MyoD, myogenin and proliferating cell nuclear antigen expression in growing Nile tilapia (Oreochromis niloticus L.)

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

Nebular gas drag and co-orbital system dynamics

Aims. We study trajectories of planetesimals whose orbits decay due to gas drag in a primordial solar nebula and are perturbed by the gravity of the secondary body on an eccentric orbit whose mass ratio takes values from mu(2) = 10(-7) to mu(2) = 10(-3) increasing ten times at each step. Each planetesimal ultimately suffers one of the three possible fates: (1) trapping in a mean motion resonance with the secondary body; (2) collision with the secondary body and consequent increase of its mass; or (3) diffusion after crossing the orbit of the secondary body.Methods. We take the Burlirsh-Stoer numerical algorithm in order to integrate the Newtonian equations of the planar, elliptical restricted three-body problem with the secondary body and the planetesimal orbiting the primary. It is assumed that there is no interaction among planetesimals, and also that the gas does not affect the orbit of the secondary body.Results. The results show that the optimal value of the gas drag constant k for the 1: 1 resonance is between 0.9 and 1.25, representing a meter size planetesimal for each AU of orbital radius. In this study, the conditions of the gas drag are such that in theory, L4 no longer exists in the circular case for a critical value of k that defines a limit size of the planetesimal, but for a secondary body with an eccentricity larger than 0.05 when mu(2) = 10(-6), it reappears. The decrease of the cutoff collision radius increase the difusions but does not affect the distribution of trapping. The contribution to the mass accretion of the secondary body is over 40% with a collision radius 0.05R(Hill) and less than 15% with 0.005R(Hill) for mu(2) = 10(-7). The trappings no longer occur when the drag constant k reachs 30. That means that the size limit of planetesimal trapping is 0.2 m per AU of orbital radius. In most cases, this accretion occurs for a weak gas drag and small secondary eccentricity. The diffusions represent most of the simulations showing that gas drag is an efficient process in scattering planetesimals and that the trapping of planetesimals in the 1: 1 resonance is a less probable fate. These results depend on the specific drag force chosen.

Co-orbital satellites of Saturn: congenital formation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Wakes in dilatonic current-carrying cosmic strings

In this work, we present the gravitational field generated by a cosmic string carrying a timelike current in the scalar-tensor gravities. The mechanism of formation and evolution of wakes is fully investigated in this framework. We show explicitly that the inclusion of electromagnetic properties for the string induces logarithmic divergences in the accretion problem.

Evolution of magnetic field and spin period in accreting neutron stars

Based on the accretion-induced magnetic field decay model, in which a frozen field and an incompressible fluid are assumed, we obtain the following results: (1) an analytic relation between the magnetic field and spin period, if the fastness parameter of the accretion disk is neglected (The evolutionary tracks of accreting neutron stars in the P-B diagram in our model are different from the equilibrium period lines when the influence of the fastness parameter is taken into account.); (2) the theoretical minimum spin period of an accreting neutron star is max(1.1ms (DeltaM/M(circle dot))(-1)R(6)(-5/14) I(45)(M/M(circle dot))(-1/2),1.1ms (M/M(circle dot))(-1/2) R(6)(17/14)), independent of the accretion rate (X-ray luminosity) but dependent on the total accretion mass, DeltaM; however, the minimum magnetic field depends on the accretion rate; (3) the magnetic field strength decreases faster with time than does the period.

On the HBO mechanism of X-ray neutron star

We ascribe the 15-60 Hz Quasi Periodic Oscillation (QPO) to the periastron precession frequency of the orbiting accreted matter at the boundary of magnetosphere-disk of Xray neutron star (NS). Considering the relativistic motion mechanism for the kHz QPO, that the radii of the inner disk and magnetosphere-disk of NS are correlated with each other by a factor is assumed. The obtained conclusions include: all QPO frequencies increase with increasing the accretion rate. The theoretical relations between 15-60 Hz QPO (HBO) frequency and the twin kHz QPOs are similar to the measured empirical formula. Further, the better fitted NS mass by the proposed model is about 1.9 solar masses for the detected LMXBs.

