Thermochronology of central Ribeira Fold Belt, SE Brazil: Petrological and geochronological evidence for long-term high temperature maintenance during Western Gondwana amalgamation

The studied sector of the central Ribeira Fold Belt (SE Brazil) comprises metatexites, diatexites, charnockites and blastomylonites. This study integrates petrological and thermochronological data in order to constrain the thermotectonic and geodynamic evolution of this Neoproterozoic-Ordovician mobile belt during Western Gondwana amalgamation. New data indicate that after an earlier collision stage at similar to 610 Ma (zircon, U-Pb age), peak metamorphism and lower crust partial melting, coeval with the main regional high grade D(1) thrust deformation, occurred at 572-562 Ma (zircon, U-Pb ages). The overall average cooling rate was low (<5 degrees C/Ma) from 750 to 250 degrees C (at similar to 455 Ma; biotite-WR Rb-Sr age), but disparate cooling paths indicate differential uplift between distinct lithotypes: (a) metatexites and blastomylonites show a overall stable 3-5 degrees C/Ma cooling rate; (b) charnockites and associated rocks remained at T>650 degrees C during sub-horizontal D(2) shearing until similar to 510-470 Ma (garnet-WR Sm-Nd ages) (1-2 degrees C/Ma), being then rapidly exhumed/cooled (8-30 degrees C/Ma) during post-orogenic D(3) deformation with late granite emplacement at similar to 490 Ma (zircon, U-Pb age). Cooling rates based on garnet-biotite Fe-Mg diffusion are broadly consistent with the geochronological cooling rates: (a) metatexites were cooled faster at high temperatures (6 degrees C/Ma) and slowly at low temperatures (0.1 degrees C/Ma), decreasing cooling rates with time; (b) charnockites show low cooling rates (2 degrees C/Ma) near metamorphic peak conditions and high cooling rates (120 degrees C/Ma) at lower temperatures, increasing cooling rates during retrogression. The charnockite thermal evolution and the extensive production of granitoid melts in the area imply that high geothermal gradients were sustained fora long period of time (50-90 Ma). This thermal anomaly most likely reflects upwelling of asthenospheric mantle and magma underplating coupled with long-term generation of high HPE (heat producing elements) granitoids. These factors must have sustained elevated crustal geotherms for similar to 100 Ma, promoting widespread charnockite generation at middle to lower crustal levels. (C) 2010 Elsevier B.V. All rights reserved.

Metamorphic P-T evolution of granulites in the central Ribeira Fold Belt, SE Brazil

Pseudosections, geothermobarometric estimates and careful petrographic observations of gneissic migmatites and granulites from Neoproterozoic central Ribeira Fold Belt (SE Brazil) were performed in order to quantify the metamorphic P-T conditions during prograde and retrograde evolution of the Brasiliano Orogeny. Results establish a prograde metamorphic trajectory from amphibolite facies conditions to metamorphic peak (T = 850 +/- 50 A degrees C; P = 8 +/- 1 kbar) that promoted widespread dehydrationmelting of 30 to 40% of the gneisses and high-grade granitization. After the metamorphic peak, migmatites evolved with cooling and decompression to T a parts per thousand 500 A degrees C and P a parts per thousand 5 kbar coupled with aH2O increase, replacing the high-grade paragenesis plagioclase-quartz-K-feldspar-garnet by quartz-biotite-sillimanite-(muscovite). Cordierite absence, microtextural observations and P-T results constrain the migmatite metamorphic evolution in the pseudosections as a clockwise P-T path with retrograde cooling and decompression. High-temperature conditions further dehydrated the lower crust with biotite and amphibole-dehydration melting and granulite formation coupled with 10% melt generation. Granulites can thus be envisaged as middle to lower crust dehydrated restites. Granulites were slowly (nearly isobarically) cooled, followed by late exhumation/retrograde rapid decompression and cooling, reflecting a two step P-T path. This retrograde evolution, coupled with water influx, chemically reequilibrated the rocks from granulite to amphibolite/greenschist facies, promoting the replacement of the plagioclase-quartz-garnet-hypersthene peak assemblage by quartz-biotite- K-feldspar symplectites.

P-T-Fluid evolution and graphite deposition during retrograde metamorphism in Ribeira Fold Belt, SE Brazil: Oxygen fugacity, fluid inclusions and C-O-H isotopic evidence

