB)
Altschuler, E.L.; Williams, T.J.; Ratner, E.R.; Dowla, F.; Wooten, F. (Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States) Department of Applied Physics, Stanford University, Stanford, California 94305 (United States) Department of Applied Science, University of California, Davis/Livermore, P.O. Box 808, Livermore, California 94551 (United States))
1994-04-25
We present a new method for optimization: constrained global optimization (CGO). CGO iteratively uses a Glauber spin flip probability and the Metropolis algorithm. The spin flip probability allows changing only the values of variables contributing excessively to the function to be minimized. We illustrate CGO with two problems---Thomson's problem of finding the minimum-energy configuration of unit charges on a spherical surface, and a problem of assigning offices---for which CGO finds better minima than other methods. We think CGO will apply to a wide class of optimization problems.
Constrained Local UniversE Simulations: A Local Group Factory
Carlesi, Edoardo; Hoffman, Yehuda; Gottlöber, Stefan; Yepes, Gustavo; Libeskind, Noam I; Pilipenko, Sergey V; Knebe, Alexander; Courtois, Helene; Tully, R Brent; Steinmetz, Matthias
2016-01-01
Near field cosmology is practiced by studying the Local Group (LG) and its neighbourhood. The present paper describes a framework for simulating the near field on the computer. Assuming the LCDM model as a prior and applying the Bayesian tools of the Wiener filter (WF) and constrained realizations of Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities, constrained simulations of our cosmic environment are performed. The aim of these simulations is to reproduce the LG and its local environment. Our main result is that the LG is likely a robust outcome of the LCDM scenario when subjected to the constraint derived from CF2 data, emerging in an environment akin to the observed one. Three levels of criteria are used to define the simulated LGs. At the base level, pairs of halos must obey specific isolation, mass and separation criteria. At the second level the orbital angular momentum and energy are constrained and on the third one the phase of the orbit is constrained. Out of the 300 constrai...
Pathophysiology of type 2 diabetes mellitus in youth: the evolving chameleon
Tfayli, Hala; Arslanian, Silva
2010-01-01
Type 2 diabetes mellitus (T2DM) in children and adolescents is an important Public Health problem against the backdrop of the epidemic of childhood obesity. The clinical presentation of T2DM in youth is heterogeneous from minimal symptomatology to diabetic ketoacidosis. The increasing rates of youth T2DM have paralleled the escalating rates of obesity, which is the major risk factor impacting insulin sensitivity. Additional risk factors include minority race, family history of diabetes mellitus, maternal diabetes during pregnancy, pubertal age group and conditions associated with insulin resistance (IR) – such as polycystic ovary syndrome (PCOS). The pathophysiology of T2DM has been studied extensively in adults, and it is widely accepted that IR together with beta-cell failure are necessary for the development of clinical diabetes mellitus in adulthood. However, pathophysiologic studies in youth are limited and in some cases conflicting. Similar to adults, IR is a prerequisite, but beta-cell failure is necessary for progression from normal glucose tolerance to prediabetes and frank diabetes in youth. Even though rates of T2DM in youth are increasing, the overall prevalence remains low if compared with type 1 diabetes mellitus (T1DM). However, as youth with T1DM are becoming obese, the clinical distinction between T2DM and obese T1DM has become difficult, because of the overlapping clinical picture with evidence of islet cell autoimmunity in a significant proportion of clinically diagnosed youth with T2DM. The latter are most likely obese children with autoimmune T1DM who carry a misdiagnosis of T2DM. Further research is needed to probe the pathophysiological, immunological, and metabolic differences between these two groups in the hopes of assigning appropriate therapeutic regimens. These challenges combined with the evolving picture of youth T2DM and its future complications provide unending opportunities for acquisition of new knowledge in the field of
Constrained Allocation Flux Balance Analysis
Mori, Matteo; Martin, Olivier C; De Martino, Andrea; Marinari, Enzo
2016-01-01
New experimental results on bacterial growth inspire a novel top-down approach to study cell metabolism, combining mass balance and proteomic constraints to extend and complement Flux Balance Analysis. We introduce here Constrained Allocation Flux Balance Analysis, CAFBA, in which the biosynthetic costs associated to growth are accounted for in an effective way through a single additional genome-wide constraint. Its roots lie in the experimentally observed pattern of proteome allocation for metabolic functions, allowing to bridge regulation and metabolism in a transparent way under the principle of growth-rate maximization. We provide a simple method to solve CAFBA efficiently and propose an "ensemble averaging" procedure to account for unknown protein costs. Applying this approach to modeling E. coli metabolism, we find that, as the growth rate increases, CAFBA solutions cross over from respiratory, growth-yield maximizing states (preferred at slow growth) to fermentative states with carbon overflow (preferr...
Bagging constrained equity premium predictors
DEFF Research Database (Denmark)
Hillebrand, Eric; Lee, Tae-Hwy; Medeiros, Marcelo
2014-01-01
The literature on excess return prediction has considered a wide array of estimation schemes, among them unrestricted and restricted regression coefficients. We consider bootstrap aggregation (bagging) to smooth parameter restrictions. Two types of restrictions are considered: positivity of the r......The literature on excess return prediction has considered a wide array of estimation schemes, among them unrestricted and restricted regression coefficients. We consider bootstrap aggregation (bagging) to smooth parameter restrictions. Two types of restrictions are considered: positivity...... of the regression coefficient and positivity of the forecast. Bagging constrained estimators can have smaller asymptotic mean-squared prediction errors than forecasts from a restricted model without bagging. Monte Carlo simulations show that forecast gains can be achieved in realistic sample sizes for the stock...
Constrained Transport vs. Divergence Cleanser Options in Astrophysical MHD Simulations
Lindner, Christopher C.; Fragile, P.
2009-01-01
In previous work, we presented results from global numerical simulations of the evolution of black hole accretion disks using the Cosmos++ GRMHD code. In those simulations we solved the magnetic induction equation using an advection-split form, which is known not to satisfy the divergence-free constraint. To minimize the build-up of divergence error, we used a hyperbolic cleanser function that simultaneously damped the error and propagated it off the grid. We have since found that this method produces qualitatively and quantitatively different behavior in high magnetic field regions than results published by other research groups, particularly in the evacuated funnels of black-hole accretion disks where Poynting-flux jets are reported to form. The main difference between our earlier work and that of our competitors is their use of constrained-transport schemes to preserve a divergence-free magnetic field. Therefore, to study these differences directly, we have implemented a constrained transport scheme into Cosmos++. Because Cosmos++ uses a zone-centered, finite-volume method, we can not use the traditional staggered-mesh constrained transport scheme of Evans & Hawley. Instead we must implement a more general scheme; we chose the Flux-CT scheme as described by Toth. Here we present comparisons of results using the divergence-cleanser and constrained transport options in Cosmos++.
Formal language constrained path problems
Energy Technology Data Exchange (ETDEWEB)
Barrett, C.; Jacob, R.; Marathe, M.
1997-07-08
In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.
String Theory Origin of Constrained Multiplets
Kallosh, Renata; Wrase, Timm
2016-01-01
We study the non-linearly realized spontaneously broken supersymmetry of the (anti-)D3-brane action in type IIB string theory. The worldvolume fields are one vector $A_\\mu$, three complex scalars $\\phi^i$ and four 4d fermions $\\lambda^0$, $\\lambda^i$. These transform, in addition to the more familiar N=4 linear supersymmetry, also under 16 spontaneously broken, non-linearly realized supersymmetries. We argue that the worldvolume fields can be packaged into the following constrained 4d non-linear N=1 multiplets: four chiral multiplets $S$, $Y^i$ that satisfy $S^2=SY^i=0$ and contain the worldvolume fermions $\\lambda^0$ and $\\lambda^i$; and four chiral multiplets $W_\\alpha$, $H^i$ that satisfy $S W_\\alpha=0$ and $S \\bar D_{\\dot \\alpha} \\bar H^{\\bar \\imath}=0$ and contain the vector $A_\\mu$ and the scalars $\\phi^i$. We also discuss how placing an anti-D3-brane on top of intersecting O7-planes can lead to an orthogonal multiplet $\\Phi$ that satisfies $S(\\Phi-\\bar \\Phi)=0$, which is particularly interesting for in...
Constrained length minimum inductance gradient coil design.
Chronik, B A; Rutt, B K
1998-02-01
A gradient coil design algorithm capable of controlling the position of the homogeneous region of interest (ROI) with respect to the current-carrying wires is required for many advanced imaging and spectroscopy applications. A modified minimum inductance target field method that allows the placement of a set of constraints on the final current density is presented. This constrained current minimum inductance method is derived in the context of previous target field methods. Complete details are shown and all equations required for implementation of the algorithm are given. The method has been implemented on computer and applied to the design of both a 1:1 aspect ratio (length:diameter) central ROI and a 2:1 aspect ratio edge ROI gradient coil. The 1:1 design demonstrates that a general analytic method can be used to easily obtain very short gradient coil designs for use with specialized magnet systems. The edge gradient design demonstrates that designs that allow imaging of the neck region with a head sized gradient coil can be obtained, as well as other applications requiring edge-of-cylinder regions of uniformity.
Giambiagi, Laura; Alvarez, Pamela; Spagnotto, Silvana
2016-09-01
In order to understand the response of the stress field state to intrinsic processes during the construction of the Andes, such as thickening of the continental crust, lithospheric delamination, and/or thermal weakening, we investigate the stress field evolution of the arc region since the last 20 Myr, in the central Andes (22-26.5°S). The 43 reduced paleostress tensors derived from inversion of 682 fault slip data reveal a complex pattern of stress states during the last episode of orogenic construction and topographic uplift. We identify two geodynamic stages: the first stage corresponds to the construction of the Altiplano/Puna plateau and the second one to its gravitational collapse. Four stress states that have prevailed in the Altiplano/Puna plateau since middle Miocene times characterize the transition from one stage to the other. Along the study latitudes, a spatiotemporal change in stress state is clearly observed, which led to an understanding that a change in the stress field may be related not only to the boundary conditions but also to intrinsic factors associated with the construction of the Andean orogeny. Our results suggest that approximately at 13-10 Ma and approximately 8-5 Ma, in the southern Altiplano and northern Puna, and in the southern Puna, respectively, regional elevation and crustal thicknesses reached threshold values necessary to generate the orogenic collapse.
Towards better constrained models of the solar magnetic cycle
Munoz-Jaramillo, Andres
2010-12-01
The best tools we have for understanding the origin of solar magnetic variability are kinematic dynamo models. During the last decade, this type of models has seen a continuous evolution and has become increasingly successful at reproducing solar cycle characteristics. The basic ingredients of these models are: the solar differential rotation -- which acts as the main source of energy for the system by shearing the magnetic field; the meridional circulation -- which plays a crucial role in magnetic field transport; the turbulent diffusivity -- which attempts to capture the effect of convective turbulence on the large scale magnetic field; and the poloidal field source -- which closes the cycle by regenerating the poloidal magnetic field. However, most of these ingredients remain poorly constrained which allows one to obtain solar-like solutions by "tuning" the input parameters, leading to controversy regarding which parameter set is more appropriate. In this thesis we revisit each of those ingredients in an attempt to constrain them better by using observational data and theoretical considerations, reducing the amount of free parameters in the model. For the meridional flow and differential rotation we use helioseismic data to constrain free parameters and find that the differential rotation is well determined, but the available data can only constrain the latitudinal dependence of the meridional flow. For the turbulent magnetic diffusivity we show that combining mixing-length theory estimates with magnetic quenching allows us to obtain viable magnetic cycles and that the commonly used diffusivity profiles can be understood as a spatiotemporal average of this process. For the poloidal source we introduce a more realistic way of modeling active region emergence and decay and find that this resolves existing discrepancies between kinematic dynamo models and surface flux transport simulations. We also study the physical mechanisms behind the unusually long minimum of
HYBRIDIZATION AND CHAMELEONIC JOURNALISM
Directory of Open Access Journals (Sweden)
Adriana Schryver Kurtz
2016-12-01
Full Text Available O texto aborda a crescente hibridização entre o Jornalismo e demais formatos midiáticos como resultado natural de um processo que já está na própria raiz da comunicação enquanto atividade histórica. A lógica interna e as potencialidades estéticas e discursivas do fenômeno são analisadas a partir das convergências entre jornalismo e cinema. Para tanto, utiliza o falso documentário Zelig (1983, texto fílmico de Woody Allen, híbrido por natureza, postulado como um microcosmo rico em pistas e sugestões para refletir sobre a fusão entre conteúdos informativos e não informativos. PALAVRAS-CHAVE: Hibridização; Jornalismo; Cinema; Zelig. ABSTRACT The text discusses the growing hybridization between journalism and other media formats as a natural result of a process that is already in the very root of communication while historical activity. The internal logic and the aesthetic and discursive potential of the phenomenon are analyzed through the convergences between journalism and cinema. Therefore, uses the mockumentary Zelig (1983, filmic text of Woody Allen, hybrid by nature, postulated as a microcosm rich in clues and suggestions to reflect about the merger between informative and uninformative content. KEYWORDS: Hybridization; Journalism; Cinema; Zelig. RESUMEN El texto aborda la creciente hibridación entre el periodismo y otros formatos de medios como um resultado natural de un proceso que ya está en la raíz misma de la comunicación mientras actividad histórica. Se analizan la lógica interna y el potencial estético y discursivo del fenómeno a través de las convergencias entre el periodismo y el cine. Para ello, utiliza el falso documental Zelig (1983, texto fílmico de Woody Allen, híbrido en su naturaleza, postulado como un microcosmos rico en pistas y sugerencias para reflexionar sobre la fusión entre contenidos informativos y no informativos. PALABRAS CLAVE: Hibridación; Periodismo; Cine; Zelig. Arquivamento e preservação de longo prazo do arquivo em: OpenDepot / Edina (The University of Edinburgh: em processo de inclusão/indexação SSOAR-GESIS – Leibniz-Institut (Alemanha: HAL (França: em processo de inclusão/indexação
DEFF Research Database (Denmark)
Marfelt, Mikkel Mouritz
Due to advancements in technology and the expansion of companies onto a global level, organizations have become increasingly aware of the need to understand and manage diverse workforces; that is, the need to understand and manage differences among employees across borders (such as geographical......, cultural, professional, etc.). This PhD dissertation studies this phenomenon, ‘a diverse workforce’, in a large Scandinavian pharmaceutical company. The dissertation follows the Diverse and Global Workforce (DGW) project, a ‘headquarter centric’ and strategic corporate initiative to address the rapid...... global expansion of the company workforce....
Gyrification from constrained cortical expansion
Tallinen, Tuomas; Biggins, John S; Mahadevan, L
2015-01-01
The exterior of the mammalian brain - the cerebral cortex - has a conserved layered structure whose thickness varies little across species. However, selection pressures over evolutionary time scales have led to cortices that have a large surface area to volume ratio in some organisms, with the result that the brain is strongly convoluted into sulci and gyri. Here we show that the gyrification can arise as a nonlinear consequence of a simple mechanical instability driven by tangential expansion of the gray matter constrained by the white matter. A physical mimic of the process using a layered swelling gel captures the essence of the mechanism, and numerical simulations of the brain treated as a soft solid lead to the formation of cusped sulci and smooth gyri similar to those in the brain. The resulting gyrification patterns are a function of relative cortical expansion and relative thickness (compared with brain size), and are consistent with observations of a wide range of brains, ranging from smooth to highl...
Constraining QGP properties with CHIMERA
Garishvili, Irakli; Abelev, Betty; Cheng, Michael; Glenn, Andrew; Soltz, Ron
2011-10-01
Understanding essential properties of strongly interacting matter is arguably the most important goal of the relativistic heavy-ion programs both at RHIC and the LHC. In particular, constraining observables such as ratio of shear viscosity to entropy density, η/s, initial temperature, Tinit, and energy density is of critical importance. For this purpose we have developed CHIMERA, Comprehensive Heavy Ion Model Reporting and Evaluation Algorithm. CHIMERA is designed to facilitate global statistical comparison of results from our multi-stage hydrodynamics/hadron cascade model of heavy ion collisions to the key soft observables (HBT, elliptic flow, spectra) measured at RHIC and the LHC. Within this framework the data representing multiple different measurements from different experiments are compiled into single format. One of the unique features of CHIMERA is, that in addition to taking into account statistical errors, it also treats different types of systematic uncertainties. The hydrodynamics/hadron cascade model used in the framework incorporates different initial state conditions, pre-equilibrium flow, the UVH2+1 viscous hydro model, Cooper-Frye freezeout, and the UrQMD hadronic cascade model. The sensitivity of the observables to the equation of state (EoS) is explored using several EoS's in the hydrodynamic evolution. The latest results from CHIMERA, including data from the LHC, will be presented.
Constrained Allocation Flux Balance Analysis
Mori, Matteo; Hwa, Terence; Martin, Olivier C.
2016-01-01
New experimental results on bacterial growth inspire a novel top-down approach to study cell metabolism, combining mass balance and proteomic constraints to extend and complement Flux Balance Analysis. We introduce here Constrained Allocation Flux Balance Analysis, CAFBA, in which the biosynthetic costs associated to growth are accounted for in an effective way through a single additional genome-wide constraint. Its roots lie in the experimentally observed pattern of proteome allocation for metabolic functions, allowing to bridge regulation and metabolism in a transparent way under the principle of growth-rate maximization. We provide a simple method to solve CAFBA efficiently and propose an “ensemble averaging” procedure to account for unknown protein costs. Applying this approach to modeling E. coli metabolism, we find that, as the growth rate increases, CAFBA solutions cross over from respiratory, growth-yield maximizing states (preferred at slow growth) to fermentative states with carbon overflow (preferred at fast growth). In addition, CAFBA allows for quantitatively accurate predictions on the rate of acetate excretion and growth yield based on only 3 parameters determined by empirical growth laws. PMID:27355325
Constraining the Europa Neutral Torus
Smith, Howard T.; Mitchell, Donald; mauk, Barry; Johnson, Robert E.; clark, george
2016-10-01
"Neutral tori" consist of neutral particles that usually co-orbit along with their source forming a toroidal (or partial toroidal) feature around the planet. The distribution and composition of these features can often provide important, if not unique, insight into magnetospheric particles sources, mechanisms and dynamics. However, these features can often be difficult to directly detect. One innovative method for detecting neutral tori is by observing Energetic Neutral Atoms (ENAs) that are generally considered produced as a result of charge exchange interactions between charged and neutral particles.Mauk et al. (2003) reported the detection of a Europa neutral particle torus using ENA observations. The presence of a Europa torus has extremely large implications for upcoming missions to Jupiter as well as understanding possible activity at this moon and providing critical insight into what lies beneath the surface of this icy ocean world. However, ENAs can also be produced as a result of charge exchange interactions between two ionized particles and in that case cannot be used to infer the presence of neutral particle population. Thus, a detailed examination of all possible source interactions must be considered before one can confirm that likely original source population of these ENA images is actually a Europa neutral particle torus. For this talk, we examine the viability that the Mauk et al. (2003) observations were actually generated from a neutral torus emanating from Europa as opposed to charge particle interactions with plasma originating from Io. These results help constrain such a torus as well as Europa source processes.
Modeling the microstructural evolution during constrained sintering
DEFF Research Database (Denmark)
Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini
A mesoscale numerical model able to simulate solid state constrained sintering is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element method for calculating stresses. The sintering behavior of a sample constrained by a rigid substrate ...
Efficient caching for constrained skyline queries
DEFF Research Database (Denmark)
Mortensen, Michael Lind; Chester, Sean; Assent, Ira;
2015-01-01
Constrained skyline queries retrieve all points that optimize some user’s preferences subject to orthogonal range constraints, but at significant computational cost. This paper is the first to propose caching to improve constrained skyline query response time. Because arbitrary range constraints ...
Bayesian evaluation of inequality constrained hypotheses
Gu, X.; Mulder, J.; Deković, M.; Hoijtink, H.
2014-01-01
Bayesian evaluation of inequality constrained hypotheses enables researchers to investigate their expectations with respect to the structure among model parameters. This article proposes an approximate Bayes procedure that can be used for the selection of the best of a set of inequality constrained
Determination of optimal gains for constrained controllers
Energy Technology Data Exchange (ETDEWEB)
Kwan, C.M.; Mestha, L.K.
1993-08-01
In this report, we consider the determination of optimal gains, with respect to a certain performance index, for state feedback controllers where some elements in the gain matrix are constrained to be zero. Two iterative schemes for systematically finding the constrained gain matrix are presented. An example is included to demonstrate the procedures.
Uttenthaler, Stefan; Nataf, David M; Robin, Annie C; Lebzelter, Thomas; Chen, B
2012-01-01
The presence of two stellar populations in the Milky Way bulge has been reported recently. We aim at studying the abundances and kinematics of stars in the outer bulge, thereby providing additional constraints on models of its formation. Spectra of 401 red giant stars in a field at (l,b)=(0{\\deg},-10{\\deg}) were obtained with FLAMES at the VLT. Stars of luminosities down to below the two bulge red clumps (RCs) are included. From these spectra we measure general metallicities, abundances of Fe and the alpha-elements, and radial velocities (RV) of the stars. These measurements as well as photometric data are compared to simulations with the Besancon and TRILEGAL models of the Galaxy. We confirm the presence of two populations among our sample stars: i) a metal-rich one at [M/H] ~+0.3, comprising about 30% of the sample, with low RV dispersion and low alpha-abundance, and ii) a metal-poor population at [M/H] ~-0.6 with high RV dispersion and high alpha-abundance. The metal-rich population could be connected to t...
Constrained Optimization and Optimal Control for Partial Differential Equations
Leugering, Günter; Griewank, Andreas
2012-01-01
This special volume focuses on optimization and control of processes governed by partial differential equations. The contributors are mostly participants of the DFG-priority program 1253: Optimization with PDE-constraints which is active since 2006. The book is organized in sections which cover almost the entire spectrum of modern research in this emerging field. Indeed, even though the field of optimal control and optimization for PDE-constrained problems has undergone a dramatic increase of interest during the last four decades, a full theory for nonlinear problems is still lacking. The cont
A Dynamic Programming Approach to Constrained Portfolios
DEFF Research Database (Denmark)
Kraft, Holger; Steffensen, Mogens
2013-01-01
This paper studies constrained portfolio problems that may involve constraints on the probability or the expected size of a shortfall of wealth or consumption. Our first contribution is that we solve the problems by dynamic programming, which is in contrast to the existing literature that applies...... the martingale method. More precisely, we construct the non-separable value function by formalizing the optimal constrained terminal wealth to be a (conjectured) contingent claim on the optimal non-constrained terminal wealth. This is relevant by itself, but also opens up the opportunity to derive new solutions...
Hamiltonian analysis of SO(4,1)-constrained BF theory
Energy Technology Data Exchange (ETDEWEB)
Durka, R; Kowalski-Glikman, J, E-mail: rdurka@ift.uni.wroc.p, E-mail: jkowalskiglikman@ift.uni.wroc.p [Institute for Theoretical Physics, University of Wroclaw, Pl. Maxa Borna 9, 50-204 Wroclaw (Poland)
2010-09-21
In this paper we discuss the canonical analysis of SO(4,1)-constrained BF theory. The action of this theory contains topological terms appended by a term that breaks the gauge symmetry down to the Lorentz subgroup SO(3,1). The equations of motion of this theory turn out to be the vacuum Einstein equations. By solving the B field equations one finds that the action of this theory contains not only the standard Einstein-Cartan term but also the Holst term proportional to the inverse of the Immirzi parameter, as well as a combination of topological invariants. We show that the structure of the constraints of an SO(4,1)-constrained BF theory is exactly that of gravity in the Holst formulation. We also briefly discuss the quantization of the theory.
A second-generation constrained reaction volume shock tube.
