374 research outputs found
Utilisation de la clairance plasmatique de l'iolthalamate pour la détermination du débit de filtration glomérulaire chez le chien : comparaison avec les autres méthodes
Le diagnostic de l'insuffisance rĂ©nale chronique (IRC) est souvent tardif et de pronostic mauvais. Les manifestations cliniques apparaissent lorsque 75% des reins sont lĂ©sĂ©s. Une exploration fonctionnelle rĂ©nale prĂ©coce est donc primordiale. Le dĂ©bit de filtration glomĂ©rulaire (DFG) est la variable physiologie d'intĂ©rĂȘt pour Ă©valuer la fonction rĂ©nale. AprĂšs une Ă©tude des principales caractĂ©ristiques histologiques et physiologiques de la fonction rĂ©nale (et plus prĂ©cisĂ©ment de la filtration glomĂ©rulaire), l'auteur dĂ©veloppe les diffĂ©rentes mĂ©thodes de mesures de DFG. Le principe de clairance Ă©tant le plus adaptĂ© Ă la dĂ©termination du DFG, les techniques de rĂ©alisation de clairances plasmatiques et urinaires sont abordĂ©es dans le dĂ©tail. Dans ce travail, l'iothalamate, un produit de contraste, est proposĂ© afin de dĂ©terminer le DFG chez le chien. AprĂšs un rĂ©capitulatif des diffĂ©rentes propriĂ©tĂ©s physico-chimiques et pharmacocinĂ©tiques de cette molĂ©cule, la clairance plasmatique de l'iothalamate est comparĂ©e aux clairances urinaires et plasmatiques des marqueurs plus conventionnels (inuline,crĂ©atinine). Les diffĂ©rents rĂ©sultats obtenus confirment que la clairance plasmatique de l'iothalamate est un bon indicateur du DFG chez le chien sain
Radiation back-reaction in relativistically strong and QED-strong laser fields
The emission from an electron in the field of a relativistically strong laser
pulse is analyzed. At the pulse intensities of \ge 10^{22} W/cm^2 the emission
from counter-propagating electrons is modified by the effects of Quantum
ElectroDynamics (QED), as long as the electron energy is sufficiently high: E
\ge 1 GeV. The radiation force experienced by an electron is for the first time
derived from the QED principles and its applicability range is extended towards
the QED-strong fields.Comment: 4 pages, 4 figure
Emission and its back-reaction accompanying electron motion in relativistically strong and QED-strong pulsed laser fields
The emission from an electron in the field of a relativistically strong laser
pulse is analyzed. At pulse intensities of J > 2 10^22 W/cm2 the emission from
counter-propagating electrons is modified by the effects of Quantum
ElectroDynamics (QED), as long as the electron energy is sufficiently high: E >
1 GeV. The radiation force experienced by an electron is for the first time
derived from the QED principles and its applicability range is extended towards
the QED-strong fields.Comment: 14 pages, 5 figures. Submitted to Phys.Rev.
Relativistic attosecond physics
A study, with particle-in-cell simulations, of relativistic nonlinear optics in the regime of tight focus and ultrashort pulse duration (the λ3λ3 regime) reveals that synchronized attosecond electromagnetic pulses [N. M. Naumova, J. A. Nees, I. V. Sokolov, B. Hou, and G. A. Mourou, Phys. Rev. Lett. 92, 063902 (2004)] and attosecond electron bunches [N. Naumova, I. Sokolov, J. Nees, A. Maksimchuk, V. Yanovsky, and G. Mourou, Phys. Rev. Lett. 93, 195003 (2004)] emerge efficiently from laser interaction with overdense plasmas. The λ3λ3 concept enables a more basic understanding and a more practical implementation of these phenomena because it provides spatial and temporal isolation. The synchronous generation of strong attosecond electromagnetic pulses and dense attosecond electron bunches provides a basis for relativistic attosecond optoelectronics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87762/2/056707_1.pd
Signatures of the Unruh effect from electrons accelerated by ultra-strong laser fields
We calculate the radiation resulting from the Unruh effect for strongly
accelerated electrons and show that the photons are created in pairs whose
polarizations are maximally entangled. Apart from the photon statistics, this
quantum radiation can further be discriminated from the classical (Larmor)
radiation via the different spectral and angular distributions. The signatures
of the Unruh effect become significant if the external electromagnetic field
accelerating the electrons is not too far below the Schwinger limit and might
be observable with future facilities. Finally, the corrections due to the
birefringent nature of the QED vacuum at such ultra-high fields are discussed.
