Sobre el tipo de metamorfismo regional progresvo hercínico en el Guadarrama oriental (Sistema central español)

Discusión sobre el tipo del metamorfismo regional progresivo hercínico del Guadarrama oriental. Se trata de un tipo intermedio de baja presión, con distena, muy parecido a los tipos que ya se conocen en Galicia, Portugal y Sur de la Península

Gravitomagnetism and the Clock Effect

The main theoretical aspects of gravitomagnetism are reviewed. It is shown that the gravitomagnetic precession of a gyroscope is intimately connected with the special temporal structure around a rotating mass that is revealed by the gravitomagnetic clock effect. This remarkable effect, which involves the difference in the proper periods of a standard clock in prograde and retrograde circular geodesic orbits around a rotating mass, is discussed in detail. The implications of this effect for the notion of ``inertial dragging'' in the general theory of relativity are presented. The theory of the clock effect is developed within the PPN framework and the possibility of measuring it via spaceborne clocks is examined.Comment: 27 pages, LaTeX, submitted to Proc. Bad Honnef Meeting on: GYROS, CLOCKS, AND INTERFEROMETERS: TESTING GENERAL RELATIVITY IN SPACE (22 - 27 August 1999; Bad Honnef, Germany

ELECTRON EXCITATION RATES IN NON-MAXWELLIAN PLASMAS

Nous étudions l'excitation collisionnelle relative à des transitions permise et interdites d'ions héliumoïdes dans deux types de plasmas non-Maxwelliens : plasmas présentant une population suprathermique et plasmas ayant une distribution d'électrons en exp-(v/vm)m. Les taux s'avèrent être extrêmement affectés par le caractère non-Maxwellien pour les valeurs moyennes et grandes de χ/kTe (χ : énergie du seuil ). Il faudrait tenir compte de ce fait et éventuellement en tirer partie dans les études de modélisation de l'amplification X réalisées dans de tels milieux.Electron excitation rates relative to allowed and forbidden transitions of He-like ions are evaluated for two current types of non-Maxwellian plasmas : plasmas with a suprathermal population and plasmas with electron distribution functions of the form exp-(v/vm)m. The rates are shown to be strongly affected by the non-Maxwellian character for moderate and large values of the ratio χ/kTe, χ being the threshold energy. This should be taken into account and hopefully taken advantage of when modelling X-ray amplifications in such plasmas

Expérience d'accélération d'électrons par onde de battement à l'INRSÉnergie

Nous avons mis au point une nouvelle approche pour vérifier expérimentalement l'accélération d'électrons par onde de battement. Il y a plusieurs éléments originaux dans cette approche. Un laser CO2 de haute intensité, opérant simultanément à deux fréquences, est utilisé pour produire un plasma par ionisation laser d'un gaz basse pression avant de stimuler l'onde de battement lorsque la résonance (ωpe = Δω) est atteinte. Une source externe d'électrons de haute énergie (0,2 MeV ≤ E ≤ 1,0 MeV) provenant d'un plasma créé par irradiation d'une cible solide avec un laser CO2 est utilisée. Une gamme d'énergie restreinte (Δ E/E = 0,25 %) de ces électrons est focalisée par un spectrographe dipolaire pour être injectée dans le plasma, parallèlement à l'onde de battement. Cette source d'électrons de haute intensité (= 108 el./cm 2-keV), pulsée (τr = 0,3 ns ) peut facilement être synchronisée avec la production du plasma et est appropriée pour permettre une discrimination facile des électrons accélérés par l'onde de battement. Des mesures de bandes latérales anti-Stokes (8,7 μm) servent à optimiser l'amplitude de l'onde plasma de résonance. Des mesures préliminaires indiquent une accélération effective de 1,0 GeV/m sur une longueur de plasma de 1,5 mm

The importance of dietary selenium on antioxidant status and hormonal profile in post-pubertal gilts

International audienc

Effect of dietary organic and inorganic selenium on antioxidant status, embryo development, and reproductive performance in hyperovulatory first-parity gilts

International audienceThis project aimed to determine the effect of Se as inorganic Na-selenite (MSe) or organic Se-yeast (OSe) on antioxidant status, hormonal profile, reproductive performance, and embryo development in first-parity gilts. Forty-nine gilts were allocated to 1 of the 3 dietary treatments starting at first pubertal estrus and lasting up to 30 d after AI: control [CONT: basal diet (Se = 0.2 mg/kg) without added Se; n = 16], MSe (CONT + 0.3 mg/kg of MSe; n = 16), and OSe (CONT + 0.3 mg/kg of OSe; n = 17). Blood was collected from all gilts on the day after each onset of estrus and on d 30 after AI. Blood was also collected daily from d −4 to d +4 of the third onset of estrus (d 0) in 8 CONT, 9 MSe, and 8 OSe cannulated gilts. Gilts had received, after d 14 and 15 of their third estrus, a hormonal challenge to induce super-ovulation. At slaughter, embryos and corpora lutea (CL) were weighed and measured. Blood Se was less (P < 0.01) in CONT than in Se gilts and greater in OSe than in MSe (P < 0.01) from the first estrus until d 30 of gestation. At the same time, blood Se-dependent glutathione peroxidase (GSH-Px) decreased for CONT gilts, whereas it increased for both Se groups. The increase was greater in MSe than in OSe gilts (treatment × time, P = 0.02). Plasma 3,3′,5-triiodothyronine and thyroxine concentrations for MSe tended to be less than for OSe gilts (P < 0.06). In cannulated gilts, plasma FSH tended to change among treatments (treatment × time, P = 0.06), and plasma estradiol-17β (E2) was less (P = 0.01) for MSe than for OSe. There was no treatment effect on mean litter size or embryonic antioxidant status. The Se content of individual embryos was greater for Se-treated than for CONT gilts (P = 0.03), and Se content of individual embryos and total litter was greater for OSe than for MSe gilts (P < 0.01). The length, weight, and protein content of embryos were greater in OSe than in MSe gilts (P < 0.05). There was no treatment effect on weight, length, Se content, and ferric reducing antioxidant power of CL, but GSH-Px in CL was greater for Se than for CONT gilts (P = 0.02). In summary, the Se status response of gilts to dietary Se was affected by both the quantity and the source of Se dietary supplements. Moreover, the uterine transfer of Se to embryos was improved with OSe as compared with MSe, and this was concomitant with an enhanced development of embryos