The Light Curve of the Weakly-Accreting T Tauri Binary KH 15D from 2005-10: Insights into the Nature of its Protoplanetary Disk

Photometry of the unique pre-main sequence binary system KH 15D is presented, spanning the years 2005-2010. This system has exhibited photometric variations and eclipses over the last 50 years caused by a precessing circumbinary disk. Advancement of the occulting edge across the binary orbit has continued and the photospheres of both stars are now completely obscured at all times. The system is now visible only by scattered light, and yet it continues to show a periodic variation on the orbital cycle with an amplitude exceeding two magnitudes. This variation, which depends only on the binary phase, has likely been present in the data since at least 1995. It can, by itself, account for shoulders on the light curve prior to ingress and following egress, obviating the need for components of extant models such as a scattering halo around star A or forward scattering from a fuzzy disk edge. A plausible source for the variable scattering component is reflected light from the far side of a warped occulting disk. We have detected color changes in V-I of several tenths of a magnitude to both the blue and red that occur during times of minima. These may indicate the presence of a third source of light (faint star) within the system, or a change in the reflectance properties of the disk as the portion being illuminated varies with the orbital motion of the stars. The data support a picture of the circumbinary disk as a geometrically thin, optically thick layer of perhaps mm or cm-sized particles that has been sculpted by the binary stars and possibly other components into a decidedly nonplanar configuration. A simple (infinitely sharp) knife-edge model does a good job of accounting for all of the recent (2005-2010) occultation data.Comment: To appear in The Astronomical Journa

A novel interplanetary communications relay

A case study of a potential Earth-Mars interplanetary communications relay, designed to ensure continuous communications, is detailed. The relay makes use of orbits based on artificial equilibrium points via the application of continuous low thrust, which allows a spacecraft to hover above the orbital plane of Mars and thus ensure communications when the planet is occulted with respect to the Earth. The artificial equilibria of two different low-thrust propulsion technologies are considered: solar electric propulsion, and a solar sail/solar electric propulsion hybrid. In the latter case it is shown that the combination of sail and solar electric propulsion may prove advantageous, but only under specific circumstances of the relay architecture suggested. The study takes into account factors such as the spacecraft's power requirements and communications band utilized to determine the mission and system architecture. A detailed contingency analysis is considered for recovering the relay after increasing periods of spacecraft motor failure, and combined with a consideration for how best to deploy the relay spacecraft to maximise propellant reserves and mission duration

Spatial Interference Detection for Mobile Visible Light Communication

Taking advantage of the rolling shutter effect of CMOS cameras in smartphones is a common practice to increase the transfered data rate with visible light communication (VLC) without employing external equipment such as photodiodes. VLC can then be used as replacement of other marker based techniques for object identification for Augmented Reality and Ubiquitous computing applications. However, the rolling shutter effect only allows to transmit data over a single dimension, which considerably limits the available bandwidth. In this article we propose a new method exploiting spacial interference detection to enable parallel transmission and design a protocol that enables easy identification of interferences between two signals. By introducing a second dimension, we are not only able to significantly increase the available bandwidth, but also identify and isolate light sources in close proximity

The Commensal Real-time ASKAP Fast Transients (CRAFT) survey

We are developing a purely commensal survey experiment for fast (<5s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.Comment: accepted for publication in PAS

