Intersubband Polariton-Polariton Scattering in a Dispersive Microcavity.

The ultrafast scattering dynamics of intersubband polaritons in dispersive cavities embedding GaAs/AlGaAs quantum wells are studied directly within their band structure using a noncollinear pump-probe geometry with phase-stable midinfrared pulses. Selective excitation of the lower polariton at a frequency of ∼25 THz and at a finite in-plane momentum k_{‖} leads to the emergence of a narrowband maximum in the probe reflectivity at k_{‖}=0. A quantum mechanical model identifies the underlying microscopic process as stimulated coherent polariton-polariton scattering. These results mark an important milestone toward quantum control and bosonic lasing in custom-tailored polaritonic systems in the mid and far infrared.

Realization of Harmonic Oscillator Arrays with Graded Semiconductor Quantum Wells.

The harmonic oscillator is a foundational concept in both theoretical and experimental quantum mechanics. Here, we demonstrate harmonic oscillators in a semiconductor platform by faithfully implementing continuously graded alloy semiconductor quantum wells. Unlike current technology, this technique avoids interfaces that can hamper the system and allows for the production of multiwell stacks several micrometers thick. The experimentally measured system oscillations are at 3 THz for two structures containing 18 and 54 parabolic quantum wells. Absorption at room temperature is achieved: this is as expected from a parabolic potential and is unlike square quantum wells that require cryogenic operation. Linewidths below 11% of the central frequency are obtained up to 150 K, with a 5.6% linewidth obtained at 10 K. Furthermore, we show that the system correctly displays an absence of nonlinearity despite electron-electron interactions-analogous to the Kohn theorem. These high-quality structures already open up several new experimental vistas.

Analyte capture in an array of functionalized droplets for a regenerable biosensor.

We describe in this work an advanced microfluidic chip for the capture of bioanalyte on the surface of droplets arranged in a dense array. We show the procedure for generating, functionalizing, and arranging the droplets inside the device for capturing a specific bioanalyte. Then, we demonstrate the capacity of the array to capture analyte from a cross-flowing liquid, using a biotin/streptavidin model. The paper also proposes to use the droplets array, after integration with acoustic detection, as a regenerable detection interface for bioanalyte sensing. We model the arrangement of droplet in dense array and show that they present a larger effective capture surface and shorter capture distance than standard flat surface biosensor of the same footprint. As the droplets can be easily evacuated and replaced inside the device analysis chamber, the proposed biosensor would allow biointerface regeneration and chain measurement without dismounting the device.

Circuit-tunable sub-wavelength THz resonators: hybridizing optical cavities and loop antennas.

We demonstrate subwavelength electromagnetic resonators operating in the THz spectral range, whose spectral properties and spatial/angular patterns can be engineered in a similar way to an electronic circuit. We discuss the device concept, and we experimentally study the tuning of the resonant frequency as a function of variable capacitances and inductances. We then elucidate the optical coupling properties. The radiation pattern, obtained by angle-resolved reflectance, reveals that the system mainly couples to the outside world via a magnetic dipolar interaction.

Improving immunosensor performances using an acoustic mixer on droplet microarray.

A major drawback of protein microarrays is the lack of control of ligand immobilization at the surface of the chip which limits their performances and thus their impacts in in vitro diagnosis. To improve antibody (Ab) grafting during the spotting process on commercialized gold SPRi chips, we propose to produce a chaotic flow in every spotted droplet, by using an acoustic field, in order to disrupt the steady state of the reaction of Ab grafting. Our results show that acoustic mixing during Ab binding at the biochips surface increases their biorecognition performances of a mean factor of 2.7 in comparison with Ab layer grafted in a passive mode. Moreover, it increases statistically the homogeneity of the response over all the surface of the chips.

Strong terahertz emission enhancement via femtosecond laser filament concatenation in air.

We investigate the emission of terahertz (THz) radiation from two laser filaments in air. An increase by 1 order of magnitude of the overall THz power is found when the two filaments are coherently linked on-axis, leading to a single longer concatenated filament. The observed enhancement is found to be the same for the cases of single-color and two-color filamentation approaches.

Terahertz pulse emission optimization from tailored femtosecond laser pulse filamentation in air.

We study the generation of intense terahertz pulses produced by two-color laser pulse filamentation in air. We tailor the filamentation process and the produced plasma strings and study how the generated terahertz field is modified. An important terahertz pulse shortening is found for plasma strings with uniform electron density.

