TEM characterization of the fine scale microstructure of a Roman ferrous nail

This paper describes the microstructure of a Roman ferrous nail through its observation by transmission electron microscopy. The morphologies of pearlitic colonies and ferritic grains are detailed and the relationship between pearlitic colonies and ferrite in Roman nails is explicitly demonstrated for the first time. Observations also confirm the presence of dislocations in ferritic grains and attest to the existence of very small carbide precipitates that have not been pointed out previously in standard archaeometric studies

Evolution of interfacial dislocation network during anisothermal high-temperature creep of a nickel-based superalloy

The effect of thermal cycling creep on the dislocation networks at the γ/γ′ interfaces in the MC2 superalloy is investigated. Tensile creep tests were performed under thermal cycling and isothermal conditions at low stress (80 MPa) and high temperature (1150 °C). In these conditions γ′ rafts may dissolve and reprecipitate during thermal cycling creep. The difference between the effects of isothermal and thermal cycling conditions on the γ/γ′ interface dislocation networks, characterized by transmission electron microscopy, is exposed, as well as their evolution during the cycle

Collaboration patterns for networked embedded servers

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Effects of agroforestry on Phytoseiidae communities (Acari: Mesostigmata) in vineyards. A synthesis of a 10-year period of observations

Several species of the predatory mite family Phytoseiidae are of major economic importance for biological pest control in crops, including grapevines. Plant diversification in agrosystems is reported to enhance useful biodiversity and provide ecosystem services. Thus, agroforestry, which consists in co-planting trees and crops, is assumed to be a possible way to ensure regulation of pest outbreaks by phytoseiid mites. This paper investigates the effect of trees ([i]Pinus pinea[/i] and [i]Sorbus domestica[/i]) within vineyards on Phytoseiidae communities. Five experimental plots were considered, two where vines were co-planted with [i]P. pinea[/i] and [i]S. domestica[/i], and three monoculture plots: vines, [i]P. pinea[/i] and [i]S. domestica[/i]. Sampling was carried out on vines and trees in 2003, 2004, 2005, 2010 and 2012. A higher Phytoseiidae diversity was observed in agroforestry plots than in monoculture plots. [i]Kampimodromus aberrans[/i] (replacing [i]T. [T.] exhilaratus[/i]) seemed to colonize these plots 15 years after its plantation, especially when vines were co-planted with [i]P. pinea[/i]. Factors affecting these faunistical changes are discussed. Effects on Phytoseiidae densities differed depending on grape cultivartree species associations. Factors affecting these interactions are discussed; plant diversity does not simply lead to a higher density and diversity of natural enemies

Mobile Service for Adaptive Museum Visits in Wireless-Optical Networks

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Opportunities for Self-Evaluation Increase Student Calibration in an Introductory Biology Course

Accurate self-evaluation is critical for learning. Calibration describes the relationship between learners’ perception of their performance and their actual performance on a task. Here, we describe two studies aimed at assessing and improving student calibration in a first-semester introductory biology course at a 4-year public institution. Study 1 investigated students’ (n = 310) calibration (the difference between estimated and actual exam performance) across one semester. Students were significantly miscalibrated for the first exam: their predicted scores were, on average, significantly higher than their actual scores. The lowest-performing students had the most inaccurate estimates. Calibration improved with each exam. By the final exam, students underestimated their scores. We initiated a second study in the following semester to examine whether explicitly teaching students about self-evaluation strategies would improve their calibration and performance. Instruction in the experimental section (n = 290) focused on students’ tendency to overestimate their abilities and provided retrieval-practice opportunities. Students in the experimental section showed better calibration and performance on the first exam compared with students in a control section taught by a different instructor during the same semester (n = 251). These findings suggest that simple instructional strategies can increase students’ metacognitive awareness and improve their performance

Phytoseiid mites (Acari: Mesostigmata) of Tunisian citrus orchards: Catalogue, biogeography and key for identification

This study presents the results of a survey aimed to determine the species composition of phytoseiid mites on citrus trees, inter-row grasses and conifers planted as break winds within and around citrus orchards. This survey was carried out in fourty six citrus orchards in the main citrus growing regions of Tunisia, from September 2009 to August 2011. Twenty six species belonging to ten genera were found, among which eleven are new for the Tunisian fauna. This paper provides a catalogue of all these species, with some information on their biogeography and biology when available. In addition, a key for the identification of all known Tunisian species (38 species belonging to 17 genera) is given

A first experimental evidence by transmission electron microscopy of dislocation disociation in the TeO2 system

En este trabajo se pretende analizar la microestructura de monocristales de TeO2 (paratelurita) deformados plásticamente en compresión uniaxial a alta temperatura (∼870 K) en distintas condiciones. Para ello, se han ensayado muestras con orientación cristalográfica [110], y se han cortado láminas correspondientes a los planos de deslizamiento para ser observadas con microscopía electrónica de transmisión. El estudio de la subestructura de dislocaciones en este material es complejo debido a su alta anisotropía. La observación de dicha microestructura ha puesto de manifiesto la presencia de disociación de dislocaciones. Es la primera vez que se encuentra este fenómeno en la paratelurita. De la distancia de equilibrio entre dislocaciones parciales, se ha podido obtener una estimación de la energía de falta de apilamiento en este sistema.This work intends to analyse the microstructure of paratellurite (TeO2 single crystals) plastically deformed at high temperature ∼870 K) in uniaxial compression along [110]. Samples have been mechanically tested, and thin foils have been cut from them, corresponding to the slip systems to be observed in transmission electron microscopy. The study of the dislocation substructure in this material is rather complex due to its high anisotropy. Microstructural observation by TEM has put into evidence the presence of dislocation dissociation. This is the first work reporting this fact. From the equilibrium distance between partials, an estimation of the stacking fault energy has been carried out