Showing papers by "State University of Campinas published in 1983"

Path integral approach to quantum Brownian motion

Abstract: We apply the influence-functional method of Feynman and Vernon to the study of Brownian motion at arbitrary temperature. By choosing a specific model for the dissipative interaction of the system of interest with its environment, we are able to evaluate the influence functional in closed form and express it in terms of a few parameters such as the phenomenological viscosity coefficient. We show that in the limit h→0 the results obtained from the influence functional formalism reduce to the classical Fokker-Planck equation. In the case of a simple harmonic oscillator with arbitrarily strong damping and at arbitrary temperature, we obtain an explicit expression for the time evolution of the complete density matrix ϱ(x, x′, t) when the system starts in a particular kind of pure state. We compare our results with those of other approaches to the problem of dissipation in quantum mechanics.

Reliable Bad Data Processing for Real-Time State Estimation

Abstract: The weighted least squares performance index test (J(x?) test) conventionally used in power system static state estimation has poor reliability for detecting the presence of measurement errors in the range 3 to 20 standard deviations. This paper describes a very simple alternative method, with considerably improved bad data detection properties, based on evaluating the coherency between the measurement with the largest normalized residual and the remainder of the measurement system. In fact, the detection and identification phases of bad data processing become combined. Inanexistent state estimator using normalized residuals, the cost of implementation of the new method is negligible. The new method has been tested extensively on several power systems, and compared with the J(x?) test.

Scale-eating in characoids and other fishes

Abstract: Scale-eating is known for several unrelated fish groups, but few data are available on the habits of most species. General habits and feeding behavior of some lepidophagous characoids are presented and compared to other scale-eating species. The diversity of morphology, habits, and behavior of scale-eating fishes is great, and few patterns are shared by the specialized scale-eaters. Except for modified teeth, no morphological characteristic permits identifying a fish as a specialized lepidophage. Hunting tactics consist mainly of ambush, stalking, or disguise (aggressive mimicry). Scale-removal may be accomplished by a jarring strike with the snout, generally directed at the prey’s flank, or by biting or rasping. The mode of scale-removal seems to reflect primarily the disposition of the jaws and the teeth. Scales are swallowed directly if taken in the mouth; if not, they are gathered as they sink, or picked up from the bottom. Scale-eating is probably a size-limited habit. Specialized scale-eaters rarely exceed 200 mm, most ranging near 120 mm. Some species eat scales only when young; most take other food items in addition to scales. Scale-eating habits probably arose from trophic or social behaviors. These are not mutually exclusive and, indeed, may have acted together during the evolution of lepidophagy. Suggested trophic origins include scraping epilithic algae, modified piscivory, and necrophagy. Social origins include intra- and interspecific aggressive behavior during feeding.

Effect of sugars, lipids and type of starch on the mode and kinetics of retrogradation of concentrated corn starch gels

Abstract: The retrogradation of concentrated gels of three types of corn starch (Normal, Amylose Extender and Waxy) and the influence of certain sugars and lipids on the mode and kinetics of retrogradation were investigated. The lipids tested were triglycerides, hydrogenated babassu oil and hydrogenated vegetable oil. The results based on the Avrami theory indicated that the mechanism of crystallization is instantaneous nucleation followed by a rod-like growth of crystals, regardless of the type of starch, sugar or lipid used. In general, sugars increased the retrogradation rate while lipids retarded it. The dissacharides were more effective in increasing the velocity of retrogradation than glucose. The results suggested that a relationship exists between the velocity of retrogradation and the number of hydroxyl groups and/or size of the molecule. Among the lipids, the most effective in retarding retrogradation was that with the shortest fatty acid chain. Die Wirkung von Zuckern, Lipiden und bestimmten Starkearten auf den Verlauf und die Kinetik der Retrogradation konzentrierter Maisstarkegele. Die Retrogradation konzentrierter Gele von drei Maisstarkearten (normal, amylosereich und wachsig) und der Einflus bestimmter Zucker und Lipide auf den Verlauf und die Kinetik der Retrogradation wurden untersucht. Als Lipide wurden Triglyceride, hydriertes Babassuol und hydriertes Pflanzenol herangezogen. Die auf der Avrami-Theorie basierenden Ergebnisse zeigten, das der Kristallisationsmechanismus aus einer augenblicklichen Keimbildung besteht, gefolgt von einem stabchenformigen Wachstum der Kristalle, unabhangig von verwendeter Starkeart, Zucker oder Lipid. Im allgemeinen erhohten Zucker die Retrogradationsgeschwindigkeit, wahrend Lipide die Retrogradation verzogerten. Disaccharide erhohten die Retrogradationsgeschwindigkeit starker als Glucose. Die Ergebnisse deuten darauf hin, das zwischen der Retrogradationsgeschwindigkeit und der Anzahl der Hydroxylgruppen und/oder der Molekulgrose eine Beziehung besteht. Unter den Lipiden verzogerten diejenigen mit der kurzesten Fettsaurekette die Retrogradation am starksten.

