Biological invasion of European tomato crops by Tuta absoluta: ecology, geographic expansion and prospects for biological control

The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato originating from South America. After its initial detection in eastern Spain in 2006, it rapidly invaded various other European countries and spread throughout the Mediterranean basin. If no control measures are taken, then the pest can cause up to 80-100% yield losses in tomato crops in recently invaded areas and may pose a threat to both greenhouse and open-field tomato production. The exceptional speed and extent of T. absoluta invasion have called for studies documenting its biology and ecology, while indicating an urgent need for efficient and sustainable management methods. The development of approaches to manage T. absoluta would be facilitated through a detailed revision of information on this pest in its area of origin. This review combines information on the invasion by T. absoluta, its ecology, and potential management strategies, including data that may help the implementation of efficient biological control programs. These programs, together with a variety of other management tactics, may allow efficient integrated pest management of T. absoluta in Europe and Mediterranean Basin countries. © 2010 Springer-Verlag

Pertes caractéristiques des électrons dans TlCl, TlBr, Tl I et calcul des fonctions optiques entre 3 et 25 eV

Energy loss spectra of 20 keV electrons have been measured in transmission of thallous halides films. From the energy loss function — Im 1/ε, optical constants are calculated by means of Kramers-Kronig analysis and compared with absorption and reflectance data. The observed singularities are interpreted in terms of plasma loss and band structure.Les pertes d'énergie caractéristiques subies par un faisceau d'électrons de 20 keV à la traversée de films de TlCl, TlBr et TlI ont été mesurées avec un spectrographe magnétique. Les constantes optiques sont calculées par une analyse de Kramers-Kronig à partir de la fonction — Im 1/ε, et sont comparées aux mesures d'absorption et de réflectivité. Les spectres sont interprétés à l'aide d'un récent calcul de structure de bande

Excitations électroniques dans TiO2 rutile et TiO mesure des pertes d'énergie des électrons entre 3 et 60 eV

The energy loss spectra of 20 keV electrons passing through thin films of TiO2 and TiO have been obtained. Optical functions are calculated up to 60 eV using Kramers-Kronig analysis. One-electron excitations and collective modes in these two oxides are discussed and the results are compared with those previously published.Les spectres de pertes d'énergie d'électrons de 20 keV transmis par des couches minces de TiO2 et TiO ont été obtenus, et les fonctions optiques calculées jusqu'à 60 eV par analyse de Kramers-Kronig. Les excitations à un électron et les modes collectifs, dans les deux oxydes, sont discutés sur la base de nos résultats et de ceux existant dans la littérature

MÉTHODE DE CALCUL DES FONCTIONS OPTIQUES A PARTIR DES MESURES DE PERTES CARACTÉRISTIQUES D'ÉNERGIE DES ÉLECTRONS APPLICATION AUX HALOGÉNURES DE THALLIUM

Nous présentons ici une méthode permettant de calculer les fonctions optiques dans un domaine d'énergie assez étendu, par la mesure des pertes caractéristiques d'énergie des électrons. Cette méthode est particulièrement appropriée aux solides ayant un gap supérieur à la résolution expérimentale qui est de l'ordre de 1 eV. Nous donnerons une application de cette méthode au cas des halogénures de thallium. Les détails du calcul et la discussion des résultats ont été publiés par ailleurs [l], [2].We describe a method for obtaining the optical constants (longitudinal dielectric constant, normal reflectivity, etc...) of large gap isotropic semiconductors, from electron energy loss spectra by means of Kramers-Kronig analysis. This method is applied to thallous halides, which have a semiconductor like property together with that of ionic crystals. The validity of the method has been proved for other compounds (CaF2, SrF2, BaF2) by the comparison of our results with available reflectance data obtained with synchrotron radiation

CT iterative reconstruction algorithms: a task-based image quality assessment

International audienceTo assess the dose performance in terms of image quality of filtered back projection (FBP) and two generations of iterative reconstruction (IR) algorithms developed by the most common CT vendors. Materials and methods: We used four CT systems equipped with a hybrid/statistical IR (H/SIR) and a full/partial/advanced model-based IR (MBIR) algorithms. Acquisitions were performed on an ACR phantom at five dose levels. Raw data were reconstructed using a standard soft tissue kernel for FBP and one iterative level of the two IR algorithm generations. The noise power spectrum (NPS) and the task-based transfer function (TTF) were computed. A detectability index (d') was computed to model the detection task of a large mass in the liver (large feature; 120 HU and 25-mm diameter) and a small calcification (small feature; 500 HU and 1.5-mm diameter).Results: With H/SIR, the highest values of d' for both features were found for Siemens, then for Canon and the lowest values for Philips and GE. For the large feature, potential dose reductions with MBIR compared with H/SIR were - 35% for GE, - 62% for Philips, and - 13% for Siemens; for the small feature, corresponding reductions were - 45%, - 78%, and - 14%, respectively. With the Canon system, a potential dose reduction of - 32% was observed only for the small feature with MBIR compared with the H/SIR algorithm. For the large feature, the dose increased by 100%.Conclusion: This multivendor comparison of several versions of IR algorithms allowed to compare the different evolution within each vendor. The use of d' is highly adapted and robust for an optimization process

GaN layer growth in relation to buffer deposition temperature

International audienceDrastic changes in Raman spectra from GaN epitaxial layers are shown to depend on the GaN buffer layer deposition temperature: for temperatures higher than 600 degrees C, non intentional n-doping is evidenced by the screening of the allowed A(1)(LO) phonon by free carriers. Raman measurements at liquid nitrogen temperature confirm this interpretation and speak in favor of. degenerate carrier gas. Partial screening of phonons with wave-vectors differing from the q = 0 transfer of. incident and scattered photons is invoked to explain LO-like scattering over the whole spectral range of optical phonons. Defects correlated to three-dimensional growth and to non-radiative recombination processes in the layers are proposed as the origin of heavy n-doping and of the wave-vector non-conservation. (C) 1997 Elsevier Science S.A