Thermal behaviour of succinic acid, sodium succinate and its compounds with some bivalent transition metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Microscopic studies on the transition between the sigmoid sinus, the superior bulb of the jugular vein and the first portion of the internal jugular vein

The author studied the structure of the tissue components of the tunicae of the terminal segment of the sigmoid sinus, particularly at the level of the transition between the sigmoid sinus, the superior bulb of the jugular vein and the first portion of the human internal jugular vein; it was established that the transition between the sigmoid sinus and the first portion of the internal jugular vein occupies the whole extension of the superior bulb of the jugular vein up to the inferior third of the first portion of this vessel. These vascular walls exhibit a structure similar to that of the dura, i.e. the tunica adventitia is formed by fascicles of collagenic fibers which describe discontinuous spirals, more open proximal to the beginning of the first portion of the internal jugular vein. Approximately in the inferior third of the first portion of the internal jugular vein, there appear fascicles of smooth muscle fibers which are arranged similarly to those of the venous walls. The tunica intima of these vascular segments exhibits an endothelium resting on a network of elastic fibers which may play the role of an internal elastic lamina. From the bony border of the jugular foramen there originates a connective system whose fascicles of collagenic and elastic fibers incorporate to the wall of the internal jugular vein after describing a stretch in spiral around the vascular lumen.

Deviation from the sech2 superradiant emission law in a two-level atomic system

The atomic superradiant emission is treated in the single-particle mean-field approximation. A single-particle Hamiltonian, which represents a dressed two-level atom in a radiation field, can be obtained and it is verified that it describes the transient regime of the emission process. While the line-shape emission for a bare atom follows the sech2 law, for the dressed atom the line shape deviates appreciably from this law and it is verified that the deviation depends crucially on the ratio of the dynamic frequency shift to the transition frequency. This kind of deviation is observed in experimental results. © 1990 The American Physical Society.

Liquid-gas phase transition in Bose-Einstein condensates with time evolution

We study the effects of a repulsive three-body interaction on a system of trapped ultracold atoms in a Bose-Einstein condensed state. The stationary solutions of the corresponding s-wave nonlinear Schrödinger equation suggest a scenario of first-order liquid-gas phase transition in the condensed state up to a critical strength of the effective three-body force. The time evolution of the condensate with feeding process and three-body recombination losses has a different characteristic pattern. Also, the decay time of the dense (liquid) phase is longer than expected due to strong oscillations of the mean-squared radius.

Evolution of the viscoelastic properties of SnO2 colloidal suspensions during the sol-gel transition

This paper describes the effect of the concentration of electrolyte and pH on the kinetics of aggregation and gelation processes of SnO2 colloidal suspensions. Creep, creep-recovery, and oscillatory rheological experiments have been done in situ during aggregation and gelation. A phenomenological description of the structure of the colloidal system is given from the time evolution of rheological parameters. The dependence of the equilibrium steady-state shear compliance on the terminal region of clusters or aggregates seems to be a way to determine the beginning of interconnection of aggregates and the gel point. We propose that at this point the equilibrium steady-state compliance is a minimum. The steady-state viscosity determined from creep experiment can be fit with a power law with the extent of the transformation, giving critical exponent s = 0.7 ± 0.1. The value of the critical exponent Δ = 0.78 ± 0.05 was determined from oscillatory experiment. These results indicate that gelation of SnO2 colloidal suspension exhibits the typical scale expected from the scalar percolation theory. © 2000 Elsevier Science B.V. All rights reserved.

A theoretical study of the A2 ∑+-X2∏ system of the SiP molecule

The A2∑+ and Z2∏ electronic states of the SiP species have been investigated theoretically at a very high level of correlation treatment (CASSCF/MRSDCI). Very accurate potential energy curves are presented for both states, as well as the associated spectroscopic constants as derived from the vib-rotational energy levels determined by means of the numerical solution of the radial Schrödinger equation. Electronic transition moment function, oscillator strengths, Einstein coefficients for spontaneous emission, and Franck-Condon factors for the A2∑+-X2∏ system have been calculated. Dipole moment functions and radiative lifetimes for both states have also been determined. Spin-orbit coupling constants are also reported. The radiative lifetimes for the A2∑+ state, taking into account the spin-orbit diagonal correction to the X2∏ state, decrease from a value of 138 ms at v′ = 0 to 0.48 ms at v′ = 8, and, for the X2∏ state, from 2.32 s at v″ = 1 to 0.59 s at v″ = 5. Vibrational and rotational transitions are expected to be relatively strong.

Raman scattering study of the PbZr1-xTixO3 system: Rhombohedral-monoclinic-tetragonal phase transitions

In this paper we present a Raman-scattering study of the phase transitions in the PbZr1-xTixO3 systems around the morphotropic phase boundary over a wide temperature range. The boundary between rhombohedral and monoclinic phases was found to be a quasivertical line between x = 0.46 and x = 0.47. We also studied the monoclinic-tetragonal phase boundary and our spectroscopic results agree very well with those reported by using x-ray diffraction.