Graded barrier single quantum well lasers - Theory and experiment

Abstract: Optical gain characteristics of quantum well heterostructure lasers are investigated in a broad range from a weakly quantized system to a strongly quantized one utilizing the band-to-band model with k selection rule, the detailed band structure of the quantum well heterostructures, and degenerate statistics. The results are compared to the experimentally observed threshold current densities in graded barrier single quantum well lasers. It is found that the threshold current densities of these quantum well lasers are well explained by the theoretical results in the range of well width from 75 to 300 A. The lowest threshold current density observed is 245 A/cm2in a heavily doped 100 A single quantum well laser with a 150μm stripe width and 550μm length.

Analysis of microstrip wraparound antennas using dyadic Green's functions

Abstract: The radiation pattern of microstrip wraparound antennas was obtained here using a theory based on dyadic Green's functions for concentric-cylindrical layered media. The dielectric layer that is usually neglected as a first-order approximation was considered here. An asymptotic expression for the dyadic Green's function that takes into account only the space wave is first obtained. Radiation patterns for various radii, permittivities, and thicknesses of the dielectric layer of a microstrip wraparound antenna were obtained using as a source a uniform annular magnetic current obtained by means of a cavity model with conducting magnetic walls. The calculated values of the percent pattern coverage decreases as the thickness and the permittivity of the dielectric layer increase. The influence of the dielectric layer is more pronounced for radiation direction near that of the axis of the cylindrical surface. It is also shown that the radiation patterns at a frequency of 2.0 GHz are not much dependent on the diameter of the antenna for values from 3 to 120 in.

Optimization of radio communication in media with three layers

Abstract: The electromagnetic radiation of an electric dipole in a medium with three layers is examined using dyadic Green's functions. The far zone field for problems of this nature is primarily determined from the lateral wave. It is shown that the excitation of this wave may be reinforced through a dipole inclination and an optimum position may be determined. The radio losses for typical forests were calculated for vertical and horizontal dipoles and for dipoles with an optimum inclination. The theoretical results are in good agreement with the available experimental data.

Cold Vapor Atomic Absorption determination of mercury by Flow Injection Analysis using a Teflon membrane phase separator coupled to the absorption cell

Abstract: A Flow Injection Analysis (FIA) procedure for the determination of trace amounts of mercury by the Cold Vapor Atomic Absorption (CVAA) method is presented. In order to make efficient use of the FIA technique, a new flow cell was developed to permit a rapid separation of elemental mercury from the carrier solution. The design of this device is based on the permeability of Hg 0 in commercially available Teflon (PTFE) tape, which acts as a membrane phase separator. The calibration curve is linear up to 70 ng.ml −1 ( A = 0.005 + 0.008 Hg(ng.ml −1 ); r = 0.9996) using a 15-cm open cell approach, with a detection limit of 1.4 ng. ml −1 (0.66 ng of mercury), considering a signal to noise ratio of three. The standard deviation is s = ±0.004 absorbance units, calculated at a level of 50 ng.ml −1 of Hg 2+ . The sampling rate was 110 samples per h.

