The Main Belt Comets and ice in the Solar System

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies

Exploring the Relationship between Semantics and Space

The asymmetric distribution of human spatial attention has been repeatedly documented in both patients and healthy controls. Biases in the distribution of attention and/or in the mental representation of space may also affect some aspects of language processing. We investigated whether biases in attention and/or mental representation of space affect semantic representations. In particular, we investigated whether semantic judgments could be modulated by the location in space where the semantic information was presented and the role of the left and right parietal cortices in this task. Healthy subjects were presented with three pictures arranged horizontally (one middle and two outer pictures) of items belonging to the same semantic category. Subjects were asked to indicate the spatial position in which the semantic distance between the outer and middle pictures was smaller. Subjects systematically overestimated the semantic distance of items presented in the right side of space. We explored the neural correlates underpinning this bias using rTMS over the left and right parietal cortex. rTMS of the left parietal cortex selectively reduced this rightward bias. Our findings suggest the existence of an attentional and/or mental representational bias in semantic judgments, similar to that observed for the processing of space and numbers. Spatial manipulation of semantic material results in the activation of specialised attentional resources located in the left hemisphere

Interferometric Observations of Rapidly Rotating Stars

Optical interferometry provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Through direct observation of rotationally distorted photospheres at sub-milliarcsecond scales, we are now able to characterize latitude dependencies of stellar radius, temperature structure, and even energy transport. These detailed new views of stars are leading to revised thinking in a broad array of associated topics, such as spectroscopy, stellar evolution, and exoplanet detection. As newly advanced techniques and instrumentation mature, this topic in astronomy is poised to greatly expand in depth and influence.Comment: Accepted for publication in A&AR

The Photospheric Convection Spectrum

Abstract. Spectra of the cellular photospheric flows are determined from observations acquired by the MDI instrument on the SOHO spacecraft. Spherical harmonic spectra are obtained from the full-disk observations. Fourier spectra are obtained from the high-resolution observations. The p-mode oscillation signal and instrumental artifacts are reduced by temporal filtering of the Doppler data. The resulting spectra give power (kinetic energy) per wave number for effective spherical harmonic degrees from 1 to over 3000. Significant power is found at all wavenumbers, including the small wavenumbers representative of giant cells. The time evolution of the spectral coefficients indicates that these small wavenumber components rotate at the solar rotation rate and thus represent a com-ponent of the photospheric cellular flows. The spectra show distinct peaks representing granules and supergranules but no distinct features at wavenumbers representative of mesogranules or giant cells. The observed cellular patterns and spectra are well represented by a model that includes two distinct modes – granules and supergranules. 1

A brain-damaged patient with an unusual perceptuomotor deficit

When interacting with objects, the pattern of movements is influenced by such object characteristics as size and position. Little is known about the effect of higher level categorical encoding of objects upon movements. Here we present evidence for an approval-for-action process which takes into account such encoding. For the brain-damaged subject L.P., the ability to complete actions involving two objects in central vision is influenced by the semantic or functional relationship between the objects. Even though she perceives only one object, she can integrate two related objects into a coordinated action. If the objects are not related she is unable to integrate them into a single motor act. We propose that selection-for-action systems include processes which gate conceptually the behavioural disposition to action