312 research outputs found
Fifty years of the Biological Records Centre
In this special issue of the Biological Journal of the Linnean Society, we celebrate 50 years of the Biological Records Centre (BRC) but, more importantly, we celebrate the pioneers of BRC and the volunteer recording community. It is inspiring to consider the many individuals who have contributed to the rich legacy of biological recording since the 16th Century. The core activity of BRC has remained unchanged since its foundation in 1964: working in partnership with volunteer recording schemes and societies to collate, manage, disseminate, and interpret species observations (biological records). However, innovative technologies and the development of statistical approaches are taking biological recording in new and exciting directions. The large spatial coverage and increasingly fine-scale spatial precision of biological records enable ecologists to examine large-scale processes that would be impossible to address without the contribution of voluntary recorders
Near-UV Observations of CS29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes
Employing spectra obtained with the new Keck I HIRES near-UV sensitive
detector, we have performed a comprehensive chemical composition analysis of
the binary blue metal-poor star CS29497-030. Abundances for 29 elements and
upper limits for an additional seven have been derived, concentrating on
elements largely produced via neutron-capture nucleosynthesis. Included in our
analysis are the two elements that define the termination point of the slow
neutron-capture process, lead and bismuth. We determine an extremely high value
of [Pb/Fe] = +3.65 +/- 0.07 (sigma = 0.13) from three features, supporting the
single-feature result obtained in previous studies. We also detect Bi for the
first time in a metal-poor star. Our derived Bi/Pb ratio is in accord with
those predicted from the most recent FRANEC calculations of the slow
neutron-capture process in low-mass AGB stars. We find that the neutron-capture
elemental abundances of CS29497-030 are best explained by an AGB model that
also includes very significant amounts of pre-enrichment of rapid
neutron-capture process material in the protostellar cloud out of which the
CS29497-030 binary system formed. Thus, CS29497-030 is both an ``r+s'' and
``extrinsic AGB'' star. Furthermore, we find that the mass of the AGB model can
be further constrained by the abundance of the light odd-element [Na/Fe] which
is sensitive to the neutron excess.Comment: 7 pages = 4 + 2 colour encapsulated postscript figures + 1 table; to
appear in ApJ Letters; additional jpeg figure available at
ftp://www.astro.caltech.edu/users/iii/cs2949703
A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
We present radial velocities, equivalent widths, model atmosphere parameters,
and abundances or upper limits for 53 species of 48 elements derived from high
resolution optical spectroscopy of 313 metal-poor stars. A majority of these
stars were selected from the metal-poor candidates of the HK Survey of Beers,
Preston, and Shectman. We derive detailed abundances for 61% of these stars for
the first time. Spectra were obtained during a 10-year observing campaign using
the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at
Las Campanas Observatory, the Robert G. Tull Coude Spectrograph on the Harlan
J. Smith Telescope at McDonald Observatory, and the High Resolution
Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. We perform
a standard LTE abundance analysis using MARCS model atmospheres, and we apply
line-by-line statistical corrections to minimize systematic abundance
differences arising when different sets of lines are available for analysis. We
identify several abundance correlations with effective temperature. A
comparison with previous abundance analyses reveals significant differences in
stellar parameters, which we investigate in detail. Our metallicities are, on
average, lower by approx. 0.25 dex for red giants and approx. 0.04 dex for
subgiants. Our sample contains 19 stars with [Fe/H] < -3.5, 84 stars with
[Fe/H] < -3.0, and 210 stars with [Fe/H] < -2.5. Detailed abundances are
presented here or elsewhere for 91% of the 209 stars with [Fe/H] < -2.5 as
estimated from medium resolution spectroscopy by Beers, Preston, and Shectman.
We will discuss the interpretation of these abundances in subsequent papers.Comment: Accepted for publication in the Astronomical Journal. 60 pages, 59
figures, 18 tables. Machine-readable versions of the long tables can be found
in the ancillary data file
Designing hollow nano gold golf balls.
Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core. Selective gold plating of the core followed by removal of the polystyrene beads produced a golf ball-like nanostructure with 100 nm pits. Dissolution of the silica core produced a hollow/porous golf ball-like nanostructure
The Absolute Magnitude of RRc Variables From Statistical Parallax
We present the first definitive measurement of the absolute magnitude of RR
Lyrae c-type variable stars (RRc) determined purely from statistical parallax.
We use a sample of 247 RRc selected from the All Sky Automated Survey (ASAS)
for which high-quality light curves, photometry and proper motions are
available. We obtain high-resolution echelle spectra for these objects to
determine radial velocities and abundances as part of the Carnegie RR Lyrae
Survey (CARRS). We find that M_(V,RRc) = 0.52 +/- 0.11 at a mean metallicity of
[Fe/H] = -1.59. This is to be compared with previous estimates for RRab stars
(M_(V,RRab) = 0.75 +/- 0.13 and the only direct measurement of an RRc absolute
magnitude (RZ Cephei, M_(V, RRc) = 0.27 +/- 0.17). We find the bulk velocity of
the halo to be (W_pi, W_theta, W_z) = (10.9,34.9,7.2) km/s in the radial,
rotational and vertical directions with dispersions (sigma_(W_pi),
sigma_(W_theta), sigma_(W_z)) = (154.7, 103.6, 93.8) km/s. For the disk, we
find (W_pi, W_theta, W_z) = (8.5, 213.2, -22.1) km/s with dispersions
(sigma_(W_pi), sigma_(W_theta), sigma_(W_z)) = (63.5, 49.6, 51.3) km/s.
Finally, we suggest that UCAC2 proper motion errors may be overestimated by
about 25%Comment: Submitted to ApJ. 11 pages including 6 figure
Integrated TiO2 resonators for visible photonics
We demonstrate waveguide-coupled titanium dioxide (TiO2) racetrack resonators
with loaded quality factors of 2x10^4 for the visible wavelengths. The
structures were fabricated in sputtered TiO2 thin films on oxidized silicon
substrates using standard top-down nanofabrication techniques, and passively
probed in transmission measurements using a tunable red laser. Devices based on
this material could serve as integrated optical elements as well as passive
platforms for coupling to visible quantum emitters.Comment: 4 pages, 3 figure
Inheritance of Evolved Glyphosate Resistance in a North Carolina Palmer Amaranth ( Amaranthus palmeri
Inheritance of glyphosate resistance in a Palmer amaranth biotype from North Carolina was studied. Glyphosate rates for 50% survival of glyphosate-resistant (GR) and glyphosate-susceptible (GS) biotypes were 1288 and 58 g ha−1, respectively. These values for F1 progenies obtained from reciprocal crosses (GR×GS and GS×GR were 794 and 501 g ha−1, respectively. Dose response of F1 progenies indicated that resistance was not fully dominant over susceptibility. Lack of significant differences between dose responses for reciprocal F1 families suggested that genetic control of glyphosate resistance was governed by nuclear genome. Analysis of F1 backcross (BC1F1) families showed that 10 and 8 BC1F1 families out of 15 fitted monogenic inheritance at 2000 and 3000 g ha−1 glyphosate, respectively. These results indicate that inheritance of glyphosate resistance in this biotype is incompletely dominant, nuclear inherited, and might not be consistent with a single gene mechanism of inheritance. Relative 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) copy number varied from 22 to 63 across 10 individuals from resistant biotype. This suggested that variable EPSPS copy number in the parents might be influential in determining if inheritance of glyphosate resistance is monogenic or polygenic in this biotype
What Can We Conclude from Death Registration? Improved Methods for Evaluating Completeness
Julie Rajaratnam and colleagues evaluate the performance of a suite of demographic methods that estimate the fraction of deaths registered and counted by civil registration systems, and identify three variants that generally perform the best
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