Campbell, M F; Tulgestke, A M; Davidson, D F; Hanson, R K
2014-05-01
We have developed a shock tube that features a sliding gate valve in order to mechanically constrain the reactive test gas mixture to an area close to the shock tube endwall, separating it from a specially formulated non-reactive buffer gas mixture. This second-generation Constrained Reaction Volume (CRV) strategy enables near-constant-pressure shock tube test conditions for reactive experiments behind reflected shocks, thereby enabling improved modeling of the reactive flow field. Here we provide details of the design and operation of the new shock tube. In addition, we detail special buffer gas tailoring procedures, analyze the buffer/test gas interactions that occur on gate valve opening, and outline the size range of fuels that can be studied using the CRV technique in this facility. Finally, we present example low-temperature ignition delay time data to illustrate the CRV shock tube's performance.
A second-generation constrained reaction volume shock tube
Campbell, M. F.; Tulgestke, A. M.; Davidson, D. F.; Hanson, R. K.
2014-05-01
We have developed a shock tube that features a sliding gate valve in order to mechanically constrain the reactive test gas mixture to an area close to the shock tube endwall, separating it from a specially formulated non-reactive buffer gas mixture. This second-generation Constrained Reaction Volume (CRV) strategy enables near-constant-pressure shock tube test conditions for reactive experiments behind reflected shocks, thereby enabling improved modeling of the reactive flow field. Here we provide details of the design and operation of the new shock tube. In addition, we detail special buffer gas tailoring procedures, analyze the buffer/test gas interactions that occur on gate valve opening, and outline the size range of fuels that can be studied using the CRV technique in this facility. Finally, we present example low-temperature ignition delay time data to illustrate the CRV shock tube's performance.
Hamiltonian analysis of SO(4,1) constrained BF theory
Durka, R
2010-01-01
In this paper we discuss canonical analysis of SO(4,1) constrained BF theory. The action of this theory contains topological terms appended by a term that breaks the gauge symmetry down to the Lorentz subgroup SO(3,1). The equations of motion of this theory turn out to be the vacuum Einstein equations. By solving the B field equations one finds that the action of this theory contains not only the standard Einstein-Cartan term, but also the Holst term proportional to the inverse of the Immirzi parameter, as well as a combination of topological invariants. We show that the structure of the constraints of a SO(4,1) constrained BF theory is exactly that of gravity in Holst formulation. We also briefly discuss quantization of the theory.
Applications of a constrained mechanics methodology in economics
Janová, Jitka
2011-01-01
The paper presents instructive interdisciplinary applications of constrained mechanics calculus in economics on a level appropriate for the undergraduate physics education. The aim of the paper is: 1. to meet the demand for illustrative examples suitable for presenting the background of the highly expanding research field of econophysics even on the undergraduate level and 2. to enable the students to understand deeper the principles and methods routinely used in mechanics by looking at the well known methodology from the different perspective of economics. Two constrained dynamic economic problems are presented using the economic terminology in an intuitive way. First, the Phillips model of business cycle is presented as a system of forced oscillations and the general problem of two interacting economies is solved by the nonholonomic dynamics approach. Second, the Cass-Koopmans-Ramsey model of economical growth is solved as a variational problem with a velocity dependent constraint using the vakonomic approa...
Constraining Cosmological Models with Different Observations
Wei, J. J.
2016-07-01
With the observations of Type Ia supernovae (SNe Ia), scientists discovered that the Universe is experiencing an accelerated expansion, and then revealed the existence of dark energy in 1998. Since the amazing discovery, cosmology has became a hot topic in the physical research field. Cosmology is a subject that strongly depends on the astronomical observations. Therefore, constraining different cosmological models with all kinds of observations is one of the most important research works in the modern cosmology. The goal of this thesis is to investigate cosmology using the latest observations. The observations include SNe Ia, Type Ic Super Luminous supernovae (SLSN Ic), Gamma-ray bursts (GRBs), angular diameter distance of galaxy cluster, strong gravitational lensing, and age measurements of old passive galaxies, etc. In Chapter 1, we briefly review the research background of cosmology, and introduce some cosmological models. Then we summarize the progress on cosmology from all kinds of observations in more details. In Chapter 2, we present the results of our studies on the supernova cosmology. The main difficulty with the use of SNe Ia as standard candles is that one must optimize three or four nuisance parameters characterizing SN luminosities simultaneously with the parameters of an expansion model of the Universe. We have confirmed that one should optimize all of the parameters by carrying out the method of maximum likelihood estimation in any situation where the parameters include an unknown intrinsic dispersion. The commonly used method, which estimates the dispersion by requiring the reduced χ^{2} to equal unity, does not take into account all possible variances among the parameters. We carry out such a comparison of the standard ΛCDM cosmology and the R_{h}=ct Universe using the SN Legacy Survey sample of 252 SN events, and show that each model fits its individually reduced data very well. Moreover, it is quite evident that SLSNe Ic may be useful
Potential Energy Surface in Hartree-Fock Theory:Adiabatic or Configuration-Constrained?
Institute of Scientific and Technical Information of China (English)
GUO Lu; Sakata Fumihiko; ZHAO En-Guang
2004-01-01
Validity of adiabatic assumption is discussed within the constrained Hartree-Fock theory for self-conjugate nucleus 72Kr. It is shown that the adiabatic assumption does not provide a correct description for the nature of nucleus when a configuration change is involved. The excited Hartree-Fock states and the continuously-connected constrained Hartree-Fock states are given for the first time by applying the configuration dictated constrained Hartree-Fock theory with Gogny force. The importance of self-consistency between the mean-field and the single particle wave functions is emphasized even when a small number of nucleons are involved in the configuration change.
Constrained crosstalk resistant adaptive noise canceller
Parsa, V.; Parker, P.
1994-08-01
The performance of an adaptive noise canceller (ANC) is sensitive to the presence of signal `crosstalk' in the reference channel. The authors propose a novel approach to crosstalk resistant adaptive noise cancellation, namely the constrained crosstalk resistant adaptive noise canceller (CCRANC). The theoretical analysis of the CCRANC along with the constrained algorithm is presented. The performance of the CCRANC in recovering somatosensory evoked potentials (SEPs) from myoelectric interference is then evaluated through simulations.
CANONICAL FORMULATION OF NONHOLONOMIC CONSTRAINED SYSTEMS
Institute of Scientific and Technical Information of China (English)
GUO YONG-XIN; YU YING; HUANG HAI-JUN
2001-01-01
Based on the Ehresmann connection theory and symplectic geometry, the canonical formulation of nonholonomic constrained mechanical systems is described. Following the Lagrangian formulation of the constrained system, the Hamiltonian formulation is given by Legendre transformation. The Poisson bracket defined by an anti-symmetric tensor does not satisfy the Jacobi identity for the nonintegrability of nonholonomic constraints. The constraint manifold can admit symplectic submanifold for some cases, in which the Lie algebraic structure exists.
On the origin of constrained superfields
Energy Technology Data Exchange (ETDEWEB)
Dall’Agata, G. [Dipartimento di Fisica “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy); Dudas, E. [Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay,F-91128 Palaiseau (France); Farakos, F. [Dipartimento di Fisica “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy)
2016-05-06
In this work we analyze constrained superfields in supersymmetry and supergravity. We propose a constraint that, in combination with the constrained goldstino multiplet, consistently removes any selected component from a generic superfield. We also describe its origin, providing the operators whose equations of motion lead to the decoupling of such components. We illustrate our proposal by means of various examples and show how known constraints can be reproduced by our method.
A TV-constrained decomposition method for spectral CT
Guo, Xiaoyue; Zhang, Li; Xing, Yuxiang
2017-03-01
Spectral CT is attracting more and more attention in medicine, industrial nondestructive testing and security inspection field. Material decomposition is an important issue to a spectral CT to discriminate materials. Because of the spectrum overlap of energy channels, as well as the correlation of basis functions, it is well acknowledged that decomposition step in spectral CT imaging causes noise amplification and artifacts in component coefficient images. In this work, we propose materials decomposition via an optimization method to improve the quality of decomposed coefficient images. On the basis of general optimization problem, total variance minimization is constrained on coefficient images in our overall objective function with adjustable weights. We solve this constrained optimization problem under the framework of ADMM. Validation on both a numerical dental phantom in simulation and a real phantom of pig leg on a practical CT system using dual-energy imaging is executed. Both numerical and physical experiments give visually obvious better reconstructions than a general direct inverse method. SNR and SSIM are adopted to quantitatively evaluate the image quality of decomposed component coefficients. All results demonstrate that the TV-constrained decomposition method performs well in reducing noise without losing spatial resolution so that improving the image quality. The method can be easily incorporated into different types of spectral imaging modalities, as well as for cases with energy channels more than two.
Applications of a constrained mechanics methodology in economics
Energy Technology Data Exchange (ETDEWEB)
Janova, Jitka, E-mail: janova@mendelu.cz [Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic); Department of Statistics and Operation Analysis, Faculty of Business and Economics, Mendel University in Brno, Zemedelska 1, 613 00 Brno (Czech Republic)
2011-11-15
This paper presents instructive interdisciplinary applications of constrained mechanics calculus in economics on a level appropriate for undergraduate physics education. The aim of the paper is (i) to meet the demand for illustrative examples suitable for presenting the background of the highly expanding research field of econophysics even at the undergraduate level and (ii) to enable the students to gain a deeper understanding of the principles and methods routinely used in mechanics by looking at the well-known methodology from the different perspective of economics. Two constrained dynamic economic problems are presented using the economic terminology in an intuitive way. First, the Phillips model of the business cycle is presented as a system of forced oscillations and the general problem of two interacting economies is solved by the nonholonomic dynamics approach. Second, the Cass-Koopmans-Ramsey model of economical growth is solved as a variational problem with a velocity-dependent constraint using the vakonomic approach. The specifics of the solution interpretation in economics compared to mechanics is discussed in detail, a discussion of the nonholonomic and vakonomic approaches to constrained problems in mechanics and economics is provided and an economic interpretation of the Lagrange multipliers (possibly surprising for the students of physics) is carefully explained. This paper can be used by the undergraduate students of physics interested in interdisciplinary physics applications to gain an understanding of the current scientific approach to economics based on a physical background, or by university teachers as an attractive supplement to classical mechanics lessons.
Outcome and complications of constrained acetabular components.
Yang, Cao; Goodman, Stuart B
2009-02-01
Constrained acetabular liners were developed for the surgical treatment of recurrent instability by holding the femoral head captive within the socket. This article summarizes the data describing constrained component designs, indications, outcome, and complications. Different designs accept head sizes of varying diameter and have differing amounts of rim elevation and offset, allowing slight variations in the range of movement allowed. Complications of constrained acetabular components can be divided into three categories. The first category is directly related to the constraining mechanism such as dislocation, head dissociation from the stem, liner dissociation from the acetabular device, and impingement with or without locking ring breakage. The second category is related to increased constraint such as aseptic component loosening and osteolysis and periprosthetic fracture. The third category includes those cases not associated with increased constraint such as infection, deep vein thrombosis, and periprosthetic fracture. This device is effective at achieving hip stability, but the complications related to the constraining mechanism and increased constraint are of concern. These devices should be used as a salvage measure for the treatment of severe instability.
New quasidilaton theory in partially constrained vielbein formalism
De Felice, Antonio; Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia; Mukohyama, Shinji; Tanahashi, Norihiro
2016-05-01
In this work we study the partially constrained vielbein formulation of the new quasidilaton theory of massive gravity, where the quasidilaton field couples to both physical and fiducial metrics simultaneously via a composite effective metric and Lorentz violation is introduced by a constraint on the vielbein. This formalism improves the new quasidilaton model since the Boulware-Deser ghost is removed fully non-linearly at all scales. This also yields crucial implications in the cosmological applications. We derive the governing cosmological background evolution and study the stability of the attractor solution.
New quasidilaton theory in partially constrained vielbein formalism
Energy Technology Data Exchange (ETDEWEB)
Felice, Antonio De [Center for Gravitational Physics, Yukawa Institute for Theoretical Physics,Kyoto University,606-8502, Kyoto (Japan); Gümrükçüoğlu, A. Emir [Theoretical Physics Group, Blackett Laboratory, Imperial College London,South Kensington Campus, London, SW7 2AZ (United Kingdom); Heisenberg, Lavinia [Institute for Theoretical Studies, ETH Zurich,Clausiusstrasse 47, 8092 Zurich (Switzerland); Mukohyama, Shinji [Center for Gravitational Physics, Yukawa Institute for Theoretical Physics,Kyoto University,606-8502, Kyoto (Japan); Kavli Institute for the Physics and Mathematics of the Universe (WPI),UTIAS, The University of Tokyo,Kashiwa, Chiba 277-8583 (Japan); Tanahashi, Norihiro [Department of Applied Mathematics and Theoretical Physics,Centre for Mathematical Sciences, University of Cambridge,Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
2016-05-25
In this work we study the partially constrained vielbein formulation of the new quasidilaton theory of massive gravity, where the quasidilaton field couples to both physical and fiducial metrics simultaneously via a composite effective metric and Lorentz violation is introduced by a constraint on the vielbein. This formalism improves the new quasidilaton model since the Boulware-Deser ghost is removed fully non-linearly at all scales. This also yields crucial implications in the cosmological applications. We derive the governing cosmological background evolution and study the stability of the attractor solution.
A moving mesh unstaggered constrained transport scheme for magnetohydrodynamics
Mocz, Philip; Springel, Volker; Vogelsberger, Mark; Marinacci, Federico; Hernquist, Lars
2016-01-01
We present a constrained transport (CT) algorithm for solving the 3D ideal magnetohydrodynamic (MHD) equations on a moving mesh, which maintains the divergence-free condition on the magnetic field to machine-precision. Our CT scheme uses an unstructured representation of the magnetic vector potential, making the numerical method simple and computationally efficient. The scheme is implemented in the moving mesh code Arepo. We demonstrate the performance of the approach with simulations of driven MHD turbulence, a magnetized disc galaxy, and a cosmological volume with primordial magnetic field. We compare the outcomes of these experiments to those obtained with a previously implemented Powell divergence-cleaning scheme. While CT and the Powell technique yield similar results in idealized test problems, some differences are seen in situations more representative of astrophysical flows. In the turbulence simulations, the Powell cleaning scheme artificially grows the mean magnetic field, while CT maintains this co...
Maximizing entropy of image models for 2-D constrained coding
DEFF Research Database (Denmark)
Forchhammer, Søren; Danieli, Matteo; Burini, Nino
2010-01-01
This paper considers estimating and maximizing the entropy of two-dimensional (2-D) fields with application to 2-D constrained coding. We consider Markov random fields (MRF), which have a non-causal description, and the special case of Pickard random fields (PRF). The PRF are 2-D causal finite...... context models, which define stationary probability distributions on finite rectangles and thus allow for calculation of the entropy. We consider two binary constraints and revisit the hard square constraint given by forbidding neighboring 1s and provide novel results for the constraint that no uniform 2...... £ 2 squares contains all 0s or all 1s. The maximum values of the entropy for the constraints are estimated and binary PRF satisfying the constraint are characterized and optimized w.r.t. the entropy. The maximum binary PRF entropy is 0.839 bits/symbol for the no uniform squares constraint. The entropy...
Continuation of Sets of Constrained Orbit Segments
DEFF Research Database (Denmark)
Schilder, Frank; Brøns, Morten; Chamoun, George Chaouki
Sets of constrained orbit segments of time continuous flows are collections of trajectories that represent a whole or parts of an invariant set. A non-trivial but simple example is a homoclinic orbit. A typical representation of this set consists of an equilibrium point of the flow and a trajecto...... orbit segments, this is very disadvantageous in practice. In this talk we will present an algorithm that allows the efficient continuation of sets of constrained orbit segments together with the solution of the full variational problem.......Sets of constrained orbit segments of time continuous flows are collections of trajectories that represent a whole or parts of an invariant set. A non-trivial but simple example is a homoclinic orbit. A typical representation of this set consists of an equilibrium point of the flow and a trajectory...
Continuation of Sets of Constrained Orbit Segments
DEFF Research Database (Denmark)
Schilder, Frank; Brøns, Morten; Chamoun, George Chaouki;
Sets of constrained orbit segments of time continuous flows are collections of trajectories that represent a whole or parts of an invariant set. A non-trivial but simple example is a homoclinic orbit. A typical representation of this set consists of an equilibrium point of the flow and a trajectory...... that starts close and returns close to this fixed point within finite time. More complicated examples are hybrid periodic orbits of piecewise smooth systems or quasi-periodic invariant tori. Even though it is possible to define generalised two-point boundary value problems for computing sets of constrained...... orbit segments, this is very disadvantageous in practice. In this talk we will present an algorithm that allows the efficient continuation of sets of constrained orbit segments together with the solution of the full variational problem....
Bayesian evaluation of inequality constrained hypotheses.
Gu, Xin; Mulder, Joris; Deković, Maja; Hoijtink, Herbert
2014-12-01
Bayesian evaluation of inequality constrained hypotheses enables researchers to investigate their expectations with respect to the structure among model parameters. This article proposes an approximate Bayes procedure that can be used for the selection of the best of a set of inequality constrained hypotheses based on the Bayes factor in a very general class of statistical models. The software package BIG is provided such that psychologists can use the approach proposed for the analysis of their own data. To illustrate the approximate Bayes procedure and the use of BIG, we evaluate inequality constrained hypotheses in a path model and a logistic regression model. Two simulation studies on the performance of our approximate Bayes procedure show that it results in accurate Bayes factors. PsycINFO Database Record (c) 2014 APA, all rights reserved
Constrained Geodesic Centers of a Simple Polygon
Oh, Eunjin; Son, Wanbin; Ahn, Hee-Kap
2016-01-01
For any two points in a simple polygon P, the geodesic distance between them is the length of the shortest path contained in P that connects them. A geodesic center of a set S of sites (points) with respect to P is a point in P that minimizes the geodesic distance to its farthest site. In many realistic facility location problems, however, the facilities are constrained to lie in feasible regions. In this paper, we show how to compute the geodesic centers constrained to a set of line segment...
Constrained instanton and black hole creation
Institute of Scientific and Technical Information of China (English)
WU Zhongchao; XU Donghui
2004-01-01
A gravitational instanton is considered as the seed for the creation of a universe. However, there exist too few instantons. To include many interesting phenomena in the framework of quantum cosmology, the concept of constrained gravitational instanton is inevitable. In this paper we show how a primordial black hole is created from a constrained instanton. The quantum creation of a generic black hole in the closed or open background is completely resolved. The relation of the creation scenario with gravitational thermodynamics and topology is discussed.
Atom-interferometry constraints on dark energy
Hamilton, Paul; Haslinger, Philipp; Simmons, Quinn; Müller, Holger; Khoury, Justin
2015-01-01
If dark energy---which drives the accelerated expansion of the universe---consists of a new light scalar field, it might be detectable as a "fifth force" between normal-matter objects, in potential conflict with precision tests of gravity. There has, however, been much theoretical progress in developing theories with screening mechanisms, which can evade detection by suppressing forces in regions of high density, such as the laboratory. One prominent example is the chameleon field. We reduce the effect of this screening mechanism by probing the chameleon with individual atoms rather than bulk matter. Using a cesium matter-wave interferometer near a spherical mass in an ultra-high vacuum chamber, we constrain a wide class of dynamical dark energy theories. Our experiment excludes a range of chameleon theories that reproduce the observed cosmic acceleration.
Mantle Convection Models Constrained by Seismic Tomography
Durbin, C. J.; Shahnas, M.; Peltier, W. R.; Woodhouse, J. H.
2011-12-01
Perovskite-post-Perovskite transition (Murakami et al., 2004, Science) that appears to define the D" layer at the base of the mantle. In this initial phase of what will be a longer term project we are assuming that the internal mantle viscosity structure is spherically symmetric and compatible with the recent inferences of Peltier and Drummond (2010, Geophys. Res. Lett.) based upon glacial isostatic adjustment and Earth rotation constraints. The internal density structure inferred from the tomography model is assimilated into the convection model by continuously "nudging" the modification to the input density structure predicted by the convection model back towards the tomographic constraint at the long wavelengths that the tomography specifically resolves, leaving the shorter wavelength structure free to evolve, essentially "slaved" to the large scale structure. We focus upon the ability of the nudged model to explain observed plate velocities, including both their poloidal (divergence related) and toroidal (strike slip fault related) components. The true plate velocity field is then used as an additional field towards which the tomographically constrained solution is nudged.
PRICING AND HEDGING OPTION UNDER PORTFOLIO CONSTRAINED
Institute of Scientific and Technical Information of China (English)
魏刚; 陈世平
2001-01-01
The authors employ convex analysis and stochastic control approach to study the question of hedging contingent claims with portfolio constrained to take values in a given closed, convex subset of RK, and extend the results of Gianmario Tessitore and Jerzy Zabczyk[6] on pricing options in multiasset and multinominal model.
CONSTRAINED RATIONAL CUBIC SPLINE AND ITS APPLICATION
Institute of Scientific and Technical Information of China (English)
Qi Duan; Huan-ling Zhang; Xiang Lai; Nan Xie; Fu-hua (Frank) Cheng
2001-01-01
In this paper, a kind of rational cubic interpolation functionwith linear denominator is constructed. The constrained interpolation with constraint on shape of the interpolating curves and on the second-order derivative of the interpolating function is studied by using this interpolation, and as the consequent result, the convex interpolation conditions have been derived.
Neuroevolutionary Constrained Optimization for Content Creation
DEFF Research Database (Denmark)
Liapis, Antonios; Yannakakis, Georgios N.; Togelius, Julian
2011-01-01
and thruster types and topologies) independently of game physics and steering strategies. According to the proposed framework, the designer picks a set of requirements for the spaceship that a constrained optimizer attempts to satisfy. The constraint satisfaction approach followed is based on neuroevolution...
Constrained tri-sphere kinematic positioning system
Viola, Robert J
2010-12-14
A scalable and adaptable, six-degree-of-freedom, kinematic positioning system is described. The system can position objects supported on top of, or suspended from, jacks comprising constrained joints. The system is compatible with extreme low temperature or high vacuum environments. When constant adjustment is not required a removable motor unit is available.
Bound constrained quadratic programming via piecewise
DEFF Research Database (Denmark)
Madsen, Kaj; Nielsen, Hans Bruun; Pinar, M. C.
1999-01-01
of a symmetric, positive definite matrix, and is solved by Newton iteration with line search. The paper describes the algorithm and its implementation including estimation of lambda/sub 1/ , how to get a good starting point for the iteration, and up- and downdating of Cholesky factorization. Results of extensive...... testing and comparison with other methods for constrained QP are given....
Constrained target controllability of complex networks
Guo, Wei-Feng; Zhang, Shao-Wu; Wei, Ze-Gang; Zeng, Tao; Liu, Fei; Zhang, Jingsong; Wu, Fang-Xiang; Chen, Luonan
2017-06-01
It is of great theoretical interest and practical significance to study how to control a system by applying perturbations to only a few driver nodes. Recently, a hot topic of modern network researches is how to determine driver nodes that allow the control of an entire network. However, in practice, to control a complex network, especially a biological network, one may know not only the set of nodes which need to be controlled (i.e. target nodes), but also the set of nodes to which only control signals can be applied (i.e. constrained control nodes). Compared to the general concept of controllability, we introduce the concept of constrained target controllability (CTC) of complex networks, which concerns the ability to drive any state of target nodes to their desirable state by applying control signals to the driver nodes from the set of constrained control nodes. To efficiently investigate the CTC of complex networks, we further design a novel graph-theoretic algorithm called CTCA to estimate the ability of a given network to control targets by choosing driver nodes from the set of constrained control nodes. We extensively evaluate the CTC of numerous real complex networks. The results indicate that biological networks with a higher average degree are easier to control than biological networks with a lower average degree, while electronic networks with a lower average degree are easier to control than web networks with a higher average degree. We also show that our CTCA can more efficiently produce driver nodes for target-controlling the networks than existing state-of-the-art methods. Moreover, we use our CTCA to analyze two expert-curated bio-molecular networks and compare to other state-of-the-art methods. The results illustrate that our CTCA can efficiently identify proven drug targets and new potentials, according to the constrained controllability of those biological networks.
