101 resultados para 12B
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Mineralogical analysis of manganese nodules and crusts collected from Indian ocean aboard Marion Dufresne points to a depth and regional control upon the manganese oxide association: vernadite - birnessite and vernadite - todorokite. Moreover, progressive changes in the vernadite/birnessite ratio as a function of time is clearly seen. Magnetite and titano-magnetite in quantities similar to those of framboidal pyrite in manganese nodules are outlined for the first time. Study of the distribution of metals (Mn, Fe, Ni, Cu, Co) shows a strong latitudinal and regional dependence that may be connected to high productivity zones and to bottom water properties. The problem of mineralogical control on the chemical composition is approached. Finally, it results that any interpretations taking into account all these data haveway to give to the variability of sea-water properties (pH, oxygenation, motions) the prominent control upon manganese nodules composition.
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Material and data were collected at 41 sites in the subpolar North Atlantic Ocean between Scotland and Newfoundland, during the RRS CharlesDarwin CD159 cruise in July 2004 (McCave, 2005). Sites were selected to reflect the major inputs of water that becomes the North Atlantic Deep Water (NADW); the Iceland-Scotland Overflow Water (ISOW), the Denmark Strait Overflow Water (DSOW) and the Labrador Sea Water (LSW). Areas cored were the south Iceland Rise, SE Greenland slope/rise and Eirik Drift, and the Labrador margin. A total of 29 box cores, 19 piston cores, 6 kasten cores, 9 short gravity cores and 20 CTD casts as well as 28 surface water samples were collected during the cruise. Here we present sediment core-top sample ages. The cores were sampled at 1 or 0.5 cm intervals and we used the top 1 or 2 cm, depending on availability of foraminifera in the samples. Sediment samples were disaggregated on an end-over-end wheel, wet sieved at >63 um, and dry sieved to 63-150 and >150 um. Accelerator Mass Spectrometer (AMS) radiocarbon dating was done for each core top based on between 900-1600 monospecific planktonic foraminifera (Globigerina bulloides or Neogloboquadrina pachyderma (sinistral)). All dates were of modern or late Holocene age except site RAPID-08-5B (9806 ± 38 uncorrected 14C years BP) and site RAPID-14-10B (11543 ± 40 uncorrected 14C years BP). The >150 um fraction was split until approximately 300 foraminifera remained and counted for number of lithic grains, benthic foraminifera, planktonic foraminifera and foraminifera fragments. In all but the shallowest sample (Greenland rise, 761m water depth) benthic foraminifera constituted less than 2% of the total >150 um fraction of the sample.
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The information in this booklet may be useful to educators when teaching about animal and plant adaptations. Illinois Learning Standards and Benchmarks: 12.B.1a, 12.B.1b, 12B.2a, 12B.2b.
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The information in this booklet may be useful to educators when teaching about animal and plant adaptations. Illinois Learning Standards Benchmarks: 12.B.1a, 12.B.1b, 12B.2a, 12B.2b.
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Supplements to v. 14 issued 1951-69 (8 v.)
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Approaches to quantify the organic carbon accumulation on a global scale generally do not consider the small-scale variability of sedimentary and oceanographic boundary conditions along continental margins. In this study, we present a new approach to regionalize the total organic carbon (TOC) content in surface sediments (<5 cm sediment depth). It is based on a compilation of more than 5500 single measurements from various sources. Global TOC distribution was determined by the application of a combined qualitative and quantitative-geostatistical method. Overall, 33 benthic TOC-based provinces were defined and used to process the global distribution pattern of the TOC content in surface sediments in a 1°x1° grid resolution. Regional dependencies of data points within each single province are expressed by modeled semi-variograms. Measured and estimated TOC values show good correlation, emphasizing the reasonable applicability of the method. The accumulation of organic carbon in marine surface sediments is a key parameter in the control of mineralization processes and the material exchange between the sediment and the ocean water. Our approach will help to improve global budgets of nutrient and carbon cycles.
