Scalar Synchrotron Radiation in the Schwarzschild-anti-de Sitter Geometry

We present a complete relativistic analysis for the scalar radiation emitted by a particle in circular orbit around a Schwarzschild-anti-de Sitter black hole. If the black hole is large, then the radiation is concentrated in narrow angles- high multipolar distribution- i.e., the radiation is synchrotronic. However, small black holes exhibit a totally different behavior: in the small black hole regime, the radiation is concentrated in low multipoles. There is a transition mass at $M=0.427 R$, where $R$ is the AdS radius. This behavior is new, it is not present in asymptotically flat spacetimes.Comment: 13 pages, 6 figures, published version. References adde

Tecnologia solar híbrida

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: Presentemente, a tecnologia solar converte a energia da radiação solar em energia elétrica e energia térmica, através do efeito fotovoltaico (PV) das células solares, e dos coletores térmicos de absorção da radiação para aquecimento, repectivamente. Estas formas de conversão são geralmente realizadas separadamente. Contudo, a eficiência da célula PV decresce devido ao seu natural aquecimento, quando exposta à radiação solar. Esta situação ocorre para a maioria das instalações PV, tornando-se necessário o seu arrefecimento, através de um fluido térmico, para que possa ter uma maior eficiência na geração de eletricidade e, ao mesmo tempo, aproveitar o calor extraído. Este equipamento, agora de cogeração, denomina-se de coletor solar híbrido termofotovoltaico (PVT). Neste artigo são examinados os diversos tipos de tecnologia solar, com especial relevo para a tecnologia PVT, e é apresentado um estudo teórico-experimental de um sistema PVT. As principais vantagens do uso do PVT, comparativamente ao PV e ao coletor térmico convencionais, centram-se essencialmente numa maior eficiência por unidade de área e numa diminuição da área de instalação necessária.ABSTRACT: Currently, solar technology converts solar radiation into electric and thermal energy, through the photovoltaic (PV) effect of solar cells, and thermal collectors that absorb radiation for heat generation, respectively. These types of conversion are generally accomplished separately. However, due to the natural heating of the PV cell, when exposed to solar radiation, its efficiency decreases. This situation occurs in the majority of PV setups and makes it necessary to have cooling, by the means of a thermal fluid, so that it can achieve an increased electric efficiency, and at the same time take advantage of the extracted heat. This cogeneration equipment is called a Photovoltaic-Thermal hybrid solar collector (PVT). In this paper various types of solar technologies are examined, in particular the PVT technology, and a theoretical-experimental study of a PVT system is presented. The main advantages of PVT, relative to PV and thermal collectors, is essentially a larger efficiency per unit of area and a reduction in the required installation area.info:eu-repo/semantics/publishedVersio

Dielectric characterization of the BiFe0.5Cr0.5O3 ceramics

Dielectric properties of the BiFe0.5Cr0.5O3 ceramics synthesized under high pressure were investigated in a broad frequency range (20 Hz – 1 GHz) between 200 and 500 K. It was revealed that the ceramics exhibit electrical conductivity above 300 K. Below 300 K, a dielectric dispersion caused by ferroelectric domains was observed. It was found that the conductivity follows the Almond–West law, which allowed us to determine a DC contribution (σDC). From the σDC values obtained at different temperatures, the activation energy (EA = 0.302 ± 0.006 eV) was calculated using the Arrhenius law.publishe

Magnetization And Specific Heat In U 1-xla Xga 2 And Magnetocaloric Effect In Uga 2