Sensitivity of a Lamb wave sensor with 2 microm AlN membrane.

Anti-symmetrical Lamb wave mode A0 presents a large sensitivity to mass loading and can be used in contact with liquids with a small attenuation. The advantages of this system are the possibility to get a large mass sensitivity. The sensitivity increases when the thickness of membrane decreases. Therefore the problem is to obtain thin piezoelectric membranes. A membrane of AlN with a thickness of 2 microm has been made. The measured mass sensitivity with a fluid is 200 cm(2) g(-1). In a practical use point of view, the problem in this kind of sensor is its temperature sensitivity. In order to reduce effective temperature sensitivity, a device with thin metallic strips is presented. On the same membrane two different waves with perpendicular propagating directions are produced. Experimentally, temperature sensitivity is rather different depending on the propagation direction but mass sensitivity is almost the same, this allows distinguishing temperature effects from those due to mass loading on the frequency shift measurements.

Action of low frequency vibration on liquid droplets and particles.

Liquids handling is an important issue in biomedical analysis. Two different devices for acoustic manipulation of droplets have already been tested. The first one, more classical, uses a high frequency travelling wave and acoustic streaming. The second one uses low frequency flexural standing waves in a plate. This means of liquid handling is original and easy to implement but the physical principle is not obvious. In order to understand more precisely the phenomena involved we present new observations on droplet displacement between two planes and on the behaviour of a droplet on an inclined vibrating plane with this method. The physical principle involved is discussed. The common acoustic radiation pressure formulation is expressed via the non-linear theory of sound propagation, but in our case the acoustic wavelength is much smaller than the height of a water droplet. To get a better understanding of the phenomenon, further experiments on the internal liquid flow and behaviour of particles in the droplet have been performed. These will be compared with results obtained with particles in a thin water-filled vibrating glass tube. The general conclusion is that the phenomenon is practical to use for droplet displacement even if its complex mechanism is not completely understood.

Targeting of diethylene triamine pentaacetic acid encapsulated in liposomes to rat liver: an effective strategy to prevent bone deposition and increase urine elimination of plutonium in rats.

PURPOSE: To modify the distribution of the chelating agent diethylene triamine pentaacetic acid (DTPA) by using a formulation approach with liposomes in order to match the in vivo distribution of plutonium (Pu) and, as a consequence, to improve actinide decorporation. MATERIALS AND METHODS: DTPA was encapsulated in conventional and stealth liposomes. Their pharmacokinetics and ability to remove Pu were evaluated in rats 2 and 16 days after a single intravenous treatment given 2 h after contamination with colloidal Pu (239Pu phytate) or with soluble Pu (238Pu citrate). RESULTS: Both formulations induced major pharmacokinetic modifications in rats, allowing an accumulation of [14C]-DTPA mainly in the liver and secondarily (for stealth liposomes) in bone and spleen. These modifications were associated with major increases in urine elimination and with a decrease in skeletal Pu deposition, depending of the nature of the Pu contaminant. After contamination by Pu phytate, conventional liposomes of DTPA (6 micromol kg(-1)) were as efficient as free DTPA (30 micromol kg(-1)) in maintaining the Pu content in the femur below 4.3% of the injected dose after 16 days, a 3.6-fold reduction compared with free DTPA (4 micromol kg(-1)) treatment or without treatment. CONCLUSIONS: A formulation approach with liposomes appears to be a powerful tool to improve the efficiency of Pu chelating agents in vivo.

Displacement of droplets and deformation of thin liquid layers using flexural vibrations of structures. Influence of acoustic radiation pressure.

In this paper observations concerning some effects of vibrating structures on fluids are presented, followed by a tentative theoretical analysis. First, a brief description of a caterpillar-like structure is made. This structure is almost equivalent to an infinite beam which allows the choice of positions of the nodal lines of a vibrating mode. Displacement of liquid droplets using switching between two modes of this structure is then presented. This phenomenon is supposed to be induced by acoustic radiation pressure. Possible extensions of this principle are then discussed. After this, results are reported concerning deformations of thin liquid layers.

Simultaneous determination of enrofloxacin and ciprofloxacin in animal biological fluids by high-performance liquid chromatography. Application in pharmacokinetic studies in pig and rabbit.

