GDH activity and ammonium excretion in the marine mysid, "Leptomysis lingvura": effects of age and starvation

[EN] Ammonium (NH4+) release by bacterial remineralization and heterotrophic grazers determines the regenerated fraction of phytoplankton productivity, so the measurement of NH4+ excretion in marine organisms is necessary to characterize both the magnitude and the efficiency of the nitrogen cycle. Glutamate dehydrogenase (GDH) is largely responsible for NH4+ formation in crustaceans and consequently should be useful in estimating NH4+ excretion by marine zooplankton.
Here, we address body size and starvation as sources of variability on the GDH to NH4+ excretion ratio (GDH/RNH4+). We found a strong correlation between the RNH4+ and the GDH activity (r2 = 0.87, n = 41) during growth. Since GDH activity maintained a linear relation (b = 0.93) and RNH4+ scaled exponentially (b =0.55) in well fed mysids, the GDH/RNH4+ ratio increased with size. However, the magnitude of its variation increased even more when adult mysids were starved. In this case, the GDH/RNH4+ ratio ranged from 11.23 to 102.41.

GDH activity and ammonium excretion in the marine mysid "Leptomysis lingvura": effects of age and starvation

Máster Universitario en Oceanografía

Effect of the Canary Islands in the blockage and mixing of the North Atlantic eastern water masses

[EN] We apply an inverse model to a hydrographic cruise that completely closes the Canary Islands to investigate their effect on the water masses transports. Most central waters are transported south between the eastern islands and the African coast, with 2.5 Sv out of a total of 3.5 Sv. Intermediate waters are effectively blocked by the islands passages, with Mediterranean/Antarctic waters predominantly found north/south of the islands, and most deep waters loop around the archipelago plateau. A process model upholds the existence of intense two-way exchange between central and intermediate waters along the eastern passage, with vertical velocities of order 10 m s.

Multiproperty correlation of experimental data of the binaries propyl ethanoate+alkanes (pentane to decane). New experimental information for vapor-liquid equilibrium and mixing properties

[EN]A thermodynamic study is carried out on binary systems composed of propyl ethanoate with six alkanes, from pentane to decane. Vapor pressures of the ester and the isobaric vapor−liquid equilibria of these six mixtures were measured at 101.32 kPa in a small-capacity ebulliometer and also the mixing properties yE = vE,hE over a range of temperatures and at atmospheric pressure. Adequate correlations are drawn for the surfaces yE = yE(x,T) with an interpretation on the behavior of the mixtures and also using cp E data from literature.

Solutions of alkyl methanoates and alkanes: Simultaneous modeling of phase equilibria and mixing properties. Estimation of behavior by UNIFAC with recalculation of parameters.

[EN]Isobaric vapor–liquid equilibria at p = 101.32 kPa (iso-p VLE) and the mixing properties, hE and vE, are determined for a set of twelve binary solutions: HCOOCuH2u+1(1)+CnH2n+2(2) with u = (1–4) and n = (7– 9). The (iso-p VLE) present deviations from the ideal behavior, which augment as u diminishes and n increases. Systems with [u = 2,3 n = 7] and [u =4 , n = 7,8] present a minimum-boiling azeotrope. The nonideality is also reflected in high endothermic values, hE > 0, and expansive effects, vE > 0, for all the binaries, which increase regularly with n

Experimental analysis of coaxial jets: instability, flow and mixing characterization

The velocity and mixing field of two turbulent jets configurations have been experimentally characterized by means of cold- and hot-wire anemometry in order to investigate the effects of the initial conditions on the flow development. In particular, experiments have been focused on the effect of the separation wall between the two streams on the flow field. The results of the experiments have pointed out that the wake behind a thick wall separating wall has a strong influence on the flow field evolution. For instance, for nearly unitary velocity ratios, a clear vortex shedding from the wall is observable. This phenomenon enhances the mixing between the inner and outer shear layer. This enhancement in the fluctuating activity is a consequence of a local absolute instability of the flow which, for a small range of velocity ratios, behaves as an hydrodynamic oscillator with no sensibility to external perturbations. It has been suggested indeed that this absolute instability can be used as a passive method to control the flow evolution. Finally, acoustic excitation has been applied to the near field in order to verify whether or not the observed vortex shedding behind the separating wall is due to a global oscillating mode as predicted by the theory. A new scaling relationship has been also proposed to determine the preferred frequency for nearly unitary velocity ratios. The proposed law takes into account both the Reynolds number and the velocity ratio dependence of this frequency and, therefore, improves all the previously proposed relationships.

Gender, age and ethnic aspects of analgesia in acute abdominal pain: is analgesia even across the groups?

Numerous studies have shown differences in pain perception between men and women, which may affect pain management strategies.