1,200 research outputs found

    On The 5D Extra-Force according to Basini-Capozziello-Leon Formalism and five important features: Kar-Sinha Gravitational Bending of Light, Chung-Freese Superluminal Behaviour, Maartens-Clarkson Black Strings, Experimental measures of Extra Dimensions on board International Space Station(ISS) and the existence of the Particle ZZ due to a Higher Dimensional spacetime

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    We use the Conformal Metric as described in Kar-Sinha work on Gravitational Bending of Light in a 5D Spacetime to recompute the equations of the 5D Force in Basini-Capozziello-Leon Formalism and we arrive at a result that possesses some advantages. The equations of the Extra Force as proposed by Leon are now more elegant in Conformal Formalism and many algebraic terms can be simplified or even suppressed. Also we recompute the Kar-Sinha Gravitational Bending of Light affected by the presence of the Extra Dimension and analyze the Superluminal Chung-Freese Features of this Formalism describing the advantages of the Chung-Freese BraneWorld when compared to other Superluminal spacetime metrics(eg:Warp Drive) and we describe why the Extra Dimension is invisible and how the Extra Dimension could be made visible at least in theory.We also examine the Maartens-Clarkson Black Holes in 5D(Black Strings) coupled to massive Kaluza-Klein graviton modes predicted by Extra Dimensions theories and we study experimental detection of Extra Dimensions on-board LIGO and LISA Space Telescopes.We also propose the use of International Space Station(ISS) to measure the additional terms(resulting from the presence of Extra Dimensions) in the Kar-Sinha Gravitational Bending of Light in Outer Space to verify if we really lives in a Higher Dimensional Spacetime.Also we demonstrate that Particle ZZ can only exists if the 5D spacetime exists.Comment: Withdrawn: author no longer wishes to post work on arXi

    A streamwise-constant model of turbulent pipe flow

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    A streamwise-constant model is presented to investigate the basic mechanisms responsible for the change in mean flow occuring during pipe flow transition. Using a single forced momentum balance equation, we show that the shape of the velocity profile is robust to changes in the forcing profile and that both linear non-normal and nonlinear effects are required to capture the change in mean flow associated with transition to turbulence. The particularly simple form of the model allows for the study of the momentum transfer directly by inspection of the equations. The distribution of the high- and low-speed streaks over the cross-section of the pipe produced by our model is remarkably similar to one observed in the velocity field near the trailing edge of the puff structures present in pipe flow transition. Under stochastic forcing, the model exhibits a quasi-periodic self-sustaining cycle characterized by the creation and subsequent decay of "streamwise-constant puffs", so-called due to the good agreement between the temporal evolution of their velocity field and the projection of the velocity field associated with three-dimensional puffs in a frame of reference moving at the bulk velocity. We establish that the flow dynamics are relatively insensitive to the regeneration mechanisms invoked to produce near-wall streamwise vortices and that using small, unstructured background disturbances to regenerate the streamwise vortices is sufficient to capture the formation of the high- and low-speed streaks and their segregation leading to the blunting of the velocity profile characteristic of turbulent pipe flow

    The Tip of the Red Giant Branch and Distance of the Magellanic Clouds: results from the DENIS survey

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    We present a precise determination of the apparent magnitude of the tip of the red giant branch (TRGB) in the I (0.8 micron), J (1.25 micron), and K_S (2.15 micron) bands from the luminosity function of a sample of data extracted from the DENIS catalogue towards the Magellanic Clouds (Cioni et al. 2000). From the J and Ks magnitudes we derive bolometric magnitudes m_bol. We present a new algorithm for the determination of the TRGB magnitude, which we describe in detail and test extensively using Monte-Carlo simulations. We note that any method that searches for a peak in the first derivative (used by most authors) or the second derivative (used by us) of the observed luminosity function does not yield an unbiased estimate for the actual magnitude of the TRGB discontinuity. We stress the importance of correcting for this bias, which is not generally done. We combine the results of our algorithm with theoretical predictions to derive the distance modulus of the Magellanic Clouds. We obtain m-M = 18.55 (0.04 formal, 0.08 systematic) for the Large Magellanic Cloud (LMC), and m-M = 18.99 (0.03 formal, 0.08 systematic) for the Small Magellanic Cloud (SMC). These are among the most accurate determinations of these quantities currently available, which is a direct consequence of the large size of our sample and the insensitivity of near infrared observations to dust extinction.Comment: 16 pages, 8 figures, revised version, accepted for publication in A&

    Variability and spectral classification of LMC giants: results from DENIS and EROS

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    We present the first cross-identifications of sources in the near-infrared DENIS survey and in the micro-lensing EROS survey in a field of about 0.5 square degrees around the optical center (OC) of the Large Magellanic Cloud. We analyze the photometric history of these stars in the EROS data base and obtain light-curves for about 800 variables. Most of the stars are long period variables (Miras and Semi-Regulars), a few Cepheids are also present. We also present new spectroscopic data on 126 asymptotic giant branch stars in the OC field, 30 previously known and 96 newly discovered by the DENIS survey. The visible spectra are used to assign a carbon- (C-) or oxygen-rich (O-rich) nature to the observed stars on the basis of the presence of molecular bands of TiO, VO, CN, C2. For the remaining of the stars we used the (J-Ks) color to determine whether they are O-rich or C-rich. Plotting Log(period) versus Ks we find three very distinct period-luminosity relations, mainly populated by Semi-Regular of type a (SRa), b (SRb) and Mira variables. Carbon-rich stars occupy mostly the upper part of these relations. We find that 65% of the asymptotic giant branch population are long period variables (LPVs).Comment: 9 pages, 7 figures, 4 tables (2 via CDS), accepted by A&A journa