Formation of current singularity in a topologically constrained plasma
Energy Technology Data Exchange (ETDEWEB)
Zhou, Yao [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences; Huang, Yi-Min [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences; Qin, Hong [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences; Univ Sci & Technol China, Dept Modern Phys, Hefei 230026, Anhui, Peoples R China.; Bhattacharjee, A. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences
2016-02-01
Recently a variational integrator for ideal magnetohydrodynamics in Lagrangian labeling has been developed. Its built-in frozen-in equation makes it optimal for studying current sheet formation. We use this scheme to study the Hahm-Kulsrud-Taylor problem, which considers the response of a 2D plasma magnetized by a sheared field under sinusoidal boundary forcing. We obtain an equilibrium solution that preserves the magnetic topology of the initial field exactly, with a fluid mapping that is non-differentiable. Unlike previous studies that examine the current density output, we identify a singular current sheet from the fluid mapping. These results are benchmarked with a constrained Grad-Shafranov solver. The same signature of current singularity can be found in other cases with more complex magnetic topologies.
Late time CMB anisotropies constrain mini-charged particles
Energy Technology Data Exchange (ETDEWEB)
Burrage, C.; Redondo, J.; Ringwald, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Jaeckel, J. [Univ. of Durham, Inst. for Particle Physics Phenomenology (United Kingdom)
2009-09-15
Observations of the temperature anisotropies induced as light from the CMB passes through large scale structures in the late universe are a sensitive probe of the interactions of photons in such environments. In extensions of the Standard Model which give rise to mini-charged particles, photons propagating through transverse magnetic fields can be lost to pair production of such particles. Such a decrement in the photon flux would occur as photons from the CMB traverse the magnetic fields of galaxy clusters. Therefore late time CMB anisotropies can be used to constrain the properties of mini- charged particles. We outline how this test is constructed, and present new constraints on mini-charged particles from observations of the Sunyaev-Zel'dovich effect in the Coma cluster. (orig.)
Dynamical Scaling and Phase Coexistence in Topologically Constrained DNA Melting
Fosado, Y. A. G.; Michieletto, D.; Marenduzzo, D.
2017-09-01
There is a long-standing experimental observation that the melting of topologically constrained DNA, such as circular closed plasmids, is less abrupt than that of linear molecules. This finding points to an important role of topology in the physics of DNA denaturation, which is, however, poorly understood. Here, we shed light on this issue by combining large-scale Brownian dynamics simulations with an analytically solvable phenomenological Landau mean field theory. We find that the competition between melting and supercoiling leads to phase coexistence of denatured and intact phases at the single-molecule level. This coexistence occurs in a wide temperature range, thereby accounting for the broadening of the transition. Finally, our simulations show an intriguing topology-dependent scaling law governing the growth of denaturation bubbles in supercoiled plasmids, which can be understood within the proposed mean field theory.
Symmetron Fields: Screening Long-Range Forces Through Local Symmetry Restoration
Hinterbichler, Kurt
2010-01-01
We present a novel screening mechanism that allows a scalar field to mediate a long range ~Mpc force of gravitational strength in the cosmos while satisfying local tests of gravity. The mechanism hinges on local symmetry restoration in the presence of matter. In regions of sufficiently high matter density, the field is drawn towards \\phi = 0 where its coupling to matter vanishes and the \\phi->-\\phi symmetry is restored. In regions of low density, however, the symmetry is spontaneously broken, and the field couples to matter with gravitational strength. We predict deviations from general relativity in the solar system that are within reach of next-generation experiments, as well as astrophysically observable violations of the equivalence principle. The model can be distinguished experimentally from Brans-Dicke gravity, chameleon theories and brane-world modifications of gravity.
A constrained-transport magnetohydrodynamics algorithm with near-spectral resolution
Maron, Jason; Oishi, Jeffrey
2007-01-01
Numerical simulations including magnetic fields have become important in many fields of astrophysics. Evolution of magnetic fields by the constrained transport algorithm preserves magnetic divergence to machine precision, and thus represents one preferred method for the inclusion of magnetic fields in simulations. We show that constrained transport can be implemented with volume-centered fields and hyperresistivity on a high-order finite difference stencil. Additionally, the finite-difference coefficients can be tuned to enhance high-wavenumber resolution. Similar techniques can be used for the interpolations required for dealiasing corrections at high wavenumber. Together, these measures yield an algorithm with a wavenumber resolution that approaches the theoretical maximum achieved by spectral algorithms. Because this algorithm uses finite differences instead of fast Fourier transforms, it runs faster and isn't restricted to periodic boundary conditions. Also, since the finite differences are spatially loca...
Constraining Substellar Magnetic Dynamos using Auroral Radio Emission
Kao, Melodie; Hallinan, Gregg; Pineda, J. Sebastian; Escala, Ivanna; Burgasser, Adam J.; Stevenson, David J.
2017-01-01
An important outstanding problem in dynamo theory is understanding how magnetic fields are generated and sustained in fully convective stellar objects. A number of models for possible dynamo mechanisms in this regime have been proposed but constraining data on magnetic field strengths and topologies across a wide range of mass, age, rotation rate, and temperature are sorely lacking, particularly in the brown dwarf regime. Detections of highly circularly polarized pulsed radio emission provide our only window into magnetic field measurements for objects in the ultracool brown dwarf regime. However, these detections are very rare; previous radio surveys encompassing ˜60 L6 or later targets have yielded only one detection. We have developed a selection strategy for biasing survey targets based on possible optical and infrared tracers of auroral activity. Using our selection strategy, we previously observed six late L and T dwarfs with the Jansky Very Large Array (VLA) and detected the presence of highly circularly polarized radio emission for five targets. Our initial detections at 4-8 GHz provided the most robust constraints on dynamo theory in this regime, confirming magnetic fields >2.5 kG. To further develop our understanding of magnetic fields in the ultracool brown dwarf mass regime bridging planets and stars, we present constraints on surface magnetic field strengths for two Y-dwarfs as well as higher frequency observations of the previously detected L/T dwarfs corresponding ~3.6 kG fields. By carefully comparing magnetic field measurements derived from auroral radio emission to measurements derived from Zeeman broadening and Zeeman Doppler imaging, we provide tentative evidence that the dynamo operating in this mass regime may be inconsistent with predicted values from currently in vogue models. This suggests that parameters beyond convective flux may influence magnetic field generation in brown dwarfs.
Cosmogenic photons strongly constrain UHECR source models
van Vliet, Arjen
2016-01-01
With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR) propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB) by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT's IGRB, as long as their number density is not strongly peaked at recent times.
Cosmogenic photons strongly constrain UHECR source models
van Vliet, Arjen
2017-03-01
With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR) propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB) by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT's IGRB, as long as their number density is not strongly peaked at recent times.
A constrained supersymmetric left-right model
Hirsch, Martin; Opferkuch, Toby; Porod, Werner; Staub, Florian
2016-01-01
We present a supersymmetric left-right model which predicts gauge coupling unification close to the string scale and extra vector bosons at the TeV scale. The subtleties in constructing a model which is in agreement with the measured quark masses and mixing for such a low left-right breaking scale are discussed. It is shown that in the constrained version of this model radiative breaking of the gauge symmetries is possible and a SM-like Higgs is obtained. Additional CP-even scalars of a similar mass or even much lighter are possible. The expected mass hierarchies for the supersymmetric states differ clearly from those of the constrained MSSM. In particular, the lightest down-type squark, which is a mixture of the sbottom and extra vector-like states, is always lighter than the stop. We also comment on the model's capability to explain current anomalies observed at the LHC.
Cosmogenic photons strongly constrain UHECR source models
Directory of Open Access Journals (Sweden)
van Vliet Arjen
2017-01-01
Full Text Available With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT’s IGRB, as long as their number density is not strongly peaked at recent times.
Global marine primary production constrains fisheries catches.
Chassot, Emmanuel; Bonhommeau, Sylvain; Dulvy, Nicholas K; Mélin, Frédéric; Watson, Reg; Gascuel, Didier; Le Pape, Olivier
2010-04-01
Primary production must constrain the amount of fish and invertebrates available to expanding fisheries; however the degree of limitation has only been demonstrated at regional scales to date. Here we show that phytoplanktonic primary production, estimated from an ocean-colour satellite (SeaWiFS), is related to global fisheries catches at the scale of Large Marine Ecosystems, while accounting for temperature and ecological factors such as ecosystem size and type, species richness, animal body size, and the degree and nature of fisheries exploitation. Indeed we show that global fisheries catches since 1950 have been increasingly constrained by the amount of primary production. The primary production appropriated by current global fisheries is 17-112% higher than that appropriated by sustainable fisheries. Global primary production appears to be declining, in some part due to climate variability and change, with consequences for the near future fisheries catches.
CONSTRAINED SPECTRAL CLUSTERING FOR IMAGE SEGMENTATION
Sourati, Jamshid; Brooks, Dana H.; Dy, Jennifer G.; Erdogmus, Deniz
2013-01-01
Constrained spectral clustering with affinity propagation in its original form is not practical for large scale problems like image segmentation. In this paper we employ novelty selection sub-sampling strategy, besides using efficient numerical eigen-decomposition methods to make this algorithm work efficiently for images. In addition, entropy-based active learning is also employed to select the queries posed to the user more wisely in an interactive image segmentation framework. We evaluate the algorithm on general and medical images to show that the segmentation results will improve using constrained clustering even if one works with a subset of pixels. Furthermore, this happens more efficiently when pixels to be labeled are selected actively. PMID:24466500
Doubly Constrained Robust Blind Beamforming Algorithm
Directory of Open Access Journals (Sweden)
Xin Song
2013-01-01
Full Text Available We propose doubly constrained robust least-squares constant modulus algorithm (LSCMA to solve the problem of signal steering vector mismatches via the Bayesian method and worst-case performance optimization, which is based on the mismatches between the actual and presumed steering vectors. The weight vector is iteratively updated with penalty for the worst-case signal steering vector by the partial Taylor-series expansion and Lagrange multiplier method, in which the Lagrange multipliers can be optimally derived and incorporated at each step. A theoretical analysis for our proposed algorithm in terms of complexity cost, convergence performance, and SINR performance is presented in this paper. In contrast to the linearly constrained LSCMA, the proposed algorithm provides better robustness against the signal steering vector mismatches, yields higher signal captive performance, improves greater array output SINR, and has a lower computational cost. The simulation results confirm the superiority of the proposed algorithm on beampattern control and output SINR enhancement.
How peer-review constrains cognition
DEFF Research Database (Denmark)
Cowley, Stephen
2015-01-01
Peer-review is neither reliable, fair, nor a valid basis for predicting ‘impact’: as quality control, peer-review is not fit for purpose. Endorsing the consensus, I offer a reframing: while a normative social process, peer-review also shapes the writing of a scientific paper. In so far...... as ‘cognition’ describes enabling conditions for flexible behavior, the practices of peer-review thus constrain knowledge-making. To pursue cognitive functions of peer-review, however, manuscripts must be seen as ‘symbolizations’, replicable patterns that use technologically enabled activity. On this bio......-cognitive view, peer-review constrains knowledge-making by writers, editors, reviewers. Authors are prompted to recursively re-aggregate symbolizations to present what are deemed acceptable knowledge claims. How, then, can recursive re-embodiment be explored? In illustration, I sketch how the paper’s own content...
Constraining neutron star matter with Quantum Chromodynamics
Kurkela, Aleksi; Schaffner-Bielich, Jurgen; Vuorinen, Aleksi
2014-01-01
In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount --- or even presence --- of quark matter inside the stars.
Constraining neutron star matter with quantum chromodynamics
Energy Technology Data Exchange (ETDEWEB)
Kurkela, Aleksi [Physics Department, Theory Unit, CERN, CH-1211 Genève 23 (Switzerland); Fraga, Eduardo S.; Schaffner-Bielich, Jürgen [Institute for Theoretical Physics, Goethe University, D-60438 Frankfurt am Main (Germany); Vuorinen, Aleksi [Department of Physics and Helsinki Institute of Physics, P.O. Box 64, FI-00014 University of Helsinki (Finland)
2014-07-10
In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount—or even presence—of quark matter inside the stars.
Constraining Neutron Star Matter with Quantum Chromodynamics
Kurkela, Aleksi; Fraga, Eduardo S.; Schaffner-Bielich, Jürgen; Vuorinen, Aleksi
2014-07-01
In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount—or even presence—of quark matter inside the stars.
Optimal constrained layer damping with partial coverage
Marcelin, J.-L.; Trompette, Ph.; Smati, A.
1992-12-01
This paper deals with the optimal damping of beams constrained by viscoelastic layers when only one or several portions of the beam are covered. An efficient finite element model for dynamic analysis of such beams is used. The design variables are the dimensions and prescribed locations of the viscoelastic layers and the objective is the maximum viscoelastic damping factor. The method for nonlinear programming in structural optimization is the so-called method of moving asymptotes.
Synthesis of constrained analogues of tryptophan
Directory of Open Access Journals (Sweden)
Elisabetta Rossi
2015-10-01
Full Text Available A Lewis acid-catalysed diastereoselective [4 + 2] cycloaddition of vinylindoles and methyl 2-acetamidoacrylate, leading to methyl 3-acetamido-1,2,3,4-tetrahydrocarbazole-3-carboxylate derivatives, is described. Treatment of the obtained cycloadducts under hydrolytic conditions results in the preparation of a small library of compounds bearing the free amino acid function at C-3 and pertaining to the class of constrained tryptophan analogues.
Capacity constrained assignment in spatial databases
DEFF Research Database (Denmark)
U, Leong Hou; Yiu, Man Lung; Mouratidis, Kyriakos;
2008-01-01
Given a point set P of customers (e.g., WiFi receivers) and a point set Q of service providers (e.g., wireless access points), where each q 2 Q has a capacity q.k, the capacity constrained assignment (CCA) is a matching M Q × P such that (i) each point q 2 Q (p 2 P) appears at most k times (at most...
CONSTRAINED SPECTRAL CLUSTERING FOR IMAGE SEGMENTATION
Sourati, Jamshid; Brooks, Dana H.; Dy, Jennifer G.; Erdogmus, Deniz
2012-01-01
Constrained spectral clustering with affinity propagation in its original form is not practical for large scale problems like image segmentation. In this paper we employ novelty selection sub-sampling strategy, besides using efficient numerical eigen-decomposition methods to make this algorithm work efficiently for images. In addition, entropy-based active learning is also employed to select the queries posed to the user more wisely in an interactive image segmentation framework. We evaluate ...
Constraining RRc candidates using SDSS colours
Bányai, E; Molnár, L; Dobos, L; Szabó, R
2016-01-01
The light variations of first-overtone RR Lyrae stars and contact eclipsing binaries can be difficult to distinguish. The Catalina Periodic Variable Star catalog contains several misclassified objects, despite the classification efforts by Drake et al. (2014). They used metallicity and surface gravity derived from spectroscopic data (from the SDSS database) to rule out binaries. Our aim is to further constrain the catalog using SDSS colours to estimate physical parameters for stars that did not have spectroscopic data.
Cardinality constrained portfolio selection via factor models
Monge, Juan Francisco
2017-01-01
In this paper we propose and discuss different 0-1 linear models in order to solve the cardinality constrained portfolio problem by using factor models. Factor models are used to build portfolios to track indexes, together with other objectives, also need a smaller number of parameters to estimate than the classical Markowitz model. The addition of the cardinality constraints limits the number of securities in the portfolio. Restricting the number of securities in the portfolio allows us to o...
HCV management in resource-constrained countries.
Lim, Seng Gee
2017-02-21
With the arrival of all-oral directly acting antiviral (DAA) therapy with high cure rates, the promise of hepatitis C virus (HCV) eradication is within closer reach. The availability of generic DAAs has improved access to countries with constrained resources. However, therapy is only one component of the HCV care continuum, which is the framework for HCV management from identifying patients to cure. The large number of undiagnosed HCV cases is the biggest concern, and strategies to address this are needed, as risk factor screening is suboptimal, detecting HCV confirmation through either reflex HCV RNA screening or ideally a sensitive point of care test are needed. HCV notification (e.g., Australia) may improve diagnosis (proportion of HCV diagnosed is 75%) and may lead to benefits by increasing linkage to care, therapy and cure. Evaluations for cirrhosis using non-invasive markers are best done with a biological panel, but they are only moderately accurate. In resource-constrained settings, only generic HCV medications are available, and a combination of sofosbuvir, ribavirin, ledipasvir or daclatasvir provides sufficient efficacy for all genotypes, but this is likely to be replaced with pangenetypic regimens such as sofosbuvir/velpatasvir and glecaprevir/pibrentaasvir. In conclusion, HCV management in resource-constrained settings is challenging on multiple fronts because of the lack of infrastructure, facilities, trained manpower and equipment. However, it is still possible to make a significant impact towards HCV eradication through a concerted effort by individuals and national organisations with domain expertise in this area.
An English language interface for constrained domains
Page, Brenda J.
1989-01-01
The Multi-Satellite Operations Control Center (MSOCC) Jargon Interpreter (MJI) demonstrates an English language interface for a constrained domain. A constrained domain is defined as one with a small and well delineated set of actions and objects. The set of actions chosen for the MJI is from the domain of MSOCC Applications Executive (MAE) Systems Test and Operations Language (STOL) directives and contains directives for signing a cathode ray tube (CRT) on or off, calling up or clearing a display page, starting or stopping a procedure, and controlling history recording. The set of objects chosen consists of CRTs, display pages, STOL procedures, and history files. Translation from English sentences to STOL directives is done in two phases. In the first phase, an augmented transition net (ATN) parser and dictionary are used for determining grammatically correct parsings of input sentences. In the second phase, grammatically typed sentences are submitted to a forward-chaining rule-based system for interpretation and translation into equivalent MAE STOL directives. Tests of the MJI show that it is able to translate individual clearly stated sentences into the subset of directives selected for the prototype. This approach to an English language interface may be used for similarly constrained situations by modifying the MJI's dictionary and rules to reflect the change of domain.
Constraining the mass of the Local Group
Carlesi, Edoardo; Hoffman, Yehuda; Sorce, Jenny G.; Gottlöber, Stefan
2017-03-01
The mass of the Local Group (LG) is a crucial parameter for galaxy formation theories. However, its observational determination is challenging - its mass budget is dominated by dark matter that cannot be directly observed. To meet this end, the posterior distributions of the LG and its massive constituents have been constructed by means of constrained and random cosmological simulations. Two priors are assumed - the Λ cold dark matter model that is used to set up the simulations, and an LG model that encodes the observational knowledge of the LG and is used to select LG-like objects from the simulations. The constrained simulations are designed to reproduce the local cosmography as it is imprinted on to the Cosmicflows-2 data base of velocities. Several prescriptions are used to define the LG model, focusing in particular on different recent estimates of the tangential velocity of M31. It is found that (a) different vtan choices affect the peak mass values up to a factor of 2, and change mass ratios of MM31 to MMW by up to 20 per cent; (b) constrained simulations yield more sharply peaked posterior distributions compared with the random ones; (c) LG mass estimates are found to be smaller than those found using the timing argument; (d) preferred Milky Way masses lie in the range of (0.6-0.8) × 1012 M⊙; whereas (e) MM31 is found to vary between (1.0-2.0) × 1012 M⊙, with a strong dependence on the vtan values used.
Constraining Source Redshift Distributions with Gravitational Lensing
Wittman, D
2012-01-01
We introduce a new method for constraining the redshift distribution of a set of galaxies, using weak gravitational lensing shear. Instead of using observed shears and redshifts to constrain cosmological parameters, we ask how well the shears around clusters can constrain the redshifts, assuming fixed cosmological parameters. This provides a check on photometric redshifts, independent of source spectral energy distribution properties and therefore free of confounding factors such as misidentification of spectral breaks. We find that ~40 massive ($\\sigma_v=1200$ km/s) cluster lenses are sufficient to determine the fraction of sources in each of six coarse redshift bins to ~11%, given weak (20%) priors on the masses of the highest-redshift lenses, tight (5%) priors on the masses of the lowest-redshift lenses, and only modest (20-50%) priors on calibration and evolution effects. Additional massive lenses drive down uncertainties as $N_{lens}^0.5$, but the improvement slows as one is forced to use lenses further ...
The canonical equilibrium of constrained molecular models
Echenique, Pablo; García-Risueño, Pablo
2011-01-01
In order to increase the efficiency of the computer simulation of biological molecules, it is very common to impose holonomic constraints on the fastest degrees of freedom; normally bond lengths, but also possibly bond angles. However, as any other element that affects the physical model, the imposition of constraints must be assessed from the point of view of accuracy: both the dynamics and the equilibrium statistical mechanics are model-dependent, and they will be changed if constraints are used. In this review, we investigate the accuracy of constrained models at the level of the equilibrium statistical mechanics distributions produced by the different dynamics. We carefully derive the canonical equilibrium distributions of both the constrained and unconstrained dynamics, comparing the two of them by means of a "stiff" approximation to the latter. We do so both in the case of flexible and hard constraints, i.e., when the value of the constrained coordinates depends on the conformation and when it is a cons...
Egg Production Constrains Chemical Defenses in a Neotropical Arachnid
Nazareth, Taís M.; Machado, Glauco
2015-01-01
Female investment in large eggs increases the demand for fatty acids, which are allocated for yolk production. Since the biosynthetic pathway leading to fatty acids uses the same precursors used in the formation of polyketides, allocation trade-offs are expected to emerge. Therefore, egg production should constrain the investment in chemical defenses based on polyketides, such as benzoquinones. We tested this hypothesis using the harvestman Acutiosoma longipes, which produces large eggs and releases benzoquinones as chemical defense. We predicted that the amount of secretion released by ovigerous females (OFs) would be smaller than that of non-ovigerous females (NOF). We also conducted a series of bioassays in the field and in the laboratory to test whether egg production renders OFs more vulnerable to predation. OFs produce less secretion than NOFs, which is congruent with the hypothesis that egg production constrains the investment in chemical defenses. Results of the bioassays show that the secretion released by OFs is less effective in deterring potential predators (ants and spiders) than the secretion released by NOFs. In conclusion, females allocate resources to chemical defenses in a way that preserves a primary biological function related to reproduction. However, the trade-off between egg and secretion production makes OFs vulnerable to predators. We suggest that egg production is a critical moment in the life of harvestman females, representing perhaps the highest cost of reproduction in the group. PMID:26331946
Constraining neutron star tidal Love numbers with gravitational wave detectors
Flanagan, Eanna E
2007-01-01
We quantify the ability of ground-based gravitational wave detectors to constrain the nuclear equation of state using the early, low frequency portion of the signal of detected neutron star - neutron star (NS-NS) inspirals. In this early adiabatic regime, the influence of a NS's internal structure on the phase of the waveform depends only on a single parameter lambda of the star related to its tidal Love number, namely the ratio of the induced quadrupole moment to the perturbing tidal gravitational field. We restrict attention to gravitational wave frequencies smaller than a cutoff frequency of 400 Hz. In this domain, f-mode frequency dependent corrections to the internal-structure signal are less than 3%, and higher order multipole corrections are less than 5%, for NS models with f-mode frequencies greater than 1 kHz. For an inspiral of two non-spinning 1.4 solar mass NSs at a signal-to-noise ratio of 20, LIGO I (LIGO II) detectors will be able to constrain lambda to lambda < 1.3 (3.3) 10^(37) g cm^2 s^2 ...
