3,762 research outputs found
Geodiversidade e viticultura: identidade regional e terroir vitivinÃcola no Estado do Rio Grande do Sul, Brasil.
O Rio Grande do Sul(RS) tem uma geodiversidade que induzà formação de solos e terrenos, incluindo os fatores naturais e culturais que implicam respostas agronômicas diferentes pela videira. Estas caracterÃsticas valorizam a produção de vinhos com qualidades únicas, que podem definir diferentes terroirs.Resumo
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
Analysis of hinterland transport strategies when exporting perishable products
Since a good hinterland connection is considered an important factor in port competitiveness, the objective of this paper is to analyse the impact of the development of hinterland transport strategies on the competitiveness of the port by taking the Port of Cape Town, the Republic of South Africa as an example. The development of transport strategies is reflected in terms of a lower cost and higher frequency of inland transport. To investigate the interplay among export products, transport, and access to a port for exporters, we use a linear programming model. The model considers both the choice of transport modes and the impacts of improved inland transport strategies. The model could easily be extended to deal with other modes or transport alternatives. It is assumed that, initially, two modes of transport – trucks and railway − are available for transportation of the export product from the farm to the port. The analysis is extended by including intermodal transportation as a combination of railway and road transport. The results of the analysis show that improving the rail services and offering more frequent rail services from the farm to the port, could lead to a better and more flexible transportation strategy. Keywords: port competitiveness, inland hinterland, dry ports, perishable products, intermodal transport, linear programmingpublishedVersio
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
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
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
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