68 research outputs found
Heat transfer to a gas containing a cloud of particles
Heat transfer to gas containing particle clou
PRODUTOS DO INTEMPERISMO E AVALIAÇÃO DO NÍVEL DE DETERIORAÇÃO EM ROCHAS ORNAMENTAIS DA FORTALEZA DE SANTA CRUZ (NITERÓI, RJ)
DOI 10.12957/tamoios.2012.5084
RESUMO A Fortaleza de Santa Cruz, magnífico exemplo da arquitetura dos tempos da chegada dos europeus ao nosso continente, começou a ser construída por volta de 1555 na entrada da Baía de Guanabara (Niterói, RJ) com blocos de gnaisse facoidal local. De modo geral, rochas empregadas em construções em ambientes litorâneos e urbanos são expostas ao sal marinho, bem como, aos poluentes CO2, S e N e, em decorrência disso, os processos relacionados ao intemperismo podem causar danos consideráveis a essas construções. Na Fortaleza de Santa Cruz foram identificados diversos tipos de crostas (negra, de sal, orgânica, “flowstones”) e estalactites como produtos do intemperismo. A intensidade dos processos é diferente nos três pavimentos que compõem a Fortaleza, levando a níveis distintos de deterioração dos blocos de rocha, em função da circulação, teor de umidade e de sal no ar em cada pavimento.
Palavras-chaves: intemperismo; rochas ornamentais; crosta negra; dissolução.
ABSTRACT The Santa Cruz Fort, a magnificent example of architecture at the time of arrival of the Europeans to our continent, began to be constructed at about 1555 at the entrance of the Guanabara Bay (Niterói, RJ) with local blocks of augen gnaiss. In general, rocks employed in constructions in coastal and urban environments are exposed to sea derived salts and pollutants such as CO2, S and N and, as consequence of that, weathering related processes can cause considerable damage to these constructions. In the Santa Cruz Fort, various types of crusts (black, salt, organic, flowstones) and stalactites have been identified as weathering products. The intensity of such processes is different in the Fort’s three main floors and that leads to distinct deteriorations levels of the blocks of rock in each floor, a function of air circulation, humidity and salt content.
Keywords: Weathering; building stones; black crust; dissolution
Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations
We have determined the angular diameters of two metal-poor stars, HD 122563
and Gmb 1830, using CHARA and Palomar Testbed Interferometer observations. For
the giant star HD 122563, we derive an angular diameter theta_3D = 0.940 +-
0.011 milliarcseconds (mas) using limb-darkening from 3D convection simulations
and for the dwarf star Gmb 1830 (HD 103095) we obtain a 1D limb-darkened
angular diameter theta_1D = 0.679 +- 0.007 mas. Coupling the angular diameters
with photometry yields effective temperatures with precisions better than 55 K
(Teff = 4598 +- 41 K and 4818 +- 54 K --- for the giant and the dwarf star,
respectively). Including their distances results in very well-determined
luminosities and radii (L = 230 +- 6 L_sun, R = 23.9 +- 1.9 R_sun and L = 0.213
+- 0.002 L_sun, R = 0.664 +- 0.015 R_sun, respectively). We used the CESAM2k
stellar structure and evolution code in order to produce models that fit the
observational data. We found values of the mixing-length parameter alpha (which
describes 1D convection) that depend on the mass of the star. The masses were
determined from the models with precisions of <3% and with the well-measured
radii excellent constraints on the surface gravity are obtained (log g = 1.60
+- 0.04, 4.59 +- 0.02, respectively). The very small errors on both log g and
Teff provide stringent constraints for spectroscopic analyses given the
sensitivity of abundances to both of these values. The precise determination of
Teff for the two stars brings into question the photometric scales for
metal-poor stars.Comment: accepted A&A, 8 dbl-column pages, incl. 7 tables and 4 figure
Benchmark stars for Gaia: fundamental properties of the Population II star HD140283 from interferometric, spectroscopic and photometric data
We determined the fundamental properties of HD 140283 by obtaining new
interferometric and spectroscopic measurements and combining them with
photometry from the literature. The interferometric measurements were obtained
using the visible interferometer VEGA on the CHARA array and we determined a 1D
limb-darkened angular diameter of 0.353 +/- 0.013 milliarcseconds. Using
photometry from the literature we derived the bolometric flux with two
solutions: a zero-reddening one of Fbol = 3.890 +/- 0.066 1E-8 erg/s/cm2 and a
solution with a maximum of Av = 0.1 mag, Fbol= 4.220 +/- 0.067 1E-8 erg/s/cm2.
