Impact of γ-rays Irradiation on Hybrid TiO2-SiO2 Sol-Gel Films Doped with RHODAMINE 6G.

In the present paper, we investigate how the optical and structural properties, in particular the observed photoluminescence (PL) of photocurable and organic-inorganic TiO2-SiO2 sol-gel films doped with Rhodamine 6G (R6G) are affected by γ-rays. For this, four luminescent films, firstly polymerized with UV photons (365 nm), were submitted to different accumulated doses of 50 kGy, 200 kGy, 500 kGy and 1 MGy while one sample was kept as a reference and unirradiated. The PL, recorded under excitations at 365 nm, 442 nm and 488 nm clearly evidences that a strong signal peaking at 564 nm is still largely present in the γ-irradiated samples. In addition, M-lines and Fourier-transform infrared (FTIR) spectroscopies are used to quantify the radiation induced refractive index variation and the chemical changes, respectively. Results show that a refractive index decrease of 7 × 10-3 at 633 nm is achieved at a 1 MGy accumulated dose while a photo-induced polymerization occurs, related to the consumption of CH=C, Si-OH and Si-O-CH3 groups to form Ti-O and Si-O bonds. All these results confirm that the host matrix (TiO2-SiO2) and R6G fluorophores successfully withstand the hard γ-ray exposure, opening the way to the use of this material for sensing applications in radiation-rich environments.

Comparison between the UV and X-ray Photosensitivities of Hybrid TiO2-SiO2 Thin Layers.

The photo-induced effects on sol-gel-based organo TiO2-SiO2 thin layers deposited by the dip-coating technique have been investigated using two very different light sources: A light-emitting diode (LED) emitting in the UV (at 365 nm, 3.4 eV) and an X-ray tube producing 40 keV mean-energy photons. The impact of adding a photo-initiator (2,2-dimethoxy-2-phenylacetophenone-DMPA) on the sol-gel photosensitivity is characterized namely in terms of the photo-induced refractive index measured through M-line spectroscopy. Results show that both silica-titania sol-gel films with or without the photo-initiator are photosensitive to both photon sources. The induced refractive index values reveal several features where slightly higher refractive indexes are obtained for the sol-gel containing the photo-initiator. UV and X-ray-induced polymerization degrees are discussed using Fourier-transform infrared (FTIR) spectroscopy where the densification of hybrid TiO2-SiO2 layers is related to the consumption of the CH=C groups and to the decomposition of Si-OH and Si-O-CH3 bonds. X-rays are more efficient at densifying the TiO2-SiO2 inorganic and organic network with respect to the UV photons. Hard X-ray photolithography, where no cracks or damages are observed after intense exposition, can be a promising technique to design submicronic-structure patterns on TiO2-SiO2 thin layers for the building of optical sensors.

Longitudinal magneto-optical effect enhancement with high transmission through a 1D all-dielectric resonant guided mode grating.

A significant enhancement of the longitudinal magneto-optical effect is demonstrated numerically and experimentally in transmission, and for small angles of incidence, through a subwavelength resonant structure consisting of a dielectric grating on top of a magneto-optical waveguide. The enhanced polarization rotation is associated with a high transmittance. These low footprint devices may thus be suitable for applications like magnetic field sensors or in non-destructive testing.

Enhancement of Both Faraday and Kerr Effects with an All-Dielectric Grating Based on a Magneto-Optical Nanocomposite Material.

We report on the design, fabrication, and characterization of an all-dielectric one-dimensional (1D) resonant device formed by a silicon nitride grating impregnated by a low-index magneto-optical silica-type matrix. This impregnation is realized through the dipping of the 966 nm periodic template in a sol-gel solution previously doped with CoFe2O4 nanoparticles, and able to fill the grating slits. By a proper adjustment of the geometrical parameters of such a photonic crystal membrane, simultaneous excitation of transverse electric (TE) and transverse magnetic (TM) polarization resonances is nearly achieved at 1570 nm. This TE/TM phase-matching situation leads to a fivefold enhancement of the Faraday effect in the resonance area with an increased merit factor of 0.32°. Moreover, the device demonstrates its ability to enhance longitudinal and transverse Kerr effects for the other directions of the applied magnetic field. Taking benefits from the ability of the nanocomposite material to be processed on photonic platforms, and despite its quite low magneto-optical activity compared to classical magnetic materials, this work proves that an all-dielectric 1D device can produce a high magneto-optical sensitivity to every magnetic field directions.

Seasonal distributions and migrations of Northwest Atlantic swordfish: inferences from integration of pop-up satellite archival tagging studies.

