1,759 research outputs found
A Prototype for the PASS Permanent All Sky Survey
A prototype system for the Permanent All Sky Survey (PASS) project is
presented. PASS is a continuous photometric survey of the entire celestial
sphere with a high temporal resolution. Its major objectives are the detection
of all giant-planet transits (with periods up to some weeks) across stars up to
mag 10.5, and to deliver continuously photometry that is useful for the study
of any variable stars. The prototype is based on CCD cameras with short focal
length optics on a fixed mount. A small dome to house it at Teide Observatory,
Tenerife, is currently being constructed. A placement at the antarctic Dome C
is also being considered. The prototype will be used for a feasibility study of
PASS, to define the best observing strategies, and to perform a detailed
characterization of the capabilities and scope of the survey. Afterwards, a
first partial sky surveying will be started with it. That first survey may be
able to detect transiting planets during its first few hundred hours of
operation. It will also deliver a data set around which software modules
dealing with the various scientific objectives of PASS will be developed. The
PASS project is still in its early phase and teams interested in specific
scientific objectives, in providing technical expertise, or in participating
with own observations are invited to collaborate.Comment: Accepted for Astronomische Nachrichten (special issue for 3rd Potsdam
Thinkshop 'Robotic Astronomy' in July 2004). 4 pages, 4 fig
Experimental study of Taylor's hypothesis in a turbulent soap film
An experimental study of Taylor's hypothesis in a quasi-two-dimensional
turbulent soap film is presented. A two probe laser Doppler velocimeter enables
a non-intrusive simultaneous measurement of the velocity at spatially separated
points. The breakdown of Taylor's hypothesis is quantified using the cross
correlation between two points displaced in both space and time; correlation is
better than 90% for scales less than the integral scale. A quantitative study
of the decorrelation beyond the integral scale is presented, including an
analysis of the failure of Taylor's hypothesis using techniques from
predictability studies of turbulent flows. Our results are compared with
similar studies of 3D turbulence.Comment: 27 pages, + 19 figure
Light and Shadows over Petra: astronomy and landscape in Nabataean lands
The Nabateans built several monuments in Petra and elsewhere displaying a
decoration with a preference for astronomical motifs, possibly as a reflection
of their religion. However, due to the lack of direct written accounts and the
scarcity of inscriptions we do not have a clear knowledge on the precise nature
of such believes and how these reflected on the calendar or the religious
time-keeping system of this ancient society. A statistical analysis of the
orientation of their sacred monuments demonstrates that astronomical
orientations were often part of an elaborated plan and possibly a trace of the
astral nature of Nabataean religion. Petra and other monuments in the ancient
Nabataean kingdom have proven to be marvellous laboratories of the interaction
between landscape features and astronomical events showing impressive
hierophanies on particular monuments related to cultic times and worships.
Among other findings, the famous Ad Deir has shown a fascinating ensemble of
light and shadow effects, perhaps connected with the bulk of Nabataean
mythology, while from the impressive Urn tomb, a series of suggestive
solstitial and equinoctial alignments emanate which might have lately helped
its selection as the cathedral of the city. This paper demonstrates that the
sky was a substantial element on Nabataean religion and reveals new evidence
for cultic worship centred on the celestial sphere.Comment: 13 pages, 8 figures, Accepted for publication in Nexus Network
Journal (2013
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Social cognition in intellectually disabled male criminal offenders: a deficit in affect perception?
Purpose: Although intellectual disability (ID) and criminal offending have long been associated, the nature of this link is obfuscated by reliance on weak, historical means of assessing ID and fractionating social cognitive skills. This paper addresses current and future research in social perception, social inference and social problem-solving in ID violent offenders.
Methodology: Literature is reviewed on comorbidity of criminal offending and ID, and on social problem-solving impairment and offending. In an exploratory case-control series comprising six violent offenders with ID and five similarly able controls, emotion recognition and social inference are assessed by the Awareness of Social Inference Test (TASIT) and social problem-solving ability and style by an adapted Social Problem-Solving Inventory (SPSI-R).
