Periodic Modulation of Extraordinary Optical Transmission through Subwavelength Hole Arrays using Surrounding Bragg Mirrors

The enhanced light transmission through an array of subwavelength holes surrounded by Bragg mirrors is studied, showing that the mirrors act to confine the surface plasmons associated with the Extraordinary Optical Transmission effect, forming a surface resonant cavity. The overall effect is increased light transmission intensity by more than a factor of three beyond the already enhanced transmission, independent of whether the Bragg mirrors are on the input or the output side of the incident light. The geometry of the Bragg mirror structures controls the enhancement, and can even reduce the transmission in half. By varying these geometric parameters, we were able to periodically modulate the transmission of light for specific wavelengths, consistent with the propagation and interference of surface plasmon waves in a resonant cavity. FDTD simulations and a wave propagation model verify this effect.Comment: 9 pages, 5 figure

Nonlinear optical properties of interconnected gold nanoparticles on silicon

International audienceWe report second harmonic generation (SHG) measurements in reflectivity from chains of gold nanoparticles interconnected with metallic bridges. We measured more than 30 times a SHG enhancement when a surface plasmon resonance was excited in the chains of nanoparticles, which was influenced by coupling due to the electrical connectivity of the bridges. This enhancement was confirmed by rigorous coupled wave method calculations and came from high localization of the electric field at the bridge. The introduction of 10% random defects into the chains of nanoparticles dropped the SHG by a factor of 2 and was shown to be very sensitive to the fundamental wavelengt

Chemical Science Membrane protein biosensing with plasmonic nanopore arrays and pore-spanning lipid membranes †

Integration of solid-state biosensors and lipid bilayer membranes is important for membrane protein research and drug discovery. In these sensors, it is critical that the solid-state sensing material does not have adverse effects on the conformation or functionality of membrane-bound molecules. In this work, pore-spanning lipid membranes are formed over an array of periodic nanopores in free-standing gold films for surface plasmon resonance (SPR) kinetic binding assays. The ability to perform kinetic assays with a transmembrane protein is demonstrated with a-hemolysin (a-HL). The incorporation of a-HL into the membrane followed by specific antibody binding (anti-a-HL) red-shifts the plasmon resonance of the gold nanopore array, which is optically monitored in real time. Subsequent fluorescence imaging reveals that the antibodies primarily bind in nanopore regions, indicating that a-HL incorporation preferentially occurs into areas of pore-spanning lipid membranes

Propriétés optiques linéaires et non linéaires de réseaux de nanostructures sub-longueurs d'onde en or

Les plasmons de surface sont des modes propres d'interface metal/diélectrique présentant un fort couplage entre les électrons libres et le champ électromagnétique. Ces plasmons peuvent être localisés sur des petites particules (sphères, cylindres, agrégat), se propager sur des interfaces planes ou rugueuses ou être guidés par des guides métalliques. Dans le cadre de ma thèse, j'ai étudié deux types de structures : des réseaux de particules sub-longueurs d'onde fortement couplées en or sur silicium et des tamis à photons permettant une forte exaltation de la transmission.Par des mesures de réflectivité optique linéaire spectroscopique sous angle d'incidence variable sur des réseaux de chaînes de particules sub-longueurs d'onde, nous avons pu mettre en évidence des résonances liées au réseau (anomalie de Wood) et surtout des résonances de plasmons de surface localisés capables de se propager le long d'une chaîne de particules sub-longueurs d'onde fortement couplées par une faible distance interparticules et par une interconnexion métallique. Mes résultats sont en accord avec les calculs RCWM que nous avons effectués. Par ailleurs, j'ai mis en évidence la grande sensibilité du doublage de fréquence à l'exaltation du champ électromagnétique local à la résonance et du au couplage entre les particules.Nous avons également réalisé des réseaux d'ouvertures circulaires sub-longueurs d'onde présentant une transmission de 10%. Par ailleurs, nous avons fabriqué des réseaux de nanocavités coaxiales. Nous avons mis en évidence expérimentalement l'existence d'un plasmon de surface or/verre et d'un mode de cavité pouvant théoriquement permettre une transmission exaltée.Surface plasmons are egen modes of metallic interfaces resulting from a strong coupling between an incident electromagnetic wave and the free electrons of the metal. These plasmons can be localized on very small particles (spheres, cylinders, agregates...). They can propagate along smooth or rough interfaces and they can be guided by metallic stripes. In the context of my thesis, I have studied two kinds of such metallic structures : gold coupled sub-wavelength particle regular arrays and arrays of subwavelength apertures permitting a enhanced transmission through a so structured metallic film.Through linear optical spectroscopic reflectivity measurements, on arrays of gold subwavelength particle, we have measured the signatures of grating effects (Wood anomalies) and especially propagating localized lurface llasmons along a chain of gold subwavelength particles by a narrow spacing between particles and by a metallic neck connecting particles. My experimental results are in good agreement with the RCWM calculations we did. Furthermore, I shew the high sensitivity of the Second Harmonic Generation measurements to the enhancement of the local electromagnetic fields due to the resonances and the coupling between particles. Subwavelength circular aperture arrays were made in a 100 nm gold film and we measured a 10% transmission. Moreover, subwavelength annular aperture arrays in a 130 nm gold film were fabricated. We measured by reflectivity the spectral signature of a surface plasmon at the gold/glass interface and a cavity mode which are responsible of the theoritical enhanced transmission.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Underuse of primary healthcare in France during the COVID-19 epidemic in 2020 according to individual characteristics: a national observational study

