10,184 research outputs found
PANIC: the new panoramic NIR camera for Calar Alto
PANIC is a wide-field NIR camera, which is currently under development for
the Calar Alto observatory (CAHA) in Spain. It uses a mosaic of four Hawaii-2RG
detectors and covers the spectral range from 0.8-2.5 micron(z to K-band). The
field-of-view is 30x30 arcmin. This instrument can be used at the 2.2m
telescope (0.45arcsec/pixel, 0.5x0.5 degree FOV) and at the 3.5m telescope
(0.23arcsec/pixel, 0.25x0.25 degree FOV). The operating temperature is about
77K, achieved by liquid Nitrogen cooling. The cryogenic optics has three flat
folding mirrors with diameters up to 282 mm and nine lenses with diameters
between 130 mm and 255 mm. A compact filter unit can carry up to 19 filters
distributed over four filter wheels. Narrow band (1%) filters can be used. The
instrument has a diameter of 1.1 m and it is about 1 m long. The weight limit
of 400 kg at the 2.2m telescope requires a light-weight cryostat design. The
aluminium vacuum vessel and radiation shield have wall thicknesses of only 6 mm
and 3 mm respectively.Comment: This paper has been presented in the SPIE of Astronomical Telescopes
and Instrumentation 2008 in Marseille (France
Formation and Collapse of Quiescent Cloud Cores Induced by Dynamic Compressions
(Abridged) We present numerical hydrodynamical simulations of the formation,
evolution and gravitational collapse of isothermal molecular cloud cores. A
compressive wave is set up in a constant sub-Jeans density distribution of
radius r = 1 pc. As the wave travels through the simulation grid, a
shock-bounded spherical shell is formed. The inner shock of this shell reaches
and bounces off the center, leaving behind a central core with an initially
almost uniform density distribution, surrounded by an envelope consisting of
the material in the shock-bounded shell, with a power-law density profile that
at late times approaches a logarithmic slope of -2 even in non-collapsing
cases. The resulting density structure resembles a quiescent core of radius <
0.1 pc, with a Bonnor-Ebert-like (BE-like) profile, although it has significant
dynamical differences: it is initially non-self-gravitating and confined by the
ram pressure of the infalling material, and consequently, growing continuously
in mass and size. With the appropriate parameters, the core mass eventually
reaches an effective Jeans mass, at which time the core begins to collapse.
Thus, there is necessarily a time delay between the appearance of the core and
the onset of its collapse, but this is not due to the dissipation of its
internal turbulence as it is often believed. These results suggest that
pre-stellar cores may approximate Bonnor-Ebert structures which are however of
variable mass and may or may not experience gravitational collapse, in
qualitative agreement with the large observed frequency of cores with BE-like
profiles.Comment: Accepted for publication in ApJ. Associated mpeg files can be found
in http://www.astrosmo.unam.mx/~g.gomez/publica.htm
Severe hypoglycemia secondary to methimazoleâinduced insulin autoimmune syndrome in a 16 year old AfricanâAmerican male
Insulin autoimmune syndrome ( IAS ) or Hirata's disease is a rare disorder characterized by hypoglycemia secondary to insulin autoantibodies ( IAb ). Over 200 patients have been described from Japan with significantly less numbers being reported from outside the Orient. IAS is more common in patients older than 40âyr of age with reports in the pediatric age group being notably rarer. Exposure to sulfhydryl group containing medications is implicated in the pathogenesis of this syndrome. In this report, we describe a case of IAS in an AfricanâAmerican adolescent. A 16âyrâold healthy AfricanâAmerican male was diagnosed with Graves' disease and started on Methimazole. Four weeks later, he was found unconscious and hypoglycemic (blood sugar 1.5âmmol/L). Evaluation was negative for insulinoma. Insulin antibodies were positive. Oral glucose tolerance test revealed elevated free insulin concentrations with disproportionately elevated total insulin levels. The patient was started on prednisone, diazoxide, and propranolol for management of IAS and hyperthyroidism. Thyroid radioâablation was subsequently undertaken. The doses of prednisone and diazoxide were tapered and these medications discontinued after 9âmonths. The insulin antibody levels decreased gradually and became undetectable in 6âmonths with resolution of the hypoglycemia.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94489/1/pedi884.pd
Differential cognitive impairment for diverse forms of multiple sclerosis
