889 research outputs found
Statistics of associations among IR galaxies
In the course of expanding the search of Kleinmann et. al. (1988) for distant, infrared-luminous objects, the authors noticed (as is often remarked) that a large number of infrared-selected galaxies have close neighbors or show merger characteristics (e.g., tidal tails, distorted disks). Because the sample size is large (567 infrared galaxies and 2182 field galaxies), this sample is ideal for statistically examining the importance of interactions among infrared galaxies. In particular, the authors compare the nearest-neighbor distribution and the two-point correlation function of their sample with that of a control sample of field galaxies
Optical processing for distributed sensors in control of flexible spacecraft
A recent potential of distributed image processing is discussed. Applications in the control of flexible spacecraft are emphasized. Devices are currently being developed at NASA and in universities and industries that allow the real-time processing of holographic images. Within 5 years, it is expected that, in real-time, one may add or subtract holographic images at optical accuracy. Images are stored and processed in crystal mediums. The accuracy of their storage and processing is dictated by the grating level of laser holograms. It is far greater than that achievable using current analog-to-digital, pixel oriented, image digitizing and computing techniques. Processors using image processing algebra can conceptually be designed to mechanize Fourier transforms, least square lattice filters, and other complex control system operations. Thus, actuator command inputs derived from complex control laws involving distributed holographic images can be generated by such an image processor. Plans are revealed for the development of a Conjugate Optics Processor for control of a flexible object
Cooperating Agents for 3D Scientific Data Interpretation
Many organizations collect vast quantities of three-dimensional (3-D) scientific data in volumetric form for a range of purposes, including resource exploration, market forecasting, and process modelling. Traditionally, these data have been interpreted by human experts with only minimal software assistance. However, such manual interpretation is a painstakingly slow and tedious process. Moreover, since interpretation involves subjective judgements and each interpreter has different scientific knowledge and experience, formulation of an effective interpretation often requires the cooperation of numerous such experts. Hence, there is a pressing need for a software system in which individual interpretations can be generated automatically and then refined through the use of cooperative reasoning and information sharing. To this end, a prototype system, SurfaceMapper, has been developed in which a community of cooperating software agents automatically locate and display interpretations in a volume of 3-D scientific data. The challenges and experiences in designing and building such a system are discussed. Particular emphasis is given to the agents' interactions and an empirical evaluation of the effectiveness of different cooperation strategies is presented
A Flaring Megamaser in Mrk 348
We report new observations of the H2O megamaser in the Seyfert 2 galaxy Mrk
348. Following our initial detection in 2000 March using the Effelsberg 100 m
telescope, re-analysis of previous data on this source indicates that the maser
was present but only marginally detectable in late 1997. Monitoring through
late 2000 shows that the maser has again decreased to its original level. The
H2O line is redshifted by ~130 km/s with respect to the systemic velocity, is
extremely broad, with a FWHM of 130 km/s, and has no detectable high velocity
components within 1500 km/s on either side of the strong line. Followup VLBA
observations show that the maser emission emanates entirely from a region >0.25
pc in extent, toward the base of the radio jet.Comment: 4 pages, 2 figures, to appear in Cosmic Masers: from Protostars to
Black Holes, IAU 206, Eds. V. Migenes et al., ASP Conference Serie
Star formation and gas inflows in the OH Megamaser galaxy IRAS03056+2034
We have obtained observations of the OH Megamaser galaxy IRAS03056+0234 using
Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Very Large
Array (VLA) and Hubble Space Telescope (HST). The HST data reveals spiral arms
containing knots of emission associated to star forming regions. The GMOS-IFU
data cover the spectral range of 4500 to 7500 \AA\ at a velocity resolution of
90 km s and spatial resolution of 506 pc. The emission-line flux
distributions reveal a ring of star forming regions with radius of 786 pc
centred at the nucleus of the galaxy, with an ionized gas mass of 1.2
10M, an ionizing photon luminosity of log Q[H]=53.8 and a
star formation rate of 4.9 M yr. The emission-line ratios and
radio emission suggest that the gas at the nuclear region is excited by both
starburst activity and an active galactic nucleus. The gas velocity fields are
partially reproduced by rotation in the galactic plane, but show, in addition,
excess redshifts to the east of the nucleus, consistent with gas inflows
towards the nucleus, with velocity of 45 km s and a mass inflow
rate of 7.710 M yr.Comment: To be published in MNRA
Online molecular characterisation of organic aerosols in an atmospheric chamber using extractive electrospray ionisation mass spectrometry
Abstract. The oxidation of biogenic volatile organic compounds (VOCs) represents a substantial source of secondary organic aerosol (SOA) in the atmosphere. In this study, we present online measurements of the molecular constituents formed in the gas and aerosol phases during α-pinene oxidation in the Cambridge Atmospheric Simulation Chamber (CASC). We focus on characterising the performance of extractive electrospray ionisation (EESI) mass spectrometry (MS) for particle analysis. A number of new aspects of EESI-MS performance are considered here. We show that relative quantification of organic analytes can be achieved in mixed organicâinorganic particles. A comprehensive assignment of mass spectra for α-pinene derived SOA in both positive and negative ion modes is obtained using an ultra-high-resolution mass spectrometer. We compare these online spectra to conventional offline ESI-MS spectra and find good agreement in terms of the compounds identified, without the need for complex sample work-up procedures. Under our experimental conditions, EESI-MS signals arise only from particle-phase analytes. High-time-resolution (7âŻmin) EESI-MS spectra are compared with simulations from the near-explicit Master Chemical Mechanism (MCM) for a range of reaction conditions. We show that MS peak abundances scale with modelled concentrations for condensable products (pinonic acid, pinic acid, OH-pinonic acid). Relative quantification is achieved throughout SOA formation as the composition, size and mass (5â2400âŻÂ”gâŻmâ3) of particles is evolving. This work provides a robust demonstration of the advantages of EESI-MS for chamber studies over offline ESI-MS (time resolution, relative quantification) and over hard online techniques (molecular information).
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