    Hidden Uq_{q}(sl(2)) x Uq_{q}(sl(2)) quantum group symmetry in two dimensional gravity

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    In a previous paper, we proposed a construction of U_q(sl(2)) quantum group symmetry generators for 2d gravity, where we took the chiral vertex operators of the theory to be the quantum group covariant ones established in earlier works. The basic idea was that the covariant fields in the spin 1/2 representation themselves can be viewed as generators, as they act, by braiding, on the other fields exactly in the required way. Here we transform this construction to the more conventional description of 2d gravity in terms of Bloch wave/Coulomb gas vertex operators, thereby establishing for the first time its quantum group symmetry properties. A U_q(sl(2))\otimes U_q(sl(2)) symmetry of a novel type emerges: The two Cartan-generator eigenvalues are specified by the choice of matrix element (bra/ket Verma-modules); the two Casimir eigenvalues are equal and specified by the Virasoro weight of the vertex operator considered; the co-product is defined with a matching condition dictated by the Hilbert space structure of the operator product. This hidden symmetry possesses a novel Hopf like structure compatible with these conditions. At roots of unity it gives the right truncation. Its (non linear) connection with the U_q(sl(2)) previously discussed is disentangled

    Pauvreté et développement : un bilan malaisé

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    Noise-induced oscillatory shuttling of NF-{\kappa}B in a two compartment IKK-NF-{\kappa}B-I{\kappa}B-A20 signaling model

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    NF-{\kappa}B is a pleiotropic protein whose nucleo-cytoplasmic trafficking is tightly regulated by multiple negative feedback loops embedded in the NF-{\kappa}B signaling network and contributes to diverse gene expression profiles important in immune cell differentiation, cell apoptosis, and innate immunity. The intracellular signaling processes and their control mechanisms, however, are susceptible to both extrinsic and intrinsic noise. In this article, we present numerical evidence for a universal dynamic behavior of NF-{\kappa}B, namely oscillatory nucleo-cytoplasmic shuttling, due to the fundamentally stochastic nature of the NF-{\kappa}B signaling network. We simulated the effect of extrinsic noise with a deterministic ODE model, using a statistical ensemble approach, generating many copies of the signaling network with different kinetic rates sampled from a biologically feasible parameter space. We modeled the effect of intrinsic noise by simulating the same networks stochastically using the Gillespie algorithm. The results demonstrate that extrinsic noise diversifies the shuttling patterns of NF-{\kappa}B response, whereas intrinsic noise induces oscillatory behavior in many of the otherwise non-oscillatory patterns. We identify two key model parameters which significantly affect the NF-{\kappa}B dynamic response and deduce a two-dimensional phase-diagram of the NF-{\kappa}B response as a function of these parameters. We conclude that if single-cell experiments are performed, a rich variety of NF-{\kappa}B response will be observed, even if population-level experiments, which average response over large numbers of cells, do not evidence oscillatory behavior.Comment: 49 pages, 12 figure

    Hydrochimie des lacs dans la région de Trinidad (Amazonie bolivienne) : influence d'un fleuve andin : le Rio Mamoré

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    La caractérisation physico-chimique des cours d'eau et des lacs de la région de Trinidad (plaine du Mamoré central) a permis de distinguer deux grands types d'eau. Les eaux d'origine andine (le Rio Mamoré et les lacs qu'il alimente) qui sont relativement bien minéralisées (> 100 mg.l-1), de type bicarbonaté calcique et avec de fortes teneurs relatives en calcium, magnésium et sulfates. Les eaux de la plaine (Rio Mocovi et les lacs peu profonds éloignés du Rio Mamoré) qui sont de type variable, toujours faiblement minéralisées (< 50 mg.l-1), et avec de fortes teneurs relatives en fer et en potassium. L'évolution de l'hydrochimie de ces différents milieux, plus ou moins proches, étudiée au cours de deux cycles hydrologiques, montre une forte influence du Rio Mamoré en période de hautes eaux (de janvier à avril) sur les milieux lacustres adjacents, liée à l'existence de zones d'inondation. (Résumé d'auteur

    Transport de matières dissoutes et particulaires des Andes vers le rio de la Planta par les tributaires boliviens (rios Pilcomayo et Bermejo) du rio Paraguay

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    Les données recueillies à 13 stations hydrométriques des réseaux du SENAMHI et de ENDE, de 1975 à 1983, permettent d'estimer les flux des matières particulaires et dissoutes dans les bassins andins des rios Pilcomayo et Bermejo, formateurs du Rio Paraguay. Les résultats obtenus en Bolivie sur le bassin versant du Rio Pilcomayo, montrent que l'essentiel de l'exportation est le fait de matières en suspension (90%). Le flux de sédiments mesuré à la sortie des Andes sur le Rio Pilcomayo (80 x 10 puissance 6 t an-1) est du même ordre de grandeur que celui observé 2 000 kilomètres à l'aval sur le Moyen Parana. (Résumé d'auteur

    Datos fisico-quimicos de los medios acuaticos de la zona del Mamoré central : region de Trinidad - Amazonia boliviana

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    La caractérisation physico-chimique des cours d'eau et des lacs de la région de Trinidad a permis de distinguer deux grands types d'eaux. Les eaux d'origine andine (le rio Mamoré et les lagunes qu'il alimente) qui sont plus minéralisées, de type bicarbonaté calcique, avec de fortes teneurs relatives en calcium, magnésium et sulfates. Les eaux de la plaine (rio Mocovi et les lagunes peu profondes éloignées du rio Mamoré) qui sont de type variable avec de fortes teneurs relatives en fer et potassium. L'évolution de l'hydrochimie de ces milieux, au cours du cycle hydrologique montre une forte influence du rio Mamoré en période de hautes eaux sur le milieu lacustre, liée aux zones d'inondation. (Résumé d'auteur
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