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Direct observation of the gene organization of the complement C4 and 21-hydroxylase loci by pulsed field gel electrophoresis.
Pulsed field gel electrophoresis and enzymes that cut genomic DNA infrequently have been used to define large RFLPs at the human C4 loci. With the enzymes BssH II or Sac II, and C4 or 21-hydroxylase DNA probes, it has been possible to observe directly the number of C4 genes present on a haplotype, and also whether the C4 genes are long (6-7-kb intron present) or short (6-7-kb intron absent). Haplotypes that have either two long C4 genes or one long and one short C4 gene generate BssH II fragments of approximately 115 or approximately 105 kb, respectively. Haplotypes that have either a single long or a single short C4 gene generate BssH II fragments of approximately 80 or approximately 70 kb, respectively. This technique has been used to analyze the DNA isolated from PBMC and allows the complete definition of the C4 gene organization of an individual without the need for family studies
Mass transport from the envelope to the disk of V346 Nor: a case study for the luminosity problem in an FUor-type young eruptive star
A long-standing open issue of the paradigm of low-mass star formation is the
luminosity problem: most protostars are less luminous than theoretically
predicted. One possible solution is that the accretion process is episodic. FU
Ori-type stars (FUors) are thought to be the visible examples for objects in
the high accretion state. FUors are often surrounded by massive envelopes,
which replenish the disk material and enable the disk to produce accretion
outbursts. However, we have insufficient information on the envelope dynamics
in FUors, about where and how mass transfer from the envelope to the disk
happens. Here we present ALMA observations of the FUor-type star V346 Nor at
1.3 mm continuum and in different CO rotational lines. We mapped the density
and velocity structure of its envelope and analyze the results using channel
maps, position-velocity diagrams, and spectro-astrometric methods. We found
that V346 Nor is surrounded by gaseous material on 10000 au scale in which a
prominent outflow cavity is carved. Within the central 700 au, the
circumstellar matter forms a flattened pseudo-disk where material is infalling
with conserved angular momentum. Within 350 au, the velocity profile is
more consistent with a disk in Keplerian rotation around a central star of 0.1
. We determined an infall rate from the envelope onto the disk of
610yr, a factor of few higher than the
quiescent accretion rate from the disk onto the star, hinting for a mismatch
between the infall and accretion rates as the cause of the eruption.Comment: 16 pages, 8 figures, published in Ap
1866-01-11 Lieutenant I.J. Dunham sends his photograph to the Adjutant General
https://digitalmaine.com/cw_me_1st_heavy_corr/1450/thumbnail.jp
The second US Naval Observatory CCD Astrograph Catalog (UCAC2)
The second USNO CCD Astrograph Catalog, UCAC2 was released in July 2003.
Positions and proper motions for 48,330,571 sources (mostly stars) are
available on 3 CDs, supplemented with 2MASS photometry for 99.5% of the
sources. The catalog covers the sky area from -90 to +40 degrees declination,
going up to +52 in some areas; this completely supersedes the UCAC1 released in
2001. Current epoch positions are obtained from observations with the USNO
8-inch Twin Astrograph equipped with a 4k CCD camera. The precision of the
positions are 15 to 70 mas, depending on magnitude, with estimated systematic
errors of 10 mas or below. Proper motions are derived by utilizing over 140
ground-and space-based catalogs, including Hipparcos/Tycho, the AC2000.2, as
well as yet unpublished re-measures of the AGK2 plates and scans from the NPM
and SPM plates. Proper motion errors are about 1 to 3 mas/yr for stars to 12th
magnitude, and about 4 to 7 mas/yr for fainter stars to 16th magnitude. The
observational data, astrometric reductions, results, and important information
for the users of this catalog are presented.Comment: accepted by AJ, AAS LaTeX, 14 figures, 10 table
Episodic accretion at early stages of evolution of low mass stars and brown dwarfs: a solution for the observed luminosity spread in HR diagrams?
We present evolutionary models for young low mass stars and brown dwarfs
taking into account episodic phases of accretion at early stages of the
evolution, a scenario supported by recent large surveys of embedded protostars.
An evolution including short episodes of vigorous accretion (\mdot \ge 10^{-4}
\msolyr) followed by longer quiescent phases (\mdot < 10^{-6} \msolyr) can
explain the observed luminosity spread in HR diagrams of star forming regions
at ages of a few Myr, for objects ranging from a few Jupiter masses to a few
tenths of a solar mass. The gravitational contraction of these accreting
objects strongly departs from the standard Hayashi track at constant \te. The
best agreement with the observed luminosity scatter is obtained if most of the
accretion shock energy is radiated away. The obtained luminosity spread at 1
Myr in the HR diagram is equivalent to what can be misinterpreted as a
10 Myr age spread for non-accreting objects. We also predict a significant
spread in radius at a given \te, as suggested by recent observations. These
calculations bear important consequences on our understanding of star formation
and early stages of evolution and on the determination of the IMF for young
( a few Myr) clusters. Our results also show that the concept of a stellar
birthline for low-mass objects has no valid support.Comment: 8 pages, 5 figures, accepted for publication in APJ Lette
The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Perseus Protostars. VI. Characterizing the Formation Mechanism for Close Multiple Systems
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations
of multiple protostar systems in the Perseus molecular cloud previously
detected by the Karl G. Jansky Very Large Array (VLA). We observed 17 close
(600~AU separation) multiple systems at 1.3~mm in continuum and five
molecular lines (i.e., \twco, \cateo, \thco, HCO, SO) to characterize the
circum-multiple environments in which these systems are forming. We detect at
least one component in the continuum for the 17 multiple systems. In three
systems, one companion is not detected, and for two systems the companions are
unresolved at our observed resolution. We also detect circum-multiple dust
emission toward 8 out of 9 Class 0 multiples. Circum-multiple dust emission is
not detected toward any of the 8 Class I multiples. Twelve systems are detected
in the dense gas tracers toward their disks/inner envelopes. For these 12
systems, we use the dense gas observations to characterize their formation
mechanism. The velocity gradients in the circum-multiple gas are clearly
orthogonal to the outflow directions in 8 out of the 12 systems, consistent
with disk fragmentation. Moreover, only two systems with separations 200~AU
are \textit{inconsistent} with disk fragmentation, in addition to the two
widest systems (500~AU). Our results suggest that disk fragmentation via
gravitational instability is an important formation mechanism for close
multiple systems, but further statistics are needed to better determine the
relative fraction formed via this method.Comment: 48 Pages, 26 Figures, 7 Tables, Accepted by Ap
Centrifugal terms in the WKB approximation and semiclassical quantization of hydrogen
A systematic semiclassical expansion of the hydrogen problem about the
classical Kepler problem is shown to yield remarkably accurate results. Ad hoc
changes of the centrifugal term, such as the standard Langer modification where
the factor l(l+1) is replaced by (l+1/2)^2, are avoided. The semiclassical
energy levels are shown to be exact to first order in with all higher
order contributions vanishing. The wave functions and dipole matrix elements
are also discussed.Comment: 5 pages, to appear in Phys. Rev.
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