Distinctive Picosecond Spin Polarization Dynamics in Bulk Half Metals.

Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce an exotic picosecond spin dynamics. In particular, conversely to what is observed in conventional metals and semiconductors, the thermalization process in HMs leads to a long living partially thermalized configuration characterized by three Fermi-Dirac distributions for the minority, majority conduction, and majority valence electrons, respectively. Remarkably, these distributions have the same temperature but different chemical potentials. This unusual thermodynamic state is causing a persistent nonequilibrium spin polarization only well above the Fermi energy. Femtosecond spin dynamics experiments performed on Fe_{3}O_{4} by time- and spin-resolved photoelectron spectroscopy support our model. Furthermore, the spin polarization response proves to be very robust and it can be adopted to selectively test the bulk HM character in a wide range of compounds.

Continuous lighting inhibits the onset of reproductive cycle in pikeperch males and females.

The effect of a constant photoperiod on the inhibition of male and female reproductive cycles was studied in pikeperch Sander lucioperca. Over a 153-day period, batches of pikeperch (2 years, 950 g) breeders were kept under either under natural or artificial photoperiod conditions (24L:0D) (30-35 fish/tank, triplicate) and sampled in late June (start of the photoperiod decrease in natural conditions), late August (start of temperature decrease) and late November (exogenous vitellogenesis) (7-10 fish/tank/sampling date). Morphological parameters, sexual steroids, alkaline-labile phosphate (µg/mL) levels and gamete developmental stages were investigated. Gonado-somatic index (%), developmental stages and sexual steroid levels (17ß-estradiol, testosterone and 11-ketotestosterone, ng/mL) in both sexes and oocyte diameter (µm) and plasma alkaline-labile phosphate (µg/mL) in females were lower in response to a continuous lighting (24L:0D). In both sexes, continuous lighting applied in June for 153 days totally inhibited or delayed the onset of the reproductive cycle. In conclusion, photoperiod manipulation can be used to delay the pikeperch reproductive cycle, even if temperature decreases. This is the first report of the inhibitory effect of photoperiod on the onset of the reproductive cycle in pikeperch.

[Cytotoxic activity of two cyclic peptides from the latex of Jatropha integerrima Euphorbiaceae]. / Etude de l'activite cytotoxique de deux cyclopeptides isoles du latex de jatropha integerrima euphorbiaceae.

Activity-guided fractionation of the ethyl acetate extract of the latex of Jatropha integerrima Euphorbiaceae combinated with cytotoxic assay against the KB human nasopharyngeal carcinoma cells, resulted to the isolation by chromatographic methods including HPLC of two new cyclopeptides: integerrimacyclopeptide4 and integerrima cyclopeptide B. The amino acid composition was established after hydrolysis and derivatization. All chiral amino acids were L configuration and were hydrophobic. Their sequences were determined by MS fragmentations (ESI-q-TOF, MS/MS) and confirmed by 2D NMR homo- and heteronuclear studies. Integerrimacyclopeptide A was a cyclooctapeptide with m/z 766 corresponding to the molecular formula C37H66N8O9. Analysis of mass spectra gave b(n) and a(n) acylium ion series which the sequence could be deduced: cyclo(Leu-Gly-Ser-Ile-Ile-Leu-Gly-lle). This structure was confirmed by interpretation of HMBC and ROESY spectra. Likewise, integerrimacyclopeptide B was a cycloheptapeptide with m/z 651 and C31H53N7O8 as molecular formula containing one proline residue: cyclo(Pro-Gly-Thr-Ile-Gly-Ile-Leu). These two cyclic peptides exhibited significant cytotoxic activityin vitro against KB tumorales cells with respective IC50 values of 0.46 +/- 0.04 and 0.66 +/-0.08 microg/ml.