503 research outputs found
Transport in Coupled Quantum Dots: Kondo Effect Versus Anti-Ferromagnetic Correlation
The interplay between the Kondo effect and the inter-dot magnetic interaction
in a coupled-dot system is studied. An exact result for the transport
properties at zero temperature is obtained by diagonalizing a cluster, composed
by the double-dot and its vicinity, which is connected to leads. It is shown
that the system goes continuously from the Kondo regime to an
anti-ferromagnetic state as the inter-dot interaction is increased. The
conductance, the charge at the dots and the spin-spin correlation are obtained
as a function of the gate potential.Comment: 4 pages, 3 postscript figures. Submitted to PR
AlcalĂłides de Duguetia trunciflora Maas (Annonaceae)
From the ethanolic extract of the leaves and thin branches of Duguetia trunciflora Maas (Annonaceae) six alkaloids were isolated, being one benzylisoquinoline: reticulineÂč, four tetrahydroprotoberberine:,tetrahydro-palmatineÂČ, tetrahydrojathrorrizineÂł, discretamine4, thaicanine5, and one berberine: jathrorrizine6. These alkaloids were identified through ÂčH and 13C NMR spectroscopic technics. The alkaloids 1, 3, 5 and 6 are being cited for the first time on Duguetia genus
Cosmic coincidence problem and variable constants of physics
The standard model of cosmology is investigated using time dependent
cosmological constant and Newton's gravitational constant . The
total energy content is described by the modified Chaplygin gas equation of
state. It is found that the time dependent constants coupled with the modified
Chaplygin gas interpolate between the earlier matter to the later dark energy
dominated phase of the universe. We also achieve a convergence of parameter
, with minute fluctuations, showing an evolving . Thus our
model fairly alleviates the cosmic coincidence problem which demands
at present time.Comment: 27 pages, 15 figure
Dynamics of interacting phantom and quintessence dark energies
We present models, in which phantom energy interacts with two different types
of dark energies including variable modified Chaplygin gas (VMCG) and new
modified Chaplygin gas (NMCG). We then construct potentials for these cases. It
has been shown that the potential of the phantom field decreases from a higher
value with the evolution of the Universe.Comment: 7 pages, 6 figures, accepted for publication in Astrophysics and
Space Scienc
Impactos ambientais do manejo agroecolĂłgico da caatinga no Rio Grande do Norte.
O objetivo deste trabalho foi avaliar os impactos ambientais do manejo agroecolĂłgico da caatinga, em unidades de produção familiar no Rio Grande do Norte, pelo mĂ©todo Ambitec de produção animal - dimensĂŁo ambiental, desenvolvido pela Embrapa Meio Ambiente. Foram avaliadas sete unidades de produção familiar, em quatro projetos de assentamentos de reforma agrĂĄria do MunicĂpio de Apodi, RN. Os dados para o levantamento foram obtidos por meio de questionĂĄrios aplicados aos representantes das unidades produtivas familiares, que atribuĂram, a cada variĂĄvel estudada, um valor que representou a alteração proporcionada pela implementação da tecnologia. ApĂłs a inserção dos coeficientes de alteração de cada variĂĄvel dos indicadores por unidade de produção, o coeficiente de impacto foi automaticamente calculado por meio da planilha Ambitec. O manejo agroecolĂłgico da caatinga resultou num impacto ambiental positivo, e suas maiores contribuiçÔes foram relacionadas aos efeitos positivos dos seguintes indicadores: capacidade produtiva do solo, uso de insumos materiais, qualidade do produto e diminuição da emissĂŁo de poluentes Ă atmosfera. Dois indicadores geraram efeitos negativos: o uso de energia e o uso de recursos naturais. Pela superioridade dos benefĂcios gerados, o manejo agroecolĂłgico da caatinga Ă© uma inovação tecnolĂłgica geradora de impactos ambientais positivos
Evolution of the differential transverse momentum correlation function with centrality in Au+Au collisions at GeV
We present first measurements of the evolution of the differential transverse
momentum correlation function, {\it C}, with collision centrality in Au+Au
interactions at GeV. {\it C} exhibits a strong dependence
on collision centrality that is qualitatively similar to that of number
correlations previously reported. We use the observed longitudinal broadening
of the near-side peak of {\it C} with increasing centrality to estimate the
ratio of the shear viscosity to entropy density, , of the matter formed
in central Au+Au interactions. We obtain an upper limit estimate of
that suggests that the produced medium has a small viscosity per unit entropy.Comment: 7 pages, 4 figures, STAR paper published in Phys. Lett.
Drawing lines at the sand: evidence for functional vs. visual reef boundaries in temperate Marine Protected Areas.
Marine Protected Areas (MPAs) can either protect all seabed habitats within them or discrete features. If discrete features within the MPA are to be protected humans have to know where the boundaries are. In Lyme Bay, SW England a MPA excluded towed demersal fishing gear from 206 km(2) to protect rocky reef habitats and the associated species. The site comprised a mosaic of sedimentary and reef habitats and so 'non reef' habitat also benefited from the MPA. Following 3 years protection, video data showed that sessile Reef Associated Species (RAS) had colonised sedimentary habitat indicating that 'reef' was present. This suggested that the functional extent of the reef was potentially greater than its visual boundary. Feature based MPA management may not adequately protect targeted features, whereas site based management allows for shifting baselines and will be more effective at delivering ecosystem goods and services
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
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