1,390 research outputs found
The Quiescent Spectrum of the AM CVn star CP Eri
We used the 6.5m MMT to obtain a spectrum of the AM CVn star CP Eri in
quiescence. The spectrum is dominated by He I emission lines, which are clearly
double peaked with a peak-to-peak separation of ~1900 km/s. The spectrum is
similar to that of the longer period AM CVn systems GP Com and CE 315, linking
the short and the long period AM CVn systems. In contrast with GP Com and CE
315, the spectrum of CP Eri does not show a central 'spike' in the line
profiles, but it does show lines of SiII in emission. The presence of these
lines indicates that the material being transferred is of higher metallicity
than in GP Com and CE 315, which, combined with the low proper motion of the
system, probably excludes a halo origin of the progenitor of CP Eri. We
constrain the primary mass to M_1>0.27 M_sun and the orbital inclination to 33
degr < i < 80 degr. The presence of the He I lines in emission opens up the
possibility for phase resolved spectroscopic studies which allows a
determination of the system parameters and a detailed study of helium accretion
disks under highly varying circumstances.Comment: 12 pages, 2 figures, accepted for publication in ApJ Letter
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Response to “The Humble Heart”
You are a child of the universe, no less than the trees and the stars; you have a right to be here. And whether or not it is clear to you, no doubt the universe is unfolding as it should. Therefore, be at peace with God, whatever you conceive God to be, and whatever your labors and aspirrations, in the noisy confusion of life, keep peace with your soul. With all its sham, drudgery and broken dreams, it is still a beautiful world. Be careful. Strive to be happy.
—Max Ehrmann, Desiderata
In my introductory astronomy course for non-science majors, I always have students who take the course because it’s the least abhorrent science class they can find. These students have been convinced by their previous education that they "can’t do" science and math. Though they are bright, articulate and accomplished and have earned their place in a selective liberal arts college, they’re convinced that they lack some special neural connections or chemical transmitters to understand information and arguments that happen to fall under the broad umbrella of science. My course is designed for these students and all but a very few succeed. On the last day, after we have spent the semester working through calculations of the luminosities, temperatures and sizes of stars and the distances to galaxies, I give them Desiderata. I focus on the fact that they are children of the universe and they belong here. Humans are not something artificial plunked down on Earth. We are part of it. We are Earth’s mind and voice. I review how they have come to exist, from the earliest moments of the Big Bang creating the protons and neutrons in every atom in their bodies, through a couple generations of stars fusing primordial hydrogen and helium into the carbon, calcium, nitrogen and oxygen in their skin, bones and breath; the explosive deaths of giant stars creating the iron carrying oxygen to their brains, the iodine regulating their metabolisms and the gold and silver shining in their jewelry; half a billion years of biological evolution giving them arms, legs and brains and ten thousand years of cultural evolution giving them a university
KUV 01584-0939: A Helium-transferring Cataclysmic Variable with an Orbital Period of 10 Minutes
High speed photometry of KUV 01584-0939 (alias Cet3) shows that is has a
period of 620.26 s. Combined with its hydrogen-deficient spectrum, this implies
that it is an AM CVn star. The optical modulation is probably a superhump, in
which case the orbital period will be slightly shorter than what we have
observed.Comment: Published by PASP. See also the latest Early-Release Research Paper
website of the PAS
Understanding thio-effects in simple phosphoryl systems : role of solvent effects and nucleophile charge.
