Biomedical subjects

C Jouanin

Publications and source records attributed to C Jouanin.

At least 19 recordsLinked to original sources

PubMed2001

Diffraction of light from thin-film polymethylmethacrylate opaline photonic crystals.

Photonic crystals in the form of large area thin films consisting of closely packed polymethylmethacrylate beads were sedimented on glass substrates. The high ordering of the opaline films made it possible to observe a number of fine features in the optical diffraction, including Fabry-Perot oscillations of the reflectivity and branching of the angular dispersion of the Bragg resonances with increase of the angle of incidence of the light beam. Results of calculations of the photonic band structure and simulations of the reflectance spectra agree well with experimental observations.

Journal Article↗

PubMed2000

The attendance cycles of the Cory's Shearwater Calonectris diomedea borealis on Selvagem Grande.

In the Cory's Shearwater Calonectris diomedea borealis of Selvagem Grande (30 degrees 09'N, 15 degrees 52'W), the visits the birds pay to their colonies are cyclic throughout the breeding period. The number of visitors varies regularly between a minimum and a maximum following a sinusoid, the half-period of which is 4.8 +/- 1.5 d (2-8 d). No variation exists according to the status of the birds (breeders or non-breeders) or to the stage of the breeding cycle (pre-egg, incubation or chick rearing) and moon phases have no influence. Among Procellariids, such attendance cycles are related to the length of the pre-egg stage. They are absent when it is short (less than 50 d), present when it is long (more than 60 d), and indifferently present or absent when it is intermediate (50-60 d). Considering the comparative scarcity of the visits of the birds to the colonies during the pre-egg stage, these cycles are likely to play a part essentially in the synchronisation of individuals in colonies and of mates in pairs.

Animals↗

PubMed2000

[Extrarenal salt excretion in oceanic birds].

Oceanic birds feed mainly on marine invertebrates which are isosmotic with sea water. The kidneys of birds have a low concentrating ability and are unable to produce urine with a sodium concentration more than 300mmol/l. How do these birds avoid dehydration? The excess salt is eliminated by the secretory work of a paired gland in the head known for centuries to anatomists as nasal glands or supraorbitary glands, and now that their function is elucidated called salt excreting glands or simply salt glands. They connect through a duct with the nasal cavity. Oceanic birds expel by the nares a clear and colourless watery liquid that contains primarily Na(+) and Cl(-), at high and constant concentration, with a small amount of K(+) and HCO(3)(-). These salt glands do not function continually as the kidney does, becoming active only in response to an osmotic load. The salt gland of oceanic birds is one of the most efficient systems of ionic transport in the living world.

Animals↗

PubMed1996