1,520 research outputs found
A Detailed Study of Giants and Horizontal Branch Stars in M68: Atmospheric Parameters and Chemical Abundances
In this paper, we present a detailed high-resolution spectroscopic study of
post main sequence stars in the Globular Cluster M68. Our sample, which covers
a range of 4000 K in , and 3.5 dex in , is comprised of
members from the red giant, red horizontal, and blue horizontal branch, making
this the first high-resolution globular cluster study covering such a large
evolutionary and parameter space. Initially, atmospheric parameters were
determined using photometric as well as spectroscopic methods, both of which
resulted in unphysical and unexpected , , , and
[Fe/H] combinations. We therefore developed a hybrid approach that addresses
most of these problems, and yields atmospheric parameters that agree well with
other measurements in the literature. Furthermore, our derived stellar
metallicities are consistent across all evolutionary stages, with
[Fe/H] = 2.42 ( = 0.14) from 25 stars. Chemical
abundances obtained using our methodology also agree with previous studies and
bear all the hallmarks of globular clusters, such as a Na-O anti-correlation,
constant Ca abundances, and mild -process enrichment.Comment: Accepted to the Astronomical Journa
First results from the UBC etch-alignment mosaic CCD
First imaging results are obtained with a new CCD mosaic prototype (3K x 3k,
15 \mu m pixels). The CCDs are aligned using an etched socket alignment
technique. Three different measurements of the alignment are made using star
images, test p attern images, and microscope analysis. The CCDs have an angular
misalignement o f less than 30 ppm. The composite device is flat to within \pm
3 \mu m, with rows/columns oriented to within 20 ppm. The use of an existing
technology with built in precision reduces many of the difficulties and
expenses typically encountered with mosaic detector construction. A new camera
being built for the UBC liquid mirror telescope is al so described.Comment: 11 pages, 6 figs, 3 tables To appear in SPIE Photonics West97 -
Electronic Imagin
Organic semiconductor laser platform for the detection of DNA by AgNP plasmonic enhancement
Organic semiconductor lasers are a sensitive biosensing platform that respond to specific biomolecule binding events. So far, such biosensors have utilized protein-based interactions for surface functionalization but a nucleic acidâbased strategy would considerably widen their utility as a general biodiagnostic platform. This manuscript reports two important advances for DNA-based sensing using an organic semiconductor (OS) distributed feedback (DFB) laser. First, the immobilization of alkyne-tagged 12/18-mer oligodeoxyribonucleotide (ODN) probes by Cu-catalyzed azide alkyne cycloaddition (CuAAC) or âclick-chemistryâ onto an 80 nm thick OS laser film modified with an azide-presenting polyelectrolyte monolayer is presented. Second, sequence-selective binding to these immobilized probes with complementary ODN-functionalized silver nanoparticles, is detected. As binding occurs, the nanoparticles increase the optical losses of the laser mode through plasmonic scattering and absorption, and this causes a rise in the threshold pump energy required for laser action that is proportional to the analyte concentration. By monitoring this threshold, detection of the complementary ODN target down to 11.5 pM is achieved. This complementary binding on the laser surface is independently confirmed through surface-enhanced Raman spectroscopy (SERS)
Influence of extended dynamics on phase transitions in a driven lattice gas
Monte Carlo simulations and dynamical mean-field approximations are performed
to study the phase transition in a driven lattice gas with nearest-neighbor
exclusion on a square lattice. A slight extension of the microscopic dynamics
with allowing the next-nearest-neighbor hops results in dramatic changes.
Instead of the phase separation into high- and low-density regions in the
stationary state the system exhibits a continuous transition belonging to the
Ising universality class for any driving. The relevant features of phase
diagram are reproduced by an improved mean-field analysis.Comment: 3 pages, 3 figure
Reactions of iminoglycines with C60 fullerene and their unambiguous characterisation using NMR spectroscopy
SERS enhancement of silver nanoparticles prepared by a template-directed triazole ligand strategy
Two advances in the development of a one-pot method to prepare silver nanoparticles (AgNPs) using the Tollensâ reagent are described. First, a template-directed process of AgNP synthesis using resorcinol triazole ligands bearing two pendent galactose sugars is shown. Second, the conversion of these AgNPs into SERS nanotags is demonstrated using malachite green isothiocyanate as the Raman reporter molecule
SERS enhancement of silver nanoparticles prepared by a template-directed triazole ligand strategy
Two advances in the development of a one-pot method to prepare silver nanoparticles (AgNPs) using the Tollens' reagent are described. First, a template-directed process of AgNP synthesis using resorcinol triazole ligands bearing two pendent galactose sugars is shown. Second, the conversion of these AgNPs into SERS nanotags is demonstrated using malachite green isothiocyanate as the Raman reporter molecule
- âŠ