International audienceBackground: The organization of healthcare systems changed significantly during the COVID-19 pandemic. The impact on the use of primary care during various key periods in 2020 has been little studied. Methods: Using individual data from the national health database, we compared the numbers of people with at least one consultation, deaths, the total number of consultations for the population of mainland France (64.3 million) and the mean number of consultations per person (differentiating between teleconsultations and consultations in person) between 2019 and 2020. We performed analyses by week, by lockdown period (March 17 to May 10, and October 30 to December 14 [less strict]), and for the entire year. Analyses were stratified for age, sex, deprivation index, epidemic level, and disease. Results: During the first lockdown, 26% of the population consulted a general practitioner (GP) at least once (-34% relative to 2019), 7.4% consulted a nurse (-28%), 1.6% a physiotherapist (-80%), and 5% a dentist (-95%). For specialists, consultations were down 82% for ophthalmologists and 37% for psychiatrists. The deficit was smaller for specialties making significant use of teleconsultations. During the second lockdown, the number of consultations was close to that in 2019, except for GPs (-7%), pediatricians (-8%), and nurses (+ 39%). Nurses had already seen a smaller increase in weekly consultations during the summer, following their authorization to perform COVID-19 screening tests. The decrease in the annual number of consultations was largest for dentists (-17%), physiotherapists (-14%), and many specialists (approximately 10%). The mean number of consultations per person was slightly lower for the various specialties, particularly for nurses (15.1 vs. 18.6). The decrease in the number of consultations was largest for children and adolescents (GPs:-10%, dentists:-13%). A smaller decrease was observed for patients with chronic diseases and with increasing age. There were 9% excess deaths, mostly in individuals over 60 years of age. Conclusions: There was a marked decrease in primary care consultations in France, especially during the first lockdown, despite strong teleconsultation activity, with differences according to age and healthcare profession. The impact of this decrease in care on morbidity and mortality merits further investigation

Acceptability of Second-Line Antidepressant Medications Using Filled Prescription Sequences in a Nationwide Cohort Study

International audienceBackground: Although about half of patients do not respond to a first-line antidepressant medication, there is no consensus on the best second-line option. The aim of this nationwide population-based study was to rank antidepressants according to their relative acceptability (ie, efficacy and tolerability) using filled prescription sequences after failure of first treatment. Methods: About 1.2 million people were identified as new antidepressant users in the French national health data system in 2011. The inclusion criterion was having at least 2 filled prescriptions of a second-line treatment after a filled prescription of a first-line treatment, resulting in 63,726 participants. The outcome was clinical acceptability as measured by the continuation/change ratio for second-line treatment. Continuation sequence was defined as at least 2 refills of the same treatment. Change sequence was defined as at least 1 filled prescription of another antidepressant. Adjusted odds ratios (aORs) were computed through multivariable binary logistic regressions. Results: Intraclass switch had a better acceptability than interclass switch (aOR [95% CI]: 1.23 [1.20-1.28]). According to the first-line treatment, intraclass switch remained more acceptable for selective serotonin reuptake inhibitors only (1.37 [1.31-1.42]). For α2 blockers and tricyclic agents, combination antidepressant therapy was the most acceptable second-line option (1.59 [1.27-2.01] and 2.53 [1.53-4.04], respectively), whereas for serotonin-norepinephrine reuptake inhibitors there was no significant difference between the strategies. For other antidepressants, intraclass switch had lower acceptability than interclass switch (0.70 [0.51-0.95]). Conclusions: Administrative claim databases may help with ranking acceptability of second-line treatments in real world settings and complement randomized controlled trials in informing clinicians about the most acceptable second-line options according to the first-line treatment

Cellular asymmetric catalysis by UDP-glucuronosyltransferase 1A8 shows functional localization to the basolateral plasma membrane.

UDP-glucuronosyltransferases (UGTs) are highly expressed in liver, intestine and kidney and catalyze the glucuronic acid conjugation of both endogenous compounds and xenobiotics. Using recombinant human UGT isoforms, we show that glucuronic acid conjugation of the model substrate, (-)-epicatechin, is catalyzed mainly by UGT1A8 and UGT1A9. In HepG2 cells, pre-treatment with polyunsaturated fatty acids increased substrate glucuronidation. In the intestinal Caco-2/HT29-MTX co-culture model, overall relative glucuronidation rates were much higher than in HepG2 cells and (-)-epicatechin was much more readily conjugated when applied to the basolateral side of the cell monolayer. Under these conditions, 95% of the conjugated product was effluxed back to the site of application and none of the other phase 2-derived metabolites followed this distribution pattern. HT29-MTX cells contained >1000-fold higher levels of UGT1A8 mRNA than Caco-2 or HepG2 cells. Gene expression of UGT1A8 increased after treatment of cells with docosahexaenoic acid, as did UGT1A protein levels. Immunofluorescence staining and western blotting showed the presence of UGT1A in basal and lateral parts of the plasma membrane of HT29-MTX cells. These results suggest that in HT29-MTX goblet cells at least some of the UGT1A8 enzyme is not endoplasmic reticulum resident but plasma membrane spanning, resulting in much more efficient conjugation of substrate from the basal than from the luminal side, coupled with rapid efflux by functionally-associated basolateral transporters. This novel molecular strategy allows the cell to carry out conjugation without the xenobiotic entering into the interior of the cell