A Data Exchange Standard for Optical (Visible/IR) Interferometry

This paper describes the OI Exchange Format, a standard for exchanging calibrated data from optical (visible/infrared) stellar interferometers. The standard is based on the Flexible Image Transport System (FITS), and supports storage of the optical interferometric observables including squared visibility and closure phase -- data products not included in radio interferometry standards such as UV-FITS. The format has already gained the support of most currently-operating optical interferometer projects, including COAST, NPOI, IOTA, CHARA, VLTI, PTI, and the Keck Interferometer, and is endorsed by the IAU Working Group on Optical Interferometry. Software is available for reading, writing and merging OI Exchange Format files.Comment: 26 pages, 1 figur

Exploring Associations between Language and Working Memory Abilities in Children with Specific or Combined Impairments in Language and Working Memory

Children with disproportionate deficits in language, known as Specific Language Impairment (SLI), often demonstrate deficits in nonverbal cognitive abilities, such as working memory. Such findings have prompted much debate on the association between language and working memory functioning. The primary aim of this thesis was to examine the connection between working memory and language abilities among children with specific or combined impairments in these domains. Study 1 examined the potential of narrative retell performance to indicate impairment in language or working memory among 17 children with specific or combined impairment in language or working memory as well as 9 controls. Quantitative analysis using logistic regression revealed that language impairment was predicted best by the interaction between mean length of utterance, percent grammatical utterances, and age, whereas working memory impairment was best predicted by the interaction between events recalled and subordinate clauses per utterance. Exploratory qualitative analysis using qualitative descriptors differentiated narratives of children with and without impairment and revealed clusters of descriptors that identified contrasting speaking styles. Study 2 tested domain-specific interventions in language or working memory using a single subject design. Chapter 3 reports the effects of a narrative-based language intervention for 10 children with language impairment with or without working memory impairment. Results showed gains on narrative ability for most participants, and broader linguistic gains for half of the participants. Intervention effects on related domains (i.e., working memory, reading, math) were evident for some participants as well. Chapter 4 reports the effects of a working memory training program for 7 children with working memory impairment with or without language impairment. Results showed training effects on working memory tasks similar to training tasks for all participants. Transfer to language ability was seen for 4 participants, and transfer to reading or math was evident for 3 participants. Responder analyses for Study 2 showed associations between intervention effectiveness and baseline cognitive abilities, age, speaking style, and intervention intensity. Results support the view that working memory and language are separable but closely related cognitive processes. Responder analyses highlight the importance of considering heterogeneity among children with impairments in research and clinical settings

Generalized Centrifugal Force Model for Pedestrian Dynamics

A spatially continuous force-based model for simulating pedestrian dynamics is introduced which includes an elliptical volume exclusion of pedestrians. We discuss the phenomena of oscillations and overlapping which occur for certain choices of the forces. The main intention of this work is the quantitative description of pedestrian movement in several geometries. Measurements of the fundamental diagram in narrow and wide corridors are performed. The results of the proposed model show good agreement with empirical data obtained in controlled experiments.Comment: 10 pages, 14 figures, accepted for publication as a Regular Article in Physical Review E. This version contains minor change

Spatial Reference Frames for Object Recognition: Tuning for Rotations in Depth

The inferior temporal cortex (IT) of monkeys is thought to play an essential role in visual object recognition. Inferotemporal neurons are known to respond to complex visual stimuli, including patterns like faces, hands, or other body parts. What is the role of such neurons in object recognition? The present study examines this question in combined psychophysical and electrophysiological experiments, in which monkeys learned to classify and recognize novel visual 3D objects. A population of neurons in IT were found to respond selectively to such objects that the monkeys had recently learned to recognize. A large majority of these cells discharged maximally for one view of the object, while their response fell off gradually as the object was rotated away from the neuron"s preferred view. Most neurons exhibited orientation-dependent responses also during view-plane rotations. Some neurons were found tuned around two views of the same object, while a very small number of cells responded in a view- invariant manner. For five different objects that were extensively used during the training of the animals, and for which behavioral performance became view-independent, multiple cells were found that were tuned around different views of the same object. No selective responses were ever encountered for views that the animal systematically failed to recognize. The results of our experiments suggest that neurons in this area can develop a complex receptive field organization as a consequence of extensive training in the discrimination and recognition of objects. Simple geometric features did not appear to account for the neurons" selective responses. These findings support the idea that a population of neurons -- each tuned to a different object aspect, and each showing a certain degree of invariance to image transformations -- may, as an assembly, encode complex 3D objects. In such a system, several neurons may be active for any given vantage point, with a single unit acting like a blurred template for a limited neighborhood of a single view

Viewer-Centered Object Recognition in Monkeys

How does the brain recognize three-dimensional objects? We trained monkeys to recognize computer rendered objects presented from an arbitrarily chosen training view, and subsequently tested their ability to generalize recognition for other views. Our results provide additional evidence in favor of with a recognition model that accomplishes view-invariant performance by storing a limited number of object views or templates together with the capacity to interpolate between the templates (Poggio and Edelman, 1990)