The effect of Jupiter's mass growth on satellite capture - Retrograde case

Gravitational capture can be used to explain the existence of the irregular satellites of giants planets. However, it is only the first step since the gravitational capture is temporary. Therefore, some kind of non-conservative effect is necessary to to turn the temporary capture into a permanent one. In the present work we study the effects of Jupiter mass growth for the permanent capture of retrograde satellites. An analysis of the zero velocity curves at the Lagrangian point L-1 indicates that mass accretion provides an increase of the confinement region ( delimited by the zero velocity curve, where particles cannot escape from the planet) favoring permanent captures. Adopting the restricted three-body problem, Sun-Jupiter-Particle, we performed numerical simulations backward in time considering the decrease of M-4. We considered initial conditions of the particles to be retrograde, at pericenter, in the region 100 R-4 less than or equal to a less than or equal to 400 R-4 and 0 less than or equal to e < 0.5. The results give Jupiter's mass at the moment when the particle escapes from the planet. Such values are an indication of the necessary conditions that could provide capture. An analysis of these results shows that retrograde satellites would be captured as soon as they get inside the Hills' radius and after that they keep migrating toward the planet while it is growing. For the region where the orbits of the four old retrograde satellites of Jupiter ( Ananke, Carme, Pasiphae and Sinope) are located we found that such satellites could have been permanently captured when Jupiter had between 62% and 93% of its present mass.

Hydrothermal rare earth elements mineralization in the Barra do Itapirapua carbonatite, southern Brazil: behaviour of selected trace elements and stable isotopes (C, O)

The Bura do Itapira pua carbonatite is located in southern Brazil and belongs to the Cretaceous Ponta Grossa alkaline-carbonatitic province related to the opening of the South Atlantic. The carbonatite complex is emplaced in Proterozoic granites and is mainly composed of plutonic magnesio- to ferrocarbonatite, with smaller amounts of subvolcanic magnesiocarbonatite. Hydrothermal alteration of the carbonatite has led to the formation of quartz, apatite, fluorite, rue earth fluorocarbonates, barite and sulfides in variable proportions. Trace element data, delta(13)C and delta(18)O are presented here, with the aim of better understanding the geochemical nature of hydrothermal alteration related to rare earth elements (REE) mineralization. The non-overprinted plutonic carbonatite shows the lowest REE contents, and its primitive carbon and oxygen stable isotopic composition places it in the field of primary igneous carbonatites. Two types of hydrothermally overprinted plutonic carbonatites can be distinguished based on secondary minerals and geochemical composition. Type I contains mainly quartz, rare earth fluorocarbonates and apatite as hydrothermal secondary minerals, and has steep chondrite normalized REE patterns, with Sigma(REE+Y) of up to 3 wt.% (i.e., two orders of magnitude higher than in fresh plutonic samples). In contrast, the Type II overprint contains apatite, fluorite and barite as dominant hydrothermal minerals, and is characterized by heavy REE enrichment relative to the fresh samples, with flat chondrite normalized REE patterns. Carbon and oxygen stable isotope ratios of Types I and II are elevated (delta(18)O + 8 to + 12 parts per thousand; delta(13)C - 6 to - 2 parts per thousand) relative to the fresh samples. Hydrothermally overprinted carbonatites exposed to weathering show even higher delta(18)O values (delta(18)O 13 to 25 parts per thousand) but no additional REE enrichment. The subvolcanic carbonatite has anomalously high delta(13)C of up to + 1 parts per thousand, which suggests crustal contamination through interaction with carbonate-bearing metasediments. (C) 1999 Elsevier B.V. B.V. All rights reserved.

The effect of hydrothermal alteration on the Sr and Nd isotopic signatures of the Barra do Itapirapua Carbonatite, Southern Brazil