Quantitative structural analysis of the transition from LT-Li xCoO2 to HT-LixCoO2 using the rietveld method: Correlation between structure and electrochemical performance

A quantitative phase analysis was made of LixCoO2 powders obtained by two distinct chemical methodologies at different temperatures (from 400 to 700°C). A phase analysis was made using Rietveld refinements based on X-ray diffraction data, considering the Li xCoO2 powders as a multiphase system that simultaneously contained two main phases with distinct, layered and spinel-type structures. The results showed the coexistence of both structures in LixCoO 2 obtained at low temperature (400 and 500°C), although only the layered structure was detected at higher temperatures (600 and 700°C), regardless of the chemical powder process employed. The electrochemical performance, evaluated mainly by the cycling reversibility of Li xCoO2 in the form of cathode insertion electrodes, revealed that there is a close correlation between structural features and the electrochemical response, with one of the redox processes (3.3 v/3.9 v) associated only with the presence of the spinel-type structure. © 2003 Elsevier B.V. All rights reserved.

Longitudinal distribution of Copepoda populations in the transition zone of Paranapanema River and Jurumirim Reservoir (São Paulo, Brazil) and interchange with two lateral lakes.

Longitudinal changes in composition, abundance, and distribution of copepods were studied at the transition zone of Paranapanema River-Jurumirim Reservoir (SP, Brazil). The interchange of biotic material between marginal lakes and the river system was also examined. Water samples were obtained from 6 stations along a stretch of 13 km of the Paranapanema River, from an upstream reach with high water velocity up to the river mouth into Jurumirim Reservoir. Two other sites in lateral lakes were also sampled. Nine copepod taxa were identified: 3 calanoids (Argyrodiaptomus furcatus Sars, Notodiaptomus iheringi Wright, and N. conifer Sars) and 6 cyclopoids (Eucyclops Claus, Microcyclops Claus, Mesocyclops longisetus Thiébaud, Thermocyclops decipiens Fischer, T. minutus Lowndes, and Paracyclops Claus). Harpacticoids were also collected. Calanoid and cyclopoid nauplii and copepodids, and harpacticoids were the most abundant organisms. In general, there was a longitudinal decrease in copepod abundance, whereas an increase was detected near the lakes. The abundance of most copepods was inversely correlated with current velocity and suspended solids. Higher abundance was observed in the river main course during the rainy season, during which there is a higher connectivity between the lakes and the main river. This promotes exportation of biologic material from marginal lakes to the river system, a biotic exchange reflecting the importance of marginal lakes to the river community structure.

Automatic code generation for microcontrollers from place-transition Petri net models

This paper describes a program for the automatic generation of code for Intel's 8051 microcontroller. The code is generated from a place-transition Petri net specification. Our goal is to minimize programming time. The code generated by our program has been observed to exactly match the net model. It has also been observed that no change is needed to be made to the generated code for its compilation to the target architecture. © 2011 IFAC.

Tetragonal to monoclinic phase transition observed during Zr anodisation

Plasma electrolytic oxidation (PEO) is a coating procedure that utilises anodic oxidation in aqueous electrolytes above the dielectric breakdown voltage to produce oxide coatings that have specific properties. These conditions facilitate oxide formation under localised high temperatures and pressures that originate from short-lived microdischarges at sites over the metal surface and have fast oxide volume expansion. Anodic ZrO2 films were prepared by subjecting metallic zirconium to PEO in acid solutions (H2C 2O4 and H3PO4) using a galvanostatic DC regime. The ZrO2 microstructure was investigated in films that were prepared at different charge densities. During the anodic breakdown, an important change in the amplitude of the voltage oscillations at a specific charge density was observed (i.e., the transition charge density (Q T)). We verified that this transition charge is a monotonic function of both the current density and temperature applied during the anodisation, which indicated that Q T is an intrinsic response of this system. The oxide morphology and microstructure were characterised using SEM and X-ray diffraction experiments (XRD) techniques. X-ray diffraction analysis revealed that the change in voltage oscillation was correlated with oxide microstructure changes during the breakdown process. © 2012 Springer-Verlag Berlin Heidelberg.

Sudden change of quantum discord for a system of two qubits

It is known that quantum discord might experience a sudden transition in its dynamics when calculated for certain Bell-diagonal states (BDS) that are in interaction with their surroundings. We examine this phenomenon, known as the sudden change of quantum discord, considering the case of two qubits independently interacting with dephasing reservoirs. We first demonstrate that, for a class of initial states which can be chosen arbitrarily close to BDS, the transition is in fact not sudden, although it might numerically appear so if not studied carefully. Then, we provide an extension of this discussion covering the X-shaped density matrices. Our findings suggest that the transition of quantum discord might be sudden only for an highly idealized zero-measure subset of states within the set of all possible initial conditions of two qubits. © 2013 American Physical Society.

Thermal and structural study of glasses in the binary system TeO2-Pb(PO3)(2)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Defining a fish bio-assessment tool to monitoring the biological condition of a cascade reservoirs system in tropical area

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)