1,772 research outputs found
High-resolution infrared spectroscopy as a tool to detect false positives of transit search programs
Transit search programs such as CoRoT and Kepler now have the capability of
detecting planets as small as the Earth. The detection of these planets however
requires the removal of all false positives. Although many false positives can
be identified by a detailed analysis of the LCs, the detections of others
require additional observations. An important source of false positives are
faint eclipsing binaries within the PSF of the target stars. We develop a new
method that allows us to detect faint eclipsing binaries with a separation
smaller than one arcsec from target stars. We thereby focus on binaries that
mimic the transits of terrestrial planets. These binaries can be either at the
same distance as the target star (triple stars), or at either larger, or
smaller distances. A close inspection of the problem indicates that in all
relevant cases the binaries are brighter in the infrared than in the optical
regime. We show how high resolution IR spectroscopy can be used to remove these
false positives. For the triple star case, we find that the brightness
difference between a primary and an eclipsing secondary is about 9-10 mag in
the visual but only about 4.5-5.9 magnitudes in the K-band. We demonstrate how
the triple star hypothesis can be excluded by taking a high-resolution IR
spectrum. Simulations of these systems show that the companions can be detected
with a false-alarm probability of 2%, if the spectrum has a S/N-ratio > 100. We
show that high-resolution IR spectra also allows to detect most of the false
positives caused by foreground or background binaries. If high resolution IR
spectroscopy is combined with photometric methods, virtually all false
positives can be detected without RV measurements. It is thus possible to
confirm transiting terrestrial planets with a modest investment of observing
time.Comment: 6 pages, 7 figure
Recommended from our members
Low inductance gas switching.
The laser trigger switch (LTS) is a key component in ZR-type pulsed power systems. In ZR, the pulse rise time through the LTS is > 200 ns and additional stages of pulse compression are required to achieve the desired <100 ns rise time. The inductance of the LTS ({approx}500nH) in large part determines the energy transfer time through the switch and there is much to be gained in improving system performance and reducing system costs by reducing this inductance. The current path through the cascade section of the ZR LTS is at a diameter of {approx} 6-inches which is certainly not optimal from an inductance point of view. The LTS connects components of much greater diameter (typically 4-5 feet). In this LDRD the viability of switch concepts in which the diameter of cascade section is greatly increased have been investigated. The key technical question to be answered was, will the desired multi-channel behavior be maintained in a cascade section of larger diameter. This LDRD proceeded in 2 distinct phases. The original plan for the LDRD was to develop a promising switch concept and then design, build, and test a moderate scale switch which would demonstrate the key features of the concept. In phase I, a switch concept which meet all electrical design criteria and had a calculated inductance of 150 nH was developed. A 1.5 MV test switch was designed and fabrication was initiated. The LDRD was then redirected due to budgetary concerns. The fabrication of the switch was halted and the focus of the LDRD was shifted to small scale experiments designed to answer the key technical question concerning multi-channel behavior. In phase II, the Multi-channel switch test bed (MCST) was designed and constructed. The purpose of MCST was to provide a versatile, fast turn around facility for the study the multi-channel electrical breakdown behavior of a ZR type cascade switch gap in a parameter space near that of a ZR LTS. Parameter scans on source impedance, gap tilt, gap spacing and electrode diameter were conducted
MicroMAPS CO Measurements over North America and Europe during Summer-Fall 2004
The MicroMAPS instrument is a nadir-viewing, gas filter-correlated radiometer which operating in the 4.67 micrometer fundamental band of carbon monoxide. Originally designed and built for a space mission, this CO remote sensor is being flown in support of satellite validation and science instrument demonstrations for potential UAV applications. The MicroMAPS instrument system, as flown on Proteus, was designed by a senior student design project in the Aerospace Engineering Department, Virginia Tech, in Blacksburg, VA. and then revised by Systems Engineers at NASA Langley. The final instrument system was integrated and tested at NASA LaRC, in partnership with Scaled Composites and Virginia Space Grant Consortium (VSGC). VSGC supervised the fabrication of the nacelle that houses the instrument system on the right rear tail boom of Proteus. Full system integration and flight testing was performed at Scaled Composites, in Mojave, in June 2004. Its successful performance enabled participation in four international science missions on Proteus: in 2004, INTEX -NA over eastern North America in July, ADRIEX over the Mediterranean region and EAQUATE over the United Kingdom region in September,and TWP-ICE over Darwin, Australia and the surrounding oceans in Jan-Feb 2006. These flights resulted in nearly 300 hours of data. In parallel with the engineering developments, theoretical radiative transfer models were developed specifically for the MicroMAPS instrument system at the University of Virginia, Mechanical Engineering Department by a combined undergraduate and graduate student team. With technical support from Resonance Ltd. in June 2005, the MicroMAPS instrument was calibrated for the conditions under which the Summer-Fall 2004 flights occurred. The analyses of the calibration data, combined with the theoretical radiative transfer models, provide the first data reduction for the science flights reported here. These early results and comparisons with profile data from the NASA DC-8, the coincident AIRS CO retrievals, and selected CO measurements from the MOZAIC program will be presented
Improving the Health Benefits of Snap Bean: Genome-Wide Association Studies of Total Phenolic Content
Snap beans are a significant source of micronutrients in the human diet. Among the micronutrients present in snap beans are phenolic compounds with known beneficial effects on human health, potentially via their metabolism by the gut-associated microbiome. The genetic pathways leading to the production of phenolics in snap bean pods remain uncertain. In this study, we quantified the level of total phenolic content (TPC) in the Bean Coordinated Agriculture Program (CAP) snap bean diversity panel of 149 accessions. The panel was characterized spectrophotometrically for phenolic content with a Folin-Ciocalteu colorimetric assay. Flower, seed and pod color were also quantified, as red, purple, yellow and brown colors are associated with anthocyanins and flavonols in common bean. Genotyping was performed through an Illumina Infinium Genechip BARCBEAN6K_3 single nucleotide polymorphism (SNP) array. Genome-Wide Association Studies (GWAS) analysis identified 11 quantitative trait nucleotides (QTN) associated with TPC. An SNP was identified for TPC on Pv07 located near the P gene, which is a major switch in the flavonoid biosynthetic pathway. Candidate genes were identified for seven of the 11 TPC QTN. Five regulatory genes were identified and represent novel sources of variation for exploitation in developing snap beans with higher phenolic levels for greater health benefits to the consumer
1919: Abilene Christian College Bible Lectures - Full Text
Please note: There are pages missing from this book because of a misprint. These missing pages do not remove any information from the book.
