Superinflation, quintessence, and the avoidance of the initial singularity

We consider the dynamics of a spatially flat universe dominated by a self-interacting nonminimally coupled scalar field. The structure of the phase space and complete phase portraits for the conformal coupling case are given. It is shown that the non-minimal coupling modifies drastically the dynamics of the universe. New cosmological behaviors are identified, including superinflation ($\dot{H}>0$), avoidance of big bang singularities through classical birth of the universe from empty Minkowski space, and spontaneous entry into and exit from inflation. The relevance of this model to the description of quintessence is discussed.Comment: RevTex, 10 pages, 4 figures, To appear in the proceedings of the 5th Peyresq meetin

Stability properties and asymptotics for N non-minimally coupled scalar fields cosmology

We consider here the dynamics of some homogeneous and isotropic cosmological models with $N$ interacting classical scalar fields non-minimally coupled to the spacetime curvature, as an attempt to generalize some recent results obtained for one and two scalar fields. We show that a Lyapunov function can be constructed under certain conditions for a large class of models, suggesting that chaotic behavior is ruled out for them. Typical solutions tend generically to the empty de Sitter (or Minkowski) fixed points, and the previous asymptotic results obtained for the one field model remain valid. In particular, we confirm that, for large times and a vanishing cosmological constant, even in the presence of the extra scalar fields, the universe tends to an infinite diluted matter dominated era.Comment: 10 page

Bromeliaceae species from coastal restinga habitats, Brazilian states of Rio de Janeiro, Espírito Santo, and Bahia.

Bromeliaceae is one of the most representative plant families in restinga habitats. We analyzed the speciesrichness and composition of Bromeliaceae in 13 restinga habitats along the Brazilian coast. We found a total of 41species distributed along the restinga habitats studied. The restinga of Praia do Sul, in the state of Rio de Janeiro, hadthe highest number of species (15), whereas the restinga of Abaeté, in the state of Bahia, had the lowest (4). Our dataare suggestive that the Doce River may represent the limit of distribution for some bromeliad species, with some speciesoccurring only south of that river and others occurring only to the north of it. The differences in Bromeliaceae speciescomposition among restinga habitats probably are not only due to differences in local environmental conditions, butalso due to the geographic distribution pattern of each species and to the present degree of disturbance at each restinga

Acute Myocardial Infarction in the Puerperium

Os autores descrevem um caso clínico de paciente de 42 anos, com enfarte agudo do miocárdio (EAM) ao 3º dia de puerpério, tendo efectuado angioplastia directa. A propósito deste caso fez-se uma revisão das principais alterações fisiológicas cardiovasculares e da hemostase na gravidez, habitualmente bem toleradas pelas gestantes, mas que em mulheres com factores de risco ou com doença cardíaca prévia aumentam a probabilidade de eventos cardiovasculares. O volume sanguíneo e o débito cardíaco aumentam em média 50% durante a gestação, a concentração de hemoglobina diminui e a menor resistência vascular periférica condiciona uma queda da pressão arterial na primeira metade da gravidez. No pós parto imediato verifica-se um incremento na pressão de enchimento ventricular, volume sistólico e débito cardíaco e é no período peri-parto que o risco cardiovascular se encontra mais elevado. A incidência de EAM na gravidez e puerpério é baixa, no entanto a tendência é de aumento, tendo em conta o número crescente de gestações nos extremos da idade reprodutiva

Hypoglycemia in Pregnancy

Hypoglycemia is considered when glycemia values fall below 60 mg/dl and is associated with increased maternal-fetal morbidity and mortality. In a diabetic pregnancy this complication can result from a decrease in caloric ingestion relative to administered insulin. Hypoglycemia can present as a simple adrenergic response or as a neuroglicopenic response that can lead to maternal death and stillbirth. This is the reason why it can rapidly evolve into an obstetric emergency. It is important to possess a pre-defined protocol to guide healthcare professionals regarding the rapid management of this situation. The authors review the scientific literature on the subject of hypoglycemia in pregnancy and propose a protocol to be applied in this situation

Magnetic-field effects on transport in carbon nanotube junctions

Here we address a theoretical study on the behaviour of electronic states of heterojunctions and quantum dots based on carbon nanotubes under magnetic fields. Emphasis is put on the analysis of the local density of states, the conductance, and on the characteristic curves of current versus voltage. The heterostructures are modeled by joining zigzag tubes through single pentagon-heptagon pair defects, and described within a simple tight binding calculation. The conductance is calculated using the Landauer formula in the Green functions formalism. The used theoretical approach incorporates the atomic details of the topological defects by performing an energy relaxation via Monte Carlo calculation. The effect of a magnetic field on the conductance gap of the system is investigated and compared to those of isolated constituent tubes. It is found that the conductance gap of the studied CNHs exhibits oscillations as a function of the magnetic flux. However, unlike the pristine tubes case, they are not Aharonov-Bohm periodic oscillations

Origin of the high energy proton component below the geomagnetic cutoff in near earth orbit

The high flux proton component observed by AMS below the geomagnetic cutoff can be well accounted for by assuming these particles to be secondaries originating from the interaction of Cosmic Ray protons with the atmosphere. Simulation results are reporte