Interioridad y Fantasías Maternas en El Rey Lear

Este ensaio discute as questões de interioridade e angústias maternas na peça King Lear de Shakespeare. Aborda também o conceito de &nbsp;significante, baseado nos pressupostos de Lacan. Primeiramente, apresenta os pressupostos de Lacan sobre o significante e a constituição da subjetividade. Depois disso, discute as angústias maternas partindo do trabalho de Janet Adelman (1992). Adelman estuda fantasias maternas baseadas na psicanálise Freudiana, mas nunca menciona os pressupostos de Lacan. Ela não revela os dispositivos mais profundos na interioridade de Lear que são negados e reprimidos, cujas projeções dirigidas e internas sugerem dimensões e disposições escuras do self interior de Lear. Ela só discute fantasias maternas re-imaginado com suas filhas. Para preencher essa lacuna, discuto e analiso as constelações psíquicas que se revelam nos silêncios, não-ditos e não sequituros de seus discursos, que apontam um conjunto de metáforas projetadas além da fase pré-edipiana, experimentada por Gloucester. Essa experiência não será dirigida somente a sua imagem de Edgar, mas ele projeta sua raiva para outros personagens da peça, como Edmond e suas figuras maternas. A experiência de auto-individuação poderia ser associada a uma cadeia de elementos imagéticos e paranóicos, que apontam para a perda da referencialidade, da totalidade e da centralidade da psique e, conseqüentemente, confunde e re-direciona o locus de suas projeções interiores. Segundo Lacan, o inconsciente é algo puramente lógico, em outras palavras, é algo originado do significante.ABSTRACT This essay aims at discussing the issues of inwardness and maternal anxieties in Shakespeare’s play King Lear. It also approaches the signifier, based on Lacan’s assumptions. It first presents Lacan’s assumptions on the signifier and the constitution of subjetivity. After that, it discusses maternal anxieties based on Janet Adelman’s work (1992). Adelman studies maternal fantasies based on Freud’s psychoanalytic framework, but she never mentions Lacan’s assumptions. She does not reveal the deeper devices in Lear’s inwardness are denied and repressed, whose driving and inward projections suggest dark dimensions and dispositions of Lear’s inner self; she only discusses maternal fantasies re-imagined with his daughters. In order to overcome this gap, I discuss and analyse the psychic constellations which are revealed in the silences, non-said, and non-sequiturs of his speeches, which point out a set of metaphors projected beyond the pre-oedipal phase, experienced by Gloucester. Such experience will not be directed only to his son Edgar image, but he projects his anger to other characters in the play, such as Edmond and his maternal figures. The experience of self individuation could be associated to a chain of imagetic, paranoid elements, which point out the loss of referenciality, wholeness and centrality of the psyche of the self, and consequently confuses him and makes him re-direct the locus of his inward projections. According to Lacan, the unconscious is something purely logic, in other words, it is something originated from the signifier.RESUMEN Este ensayo discute los problemas de la interioridad y la angustia materna en la obra El Rey Lear de Shakespeare. También se analiza el concepto de significante, basado en los supuestos de Lacan. En primer lugar, presenta los supuestos de Lacan sobre el significante y la constitución de la subjetividad. A partir de entonces, discute la angustia materna partindo del trabajo de Janet Adelman (1992). Adelman estudia las fantasías maternas basado en el psicoanálisis freudiano, pero nunca menciona los supuestos de Lacan. Ella no revela los dispositivos más profundos en el interior de Lear que son negados y reprimidos, cuyas proyecciones interires sugieren dimensiones y disposiciones oscuras del sujeto de Lear. Sólo discute las fantasías maternales re-imaginados con sus hijas. Para llenar este vacío, discuto y analizo las constelaciones psíquicas que se revelan en los silencios y no sequituros de sus discursos, que enlazan una serie de metáforas además de la fase de pre-edípica, experimentada por Gloucester. Esta experiencia no sólo se dirige a imagen de su hijo Edgar, pero él proyecta su ira a otros personajes de la obra, como Edmond y sus figuras maternas. La experiencia de auto-individuación podría estar relacionado con una cadena de la imaginería y elementos paranoides relacionadas con la perda de referencial, la totalidad y la centralidad de la psique y por lo tanto confuso y re-dirige el lugar de sus proyecciones interiores. Según Lacan, el inconsciente es puramente lógico, en otras palabras, es algo que se originó a partir del significante

From deep dyslexia to agrammatic comprehension on silent reading

We report on a case of a French-speaking patient whose performance on reading aloud single words was characteristically deep dyslexic (in spite of preserved ability to identify letters), and whose comprehension on silent sentence reading was agrammatic and strikingly poorer than on oral reading. The first part of the study is mainly informative as regards (i) the relationship between letter identification, semantic paralexias and the ability to read nonwords, (ii) the differential character of silent and oral reading tasks, and (iii) the potential modality-dependent character of the deficits in comprehension encountered. In the second part of the study we examine the patient's sensitivity to verb-noun ambiguity and probe her skills in the comprehension of indexical structures by exploring her ability to cope with number agreement and temporal and prepositional relations. The results indicate the patient's sensitivity to certain dimensions of these linguistic categories, reveal a partly correct basis for certain incorrect responses, and, on the whole, favor a definition of the patient's disorders in terms of a deficit in integrating indexical information in language comprehension. More generally, the present study substantiates a microgenetic approach to neuropsychology, where the pathological behavior due to brain damage is described as an arrest of microgenesis at an early stage of development, so that patient's responses take the form of unfinished "products" which would normally undergo further development

Shape-based invariant features extraction for object recognition

International audienceThe emergence of new technologies enables generating large quantity of digital information including images; this leads to an increasing number of generated digital images. Therefore it appears a necessity for automatic systems for image retrieval. These systems consist of techniques used for query specification and re-trieval of images from an image collection. The most frequent and the most com-mon means for image retrieval is the indexing using textual keywords. But for some special application domains and face to the huge quantity of images, key-words are no more sufficient or unpractical. Moreover, images are rich in content; so in order to overcome these mentioned difficulties, some approaches are pro-posed based on visual features derived directly from the content of the image: these are the content-based image retrieval (CBIR) approaches. They allow users to search the desired image by specifying image queries: a query can be an exam-ple, a sketch or visual features (e.g., colour, texture and shape). Once the features have been defined and extracted, the retrieval becomes a task of measuring simi-larity between image features. An important property of these features is to be in-variant under various deformations that the observed image could undergo. In this chapter, we will present a number of existing methods for CBIR applica-tions. We will also describe some measures that are usually used for similarity measurement. At the end, and as an application example, we present a specific ap-proach, that we are developing, to illustrate the topic by providing experimental results