301 research outputs found
Soliton cellular automaton associated with crystal base
We calculate the combinatorial matrix for all elements of
where denotes the
-perfect crystal of level , and then study the soliton cellular
automaton constructed from it. The solitons of length are identified with
elements of the -crystal . The scattering
rule for our soliton cellular automaton is identified with the combinatorial
matrix for -crystals
Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalogue
We present refined coordinates and proper motion data for the high proper
motion (HPM) stars in the Luyten Half-Second (LHS) catalogue. The positional
uncertainty in the original Luyten catalogue is typically >10" and is often
>30". We have used the digital scans of the Palomar Observatory Sky Survey
(POSS) I and POSS II plates to derive more accurate positions and proper
motions of the objects. Out of the 4470 candidates in the LHS catalogue, 4323
objects were manually re-identified in the POSS I and POSS II scans. A small
fraction of the stars were not found due to the lack of finder charts and
digitized POSS II scans. The uncertainties in the revised positions are
typically ~2", but can be as high as ~8" in a few cases; this is a large
improvement over the original data. Cross-correlation with the Tycho-2 and
Hipparcos catalogues yielded 819 candidates (with m_R < 12). For these brighter
sources, the position and proper motion data have been replaced with the more
accurate Tycho/Hipparcos data. In total, we have revised proper motion
measurements and coordinates for 4040 stars and revised coordinates for 4330
stars, which are presented here.Comment: 108 pages. Accepted for Publication in ApJ Suppl. Some errors caused
by the transcription errors in the original LHS catalogue have been corrected
in this resubmission. The most current version of the catalogue is also
available online at http://www.stsci.edu/~ksahu/lh
Structures of falcipain-2 and falcipain-3 bound to small molecule inhibitors: implications for substrate specificity.
Falcipain-2 and falcipain-3 are critical hemoglobinases of Plasmodium falciparum, the most virulent human malaria parasite. We have determined the 2.9 A crystal structure of falcipain-2 in complex with the epoxysuccinate E64 and the 2.5 A crystal structure of falcipain-3 in complex with the aldehyde leupeptin. These complexes represent the first crystal structures of plasmodial cysteine proteases with small molecule inhibitors and the first reported crystal structure of falcipain-3. Our structural analyses indicate that the relative shape and flexibility of the S2 pocket are affected by a number of discrete amino acid substitutions. The cumulative effect of subtle differences, including those at "gatekeeper" positions, may explain the observed kinetic differences between these two closely related enzymes
Integral-Field Spectroscopy of the Post Red Supergiant IRC +10420: evidence for an axi-symmetric wind
We present NAOMI/OASIS adaptive-optics assisted integral-field spectroscopy
of the transitional massive hypergiant IRC +10420, an extreme mass-losing star
apparently in the process of evolving from a Red Supergiant toward the
Wolf-Rayet phase. To investigate the present-day mass-loss geometry of the
star, we study the appearance of the line-emission from the inner wind as
viewed when reflected off the surrounding nebula. We find that, contrary to
previous work, there is strong evidence for wind axi-symmetry, based on the
equivalent-width and velocity variations of H and Fe {\sc ii}
6516. We attribute this behaviour to the appearance of the complex
line-profiles when viewed from different angles. We also speculate that the Ti
{\sc ii} emission originates in the outer nebula in a region analogous to the
Strontium Filament of Carinae, based on the morphology of the
line-emission. Finally, we suggest that the present-day axisymmetric wind of
IRC +10420, combined with its continued blueward evolution, is evidence that
the star is evolving toward the B[e] supergiant phase.Comment: 22 pages, 9 figures, accepted for publication in ApJ. B&W-optimized
version can be downloaded from http://www.cis.rit.edu/~bxdpci/pubs.htm
High-velocity white dwarfs: thick disk, not dark matter
We present an alternative interpretation of the nature of the extremely cool,
high-velocity white dwarfs identified by Oppenheimer et al (2001) in a
high-latitude astrometric survey. We argue that the velocity distribution of
the majority of the sample is more consistent with the high-velocity tail of a
rotating population, probably the thick disk, rather than a pressure-supported
halo system. Indeed, the observed numbers are well matched by predictions based
on the kinematics of a complete sample of nearby M dwarfs. Analysing only stars
showing retrograde motion gives a local density close to that expected for
white dwarfs in the stellar (R^-3.5) halo. Under our interpretation, none of
the white dwarfs need be assigned to the dark-matter, heavy halo. However,
luminosity functions derived from observations of these stars can set important
constraints on the age of the oldest stars in the Galactic Disk.Comment: 11 pages, 5 figures; accepted for ApJ, 29 May 200
The Cervical Dystonia Impact Profile (CDIP-58): Can a Rasch developed patient reported outcome measure satisfy traditional psychometric criteria?
