Modelling the covariance structure in marginal multivariate count models: Hunting in Bioko Island.

The main goal of this article is to present a flexible statistical modelling framework to deal with multivariate count data along with longitudinal and repeated measures structures. The covariance structure for each response variable is defined in terms of a covariance link function combined with a matrix linear predictor involving known matrices. In order to specify the joint covariance matrix for the multivariate response vector, the generalized Kronecker product is employed. We take into account the count nature of the data by means of the power dispersion function associated with the Poisson–Tweedie distribution. Furthermore, the score information criterion is extended for selecting the components of the matrix linear predictor. We analyse a data set consisting of prey animals (the main hunted species, the blue duiker Philantomba monticola and other taxa) shot or snared for bushmeat by 52 commercial hunters over a 33-month period in Pico Basilé, Bioko Island, Equatorial Guinea. By taking into account the severely unbalanced repeated measures and longitudinal structures induced by the hunters and a set of potential covariates (which in turn affect the mean and covariance structures), our method can be used to indicate whether there was statistical evidence of a decline in blue duikers and other species hunted during the study period. Determining whether observed drops in the number of animals hunted are indeed true is crucial to assess whether species depletion effects are taking place in exploited areas anywhere in the world. We suggest that our method can be used to more accurately understand the trajectories of animals hunted for commercial or subsistence purposes and establish clear policies to ensure sustainable hunting practices

Planar microlenses for near infrared CMOS image sensors

In this paper we present planar microlenses designed to improve the sensitivity of SPAD pixels. We designed diffractive and metasurface planar microlens structures based on rigorous optical simulations, then we implemented the diffractive microlens on a SPAD design available on STMicroelectronics 40nm CMOS testchips (32 × 32 SPAD array), and compared with the process of reference melted microlens. We characterized circuits and demonstrated optical gain from our designed microlenses (numbers to be added)

Development of an UV scanning photoluminescence apparatus for SiC characterization

We have adapted a scanning photoluminescence (SPL) apparatus, previously developed for III-V compounds analysis, for the characterization of SiC. The PL mapping is obtained by scanning the sample, fixed to an x-y stage with 1 μm minimal step, under a doubled Ar+ laser beam (244 nm) focused by a microscope objective (×52). For this excitation the spot diameter is about 4 μm. The PL signal can be either directly detected, giving integrated PL intensity, either dispersed using a monochromator, giving spectrally resolved PL (1 nm resolution). The measurements can be realized at room temperature for near band edge studies, or at low temperature (80 K) for deep defects investigation. The gettering effect of non radiative centres by the screw dislocations in 6H-SiC is evidenced using this apparatus

Properties of nitrogen doped silicon films deposited by low-pressure chemical vapor deposition from silane and ammonia

Nitrogen doped silicon (NIDOS) films have been deposited by low-pressure chemical vapor deposition from silane SiH4 and ammonia NH3 at high temperature (750°C) and the influences of the NH3/SiH4 gas ratio on the films deposition rate, refractive index, stoichiometry, microstructure, electrical conductivity, and thermomechanical stress are studied. The chemical species derived from silylene SiH2 into the gaseous phase are shown to be responsible for the deposition of NIDOS and/or (silicon rich) silicon nitride. The competition between these two deposition phenomena leads finally to very high deposition rates (100 nm/min) for low NH3/SiH4 gas ratio (R¿0.1). Moreover, complex variations of NIDOS film properties are evidenced and related to the dual behavior of the nitrogen atom into silicon, either n-type substitutional impurity or insulative intersticial impurity, according to the Si¿N atomic bound. Finally, the use of NIDOS deposition for the realization of microelectromechanical systems is investigated

Transmission measurements of multilayer interference filters developed for a full integration on Complementary Metal Oxide Semiconductor chips

International audienceWe present in this paper a method to measure the transmission spectra of optical filters composed of Complementary Metal-Oxide-Semiconductor (CMOS) compatible materials thin layers in order to be fully integrated on various types of CMOS image sensors (ambient light sensors, proximity detection, red green blue colour imaging, etc.). As the filters have to be deposited on top of a CMOS device, a good approach in order to evaluate with accuracy their response on chip is (i) to achieve the stacks on Siwafers (as it is the case for the CMOS sensor) (ii) then to perform a direct bonding of the structure on glass wafers (iii) in the end to remove the entire bulk silicon. In this way, we show the measured spectral responses of multilayer interference filters and can check particularly the agreement of the transmission peak with the theoretical calculations and its reproducibility wafer to wafer. It enables to optimize the filters optical designs and to demonstrate that the developed filters fulfill typical CMOS requirements of integration and reliability

Properties of nitrogen doped silicon films deposited by low-pressure chemical vapor deposition from silane and ammonia

Nitrogen doped silicon (NIDOS) films have been deposited by low-pressure chemical vapor deposition from silane SiH4 and ammonia NH3 at high temperature (750°C) and the influences of the NH3/SiH4 gas ratio on the films deposition rate, refractive index, stoichiometry, microstructure, electrical conductivity, and thermomechanical stress are studied. The chemical species derived from silylene SiH2 into the gaseous phase are shown to be responsible for the deposition of NIDOS and/or (silicon rich) silicon nitride. The competition between these two deposition phenomena leads finally to very high deposition rates (100 nm/min) for low NH3/SiH4 gas ratio (R¿0.1). Moreover, complex variations of NIDOS film properties are evidenced and related to the dual behavior of the nitrogen atom into silicon, either n-type substitutional impurity or insulative intersticial impurity, according to the Si¿N atomic bound. Finally, the use of NIDOS deposition for the realization of microelectromechanical systems is investigated