acceda Comunidad :

Yacimiento arqueológico de la necrópolis de La Cucaracha, Mazo, La Palma (Islas Canarias)

2010-09-14T08:51:24Z

Título : Yacimiento arqueológico de la necrópolis de La Cucaracha, Mazo, La Palma (Islas Canarias)

Winter mesoscale variations of carbonate system parameters and estimates of CO2 fluxes in the Gulf of Cadiz, northeast Atlantic Ocean

2010-11-03T13:21:16Z

Título : Winter mesoscale variations of carbonate system parameters and estimates of CO2 fluxes in the Gulf of Cadiz, northeast Atlantic Ocean Autor : González-Dávila, Melchor

Wind-driven cross-equatorial flow in the Indian ocean

2011-08-09T08:26:17Z

Título : Wind-driven cross-equatorial flow in the Indian ocean Autor : Pérez-Hernández, M.Dolores; Joyce, Terrence; Vélez Belchí, Pedro Resumen : NCEP Wind-stress and temperature and salinity data from Argo have been used together with a steady model to estimate the meridional velocity and volume and heat transport in the Equatorial Indian Ocean for a seven years period (2003-2009). Total volume transport of the wind stress curl shows a northward and southward flow for theWinter and Summer Monsoon,respectively. The velocity section shows a Somali Current flowing in opposite direction in the Winter and Summer Monsoons. In the Winter Monsoon, the Somali Current is shallow (~ 200 dbar) and flows to the south with and undercurrent below it. In the Summer Monsoon and Transitional Periods, the Somali Current flows to the north and to the south, respectively and extend to (~ 650 dbar) depth. The heat transport across the Equator presents a seasonal reversing, being -0.8PW to the south in the Winter monsoon and +1.2PW in the Summer Monsoon. The annual heat transport is -1.4PW that is mainly carried out by the Somali Current

Why is VO2 max after altitude acclimatization still reduced despite normalization of arterial O2 content?

2012-11-05T09:51:45Z

Título : Why is VO2 max after altitude acclimatization still reduced despite normalization of arterial O2 content? Autor : Calbet, José A.L.; Boushel, R.; Radegran, Goran; Sondergaard, H.; Wagner, P.D.; Saltin, Bengt Resumen : [EN] Acute hypoxia (AH) reduces maximal O2 consumption (VO2 max), but after acclimatization, and despite increases in both hemoglobin concentration and arterial O2 saturation that can normalize arterial O2 concentration ([O2]), VO2 max remains low. To determine why, seven lowlanders were studied at VO2 max (cycle ergometry) at sea level (SL), after 9-10 wk at 5,260 m [chronic hypoxia (CH)], and 6 mo later at SL in AH (FiO2 = 0.105) equivalent to 5,260 m. Pulmonary and leg indexes of O2 transport were measured in each condition. Both cardiac output and leg blood flow were reduced by approximately 15% in both AH and CH (P < 0.05). At maximal exercise, arterial [O2] in AH was 31% lower than at SL (P < 0.05), whereas in CH it was the same as at SL due to both polycythemia and hyperventilation. O2 extraction by the legs, however, remained at SL values in both AH and CH. Although at both SL and in AH, 76% of the cardiac output perfused the legs, in CH the legs received only 67%. Pulmonary VO2 max (4.1 +/- 0.3 l/min at SL) fell to 2.2 +/- 0.1 l/min in AH (P < 0.05) and was only 2.4 +/- 0.2 l/min in CH (P < 0.05). These data suggest that the failure to recover VO2 max after acclimatization despite normalization of arterial [O2] is explained by two circulatory effects of altitude: 1) failure of cardiac output to normalize and 2) preferential redistribution of cardiac output to nonexercising tissues. Oxygen transport from blood to muscle mitochondria, on the other hand, appears unaffected by CH.