Cognitive and linguistic effects of narrative-based language intervention in children with Developmental Language Disorder

Background and aims: Narrative-based language intervention provides a naturalistic context for targeting overall story structure and specific syntactic goals in children with Developmental Language Disorder (DLD). Given the cognitive demands of narratives, narrative-based language intervention also has the potential to positively impact related abilities such as working memory and academic skills. Methods: Ten children (8–11 years old) with DLD completed 15 sessions of narrative-based language intervention. Results: Results of single subject data revealed gains in language for five participants, four of whom improved on a probe tapping working memory. An additional four participants improved on a working memory probe only. On standardized measures, clinically significant gains were noted for one additional participant on a language measure and one additional participant on a visuospatial working memory. Carry over to reading was noted for three participants and to math for one participant. Across measures, gains in both verbal and visuospatial working memory were common. A responder analysis revealed that improvement in language may be associated with higher verbal short-term memory and receptive language at baseline. Those with working memory impairments were among those showing the fewest improvements across measures. Conclusions: Narrative-based language intervention impacted verbal skills in different ways across individual children with DLD. Implications: Further research is needed to gain an understanding of who benefits most from narrative-based language intervention

Cognitive and Linguistic Effects of Working Memory Training in Children With Corresponding Deficits

Working memory training has been found to result in improvements on tasks similar to those involved in the training (near transfer) but show limited impact on everyday skills such as language or academic abilities (far transfer). Previous research has largely focused on those with a broad range of skills, and examined group level responses. This study uses a single subject design to examine the effect of working memory training on both working memory and related domains in children with working memory impairment. Seven children (8–11 years old) with a working memory impairment completed 20 sessions of computerized working memory intervention. Data revealed near transfer for all participants. Evidence of far transfer to improvements in language, reading, or math was observed for approximately half of the participants on individual measures. Three participants showed convincing but modest training effects across multiple measures. A combination of factors appeared to influence far transfer including age, training intensity, and baseline measures

Multitransitional observations of the CS core of L673

A multitransitional study with the BIMA interferometric array was carried out toward the starless core found in the L673 region, in order to study the small-size structure of the cores detected with previous single--dish observations, which provides us with a test of the predictions of the chemical model of Taylor et al. (1996; 1998). We detected emission in the CS (2-1), N2H+ (1-0), and HCO+ (1-0) lines. Several clumps of size ~0.08 pc were found for each line distributed all over the region where previous single-dish emission was found (Morata et al. 1997). Each molecular transition traces differently the clump distribution, although in some cases the detected clumps are coincident. The distribution of the N2H+ emission and the single-dish NH3 emission are coincident and compatible with an origin in the same gas. The large fraction of missing flux measured for the CS (2-1) transition can be explained if the cloud is formed by a clumpy and heterogeneous medium. Four positions were selected to derive the abundance ratios [N2H+/CS] and [HCO+/CS] from the molecular column density determinations, and to compare them with the values predicted by the chemical model. The model was able to explain the interferometric observations, and, in particular, the chemical differentiation of the detected clumps and the coincidence of the NH3 and N2H+ emissions. The lack of HCO+ towards the two selected positions that trace the more evolved clumps cannot be accounted for by the model, but it is possibly due to strong self-absorption. We propose a classification of the studied clumps according to the stage of chemical evolution indicated by the molecular abundances.Comment: 10 pages, 9 figures, accepted for publication in A&

Nature of complex singularities for the 2D Euler equation

A detailed study of complex-space singularities of the two-dimensional incompressible Euler equation is performed in the short-time asymptotic r\'egime when such singularities are very far from the real domain; this allows an exact recursive determination of arbitrarily many spatial Fourier coefficients. Using high-precision arithmetic we find that the Fourier coefficients of the stream function are given over more than two decades of wavenumbers by \hat F(\k) = C(\theta) k^{-\alpha} \ue ^ {-k \delta(\theta)}, where \k = k(\cos \theta, \sin \theta). The prefactor exponent $\alpha$, typically between 5/2 and 8/3, is determined with an accuracy better than 0.01. It depends on the initial condition but not on $\theta$. The vorticity diverges as $s^{-\beta}$, where $\alpha+\beta= 7/2$ and $s$ is the distance to the (complex) singular manifold. This new type of non-universal singularity is permitted by the strong reduction of nonlinearity (depletion) which is associated to incompressibility. Spectral calculations show that the scaling reported above persists well beyond the time of validity of the short-time asymptotics. A simple model in which the vorticity is treated as a passive scalar is shown analytically to have universal singularities with exponent $\alpha =5/2$.Comment: 22 pages, 24 figures, published version; a version of the paper with higher-quality figures is available at http://www.obs-nice.fr/etc7/euler.pd