The Cretaceous Barra do Itapirapua carbonatite in southern Brazil experienced extensive postmagmatic hydrothermal alteration. In this article, Sr and Nd isotope ratios of coexisting samples of hydrothermally overprinted and of preserved, nonoverprinted carbonatite are presented. Hydrothermal alteration caused strong REE enrichment, leading to the formation of minerals of the bastnaesite group. In the overprinted carbonatite, Nd contents reach 4000 ppm, two orders of magnitude higher than in the fresh carbonatite, but epsilon(Nd) varies only within a range of 3.4 units. In contrast, Sr was leached from the carbonatite during the postmagmatic alteration; hence values of around 10,000 ppm in the fresh carbonatite drop to about 1000 ppm in the overprinted samples. Leaching is accompanied by a variation of Sr isotopic composition toward more radiogenic values, resulting in an increase of 15 units in epsilon(Sr). Variation of Sr isotopic composition is related to postmagmatic alteration and is decoupled from the variation of Nd isotopic composition, ruling out heterogeneities in the mantle source as the main cause of isotopic variability in the data set. Furthermore, this cannot be explained by bulk crustal contamination. A two-step model is proposed in which (1) a REE-rich, carbonatite-derived hydrothermal fluid overprinted the pristine carbonatite, causing REE-enrichment with a relative small change of isotopic composition; and (2) crust-derived hydrothermal fluids percolated the cooling carbonatite, leaching the original Sr from the carbonatite and introducing a more radiogenic Sr isotopic signature. The amounts of carbonatite-derived Nd with primitive, carbonatite-like Nd isotope ratios introduced during the first stage of hydrothermal alteration are high enough to buffer the effect of crust-derived Nd on the Nd isotopic composition of the overprinted carbonatite.

The late precambrian K-alkaline magmatism in the Ribeira Fold Belt: a case study of the Piracaia Pluton, State of São Paulo, SE Brazil, and its potential mineralization (Cu, Zn, Gd)

The Pluriserial Ribeira Magmatic System-590 of the Late Precambrian Ribeira Fold Belt comprises seven groups of high-K rocks of crustal or mantle origin with ages ranging between 620 and 570 Ma. One of these groups is represented by transalkaline suites akin to appinitic lamprophyres. The suites assemble one or more of following lithologies: (+/- quartz) gabbros and monzogabbros, (+/- quartz) diorites and monzodiorites, (+/- quartz) monzonites and syenites in addition to rare granites. All these rocks occur together in the Piracaia pluton, State of São Paulo. The mineralogy of the Piracaia suite comprises variable amounts of plagioclase (An 60-10), alkali-feldspars (orthoclase, microcline, albite), ortho- (Fe-hypersthene) and clinopyroxenes (augite), amphiboles (hornblende and rare late Fe-hastingsite), abundant biotite, quartz, opaques, sphene, allanite and zircon. Several magmatic pulses constructed the pluton. The Piracaia magma bulk trend evolved initially along the silica-undersaturation plane with simultaneous fractionation of accessory, mafic and felsic minerals. These are segregated in feldspar-rich cumulates. In the late stage, the evolutionary trend followed two distinct paths: one along the or-ab thermal barrier with the crystallization of syenites; the second one along the thermal valley in the or-ab-qz subsystem, producing quartz-syenites and granites. The source of the Piracaia magma was a 'vein-plus-wall-rock-system '. Together the pulses reflect increasing and decreasing participation of peridotites and mica pyroxenites, respectively, in the magmatogenic process. The magmatic pulses were stored in magma chambers, several drained by deep faults or fractures, which were successively reactivated and recharged. Each new pulse underwent mixing with earlier residual magma, followed by fractionation. During ascent through the hot and thickened post-collisional crust, the magma pulses underwent minor compositional changes by crustal contamination. The concentration of valuable elements (Cu, Zn, Gd) in the Piracaia pluton occurred during two phases of the magmatic evolution. Cu and Zn were enriched in cumulates and Gd was concentrated in residual quartz-syenitic veins. Due to their homogeneous dark colour and texture, the monzodiorites are exploited both for polished dimension stones and supports for sensitive scientific instruments. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Relics of eclogite facies assemblages in the Ceara Central Domain, NW Borborema Province, NE Brazil: Implications for the assembly of West Gondwana