Combined fluid inclusion (FI) microthermometry, Raman spectroscopy, X-ray diffraction, C-O-H isotopes and oxygen fugacities of granulites from central Ribeira Fold Belt, SE Brazil, provided the following results: i) Magnetite-Hematite fO(2) estimates range from 10(-11.5) bar (QFM + 1) to 10(-18.3) bar (QFM - 1) for the temperature range of 896 degrees C-656 degrees C, implying fO(2) decrease from metamorphic peak temperatures to retrograde conditions; ii) 5 main types of fluid inclusions were observed: a) CO(2) and CO(2)-N(2) (0-11 mol%) high to medium density (1.01-0.59 g/cm(3)) FI; b) CO(2) and CO(2)-N(2) (0-36 mol%) low density (0.19-0.29 g/cm(3)) FI; c) CO(2) (94-95 mol%)-N(2) (3 mol%)-CH(4) (2-3 mol%)-H(2)O (water phi(v) (25 degrees C) = 0.1) FI; d) low-salinity H(2)O-CO(2) FI; and e) late low-salinity H(2)O FI; iii) Raman analyses evidence two graphite types in khondalites: an early highly ordered graphite (T similar to 450 degrees C) overgrown by a disordered kind (T similar to 330 degrees C); iv) delta(18)O quartz results of 10.3-10.7 parts per thousand, imply high-temperature CO(2) delta(18)O values of 14.4-14.8 parts per thousand, suggesting the involvement of a metamorphic fluid, whereas lower temperature biotite delta(18)O and delta D results of 7.5-8.5 parts per thousand and -54 to -67 parts per thousand respectively imply H(2)O delta(18)O values of 10-11 parts per thousand and delta D(H2O) of -23 to -36 parts per thousand suggesting delta(18)O depletion and increasing fluid/rock ratio from metamorphic peak to retrograde conditions. Isotopic results are compatible with low-temperature H(2)O influx and fO(2) decrease that promoted graphite deposition in retrograde granulites, simultaneous with low density CO(2), CO(2)-N(2) and CO(2)-N(2)-CH(4)-H(2)O fluid inclusions at T = 450-330 degrees C. Graphite delta(13)C results of -10.9 to -11.4 parts per thousand imply CO(2) delta(13)C values of -0.8 to -1.3 parts per thousand suggesting decarbonation of Cambrian marine carbonates with small admixture of lighter biogenic or mantle derived fluids. Based on these results, it is suggested that metamorphic fluids from the central segment of Ribeira Fold Belt evolved to CO(2)-N(2) fluids during granulitic metamorphism at high fO(2), followed by rapid pressure drop at T similar to 400-450 degrees C during late exhumation that caused fO(2) reduction induced by temperature decrease and water influx, turning carbonic fluids into CO(2)-H(2)O (depleting biotite delta(18)O and delta D values), and progressively into H(2)O. When fO(2) decreased substantially by mixture of carbonic and aqueous fluids, graphite deposited forming khondalites. (C) 2010 Elsevier Ltd. All rights reserved.

Quantified Interference: Information Theory and Information Flow

The paper investigates which of Shannon’s measures (entropy, conditional entropy, mutual information) is the right one for the task of quantifying information flow in a programming language. We examine earlier relevant contributions from Denning, McLean and Gray and we propose and motivate a specific quantitative definition of information flow. We prove results relating equivalence relations, interference of program variables, independence of random variables and the flow of confidential information. Finally, we show how, in our setting, Shannon’s Perfect Secrecy theorem provides a sufficient condition to determine whether a program leaks confidential information.

Weed interference on maize (Zea mays) under no tillage system

A field trial was carried out in Brazil in March 2002 with the aim to evaluate the effects of different timing and extension of weedy period on maize productivity. The hybrid Pioneer 30K75 was sowed under 7 t ha(-1) mulching promoted by glyphosate spraying. The treatments were divided in two groups: In the first group, weeds were maintained since the maize sowing until different periods in the crop cycle: 0, 14, 28, 42, 56, 70, and 150 days (harvesting time). In the second group, the maize crop was kept weed free for the same periods of the first group. Weed control was done through hand hoeing. A complete randomized blocks experimental design with five replications was used for plots distribution in the field. Nonlinear regression model was used to study the effects of weedy or weedfree periods on maize productivity. Weed community included 13 families and 31 species. Asteraceae, Poaceae, and Euphorbiaceae were the most abundant families. Results showed that under no tillage condition with 7 t ha-1 mulching at sowing time, the maize crop could cohabit with weed community for 54 days without any yield lost. on the other hand, if the crop was kept weed free for 27 days, the weed interference was not enable to reduce maize production. According to these results one weed control measure between 27 and 54 days after crop emergence could be enough to avoid any reduction in maize productivity.

EFFECTS of MINERAL NUTRITION on INTER- and INTRASPECIFIC INTERFERENCE of PEANUT (Arachis hypogaea L.) and HAIRY BEGGARTICKS (Bidens pilosa L.)

The present work was carried out to study the effects of mineral nutrition on peanut (Arachis hypogaea L) cv. IAC Runner-886 and hairy beggarticks (Bidens pilosa L) growth, when submitted to inter- and intraspecific competition. The treatments consisted of two peanut plants per pot, two hairy beggarticks per pot and one plant of each species per pot. The plants were nourished with Hoagland and Arnon (1950) complete solution, or without potassium, or without phosphorus or without nitrogen. Sixty days after planting, no inter- or intraspecific competition effect on growth characteristics of peanut was verified and nutrition was not a limiting factor to the culture. No interaction between competition and nutrition effects was observed for both species. The weed suffered more negative effects from intraspecific competition and nutrition. The absence of N had a pronounced effect compared to the other elements, resulting in a reduction in all the evaluated characteristics. The deficiency of nutrients and competition affected the weed more than the crop, showing that peanut was more competitive than hairy beggarticks.