Kiemeneij, Ferdinand
2015-11-01
In order to obviate double arterial access for bi-coronary visualization during transradial intervention of chronic total coronary occlusions, a novel technique was used. A 3-in-6 mother-and-child technique was applied in which a 3 Fr intracoronary catheter was advanced via a 6 Fr guide into the artery supplying collaterals to the distal occluded segment of the right coronary artery (RCA). The same guide was used, with the 3 Fr catheter in situ, to visualize the occluded target vessel. With double contrast injections, the guidewire could be guided through the RCA occlusion while the intraluminal position could be visualized and confirmed. This was followed by successful drug-eluting stent implantation. This method to visualize both coronary arteries simultaneously is named the "Chameleon's technique."
The recursion operator for a constrained CKP hierarchy
Li, Chuanzhong; He, Jingsong; Cheng, Yi
2010-01-01
This paper gives a recursion operator for a 1-constrained CKP hierarchy, and by the recursion operator it proves that the 1-constrained CKP hierarchy can be reduced to the mKdV hierarchy under condition $q=r$.
Technical Note: Methods for interval constrained atmospheric inversion of methane
Directory of Open Access Journals (Sweden)
J. Tang
2010-08-01
Full Text Available Three interval constrained methods, including the interval constrained Kalman smoother, the interval constrained maximum likelihood ensemble smoother and the interval constrained ensemble Kalman smoother are developed to conduct inversions of atmospheric trace gas methane (CH_{4}. The negative values of fluxes in an unconstrained inversion are avoided in the constrained inversion. In a multi-year inversion experiment using pseudo observations derived from a forward transport simulation with known fluxes, the interval constrained fixed-lag Kalman smoother presents the best results, followed by the interval constrained fixed-lag ensemble Kalman smoother and the interval constrained maximum likelihood ensemble Kalman smoother. Consistent uncertainties are obtained for the posterior fluxes with these three methods. This study provides alternatives of the variable transform method to deal with interval constraints in atmospheric inversions.
The recursion operator for a constrained CKP hierarchy
Li, Chuanzhong; Tian, Kelei; He, Jingsong; Cheng, Yi
2010-01-01
This paper gives a recursion operator for a 1-constrained CKP hierarchy, and by the recursion operator it proves that the 1-constrained CKP hierarchy can be reduced to the mKdV hierarchy under condition $q=r$.
21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Wrist joint polymer constrained prosthesis. 888.3780 Section 888.3780 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made...
21 CFR 888.3230 - Finger joint polymer constrained prosthesis.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint polymer constrained prosthesis. 888... constrained prosthesis. (a) Identification. A finger joint polymer constrained prosthesis is a device intended... generic type of device includes prostheses that consist of a single flexible across-the-joint...
Cascading Constrained 2-D Arrays using Periodic Merging Arrays
DEFF Research Database (Denmark)
Forchhammer, Søren; Laursen, Torben Vaarby
2003-01-01
We consider a method for designing 2-D constrained codes by cascading finite width arrays using predefined finite width periodic merging arrays. This provides a constructive lower bound on the capacity of the 2-D constrained code. Examples include symmetric RLL and density constrained codes....... Numerical results for the capacities are presented....
Constraining gravity with hadron physics: neutron stars, modified gravity and gravitational waves
Llanes-Estrada, Felipe J
2016-01-01
The finding of Gravitational Waves by the aLIGO scientific and VIRGO collaborations opens opportunities to better test and understand strong interactions, both nuclear-hadronic and gravitational. Assuming General Relativity holds, one can constrain hadron physics at a neutron star. But precise knowledge of the Equation of State and transport properties in hadron matter can also be used to constrain the theory of gravity itself. I review a couple of these opportunities in the context of modified f(R) gravity, the maximum mass of neutron stars, and progress in the Equation of State of neutron matter from the chiral effective field theory of QCD.
Constraining gravity with hadron physics: neutron stars, modified gravity and gravitational waves
Llanes-Estrada, Felipe J.
2017-03-01
The finding of Gravitational Waves (GW) by the aLIGO scientific and VIRGO collaborations opens opportunities to better test and understand strong interactions, both nuclear-hadronic and gravitational. Assuming General Relativity holds, one can constrain hadron physics at a neutron star. But precise knowledge of the Equation of State and transport properties in hadron matter can also be used to constrain the theory of gravity itself. I review a couple of these opportunities in the context of modified f (R) gravity, the maximum mass of neutron stars, and progress in the Equation of State of neutron matter from the chiral effective field theory of QCD.
Correspondence between constrained transport and vector potential methods for magnetohydrodynamics
Mocz, Philip
2017-01-01
We show that one can formulate second-order field- and flux-interpolated constrained transport/central difference (CT/CD) type methods as cell-centered magnetic vector potential schemes. We introduce four vector potential CTA/CDA schemes - three of which correspond to CT/CD methods of Tóth (2000) [1] and one of which is a new simple flux-CT-like scheme - where the centroidal vector potential is the primal update variable. These algorithms conserve a discretization of the ∇ ṡ B = 0 condition to machine precision and may be combined with shock-capturing Godunov type base schemes for magnetohydrodynamics. Recasting CT in terms of a centroidal vector potential allows for some simple generalizations of divergence-preserving methods to unstructured meshes, and potentially new directions to generalize CT schemes to higher-order.
Constrained Overcomplete Analysis Operator Learning for Cosparse Signal Modelling
Yaghoobi, Mehrdad; Gribonval, Remi; Davies, Mike E
2012-01-01
We consider the problem of learning a low-dimensional signal model from a collection of training samples. The mainstream approach would be to learn an overcomplete dictionary to provide good approximations of the training samples using sparse synthesis coefficients. This famous sparse model has a less well known counterpart, in analysis form, called the cosparse analysis model. In this new model, signals are characterised by their parsimony in a transformed domain using an overcomplete (linear) analysis operator. We propose to learn an analysis operator from a training corpus using a constrained optimisation framework based on L1 optimisation. The reason for introducing a constraint in the optimisation framework is to exclude trivial solutions. Although there is no final answer here for which constraint is the most relevant constraint, we investigate some conventional constraints in the model adaptation field and use the uniformly normalised tight frame (UNTF) for this purpose. We then derive a practical lear...
Geometric constrained variational calculus. III: The second variation (Part II)
Massa, Enrico; Luria, Gianvittorio; Pagani, Enrico
2016-03-01
The problem of minimality for constrained variational calculus is analyzed within the class of piecewise differentiable extremaloids. A fully covariant representation of the second variation of the action functional based on a family of local gauge transformations of the original Lagrangian is proposed. The necessity of pursuing a local adaptation process, rather than the global one described in [1] is seen to depend on the value of certain scalar attributes of the extremaloid, here called the corners’ strengths. On this basis, both the necessary and the sufficient conditions for minimality are worked out. In the discussion, a crucial role is played by an analysis of the prolongability of the Jacobi fields across the corners. Eventually, in the appendix, an alternative approach to the concept of strength of a corner, more closely related to Pontryagin’s maximum principle, is presented.
QCD strings as constrained grassmannian sigma model
Viswanathan, K S; Viswanathan, K S; Parthasarathy, R
1995-01-01
We present calculations for the effective action of string world sheet in R3 and R4 utilizing its correspondence with the constrained Grassmannian sigma model. Minimal surfaces describe the dynamics of open strings while harmonic surfaces describe that of closed strings. The one-loop effective action for these are calculated with instanton and anti-instanton background, reprsenting N-string interactions at the tree level. The effective action is found to be the partition function of a classical modified Coulomb gas in the confining phase, with a dynamically generated mass gap.
Can Neutron stars constrain Dark Matter?
DEFF Research Database (Denmark)
Kouvaris, Christoforos; Tinyakov, Peter
2010-01-01
We argue that observations of old neutron stars can impose constraints on dark matter candidates even with very small elastic or inelastic cross section, and self-annihilation cross section. We find that old neutron stars close to the galactic center or in globular clusters can maintain a surface...... temperature that could in principle be detected. Due to their compactness, neutron stars can acrete WIMPs efficiently even if the WIMP-to-nucleon cross section obeys the current limits from direct dark matter searches, and therefore they could constrain a wide range of dark matter candidates....
Energetic Materials Optimization via Constrained Search
2015-06-01
space.18–20 LCAP and VP-DFT interpolate continuously between the Hamiltonians of various chemical species. Furthermore, recently an investigation into...Computational Chemistry Protocol All quantum- mechanical computations were performed using Gaussian 09.24 All geometries were preoptimized with B3LYP/3-21G under...via nonnegative Lagrange multipliers λ ∈ R3+ for the 3 constraints to the augmented Lagrangian function L(x, λ) := P (x) − λC(x) as a constrained min
Quantization of soluble classical constrained systems
Energy Technology Data Exchange (ETDEWEB)
Belhadi, Z. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Laboratoire de physique théorique, Faculté des sciences exactes, Université de Bejaia, 06000 Bejaia (Algeria); Menas, F. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Ecole Nationale Préparatoire aux Etudes d’ingéniorat, Laboratoire de physique, RN 5 Rouiba, Alger (Algeria); Bérard, A. [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France); Mohrbach, H., E-mail: herve.mohrbach@univ-lorraine.fr [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France)
2014-12-15
The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac’s formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way.
Neuroevolutionary Constrained Optimization for Content Creation
DEFF Research Database (Denmark)
Liapis, Antonios; Yannakakis, Georgios N.; Togelius, Julian
2011-01-01
and thruster types and topologies) independently of game physics and steering strategies. According to the proposed framework, the designer picks a set of requirements for the spaceship that a constrained optimizer attempts to satisfy. The constraint satisfaction approach followed is based on neuroevolution......; Compositional Pattern-Producing Networks (CPPNs) which represent the spaceship’s design are trained via a constraint-based evolutionary algorithm. Results obtained in a number of evolutionary runs using a set of constraints and objectives show that the generated spaceships perform well in movement, combat...
Charged particles constrained to a curved surface
Müller, Thomas
2012-01-01
We study the motion of charged particles constrained to arbitrary two-dimensional curved surfaces but interacting in three-dimensional space via the Coulomb potential. To speed-up the interaction calculations, we use the parallel compute capability of the Compute Unified Device Architecture (CUDA) of todays graphics boards. The particles and the curved surfaces are shown using the Open Graphics Library (OpenGL). The paper is intended to give graduate students, who have basic experiences with electrostatics and differential geometry, a deeper understanding in charged particle interactions and a short introduction how to handle a many particle system using parallel computing on a single home computer
Utility Constrained Energy Minimization In Aloha Networks
Khodaian, Amir Mahdi; Talebi, Mohammad S
2010-01-01
In this paper we consider the issue of energy efficiency in random access networks and show that optimizing transmission probabilities of nodes can enhance network performance in terms of energy consumption and fairness. First, we propose a heuristic power control method that improves throughput, and then we model the Utility Constrained Energy Minimization (UCEM) problem in which the utility constraint takes into account single and multi node performance. UCEM is modeled as a convex optimization problem and Sequential Quadratic Programming (SQP) is used to find optimal transmission probabilities. Numerical results show that our method can achieve fairness, reduce energy consumption and enhance lifetime of such networks.
Constraining Milky Way mass with Hypervelocity Stars
Fragione, Giacomo
2016-01-01
We show that hypervelocity stars (HVSs) ejected from the center of the Milky Way galaxy can be used to constrain the mass of its halo. The asymmetry in the radial velocity distribution of halo stars due to escaping HVSs depends on the halo potential (escape speed) as long as the round trip orbital time is shorter than the stellar lifetime. Adopting a characteristic HVS travel time of $300$ Myr, which corresponds to the average mass of main sequence HVSs ($3.2$ M$_{\\odot}$), we find that current data favors a mass for the Milky Way in the range $(1.2$-$1.7)\\times 10^{12} \\mathrm{M}_\\odot$.
Lifespan theorem for constrained surface diffusion flows
McCoy, James; Williams, Graham; 10.1007/s00209-010-0720-7
2012-01-01
We consider closed immersed hypersurfaces in $\\R^{3}$ and $\\R^4$ evolving by a class of constrained surface diffusion flows. Our result, similar to earlier results for the Willmore flow, gives both a positive lower bound on the time for which a smooth solution exists, and a small upper bound on a power of the total curvature during this time. By phrasing the theorem in terms of the concentration of curvature in the initial surface, our result holds for very general initial data and has applications to further development in asymptotic analysis for these flows.
Integrating job scheduling and constrained network routing
DEFF Research Database (Denmark)
Gamst, Mette
2010-01-01
This paper examines the NP-hard problem of scheduling jobs on resources such that the overall profit of executed jobs is maximized. Job demand must be sent through a constrained network to the resource before execution can begin. The problem has application in grid computing, where a number...... of geographically distributed resources connected through an optical network work together for solving large problems. A number of heuristics are proposed along with an exact solution approach based on Dantzig-Wolfe decomposition. The latter has some performance difficulties while the heuristics solve all instances...
Weight-Constrained Minimum Spanning Tree Problem
Henn, Sebastian Tobias
2007-01-01
In an undirected graph G we associate costs and weights to each edge. The weight-constrained minimum spanning tree problem is to find a spanning tree of total edge weight at most a given value W and minimum total costs under this restriction. In this thesis a literature overview on this NP-hard problem, theoretical properties concerning the convex hull and the Lagrangian relaxation are given. We present also some in- and exclusion-test for this problem. We apply a ranking algorithm and the me...
Zeya, Bushra; Arjuman, Albina; Chandra, Nimai Chand
2016-08-16
LOX-1, one of the main receptors for oxLDL, is found mainly on the surface of endothelial cells. It is a multifacet 52 kDa type II transmembrane protein that structurally belongs to the C-type lectin family. It exists with short intracellular N-terminal and long extracellular C-terminal hydrophilic domains separated by a hydrophobic domain of 26 amino acids. LOX-1 acts like a bifunctional receptor either showing pro-atherogenicity by activating the NFκB-mediated down signaling cascade for gene activation of pro-inflammatory molecules or playing an atheroprotective agent by receptor-mediated uptake of oxLDL in the presence of an anti-inflammatory molecule like IL-10. Mildly, moderately, and highly oxidized LDL show their characteristic features upon LOX-1 activation and its ligand binding indenture. The polymorphic LOX-1 genes are intensively associated with increased susceptibility to myocardial diseases. The splicing variant LOX IN dimerizes with the native form of LOX-1 and protects cells from damage by oxidized LDL. In the developing field of regenerating medicine, LOX-1 is a potential target for therapeutic intervention.
Experimental investigation of a self-sensing active constrained layer damping treatment
Yellin, Jessica M.; Shen, I. Y.
1996-05-01
A variational formulation of active constrained layer (ACL) damping treatments has indicated that the power dissipated through the active damping is the product of the electric field and the axial velocity of the piezoelectric constraining layer at the boundaries. This feature, unique to this formulation, suggests that a self-sensing and actuating piezoelectric constraining layer using rate of strain feedback may be an appropriate method of dissipating vibration energy with less instability, since the sensor and actuator are truly collocated. A partial ACL damping treatment design for an Euler-Bernoulli beam using a self-sensing actuator (SSA) as the active layer has been developed. The open loop transfer functions of the treated beam given by the SSA rate of strain circuit show great similarity to transfer functions taken from a reference sensor laminated directly to the beam. It has been shown experimentally that this beam treatment significantly increased the damping coefficient of the first mode in closed loop.
The Performance Comparisons between the Unconstrained and Constrained Equalization Algorithms
Institute of Scientific and Technical Information of China (English)
HE Zhong-qiu; LI Dao-ben
2003-01-01
This paper proposes two unconstrained algorithms, the Steepest Decent (SD) algorithm and the Conjugate Gradient (CG) algorithm, based on a superexcellent cost function [1～3]. At the same time, two constrained algorithms which include the Constrained Steepest Decent (CSD) algorithm and the Constrained Conjugate Gradient algorithm (CCG) are deduced subject to a new constrain condition. They are both implemented in unitary transform domain. The computational complexities of the constrained algorithms are compared to those of the unconstrained algorithms. Resulting simulations show their performance comparisons.
Constrained Simulation of the Bullet Cluster
Lage, Craig
2013-01-01
In this work, we report on a detailed simulation of the Bullet Cluster (1E0657-56) merger, including magnetohydrodynamics, plasma cooling, and adaptive mesh refinement. We constrain the simulation with data from gravitational lensing reconstructions and 0.5 - 2 keV Chandra X-ray flux map, then compare the resulting model to higher energy X-ray fluxes, the extracted plasma temperature map, Sunyaev-Zel'dovich effect measurements, and cluster halo radio emission. We constrain the initial conditions by minimizing the chi-squared figure of merit between the full 2D observational data sets and the simulation, rather than comparing only a few features such as the location of subcluster centroids, as in previous studies. A simple initial configuration of two triaxial clusters with NFW dark matter profiles and physically reasonable plasma profiles gives a good fit to the current observational morphology and X-ray emissions of the merging clusters. There is no need for unconventional physics or extreme infall velocitie...
Constraining dark matter through 21-cm observations
Valdés, M.; Ferrara, A.; Mapelli, M.; Ripamonti, E.
2007-05-01
Beyond reionization epoch cosmic hydrogen is neutral and can be directly observed through its 21-cm line signal. If dark matter (DM) decays or annihilates, the corresponding energy input affects the hydrogen kinetic temperature and ionized fraction, and contributes to the Lyα background. The changes induced by these processes on the 21-cm signal can then be used to constrain the proposed DM candidates, among which we select the three most popular ones: (i) 25-keV decaying sterile neutrinos, (ii) 10-MeV decaying light dark matter (LDM) and (iii) 10-MeV annihilating LDM. Although we find that the DM effects are considerably smaller than found by previous studies (due to a more physical description of the energy transfer from DM to the gas), we conclude that combined observations of the 21-cm background and of its gradient should be able to put constrains at least on LDM candidates. In fact, LDM decays (annihilations) induce differential brightness temperature variations with respect to the non-decaying/annihilating DM case up to ΔδTb = 8 (22) mK at about 50 (15) MHz. In principle, this signal could be detected both by current single-dish radio telescopes and future facilities as Low Frequency Array; however, this assumes that ionospheric, interference and foreground issues can be properly taken care of.
Constrained Metric Learning by Permutation Inducing Isometries.
Bosveld, Joel; Mahmood, Arif; Huynh, Du Q; Noakes, Lyle
2016-01-01
The choice of metric critically affects the performance of classification and clustering algorithms. Metric learning algorithms attempt to improve performance, by learning a more appropriate metric. Unfortunately, most of the current algorithms learn a distance function which is not invariant to rigid transformations of images. Therefore, the distances between two images and their rigidly transformed pair may differ, leading to inconsistent classification or clustering results. We propose to constrain the learned metric to be invariant to the geometry preserving transformations of images that induce permutations in the feature space. The constraint that these transformations are isometries of the metric ensures consistent results and improves accuracy. Our second contribution is a dimension reduction technique that is consistent with the isometry constraints. Our third contribution is the formulation of the isometry constrained logistic discriminant metric learning (IC-LDML) algorithm, by incorporating the isometry constraints within the objective function of the LDML algorithm. The proposed algorithm is compared with the existing techniques on the publicly available labeled faces in the wild, viewpoint-invariant pedestrian recognition, and Toy Cars data sets. The IC-LDML algorithm has outperformed existing techniques for the tasks of face recognition, person identification, and object classification by a significant margin.
Constraining the halo mass function with observations
Castro, Tiago; Marra, Valerio; Quartin, Miguel
2016-12-01
The abundances of dark matter haloes in the universe are described by the halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behaviour through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper, we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of Type Ia supernovae. Our results show that Dark Energy Survey is capable of putting the first meaningful constraints on the HMF, while both Euclid and J-PAS (Javalambre-Physics of the Accelerated Universe Astrophysical Survey) can give stronger constraints, comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even more important for measuring the HMF than for constraining the cosmological parameters, and can vastly improve the determination of the HMF. Measuring the HMF could thus be used to cross-check simulations and their implementation of baryon physics. It could even, if deviations cannot be accounted for, hint at new physics.
Changes in epistemic frameworks: Random or constrained?
Directory of Open Access Journals (Sweden)
Ananka Loubser
2012-11-01
Full Text Available Since the emergence of a solid anti-positivist approach in the philosophy of science, an important question has been to understand how and why epistemic frameworks change in time, are modified or even substituted. In contemporary philosophy of science three main approaches to framework-change were detected in the humanist tradition:1. In both the pre-theoretical and theoretical domains changes occur according to a rather constrained, predictable or even pre-determined pattern (e.g. Holton.2. Changes occur in a way that is more random or unpredictable and free from constraints (e.g. Kuhn, Feyerabend, Rorty, Lyotard.3. Between these approaches, a middle position can be found, attempting some kind of synthesis (e.g. Popper, Lakatos.Because this situation calls for clarification and systematisation, this article in fact tried to achieve more clarity on how changes in pre-scientific frameworks occur, as well as provided transcendental criticism of the above positions. This article suggested that the above-mentioned positions are not fully satisfactory, as change and constancy are not sufficiently integrated. An alternative model was suggested in which changes in epistemic frameworks occur according to a pattern, neither completely random nor rigidly constrained, which results in change being dynamic but not arbitrary. This alternative model is integral, rather than dialectical and therefore does not correspond to position three.
Constraining the braneworld with gravitational wave observations
McWilliams, Sean T
2009-01-01
Braneworld models containing large extra dimensions may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model, the asymptotic AdS radius of curvature of the extra dimension supports a single bound state of the massless graviton on the brane, thereby avoiding gross violations of Newton's law. However, one possible consequence of this model is an enormous increase in the amount of Hawking radiation emitted by black holes. This consequence has been employed by other authors to attempt to constrain the AdS radius of curvature through the observation of black holes. I present two novel methods for constraining the AdS curvature. The first method results from the effect of this enhanced mass loss on the event rate for extreme mass ratio inspirals (EMRIs) detected by the space-based LISA interferometer. The second method results from the observation of an individually resolvable galactic black hole binary with LISA. I show that the ...
Constraining the mass of the Local Group
Carlesi, Edoardo; Sorce, Jenny G; Gottlöber, Stefan
2016-01-01
The mass of the Local Group (LG) is a crucial parameter for galaxy formation theories. However, its observational determination is challenging - its mass budget is dominated by dark matter which cannot be directly observed. To meet this end the posterior distributions of the LG and its massive constituents have been constructed by means of constrained and random cosmological simulations. Two priors are assumed - the LCDM model that is used to set up the simulations and a LG model,which encodes the observational knowledge of the LG and is used to select LG-like objects from the simulations. The constrained simulations are designed to reproduce the local cosmography as it is imprinted onto the Cosmicflows-2 database of velocities. Several prescriptions are used to define the LG model, focusing in particular on different recent estimates of the tangential velocity of M31. It is found that (a) different $v_{tan}$ choices affect the peak mass values up to a factor of 2, and change mass ratios of $M_{M31}$ to $M_{M...
Nonstationary sparsity-constrained seismic deconvolution
Sun, Xue-Kai; Sam, Zandong Sun; Xie, Hui-Wen
2014-12-01
The Robinson convolution model is mainly restricted by three inappropriate assumptions, i.e., statistically white reflectivity, minimum-phase wavelet, and stationarity. Modern reflectivity inversion methods (e.g., sparsity-constrained deconvolution) generally attempt to suppress the problems associated with the first two assumptions but often ignore that seismic traces are nonstationary signals, which undermines the basic assumption of unchanging wavelet in reflectivity inversion. Through tests on reflectivity series, we confirm the effects of nonstationarity on reflectivity estimation and the loss of significant information, especially in deep layers. To overcome the problems caused by nonstationarity, we propose a nonstationary convolutional model, and then use the attenuation curve in log spectra to detect and correct the influences of nonstationarity. We use Gabor deconvolution to handle nonstationarity and sparsity-constrained deconvolution to separating reflectivity and wavelet. The combination of the two deconvolution methods effectively handles nonstationarity and greatly reduces the problems associated with the unreasonable assumptions regarding reflectivity and wavelet. Using marine seismic data, we show that correcting nonstationarity helps recover subtle reflectivity information and enhances the characterization of details with respect to the geological record.