PACS: 04.62.+v, 12.20.Fv, 41.60.-m, 42.25.Lc.Comment: 4 pages, 1 figur
âClip-Stoneâ Filiation Within the Biliary Tract
A case of cholangitis due to the migration of a metal clip used for surgical cholecystectomy 4 years
earlier, is reported. The diagnostic approach and therapeutic options, either endoscopic or surgical are
discussed. The use of resorbable clips during the performance of laparoscopic cholecystectomy should
avoid this type of complication
Antagonism and Antimicrobial Capacity of Epiphytic and Endophytic Bacteria against the Phytopathogen Xylella fastidiosa
Olive quick decline syndrome (OQDS), which is caused by Xylella fastidiosa, poses a severe threat to the agriculture of Mediterranean countries and causes severe damage to the olive trees in Italy. Since no effective control measures are currently available, the objective of this study was the screening of antagonistic bacteria that are potentially deployable as biocontrol agents against X. fastidiosa. Therefore, two approaches were used, i.e., the evaluation of the antagonistic activity of (i) endophytic bacteria isolated from two different cultivars of olive trees (Leccino and Ogliarola salentina) and (ii) epiphytic bacteria isolated from the phyllospheres of different host plant species of X. fastidiosa. In vitro dual culture tests showed that 12 out of 200 isolates inhibited X. fastidiosa growth, with appearances of clear zones between 4.0 and 38.6 mm. 16S rRNA gene sequencing revealed different species of the genera Paenibacillus, Bacillus, Pantoea, Microbacterium, Stenotrophomonas, Delftia, and Pseudomonas. Furthermore, an investigation for antimicrobial activity identified 5 out of the 12 antagonistic bacteria, Paenibacillus rigui, Bacillus subtilis, Bacillus pumilus, Microbacterium oxydans, and Stenotrophomonas rhizophila, that were able to produce culture filtrates with inhibitory activities. Our results are promising for further investigation to develop an eco-sustainable strategy to control X. fastidiosa using biocontrol agents or their secreted metabolites
Femtosecond optical absorption studies of nonequilibrium electronic processes in high Tc superconductors
We report the results of femtosecond optical transient absorption experiments performed on the superconducting compounds YBa2Cu3O7âx(x ⌠0) and Bi2Sr2Ca2Cu3O10+ÎŽ(ÎŽ ⌠0) and nonsuperconducting YBa2Cu3O6+y(y<0.4) for sample temperatures ranging from âŒ7 K to room temperature. Nonequilibrium heating was found to occur on a subpicosecond time scale. A distinct, dramatic increase in the relaxation time was observed for the superconducting samples as the sample temperature was lowered below the critical temperatures of the respective films. Accompanying the increase in relaxation time was an increase in the peak fractional transmissivity change. No such changes were observed for the nonsuperconducting YBCO sample. We believe the above described behavior is electronic in origin and intimately related to the superconductivity of the compounds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69780/2/APPLAB-57-16-1696-1.pd
Subpicosecond timeâresolved studies of coherent phonon oscillations in thinâfilm YBa2Cu3O6+x (x<0.4)
We report the results of the first timeâresolved observation of impulsively generated coherent optical phonon oscillations in the semiconducting cuprate compound YBa2Cu3O6+x (x<0.4). The oscillations, which were probed through timeâresolved transmissivity modulation, had a period of 237 fs at room temperature, corresponding to a Raman active mode of A1g symmetry at 142 cmâ1. No oscillations were observed in the superconducting form of YâBaâCuâO either above or below Tc. The amplitude, frequency, and linewidth of this mode were measured over a temperature range from âŒ7 K to room temperature.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70769/2/APPLAB-58-9-980-1.pd
Ultrafast Radial Transport In A MicronâScale Aluminum Plasma Excited At Relativistic Intensity
Using femtosecond microscopy, we observe a thermal/ionization front expand radially at âŒ108cm/s from a λ2âsize spot of an aluminum target excited at >1018W/cm2. Numerical modeling shows transport is predominantly radiative and may be initially nonlocal. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87543/2/609_1.pd
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