850 research outputs found
CO2 perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations
Increasing atmospheric carbon dioxide (CO2) through human activities and invasion of anthropogenic CO2 into the surface ocean alters the seawater carbonate chemistry, increasing CO2 and bicarbonate (HCO3â) at the expense of carbonate ion (CO32â) concentrations. This redistribution in the dissolved inorganic carbon (DIC) pool decreases pH and carbonate saturation state (Ω). Several components of the carbonate system are considered potential key variables influencing for instance calcium carbonate precipitation in marine calcifiers such as coccolithophores, foraminifera, corals, mollusks and echinoderms. Unravelling the sensitivities of marine organisms and ecosystems to CO2 induced ocean acidification (OA) requires well-controlled experimental setups and accurate carbonate system manipulations. Here we describe and analyse the chemical changes involved in the two basic approaches for carbonate chemistry manipulation, i.e. changing DIC at constant total alkalinity (TA) and changing TA at constant DIC. Furthermore, we briefly introduce several methods to experimentally manipulate DIC and TA. Finally, we examine responses obtained with both approaches using published results for the coccolithophore Emiliania huxleyi. We conclude that under most experimental conditions in the context of ocean acidification DIC and TA manipulations yield similar changes in all parameters of the carbonate system, which implies direct comparability of data obtained with the two basic approaches for CO2 perturbation
Statistical transmutation of quantum bosonic strings coupled to general four-dimensional Chern-Simons theory
A bosonic string coupled to the generalized Chern-Simons theory in 3+1D
acquires a magnetic field along itself, when it is closed, and a topological
charge at its extremity, when it is open. We construct the creation operators
for the full quantum field states associated to these strings and determine the
dual algebra satisfied by them. We show that the creation operator fo the
composite state of a quantum closed bosonic string, bearing a magnetic flux,
and a topologically charged open bosonic string, possesses generalized
statistics. The relation of our results with previous approaches to the problem
is also established.Comment: 4 pages, Revtex
Short-term response of the coccolithophore Emiliania huxleyi to an abrupt change in seawater carbon dioxide concentrations
The response of the coccolithophore Emiliania huxleyi to rising CO2 concentrations is well documented for acclimated cultures where cells are exposed to the CO2 treatments for several generations prior to the experiment. The exact number of generations required for acclimation to CO2-induced changes in seawater carbonate chemistry, however, is unknown. Here we show that Emiliania huxleyi's short-term response (26 h) after cultures (grown at 500 ÎŒatm) were abruptly exposed to changed CO2 concentrations (~190, 410, 800 and 1500 ÎŒatm) is similar to that obtained with acclimated cultures under comparable conditions in earlier studies. Most importantly, from the lower CO2 levels (190 and 410 ÎŒatm) to 750 and 1500 ÎŒatm calcification decreased and organic carbon fixation increased within the first 8 to 14 h after exposing the cultures to changes in carbonate chemistry. This suggests that Emiliania huxleyi rapidly alters the rates of essential metabolical processes in response to changes in seawater carbonate chemistry, establishing a new physiological "state" (acclimation) within a matter of hours. If this relatively rapid response applies to other phytoplankton species, it may simplify interpretation of studies with natural communities (e.g. mesocosm studies and ship-board incubations), where often it is not feasible to allow for a pre-conditioning phase before starting experimental incubations
DendĂȘ: futuro do Amazonas.
Ecologia. Mercado. Estimativas. Potencial do Amazonas.bitstream/item/198356/1/Dende-futuro-do-Amazonas.pd
O ENGAJAMENTO POLĂTICO CULTURAL DE NIETZSCHE EM SUAS REFLEXĂES SOBRE A ARTE
A presente pesquisa pretende abordar como Nietzsche foi um pensador
extremamente engajado com as questÔes culturais de sua época em suas
reflexÔes sobre a arte. Tomando como pano de fundo, a ideia de um Nietzsche
que atravĂ©s da filosofia e pela arte, faz uma crĂtica Ă cultura, em Ășltima
instĂąncia, o que defenderemos nessa pesquisa Ă© um conceito de engajamento
que estå ancorado nas reflexÔes de Nietzsche sobre a arte, mas que, no
entanto, indicam que ele não tinha apenas uma preocupação puramente
estĂ©tica, mas, sim polĂtico cultural. Esta hipĂłtese de engajamento polĂtico
cultural serĂĄ demonstrada atravĂ©s dos conceitos de Bildung e de mĂșsica
popular nos escritos do primeiro Nietzsche. Findando nosso trabalho o texto O
Caso Wagner serĂĄ analisado polĂtico culturalmente como crĂtica ao projeto da
modernidade, trabalhando conceitos como décadence, niilismo, arte
decadente, indĂșstria cultural e grande polĂtica; sedimentando a ideia geral de
um Nietzsche engajado polĂtico culturalmente.
Palavras chaves: Engajamento polĂtico-cultural. Arte. Extemporaneidade.
CrĂtica. Modernidade. Niilismo. DĂ©cadence. Grande polĂtica
Vegetative compatibility and genetic analysis of Colletotrichum lindemuthianum isolates from Brazil.
Geometric Quantization of Topological Gauge Theories
We study the symplectic quantization of Abelian gauge theories in
space-time dimensions with the introduction of a topological Chern-Simons term.Comment: 13 pages, plain TEX, IF/UFRJ/9
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