Nguyen, Q. H.; Choi, S. B.
2012-01-01
This research focuses on optimal design of different types of magnetorheological brakes (MRBs), from which an optimal selection of MRB types is identified. In the optimization, common types of MRB such as disc-type, drum-type, hybrid-types, and T-shaped type are considered. The optimization problem is to find the optimal value of significant geometric dimensions of the MRB that can produce a maximum braking torque. The MRB is constrained in a cylindrical volume of a specific radius and length. After a brief description of the configuration of MRB types, the braking torques of the MRBs are derived based on the Herschel-Bulkley model of the MR fluid. The optimal design of MRBs constrained in a specific cylindrical volume is then analysed. The objective of the optimization is to maximize the braking torque while the torque ratio (the ratio of maximum braking torque and the zero-field friction torque) is constrained to be greater than a certain value. A finite element analysis integrated with an optimization tool is employed to obtain optimal solutions of the MRBs. Optimal solutions of MRBs constrained in different volumes are obtained based on the proposed optimization procedure. From the results, discussions on the optimal selection of MRB types depending on constrained volumes are given.
A self-constrained inversion of magnetic data based on correlation method
Sun, Shida; Chen, Chao
2016-12-01
Geologically-constrained inversion is a powerful method for producing geologically reasonable solutions in geophysical exploration problems. But in many cases, except the observed geophysical data to be inverted, the geological information is insufficiently available for improving reliability of recovered models. To deal with these situations, self-constraints extracted from preprocessing observed data have been applied to constrain the inversion. In this paper, we present a self-constrained inversion method based on correlation method. In our approach the correlation results are first obtained by calculating the cross-correlation between theoretical data and horizontal gradients of the observed data. Subsequently, we propose two specific strategies to extract the spatial variation from the correlation results and then translate them into spatial weighting functions. Incorporating the spatial weighting functions into the model objective function, we obtain self-constrained solutions with higher reliability. We presented two synthetic and one field magnetic data example to test the validity. All results demonstrate that the solution from our self-constrained inversion can delineate the geological bodies with clearer boundaries and much more concentrated physical property.
Constraining Gravity at Large Scales with Clusters of Galaxies
Rapetti, D.; Cataneo, M.; Schmidt, F.; Lombriser, L.; Li, B.; Mantz, A.; Allen, S.; Applegate, D.; Kelly, P.; von der Linden, A.; Morris, R. G.
2017-01-01
I will present the most recent constraints on f(R) modifications of gravity from the abundance of massive galaxy clusters. Our analysis self-consistently and simultaneously incorporates survey, observable-mass scaling relations, as well as weak gravitational lensing data to accurately calibrate the absolute cluster mass scale. Using this advanced cluster analysis in combination with CMB data, and other cosmological constraints, we obtain upper bounds on f(R) gravity that are about an order of magnitude tighter than those from such previous studies. The robustness of our results derives from our high quality cluster growth data out to redshifts z 0 . 5 , a tight control of systematic uncertainties, accounting for the covariance between all parameters, and the use of the full shape of the halo mass function (HMF) over the mass range of the data. Based on the current highest resolution N-body simulations, I will also describe our new modeling of the f(R) HMF. This includes novel corrections to capture key non-linear effects of the Chameleon screening mechanism that will allow us to obtain the next generation of cluster constraints on this model. DR is supported by an NPP Senior Fellowship at NASA ARC, administered by USRA under contract with NASA.
Porciani, Cristiano
2016-01-01
Constrained realisations of Gaussian random fields are used in cosmology to design special initial conditions for numerical simulations. We review this approach and its application to density peaks providing several worked-out examples. We then critically discuss the recent proposal to use constrained realisations to modify the linear density field within and around the Lagrangian patches that form dark-matter haloes. The ambitious concept is to forge `genetically modified' haloes with some desired properties after the non-linear evolution. We demonstrate that the original implementation of this method is not exact but approximate because it tacitly assumes that protohaloes sample a set of random points with a fixed mean overdensity. We show that carrying out a full genetic modification is a formidable and daunting task requiring a mathematical understanding of what determines the biased locations of protohaloes in the linear density field. We discuss approximate solutions based on educated guesses regarding ...
A moving mesh unstaggered constrained transport scheme for magnetohydrodynamics
Mocz, Philip; Pakmor, Rüdiger; Springel, Volker; Vogelsberger, Mark; Marinacci, Federico; Hernquist, Lars
2016-11-01
We present a constrained transport (CT) algorithm for solving the 3D ideal magnetohydrodynamic (MHD) equations on a moving mesh, which maintains the divergence-free condition on the magnetic field to machine-precision. Our CT scheme uses an unstructured representation of the magnetic vector potential, making the numerical method simple and computationally efficient. The scheme is implemented in the moving mesh code AREPO. We demonstrate the performance of the approach with simulations of driven MHD turbulence, a magnetized disc galaxy, and a cosmological volume with primordial magnetic field. We compare the outcomes of these experiments to those obtained with a previously implemented Powell divergence-cleaning scheme. While CT and the Powell technique yield similar results in idealized test problems, some differences are seen in situations more representative of astrophysical flows. In the turbulence simulations, the Powell cleaning scheme artificially grows the mean magnetic field, while CT maintains this conserved quantity of ideal MHD. In the disc simulation, CT gives slower magnetic field growth rate and saturates to equipartition between the turbulent kinetic energy and magnetic energy, whereas Powell cleaning produces a dynamically dominant magnetic field. Such difference has been observed in adaptive-mesh refinement codes with CT and smoothed-particle hydrodynamics codes with divergence-cleaning. In the cosmological simulation, both approaches give similar magnetic amplification, but Powell exhibits more cell-level noise. CT methods in general are more accurate than divergence-cleaning techniques, and, when coupled to a moving mesh can exploit the advantages of automatic spatial/temporal adaptivity and reduced advection errors, allowing for improved astrophysical MHD simulations.
Constraining the Inflationary Equation of State
Ackerman, Lotty; Kundu, Sandipan; Sivanandam, Navin
2010-01-01
We explore possible constraints on the inflationary equation state: p=w\\rho. While w must be close to -1 for those modes that contribute to the observed power spectrum, for those modes currently out of experimental reach, the constraints on w are much weaker, with only w<-1/3 as an a priori requirement. We find, however, that limits on the reheat temperature and the inflationary energy scale constrain w further, though there is still ample parameter space for a vastly different (accelerating) equation of state between the end of quasi-de Sitter inflation and the beginning of the radiation-dominated era. In the event that such an epoch of acceleration could be observed, we review the consequences for the primordial power spectrum.
Constraining the Cratering Chronology of Vesta
O'Brien, David P; Morbidelli, Alessandro; Bottke, William F; Schenk, Paul M; Russell, Christopher T; Raymond, Carol A
2014-01-01
Vesta has a complex cratering history, with ancient terrains as well as recent large impacts that have led to regional resurfacing. Crater counts can help constrain the relative ages of different units on Vesta's surface, but converting those crater counts to absolute ages requires a chronology function. We present a cratering chronology based on the best current models for the dynamical evolution of asteroid belt, and calibrate it to Vesta using the record of large craters on its surface. While uncertainties remain, our chronology function is broadly consistent with an ancient surface of Vesta as well as other constraints such as the bombardment history of the rest of the inner Solar System and the Ar-Ar age distribution of howardite, eucrite and diogenite (HED) meteorites from Vesta.
Database Transposition for Constrained (Closed) Pattern Mining
Jeudy, Baptiste
2009-01-01
Recently, different works proposed a new way to mine patterns in databases with pathological size. For example, experiments in genome biology usually provide databases with thousands of attributes (genes) but only tens of objects (experiments). In this case, mining the "transposed" database runs through a smaller search space, and the Galois connection allows to infer the closed patterns of the original database. We focus here on constrained pattern mining for those unusual databases and give a theoretical framework for database and constraint transposition. We discuss the properties of constraint transposition and look into classical constraints. We then address the problem of generating the closed patterns of the original database satisfying the constraint, starting from those mined in the "transposed" database. Finally, we show how to generate all the patterns satisfying the constraint from the closed ones.
Shape space exploration of constrained meshes
Yang, Yongliang
2011-01-01
We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc.
Remote gaming on resource-constrained devices
Reza, Waazim; Kalva, Hari; Kaufman, Richard
2010-08-01
Games have become important applications on mobile devices. A mobile gaming approach known as remote gaming is being developed to support games on low cost mobile devices. In the remote gaming approach, the responsibility of rendering a game and advancing the game play is put on remote servers instead of the resource constrained mobile devices. The games rendered on the servers are encoded as video and streamed to mobile devices. Mobile devices gather user input and stream the commands back to the servers to advance game play. With this solution, mobile devices with video playback and network connectivity can become game consoles. In this paper we present the design and development of such a system and evaluate the performance and design considerations to maximize the end user gaming experience.
Lagrange versus symplectic algorithm for constrained systems
Energy Technology Data Exchange (ETDEWEB)
Rothe, Heinz J; Rothe, Klaus D [Institut fuer Theoretische Physik - Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)
2003-02-14
The systematization of the purely Lagrangian approach to constrained systems in the form of an algorithm involves the iterative construction of a generalized Hessian matrix W taking a rectangular form. This Hessian will exhibit as many left zero modes as there are Lagrangian constraints in the theory. We apply this approach to a general Lagrangian in the first-order formulation and show how the seemingly overdetermined set of equations is solved for the velocities by suitably extending W to a rectangular matrix. As a byproduct we thereby demonstrate the equivalence of the Lagrangian approach to the traditional Dirac approach. By making use of this equivalence we show that a recently proposed symplectic algorithm does not necessarily reproduce the full constraint structure of the traditional Dirac algorithm.
Constrained sampling method for analytic continuation
Sandvik, Anders W.
2016-12-01
A method for analytic continuation of imaginary-time correlation functions (here obtained in quantum Monte Carlo simulations) to real-frequency spectral functions is proposed. Stochastically sampling a spectrum parametrized by a large number of δ functions, treated as a statistical-mechanics problem, it avoids distortions caused by (as demonstrated here) configurational entropy in previous sampling methods. The key development is the suppression of entropy by constraining the spectral weight to within identifiable optimal bounds and imposing a set number of peaks. As a test case, the dynamic structure factor of the S =1 /2 Heisenberg chain is computed. Very good agreement is found with Bethe ansatz results in the ground state (including a sharp edge) and with exact diagonalization of small systems at elevated temperatures.
Constraining the Porosities of Interstellar Dust Grains
Heng, Kevin
2009-01-01
We present theoretical calculations of the X-ray scattering properties of porous grain aggregates with olivine monomers. The small and large angle scattering properties of these aggregates are governed by the global structure and substructure of the grain, respectively. We construct two diagnostics, R_X and T_X, based on the optical and X-ray properties of the aggregates, and apply them to a Chandra measurement of the dust halo around the Galactic binary GX13+1. Grain aggregates with porosities higher than about 0.55 are ruled out. Future high-precision observations of X-ray dust haloes together with detailed modeling of the X-ray scattering properties of porous grain mixtures will further constrain the presence of porous grain aggregates in a given dust population.
Scheduling of resource-constrained projects
Klein, Robert
2000-01-01
Project management has become a widespread instrument enabling organizations to efficiently master the challenges of steadily shortening product life cycles, global markets and decreasing profit margins. With projects increasing in size and complexity, their planning and control represents one of the most crucial management tasks. This is especially true for scheduling, which is concerned with establishing execution dates for the sub-activities to be performed in order to complete the project. The ability to manage projects where resources must be allocated between concurrent projects or even sub-activities of a single project requires the use of commercial project management software packages. However, the results yielded by the solution procedures included are often rather unsatisfactory. Scheduling of Resource-Constrained Projects develops more efficient procedures, which can easily be integrated into software packages by incorporated programming languages, and thus should be of great interest for practiti...
Shape space exploration of constrained meshes
Yang, Yongliang
2011-12-12
We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc. © 2011 ACM.
Constrained Delaunay Triangulation for Ad Hoc Networks
Directory of Open Access Journals (Sweden)
D. Satyanarayana
2008-01-01
Full Text Available Geometric spanners can be used for efficient routing in wireless ad hoc networks. Computation of existing spanners for ad hoc networks primarily focused on geometric properties without considering network requirements. In this paper, we propose a new spanner called constrained Delaunay triangulation (CDT which considers both geometric properties and network requirements. The CDT is formed by introducing a small set of constraint edges into local Delaunay triangulation (LDel to reduce the number of hops between nodes in the network graph. We have simulated the CDT using network simulator (ns-2.28 and compared with Gabriel graph (GG, relative neighborhood graph (RNG, local Delaunay triangulation (LDel, and planarized local Delaunay triangulation (PLDel. The simulation results show that the minimum number of hops from source to destination is less than other spanners. We also observed the decrease in delay, jitter, and improvement in throughput.
Multiple Clustering Views via Constrained Projections
DEFF Research Database (Denmark)
Dang, Xuan-Hong; Assent, Ira; Bailey, James
2012-01-01
Clustering, the grouping of data based on mutual similarity, is often used as one of principal tools to analyze and understand data. Unfortunately, most conventional techniques aim at finding only a single clustering over the data. For many practical applications, especially those being described...... in high dimensional data, it is common to see that the data can be grouped into different yet meaningful ways. This gives rise to the recently emerging research area of discovering alternative clusterings. In this preliminary work, we propose a novel framework to generate multiple clustering views....... The framework relies on a constrained data projection approach by which we ensure that a novel alternative clustering being found is not only qualitatively strong but also distinctively different from a reference clustering solution. We demonstrate the potential of the proposed framework using both synthetic...
Constraining Dark Sectors with Monojets and Dijets
Chala, Mikael; McCullough, Matthew; Nardini, Germano; Schmidt-Hoberg, Kai
2015-01-01
We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever - precisely due to its sizeable interactions with the visible sector - the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simpli...
Topological impact of constrained fracture growth
Directory of Open Access Journals (Sweden)
Sigmund Mongstad Hope
2015-09-01
Full Text Available The topology of two discrete fracture network models is compared to investigate the impact of constrained fracture growth. In the Poissonian discrete fracture network model the fractures are assigned length, position and orientation independent of all other fractures, while in the mechanical discrete fracture network model the fractures grow and the growth can be limited by the presence of other fractures. The topology is found to be impacted by both the choice of model, as well as the choice of rules for the mechanical model. A significant difference is the degree mixing. In two dimensions the Poissonian model results in assortative networks, while the mechanical model results in disassortative networks. In three dimensions both models produce disassortative networks, but the disassortative mixing is strongest for the mechanical model.
Regions of constrained maximum likelihood parameter identifiability
Lee, C.-H.; Herget, C. J.
1975-01-01
This paper considers the parameter identification problem of general discrete-time, nonlinear, multiple-input/multiple-output dynamic systems with Gaussian-white distributed measurement errors. Knowledge of the system parameterization is assumed to be known. Regions of constrained maximum likelihood (CML) parameter identifiability are established. A computation procedure employing interval arithmetic is proposed for finding explicit regions of parameter identifiability for the case of linear systems. It is shown that if the vector of true parameters is locally CML identifiable, then with probability one, the vector of true parameters is a unique maximal point of the maximum likelihood function in the region of parameter identifiability and the CML estimation sequence will converge to the true parameters.
Communication Schemes with Constrained Reordering of Resources
DEFF Research Database (Denmark)
Popovski, Petar; Utkovski, Zoran; Trillingsgaard, Kasper Fløe
2013-01-01
reordering of the labelled user resources (packets, channels) in an existing, primary system. However, the degrees of freedom of the reordering are constrained by the operation of the primary system. The second scenario is related to communication systems with energy harvesting, where the transmitted signals...... pertaining to the communication model when the resources that can be reordered have binary values. The capacity result is valid under arbitrary error model in which errors in each resource (packet) occur independently. Inspired by the information—theoretic analysis, we have shown how to design practical......This paper introduces a communication model inspired by two practical scenarios. The first scenario is related to the concept of protocol coding, where information is encoded in the actions taken by an existing communication protocol. We investigate strategies for protocol coding via combinatorial...
Constraining CO emission estimates using atmospheric observations
Hooghiemstra, P. B.
2012-06-01
We apply a four-dimensional variational (4D-Var) data assimilation system to optimize carbon monoxide (CO) emissions and to reduce the uncertainty of emission estimates from individual sources using the chemistry transport model TM5. In the first study only a limited amount of surface network observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) is used to test the 4D-Var system. Uncertainty reduction up to 60% in yearly emissions is observed over well-constrained regions and the inferred emissions compare well with recent studies for 2004. However, since the observations only constrain total CO emissions, the 4D-Var system has difficulties separating anthropogenic and biogenic sources in particular. The inferred emissions are validated with NOAA aircraft data over North America and the agreement is significantly improved from the prior to posterior simulation. Validation with the Measurements Of Pollution In The Troposphere (MOPITT) instrument shows a slight improved agreement over the well-constrained Northern Hemisphere and in the tropics (except for the African continent). However, the model simulation with posterior emissions underestimates MOPITT CO total columns on the remote Southern Hemisphere (SH) by about 10%. This is caused by a reduction in SH CO sources mainly due to surface stations on the high southern latitudes. In the second study, we compare two global inversions to estimate carbon monoxide (CO) emissions for 2004. Either surface flask observations from NOAA or CO total columns from the MOPITT instrument are assimilated in a 4D-Var framework. In the Southern Hemisphere (SH) three important findings are reported. First, due to their different vertical sensitivity, the stations-only inversion increases SH biomass burning emissions by 108 Tg CO/yr more than the MOPITT-only inversion. Conversely, the MOPITT-only inversion results in SH natural emissions
Statistical mechanics of budget-constrained auctions
Altarelli, F.; Braunstein, A.; Realpe-Gomez, J.; Zecchina, R.
2009-07-01
Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being in the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). On the basis of the cavity method of statistical mechanics, we introduce a message-passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution, and we derive from its properties the phase diagram of the problem. As the control parameter (average value of the budgets) is varied, we find two phase transitions delimiting a region in which long-range correlations arise.
Fluctuation theorem for constrained equilibrium systems
Gilbert, Thomas; Dorfman, J. Robert
2006-02-01
We discuss the fluctuation properties of equilibrium chaotic systems with constraints such as isokinetic and Nosé-Hoover thermostats. Although the dynamics of these systems does not typically preserve phase-space volumes, the average phase-space contraction rate vanishes, so that the stationary states are smooth. Nevertheless, finite-time averages of the phase-space contraction rate have nontrivial fluctuations which we show satisfy a simple version of the Gallavotti-Cohen fluctuation theorem, complementary to the usual fluctuation theorem for nonequilibrium stationary states and appropriate to constrained equilibrium states. Moreover, we show that these fluctuations are distributed according to a Gaussian curve for long enough times. Three different systems are considered here: namely, (i) a fluid composed of particles interacting with Lennard-Jones potentials, (ii) a harmonic oscillator with Nosé-Hoover thermostatting, and (iii) a simple hyperbolic two-dimensional map.
Explaining evolution via constrained persistent perfect phylogeny.
Bonizzoni, Paola; Carrieri, Anna Paola; Della Vedova, Gianluca; Trucco, Gabriella
2014-01-01
The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to explain efficiently data that do not
A Path Algorithm for Constrained Estimation.
Zhou, Hua; Lange, Kenneth
2013-01-01
Many least-square problems involve affine equality and inequality constraints. Although there are a variety of methods for solving such problems, most statisticians find constrained estimation challenging. The current article proposes a new path-following algorithm for quadratic programming that replaces hard constraints by what are called exact penalties. Similar penalties arise in l1 regularization in model selection. In the regularization setting, penalties encapsulate prior knowledge, and penalized parameter estimates represent a trade-off between the observed data and the prior knowledge. Classical penalty methods of optimization, such as the quadratic penalty method, solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ∞, one recovers the constrained solution. In the exact penalty method, squared penalties!are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. The exact path-following method starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. Path following in Lasso penalized regression, in contrast, starts with a large value of the penalty constant and works its way downward. In both settings, inspection of the entire solution path is revealing. Just as with the Lasso and generalized Lasso, it is possible to plot the effective degrees of freedom along the solution path. For a strictly convex quadratic program, the exact penalty algorithm can be framed entirely in terms of the sweep operator of regression analysis. A few well-chosen examples illustrate the mechanics and potential of path following. This article has supplementary materials available online.
Electrophoretic deposition and constrained sintering of strontium titanate thick films
Energy Technology Data Exchange (ETDEWEB)
Amaral, Luís; Vilarinho, Paula M., E-mail: paula.vilarinho@ua.pt; Senos, Ana M.R.
2015-01-15
Thick films of functional oxides are currently substituting counterparts bulk ceramics, as in the case of low loss dielectrics. For SrTiO{sub 3} (ST) based compositions it is demonstrated that electrophoretic deposition (EPD), using acetone as a suspension media with iodine addition, is a suitable technology to fabricate 12 μm thick films. The microstructural analysis of the films sintered at 1500 °C shows that highly densified microstructures can be obtained and, by slightly varying the Sr/Ti stoichiometry in the powder composition, increased densification and grain size and enlargement of the distribution with decreasing Sr/Ti ratio can be observed. In spite of the high densification of the films, it is also demonstrated that due to the constraint imposed by the substrate a smaller grain size is observed in thick films as compared to equivalent bulk ceramics. In addition, a preferential vertical pore orientation is observed in ST thick films. These results may have broad implications if one considers that the dielectric losses and dielectric tunability is affected by pore orientation, since it affects the electric field distribution. - Highlights: • Nonstoichiometry effect on microstructure of constrained sintered thick films and bulk is similar. • Increased densification and grain size and enlargement of distribution with decreasing Sr/Ti ratio. • Independent of Sr/Ti ratio smaller grain size for thick films compared to ceramics. • Preferential vertical pore orientation for constrained sintering of thick films. • Anisotropic porosity as tailoring factor to engineer permittivity and tunability.
Modeling Atmospheric CO2 Processes to Constrain the Missing Sink
Kawa, S. R.; Denning, A. S.; Erickson, D. J.; Collatz, J. C.; Pawson, S.
2005-01-01
We report on a NASA supported modeling effort to reduce uncertainty in carbon cycle processes that create the so-called missing sink of atmospheric CO2. Our overall objective is to improve characterization of CO2 source/sink processes globally with improved formulations for atmospheric transport, terrestrial uptake and release, biomass and fossil fuel burning, and observational data analysis. The motivation for this study follows from the perspective that progress in determining CO2 sources and sinks beyond the current state of the art will rely on utilization of more extensive and intensive CO2 and related observations including those from satellite remote sensing. The major components of this effort are: 1) Continued development of the chemistry and transport model using analyzed meteorological fields from the Goddard Global Modeling and Assimilation Office, with comparison to real time data in both forward and inverse modes; 2) An advanced biosphere model, constrained by remote sensing data, coupled to the global transport model to produce distributions of CO2 fluxes and concentrations that are consistent with actual meteorological variability; 3) Improved remote sensing estimates for biomass burning emission fluxes to better characterize interannual variability in the atmospheric CO2 budget and to better constrain the land use change source; 4) Evaluating the impact of temporally resolved fossil fuel emission distributions on atmospheric CO2 gradients and variability. 5) Testing the impact of existing and planned remote sensing data sources (e.g., AIRS, MODIS, OCO) on inference of CO2 sources and sinks, and use the model to help establish measurement requirements for future remote sensing instruments. The results will help to prepare for the use of OCO and other satellite data in a multi-disciplinary carbon data assimilation system for analysis and prediction of carbon cycle changes and carbodclimate interactions.
Discussing the processes constraining the Jovian synchrotron radio emission's features
Santos-Costa, Daniel; Bolton, Scott J.