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

Tectonics and paleogeography of the Marajó Basin, northern Brazil

A área da Bacia do Marajó apresenta feições geológicas e geomorfológicas devidas principamente à distensão Mesozóica e à neotectônica pós-miocênica. O evento de distensão, com fases do Cretáceo Inferior e Superior, originou quatro sub-bacias que contituem a Bacia do Marajó, com uma espessa seqüência clástica continental mostrando influência marinha. Falhas normais NW e NNW e direcionais NE e ENE controlaram a geometria da bacia. A distensão, relacionada com a abertura do Atlântico Equatorial, propagou-se continente adentro ao longo de zonas de fraqueza crustal dos cinturões orogênicos pré-cambrianos Tumucumaque, Amapá e Araguaia. O evento neotectônico é um regime transcorrente que desenvolveu bacias transtensivas preenchidas por sedimentos marinhos rasos (Formação Pirabas) e seqüências transicionais (Grupo Barreiras) do Terciário Superior, seguidos por depósitos fluviais e seqüências transicionais do Quaternário, derivadas dos rios Amazoans e Tocantins e do estuário do Marajó. A paisagem atual tem morfologia tipicamente estuarina. A morfologia costeira apresenta escarpas em seqüências transicionais do Terciário Superior, enquanto no interior dominam elevações sustentadas por crosta laterítica do Pleistoceno Médio, aparadas por superfície erosiva a 70 m. No leste da Ilha do Marajó são reconhecidas várias gerações de paleocanais com seqüências estuarinas associadas, enquanto no lado oeste predomina uma planície flúvio-marinha.

Feições crustais determinadas pela análize azimutal da função do receptor, na região da estação sismológica de Rio Claro (RCLB)

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

Aplicação do método de Polarização Induzida em área de disposição de resíduos sólidos no município de Caçapava do Sul - RS

A geofísica é um método eficaz para investigação de áreas impactadas pelos mais diversos tipos de contaminantes, principalmente em locais de disposição de resíduos sólidos domiciliares e também utilizada na caracterização de contrastes de propriedades físicas em presença de substâncias poluentes. Este trabalho utilizou o método de Polarização Induzida numa área de disposição de resíduos sólidos desativada, localizada no município de Caçapava do Sul - RS. O aterro está assentado sobre rochas metamórficas fraturadas, pertencentes ao Complexo Metamórfico Vacacaí (Neoproterozóico). Foram realizadas 8 linhas de caminhamento elétrico, com espaçamento de 5 m entre eletrodos e 10 níveis de investigação, além de 83 medidas de direção e sentido de fraturas. O resultado geofísico permite caracterizar a camada de resíduos por baixos valores de cargabilidade. Anomalias verticais abaixo da camada de resíduos são interpretadas como zonas de fratura com possível acúmulo de chorume, caracterizadas por baixos valores de cargabilidade.

Metamorphic evolution of a subduction complex, South Shetland Islands, Antarctica

A subduction complex composed of ocean floor material mixed with arc-derived metasediments crops out in the Elephant Island group and at Smith Island, South Shetland Islands, Antarctica, with metamorphic ages of 120-80 Ma and 58-47 Ma? respectively. Seven metamorphic zones (I-VII) mapped on Elephant Island delineate a gradual increase in metamorphic grade from the pumpellyite-actinolite facies, through the crossite-epidote blueschist facies, to the lower amphibolite facies. Geothermometry in garnet-amphibole and garnet-biotite pairs yields temperatures of about 350 degrees C in zone III to about 525 degrees C in zone VII. Pressures were estimated on the basis of Si content in white mica, Al2O3 content in alkali amphibole, Na-M4/Al-IV in sodic-calcic and calcic amphibole, Al-VI/Si in calcic amphibole, and jadeite content in clinopyroxene. Mean values vary from about 6-7.5 kbar in zone II to about 5 kbar in zone VII. Results from the other islands of the Elephant Island group are comparable to those from the main island; Smith Island yielded slightly higher pressures, up to 8 kbar, with temperatures estimated between 300 and 350 degrees C. Zoned minerals and other textural indications locally enable inference of P-T-t trajectories, all with a clockwise evolution. A reconstruction in space and time of these P-T-t paths allows an estimate of the thermal structure in the upper crust during the two ductile deformation phases (D-1 & D-2) that affected the area. This thermal structure is in good agreement with the one expected for a subduction zone. The arrival and collision of thickened oceanic crust may have caused the accretion and preservation of the subduction complex. In this model, D-1 represents the subduction movements expressed by the first vector of the clockwise P-T-t path, D-2 reflects the collision corresponding to the second vector with increasing temperature and decreasing pressure, and D-3 corresponds to isostatic uplift accompanied by erosion, under circumstances of decreasing temperature and pressure.