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L Leroy

Publications and source records attributed to L Leroy.

18 recordsLinked to original sources
PubMed2006

Incoherent and coherent writing and erasure of cavity solitons in an optically pumped semiconductor amplifier.

Cavity solitons in semiconductor amplifiers were, from the beginning of their study and observation, obtained either spontaneously or in a controlled manner by local coherent excitation. We describe two experiments that demonstrate coherent and, we believe for the first time, incoherent writing and erasure of cavity solitons in an optically pumped vertical-cavity semiconductor amplifier by short optical pulses.

Journal Article↗
PubMed2004

Organization and orientation of amphiphilic push-pull chromophores deposited in Langmuir-Blodgett monolayers studied by second harmonic generation and atomic force microscopy.

Orientation and organization of two amphiphilic push-pull chromophores mixed with two phospholipids (dipalmitoylphosphatidylcholine and dioleoylphosphatidylcholine) in Langmuir-Blodgett (LB) monolayers are investigated by second harmonic generation. The LB monolayers have also been characterized by atomic force microscopy and UV-vis spectroscopy. The effective molecular orientations and hyperpolarizabilities of the chromophores are studied as a function of the phospholipid concentrations. The experimental results are discussed within the frame of a model of orientational distribution of the chromophores which gives the orientational mean angle and bounds on the orientational disorder. The mean orientation of the chromophores is found to be within 45-55 degrees whereas their hyperpolarizability coefficients, measured with respect to quartz, are estimated to be in the range (0.3-0.7) x 10(-27) esu taking account of the maximal orientational disorder.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Physico-chemical properties of the heat-induced 'superaggregates' of amphotericin B.

The aggregation state of amphotericin B (AmB) was previously reported to modulate its therapeutic efficiency. As a preliminary study to test the biological effects of 'superaggregates' generated by heat treatment, we present spectroscopic data related to their formation in aqueous solutions. Drastic changes in the AmB aggregation state in water were shown to occur on heating at 50-60 degrees C. The concentration of the aggregates formed at high (A(t)) or room (A) temperature, and the concentration of the monomeric form (M) of AmB were calculated by processing absorption data. The thermally induced conversion from A to A(t) depends on the AmB concentration. Rayleigh scattering measurements suggest that the A(t) aggregates are larger than the A aggregates. At room temperature, the condensation rate of A with M-leading to the 'superaggregated' form A(t)-was slower and depended on the concentration of M. The superaggregated species A(t) was shown to be the most chemically stable species. Physico-chemical properties of these superaggregates are discussed as a potential new solution to improve the therapeutic efficacy of AmB.

Journal Article↗
PubMed1997

Release of amphotericin B from delivery systems and its action against fungal and mammalian cells.

Spectroscopic studies of four amphotericin B (AmB) lipid preparations--small negatively charged unilamellar vesicles "AmBisome", positively charged oligolamellar liposomes "Ampholiposomes", AmB Lipid Complex "L-AmpB33"--and AmB association with gamma cyclodextrin demonstrated that the composition of drug delivery system directly influences AmB organization. The aggregation state and release in external medium of AmB was monitored by circular dichroism and UV-visible absorption. AmB short-term activity against Candida albicans (K+ leakage) was found to be correlated with the amount of free AmB released from lipid preparations. These data seem to indicate that lipid composition influences anti-Candida albicans activity, by modulation of AmB binding to lipids.

Amphotericin B↗
PubMed1988

[Ambulatory ocular surgery].

Out-patient ocular surgery exists in numerous countries and is currently making its debut in France. The authors note, from a series of 286 out-patients lens implantation operations, that the rate of complications does not significantly differ from that of in-patient procedures. These figures corroborate the results published in the United-States. The procedures applies only to motivated patients in good health and non-handicapped who well understand instructions. The selection of patients is done with the concurrence of the anesthesiologist. The anesthesia is local, occasionally preceded by a suitable sedative. The procedure takes place in an adapted surgical center of which there are several types. The check-out of the patient is within one to four hours after the operation. The constraints posed by equipment and facilities are significant since the responsibility dwells at all times with the surgeon. Caution must be exercised in all phases. The economic advantages of out-patient ocular surgery are not obvious in the current managerial context all the more so because the investment (in equipment and facilities) is costly. Nonetheless, a desired positive secondary effect would be the freeing of hospital beds for other uses. As a parallel, out-patient ocular surgery responds to a new patients demand to be treated rapidly and in an up-to-date manner (both medically and in terms of reception, waiting periods and check-out). The quality of the all procedure is increased.

Ambulatory Surgical Procedures↗
PubMed1986

[Treatment of senile macular degeneration with Ginkgo biloba extract. A preliminary double-blind drug vs. placebo study].

Senile macular degeneration is a frequent cause of blindness for which there is no satisfactory medical treatment. A double-blind trial comparing Ginkgo biloba extract with a placebo was conducted in 10 out-patients at the Hôpital Foch. Drug effectiveness was assessed on the results of fundoscopy and of measurements of visual acuity and visual field. In spite of the small population sample, a statistically significant improvement in long distance visual acuity was observed after treatment with Ginkgo biloba extract. The assumed pathogenesis of senile macular degeneration is discussed with emphasis on free oxygenated radicals.

Aged↗
PubMed1984

[Combined operation: cataract and glaucoma with implantation. Results of a series of 28 cases].

28 eyes underwent a combined procedure: trabeculectomy, extra-capsular cataract extraction and implantation of a posterior chamber intraocular lens. With a minimum of 9 months follow-up, 23 eyes had intraocular pressure controlled of all antiglaucoma medications, and 4 additional eyes achieved control with only the use of timolol maleate drops. (1 eye was lost to follow-up.) Preoperative near visual acuity was less than Parinaud 5 (Jaeger 7) in all eyes. Post-operative near visual acuity was Parinaud 2 (Jaeger 1) in 17 eyes. Senile macular degeneration was responsible for less than Parinaud 2 visual acuity in 4 additional eyes. An extracapsular extraction has advantages over the intracapsular method, both in terms of less post-operative vitreoretinal complications for the cataract extraction itself, and for the creation of a functional trabeculectomy by keeping the vitreous away from the filtration site. Use of a posterior chamber intraocular lens implant as part of the combined procedure appears to be highly acceptable. Complications and limits of the combined procedure are discussed.

Aged↗
PubMedDate not supplied

Sensitivity of transient evoked and distortion product otoacoustic emissions to the direct effects of noise on the human cochlea.

Measurement of otoacoustic emissions (OAEs) has been proposed as a sensitive test to reliably assess the effects of noise exposure. The present study in humans was designed to evaluate the sensitivity and applicability of transient evoked OAEs (TEOAEs) and 2f1-f2 distortion product OAEs (DPOAEs) as quantitative indices of the functional integrity of the outer hair cells (OHC) during growth of and recovery from temporary threshold shift (TTS). This was examined in two different groups of volunteers by measuring the per- and post-stimulatory effects of a one hour BBN and an on-site five hour exposure to loud music from a discotheque. The results of both experiments show consistent growth and recovery patterns for both DPOAEs and TEOAEs. For TEOAEs, both the reproducibility scores and signal to noise ratio values for the 4 kHz frequency band exhibited the greatest sensitivity. The DPOAEs, on the other hand, showed the greatest sensitivity between 2 and 5.5 kHz. Thus, both the TEOAEs and DPOAEs have a great potential in the detection of TTS after noise exposure.

Adult↗