Numerical and experimental analysis of natural convection in a cavity with flush mounted heat sources on a side wall

This work considers a problem of interest in several technological applications such as the thermal control of electronic equipment. It is also important to study the heat transfer performance of these components under off-normal conditions, such as during failure of cooling fans. The effect of natural convection on the flow and heat transfer in a cavity with two flush mounted heat sources on the left vertical wall, simulating electronic components, is studied numerically and experimentally. The influence of the power distribution, spacing between the heat sources and cavity aspect ratio have been investigated. An analysis of the average Nusselt number of the two heat sources was performed to investigate the behavior of the heat transfer coefficients. The results obtained numerically and experimentally, after an error analysis, showed a good agreement.

Heterochromatic banding pattern in two Brazilian populations of Aedes aegypti

We analysed samples of Aedes aegypti from Sao Jose do Rio Preto and Franca (Brazil) by C-banding and Ag-banding staining techniques. C-banding pattern of Ae. aegypti from Sao Jose do Rio Preto examined in metaphase cells differed from Franca. The chromosomes 2, 3 and X showed centromeric C-bands in both populations, but a slightly stained centromeric band in the Y chromosome was observed only in Sao Jose do Rio Preto. In addition, the X chromosome in both populations and the Y chromosome of all individuals from Sao Jose do Rio Preto showed an intercalary band on one of the arms that was absent in Franca. An intercalary, new band, lying on the secondary constriction of chromosome 3 was also present in mosquitoes of both populations. The comparison of the present data with data in the literature for Ae. aegypti from other regions of the world showed that they differ as to the banding pattern of sex chromosomes and the now described intercalary band in chromosome 3. The observations suggested that the heterochromatic regions of all chromosomes are associated to constitute a single C-banded body in interphase cells. Ag-banding technique stained the centromeric regions of all chromosomes (including the Y) and the intercalary C-band region of the X chromosome in both populations. As Ae. aegypti populations are widespread in a great part of the world, the banding pattern variations indicate environmental interactions and may reveal both the chromosome evolutionary patterns in this species and the variations that may interfere with its vector activity.

Relativistic quantum thermodynamics of ideal gases in two dimensions

In this work we study the behavior of relativistic ideal Bose and Fermi gases in two space dimensions. Making use of polylogarithm functions we derive a closed and unified expression for their densities. It is shown that both type of gases are essentially inequivalent, and only in the non-relativistic limit the spinless and equal mass Bose and Fermi gases are equivalent as known in the literature.

Differentiation of floral color and odor in two fly pollinated species of Metrodorea (Rutaceae) from Brazil

We investigated if differences in morphological characters in two species of Metrodorea (Rutaceae) from Brazilian semideciduous forests correspond to some pollination divergence. M. nigra and M. stipularis are sympatric species, display a similar floral morphology, are protandrous, self-incompatible, their flower periods overlap, and both are pollinated by flies. M. nigra main pollinators are Pseudoptiloleps nigripoda (Muscidae) and Fannia sp. (Fanniidae); M. stipularis major pollinators are Phaenicia eximia (Calliphoridae), Palpada sp. and Ornidia obesa (Syrphidae). The distinct floral odor (disagreeable in M. nigra and sweet in M. stipularis) and color (brownish violet vs. pale yellow) determine the differences on type and number of floral visitors observed. Several species from semideciduous forests initially considered to be pollinated by diverse insects, present flies as main pollinators, stressing the importance of fly pollination in such habitats.

Numerical study of the spherically symmetric Gross-Pitaevskii equation in two space dimensions

The Gross-Pitaevskii equation for Bose-Einstein condensation (BEC) in two space dimensions under the action of a harmonic oscillator trap potential for bosonic atoms with attractive and repulsive interparticle interactions was numerically studied by using time-dependent and time-independent approaches. In both cases, numerical difficulty appeared for large nonlinearity. Nonetheless, the solution of the time-dependent approach exhibited intrinsic oscillation with time iteration which is independent of space and time steps used in discretization.