BACKGROUND: Cognitive impairment is a common feature in multiple sclerosis (MS) patients and occurs in 60% of all cases. Unfortunately, neurological examination does not always agree with the neuropsychological evaluation in determining the cognitive profile of the patient. On the other hand, psychophysiological techniques such as event-related potentials (ERPs) can help in evaluating cognitive impairment in different pathologies. Behavioural responses and EEG signals were recorded during the experiment in three experimental groups: 1) a relapsing-remitting group (RRMS), 2) a benign multiple sclerosis group (BMS) and 3) a Control group. The paradigm employed was a spatial attention task with central cues (Posner experiment). The main aim was to observe the differences in the performance (behavioural variables) and in the latency and amplitude of the ERP components among these groups. RESULTS: Our data indicate that both MS groups showed poorer task performance (longer reaction times and lower percentage of correct responses), a latency delay for the N1 and P300 component, and a different amplitude for the frontal N1. Moreover, the deficit in the BMS group, indexed by behavioural and pyschophysiological variables, was more pronounced compared to the RRMS group. CONCLUSION: The present results suggest a cognitive impairment in the information processing in all of these patients. Comparing both pathological groups, cognitive impairment was more accentuated in the BMS group compared to the RMSS group. This suggests a silent deterioration of cognitive skills for the BMS that is not usually treated with pharmacological or neuropsychological therapy
Dynamical cloud formation traced by atomic and molecular gas
Context. Atomic and molecular cloud formation is a dynamical process. However, kinematic signatures of these processes are still observationally poorly constrained.
Aims. We identify and characterize the cloud formation signatures in atomic and molecular gas.
Methods. Targeting the cloud-scale environment of the prototypical infrared dark cloud G28.3, we employed spectral line imaging observations of the two atomic lines HI and [CI] as well as molecular lines observations in 13CO in the 1â0 and 3â2 transitions. The analysis comprises investigations of the kinematic properties of the different tracers, estimates of the mass flow rates, velocity structure functions, a histogram of oriented gradients (HOG) study, and comparisons to simulations.
Results. The central infrared dark cloud (IRDC) is embedded in a more diffuse envelope of cold neutral medium traced by HI self-absorption and molecular gas. The spectral line data as well as the HOG and structure function analysis indicate a possible kinematic decoupling of the HI from the other gas compounds. Spectral analysis and positionâvelocity diagrams reveal two velocity components that converge at the position of the IRDC. Estimated mass flow rates appear rather constant from the cloud edge toward the center. The velocity structure function analysis is consistent with gas flows being dominated by the formation of hierarchical structures.
Conclusions. The observations and analysis are consistent with a picture where the IRDC G28.3 is formed at the center of two converging gas flows. While the approximately constant mass flow rates are consistent with a self-similar, gravitationally driven collapse of the cloud, external compression (e.g., via spiral arm shocks or supernova explosions) cannot be excluded yet. Future investigations should aim at differentiating the origin of such converging gas flows
A new method to trace colloid transport pathways in macroporous soils using Xâray computed tomography and fluorescence macrophotography
The fast and deep percolation of particles through soil is attributed to preferential flow pathways, and their extent can be critical in the filtering of particulate pollutants in soil. Particle deposition on the pore walls and transport between the pores and matrix modulate the preferential flow of particulate pollutants. In the present research, we developed a novel method of combining fluorescence macrophotography and Xâray computed tomography (CT) to track preferential pathways of colloidal fluorescent microspheres (MS) in breakthrough experiments. We located accumulations of MS by fluorescence imaging and used them to delimit the deposition structures along the preferential colloid pathways by superimposing these images on the 3âD pore network obtained from CT. Advectionâdiffusion with transport parameters from the dualâporosity equation correlated with preferential pathway features across different soil management techniques. However, management did not influence the morphology of the MS preferential pathways. Preferential flow occurred in only a small fraction of the total pore network and was controlled by pores connected to the soil surface and by matrix density
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