2008-03-01
Our recent analysis and understanding of the Jovian synchrotron radio emission with a radiation-belt model is presented. In this work, the electron population is determined by solving the Fokker-Planck diffusion equation and considering different physical processes. The results of the modeling are first compared to in situ particle data, brightness distributions, radio spectrum, and beaming curves to verify the simulated particle distributions. The dynamics of high-energy electrons in Jupiter's inner magnetosphere and their related radio emission are then examined. The results demonstrate that the Jovian moons set the extension and intensity of the synchrotron emission's brightness distribution along the magnetic equator. Simulations show that moons and dust both control the transport toward the planet by significantly reducing the abundance of particles constrained to populate, near the equator and inside 1.8 Jovian radii, the innermost region of the magnetosphere. Due to interactions with dust and synchrotron mechanism, radiation-belt electrons are moved along field lines, between Metis (1.79 Jovian radii) and Amalthea (2.54 Jovian radii), toward high latitudes. The quantity of particles transported away from the equator is sufficient to produce measurable secondary radio emissions. Among all the phenomena acting in the inner magnetosphere, the moons (Amalthea and Thebe) are the primary moderator for the radiation's intensity at high latitudes. Moon losses also affect the characteristics of the total radio flux with longitude. The sweeping effect amplifies the 10-h modulation of the beaming curve's amplitude while energy resonances occurring near Amalthea and Thebe belong to phenomena adjusting it to the right level. Interactions with dust do not significantly constrain radio spectrum features. Resonances near Amalthea and Thebe are responsible for the Jovian radio spectrum's particular slope.
Constraining ALP-photon coupling using galaxy clusters
Schlederer, Martin
2015-01-01
In this study, we propose a new approach to constrain the coupling of axion-like particles (ALPs) to photons. One intriguing property of these ALPs is their mixing with photons within magnetic fields. This mixing allows photons propagating in magnetic fields to convert into ALPs and \\textit{vice versa}. Plasma effects can lead to resonant conversion, further enhancing the conversion probability. For suitable ALP masses, this resonant conversion can occur for cosmic microwave background photons transversing galaxy clusters which would distort the CMB spectrum in the direction of galaxy clusters. We compare the predicted distortion with recent measurements of the thermal Sunyaev-Zeldovich Compton parameter to obtain upper limits on the coupling between photons and ALPs. The constraints apply to the mass range of approximately $2\\cdot 10^{-14}$ eV $ \\lesssim m_\\phi \\lesssim 3\\cdot 10^{-12}$ eV in which resonant photon-ALP conversions can occur. Using simple galaxy cluster models, we obtain new limits for this ma...
Titan's interior constrained from its obliquity and tidal Love number
Baland, Rose-Marie; Coyette, Alexis; Yseboodt, Marie; Beuthe, Mikael; Van Hoolst, Tim
2016-04-01
In the last few years, the Cassini-Huygens mission to the Saturn system has measured the shape, the obliquity, the static gravity field, and the tidally induced gravity field of Titan. The large values of the obliquity and of the k2 Love number both point to the existence of a global internal ocean below the icy crust. In order to constrain interior models of Titan, we combine the above-mentioned data as follows: (1) we build four-layer density profiles consistent with Titan's bulk properties; (2) we determine the corresponding internal flattening compatible with the observed gravity and topography; (3) we compute the obliquity and tidal Love number for each interior model; (4) we compare these predictions with the observations. Previously, we found that Titan is more differentiated than expected (assuming hydrostatic equilibrium), and that its ocean is dense and less than 100 km thick. Here, we revisit these conclusions using a more complete Cassini state model, including: (1) gravitational and pressure torques due to internal tidal deformations; (2) atmosphere/lakes-surface exchange of angular momentum; (3) inertial torque due to Poincaré flow. We also adopt faster methods to evaluate Love numbers (i.e. the membrane approach) in order to explore a larger parameter space.
A clear and measurable signature of modified gravity in the galaxy velocity field
Hellwing, Wojciech A; Frenk, Carlos S; Li, Baojiu; Cole, Shaun
2014-01-01
The velocity field of dark matter and galaxies reflects the continued action of gravity throughout cosmic history. We show that the low-order moments of the pairwise velocity distribution, $v_{12}$, are a powerful diagnostic of the laws of gravity on cosmological scales. In particular, the projected line-of-sight galaxy pairwise velocity dispersion, $\\sigma_{12}(r)$, is very sensitive to the presence of modified gravity. Using a set of high-resolution N-body simulations we compute the pairwise velocity distribution and its projected line-of-sight dispersion for a class of modified gravity theories: the chameleon $f(R)$ gravity and Galileon gravity (cubic and quartic). The velocities of dark matter halos with a wide range of masses exhibit deviations from General Relativity at the 5 to 10 $\\sigma$ level. We examine strategies for detecting these deviations in galaxy redshift and peculiar velocity surveys. If detected, this signature would be a smoking gun for modified gravity.
Clear and measurable signature of modified gravity in the galaxy velocity field.
Hellwing, Wojciech A; Barreira, Alexandre; Frenk, Carlos S; Li, Baojiu; Cole, Shaun
2014-06-06
The velocity field of dark matter and galaxies reflects the continued action of gravity throughout cosmic history. We show that the low-order moments of the pairwise velocity distribution v_{12} are a powerful diagnostic of the laws of gravity on cosmological scales. In particular, the projected line-of-sight galaxy pairwise velocity dispersion σ_{12}(r) is very sensitive to the presence of modified gravity. Using a set of high-resolution N-body simulations, we compute the pairwise velocity distribution and its projected line-of-sight dispersion for a class of modified gravity theories: the chameleon f(R) gravity and Galileon gravity (cubic and quartic). The velocities of dark matter halos with a wide range of masses would exhibit deviations from general relativity at the (5-10)σ level. We examine strategies for detecting these deviations in galaxy redshift and peculiar velocity surveys. If detected, this signature would be a "smoking gun" for modified gravity.
Dickman, Elizabeth M; Newell, Jennifer M; González, María J; Vanni, Michael J
2008-11-25
The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not been tested experimentally in food chains with 3 or more trophic levels. In a field experiment manipulating light, nutrients, and food-chain length, we show that FCE is constrained by algal food quality and food-chain length. FCE across 3 trophic levels (phytoplankton to carnivorous fish) was highest under low light and high nutrients, where algal quality was best as indicated by taxonomic composition and nutrient stoichiometry. In 3-level systems, FCE was constrained by the efficiency at which both herbivores and carnivores converted food into production; a strong nutrient effect on carnivore efficiency suggests a carryover effect of algal quality across 3 trophic levels. Energy transfer efficiency from algae to herbivores was also higher in 2-level systems (without carnivores) than in 3-level systems. Our results support the hypothesis that FCE is strongly constrained by light, nutrients, and food-chain length and suggest that carryover effects across multiple trophic levels are important. Because many environmental perturbations affect light, nutrients, and food-chain length, and many ecological services are mediated by FCE, it will be important to apply these findings to various ecosystem types.
Constrained Fisher Scoring for a Mixture of Factor Analyzers
2016-09-01
global appearance model across the entire sensor network. constrained maximum likelihood estimation, mixture of factor analyzers, Newton’s method...ARL-TR-7836• SEP 2016 US Army Research Laboratory Constrained Fisher Scoring for a Mixture of Factor Analyzers by Gene T Whipps, Emre Ertin, and...TR-7836• SEP 2016 US Army Research Laboratory Constrained Fisher Scoring for a Mixture of Factor Analyzers by Gene T Whipps Sensors and Electron
A Constrained Transport Scheme for MHD on Unstructured Static and Moving Meshes
Mocz, Philip; Hernquist, Lars
2014-01-01
Magnetic fields play an important role in many astrophysical systems and a detailed understanding of their impact on the gas dynamics requires robust numerical simulations. Here we present a new method to evolve the ideal magnetohydrodynamic (MHD) equations on unstructured static and moving meshes that preserves the magnetic field divergence-free constraint to machine precision. The method overcomes the major problems of using a cleaning scheme on the magnetic fields instead, which is non-conservative, not fully Galilean invariant, does not eliminate divergence errors completely, and may produce incorrect jumps across shocks. Our new method is a generalization of the constrained transport (CT) algorithm used to enforce the $\
Eulerian Formulation of Spatially Constrained Elastic Rods
Huynen, Alexandre
Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is in contact with a stiff constraining surface. The research work presented in this doctoral dissertation formulates a computational model for the solution of elastic rods constrained inside or around frictionless tube-like surfaces. The segmentation strategy adopted to cope with this complex class of problems consists in sequencing the global problem into, comparatively simpler, elementary problems either in continuous contact with the constraint or contact-free between their extremities. Within the conventional Lagrangian formulation of elastic rods, this approach is however associated with two major drawbacks. First, the boundary conditions specifying the locations of the rod centerline at both extremities of each elementary problem lead to the establishment of isoperimetric constraints, i.e., integral constraints on the unknown length of the rod. Second, the assessment of the unilateral contact condition requires, in principle, the comparison of two curves parametrized by distinct curvilinear coordinates, viz. the rod centerline and the constraint axis. Both conspire to burden the computations associated with the method. To streamline the solution along the elementary problems and rationalize the assessment of the unilateral contact condition, the rod governing equations are reformulated within the Eulerian framework of the constraint. The methodical exploration of both types of elementary problems leads to specific formulations of the rod governing equations that stress the profound connection between the mechanics of the rod and the geometry of the constraint surface. The proposed Eulerian reformulation, which restates the rod local equilibrium in terms of the curvilinear coordinate associated with the constraint axis, describes the rod deformed configuration
Resource Management in Constrained Dynamic Situations
Seok, Jinwoo
Resource management is considered in this dissertation for systems with limited resources, possibly combined with other system constraints, in unpredictably dynamic environments. Resources may represent fuel, power, capabilities, energy, and so on. Resource management is important for many practical systems; usually, resources are limited, and their use must be optimized. Furthermore, systems are often constrained, and constraints must be satisfied for safe operation. Simplistic resource management can result in poor use of resources and failure of the system. Furthermore, many real-world situations involve dynamic environments. Many traditional problems are formulated based on the assumptions of given probabilities or perfect knowledge of future events. However, in many cases, the future is completely unknown, and information on or probabilities about future events are not available. In other words, we operate in unpredictably dynamic situations. Thus, a method is needed to handle dynamic situations without knowledge of the future, but few formal methods have been developed to address them. Thus, the goal is to design resource management methods for constrained systems, with limited resources, in unpredictably dynamic environments. To this end, resource management is organized hierarchically into two levels: 1) planning, and 2) control. In the planning level, the set of tasks to be performed is scheduled based on limited resources to maximize resource usage in unpredictably dynamic environments. In the control level, the system controller is designed to follow the schedule by considering all the system constraints for safe and efficient operation. Consequently, this dissertation is mainly divided into two parts: 1) planning level design, based on finite state machines, and 2) control level methods, based on model predictive control. We define a recomposable restricted finite state machine to handle limited resource situations and unpredictably dynamic environments
Sequential unconstrained minimization algorithms for constrained optimization
Byrne, Charles
2008-02-01
The problem of minimizing a function f(x):RJ → R, subject to constraints on the vector variable x, occurs frequently in inverse problems. Even without constraints, finding a minimizer of f(x) may require iterative methods. We consider here a general class of iterative algorithms that find a solution to the constrained minimization problem as the limit of a sequence of vectors, each solving an unconstrained minimization problem. Our sequential unconstrained minimization algorithm (SUMMA) is an iterative procedure for constrained minimization. At the kth step we minimize the function G_k(x)=f(x)+g_k(x), to obtain xk. The auxiliary functions gk(x):D ⊆ RJ → R+ are nonnegative on the set D, each xk is assumed to lie within D, and the objective is to minimize the continuous function f:RJ → R over x in the set C=\\overline D , the closure of D. We assume that such minimizers exist, and denote one such by \\hat x . We assume that the functions gk(x) satisfy the inequalities 0\\leq g_k(x)\\leq G_{k-1}(x)-G_{k-1}(x^{k-1}), for k = 2, 3, .... Using this assumption, we show that the sequence {f(xk)} is decreasing and converges to f({\\hat x}) . If the restriction of f(x) to D has bounded level sets, which happens if \\hat x is unique and f(x) is closed, proper and convex, then the sequence {xk} is bounded, and f(x^*)=f({\\hat x}) , for any cluster point x*. Therefore, if \\hat x is unique, x^*={\\hat x} and \\{x^k\\}\\rightarrow {\\hat x} . When \\hat x is not unique, convergence can still be obtained, in particular cases. The SUMMA includes, as particular cases, the well-known barrier- and penalty-function methods, the simultaneous multiplicative algebraic reconstruction technique (SMART), the proximal minimization algorithm of Censor and Zenios, the entropic proximal methods of Teboulle, as well as certain cases of gradient descent and the Newton-Raphson method. The proof techniques used for SUMMA can be extended to obtain related results for the induced proximal
The goldstino brane, the constrained superfields and matter in N=1 supergravity
Energy Technology Data Exchange (ETDEWEB)
Bandos, Igor [Department of Theoretical Physics, University of the Basque Country UPV/EHU,P.O. Box 644, 48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science,48011, Bilbao (Spain); Heller, Markus [Dipartimento di Fisica e Astronomia “Galileo Galilei' , Università degli Studi di Padova,Via Marzolo 8, 35131 Padova (Italy); Institut für Theoretische Physik, Ruprecht-Karls-Universität,Philosophenweg 19, 69120 Heidelberg (Germany); Kuzenko, Sergei M. [School of Physics M013, The University of Western Australia35 Stirling Highway, Crawley W.A. 6009 (Australia); Martucci, Luca [Dipartimento di Fisica e Astronomia “Galileo Galilei' , Università degli Studi di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN - Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy); Sorokin, Dmitri [INFN - Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy); Dipartimento di Fisica e Astronomia “Galileo Galilei' , Università degli Studi di Padova,Via Marzolo 8, 35131 Padova (Italy)
2016-11-21
We show that different (brane and constrained superfield) descriptions for the Volkov-Akulov goldstino coupled to N=1, D=4 supergravity with matter produce similar wide classes of models with spontaneously broken local supersymmetry and discuss the relation between the different formulations. As with the formulations with irreducible constrained superfields, the geometric goldstino brane approach has the advantage of being manifestly off-shell supersymmetric without the need to introduce auxiliary fields. It provides an explicit solution of the nilpotent superfield constraints and avoids issues with non-Gaussian integration of auxiliary fields. We describe general couplings of the supersymmetry breaking sector, including the goldstino and other non-supersymmetric matter, to supergravity and matter supermultiplets. Among various examples, we discuss a goldstino brane contribution to the gravitino mass term and the supersymmetrization of the anti-D3-brane contribution to the effective theory of type IIB warped flux compactifications.
The Goldstino Brane, the Constrained Superfields and Matter in N=1 Supergravity
Bandos, Igor; Kuzenko, Sergei M; Martucci, Luca; Sorokin, Dmitri
2016-01-01
We show that different (brane and constrained superfield) descriptions for the Volkov-Akulov goldstino coupled to N=1, D=4 supergravity with matter produce similar wide classes of models with spontaneously broken local supersymmetry and discuss the relation between the different formulations. As with the formulations with irreducible constrained superfields, the geometric goldstino brane approach has the advantage of being manifestly off-shell supersymmetric without the need to introduce auxiliary fields. It provides an explicit solution of the nilpotent superfield constraints and avoids issues with non-Gaussian integration of auxiliary fields. We describe general couplings of the supersymmetry breaking sector, including the goldstino and other non-supersymmetric matter, to supergravity and matter supermultiplets. Among various examples, we discuss a goldstino brane contribution to the gravitino mass term and the supersymmetrization of the anti-D3-brane contribution to the effective theory of type IIB warped ...
Pinel-Giroux, Fanny-Maud; de Guise, Jacques A.; Labelle, Hubert
2007-01-01
Sagittal curvatures of the spine can be assessed using the constrained or non-constrained Cobb techniques. However, there is no study that specifically compares these two techniques. The objective of this study is to assess the reproducibility and clinical relevance of the non-constrained Cobb technique (non-constrained limit vertebrae) compared to the constrained Cobb technique (constrained limit vertebrae). Standing sagittal radiographs of the spine of ten adolescents with idiopathic scoliosis, ten adolescents with spondylolisthesis and ten normal adolescents were selected. Thoracic kyphosis (TK) and lumbar lordosis (LL) were measured twice by three observers using both constrained and non-constrained Cobb techniques. Pearson’s correlation coefficients, as well as intra- and inter-observer intra-class correlation coefficients (ICC) were calculated. Inter-observer ICCs were similar for TK and LL with both techniques, ranging from 0.84 to 0.89. Intra-observer ICCs for both techniques were between 0.74 and 0.92 for TK, while they were between 0.87 and 0.97 for LL. The two techniques were highly correlated for the measurement of the TK (r = 0.96) and LL (r = 0.94). Computer-assisted assessment of the sagittal profile using the non-constrained Cobb technique provides excellent reproducibility. As opposed to the constrained Cobb technique, the non-constrained Cobb technique takes into account the variability in the level of transition between the TK and LL. However, adequate use of this technique requires accurate identification of the limit vertebrae in the thoracolumbar spine. Consequently, a computer-assisted technique is recommended when using the non-constrained Cobb technique. PMID:17426991
Electricity in a Climate-Constrained World
Energy Technology Data Exchange (ETDEWEB)
NONE
2012-07-01
After experiencing a historic drop in 2009, electricity generation reached a record high in 2010, confirming the close linkage between economic growth and electricity usage. Unfortunately, CO2 emissions from electricity have also resumed their growth: Electricity remains the single-largest source of CO2 emissions from energy, with 11.7 billion tonnes of CO2 released in 2010. The imperative to 'decarbonise' electricity and improve end-use efficiency remains essential to the global fight against climate change. The IEA’s Electricity in a Climate-Constrained World provides an authoritative resource on progress to date in this area, including statistics related to CO2 and the electricity sector across ten regions of the world (supply, end-use and capacity additions). It also presents topical analyses on the challenge of rapidly curbing CO2 emissions from electricity. Looking at policy instruments, it focuses on emissions trading in China, using energy efficiency to manage electricity supply crises and combining policy instruments for effective CO2 reductions. On regulatory issues, it asks whether deregulation can deliver decarbonisation and assesses the role of state-owned enterprises in emerging economies. And from technology perspectives, it explores the rise of new end-uses, the role of electricity storage, biomass use in Brazil, and the potential of carbon capture and storage for ‘negative emissions’ electricity supply.
Constraining the Properties of Cold Interstellar Clouds
Spraggs, Mary Elizabeth; Gibson, Steven J.
2016-01-01
Since the interstellar medium (ISM) plays an integral role in star formation and galactic structure, it is important to understand the evolution of clouds over time, including the processes of cooling and condensation that lead to the formation of new stars. This work aims to constrain and better understand the physical properties of the cold ISM by utilizing large surveys of neutral atomic hydrogen (HI) 21cm spectral line emission and absorption, carbon monoxide (CO) 2.6mm line emission, and multi-band infrared dust thermal continuum emission. We identify areas where the gas may be cooling and forming molecules using HI self-absorption (HISA), in which cold foreground HI absorbs radiation from warmer background HI emission.We are developing an algorithm that uses total gas column densities inferred from Planck and other FIR/sub-mm data in parallel with CO and HISA spectral line data to determine the gas temperature, density, molecular abundance, and other properties as functions of position. We can then map these properties to study their variation throughout an individual cloud as well as any dependencies on location or environment within the Galaxy.Funding for this work was provided by the National Science Foundation, the NASA Kentucky Space Grant Consortium, the WKU Ogden College of Science and Engineering, and the Carol Martin Gatton Academy for Mathematics and Science in Kentucky.
Constrained Graph Optimization: Interdiction and Preservation Problems
Energy Technology Data Exchange (ETDEWEB)
Schild, Aaron V [Los Alamos National Laboratory
2012-07-30
The maximum flow, shortest path, and maximum matching problems are a set of basic graph problems that are critical in theoretical computer science and applications. Constrained graph optimization, a variation of these basic graph problems involving modification of the underlying graph, is equally important but sometimes significantly harder. In particular, one can explore these optimization problems with additional cost constraints. In the preservation case, the optimizer has a budget to preserve vertices or edges of a graph, preventing them from being deleted. The optimizer wants to find the best set of preserved edges/vertices in which the cost constraints are satisfied and the basic graph problems are optimized. For example, in shortest path preservation, the optimizer wants to find a set of edges/vertices within which the shortest path between two predetermined points is smallest. In interdiction problems, one deletes vertices or edges from the graph with a particular cost in order to impede the basic graph problems as much as possible (for example, delete edges/vertices to maximize the shortest path between two predetermined vertices). Applications of preservation problems include optimal road maintenance, power grid maintenance, and job scheduling, while interdiction problems are related to drug trafficking prevention, network stability assessment, and counterterrorism. Computational hardness results are presented, along with heuristic methods for approximating solutions to the matching interdiction problem. Also, efficient algorithms are presented for special cases of graphs, including on planar graphs. The graphs in many of the listed applications are planar, so these algorithms have important practical implications.
Constrained spheroids for prolonged hepatocyte culture.
Tong, Wen Hao; Fang, Yu; Yan, Jie; Hong, Xin; Hari Singh, Nisha; Wang, Shu Rui; Nugraha, Bramasta; Xia, Lei; Fong, Eliza Li Shan; Iliescu, Ciprian; Yu, Hanry
2016-02-01
Liver-specific functions in primary hepatocytes can be maintained over extended duration in vitro using spheroid culture. However, the undesired loss of cells over time is still a major unaddressed problem, which consequently generates large variations in downstream assays such as drug screening. In static culture, the turbulence generated by medium change can cause spheroids to detach from the culture substrate. Under perfusion, the momentum generated by Stokes force similarly results in spheroid detachment. To overcome this problem, we developed a Constrained Spheroids (CS) culture system that immobilizes spheroids between a glass coverslip and an ultra-thin porous Parylene C membrane, both surface-modified with poly(ethylene glycol) and galactose ligands for optimum spheroid formation and maintenance. In this configuration, cell loss was minimized even when perfusion was introduced. When compared to the standard collagen sandwich model, hepatocytes cultured as CS under perfusion exhibited significantly enhanced hepatocyte functions such as urea secretion, and CYP1A1 and CYP3A2 metabolic activity. We propose the use of the CS culture as an improved culture platform to current hepatocyte spheroid-based culture systems.
Constraining cosmic isotropy with type Ia supernovae
Bengaly,, C A P; Alcaniz, J S
2016-01-01
We investigate the validity of the Cosmological Principle by constraining the cosmological parameters $H_0$ and $q_0$ through the celestial sphere. Our analyses are performed in a low-redshift regime in order to follow a model independent approach, using both Union2.1 and JLA Type Ia Supernovae (SNe) compilations. We find that the preferred direction of the $H_0$ parameter in the sky is consistent with the bulk flow motion of our local Universe in the Union2.1 case, while the $q_0$ directional analysis seem to be anti-correlated with the $H_0$ for both data sets. Furthermore, we test the consistency of these results with Monte Carlo (MC) realisations, finding that the anisotropy on both parameters are significant within $2-3\\sigma$ confidence level, albeit we find a significant correlation between the $H_0$ and $q_0$ mapping with the angular distribution of SNe from the JLA compilation. Therefore, we conclude that the detected anisotropies are either of local origin, or induced by the non-uniform celestial co...
Constraining the Oblateness of Kepler Planets
Zhu, Wei; Zhou, George; Lin, D N C
2014-01-01
We use Kepler short cadence light curves to constrain the oblateness of planet candidates in the Kepler sample. The transits of rapidly rotating planets that are deformed in shape will lead to distortions in the ingress and egress of their light curves. We report the first tentative detection of an oblate planet outside of the solar system, measuring an oblateness of $0.22 \\pm 0.11$ for the 18 $M_J$ mass brown dwarf Kepler 39b (KOI-423.01). We also provide constraints on the oblateness of the planets (candidates) HAT-P-7b, KOI-686.01, and KOI-197.01 to be < 0.067, < 0.251, and < 0.186, respectively. Using the Q'-values from Jupiter and Saturn, we expect tidal synchronization for the spins of HAT-P-7b, KOI-686.01 and KOI-197.01, and for their rotational oblateness signatures to be undetectable in the current data. The potentially large oblateness of KOI-423.01 (Kepler 39b) suggests that the Q'-value of the brown dwarf needs to be two orders of magnitude larger than that of the solar system gas giants ...
