Direct imaging with highly diluted apertures. II. Properties of the point spread function of a hypertelescope

In the future, optical stellar interferometers will provide true images thanks to larger number of telescopes and to advanced cophasing subsystems. These conditions are required to have sufficient resolution elements (resel) in the image and to provide direct images in the hypertelescope mode. It has already been shown that hypertelescopes provide snapshot images with a significant gain in sensitivity without inducing any loss of the useful field of view for direct imaging applications. This paper aims at studying the properties of the point spread functions of future large arrays using the hypertelescope mode. Numerical simulations have been performed and criteria have been defined to study the image properties. It is shown that the choice of the configuration of the array is a trade-off between the resolution, the halo level and the field of view. A regular pattern of the array of telescopes optimizes the image quality (low halo level and maximum encircled energy in the central peak), but decreases the useful field of view. Moreover, a non-redundant array is less sensitive to the space aliasing effect than a redundant array.Comment: 10 pages paper with referee in A&

Tests with a Carlina-type diluted telescope; Primary coherencing

Studies are under way to propose a new generation of post-VLTI interferometers. The Carlina concept studied at the Haute- Provence Observatory is one of the proposed solutions. It consists in an optical interferometer configured like a diluted version of the Arecibo radio telescope: above the diluted primary mirror made of fixed cospherical segments, a helium balloon (or cables suspended between two mountains), carries a gondola containing the focal optics. Since 2003, we have been building a technical demonstrator of this diluted telescope. First fringes were obtained in May 2004 with two closely-spaced primary segments and a CCD on the focal gondola. We have been testing the whole optical train with three primary mirrors. The main aim of this article is to describe the metrology that we have conceived, and tested under the helium balloon to align the primary mirrors separate by 5-10 m on the ground with an accuracy of a few microns. The servo loop stabilizes the mirror of metrology under the helium balloon with an accuracy better than 5 mm while it moves horizontally by 30 cm in open loop by 10-20 km/h of wind. We have obtained the white fringes of metrology; i.e., the three mirrors are aligned (cospherized) with an accuracy of {\approx} 1 micron. We show data proving the stability of fringes over 15 minutes, therefore providing evidence that the mechanical parts are stabilized within a few microns. This is an important step that demonstrates the feasibility of building a diluted telescope using cables strained between cliffs or under a balloon. Carlina, like the MMT or LBT, could be one of the first members of a new class of telescopes named diluted telescopes.Comment: 18 pages, 17 figures, A&A, accepte

L1 transfer in the acquisition of manner and path in Spanish by native speakers of English

In this article the authors argue that L1 transfer from English is not only important in the early stages of L2 acquisition of Spanish, but remains influential in later stages if there is not enough positive evidence for the learners to progress in their development (Lefebvre, White, & Jourdan, 2006). The findings are based on analyses of path and manner of movement in stories told by British students of Spanish (N = 68) of three different proficiency levels. Verbs that conflate motion and path, on the one hand, are mastered early, possibly because the existence of Latinate path verbs, such as enter and ascend in English, facilitate their early acquisition by British learners of Spanish. Contrary to the findings of Cadierno (2004) and Cadierno and Ruiz (2006), the encoding of manner, in particular in boundary crossing contexts, seems to pose enormous difficulties, even among students who had been abroad on a placement in a Spanish-speaking country prior to the data collection. An analysis of the frequency of manner verbs in Spanish corpora shows that one of the key reasons why students struggle with manner is that manner verbs are so infrequent in Spanish. The authors claim that scarce positive evidence in the language exposed to and little or no negative evidence are responsible for the long-lasting effect of transfer on the expression of manner

Beyond paradigm : The ‘what’ and the ‘how’ of classroom research

This article reviews studies in second language classroom research from a cross-theoretic perspective, arguing that the classroom holds the potential for bringing together researchers from opposing theoretical orientations. It shows how generative and general cognitive approaches share a view of language that implicates both implicit and explicit knowledge, and that holds a bias towards implicit knowledge. Arguing that it is implicit knowledge that should be the object of research, it proposes that classroom research would benefit from incorporating insights from a generative understanding of language. Specifically, there is a need for a more nuanced view of the complexity of language in terms of linguistic domain, and the interaction between those domains. Generative second language acquisition research that shows developmental differences in terms of both linguistic domain and interface is reviewed. The core argument is a call for more attention to the ‘what’ of language development in classroom research and, by implication, teaching practice. As such, the language classroom is seen to offer potential for research that goes beyond paradigm to address both the ‘what’ and the ‘how’ of language development

Evidence from neurolinguistic methodologies: can it actually inform linguistic/ language acquisition theories and translate to evidence-based applications?

This special issue is a testament to the recent burgeoning interest by theoretical linguists, language acquisitionists and teaching practitioners in the neuroscience of language. It offers a highly valuable, state-of-the-art overview of the neurophysiological methods that are currently being applied to questions in the field of second language (L2) acquisition, teaching and processing. Research in the area of neurolinguistics has developed dramatically in the past twenty years, providing a wealth of exciting findings, many of which are discussed in the papers in this volume. The goal of this commentary is twofold. The first is to critically assess the current state of neurolinguistic data from the point of view of language acquisition and processing—informed by the papers that comprise this special issue and the literature as a whole—pondering how the neuroscience of language/processing might inform us with respect to linguistic and language acquisition theories. The second goal is to offer some links from implications of exploring the first goal towards informing language teachers and the creation of linguistically and neurolinguistically-informed evidence-based pedagogies for non-native language teaching

Grammatical aspect and L2 learners’ on-line processing of temporarily ambiguous sentences in English: A self-paced reading study with German, Dutch and French L2 learners

The results of a self-paced reading study with advanced German, Dutch and French second language (L2) learners of English showed that their online comprehension of early closure (EC) sentences which are initially misanalysed by native English speakers (e.g. While John hunted the frightened rabbit escaped) was affected by whether or not, like English, their first language (L1) encodes aspect grammatically (French) or only via lexical means (German, Dutch). The English and the higher proficiency French participants showed a processing asymmetry in their online reading of the temporarily ambiguous sentences, assumed to be caused by the difference in the aspectual perspective a comprehender takes when initial verbs appear in the past simple vs. the past progressive. In contrast, the German and Dutch learners, irrespective of proficiency, treated both progressive and simple sentences in the same way, despite the fact that all the L2 learners were matched according to their metalinguistic knowledge of English aspectual distinctions. Furthermore, despite patterning with the German learners online, the Dutch L2 learners’ offline judgments were more akin to those of the English native speakers and the French L2 learners, showing an effect of aspect, which could be argued to lend support to the idea that progressive aspect may be becoming grammaticalized in Dutch. Taken together, the results of this study add to our growing understanding of cross-linguistic influences during online L2 sentence processing, and differences between L2 parsing and learners’ metalinguistic L2 performance