Weed interference on coffee fruit production during a four-year investigation after planting

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

Modeling of weeds interference periods in bean

Objetivou-se com este trabalho determinar o período de convivência anterior à interferência das plantas daninhas (PAI) e o período anterior ao dano no rendimento econômico (PADRE) na cultura do feijão, em diferentes espaçamentos (0,45 e 0,60 m) e densidade de plantas (10 e 15 plantas m-1). Os tratamentos foram constituídos de períodos de convivência entre a cultura e as plantas daninhas (0 a 10, 0 a 20, 0 a 30, 0 a 40, 0 a 50, 0 a 60, 0 a 70 e 0 a 80 dias), mais uma testemunha sem convívio com as plantas daninhas. Adotou-se o delineamento experimental de blocos casualizados, com quatro repetições. Os períodos anteriores à interferência (PAI) da cultura foram de 23, 27, 13 e 19 dias após emergência, e os períodos anteriores ao dano no rendimento econômico (PADRE), de 10, 9, 8 e 8 dias, para os tratamentos com espaçamento de 0,45 m e densidades de semeadura de 10 e 15 plantas m-1 e para aqueles com espaçamento de 0,60 m e densidades de semeadura de 10 e 15 plantas m-1, respectivamente, o que reduziu a produtividade de grãos em 63, 50, 42 e 57%, respectivamente, com a presença das plantas daninhas durante todo o ciclo do feijoeiro.

Interference effects in nonplanar wires with a two-dimensional electron gas

We have studied the universal conductance fluctuations (UCF) due to quantum interface in a two-dimensional electron gas (2DEG) grown on the substrates with pre-patterned, sub-micron wires. The dependence of UCF on the angle between the direction of the magnetic field and the substrate has been investigated. We found, that magnetoresistance traces for different angles are completely uncorrelated. A non-planar character of electron motion is responsible for these angular conductance fluctuations. We compared the experimental results with a simple geometrical model.

Occurrence of pneumocystis pneumonia in HIV-infected patients and the interference of the highly active antiretroviral therapy

From the beginning of the AIDS epidemic, pneumocystis pneumonia ( PCP) has been distinguished as one of the most frequent opportunistic diseases with high morbid-mortality. As from 1996, the advent of the highly active antiretroviral therapy ( HAART) has changed the characteristics of such epidemic by reducing its related diseases and, as a result, AIDS-related mortality. With the purpose to estimate PCP occurrence and HAART interference, 376 HIV-infected or AIDS patients were studied from January 1992 to December 2002. Among them, 58 ( 15.5%) PCP cases were found. There was a higher occurrence of PCP in the group of patients in which HAART was not used, with 40 ( 69.0%) of the episodes. As regards the studied period, a tendency to a linear reduction in annual PCP incidence was observed. The mean of T CD4+ lymphocytes in the patients with PCP ( 117 cells/mm(3)) was significantly lower when compared to that of the other individuals ( 325 cells/mm(3)). Therefore, this study suggests a temporal reduction in PCP occurrence related to HAART use with higher T CD4+ lymphocyte counts. Nevertheless, this opportunistic infection still shows significant incidence in AIDS patients. ( NCT00516581).

Mucosal Bridge of the Vocal Fold: Difficulties in the Diagnosis and Treatment

Mucosal bridges are rare laryngeal lesions probably of genetic origin. They may cause dysphonia of varying degrees, especially when associated with other laryngeal lesions such as vocal sulci and cysts. Reports on mucosal bridges are rare, and the better treatment is inconclusive.Aim. To report the authors' experience in 14 cases of mucosal bridge showing details on endoscopic examinations and treatment.Study Design. Retrospective study.Methods. We reviewed the medical records of 14 patients with a diagnosis of mucosal bridge confirmed by video-laryngostroboscopy and direct laryngoscopy who attended the Outpatient Clinic of Voice Disorders of the Discipline of Otorhinolaryngology, Botucatu Medical School, São Paulo State University, São Paulo. Data collected included information on gender, age, symptoms, time of onset, history of intubation, smoking status, alcohol intake, associated laryngeal lesions, treatment, and GRBAS (grade of hoarseness, roughness, breathiness, asthenia, and stress) scale ratings.Results. of 14 patients, 10 were females and four were males. There was a prevalence of adults (n = 12), with only two of the patients being younger than 13 years (10 and 13 years). Mucosal bridges showed no correlations with smoking, alcohol intake, or gastroesophageal and sinonasal symptoms. Voice abuse was reported in 50% of the cases that consisted of patients who had high-voice demand occupations. In seven cases, mucosal bridges were associated with other laryngeal lesions, particularly vocal cysts and sulci. All patients who underwent surgery and phonotherapy showed improved vocal quality.Conclusions. We documented 14 patients with dysphonia caused by mucosal bridge. Promising results were obtained with surgery.

Vocal Fold Nodules: Morphological and Immunohistochemical Investigations

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

Vaccine immune response and interference of colostral antibodies in calves vaccinated against rabies at 2, 4 and 6 months of age born from antirabies revaccinated females

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