Trapping of soursop (Annona muricata) juice volatiles on porapak Q by suction

Abstract: The trapping technique of Singleton and Pattee, in which the volatiles are swept to a Porapak Q trap by suction rather than by a sweeping gas, was modified and used to isolate soursop juice volatiles. Using fixed, low vacuum and operating conditions determined specifically for soursop volatiles, very high reproducibility was obtained. The majority of the peaks had a coefficient of variation less than 0.10. The relative amounts of the volatile components obtained by direct headspace sampling was fairly well maintained in the Porapak Q concentrate. The chromatograms showed distinct differences between two commercial brands or between lots of the same brand of soursop juice. The trapping technique appear to have wide applicability provided that the operating conditions are adapted to each product studied.

Aspectos de comportamento alimentar e dieta da tartaruga marinha, Chelonia mydas no litoral norte paulista

Abstract: Feeding behavior of immature green turtles, Chelonia mydas, has been observed on rocky shores along the northern part of State of Sao Paulo, southeastern Brazil. This turtle forages on underwater ledges, at depths of 1 to 3 m and grazes on benthic algae. The turtle seems to visually scan the algae during feeding and moves slowly, walking from one patch of vegetation to another. Gut contents of four individuals (331-452 mmCCL) consisted mainly of red and brown algae. Comparisons between gut contents and algae growing at the grazing sites, together with scanning behavior suggest selective feeding. Syntopic large herbivorous fishes of the genera Kyphosus, Sparisma, and Acanthurus showed little feeding overlap with the green turtle.

Cytochemical properties of euchromatin and heterochromatin.

Abstract: Two classic cytochemical tests, the Feulgen-Schiff reaction and Toluidine Blue basophilia, have been employed for investigating the differential characteristics of heterochromatin and euchromatin. Differences have been detected in the Feulgen hydrolysis kinetics, the Feulgen absorption spectrum, the image analysis of Feulgen-stained material, and the binding of Toluidine Blue under ordinary and Mg2+ competitive staining conditions. The differences are assumed to be a function of the composition and stereo-arrangement of the DNA and DNA-protein complexes present in these chromatin types and are possibly associated with physiological activities whose whole meaning is far from being clear. Differences in optical retardations in Toluidine Blue-stained material were also found. These are interpreted as being due to chromatin packing state and selective removal of histones promoted by the acetic acid-ethanol fixative.

Accurate method for characterising single-mode fibres: theory and experiment

Abstract: We present a direct method for determining the modal field from the far-field pattern of single-mode fibres having arbitrary index profiles. Analysis of experimental data shows that the method is relatively simple compared to other methods and gives accurate results.

Raman study of anharmonic effects in α -LiI O 3

Abstract: We present a detailed study of the Raman spectrum of $\ensuremath{\alpha}$-LiI${\mathrm{O}}_{3}$ as a function of temperature and pressure. Measurements under hydrostatic pressure were performed at 300 and 380 K. Comparison of these results among each other and with previous results from uniaxial stress measurements performed at 77 K reveal that mode Gr\"uneisen parameters, ${\ensuremath{\gamma}}_{j}$, are essentially temperature independent. These parameters are strongly dependent on mode frequency, ${\ensuremath{\omega}}_{j}$, obeying an approximate scaling law, ${\ensuremath{\gamma}}_{j}\ensuremath{\propto}{\ensuremath{\omega}}_{j}^{\ensuremath{-}2}$---a behavior characteristic of that observed in molecular crystals. Data from the pressure and temperature dependence of ${\ensuremath{\omega}}_{j}$ are combined to separate the intrinsic (thermal expansion) from the extrinsic contributions to the latter. This procedure reveals the existence of anomalous anharmonic behavior affecting only the lattice mode which involves translations of ${\mathrm{Li}}^{+}$ ions along the $c$ axis. We suggest that this is indicative of the existence of a link between this mode and the anomalous increase in the ionic conductivity along the $c$ axis occurring in this material at high temperatures.

Uma nova espécie de Thoropa da Serra do Cipó, Minas Gerais, Brasil (Amphibia, Leptodactylidae)

Abstract: Thoropa megatympanum, sp. n., is described from the Serra do Cipo, Minas Gerais, Southeastern Brasil. The new species is related to T. miliaris (Spix), from which it is readily distinguished by its smaller size, broader head, larger tympanum, shorter legs, and dorsal pattern mottled. The eggs and the tadpole are also described.