A simple and rapid high-performance liquid chromatographic method for the simultaneous determination of enrofloxacin and ciprofloxacin has been developed in pig and rabbit samples. Solid-phase extraction was applied from samples on a C18 cartridge using a mixture of methanol-hydrochloric acid (98:2, v/v). Analytical separation was performed on a C18 column with UV detection at 277 nm under gradient conditions. The mobile phase was a mixture of orthophosphoric acidtriethylamine-acetonitrile. The method has been validated for both molecules in pig and rabbit plasma and adapted for rabbit tissue-cage fluid (TCF). The assay is specific and reproducible within the both drugs and mean recoveries for ciprofloxacin and enrofloxacin, respectively, were 92+/-6% and 90+/-5% for pig plasma over the range used. Mean recoveries for enrofloxacin were 108+/-9% and 102+/-7% for rabbit plasma and TCF, respectively, over the range used. The suitability of the assay for pharmacokinetic studies was determined by measuring enrofloxacin and ciprofloxacin concentrations either in pig plasma after administration of a single intravenous 5 mg/kg dose of enrofloxacin or in rabbit plasma and TCF during a 24 h infusion of enrofloxacin at a rate of 1.25 mg/kg per hour.

Costo-eficacia de las estrategias de vacunación en servicios ordinarios y en campañas en el Ecuador / Cost-effectiveness of routine and campaing vaccination strategies in Ecuador

En julio de 1986 se realizó una encuesta domiciliaria nacional sobre cobertura de vacunación de 3 697 niños ecuatorianos, que brindó la oportunidad de realizar un análisis de costo-eficacia de (1) los servicios de vacunación ordinarios en establecimientos fijos (2) de las campañas de inmunización en masa. Una de las principales finalidades de las campañas fue complementar los servicios de vacunación ordinarios y acelerar las actividades de inmunización. Basándose en la encuesta de la cobertura, el Programa para la Reduccion de la Enfermedad Maternoinfantil (PREMI) y varias campañas anteriores aumentaron la proporción de niños menores de cinco años completamente vacunados de 43 a 64 por ciento. En un año, la campaña del PREMI se encargó de vacunar completamente a 11 por ciento de los niños menores de un año, 21 por ciento de los de 1 a 2 años y 13 por ciento de todos los menores de 5 años. La campaña también ayudó a completar el programa de vacunación cuando los niños eran todavía muy pequeños y estaban expuestos al máximo riesgo. El costo medio por dosis de vacuna (en $US de 1985) fue aproximadamente de $0,29 en los establecimientos fijos y de $0,83 en la campaña del PREMI. El total de los costos nacionales fue de $675 000 y de 1 665 000 en los servicios de vacunación ordinarios y en las campañas, respectivamente. El costo por niño completamente vacunado fue de $44,39 en los primeros y de $8,60 en las últimas. El costo de cada defunción evitada fue de unos $1 900 en los servicios de vacunación ordinarios, de $4 200 en la campaña del PREMI y de $3 200 en el programa combinado. A causa de las menores tasas de mortalidad del Ecuador, los costos por cada defunción evitada en ese país con ambas estrategias no son tan bajos como los observados en estudios pertinentes efectuados en Africa. Las campañas, pese a ser menos eficaces en función del costo que los servicios de vacunación ordinarios, mejoraron significativamente la cobertura de vacunación de los niños menores que no habían sido vacunados en los servicios ordinarios. Al comparar los costos por niño completamente vacunado en ambos servicios con los de programas similares en otros países, los resultados fueron favorables

Costo-eficacia de las estrategias de vacunación en servicios ordinarios y en campañas en el Ecuador / Cost-effectiveness of routine and campaing vaccination strategies in Ecuador