Uploaded by Jackson Hage
The Multiplicity of Massive Stars: A High Angular Resolution Survey with the HST Fine Guidance Sensor
We present the results of an all-sky survey made with the Fine Guidance
Sensor on Hubble Space Telescope to search for angularly resolved binary
systems among the massive stars. The sample of 224 stars is comprised mainly of
Galactic O- and B-type stars and Luminous Blue Variables, plus a few luminous
stars in the Large Magellanic Cloud. The FGS TRANS mode observations are
sensitive to detection of companions with an angular separation between 0."01
and 1."0 and brighter than . The FGS observations resolved 52
binary and 6 triple star systems and detected partially resolved binaries in 7
additional targets (43 of these are new detections). These numbers yield a
companion detection frequency of 29% for the FGS survey. We also gathered
literature results on the numbers of close spectroscopic binaries and wider
astrometric binaries among the sample, and we present estimates of the
frequency of multiple systems and the companion frequency for subsets of stars
residing in clusters and associations, field stars, and runaway stars. These
results confirm the high multiplicity fraction, especially among massive stars
in clusters and associations. We show that the period distribution is
approximately flat in increments of log P. We identify a number of systems of
potential interest for long term orbital determinations, and we note the
importance of some of these companions for the interpretation of the radial
velocities and light curves of close binaries that have third companions.Comment: 37 pages, 4 figures, 5 tables; AJ, in press; Full version with
extended tables and large figure set can be found:
http://www.astro.umontreal.ca/~emily/fgs.pd
Theoretical study on the electronic, structural, properties and reactivity of a series of mono-, di-, tri- and tetrachlorothiophenes as well as corresponding radical cation forms as monomers for conducting polymers
In this paper, electrical and structural properties of mono-, di-, tri- and tetrachlorothiophenes and their radical cations have been studied using the density functional theory and B3LYP method with 6-311++G** basis set. The effects of the number and position of the substituent of chlorine atoms on the properties of the thiophene ring for all chlorothiophenes and their radical cations have been studied. Vibrational frequencies, nuclear chemical shielding constants, spin-density distribution, size and direction of dipole moment vector, ionization potential, electric polarizabilities and NICS values of these compounds have been calculated as well. The analysis of these data showed that double bonds in 3-chlorothiophene are more delocalized and it is the best possible candidate monomer among all chlorothiophenes for the synthesis of corresponding conducting polymers with modified characteristics
Mapping gene associations in human mitochondria using clinical disease phenotypes
Nuclear genes encode most mitochondrial proteins, and their mutations cause diverse and debilitating clinical disorders. To date, 1,200 of these mitochondrial genes have been recorded, while no standardized catalog exists of the associated clinical phenotypes. Such a catalog would be useful to develop methods to analyze human phenotypic data, to determine genotype-phenotype relations among many genes and diseases, and to support the clinical diagnosis of mitochondrial disorders. Here we establish a clinical phenotype catalog of 174 mitochondrial disease genes and study associations of diseases and genes. Phenotypic features such as clinical signs and symptoms were manually annotated from full-text medical articles and classified based on the hierarchical MeSH ontology. This classification of phenotypic features of each gene allowed for the comparison of diseases between different genes. In turn, we were then able to measure the phenotypic associations of disease genes for which we calculated a quantitative value that is based on their shared phenotypic features. The results showed that genes sharing more similar phenotypes have a stronger tendency for functional interactions, proving the usefulness of phenotype similarity values in disease gene network analysis. We then constructed a functional network of mitochondrial genes and discovered a higher connectivity for non-disease than for disease genes, and a tendency of disease genes to interact with each other. Utilizing these differences, we propose 168 candidate genes that resemble the characteristic interaction patterns of mitochondrial disease genes. Through their network associations, the candidates are further prioritized for the study of specific disorders such as optic neuropathies and Parkinson disease. Most mitochondrial disease phenotypes involve several clinical categories including neurologic, metabolic, and gastrointestinal disorders, which might indicate the effects of gene defects within the mitochondrial system. The accompanying knowledgebase (http://www.mitophenome.org/) supports the study of clinical diseases and associated genes
- …