303 research outputs found
Evanescent-Field-Induced Second Harmonic Generation by Noncentrosymmetric Nanoparticles
No full textWe demonstrate the excitation of second harmonic radiation of noncentrosymmetric nanoparticles dispersed on a planar optical waveguide by the evanescent field of the guided mode. Polarization imaging reveals information on the orientation of the crystal axis of individual nanoparticles. Interference patterns generated from adjacent particles at the second harmonic frequency are - to the authors knowledge - observed for the first time. The actual form of the interference pattern is explained on the basis of a dipole radiation model, taking into account the nanoparticles' orientation, surface effects, and the characteristics of the imaging optics
Nonlinear bio-imaging and detection with ultrafast lasers
No full textAprès une introduction théorique (Chapitre 1) et le passage en revue du matériel expérimental utilisé (Chapitre 2), les différentes expériences sont regroupées en trois chapitres distincts selon leur thématique. Tout d'abord, l'utilisation de nano-cristaux non-linéaires comme marqueurs pour la microscopie est démontrée (Chapitre 3). Puis, le développement d'un nouveau façonneur d'impulsions laser et l'application d'un nouveau algorithme aux problèmes de contrôle optimal sont décrits (Chapitre 4). Pour finir, la question de la conservation de la phase des impulsions laser lors de leur propagation au travers d'une atmosphère turbulente est abordée (Chapitre 5)
A Precision measurement of the number of neutrino species
No full textWe have measured the cross section for e + e − →hadrons over the center of mass energy range of the Z 0 peak, from 88.22 to 95.03 GeV. We determine the Z 0 mass M z =91.164±0.013 (experiment) ±0.030 (LEP) GeV. Within the framework of the standard model we determine the invisible width, Γ invisible =0.502±0.018 GeV, and the number of light neutrino species, N ν =3.01±0.11. We exclude the existence of a supersymmetric scalar neutrino having a mass less than 31.4 GeV, at the 95% confidence level. We performed a model independent combined fit to the e + e − →hadrons and e + e − → μ + μ − data to determine total width, leptonic width and hadronic width of the Z 0
Mass limits for scalar muons, scalar electrons, and winos from e<sup>+</sup>e<sup>−</sup> collisions near √ = 91 GeV
No full textWe have searched for scalar muons μ , scalar electrons ẽ, and winos W̃ from the reactions e + e − → e ̃ + e ̃ − , μ + μ − , W ̃ + W ̃ − at √s ∼ 91 GeV with an integrated luminosity of 157 nb −1 . We have searched for μ + μ − , e + e − , or e− μ final states with missing transverse momentum P T > 6 GeV. These final states are signatures for the production of ẽ, μ , and W̃. We found no events. Our results are M μ > 41 GeV , M e ̃ > 41 GeV , and M W ̃ > 44 GeV at the 95% confidence level
Fetal echocardiography in pregnancies of women with congenital heart disease--clinical utility and limitations
No full textWomen with important cyanotic or uncyanotic, operated or unoperated congenital heart disease (CHD) have been shown to carry an inherent risk during pregnancy for themselves and for their fetus. Obstetrical and fetal echocardiography has recently been upgraded by new technical developments in ultrasound machines. These improvements have increased the detection rate of congenital malformations and cardiac anomalies which ranged in the past between 4 and 60% for significant anomalies. Obesity or an unfavourable position of the fetus may, however, obscure the imaging quality and cause limitations to visualise the fetal heart from different angles and thus prevent the detection of anomalies. In addition, several cardiac anomalies develop throughout pregnancy and may not yet be present at an early date of screening. While the risk for a congenital cardiac malformation (CCM) in a normal population is 0.8-1%, the recurrence rate for CCM increases to 2 to 3% when a previous child has been affected but will become significantly higher when genetically determined anomalies have affected a family member or when the pregnant woman (5.8%) has CHD. The aim of fetal screening in women with CCM is to ascertain normal intrauterine growth, to exclude fetal CHD and/or to ascertain a malformation or arrhythmia which has been suspected during an obstetrical screening. The acquired detailed echocardiographic knowledge of the malformation or arrhythmia allows the explanation of a CCM to the future parents, to present therapeutic options during pregnancy or after birth and to plan delivery in a tertiary center that provides early cardiovascular and/or catheter interventions and disposes of intensive care facilities for affected newborns. Under certain conditions, termination can be discussed in early pregnancy. Very recent publications have shown how important a prenatal diagnosis can become in a new-born with transposition of the great arteries and a very restrictive foramen ovale (Circulation 1999). Therapeutic measures in the fetus have been attempted with very limited success so far; successful life saving treatment does, however, exist for fetal arrhythmias
Caractéristiques des noyaux stables
No full textTableaux donnant, pour le neutron et les différents noyaux, de l'hydrogène au bismuth, les valeurs relatives (en général par rapport au proton) des rapports gyromagnétiques, les spins, les moments magnétiques nucléaires et les moments électriques quadrupolaires. Bibliographie jusqu'à la fin de I949
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