The interferometric Teff is thus 5534 +/- 103 K or 5647 +/- 105 K and its
radius is R = 2.21 +/- 0.08 Rsol. Spectroscopic measurements of HD140283 were
obtained using HARPS, NARVAL, and UVES and a 1D LTE analysis of H-alpha line
wings yields Teff(Halpha) = 5626 +/- 75 K. Using fine-tuned stellar models
including diffusion of elements we then determined the mass M and age t of
HD140283. Once the metallicity has been fixed, the age of the star depends on
M, initial helium abundance Yi and mixing-length parameter alpha, only two of
which are independent. We need to adjust alpha to much lower values than the
solar one (~2) in order to fit the observations, and if Av = 0.0 mag then 0.5 <
alpha < 1. We give an equation to estimate t from M, Yi (alpha) and Av.
Establishing a reference alpha = 1.00 and adopting Yi = 0.245 we derive a mass
and age of HD140283: M = 0.780 +/- 0.010 Msol and t = 13.7 +/- 0.7 Gyr (Av =
0.0) or M = 0.805 +/- 0.010 Msol and t = 12.2 +/- 0.6 Gyr (Av=0.1 mag). Our
stellar models yield an initial metallicity of [Z/X]i = -1.70 and logg = 3.65
+/- 0.03. Asteroseismic observations are critical for overcoming limitations in
our results.Comment: final accepted version paper (2 column format
Competitive endothelial adhesion between Plasmodium falciparum isolates under physiological flow conditions
<p>Abstract</p> <p>Background</p> <p>Sequestration of parasitized red blood cells in the microvasculature of major organs involves a sequence of events that is believed to contribute to the pathogenesis of severe falciparum malaria. <it>Plasmodium falciparum </it>infections are commonly composed of multiple subpopulations of parasites with varied adhesive properties. A key question is: do these subpopulations compete for adhesion to endothelium? This study investigated whether, in a laboratory model of cytoadherence, there is competition in binding to endothelium between pRBC infected with <it>P. falciparum </it>of variant adhesive phenotypes, particularly under flow conditions.</p> <p>Methods</p> <p>Four different <it>P. falciparum </it>isolates, of known adherence phenotypes, were matched in pairs, mixed in different proportions and allowed to bind to cultured human endothelium. Using <it>in vitro </it>competitive static and flow-based adhesion assays, that allow simultaneous testing of the adhesive properties of two different parasite lines, adherence levels of paired <it>P. falciparum </it>isolates were quantified and analysed using either non-parametric Wilcoxon's paired signed rank test or Student paired test.</p> <p>Results</p> <p>Study findings show that <it>P. falciparum </it>parasite lines show marked differences in the efficiency of adhesion to endothelium.</p> <p>Conclusion</p> <p><it>Plasmodium falciparum </it>variants will compete for adhesion to endothelia and variants can be ranked by their efficiency of binding. These findings suggest that variants from a mixed infection will not show uniform cytoadherence and so may vary in their ability to cause disease.</p
Identification of phosphorylated proteins in erythrocytes infected by the human malaria parasite Plasmodium falciparum
Rosai-Dorfman Disease Presenting as Isolated Subglottic Mass- an Extremely Rare Presentation
Comparison of the effects of chemotherapy and local irradiation on the vascularity of a transplanted mouse mammary adenocarcinoma and a pleo- morphic sarcoma.
Defeating Communist Insurgency: Experiences from Malaya and Vietnam. By SirRobert Thompson. (New York: Frederick A. Praeger, 1966. Pp. 171. $4.95.)
Processability and properties of yarns produced from cornhusk fibres and their blends with other fibres
537-542Natural
cellulose fibres extracted from cornhusks have been blended with cotton and
polyester and processed on the ring and rotor spinning machines. The
processability of crnnhusk fibres on the conventional spinning systems,
compatibility with cotton and polyester, and properties of the blended yarns
have been studied. The properties of cornhusk fibre blended yarns are also
compared with those of the similar yarns produced from unconventional fibres,
such as pineapple and banana leaves, milkweed and kenaf. It is observed that
the blending o f cornhusk fibres with cotton docs not adversely affect the
properties
of yarns while the blending of cornhusk fibres with polyester improves the
strength and elongation of the yarns
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