Search results for "Core"
showing 10 items of 1999 documents
Near-IR-to-visible emission in ytterbium-doped silica fiber at in-core 488-nm pumping
2008
We report near-IR-to-visible broadband emission in Ytterbium-doped silicate fiber (YF) at 488-nm in-core excitation. This emission is revealed to originate from Yb3+-Yb3+ pair clusters (900 – 1200-nm band), whose presence is proved by a separate study of cooperative processes in the fiber, and Yb2+ phototropic centers (600 – 900-nm band) provisionally accepted to be present in the YF.
Vertical root fracture in endodontically treated teeth: A review of 25 cases
2001
Abstract Objective: We sought to examine the clinical conditions under which 25 endodontically treated teeth underwent vertical root fracture (VRF) and to relate this condition to the time elapsed from endodontic treatment to fracture. Study Design: This was a retrospective study in which we reviewed 25 case histories of patients with postendodontic VRF and studied the effect of various pretreatment and posttreatment factors as they related to VRF. Results And Conclusions: The mean time to VRF was 54 months; this was not significantly influenced by the presence or absence of prior restoration or by the presence or absence of a crown fitting. The use of a prefabricated, cylindrical, cemented…
Sulle tracce del manticora. La zoologia dei confini del mondo in Grecia e a Roma
2003
Uno studio sulla zoologia fantastica in Grecia e a Roma. Attraverso l’analisi di tutte le versioni della rappresentazione relativa al manticora, favoloso animale con la testa di uomo, il corpo di leone e la coda di scorpione, si mostrano i meccanismi della trasmissione del sapere paradossografico all’interno del genere della Naturalis Historia degli antichi.
Towards a rapidly rotating liquid sodium dynamo experiment
2002
The main characteristics of the Earth's dynamo are reviewed. The combined actions of Coriolisand Lorentz forces lead to the so--called ``magnetostrophic'' regime. We derive an estimate of the power needed to sustain the magnetic field in this regime. We show that an experimentwith liquid sodium can be designed to operate in the magnetostrophic regime. Such an experiment would bring most valuable informations on the mechanisms of planetary dynamos. In order toprepare this large--scale experiment and explore the magnetostrophic balance, a smaller scale liquid sodium set--up has been designed and is being built. It consists of a rapidly rotating spherical shell filled with liquid sodium, in wh…
Nonlinear femtosecond pulse propagation in all-solid photonic bandgap fiber
2009
Nonlinear femtosecond pulse propagation in all-solid photonic bandgap fiber is investigated experimentally and numerically for both the photonic bandgap guiding in the central silica core and the total internal reflection in germanium doped inclusions.
Stimulated Brillouin scattering in Germanium-doped-core optical fibers up to 98% mol doping level
2018
International audience; We experimentally investigate stimulated Brillouin scattering in several highly GeO2-doped optical fibers and report wide frequency tunability over more than 3 GHz and Brillouin gain 7 times larger than in standard silica fibers.
Environmental effects on the natural vibrations of nanoplatelets: a high pressure study.
2017
International audience; Resonant acoustic modes from ultrathin CdS colloidal nanoplatelets (NPLs) are probed under high pressure using low frequency Raman spectroscopy. In particular we focus on the characterization of the recently evidenced mass load effect that is responsible for a significant downshift of the NPL breathing frequency due to the inert mass of organic ligands. We show that a key parameter in the observation of the mass effect is whether the surrounding medium is able to support THz acoustic wave propagation, at a frequency close to that of the inorganic vibrating core. At low pressures, surface organic molecules show a single particle-like behavior and a strong mass effect …
Second zero dispersion wavelength measurement through soliton self-frequency shift compensation in suspended core fibre
2008
International audience; A simple experimental technique to evaluate the second zero dispersion wavelength of very small core microstrutured fibres is described. Based on the effect of soliton self-frequency shift and its subsequent compensation in the vicinity of the second zero dispersion. the proposed method is applied to both standard and suspended core microstructured fibres by simply measuring the frequency stabilised soliton spectrum, avoiding any calculation and knowledge of any experimental parameters.
A method for the preparation of repacked soil cores with homogeneous aggregates for studying microbial nitrogen transformations under highly controll…
1998
International audience; he feasibility of studies on nitrate transformations during incubation in controlled conditions of air-filled porosity using a method of soil core preparation was investigated. Repacked cores were obtained by uniaxial confined compression in a cylindrical mould of a mass of calibrated and conveniently wet aggregates with a water content selected to saturate the textural porosity of the soil aggregates, imposing structural porosity and thereby producing controlled conditions of aeration. The principle and the descrip- tion of the incubation method are explained and some denitrification and respiration data obtained with low and increasing OZ partial pressures are pres…
Effets simultanés de niveaux croissants de glucose et de pressions partielles en oxygène sur la dénitrification et la réduction dissimilative du nitr…
1998
International audience; Dissimilatory nitrate reduction to ammonium (DNRA) and its importance in comparison to denitrification were studied in soil samples artificially repacked to control water potential and porosity, and incubated for 72 h. Labelled nitrate (100 mg N.kg-’ dry soil, 21.8 % 15N in excess) and increasing levels of glucose-C (250, 500 and 1 000 mg glucose-Ckg-’ dry soil) were initially added to the soil samples to obtain increasing glucose-C/nitrate-N ratios of 2.5,5 and 10, which were then subjected to different 0, partial pressures (0,0.5, 1.0 and 2.0 % (v/v)). The results confirmed the good reproducibility of the experimental condi- tions using this method. Denitrification…