Should we still believe in constrained supersymmetry?
Balázs, Csaba; Carter, Daniel; Farmer, Benjamin; White, Martin
2012-01-01
We calculate Bayes factors to quantify how the feasibility of the constrained minimal supersymmetric standard model (CMSSM) has changed in the light of a series of observations. This is done in the Bayesian spirit where probability reflects a degree of belief in a proposition and Bayes' theorem tells us how to update it after acquiring new information. Our experimental baseline is the approximate knowledge that was available before LEP, and our comparison model is the Standard Model with a simple dark matter candidate. To quantify the amount by which experiments have altered our relative belief in the CMSSM since the baseline data we compute the Bayes factors that arise from learning in sequence the LEP Higgs constraints, the XENON100 dark matter constraints, the 2011 LHC supersymmetry search results, and the early 2012 LHC Higgs search results. We find that LEP and the LHC strongly shatter our trust in the CMSSM (with $M_0$ and $M_{1/2}$ below 2 TeV), reducing its posterior odds by a factor of approximately ...
Constraining the halo mass function with observations
Castro, Tiago; Quartin, Miguel
2016-01-01
The abundances of matter halos in the universe are described by the so-called halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behavior through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of type Ia supernovae. Our results show that DES is capable of putting the first meaningful constraints, while both Euclid and J-PAS can give constraints on the HMF parameters which are comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even mo...
Constraining New Physics with D meson decays
Energy Technology Data Exchange (ETDEWEB)
Barranco, J.; Delepine, D.; Gonzalez Macias, V. [Departamento de Física, División de Ciencias e Ingeniería, Universidad de Guanajuato, Campus León, León 37150 (Mexico); Lopez-Lozano, L. [Departamento de Física, División de Ciencias e Ingeniería, Universidad de Guanajuato, Campus León, León 37150 (Mexico); Área Académica de Matemáticas y Física, Universidad Autónoma del Estado de Hidalgo, Carr. Pachuca-Tulancingo Km. 4.5, C.P. 42184, Pachuca, HGO (Mexico)
2014-04-04
Latest Lattice results on D form factors evaluation from first principles show that the Standard Model (SM) branching ratios prediction for the leptonic D{sub s}→ℓν{sub ℓ} decays and the semileptonic SM branching ratios of the D{sup 0} and D{sup +} meson decays are in good agreement with the world average experimental measurements. It is possible to disprove New Physics hypothesis or find bounds over several models beyond the SM. Using the observed leptonic and semileptonic branching ratios for the D meson decays, we performed a combined analysis to constrain non-standard interactions which mediate the cs{sup ¯}→lν{sup ¯} transition. This is done either by a model-independent way through the corresponding Wilson coefficients or in a model-dependent way by finding the respective bounds over the relevant parameters for some models beyond the Standard Model. In particular, we obtain bounds for the Two Higgs Doublet Model Type-II and Type III, the Left–Right model, the Minimal Supersymmetric Standard Model with explicit R-parity violation and Leptoquarks. Finally, we estimate the transverse polarization of the lepton in the D{sup 0} decay and we found it can be as high as P{sub T}=0.23.
Joint Chance-Constrained Dynamic Programming
Ono, Masahiro; Kuwata, Yoshiaki; Balaram, J. Bob
2012-01-01
This paper presents a novel dynamic programming algorithm with a joint chance constraint, which explicitly bounds the risk of failure in order to maintain the state within a specified feasible region. A joint chance constraint cannot be handled by existing constrained dynamic programming approaches since their application is limited to constraints in the same form as the cost function, that is, an expectation over a sum of one-stage costs. We overcome this challenge by reformulating the joint chance constraint into a constraint on an expectation over a sum of indicator functions, which can be incorporated into the cost function by dualizing the optimization problem. As a result, the primal variables can be optimized by a standard dynamic programming, while the dual variable is optimized by a root-finding algorithm that converges exponentially. Error bounds on the primal and dual objective values are rigorously derived. We demonstrate the algorithm on a path planning problem, as well as an optimal control problem for Mars entry, descent and landing. The simulations are conducted using a real terrain data of Mars, with four million discrete states at each time step.
iBGP and Constrained Connectivity
Dinitz, Michael
2011-01-01
We initiate the theoretical study of the problem of minimizing the size of an iBGP overlay in an Autonomous System (AS) in the Internet subject to a natural notion of correctness derived from the standard "hot-potato" routing rules. For both natural versions of the problem (where we measure the size of an overlay by either the number of edges or the maximum degree) we prove that it is NP-hard to approximate to a factor better than $\\Omega(\\log n)$ and provide approximation algorithms with ratio $\\tilde{O}(\\sqrt{n})$. In addition, we give a slightly worse $\\tilde{O}(n^{2/3})$-approximation based on primal-dual techniques that has the virtue of being both fast and good in practice, which we show via simulations on the actual topologies of five large Autonomous Systems. The main technique we use is a reduction to a new connectivity-based network design problem that we call Constrained Connectivity. In this problem we are given a graph $G=(V,E)$, and for every pair of vertices $u,v \\in V$ we are given a set $S(u,...
Founder niche constrains evolutionary adaptive radiation.
Flohr, Régis C E; Blom, Carsten J; Rainey, Paul B; Beaumont, Hubertus J E
2013-12-17
Adaptive radiation of a lineage into a range of organisms with different niches underpins the evolution of life's diversity. Although the role of the environment in shaping adaptive radiation is well established, theory predicts that the evolvability and niche of the founding ancestor are also of importance. Direct demonstration of a causal link requires resolving the independent effects of these additional factors. Here, we accomplish this using experimental bacterial populations and demonstrate how the dynamics of adaptive radiation are constrained by the niche of the founder. We manipulated the propensity of the founder to undergo adaptive radiation and resolved the underlying causal changes in both its evolvability and niche. Evolvability did not change, but the propensity for adaptive radiation was altered by changes in the position and breadth of the niche of the founder. These observations provide direct empirical evidence for a link between the niche of organisms and their propensity for adaptive radiation. This general mechanism may have rendered the evolutionary dynamics of extant adaptive radiations dependent on chance events that determined their founding ancestors.
Constraining the roughness degree of slip heterogeneity
Causse, Mathieu
2010-05-07
This article investigates different approaches for assessing the degree of roughness of the slip distribution of future earthquakes. First, we analyze a database of slip images extracted from a suite of 152 finite-source rupture models from 80 events (Mw = 4.1–8.9). This results in an empirical model defining the distribution of the slip spectrum corner wave numbers (kc) as a function of moment magnitude. To reduce the “epistemic” uncertainty, we select a single slip model per event and screen out poorly resolved models. The number of remaining models (30) is thus rather small. In addition, the robustness of the empirical model rests on a reliable estimation of kc by kinematic inversion methods. We address this issue by performing tests on synthetic data with a frequency domain inversion method. These tests reveal that due to smoothing constraints used to stabilize the inversion process, kc tends to be underestimated. We then develop an alternative approach: (1) we establish a proportionality relationship between kc and the peak ground acceleration (PGA), using a k−2 kinematic source model, and (2) we analyze the PGA distribution, which is believed to be better constrained than slip images. These two methods reveal that kc follows a lognormal distribution, with similar standard deviations for both methods.
Constraining groundwater modeling with magnetic resonance soundings.
Boucher, Marie; Favreau, Guillaume; Nazoumou, Yahaya; Cappelaere, Bernard; Massuel, Sylvain; Legchenko, Anatoly
2012-01-01
Magnetic resonance sounding (MRS) is a noninvasive geophysical method that allows estimating the free water content and transmissivity of aquifers. In this article, the ability of MRS to improve the reliability of a numerical groundwater model is assessed. Thirty-five sites were investigated by MRS over a ∼5000 km(2) domain of the sedimentary Continental Terminal aquifer in SW Niger. Time domain electromagnetic soundings were jointly carried out to estimate the aquifer thickness. A groundwater model was previously built for this section of the aquifer and forced by the outputs from a distributed surface hydrology model, to simulate the observed long-term (1992 to 2003) rise in the water table. Uncertainty analysis had shown that independent estimates of the free water content and transmissivity values of the aquifer would facilitate cross-evaluation of the surface-water and groundwater models. MRS results indicate ranges for permeability (K = 1 × 10(-5) to 3 × 10(-4) m/s) and for free water content (w = 5% to 23% m(3) /m(3) ) narrowed by two orders of magnitude (K) and by ∼50% (w), respectively, compared to the ranges of permeability and specific yield values previously considered. These shorter parameter ranges result in a reduction in the model's equifinality (whereby multiple combinations of model's parameters are able to represent the same observed piezometric levels), allowing a better constrained estimate to be derived for net aquifer recharge (∼22 mm/year).
Pressure compensated transducer system with constrained diaphragm
Percy, Joseph L.
1992-08-01
An acoustic source apparatus has an acoustic transducer that is enclosed in a substantially rigid and watertight enclosure to resist the pressure of water on the transducer and to seal the transducer from the water. The enclosure has an opening through which acoustic signals pass and over which is placed a resilient, expandable and substantially water-impermeable diaphragm. A net stiffens and strengthens the diaphragm as well as constrains the diaphragm from overexpansion or from migrating due to buoyancy forces. Pressurized gas, regulated at slightly above ambient pressure, is supplied to the enclosure and the diaphragm to compensate for underwater ambient pressures. Gas pressure regulated at above ambient pressure is used to selectively tune the pressure levels within the enclosure and diaphragm so that diaphragm resonance can be achieved. Controls are used to selectively fill, as well as vent the enclosure and diaphragm during system descent and ascent, respectively. A signal link is used to activate these controls and to provide the driving force for the acoustic transducer.
Joint Chance-Constrained Dynamic Programming
Ono, Masahiro; Kuwata, Yoshiaki; Balaram, J. Bob
2012-01-01
This paper presents a novel dynamic programming algorithm with a joint chance constraint, which explicitly bounds the risk of failure in order to maintain the state within a specified feasible region. A joint chance constraint cannot be handled by existing constrained dynamic programming approaches since their application is limited to constraints in the same form as the cost function, that is, an expectation over a sum of one-stage costs. We overcome this challenge by reformulating the joint chance constraint into a constraint on an expectation over a sum of indicator functions, which can be incorporated into the cost function by dualizing the optimization problem. As a result, the primal variables can be optimized by a standard dynamic programming, while the dual variable is optimized by a root-finding algorithm that converges exponentially. Error bounds on the primal and dual objective values are rigorously derived. We demonstrate the algorithm on a path planning problem, as well as an optimal control problem for Mars entry, descent and landing. The simulations are conducted using a real terrain data of Mars, with four million discrete states at each time step.
Constraining Sterile Neutrinos Using Reactor Neutrino Experiments
Girardi, Ivan; Ohlsson, Tommy; Zhang, He; Zhou, Shun
2014-01-01
Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experi\\-ment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle $\\sin^2 2 \\theta_{14} \\lesssim 0.06$ at 3$\\sigma$ confidence level for the mass-squared difference $\\Delta m^2_{41}$ in the range $(10^{-3},10^{-1}) \\, {\\rm eV^2}$. The latter bound can be improved by six years of running of the JUNO experiment, $\\sin^22\\theta_{14} \\lesssim 0.016$, although in the smaller mass range $ \\Delta m^2_{41} \\in (10^{-4} ,10^{-3}) \\, {\\rm eV}^2$. We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters $\\theta_{13}$ and $\\Delta m^2...
Constraining the oblateness of Kepler planets
Energy Technology Data Exchange (ETDEWEB)
Zhu, Wei [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Huang, Chelsea X. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Zhou, George [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Lin, D. N. C., E-mail: weizhu@astronomy.ohio-state.edu [UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
2014-11-20
We use Kepler short-cadence light curves to constrain the oblateness of planet candidates in the Kepler sample. The transits of rapidly rotating planets that are deformed in shape will lead to distortions in the ingress and egress of their light curves. We report the first tentative detection of an oblate planet outside the solar system, measuring an oblateness of 0.22{sub −0.11}{sup +0.11} for the 18 M{sub J} mass brown dwarf Kepler 39b (KOI 423.01). We also provide constraints on the oblateness of the planets (candidates) HAT-P-7b, KOI 686.01, and KOI 197.01 to be <0.067, <0.251, and <0.186, respectively. Using the Q' values from Jupiter and Saturn, we expect tidal synchronization for the spins of HAT-P-7b, KOI 686.01, and KOI 197.01, and for their rotational oblateness signatures to be undetectable in the current data. The potentially large oblateness of KOI 423.01 (Kepler 39b) suggests that the Q' value of the brown dwarf needs to be two orders of magnitude larger than that of the solar system gas giants to avoid being tidally spun down.
Optimal performance of constrained control systems
Harvey, P. Scott, Jr.; Gavin, Henri P.; Scruggs, Jeffrey T.
2012-08-01
This paper presents a method to compute optimal open-loop trajectories for systems subject to state and control inequality constraints in which the cost function is quadratic and the state dynamics are linear. For the case in which inequality constraints are decentralized with respect to the controls, optimal Lagrange multipliers enforcing the inequality constraints may be found at any time through Pontryagin’s minimum principle. In so doing, the set of differential algebraic Euler-Lagrange equations is transformed into a nonlinear two-point boundary-value problem for states and costates whose solution meets the necessary conditions for optimality. The optimal performance of inequality constrained control systems is calculable, allowing for comparison to previous, sub-optimal solutions. The method is applied to the control of damping forces in a vibration isolation system subjected to constraints imposed by the physical implementation of a particular controllable damper. An outcome of this study is the best performance achievable given a particular objective, isolation system, and semi-active damper constraints.
Constrained Subjective Assessment of Student Learning
Saliu, Sokol
2005-09-01
Student learning is a complex incremental cognitive process; assessment needs to parallel this, reporting the results in similar terms. Application of fuzzy sets and logic to the criterion-referenced assessment of student learning is considered here. The constrained qualitative assessment (CQA) system was designed, and then applied in assessing a past course in microcomputer system design (MSD). CQA criteria were articulated in fuzzy terms and sets, and the assessment procedure was cast as a fuzzy inference rule base. An interactive graphic interface provided for transparent assessment, student "backwash," and support to the teacher when compiling the tests. Grade intervals, obtained from a departmental poll, were used to compile a fuzzy "grade" set. Assessment results were compared to those of a former standard method and to those of a modified version of it (but with fewer criteria). The three methods yielded similar results, supporting the application of CQA. The method improved assessment reliability by means of the consensus embedded in the fuzzy grade set, and improved assessment validity by integrating fuzzy criteria into the assessment procedure.
Constraining solar hidden photons using HPGe detector
Energy Technology Data Exchange (ETDEWEB)
Horvat, R.; Kekez, D., E-mail: Dalibor.Kekez@irb.hr; Krčmar, M.; Krečak, Z.; Ljubičić, A.
2013-04-25
In this Letter we report on the results of our search for photons from a U(1) gauge factor in the hidden sector of the full theory. With our experimental setup we observe the single spectrum in a HPGe detector arising as a result of the photoelectric-like absorption of hidden photons emitted from the Sun on germanium atoms inside the detector. The main ingredient of the theory used in our analysis, a severely constrained kinetic mixing from the two U(1) gauge factors and massive hidden photons, entails both photon into hidden state oscillations and a minuscule coupling of hidden photons to visible matter, of which the latter our experimental setup has been designed to observe. On a theoretical side, full account was taken of the effects of refraction and damping of photons while propagating in Sun's interior as well as in the detector. We exclude hidden photons with kinetic couplings χ>(2.2×10{sup −13}–3×10{sup −7}) in the mass region 0.2 eV≲m{sub γ{sup ′}}≲30 keV. Our constraints on the mixing parameter χ in the mass region from 20 eV up to 15 keV prove even slightly better then those obtained recently by using data from the CAST experiment, albeit still somewhat weaker than those obtained from solar and HB stars lifetime arguments.
Constraining local 3-D models of the saturated-zone, Yucca Mountain, Nevada
Energy Technology Data Exchange (ETDEWEB)
Barr, G.E.; Shannon, S.A.
1994-04-01
A qualitative three-dimensional analysis of the saturated zone flow system was performed for a 8 km {times} 8 km region including the potential Yucca Mountain repository site. Certain recognized geologic features of unknown hydraulic properties were introduced to assess the general response of the flow field to these features. Two of these features, the Solitario Canyon fault and the proposed fault in Drill Hole Wash, appear to constrain flow and allow calibration.
Constraining local 3-D models of the saturated-zone, Yucca Mountain, Nevada
Energy Technology Data Exchange (ETDEWEB)
Barr, G.E.; Shannon, S.A. [Sandia National Labs., Albuquerque, NM (United States)
1994-12-31
A qualitative three-dimensional analysis of the saturated zone flow system was performed for a 8 km {times} 8 km region including the potential Yucca Mountain repository site. Certain recognized geologic features of unknown hydraulic properties were introduced to assess the general response of the flow field to these features. Two of these features, the Solitario Canyon fault and the proposed fault in Drill Hole Wash, appear to constrain flow and allow calibration.
Constrained superfields from an anti-D3-brane in KKLT
Vercnocke, Bert; Wrase, Timm
2016-08-01
The KKLT construction of dS vacua [1] relies on an uplift term that arises from an anti-D3-brane. It was argued by Kachru, Pearson and Verlinde [2] that this anti-D3-brane is an excited state in a supersymmetric theory since it can decay to a supersymmetric ground state. Hence the anti-D3-brane breaks supersymmetry spontaneously and one should be able to package all the world-volume fields on the anti-D3-brane into a four dimensional {N} = 1 supersymmetric action. Here we extend previous results and identify the constrained superfields that correspond to all the degrees of freedom on the anti-D3-brane. In particular, we show explicitly that the four 4D worldvolume spinors give rise to constrained chiral multiplets S and Y i , i = 1 , 2 , 3 that satisfy S 2 = SY i = 0. We also conjecture (and provide evidence in a forthcoming publication) that the vector field A μ and the three scalars ϕ i give rise to a field strength multiplet W α and three chiral multiplets H i that satisfy the constraints S{W}_{α }={overline{D}}_{overset{\\cdot }{α }}(S{overline{H}}^i)=0 . This is the first time that such constrained multiplets appear in string theory constructions.
The Pendulum: From Constrained Fall to the Concept of Potential
Bevilacqua, Fabio; Falomo, Lidia; Fregonese, Lucio; Giannetto, Enrico; Giudice, Franco; Mascheretti, Paolo
2006-01-01
Kuhn underlined the relevance of Galileo's gestalt switch in the interpretation of a swinging body from constrained fall to time metre. But the new interpretation did not eliminate the older one. The constrained fall, both in the motion of pendulums and along inclined planes, led Galileo to the law of free fall. Experimenting with physical…
I/O-Efficient Construction of Constrained Delaunay Triangulations
DEFF Research Database (Denmark)
Agarwal, Pankaj Kumar; Arge, Lars; Yi, Ke
2005-01-01
In this paper, we designed and implemented an I/O-efficient algorithm for constructing constrained Delaunay triangulations. If the number of constraining segments is smaller than the memory size, our algorithm runs in expected O( N B logM/B NB ) I/Os for triangulating N points in the plane, where M...
21 CFR 888.3720 - Toe joint polymer constrained prosthesis.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Toe joint polymer constrained prosthesis. 888.3720 Section 888.3720 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of...
The Pendulum: From Constrained Fall to the Concept of Potential
Bevilacqua, Fabio; Falomo, Lidia; Fregonese, Lucio; Giannetto, Enrico; Giudice, Franco; Mascheretti, Paolo
2006-01-01
Kuhn underlined the relevance of Galileo's gestalt switch in the interpretation of a swinging body from constrained fall to time metre. But the new interpretation did not eliminate the older one. The constrained fall, both in the motion of pendulums and along inclined planes, led Galileo to the law of free fall. Experimenting with physical…
Solving constrained minimax problem via nonsmooth equations method
Institute of Scientific and Technical Information of China (English)
GUO Xiu-xia(郭修霞)
2004-01-01
A new nonsmooth equations model of constrained minimax problem was derived. The generalized Newton method was applied for solving this system of nonsmooth equations system. A new algorithm for solving constrained minimax problem was established. The local superlinear and quadratic convergences of the algorithm were discussed.
Logical consistency and sum-constrained linear models
van Perlo -ten Kleij, Frederieke; Steerneman, A.G.M.; Koning, Ruud H.
2006-01-01
A topic that has received quite some attention in the seventies and eighties is logical consistency of sum-constrained linear models. Loosely defined, a sum-constrained model is logically consistent if the restrictions on the parameters and explanatory variables are such that the sum constraint is a
Constraining Cosmic Evolution of Type Ia Supernovae
Energy Technology Data Exchange (ETDEWEB)
Foley, Ryan J.; Filippenko, Alexei V.; Aguilera, C.; Becker, A.C.; Blondin, S.; Challis, P.; Clocchiatti, A.; Covarrubias, R.; Davis, T.M.; Garnavich, P.M.; Jha, S.; Kirshner, R.P.; Krisciunas, K.; Leibundgut, B.; Li, W.; Matheson, T.; Miceli, A.; Miknaitis, G.; Pignata, G.; Rest, A.; Riess, A.G.; /UC, Berkeley, Astron. Dept. /Cerro-Tololo InterAmerican Obs. /Washington U., Seattle, Astron. Dept. /Harvard-Smithsonian Ctr. Astrophys. /Chile U., Catolica /Bohr Inst. /Notre Dame U. /KIPAC, Menlo Park /Texas A-M /European Southern Observ. /NOAO, Tucson /Fermilab /Chile U., Santiago /Harvard U., Phys. Dept. /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Res. Sch. Astron. Astrophys., Weston Creek /Stockholm U. /Hawaii U. /Illinois U., Urbana, Astron. Dept.
2008-02-13
We present the first large-scale effort of creating composite spectra of high-redshift type Ia supernovae (SNe Ia) and comparing them to low-redshift counterparts. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with excellent light-curve information. In addition, we have obtained 397 spectra of low-redshift SNe through a multiple-decade effort at Lick and Keck Observatories, and we have used 45 ultraviolet spectra obtained by HST/IUE. The low-redshift spectra act as a control sample when comparing to the ESSENCE spectra. In all instances, the ESSENCE and Lick composite spectra appear very similar. The addition of galaxy light to the Lick composite spectra allows a nearly perfect match of the overall spectral-energy distribution with the ESSENCE composite spectra, indicating that the high-redshift SNe are more contaminated with host-galaxy light than their low-redshift counterparts. This is caused by observing objects at all redshifts with similar slit widths, which corresponds to different projected distances. After correcting for the galaxy-light contamination, subtle differences in the spectra remain. We have estimated the systematic errors when using current spectral templates for K-corrections to be {approx}0.02 mag. The variance in the composite spectra give an estimate of the intrinsic variance in low-redshift maximum-light SN spectra of {approx}3% in the optical and growing toward the ultraviolet. The difference between the maximum-light low and high-redshift spectra constrain SN evolution between our samples to be < 10% in the rest-frame optical.