En julio de 1986 se realizó una encuesta domiciliaria nacional sobre cobertura de vacunación de 3 697 niños ecuatorianos, que brindó la oportunidad de realizar un análisis de costo-eficacia de (1) los servicios de vacunación ordinarios en establecimientos fijos (2) de las campañas de inmunización en masa. Una de las principales finalidades de las campañas fue complementar los servicios de vacunación ordinarios y acelerar las actividades de inmunización. Basándose en la encuesta de la cobertura, el Programa para la Reduccion de la Enfermedad Maternoinfantil (PREMI) y varias campañas anteriores aumentaron la proporción de niños menores de cinco años completamente vacunados de 43 a 64 por ciento. En un año, la campaña del PREMI se encargó de vacunar completamente a 11 por ciento de los niños menores de un año, 21 por ciento de los de 1 a 2 años y 13 por ciento de todos los menores de 5 años. La campaña también ayudó a completar el programa de vacunación cuando los niños eran todavía muy pequeños y estaban expuestos al máximo riesgo. El costo medio por dosis de vacuna (en $US de 1985) fue aproximadamente de $0,29 en los establecimientos fijos y de $0,83 en la campaña del PREMI. El total de los costos nacionales fue de $675 000 y de 1 665 000 en los servicios de vacunación ordinarios y en las campañas, respectivamente. El costo por niño completamente vacunado fue de $44,39 en los primeros y de $8,60 en las últimas. El costo de cada defunción evitada fue de unos $1 900 en los servicios de vacunación ordinarios, de $4 200 en la campaña del PREMI y de $3 200 en el programa combinado. A causa de las menores tasas de mortalidad del Ecuador, los costos por cada defunción evitada en ese país con ambas estrategias no son tan bajos como los observados en estudios pertinentes efectuados en Africa. Las campañas, pese a ser menos eficaces en función del costo que los servicios de vacunación ordinarios, mejoraron significativamente la cobertura de vacunación de los niños menores que no habían sido vacunados en los servicios ordinarios. Al comparar los costos por niño completamente vacunado en ambos servicios con los de programas similares en otros países, los resultados fueron favorables

Disponible en inglés en: Bull. WHO 67(6), 1989

Cost-effectiveness of routine and campaign vaccination strategies in Ecuador.

A national household coverage survey of 3697 Ecuadorean children, carried out in July 1986, provided an opportunity for a cost-effectiveness analysis of (1) routine vaccination services based in fixed facilities and (2) mass immunization campaigns. A major purpose of the campaigns was to complement the routine services and to accelerate immunization activities. Based on the coverage survey, the Program for Reduction of Maternal and Childhood Illness (PREMI) and earlier campaigns increased the proportion of children under 5 years who were fully vaccinated from 43% to 64%. In one year, the PREMI campaign was responsible for fully vaccinating 11% of children under one year, 21% of 1-2-year-old children, and 13% of all children under 5 years. The campaign also helped ensure that vaccinations were completed when children were still very young and at greatest risk. The average cost per vaccination dose (in 1985 US$ prices) was approximately $0.29 for fixed facilities and $0.83 for the PREMI campaign. Total national costs were $675,000 and $1,665,000 for routine and campaign services respectively. The cost per fully vaccinated child (FVC) was $4.39 for routine vaccination services and $8.60 for the campaign. The cost per death averted was about $1900 for routine vaccination services, $4200 for the PREMI campaign, and $3200 for the combined programme. Because of Ecuador's lower mortality rates, the costs per death averted in Ecuador from both vaccination strategies are not as low as those from studies of vaccinations in Africa. The campaigns, though less cost-effective than routine services, significantly improved the vaccination coverage of younger children who had been missed by the routine services. The costs per FVC of both the campaign and the routine services compare favourably with such programmes in other countries.

Cost-effectiveness of routine and campaign vaccination strategies in Ecuador

A national household coverage survey of 3697 Ecuadorean children, carried out in July 1986, provided an opportunity for a cost-effectiveness analysis of (1) routine vaccination services based in fixed facilities and (2) mass immunization campaigns. A major purpose of the campaigns was to complement the routine services and to accelerate immunization activities. Based on the coverage survey, the Program for Reduction of Maternal and Childhood Illness (PREMI) and earlier campaigns increased the proportion of children under 5 years who were fully vaccinated from 43 per cent to 64 per cent. In one year, the PREMI campaign was responsible for fully vaccinating 11 per cent of children under one year, 21 per cent of 1-2-year-old children, and 13 per cent of all children under 5 years. The campaign also helped ensure that vaccinations were completed when children were still very young and at greatest risk

The average cost per vaccination dose (in 1985 US$ prices) was approximately $0.20 for fixed facilities and $0.83 for the PREMI campaign. Total national costs were $675,000 and $1,665,000 for routine and campaign services respectively. The cost por fully vaccinated child (FVC) was $4.39 for routine vaccination services and $8.60 for the campaign. The cost per death avered was about $1,900 for routine vaccination services ...(AU)