Search results for "TEFL"
showing 10 items of 25 documents
Genetic diversity of Iberian populations ofBemisia tabaci(Hemiptera: Aleyrodidae) based on random amplified polymorphic DNA-polymerase chain reaction
2001
The genetic structure of six Iberian populations of the whitefly Bemisia tabaci, two of them biotype Q, one biotype B, and the other three a mixture of both, has been studied using random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). A total of 336 individuals was completely discriminated by means of 234 scored bands. Separate analyses of molecular variance of haploid males and diploid females using the pairwise number of differences between haplotypes showed that biotypes contribute significantly more to the observed variability than populations within biotypes. On average, gene flow between two biotypes of the same population is lower than between populations of identica…
Endosymbiont communities in Bemisia tabaci: a metagenomic approach
2014
Este trabajo es parte de un programa de investigación que tiene como objetivo dilucidar la evolución de las bacterias endosimbiontes utilizando los consorcios insecto-bacteria como modelo. Los diferentes estudios realizados sobre los insectos y sus bacterias endosimbiontes han arrojado luz sobre los cambios ocurridos tras la adquisición de una forma de vida intracelular, así cómo la interacción entre diferentes endosimbiontes formando comunidades endosimbioticas. Dos son los objetivos principales de este trabajo. El primera (capítulos “Portiera y su socio Hamiltonella” y “El tercer pasajero: Cardinium cBtQ1)” trata de analizar y describir las relaciones de la comunidad endosimbiótica en B. …
Learner identity in EFL: An analysis of digital texts of identity in higher education
2018
This study explores learner identity (LI) in digital texts of identity (DTI) produced by college learners in English as a foreign language (EFL). In so doing, it aims to shed light on learners’ connections of their learning experiences across time and settings, and their impact on the various learner identities that form their LI. It also intends to elucidate how learners construct powerful learner identities in and through their digital discourses. To this end, 51 DTI were collected and scrutinized, following studies on LI, critical and poststructuralist discourse analysis, and “thematic” and “dialogic/performative” analysis within narrative research. Learners established connections betwe…
IPM-recommended insecticides harm beneficial insects through contaminated honeydew
2020
The use of some systemic insecticides has been banned in Europe because they are toxic to beneficial insects when these feed on nectar. A recent study shows that systemic insecticides can also kill beneficial insects when they feed on honeydew. Honeydew is the sugar-rich excretion of hemipterans and is the most abundant carbohydrate source for beneficial insects such as pollinators and biological control agents in agroecosystems. Here, we investigated whether the toxicity of contaminated honeydew depends on i) the hemipteran species that excretes the honeydew; ii) the active ingredient, and iii) the beneficial insect that feeds on it. HPLC-MS/MS analyses demonstrated that the systemic insec…
Low Levels of Mitochondrial DNA and Symbiont Diversity in the Worldwide Agricultural Pest, the Greenhouse Whitefly Trialeurodes vaporariorum (Hemipte…
2015
Trialeurodes vaporariorum, the greenhouse whitefly, is a cosmopolitan agricultural pest. Little is known about the genetic diversity of T. vaporariorum and the bacterial symbionts associated with this species. Here, we undertook a large phylogeographic study by investigating both the mitochondrial (mt) diversity and the infection status of 38 T. vaporariorum collections from 18 countries around the world. Genetic diversity of T. vaporariorum was studied by analyzing sequence data from the mt cytochrome oxidase I, cytochrome b, and NADH dehydrogenase subunit 5 genes. Maximum-likelihood (ML) phylogeny reconstruction delineated 2 clades characterized by limited sequence divergence: one clade c…
Multipactor Effect Characterization of Dielectric Materials for Space Applications
2018
[EN] The objective of this paper is to advance the state of the art in the characterization of the multipactor effect in dielectric materials. The materials studied are the most commonly used dielectrics in space applications, namely, Alumina, Rexolite, Rogers RT5870, Rohacell, Teflon, and Ultem 1000. In this paper, a new family of coaxial waveguide components, covering the L- and S-bands, with a wideband, low-pass response has been designed, and six different prototypes have been specifically optimized and manufactured. The six prototypes have then been used to simulate and measure the multipactor breakdown susceptibility charts for the six dielectric materials investigated. Finally, the s…
Genome Evolution in the Primary Endosymbiont of Whiteflies Sheds Light on Their Divergence
2015
International audience; Hemipteran insects are well-known in their ability to establish symbiotic relationships with bacteria. Among them, heteropteran insects present an array of symbiotic systems, ranging from the most common gut crypt symbiosis to the more restricted bacteriome-associated endosymbiosis, which have only been detected in members of the superfamily Lygaeoidea and the family Cimicidae so far. Genomic data of heteropteran endosymbionts are scarce and have merely been analyzed from the Wolbachia endosymbiont in bed bug and a few gut crypt-associated symbionts in pentatomoid bugs. In this study, we present the first detailed genomic analysis of a bacteriome-associated endosymbi…
Anxiety and self-related constructs in learners who stutter in the learning of English as a foreign language
2020
La Ansiedad en una Lengua Extranjera (ALE) se ha considerado uno de los factores más importantes que afectan el grado de éxito del aprendizaje de idiomas (Daubney, Dewaele y Goknou, 2017). Sin embargo, la investigación sobre ALE en Alumnos Con Tartamudez (ACT) es escasa. Esta tesis doctoral aborda este problema explorando la relación entre ALE y la tartamudez en el aprendizaje del inglés como lengua extranjera en el contexto español. Con este fin, se recopilaron y examinaron cuentas de primera mano de ACT y se midió la ALE. Por lo tanto, este estudio tiene como objetivo contribuir a la literatura sobre ALE mediante la documentación de las experiencias de un grupo de estudiantes subrepresent…
External and internal elimination of supernumerary larvae in the whitefly parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae)
2008
Abstract The solitary parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is one of the key biological control agents of the whitefly Bemisia argentifolii Bellows & Perring, also known as B. tabaci (Gennadius) B-biotype (Homoptera: Aleyrodidae). We present new information on its biology, and particularly about larval elimination during the first instar in cases of superparasitism. For the first time, physical elimination of supernumerary larvae was observed, both outside and inside the host. These findings are documented with confocal microscopy images and video recordings. We observed more than 350 B. argentifolii nymphs, parasitized with one, two or more than two larvae. Physi…
Viral diseases causing the greatest economic losses to the tomato crop. II. The Tomato yellow leaf curl virus — a review
1996
Abstract Tomato yellow leaf curl geminivirus (TYLCV), transmitted by the whitefly Bemisia tabaci (Gennadius) is one of the most devastating diseases of cultivated tomato (Lycopersicon esculentum Mill.). TYLCV causes economic losses up to 100% in tomato crop in many tropical and subtropical regions, and is spreading towards new areas. The increasing economic importance of TYLCV has resulted in the need for accurate detection and identification procedures, stimulating intensive research efforts focused on virus biology, diversity, and epidemiology to develop successful control strategies. Breeding for resistance appears to be the best approach to control this disease, but to date only partial…