Showing papers by "University of Nice Sophia Antipolis published in 1972"
TL;DR: In the freshwater-adapted eel the osmotic permeability is considerably higher than the diffusional permeability, which supports the previously advanced hypothesis concerning the presence of water-filled channels in the branchial epithelium.
Abstract: 1. The temperature dependence of diffusional permeability to water was studied in freshwater-adapted and seawater-adapted eels. The pattern of temperature acclimation is discussed. 2. The ratio of water permeability to sodium permeability is approximately 3 at 25°C, but falls to 1 at 5°C. This drop is mainly due to a diminution of the water permeability, the temperature coefficients being much higher for water than for sodium. 3. The relatively independent variations of water and sodium permeabilities in the seawater-adapted fish probably indicate a certain dissociation between water movements and salt movements. 4. In the freshwater-adapted eel the osmotic permeability is considerably higher than the diffusional permeability, which supports the previously advanced hypothesis concerning the presence of water-filled channels in the branchial epithelium. 5. In the seawater-adapted eel the osmotic permeability is lower than the diffusional permeability, this difference being greater the lower the temperature. This surprising result must signify either that the osmotic pressure difference between blood and sea water does not represent the true osmotic gradient across the membrane, or that a reabsorption of water linked with a movement of solutes occurs in a specialized region of the gill.
99 citations
TL;DR: It would seem that the more perfect the semipermeability of the gill membrane and the weaker the transepithelial osmotic gradient, the greater is the branchial porosity.
Abstract: 1. Comparative effects of temperature on the permeability of the gill to water and to sodium were studied in the marine sea perch Serranus and the freshwater goldfish Carassius . 2. The acclimation Q 10 for the water fluxes is higher in the freshwater fish than in the marine fish. 3. In the goldfish the osmotic permeability ( P os ) is greater than the diffusional permeability (P dlf ) at all acclimation temperatures, suggesting the presence of ‘waterfilled channels’ in the branchial membrane. In the sea perch, on the other hand, P os / P dlf is approximately 1, indicating that water movements probably occur by simple diffusion. 4. The permeabilities to water and to sodium are similar in the sea perch but very different in the goldfish. Considering these results together with those from a similar study on an elasmobranch, it would seem that the more perfect the semipermeability of the gill membrane and the weaker the transepithelial osmotic gradient, the greater is the branchial porosity. 5. Assuming that temperature changes do not cause modification of the branchial surface or relative permeabilities to water and to sodium the independence of the temperature-coefficient variations for water and for sodium indicates a certain dissociation between the movements of salt and of water, in the sea perch. In the goldfish, assuming a constant branchial surface and in view of the fact that P os > P dif the high temperature coefficients for the water fluxes suggest that the water in the ‘water-filled channels’ is in a highly organized state.
40 citations
TL;DR: In this paper, the conductivity of TEA-TCNQ 2 has been measured over the temperature range from 77 to 355°K, and the majority carrier mobility at 77°K was evaluated from space charge limited currents as 0.25 cm 2 /V-sec.
29 citations
TL;DR: In this article, an anisotropic and temperature dependent activation energy was observed for the electrical conductivity of a single-phase circuit, where the activation energy depends on the temperature and conductivity.
16 citations
TL;DR: In this paper, the preferred conformations of a nucleotide are predicted for the first time, in the present work, by quantum calculations, and they are shown to be stable with respect to three angular parameters denoted by 13 1, 02, X.
10 citations
TL;DR: As(CH3)3 is obtained in good yields from the normal Grignard procedure in ethyl ether, when isolated through its silver or copper nitrate complexes.
Abstract: As(CH3)3 is obtained in good yields from the normal Grignard procedure in ethyl ether, when isolated through its silver or copper nitrate complexes.
8 citations
TL;DR: In this paper, the conductivity of the freshly prepared yellow adduct of phenothiazine and iodine in acetonitrile is due in about equal parts to 2:3 and 1:2 complexes at 20°C.
8 citations
TL;DR: The basal beds on the Shatsky Rise cored during Leg 6 of the Deep Sea Drilling Project are the oldest sediments recovered to date in the Pacific Ocean based on benthonic Foraminifera.
Abstract: The basal beds on the Shatsky Rise cored during Leg 6 of the Deep Sea Drilling Project are the oldest sediments recovered to date in the Pacific Ocean Based on benthonic Foraminifera, the sediments correlate with the lower Barremian to upper Hauterivian (Lower Cretaceous) rather than the Upper Jurassic or Lower Cretaceous as previously reported Thus the oldest sediments presently known from the Pacific Ocean are considerably younger than those in the western North Atlantic Ocean (Oxfordian; Upper Jurassic)
8 citations
TL;DR: A study by Extended Hiickel Theory of the D-ribose (C, , -exe)-phosphate unit finds the allowed conformations of the unit are found to be in agreement with those obtained from empiric calculations and also with observed structures.
5 citations
TL;DR: In this paper, some results concerning piezo reflectance, thermo-reflectance, electro reflectance and electro-transmittance of Ag and Au films are given, as well as their properties in modulation spectroscopy.
4 citations
TL;DR: In this article, the enthalpies of addition between phosphorus compounds and boron trifluoride were correlated with different effects produced by groups linked to the phosphorus atom.
TL;DR: In this paper, it is shown that the remedy is simple and unique, at least for Regge-Regge cuts, and that the absorption correction depends on one parameter whose effect is to modify the conventional strength of the absorption by a factor ranging from 0.1 to 1.6.
TL;DR: In this paper, the changes in the dielectric constant of Ag films 1000 A thick, in a direction parallel and perpendicular to the film, have been computed from piezoreflectance spectra measured at an angle of incidence of 45° and light polarized s and p.
TL;DR: In this article, the authors used a Reggeized Deck model similar to that proposed by Berger and showed that this model, which conserves neither s -channel nor t -channel helicity, is able to reproduce the isotropic azimuthal distributions found experimentally, when the events are selected according to their location on a longitudinal phase space plot.
TL;DR: In this paper, a reinvestigation des systemes (Cu-M) de concentration avec transfert is performed, and two series of results sont comparees and discutees.
Abstract: L’utilisation de cellules a membranes de verre reversibles par rapport aux ions alcalins, et l’etude des proprietes de transport ionique a travers ces membranes, nous a permis une reinvestigation des systemes (Cu — M) Cl deja etudies avec des cellules de concentration avec transfert.Les deux series de resultats sont comparees et discutees. Une estimation du potentiel de jonction liquide-liquide, ainsi que des nombres de transport internes, pour les cellules avec transfert est presentee.
TL;DR: In this article, a set of tests are proposed for the spin assignment for baryon resonances with 92 ⊽ J ⩽ 192, and when J is known, they are used to test the dynamical assumption that all helicity amplitudes for the reaction have the same phase, this without a polarized target and without observing a parity-violating decay.
TL;DR: The electrical activity recorded at the surface of the frog's nervous olfactory structures shows two very different patterns in connection with the amphibiotical life of the animal.