Two-branes with variable tension model and the effective Newtonian constant

It is shown that, in the two brane time variation model framework, if the hidden brane tension varies according to the phenomenological Eotvos law, the visible brane tension behavior is such that its time derivative is negative in the past and positive after a specific time of cosmological evolution. This behavior is interpreted in terms of an useful mechanical system analog and its relation with the variation of the Newtonian (effective) gravitational `constant' is explored.Comment: 15 pages, no figure, accepted for publication in Physical Review

Notes on the Two-brane Model with Variable Tension

Motivated by possible extensions of the braneworld models with two branes, we investigate some consequences of a variable brane tension using the well established results on consistency conditions. By a slight modification of the usual stress-tensor used in order to derive the braneworld sum rules, we find out some important constraints obeyed by time dependent brane tensions. In particular it is shown that the tensions of two Randall-Sundrum like branes obeying, at the same time, an Eotvos law, aggravate the fine tuning problem. Also, it is shown that if the hidden brane tension obeys an Eotvos law, then the visible brane has a mixed behavior allowing a bouncing-like period at early times while it is dominated by an Eotvos law nowadays. To finalize, we discuss some qualitative characteristics which may arise in the scope of dynamical brane tensions, as anisotropic background and branons production.Comment: 7 pages, 1 figure, accepted for publication in Physical Review

Electrodynamics of Media

Contains reports on two research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E)M. I. T. Sloan Fund for Basic ResearchNational Science Foundation (Grant GK-3370

Attosecond control of electron dynamics in carbon monoxide

Laser pulses with stable electric field waveforms establish the opportunity to achieve coherent control on attosecond timescales. We present experimental and theoretical results on the steering of electronic motion in a multi-electron system. A very high degree of light-waveform control over the directional emission of C+ and O+ fragments from the dissociative ionization of CO was observed. Ab initio based model calculations reveal contributions to the control related to the ionization and laser-induced population transfer between excited electronic states of CO+ during dissociation

Discovery of seven T Tauri stars and a brown dwarf candidate in the nearby TW Hydrae Association

We report the discovery of five T Tauri star systems, two of which are resolved binaries, in the vicinity of the nearest known region of recent star formation, the TW Hydrae Association. The newly discovered systems display the same signatures of youth (namely high X-ray flux, large Li abundance and strong chromospheric activity) and the same proper motion as the original five members. These similarities firmly establish the group as a bona fide T Tauri association, unique in its proximity to Earth and its complete isolation from any known molecular clouds. At an age of ~10 Myr and a distance of ~50 pc, the association members are excellent candidates for future studies of circumstellar disk dissipation and the formation of brown dwarfs and planets. Indeed, as an example, our speckle imaging revealed a faint, very likely companion 2" north of CoD-33 7795 (TWA 5). Its color and brightness suggest a spectral type ~M8.5 which, at an age of ~10^7 years, implies a mass ~20 M(Jupiter).Comment: 6 pages, 4 figures and 1 table. AAS LaTeX aas2pp4.sty. To be published in Ap

Black string corrections in variable tension braneworld scenarios

Braneworld models with variable tension are investigated, and the corrections on the black string horizon along the extra dimension are provided. Such corrections are encrypted in additional terms involving the covariant derivatives of the variable tension on the brane, providing profound consequences concerning the black string horizon variation along the extra dimension, near the brane. The black string horizon behavior is shown to be drastically modified by the terms corrected by the brane variable tension. In particular, a model motivated by the phenomenological interesting case regarding Eotvos branes is investigated. It forthwith provides further physical features regarding variable tension braneworld scenarios, heretofore concealed in all previous analysis in the literature. All precedent analysis considered uniquely the expansion of the metric up to the second order along the extra dimension, what is able to evince solely the brane variable tension absolute value. Notwithstanding, the expansion terms aftermath, further accomplished in this paper from the third order on, elicits the successive covariant derivatives of the brane variable tension, and their respective coupling with the extrinsic curvature, the Weyl tensor, and the Riemann and Ricci tensors, as well as the scalar curvature. Such additional terms are shown to provide sudden modifications in the black string horizon in a variable tension braneworld scenarioComment: 12 pages, 5 figures, accepted in PR

Geologia: um critério do meio físico para estabelecimento de indicações geográficas de vinhos finos na Serra Gaúcha, RS, Brasil.

O desenvolvimento da vitivinicultura no Brasil tem sido associado a pesquisas lideradas pela Embrapa Uva e Vinho e seus parceiros, a fim de desenvolver indicações geográficas (IG), a primeira delas sendo Vale dos Vinhedos. Este ativo de propriedade intelectual segue requisitos legais e técnicos, incluindo identidade geográfica.Resumo

Wake-Tailplane Interaction of a Slingsby Firefly Aircraft

This paper presents in-flight measurements of the interaction of the wing wake of a stalled Slingsby T67 Firefly light aircraft with the aircraft tailplane. Tailplane data was recorded by a GoPro360 camera and analyzed using spatial correlation methods. The tailplane movement and corresponding spectra indicate that the aerodynamic wake shedding frequency closely matches the resonant frequency of the tailplane, resulting in a significant excitation of the structure during heavy stall. Large magnitude, lower frequency tailplane movement was also identified by analysis of the pitch attitude from the image data, with results consistent in post-stall behavior reported by previous modelling and measurements

Unsteady aerodynamics analysis and modelling of a Slingsby Firefly aircraft:Detached-Eddy Simulation model and flight test validation

This paper presents unsteady stall characteristics of a Slingsby T67M260 Fire y light aircraft from both a computational uid dynamics (CFD) half model and ight tests. Initial results from the steady CFD, based on a RANS k . ! SST turbulence model, established the critical angle of attack of the stall to be stall = 16 , with a maximum lift coe cient of CLmax = 1.2. Comparisons with straight and level ight test data were comparable up to = 12 { 14 , with the increasing deviation at higher attributed to the e ect of the propeller slipstream under these ight conditions. The RANS CFD model was then extended to an unsteady Detached-Eddy Simulation (DES) model for three angles of attack at pre-stall and stall condition ( = 14 , 16 , 18 ), with analysis of the vortex shedding frequency. Further comparisons were then made with ight test data taken using on-board accelerometers and wing tuft surface ow visualization, at a stalled condition at equivalent . These unsteady CFD data established a dominant shedding frequency ranging from 11.7 Hz { 8.74 Hz with increasing and a Strouhal number based on wing chord of St = 0.11, which when compared to flight test accelerometer spectra matched within 2.9% of the measured frequenc

Integração de dados em SIG - geológicos e sensoriamento remoto na caracterização da IG Farroupilha para vinhos de qualidade, RS, Brasil.

Este trabalho visou elaborar uma base geológica da IG Farroupilha, a fim de contribuir com a delimitação da mesma, integrando e processando os dados num sistema de informações geográficas