Constraining projections of summer Arctic sea ice
Directory of Open Access Journals (Sweden)
F. Massonnet
2012-11-01
Full Text Available We examine the recent (1979–2010 and future (2011–2100 characteristics of the summer Arctic sea ice cover as simulated by 29 Earth system and general circulation models from the Coupled Model Intercomparison Project, phase 5 (CMIP5. As was the case with CMIP3, a large intermodel spread persists in the simulated summer sea ice losses over the 21st century for a given forcing scenario. The 1979–2010 sea ice extent, thickness distribution and volume characteristics of each CMIP5 model are discussed as potential constraints on the September sea ice extent (SSIE projections. Our results suggest first that the future changes in SSIE with respect to the 1979–2010 model SSIE are related in a complicated manner to the initial 1979–2010 sea ice model characteristics, due to the large diversity of the CMIP5 population: at a given time, some models are in an ice-free state while others are still on the track of ice loss. However, in phase plane plots (that do not consider the time as an independent variable, we show that the transition towards ice-free conditions is actually occurring in a very similar manner for all models. We also find that the year at which SSIE drops below a certain threshold is likely to be constrained by the present-day sea ice properties. In a second step, using several adequate 1979–2010 sea ice metrics, we effectively reduce the uncertainty as to when the Arctic could become nearly ice-free in summertime, the interval [2041, 2060] being our best estimate for a high climate forcing scenario.
The cost-constrained traveling salesman problem
Energy Technology Data Exchange (ETDEWEB)
Sokkappa, P.R.
1990-10-01
The Cost-Constrained Traveling Salesman Problem (CCTSP) is a variant of the well-known Traveling Salesman Problem (TSP). In the TSP, the goal is to find a tour of a given set of cities such that the total cost of the tour is minimized. In the CCTSP, each city is given a value, and a fixed cost-constraint is specified. The objective is to find a subtour of the cities that achieves maximum value without exceeding the cost-constraint. Thus, unlike the TSP, the CCTSP requires both selection and sequencing. As a consequence, most results for the TSP cannot be extended to the CCTSP. We show that the CCTSP is NP-hard and that no K-approximation algorithm or fully polynomial approximation scheme exists, unless P = NP. We also show that several special cases are polynomially solvable. Algorithms for the CCTSP, which outperform previous methods, are developed in three areas: upper bounding methods, exact algorithms, and heuristics. We found that a bounding strategy based on the knapsack problem performs better, both in speed and in the quality of the bounds, than methods based on the assignment problem. Likewise, we found that a branch-and-bound approach using the knapsack bound was superior to a method based on a common branch-and-bound method for the TSP. In our study of heuristic algorithms, we found that, when selecting modes for inclusion in the subtour, it is important to consider the neighborhood'' of the nodes. A node with low value that brings the subtour near many other nodes may be more desirable than an isolated node of high value. We found two types of repetition to be desirable: repetitions based on randomization in the subtour buildings process, and repetitions encouraging the inclusion of different subsets of the nodes. By varying the number and type of repetitions, we can adjust the computation time required by our method to obtain algorithms that outperform previous methods.
Diba, Kamran; Buzsáki, György
2008-01-01
The hippocampus provides a spatial map of the environment. Changes in the environment alter the firing patterns of hippocampal neurons, but are presumably constrained by elements of the network dynamics. We compared the neural activity in CA1 and CA3 regions of the hippocampus in rats running for water reward on a linear track, before and after the track length was shortened. A fraction of cells lost their place-fields and new sets of cells with fields emerged, indicating distinct representation of the two tracks. Cells active in both environments shifted their place-fields in a location dependent manner, most notably at the beginning and the end of the track. Furthermore, peak firing rates and place-field sizes decreased, while place-field overlap and co-activity increased. Power in the theta-frequency band of the local field potentials also decreased in both CA1 and CA3, along with the coherence between the two structures. In contrast, the theta-scale (0–150 ms) time lags between cell pairs, representing distances on the tracks, were conserved, and the activity of the inhibitory neuron population was maintained across environments. We interpret these observations as reflecting the freedoms and constraints of the hippocampal network dynamics. The freedoms permit the necessary flexibility for the network to distinctly represent unique patterns, while the dynamics constrain the speed at which activity propagates between the cell assemblies representing the patterns. PMID:19074018
A constrained conjugate gradient algorithm for computed tomography
Energy Technology Data Exchange (ETDEWEB)
Azevedo, S.G.; Goodman, D.M. [Lawrence Livermore National Lab., CA (United States)
1994-11-15
Image reconstruction from projections of x-ray, gamma-ray, protons and other penetrating radiation is a well-known problem in a variety of fields, and is commonly referred to as computed tomography (CT). Various analytical and series expansion methods of reconstruction and been used in the past to provide three-dimensional (3D) views of some interior quantity. The difficulties of these approaches lie in the cases where (a) the number of views attainable is limited, (b) the Poisson (or other) uncertainties are significant, (c) quantifiable knowledge of the object is available, but not implementable, or (d) other limitations of the data exist. We have adapted a novel nonlinear optimization procedure developed at LLNL to address limited-data image reconstruction problems. The technique, known as nonlinear least squares with general constraints or constrained conjugate gradients (CCG), has been successfully applied to a number of signal and image processing problems, and is now of great interest to the image reconstruction community. Previous applications of this algorithm to deconvolution problems and x-ray diffraction images for crystallography have shown the great promise.
Constraining the primordial initial mass function with stellar archaeology
Hartwig, Tilman; Klessen, Ralf S; Glover, Simon C O
2014-01-01
We present a new near-field cosmological probe of the initial mass function (IMF) of the first stars. Specifically, we constrain the lower-mass limit of the Population III (Pop III) IMF with the total number of stars in large, unbiased surveys of the Milky Way bulge and halo. We model the early star formation history in a Milky-Way like halo with a semi-analytic approach, based on Monte-Carlo sampling of dark matter merger trees, combined with a treatment of the most important feedback mechanisms, such as stellar radiation and metal enrichment. Assuming a logarithmically flat Pop III IMF and varying its low mass limit, we derive the number of expected survivors of these first stars, using them to estimate the probability to detect any such Pop III fossil in stellar archaeological surveys. Our model parameters are calibrated with existing empirical constraints, such as the optical depth to Thomson scattering. Following our analysis, the most promising region to find possible Pop III survivors is the stellar ha...
Segmentation in cohesive systems constrained by elastic environments
Novak, I.; Truskinovsky, L.
2017-04-01
The complexity of fracture-induced segmentation in elastically constrained cohesive (fragile) systems originates from the presence of competing interactions. The role of discreteness in such phenomena is of interest in a variety of fields, from hierarchical self-assembly to developmental morphogenesis. In this paper, we study the analytically solvable example of segmentation in a breakable mass-spring chain elastically linked to a deformable lattice structure. We explicitly construct the complete set of local minima of the energy in this prototypical problem and identify among them the states corresponding to the global energy minima. We show that, even in the continuum limit, the dependence of the segmentation topology on the stretching/pre-stress parameter in this problem takes the form of a devil's type staircase. The peculiar nature of this staircase, characterized by locking in rational microstructures, is of particular importance for biological applications, where its structure may serve as an explanation of the robustness of stress-driven segmentation. This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.'
Sampling from stochastic reservoir models constrained by production data
Energy Technology Data Exchange (ETDEWEB)
Hegstad, Bjoern Kaare
1997-12-31
When a petroleum reservoir is evaluated, it is important to forecast future production of oil and gas and to assess forecast uncertainty. This is done by defining a stochastic model for the reservoir characteristics, generating realizations from this model and applying a fluid flow simulator to the realizations. The reservoir characteristics define the geometry of the reservoir, initial saturation, petrophysical properties etc. This thesis discusses how to generate realizations constrained by production data, that is to say, the realizations should reproduce the observed production history of the petroleum reservoir within the uncertainty of these data. The topics discussed are: (1) Theoretical framework, (2) History matching, forecasting and forecasting uncertainty, (3) A three-dimensional test case, (4) Modelling transmissibility multipliers by Markov random fields, (5) Up scaling, (6) The link between model parameters, well observations and production history in a simple test case, (7) Sampling the posterior using optimization in a hierarchical model, (8) A comparison of Rejection Sampling and Metropolis-Hastings algorithm, (9) Stochastic simulation and conditioning by annealing in reservoir description, and (10) Uncertainty assessment in history matching and forecasting. 139 refs., 85 figs., 1 tab.
Constrained spacecraft reorientation using mixed integer convex programming
Tam, Margaret; Glenn Lightsey, E.
2016-10-01
A constrained attitude guidance (CAG) system is developed using convex optimization to autonomously achieve spacecraft pointing objectives while meeting the constraints imposed by on-board hardware. These constraints include bounds on the control input and slew rate, as well as pointing constraints imposed by the sensors. The pointing constraints consist of inclusion and exclusion cones that dictate permissible orientations of the spacecraft in order to keep objects in or out of the field of view of the sensors. The optimization scheme drives a body vector towards a target inertial vector along a trajectory that consists solely of permissible orientations in order to achieve the desired attitude for a given mission mode. The non-convex rotational kinematics are handled by discretization, which also ensures that the quaternion stays unity norm. In order to guarantee an admissible path, the pointing constraints are relaxed. Depending on how strict the pointing constraints are, the degree of relaxation is tuneable. The use of binary variables permits the inclusion of logical expressions in the pointing constraints in the case that a set of sensors has redundancies. The resulting mixed integer convex programming (MICP) formulation generates a steering law that can be easily integrated into an attitude determination and control (ADC) system. A sample simulation of the system is performed for the Bevo-2 satellite, including disturbance torques and actuator dynamics which are not modeled by the controller. Simulation results demonstrate the robustness of the system to disturbances while meeting the mission requirements with desirable performance characteristics.
Constraining Numerical Geodynamo Modeling with Surface Observations
Kuang, Weijia; Tangborn, Andrew
2006-01-01
Numerical dynamo solutions have traditionally been generated entirely by a set of self-consistent differential equations that govern the spatial-temporal variation of the magnetic field, velocity field and other fields related to dynamo processes. In particular, those solutions are obtained with parameters very different from those appropriate for the Earth s core. Geophysical application of the numerical results therefore depends on correct understanding of the differences (errors) between the model outputs and the true states (truth) in the outer core. Part of the truth can be observed at the surface in the form of poloidal magnetic field. To understand these differences, or errors, we generate new initial model state (analysis) by assimilating sequentially the model outputs with the surface geomagnetic observations using an optimal interpolation scheme. The time evolution of the core state is then controlled by our MoSST core dynamics model. The final outputs (forecasts) are then compared with the surface observations as a means to test the success of the assimilation. We use the surface geomagnetic data back to year 1900 for our studies, with 5-year forecast and 20-year analysis periods. We intend to use the result; to understand time variation of the errors with the assimilation sequences, and the impact of the assimilation on other unobservable quantities, such as the toroidal field and the fluid velocity in the core.
Constraining Water Quality Models With Electrical Resistivity Tomography (ERT)
Bentley, L. R.; Gharibi, M.; Mrklas, O.; Lunn, S. D.
2001-12-01
Water quality models are difficult to constrain with piezometer data alone because the data are spatially sparse. Since the electrical conductivity (EC) of water is often correlated with water quality, geophysical measurements of electrical conductivity may provide densely sampled secondary data for constraining water quality models. We present a quantitative interpretation protocol for interpreting EC derived from surface ERT results. A standard temperature is selected that is in the range of the in situ field temperatures, and laboratory measurements establish a functional relationship between water EC and temperature. Total meq/l of charge are often strongly correlated with water EC at the standard temperature. Laboratory data is used to develop a correlation model between indicator parameters or water chemistry evolution and total meq/l of charge. Since the solid phase may contain a conductive clay fraction, a site specific calibrated Waxman-Smits rock physics model is used to estimate groundwater EC from bulk EC derived from ERT inversions. The groundwater EC at in situ temperature is converted to EC at the standard temperature, and the total meq/l is estimated using the laboratory-established correlation. The estimated meq/l can be used as soft information to map distribution of water quality or to estimate changes to water chemistry with time. We apply the analysis to a decommissioned sour gas plant undergoing remediation. Background bulk EC is high (50 to 100 mS/m) due to the clay content of tills. The highest values of groundwater EC are mainly due to acetic acid, which is a degradation product of amines and glycols. Acetic acid degrades readily under aerobic conditions, lowering the EC of pore waters. The calibrated Waxman-Smits model predicts that a reduction of groundwater EC from 1600 mS/m to 800mS/m will result in a reduction of bulk EC from 150 mS/m to 110 mS/m. Groundwater EC values both increase and decrease with time due to site heterogeneity, and
Chance-Constrained Guidance With Non-Convex Constraints
Ono, Masahiro
2011-01-01
Missions to small bodies, such as comets or asteroids, require autonomous guidance for descent to these small bodies. Such guidance is made challenging by uncertainty in the position and velocity of the spacecraft, as well as the uncertainty in the gravitational field around the small body. In addition, the requirement to avoid collision with the asteroid represents a non-convex constraint that means finding the optimal guidance trajectory, in general, is intractable. In this innovation, a new approach is proposed for chance-constrained optimal guidance with non-convex constraints. Chance-constrained guidance takes into account uncertainty so that the probability of collision is below a specified threshold. In this approach, a new bounding method has been developed to obtain a set of decomposed chance constraints that is a sufficient condition of the original chance constraint. The decomposition of the chance constraint enables its efficient evaluation, as well as the application of the branch and bound method. Branch and bound enables non-convex problems to be solved efficiently to global optimality. Considering the problem of finite-horizon robust optimal control of dynamic systems under Gaussian-distributed stochastic uncertainty, with state and control constraints, a discrete-time, continuous-state linear dynamics model is assumed. Gaussian-distributed stochastic uncertainty is a more natural model for exogenous disturbances such as wind gusts and turbulence than the previously studied set-bounded models. However, with stochastic uncertainty, it is often impossible to guarantee that state constraints are satisfied, because there is typically a non-zero probability of having a disturbance that is large enough to push the state out of the feasible region. An effective framework to address robustness with stochastic uncertainty is optimization with chance constraints. These require that the probability of violating the state constraints (i.e., the probability of
Patterning and structural engineering of dimensionally constrained functional oxide nanostructures
Pan, Zixiao
deposition profile in VP-eBL and demonstrated successful fabrication of architectures spaning 0-dimensional dots, 1-dimensional lines, 2-dimensional high density grids, and 3-dimensional heterostructures. Embedded in these efforts were varied site-specific characterizations on the nanostructures. Our initial study using x-ray microdiffraction indicated localized deformation field induced in the substrate at vicinity of epitaxial pattern edges. Our approach of building and tailoring nano-constrained functional oxides is highly flexible, serving for a wide variety of materials and diverse types of architectures. The protocol reported in this dissertation lays the groundwork for in-depth exploration of the rich phenomena related to spatial/dimensional confinement. Further refinement of our strategy may provide an effective tool to harness the technological opportunities of diverse functional materials and pave the way for innovative applications which require nanopatterned architectures.
Indian Academy of Sciences (India)
Wen Debao; Liu Sanzhi
2010-08-01
For the limitation of the conventional multiplicative algebraic reconstruction technique (MART), a constrained MART (CMART) is proposed in this paper. In the new tomographic algorithm, a popular two-dimensional multi-point finite difference approximation of the second order Laplacian operator is used to smooth the electron density field. The feasibility and superiority of the new method are demonstrated by using the numerical simulation experiment. Finally, the CMART is used to reconstruct the regional electron density field by using the actual GNSS data under geomagnetic quiet and disturbed days. The available ionosonde data from Beijing station further validates the superiority of the new method.
Wen, Debao; Liu, Sanzhi
2010-08-01
For the limitation of the conventional multiplicative algebraic reconstruction technique (MART), a constrained MART (CMART) is proposed in this paper. In the new tomographic algorithm, a popular two-dimensional multi-point finite difference approximation of the second order Laplacian operator is used to smooth the electron density field. The feasibility and superiority of the new method are demonstrated by using the numerical simulation experiment. Finally, the CMART is used to reconstruct the regional electron density field by using the actual GNSS data under geomagnetic quiet and disturbed days. The available ionosonde data from Beijing station further validates the superiority of the new method.
Wave speed in excitable random networks with spatially constrained connections.
Directory of Open Access Journals (Sweden)
Nikita Vladimirov
Full Text Available Very fast oscillations (VFO in neocortex are widely observed before epileptic seizures, and there is growing evidence that they are caused by networks of pyramidal neurons connected by gap junctions between their axons. We are motivated by the spatio-temporal waves of activity recorded using electrocorticography (ECoG, and study the speed of activity propagation through a network of neurons axonally coupled by gap junctions. We simulate wave propagation by excitable cellular automata (CA on random (Erdös-Rényi networks of special type, with spatially constrained connections. From the cellular automaton model, we derive a mean field theory to predict wave propagation. The governing equation resolved by the Fisher-Kolmogorov PDE fails to describe wave speed. A new (hyperbolic PDE is suggested, which provides adequate wave speed v( that saturates with network degree , in agreement with intuitive expectations and CA simulations. We further show that the maximum length of connection is a much better predictor of the wave speed than the mean length. When tested in networks with various degree distributions, wave speeds are found to strongly depend on the ratio of network moments / rather than on mean degree , which is explained by general network theory. The wave speeds are strikingly similar in a diverse set of networks, including regular, Poisson, exponential and power law distributions, supporting our theory for various network topologies. Our results suggest practical predictions for networks of electrically coupled neurons, and our mean field method can be readily applied for a wide class of similar problems, such as spread of epidemics through spatial networks.
KINETIC CONSEQUENCES OF CONSTRAINING RUNNING BEHAVIOR
Directory of Open Access Journals (Sweden)
John A. Mercer
2005-06-01
Full Text Available It is known that impact forces increase with running velocity as well as when stride length increases. Since stride length naturally changes with changes in submaximal running velocity, it was not clear which factor, running velocity or stride length, played a critical role in determining impact characteristics. The aim of the study was to investigate whether or not stride length influences the relationship between running velocity and impact characteristics. Eight volunteers (mass=72.4 ± 8.9 kg; height = 1.7 ± 0.1 m; age = 25 ± 3.4 years completed two running conditions: preferred stride length (PSL and stride length constrained at 2.5 m (SL2.5. During each condition, participants ran at a variety of speeds with the intent that the range of speeds would be similar between conditions. During PSL, participants were given no instructions regarding stride length. During SL2.5, participants were required to strike targets placed on the floor that resulted in a stride length of 2.5 m. Ground reaction forces were recorded (1080 Hz as well as leg and head accelerations (uni-axial accelerometers. Impact force and impact attenuation (calculated as the ratio of head and leg impact accelerations were recorded for each running trial. Scatter plots were generated plotting each parameter against running velocity. Lines of best fit were calculated with the slopes recorded for analysis. The slopes were compared between conditions using paired t-tests. Data from two subjects were dropped from analysis since the velocity ranges were not similar between conditions resulting in the analysis of six subjects. The slope of impact force vs. velocity relationship was different between conditions (PSL: 0.178 ± 0.16 BW/m·s-1; SL2.5: -0.003 ± 0.14 BW/m·s-1; p < 0.05. The slope of the impact attenuation vs. velocity relationship was different between conditions (PSL: 5.12 ± 2.88 %/m·s-1; SL2.5: 1.39 ± 1.51 %/m·s-1; p < 0.05. Stride length was an important factor
Generation of Granulites Constrained by Thermal Modeling
Depine, G. V.; Andronicos, C. L.; Phipps-Morgan, J.
2006-12-01
The heat source needed to generate granulites facies metamorphism is still an unsolved problem in geology. There is a close spatial relationship between granulite terrains and extensive silicic plutonism, suggesting heat advection by melts is critical to their formation. To investigate the role of heat advection by melt in the generation of granulites we use numerical 1-D models which include the movement of melt from the base of the crust to the middle crust. The model is in part constrained by petrological observations from the Coast Plutonic Complex (CPC) in British Columbia, Canada at ~ 54° N where migmatite and granulite are widespread. The model takes into account time dependent heat conduction and advection of melts generated at the base of the crust. The model starts with a crust of 55 km, consistent with petrologic and geochemical data from the CPC. The lower crust is assumed to be amphibolite in composition, consistent with seismologic and geochemical constraints for the CPC. An initial geothermal gradient estimated from metamorphic P-T-t paths in this region is ~37°C/km, hotter than normal geothermal gradients. The parameters used for the model are a coefficient of thermal conductivity of 2.5 W/m°C, a density for the crust of 2700 kg/m3 and a heat capacity of 1170 J/Kg°C. Using the above starting conditions, a temperature of 1250°C is assumed for the mantle below 55 km, equivalent to placing asthenosphere in contact with the base of the crust to simulate delamination, basaltic underplating and/or asthenospheric exposure by a sudden steepening of slab. This condition at 55 km results in melting the amphibolite in the lower crust. Once a melt fraction of 10% is reached the melt is allowed to migrate to a depth of 13 km, while material at 13 km is displaced downwards to replace the ascending melts. The steady-state profile has a very steep geothermal gradient of more than 50°C/km from the surface to 13 km, consistent with the generation of andalusite
Onomatopoeia characters extraction from comic images using constrained Delaunay triangulation
Liu, Xiangping; Shoji, Kenji; Mori, Hiroshi; Toyama, Fubito
2014-02-01
A method for extracting onomatopoeia characters from comic images was developed based on stroke width feature of characters, since they nearly have a constant stroke width in a number of cases. An image was segmented with a constrained Delaunay triangulation. Connected component grouping was performed based on the triangles generated by the constrained Delaunay triangulation. Stroke width calculation of the connected components was conducted based on the altitude of the triangles generated with the constrained Delaunay triangulation. The experimental results proved the effectiveness of the proposed method.
Processing Constrained K Closest Pairs Query in Spatial Databases
Institute of Scientific and Technical Information of China (English)
LIU Xiaofeng; LIU Yunsheng; XIAO Yingyuan
2006-01-01
In this paper, constrained K closest pairs query is introduced, which retrieves the K closest pairs satisfying the given spatial constraint from two datasets. For data sets indexed by R-trees in spatial databases, three algorithms are presented for answering this kind of query. Among of them,two-phase Range+Join and Join+Range algorithms adopt the strategy that changes the execution order of range and closest pairs queries, and constrained heap-based algorithm utilizes extended distance functions to prune search space and minimize the pruning distance. Experimental results show that constrained heap-base algorithm has better applicability and performance than two-phase algorithms.
Sundance: High-Level Software for PDE-Constrained Optimization
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Kevin Long
2012-01-01
Full Text Available Sundance is a package in the Trilinos suite designed to provide high-level components for the development of high-performance PDE simulators with built-in capabilities for PDE-constrained optimization. We review the implications of PDE-constrained optimization on simulator design requirements, then survey the architecture of the Sundance problem specification components. These components allow immediate extension of a forward simulator for use in an optimization context. We show examples of the use of these components to develop full-space and reduced-space codes for linear and nonlinear PDE-constrained inverse problems.
Solving constrained traveling salesman problems by genetic algorithms
Institute of Scientific and Technical Information of China (English)
WU Chunguo; LIANG Yanchun; LEE Heowpueh; LU Chun; LIN Wuzhong
2004-01-01
Three kinds of constrained traveling salesman problems (TSP) arising from application problems, namely the open route TSP, the end-fixed TSP, and the path-constrained TSP, are proposed. The corresponding approaches based on modified genetic algorithms (GA) for solving these constrained TSPs are presented. Numerical experiments demonstrate that the algorithm for the open route TSP shows its advantages when the open route is required, the algorithm for the end-fixed TSP can deal with route optimization with constraint of fixed ends effectively, and the algorithm for the path-constraint could benefit the traffic problems where some cities cannot be visited from each other.
Constraining Torsion with Gravity Probe B
Mao, Y; Guth, A H; Tegmark, M; Cabi, Serkan; Guth, Alan; Mao, Yi; Tegmark, Max
2006-01-01
It is well-entrenched folklore that torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally. We give an explicit counterexample where a rotating body generates a torsion field in Weitzenbock spacetime with a Hayashi-Shirafuji Lagrangian. More generally, in the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope should also feel torsion. Using symmetry arguments, we show that to lowest order, the torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the PPN formalism and provide a concrete framework for further testing GR. We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shira...