Data sets from three laboratories conducting studies of movements and migrations of Atlantic swordfish (Xiphias gladius) using pop-up satellite archival tags were pooled, and processed using a common methodology. From 78 available deployments, 38 were selected for detailed examination based on deployment duration. The points of deployment ranged from southern Newfoundland to the Straits of Florida. The aggregate data comprise the most comprehensive information describing migrations of swordfish in the Atlantic. Challenges in using data from different tag manufacturers are discussed. The relative utility of geolocations obtained with light is compared with results derived from temperature information for this deep-diving species. The results show that fish tagged off North America remain in the western Atlantic throughout their deployments. This is inconsistent with the model of stock structure used in assessments conducted by the International Commission for the Conservation of Atlantic Tunas, which assumes that fish mix freely throughout the North Atlantic.

Meta-analytic findings of the relation between maternal prenatal stress and anxiety and child cognitive outcome.

OBJECTIVE: Different studies have revealed mixed findings regarding the relation between maternal prenatal stress or anxiety (MPSA) and early child cognitive outcome. Different methodological considerations may be linked to the absence of clear support for this hypothesized link. The purpose of this article was to conduct a meta-analysis of this relation while considering the following as potential moderators: (1) pregnancy trimester during which MPSA was assessed, (2) type of MPSA assessment (life events, pregnancy related, subjective assessments), and (3) research design (retrospective or prospective). Other moderators were also examined: child age at assessment and the year of publication. METHOD: Eleven studies were identified (N = 5903) that examined the relation between MPSA and early child cognitive outcome. RESULTS: A small effect size of r = -.05 was found for this relation. The effect size varied across studies and was significantly moderated by the manner in which MPSA was operationalized (events, subjective assessment of stress or pregnancy-related stress or anxiety) and by whether MPSA assessment took place before or after infant birth. Greater relations to child cognitive outcome were found for postnatal event-based indicators of MPSA. CONCLUSION: The relation between MPSA and child cognitive outcome seems to be present, but low. Moreover, it is affected by the specific choices made by researchers in the manner in which constructs are operationalized.

Foraging in the darkness of the Southern Ocean: influence of bioluminescence on a deep diving predator.

How non-echolocating deep diving marine predators locate their prey while foraging remains mostly unknown. Female southern elephant seals (SES) (Mirounga leonina) have vision adapted to low intensity light with a peak sensitivity at 485 nm. This matches the wavelength of bioluminescence produced by a large range of marine organisms including myctophid fish, SES's main prey. In this study, we investigated whether bioluminescence provides an accurate estimate of prey occurrence for SES. To do so, four SES were satellite-tracked during their post-breeding foraging trip and were equipped with Time-Depth-Recorders that also recorded light levels every two seconds. A total of 3386 dives were processed through a light-treatment model that detected light events higher than ambient level, i.e. bioluminescence events. The number of bioluminescence events was related to an index of foraging intensity for SES dives deep enough to avoid the influence of natural ambient light. The occurrence of bioluminescence was found to be negatively related to depth both at night and day. Foraging intensity was also positively related to bioluminescence both during day and night. This result suggests that bioluminescence likely provides SES with valuable indications of prey occurrence and might be a key element in predator-prey interactions in deep-dark marine environments.

Lost in space? Searching for directions in the spatial modelling of individuals, populations and species ranges.

The workshop 'Spatial models in animal ecology, management and conservation' held at Silwood Park (UK), 9-11 March 2010, aimed to synthesize recent progress in modelling the spatial dynamics of individuals, populations and species ranges and to provide directions for research. It brought together marine and terrestrial researchers working on spatial models at different levels of organization, using empirical as well as theory-driven approaches. Different approaches, temporal and spatial scales, and practical constraints predominate at different levels of organization and in different environments. However, there are theoretical concepts and specific methods that can fruitfully be transferred across levels and systems, including: habitat suitability characterization, movement rules, and ways of estimating uncertainty.

Accurate and rapid optical characterization of an anisotropic guided structure based on a neural method.

Optimal performances of integrated optical devices are obtained by the use of an accurate and reliable characterization method. The parameters of interest, i.e., optical indices and thickness of the waveguide structure, are calculated from effective indices by means of an inversion procedure. We demonstrate how an artificial neural network can achieve such a process. The artificial neural network used is a multilayer perceptron. The first result concerns a simulated anisotropic waveguide. The accuracy in the determination of optical indices and waveguide thickness is 5 x 10(-5) and 4 nm, respectively. Then an experimental application on a silica-titania thin film is performed. In addition, effective indices are measured by m-lines spectroscopy. Finally, a comparison with a classical optimization algorithm demonstrates the robustness of the neural method.