Éditeur(s) : HAL CCSD Springer/Terra Scientific Publishing Company
Résumé : International audience
We report oil the discovery of magnetite nanoparticles ranging in size from 2 to 14 full in the mineralized zones of the Pena Colorada iron-ore deposit, southern Mexico. Micrometric scale magnetite was magnetically reduced and divided into distinct size ranges: 85-56 mu m, 56-30 mu m, 30-22 mu m, 22-15 mu m, 15-10 mu m, 10-7 mu m and 7-2 mu m. Nanometric-scale magnetite in the size range 2-14 nm was identified. The magnetite was characterized by X-ray diffraction, transmitted and reflected light microscope, high-resolution transmission electron microscopy (TEM), high angle annular dark field, Mossbauer spectroscopy and its magnetic properties. Crystallographic identification of nanostructures Was performed using high-resolution TEM. Characteristic changes were observed when the particles make the size transition from micro- to nanometric sizes, as follows: (1) frequency-dependent magnetic Susceptibility percentage (chi FD%) measurements Show high Values (13%) for the 2-14 nm fractions attributed to dominant fractions of superparamagnetic particles; (2) variations of chi FD% < 4.5% in fractions of 56-0.2 mu m occur in association with the presence of microparticles formed by magnetite aggregates of nanoparticles (< 15 nm) embedded in berthierine; (3) Mossbauer spectroscopy results identified a superparamagnetic fraction; (4) nanometric and 0.2-3 mu m grain size magnetite particles require a magnetic field up to 152 mT to reach saturation during the isothermal remanent magnetization experiment; (5) coercivity and remanent magnetization of the magnetite increase when the particle size decreases, probably due to parallel Coupling effects; (6) two-magnetic Susceptibility versus temperature experiments of the same 2-14 nm sample show that the reversibility during the second heating is due to the formation of new magnetite nanoparticles and growth of those already present. during the first heating process.
ISSN: 1343-8832

hal-00413053
https://hal.archives-ouvertes.fr/hal-00413053

Éditeur(s) : Springer
Résumé : Proteinases from hepatopancreas (HP) and gastric juice (GJ) from wild and cultured red octopus (Octopus maya) were characterized. Hepatopancreas assays revealed optimal activity at pH 4, 9-10 and 10 for wild and pH 3, 8, and 9, for cultured octopuses, for total proteinases, trypsin and chymotrypsin, respectively. In the gastric juice, maximum activity was recorded at pH 6, 8, and 7 for total proteinases, trypsin, and chymotrypsin, respectively for both wild and cultured octopus. A reduction on enzyme activity of 70 and 20% was observed in HP and GJ extracts, respectively when protease inhibitor Pepstatin A was used. That result suggests that the main proteases in the HP were aspartic acid proteinases type (possibly Cathepsin D) and some of them were present in the GJ. Dissociating discontinuous polyacrylamide gel electrophoresis showed activity bands between 20 and 28, 30 and 34, 35 and 45, 60 and 70 kDa, and a last one between 75 and 100 kDa. We concluded that extracellular digestion of O. maya takes place in an acid environment, around pH 6. In contrast, intracellular digestion in the HP is developed at pHs between 3 and 4, where cathepsin D could be the most important enzyme for O. maya.
Aquaculture International (0967-6120) (Springer), 2011-06 , Vol. 19 , N. 3 , P. 445-457

Droits : Springer Science+Business Media B.V. 2010
http://archimer.ifremer.fr/doc/00036/14683/17998.pdf
DOI:10.1007/s10499-010-9360-5
http://archimer.ifremer.fr/doc/00036/14683/

Éditeur(s) : HAL CCSD springer Link
Résumé : International audience
Experimental Astronomy

hal-01094521
https://hal.archives-ouvertes.fr/hal-01094521
BIBCODE : 2014ExA...tmp...41R
DOI : 10.1007/s10686-014-9383-4
ARXIV : 1310.0696

Éditeur(s) : Elsevier
Résumé : A study was conducted using a bioenergetics approach to generate information on energy requirement and feed utilization of Litopenaeus stylirostris. Animals (initial mean weight 21 +/- 1 g were fed ad libitum six experimental diets, ranging from 25 to 58% crude protein (CP), for 50 days. Weight gain increased from 21 to 30 g with increasing dietary protein level. Survival rates averaged 80%. Basal metabolism (HeE) and heat increment of feeding (HiE) were monitored using respirometry. HeE was on average I U shrimp(-1) day(-1) or 47 U kg live weight(-1) day (22 kJ/kg(0.8). d(-1)), slightly more than what is observed in fish. HiE averaged 0.2 W/sbrimp(-1) day(-1) or 10 W kg live weight(-1) day(-1) (4 kJ/kg(0.8) d(-1)). It represented 3 1 % and 12% digestible energy intake (DET) for shrimp fed on 58% CP and 25% CP diet respectively. Non-fecal (UE + ZE) energy calculated on the basis of N-ammonia excretion averaged 0.2 jig N-ammonia/g dry wt./ mn or 25 J live shrimp(-1) day(-1) in fasting stage and increased to 40 J in post-prandial stage. Ammonia production increased with increasing dietary crude protein (CP). The O:N ratio indicated that protein was increasingly used as an energy substrate as CP increased. The information was used to construct an energy budget for shrimp fed a protypical 40% CP diet. Gross energy intake (IE) was estimated at 6.5 W live shrimp(-1) day(-1); digestible energy intake (DEI) at 5, urinary and branchial excretion (UE +ZE) at 1.2, total heat production (HE) at 3.2; recovered energy (RE) at 0.6 (or 11% DEI). L. stylirostris adults issued from domesticated strain appeared to be more efficiently utilizing (i.e. converting into carcass energy) protein than carbohydrates. This preliminary energy budget can be used to construct theoretical feed requirement and waste outputs model for L. stylirostris. (C) 2007 Published by Elsevier B.V.
Aquaculture (0044-8486) (Elsevier), 2007-10 , Vol. 271 , N. 1-4 , P. 439-448

Droits : 2007 Published by Elsevier B.V.
http://archimer.ifremer.fr/doc/2007/publication-6263.pdf
DOI:10.1016/j.aquaculture.2006.05.062
http://archimer.ifremer.fr/doc/00000/6263/