Findings: Violent offenders recognised all emotions except ‘anxious’, which they tended to misidentify as ‘surprise’. While offenders could interpret and integrate wider contextual cues, absent such cues offenders were less able to use paralinguistic cues (e.g. emotional tone) to infer speakers' feelings. Offenders in this sample exceeded controls' social problem-solving scores.
Value: ID offenders, like neurotypical offenders, display specific deficits in emotion recognition- particularly fear recognition. Concurrently, enhanced social problem solving (at least as measured by the SPSI-R) in offenders is a novel preliminary finding which requires follow-up in a larger sample. Findings are discussed within the social processing framework, highlighting the need for tighter service-user baseline measures and further research into the causes of ID offending
On the Orbit Structure of the Logarithmic Potential
We investigate the dynamics in the logarithmic galactic potential with an
analytical approach. The phase-space structure of the real system is
approximated with resonant detuned normal forms constructed with the method
based on the Lie transform. Attention is focused on the properties of the axial
periodic orbits and of low order `boxlets' that play an important role in
galactic models. Using energy and ellipticity as parameters, we find analytical
expressions of several useful indicators, such as stability-instability
thresholds, bifurcations and phase-space fractions of some orbit families and
compare them with numerical results available in the literature.Comment: To appear on the Astrophysical Journa
Effects of Uniform and Differential Rotation on Stellar Pulsations
We have investigated the effects of uniform rotation and a specific model for
differential rotation on the pulsation frequencies of 10 \Msun\ stellar models.
Uniform rotation decreases the frequencies for all modes. Differential rotation
does not appear to have a significant effect on the frequencies, except for the
most extreme differentially rotating models. In all cases, the large and small
separations show the effects of rotation at lower velocities than do the
individual frequencies. Unfortunately, to a certain extent, differential
rotation mimics the effects o f more rapid rotation, and only the presence of
some specific observed frequencies with well identified modes will be able to
uniquely constrain the internal rotation of pulsating stars.Comment: 33 pages, 16 figures. Accepted for publication in Ap
SYMPA, a dedicated instrument for Jovian Seismology. II. Real performance and first results
Context. Due to its great mass and its rapid formation, Jupiter has played a
crucial role in shaping the Solar System. The knowledge of its internal
structure would strongly constrain the solar system formation mechanism.
Seismology is the most efficient way to probe directly the internal structure
of giant planets. Aims. SYMPA is the first instrument dedicated to the
observations of free oscillations of Jupiter. Principles and theoretical
performance have been presented in paper I. This second paper describes the
data processing method, the real instrumental performance and presents the
first results of a Jovian observation run, lead in 2005 at Teide Observatory.
Methods. SYMPA is a Fourier transform spectrometer which works at fixed optical
path difference. It produces Doppler shift maps of the observed object.
Velocity amplitude of Jupiter's oscillations is expected below 60 cm/s. Results
Despite light technical defects, the instrument demonstrated to work correctly,
being limited only by photon noise, after a careful analysis. A noise level of
about 12 cm/s has been reached on a 10-night observation run, with 21 % duty
cycle, which is 5 time better than previous similar observations. However, no
signal from Jupiter is clearly highlighted.Comment: 13 pages, 26 figure
Oscillations of a solid sphere falling through a wormlike micellar fluid
We present an experimental study of the motion of a solid sphere falling
through a wormlike micellar fluid. While smaller or lighter spheres quickly
reach a terminal velocity, larger or heavier spheres are found to oscillate in
the direction of their falling motion. The onset of this instability correlates
with a critical value of the velocity gradient scale
s. We relate this condition to the known complex rheology of wormlike
micellar fluids, and suggest that the unsteady motion of the sphere is caused
by the formation and breaking of flow-induced structures.Comment: 4 pages, 4 figure
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