7,696 research outputs found
An Anomalous UV Extension in NGC6251
Deep U-band FOC images of the nuclear region of NGC6251 have revealed a
region of extended emission which is most probably radiation scattered from a
continuum source in the nucleus. This radiation lies interior to a dust ring,
is nearly perpendicular to the radio jet axis, and is seen primarily in the FOC
U and b filters. The extension has a low observed polarization(), and
is unlikely to arise from line emission. We know of no other examples similar
to what we have found in NGC 6251, and we offer some tentative explanations.
The nuclear morphology shows clear similarities to that seen in the nucleus of
NGC 4261 except for the extended U-band radiation.Comment: 14 pages AAStex format + 4 figures; accepted for publication in ApJ
Letter
Development of Heterogeneous Photosensitized Transition Metal Oxide Water-Splitting Catalysts on Silica Support
The research presented in this manuscript describes the development of photosensitized inexpensive catalysts based on readily available materials. The investigation covers synthesis and characterization of photosensitizers based on porphyrins, mechanical and thermal coating of solid support with semiconducting transition metal oxides, photosensitization of the semiconducting layer, and characterization of the photoelectrochemical properties displayed by the new materials. The process of water oxidation is of primary interest here, with little emphasis put on reduction of protons to gaseous hydrogen. Photoelectrochemically produced protons serve as a probe of effectiveness of the catalysts. Several systems are described, and two catalysts are identified as the most efficient
Classifying and monitoring water quality by use of satellite imagery
A technique in which LANDSAT measurements from very clear lakes are subtracted from measurements from other lakes in order to remove atmospheric and surface noise effects to obtain a residual signal dependent only on the material suspended in the water is described. This residual signal is used by the Multispectral Data Analysis System as a basis for producing color categorized imagery showing lakes by type and concentration of suspended material. Several hundred lakes in the Madison and Spooner, Wisconsin area were categorized for tannin or non-tannin waters and for the degree of algae, silt, weeds, and bottom effects
Test and evaluation of a multifunction keyboard and a dedicated keyboard for control of a flight management computer
A flight management computer (FMC) control display unit (CDU) test was conducted to compare two types of input devices: a fixed legend (dedicated) keyboard and a programmable legend (multifunction) keyboard. The task used for comparison was operation of the flight management computer for the Boeing 737-300. The same tasks were performed by twelve pilots on the FMC control display unit configured with a programmable legend keyboard and with the currently used B737-300 dedicated keyboard. Flight simulator work activity levels and input task complexity were varied during each pilot session. Half of the points tested were previously familiar with the B737-300 dedicated keyboard CDU and half had no prior experience with it. The data collected included simulator flight parameters, keystroke time and sequences, and pilot questionnaire responses. A timeline analysis was also used for evaluation of the two keyboard concepts
The Prowler IADS performance evaluation tool (PIPE)
The Prowler IADS Performance Evaluator is a computer simulation model of an airstrike protected by electronic countermeasures platforms. It is designed for integration into mission planning systems and analysis tools used to determine the effectiveness of electronic countermeasures or allocate scarce countermeasures equipment. PIPE's features include flexible hierarchical IADS specification, the capability to construct and calculate appropriate measures of performance, graphical presentation analysis results, mission visualizationNaval Postgraduate School, Monterey, California.http://archive.org/details/prowleriadsperfo00bailMonterey, California. Naval Postgraduate SchoolApproved for public release; distribution is unlimited
SIVIC: Open-Source, Standards-Based Software for DICOM MR Spectroscopy Workflows
Quantitative analysis of magnetic resonance spectroscopic imaging (MRSI) data provides maps of metabolic parameters that show promise for improving medical diagnosis and therapeutic monitoring. While anatomical images are routinely reconstructed on the scanner, formatted using the DICOM standard, and interpreted using PACS workstations, this is not the case for MRSI data. The evaluation of MRSI data is made more complex because files are typically encoded with vendor-specific file formats and there is a lack of standardized tools for reconstruction, processing, and visualization. SIVIC is a flexible open-source software framework and application suite that enables a complete scanner-to-PACS workflow for evaluation and interpretation of MRSI data. It supports conversion of vendor-specific formats into the DICOM MR spectroscopy (MRS) standard, provides modular and extensible reconstruction and analysis pipelines, and provides tools to support the unique visualization requirements associated with such data. Workflows are presented which demonstrate the routine use of SIVIC to support the acquisition, analysis, and delivery to PACS of clinical 1H MRSI datasets at UCSF
Which solar EUV indices are best for reconstructing the solar EUV irradiance ?
The solar EUV irradiance is of key importance for space weather. Most of the
time, however, surrogate quantities such as EUV indices have to be used by lack
of continuous and spectrally resolved measurements of the irradiance. The
ability of such proxies to reproduce the irradiance from different solar
atmospheric layers is usually investigated by comparing patterns of temporal
correlations. We consider instead a statistical approach. The TIMED/SEE
experiment, which has been continuously operating since Feb. 2002, allows for
the first time to compare in a statistical manner the EUV spectral irradiance
to five EUV proxies: the sunspot number, the f10.7, Ca K, and Mg II indices,
and the He I equivalent width.
Using multivariate statistical methods such as multidimensional scaling, we
represent in a single graph the measure of relatedness between these indices
and various strong spectral lines. The ability of each index to reproduce the
EUV irradiance is discussed; it is shown why so few lines can be effectively
reconstructed from them. All indices exhibit comparable performance, apart from
the sunspot number, which is the least appropriate. No single index can
satisfactorily describe both the level of variability on time scales beyond 27
days, and relative changes of irradiance on shorter time scales.Comment: 6 figures, to appear in Adv. Space. Re
Differential localization and expression of complement in a rat model of motor neuron disease
ComBio is the major ASBMB conference held each year, in association with other organisations. This page has links to past, current and future ComBio meetings. Further information and links will be placed online as they become available
Stellar Kinematics of the Double Nucleus of M31
We report observations of the double nucleus of M31 with the f/48 long-slit
spectrograph of the HST Faint Object Camera. We obtain a total exposure of
19,000 sec. over 7 orbits, with the 0.063-arcsec-wide slit along the line
between the two brightness peaks (PA 42). A spectrum of Jupiter is used as a
spectral template. The rotation curve is resolved, and reaches a maximum
amplitude of ~250 km/s roughly 0.3 arcsec either side of a rotation center
lying between P1 and P2, 0.16 +/- 0.05 arcsec from the optically fainter P2. We
find the velocity dispersion to be < 250 km/s everywhere except for a narrow
``dispersion spike'', centered 0.06 +/- 0.03 arcsec on the anti-P1 side of P2,
in which sigma peaks at 440 +/- 70 km/s. At much lower confidence, we see local
disturbances to the rotation curve at P1 and P2, and an elevation in sigma at
P1. At very low significance we detect a weak asymmetry in the line-of-sight
velocity distribution opposite to the sense usually encountered. Convolving our
V and sigma profiles to CFHT resolution, we find good agreement with the
results of Kormendy & Bender (1998, preprint), though there is a 20%
discrepancy in the dispersion that cannot be attributed to the dispersion
spike. Our results are not consistent with the location of the maximum
dispersion as found by Bacon et al. We find that the sinking star cluster model
of Emsellem & Combes (1997) does not reproduce either the rotation curve or the
dispersion profile. The eccentric disk model of Tremaine (1995) fares better,
and can be improved somewhat by adjusting the original parameters. However,
detailed modeling will require dynamical models of significantly greater
realism.Comment: 29 pages, Latex, AASTeX v4.0, with 7 eps figures. To appear in The
Astronomical Journal, February 199
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