<p>Abstract</p> <p>Background</p> <p>The United States Food and Drug Administration (FDA) are currently producing guidelines for the scientific adequacy of patient reported outcome measures (PROMs) in clinical trials, which will have implications for the selection of scales used in future clinical trials. In this study, we examine how the Cervical Dystonia Impact Profile (CDIP-58), a rigorous Rasch measurement developed neurologic PROM, stands up to traditional psychometric criteria for three reasons: 1) provide traditional psychometric evidence for the CDIP-58 in line with proposed FDA guidelines; 2) enable researchers and clinicians to compare it with existing dystonia PROMs; and 3) help researchers and clinicians bridge the knowledge gap between old and new methods of reliability and validity testing.</p> <p>Methods</p> <p>We evaluated traditional psychometric properties of data quality, scaling assumptions, targeting, reliability and validity in a group of 391 people with CD. The main outcome measures used were the CDIP-58, Medical Outcome Study Short Form-36, the 28-item General Health Questionnaire, and Hospital and Anxiety and Depression Scale.</p> <p>Results</p> <p>A total of 391 people returned completed questionnaires (corrected response rate 87%). Analyses showed: 1) data quality was high (low missing data ≤ 4%, subscale scores could be computed for > 96% of the sample); 2) item groupings passed tests for scaling assumptions; 3) good targeting (except for the Sleep subscale, ceiling effect = 27%); 4) good reliability (Cronbach's alpha ≥ 0.92, test-retest intraclass correlations ≥ 0.83); and 5) validity was supported.</p> <p>Conclusion</p> <p>This study has shown that new psychometric methods can produce a PROM that stands up to traditional criteria and supports the clinical advantages of Rasch analysis.</p
Studying the Galactic Bulge Through Spectroscopy of Microlensed Sources: I. Theoretical Considerations
The observed spectra of the microlensed sources towards the Galactic bulge
may be used as a tool for studying the kinematics and extinction effects in the
Galactic bulge. In this paper, we first investigate the expected distribution
of the microlensed sources as a function of depth within the Galactic bulge.
Our analysis takes a magnitude limited microlensing survey into account, and
includes the effects of extinction. We show that, in the current magnitude
limited surveys, the probability that the source lies at the far side of the
bulge is larger than the probability that the source lies at the near side. We
then investigate the effects of extinction on the observed spectra of
microlensed sources. Kurucz model spectra and the observed extinctions towards
the Galactic bulge have been used to demonstrate that the microlensed sources
should clearly show the effects of extinction which, in turn, can be used as a
statistical measure of the contribution of the disk lenses and bulge lenses at
different depths. The spectra of the microlensed sources provide a unique probe
to derive the radial velocities of a sample which lies preferentially at the
far side of the Galactic bulge. The radial velocities, coupled with the
microlensing time scales, can thus be useful in studying the 3-dimensional
kinematics of the Galactic bulge.Comment: 35 pages, 12 figures, Major revisions, Accepted for publication in
Ap
The WFC3 Galactic Bulge Treasury Program: Metallicity Estimates for the Stellar Population and Exoplanet Hosts
We present new UV-to-IR stellar photometry of four low-extinction windows in
the Galactic bulge, obtained with the Wide Field Camera 3 on the Hubble Space
Telescope (HST). Using our five bandpasses, we have defined reddening-free
photometric indices sensitive to stellar effective temperature and metallicity.
We find that the bulge populations resemble those formed via classical
dissipative collapse: each field is dominated by an old (~10 Gyr) population
exhibiting a wide metallicity range (-1.5 < [Fe/H] < 0.5). We detect a
metallicity gradient in the bulge population, with the fraction of stars at
super-solar metallicities dropping from 41% to 35% over distances from the
Galactic center ranging from 0.3 to 1.2 kpc. One field includes candidate
exoplanet hosts discovered in the SWEEPS HST transit survey. Our measurements
for 11 of these hosts demonstrate that exoplanets in the distinct bulge
environment are preferentially found around high-metallicity stars, as in the
solar neighborhood, supporting the view that planets form more readily in
metal-rich environments.Comment: Accepted for publication in The Astrophysical Journal Letters. Latex,
5 pages, ApJ forma
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