Variational studies and replica symmetry breaking in the generalization problem of the binary perceptron

We analyze the average performance of a general class of learning algorithms for the nondeterministic polynomial time complete problem of rule extraction by a binary perceptron. The examples are generated by a rule implemented by a teacher network of similar architecture. A variational approach is used in trying to identify the potential energy that leads to the largest generalization in the thermodynamic limit. We restrict our search to algorithms that always satisfy the binary constraints. A replica symmetric ansatz leads to a learning algorithm which presents a phase transition in violation of an information theoretical bound. Stability analysis shows that this is due to a failure of the replica symmetric ansatz and the first step of replica symmetry breaking (RSB) is studied. The variational method does not determine a unique potential but it allows construction of a class with a unique minimum within each first order valley. Members of this class improve on the performance of Gibbs algorithm but fail to reach the Bayesian limit in the low generalization phase. They even fail to reach the performance of the best binary, an optimal clipping of the barycenter of version space. We find a trade-off between a good low performance and early onset of perfect generalization. Although the RSB may be locally stable we discuss the possibility that it fails to be the correct saddle point globally. ©2000 The American Physical Society.

Experimental Salmonella enterica serovar Pullorum infection in two commercial varieties of laying hens

An experiment was carried out to investigate the biology of Salmonella Pullorum in two varieties of laying hens, from 5 days of age up to 9 months. One variety was resistant to systemic salmonellosis (light layers producing white eggs) and the other was considered susceptible (brown layers producing brown eggs). The brown birds were more affected by the infection, showing signs of clinical disease in the first month of life. Later, these signs disappeared, but postmortem examination revealed persistent gross pathological changes in the liver, spleen, heart and ovary. The rapid agglutination test detected reactors throughout the experiment, with the strongest agglutination from 1 to 7 months post-infection. S. Pullorum was isolated from some of the organs and the eggs laid throughout the experiment. The relationship between white birds and S. Pullorum was less intense, and there were no noticeable signs of disease. There were few gross pathological changes, and the bacteria were isolated infrequently and only for a brief period after infection, although contaminated eggs were laid by these birds. The strongest serological response in the white chickens occurred between the second and the fifth month post-infection.

Application of C-banding in two Arachis wild species, Arachis Pintoi Krapov. and W.C. Gregory and A. villosulicarpa Hoehne to mitotic chromosome analyses

Two wild diploid (2n = 20 chromosomes) and self-pollinating Arachis species, Arachis Pintoi Krapov and W.C. Gregory and A. villosulicarpa Hoehne were submmited to C-band technique to karyotype analyses. Root tips were employed in the analyses. Morphometric data chose that chromosome lengths varied from 3.12 in A. villosulicarpa to 1.45 in A. Pintoi. Karyotype formula obtained was 10sm to A. Pintoi and 9sm + 1m to A. villosulicarpa. There was a predominance of pericentromeric C-band in all mitotic metaphasic chromosomes in both species. Besides C-band values, both species still did not differ in respect to chromosome absolute and relative lengths, centromeric index, symmetry index and total karyotype haploid length. C-band and morphometric data did not show strong or significant differences which could separate these two species of peanut which belong to evolutive different sections.

Content of essential oil of fennel seeds in two different stages of development

This experiment was carried out at Plant Production Sector, Agronomical Science College-Botucatu, S.P., Brazil, in March, 2000. The aim of this assay was to determine the yield of essential oil of fennel (Foeniculum vulgare Miller) in different stages of development. Essential oils were prepared by hydrodistillation from the seeds using of Clevenger apparatus. The water utilized for the extraction of essential oil was sufficient to cover 100 g of seeds and the mixture was distilled for three hours. The volume of essential oil in the graduated side -arm of Clevenger apparatus was observed. There were no significative difference statistic was observed (Tukey 5%) in percentage (v/m) of oil content, based on dry weight of green seeds compared with dry weight of mature seeds, when they were harvested in two different stages of development. There was significative difference statistic between data obtained of humidity content of green seeds when these were compared with mature seeds. These results shows that others specifics studies about adaptation of fennel in tropical conditions are necessary, because the obtained data were different of data described on literature.

Spectroscopic characteristics of Er3+ in the two crystallographic sites of Gd2SiO5

Gd2SiO5 is among the interesting and suitable hosts for Er3+ which find extensive applications in the infrared, visible and ultraviolet spectral regions. In order to investigate its potentialities, a prior study of the spectroscopic behaviour of Er3+ substituting for Gd3+ ions in the two crystallographic sites of the host was performed. Absorption, excitation, site-selective emission and time-resolved spectroscopies were employed in the visible spectral region to study transitions between excited 4S3/2 and ground 4I15/2 states. These levels multiplets were attributed to each site separately, and their corresponding 4S3/2 lifetimes (1.8 ± 0.1 μs for site 1 and 3.2 ± 0.1 μs for site 2) were determined.