We have investigated the properties of the ferromagnetic series U1-x Lax Ga2. The magnetization results show a reduction of μeff and of Tc when x is increased. The electronic coefficient γ of the specific heat increases to a maximum of 260 mJUmol K2 at x=0.75. This behavior is probably consequence of delocalization of 5f electrons, causing enhancement of the density of states. For x=0.9 the ordering disappears and a non-Fermi-liquid behavior is observed. U Ga2 also presented a significant magnetocaloric effect of Δ Smag =-3.5 Jkg K at 120 K and H=7 T which can be modified by chemical pressure. © 2005 American Institute of Physics.9710Andeev, A.V., Belov, K.P., Deriagin, A.V., Levitin, R.Z., Menovsky, A., (1979) J. Phys. Colloq., 4, p. 82Da Silva, L.M., Gandra, F.G., Rojas, D.P., Cardoso, L.P., Medina, A.N., (2002) Physica B, 312-313, p. 906Tran, V.H., Kaczorowski, D., Roisnel, T., Tróc, R., Noel, H., Bouŕe, F., Andŕ, G., (1995) Physica B, 205, p. 24Gandra, F.G., Rojas, D.P., Shlyk, L., Cardoso, L.P., Medina, A.N., (2001) J. Magn. Magn. Mater., 226, p. 1312Barbara, B., (1973) J. Phys. (Paris), 34, p. 1039Sechovsky, V., Havela, L., Svoboda, P., (1986) J. Less-Common Met., 121, p. 163Segal, E., Wallace, W.E., (1975) J. Solid State Chem., 13, p. 201Radwanski, R.J., Kim-Ngan, N.H., (1995) J. Magn. Magn. Mater., 140, p. 1373Zapf, V.S., Dickey, R.P., Freeman, E.J., Sirvent, C., Maple, M.B., (2002) Phys. Rev. B, 65, p. 024437Pecharsky, V.K., Gschneider Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494Pecharsky, V.K., Gschneider Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494Plackowski, T., Junod, A., Bouquet, F., Sheikin, I., Wang, Y., Jezÿowski, A., Mattenberger, K., (2003) Phys. Rev. B, 67, p. 184406Svobodaa, P., Sechovsky, V., Menovsky, A.A., (2003) Physica B, 339, p. 177Gama, S., Coelho, A.A., De Campos, A., Carvalho, A.M.G., Gandra, F.G., Von Ranke, P.J., De Oliveira, N.A., Phys. Rev. Lett

Composition-, temperature- and pressure-induced transitions between high-pressure stabilized perovskite phases of the (1-x)BiFe0.5Sc0.5O3 - xLaFe0.5Sc0.5O3 series

Crystal structures of the high-pressure synthesized perovskite phases of the (1-x)BiFe0.5Sc0.5O3-xLaFe0.5Sc0.5O3 (0 ​= ​x ​≤ ​1) system and their temperature and pressure behaviours were studied using laboratory and synchrotron X-ray diffractions as well as neutron diffraction. At room temperature, the as-prepared phases with x ​≤ ​0.05 have an antipolar structure with the Pnma symmetry and with the √2ap ​× ​4ap ​× ​2√2ap superstructure (where ap is the pseudocubic perovskite unit-cell parameter). An incommensurately modulated phase with the Imma(00γ)s00 superspace group is observed for 0.10 ​= ​x ​≤ ​0.33, while a non-polar Pnma phase (√2ap ​× ​2ap ​× ​√2ap) is stable when x ​≥ ​0.34. The antipolar Pnma phase in the as-prepared samples with composition corresponding to x ​= ​0 transforms into the polar Ima2 one via irreversible annealing-caused transformation accompanied by a formation of a high-temperature intermediate polar R3c polymorph, while the antipolar Pnma phase in samples with x ​= ​0.05 is stable until the decomposition temperature. In the solid solutions with 0.10 ​= ​x ​≤ ​0.33, increasing temperature was found to result in a reversible transformation of the Imma(00γ)s00 phase into a non-polar Pnma one. The transition temperature decreases with increasing x. A hydrostatic pressure of few GPa was also shown to induce a reversible Imma(00γ)s00 → Pnma transformation.publishe

Goats in a comfortable and stressed environment consuming saline water: performance, digestibility, nitrogen balance, and urinary mineral concentrations

ABSTRACT The objective was to evaluate the effect of water salinity and environmental temperature on the nutrient consumption, digestibility, nitrogen balance, and mineral excretion of creole goats. Thirty-six males with an average age of 5.0±0.6 months and an average weight of 20.0±2.3kg were housed in metabolic cages. They are distributed in a completely randomized design, with a 2×3 type crossover (2 temperatures (T1 = 26±0.6ºC and T2 = 32±1.2ºC) and three levels of salinity (1.0, 6.0, and 12.0 dS m-1). The temperature influenced (P0.05) of temperatures or water salinity levels; the animals consumed and retained averages of 10.31 and 4.19 g day-1 of nitrogen in the body, respectively. The different water salinity levels influenced (P<0.05) water intake and increased the excretions of potassium and sodium in urine. Total solids levels ranging from 640 to 9,600mg L-1 in water for goats increase water consumption, as does urine potassium and sodium excretion in urine