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X-ray computed tomography (CT) provides an insight into the progression of dissolution in the tests of planktonic foraminifera. Four species of foraminifera (G. ruber [white], G. sacculifer, N. dutertrei and P. obliquiloculata) from Pacific, Atlantic and Indian Ocean core-top samples were examined by CT and SEM. Inner chamber walls began to dissolve at Delta[CO3**2-] values of 12-14 µmol/kg. Close to the calcite saturation horizon, dissolution and precipitation of calcite may occur simultaneously. Inner calcite of G. sacculifer, N. dutertrei and P. obliquiloculata from such sites appeared altered or replaced, whereas outer crust calcite was dense with no pores. Unlike the other species, there was no distinction between inner and outer calcite in CT scans of G. ruber. Empty calcite crusts of N. dutertrei and P. obliquiloculata were most resistant to dissolution and were present in samples where Delta[CO3**2-] ~ -20 µmol/kg. Five stages of preservation were identified in CT scans, and an empirical dissolution index, XDX, was established. XDX appears to be insensitive to initial test mass. Mass loss in response to dissolution was similar between species and sites at ~ 0.4 µg/µmol/kg. We provide calibrations to estimate Delta[CO3**2-] and initial test mass from XDX.
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Mg/Ca and d18O data for four species of planktic foraminifera (G. ruber (white), G. sacculifer (without sac), N. dutertrei, and P. obliquiloculata) from core top sediments from the tropical Pacific, Atlantic, and western Indian Ocean. Deepwater calcite saturation values (Delta[CO3**2-]) at the sites range from 55 to -23 µmol/kg.
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Entre as principais causas de perdas produtivas em bovinos criados nos trópicos está a infestação pelo carrapato Rhipicephalus (Boophilus) microplus e, consequentemente, dos hemoparasitas transmitidos por ele. A resistência dos zebuínos e de animais cruzados com raças taurinas à infestação por esse ácaro é amplamente conhecida. Entretanto, no que se refere à suscetibilidade às babesioses bovinas, existem evidências de que o grupo genético também pode interferir na resistência, seguindo o mesmo padrão observado para o carrapato vetor, com os taurinos apresentando maior sensibilidade. Assim, este estudo teve por objetivo avaliar a parasitemia por Babesia bovis e Babesia bigemina em 50 novilhas da raça Canchim ( Charolês + Zebu) naturalmente infestadas pelo R. (B.) microplus nas quatro estações do ano durante 24 meses, além de caracterizar o perfil de citocinas que podem estar associados ao fenótipo de resistência e suscetibilidade aos hemoparasitas do gênero Babesia spp. Foram realizadas contagens de fêmeas adultas de carrapatos com tamanho igual ou superior a 4,5 mm de diâmetro, presentes no lado esquerdo de cada bovino. As amostras de DNA extraídas foram submetidas à amplificação por meio da Reação em Cadeia da Polimerase Quantitativa em Tempo Real (qPCR), utilizando iniciadores que flanqueiam fragmentos dos genes mitocondriais do citocromo b (mt-cyt B), específicos para B. bovis e B. bigemina. O RNA extraído do sangue, foi usado para sintetizar o DNA complementar (cDNA) para análise de expressão dos genes do IFN- , TNF- , IL-10 e IL-12B por meio da quantificação relativa (RTqPCR). Foram observadas diferenças significativas (P<0,05) entre os meses das avaliações para a contagem de carrapatos. Entretanto, não houve efeito significativo (P>0,05) nas colheitas realizadas entre novembro de 2013 a janeiro de 2014 e entre os meses janeiro e fevereiro de 2015. A frequência da parasitemia no rebanho foi de 98%. Dentre as amostras de DNA que puderam ser quantificadas pela qPCR, 98% e 95,4% foram positivas para B. bovis e B. bigemina, respectivamente. Com relação ao número de cópias (NC) dos fragmentos dos genes mt-cyt B específicos para B. bovis e B. bigemina foram observados efeitos significativos (P<0,05) para ambas as espécies e interação das mesmas com as colheitas realizadas nas diferentes estações do ano. A análise do nível de expressão de mRNA do IFN- , TNF- e IL-12B revelou que houve um efeito siginificativo (P<0,05) da interação entre animais dos extremos de resistência/suscetibilidade e estações do ano, exceto para IL-10. Conclui-se que, a qPCR apresenta alta sensibilidade e especificidade para o diagnóstico das babesioses bovinas em amostras de sangue e que a oscilação na carga parasitária nas diferentes estações do ano pode estar associada com o perfil de expressão de citocinas apresentada.