Recent experimental work (J. Org. Chem., 2012, 77, 5829) demonstrated pronounced differences in measured thio-effects for the hydrolysis of (thio)phosphodichloridates by water and hydroxide nucleophiles. In the present work, we have performed detailed quantum chemical calculations of these reactions, with the aim of rationalizing the molecular bases for this discrimination. The calculations highlight the interplay between nucleophile charge and transition state solvation in SN2(P) mechanisms as the basis of these differences, rather than a change in mechanism
Electron Population Aging Models for Wide-Angle Tails
Color-color diagrams have been useful in studying the spectral shapes in
radio galaxies. At the workshop we presented color-color diagrams for two
wide-angle tails, 1231+674 and 1433+553, and found that the standard aging
models do not adequately represent the observed data. Although the JP and KP
models can explain some of the observed points in the color-color diagram, they
do not account for those found near the power-law line. This difficulty may be
attributable to several causes. Spectral tomography has been previously used to
discern two separate electron populations in these sources. The combination
spectra from two such overlying components can easily resemble a range of
power-laws. In addition, any non-uniformity in the magnetic field strength can
also create a power-law-like spectrum. We will also discuss the effects that
angular resolution has on the shape of the spectrum.Comment: 4 pages, 1 figure, proceedings from 1999 'Life Cycles of Radio
Galaxies' workshop at STScI in Baltimore, M
Blockchain vehicles for efficient Medical Record management
The lack of interoperability in Britain’s medical records systems precludes the realisation of benefits generated by increased spending elsewhere in healthcare. Growing concerns regarding the security of online medical data following breaches, and regarding regulations governing data ownership, mandate strict parameters in the development of efficient methods to administrate medical records. Furthermore, consideration must be placed on the rise of connected devices, which vastly increase the amount of data that can be collected in order to improve a patient’s long-term health outcomes. Increasing numbers of healthcare systems are developing Blockchain-based systems to manage medical data. A Blockchain is a decentralised, continuously growing online ledger of records, validated by members of the network. Traditionally used to manage cryptocurrency records, distributed ledger technology can be applied to various aspects of healthcare. In this manuscript, we focus on how Electronic Medical Records in particular can be managed by Blockchain, and how the introduction of this novel technology can create a more efficient and interoperable infrastructure to manage records that leads to improved healthcare outcomes, while maintaining patient data ownership and without compromising privacy or security of sensitive data
Understanding Thio-Effects in Simple Phosphoryl Systems: Role of Solvent Effects and Nucleophile Charge
Recent experimental work (J. Org. Chem., 2012, 77, 5829) demonstrated pronounced differences in measured thio-effects for the hydrolysis of (thio)phosphodichloridates by water and hydroxide nucleophiles. In the present work, we have performed detailed quantum chemical calculations of these reactions, with the aim of rationalizing the molecular bases for this discrimination. The calculations highlight the interplay between nucleophile charge and transition state solvation in SN2(P) mechanisms as the basis of these differences, rather than a change in mechanism
The Helium-Rich Cataclysmic Variable ES Ceti
We report photometry of the helium-rich cataclysmic variable ES Ceti during
2001-2004. The star is roughly stable at V ~ 17.0 and has a light curve
dominated by a single period of 620 s, which remains measurably constant over
the 3 year baseline. The weight of evidence suggests that this is the true
orbital period of the underlying binary, not a "superhump" as initially
assumed. We report GALEX ultraviolet magnitudes, which establish a very blue
flux distribution (F_nu ~ nu^1.3), and therefore a large bolometric correction.
Other evidence (the very strong He II 4686 emission, and a ROSAT detection in
soft X-rays) also indicates a strong EUV source, and comparison to
helium-atmosphere models suggests a temperature of 130+-10 kK. For a distance
of 350 pc, we estimate a luminosity of (0.8-1.7)x10^34 erg/s, yielding a mass
accretion rate of (2-4)x10^-9 M_sol/yr onto an assumed 0.7 M_sol white dwarf.
This appears to be about as expected for white dwarfs orbiting each other in a
10 minute binary, assuming that mass transfer is powered by gravitational
radiation losses. We estimate mean accretion rates for other helium-rich
cataclysmic variables, and find that they also follow the expected M-dot ~
P_o^-5 relation. There is some evidence (the lack of superhumps, and the small
apparent size of the luminous region) that the mass transfer stream in ES Cet
directly strikes the white dwarf, rather than circularizing to form an
accretion disk.Comment: PDF, 26 pages, 3 tables, 9 figures; accepted, in press, to appear
February 2005, PASP; more info at http://cba.phys.columbia.edu
Neurocognitive factors in sensory restoration of early deafness: a connectome model
Progress in biomedical technology (cochlear, vestibular, and retinal implants) has led to remarkable success in neurosensory restoration, particularly in the auditory system. However, outcomes vary considerably, even after accounting for comorbidity-for example, after cochlear implantation, some deaf children develop spoken language skills approaching those of their hearing peers, whereas other children fail to do so. Here, we review evidence that auditory deprivation has widespread effects on brain development, affecting the capacity to process information beyond the auditory system. After sensory loss and deafness, the brain's effective connectivity is altered within the auditory system, between sensory systems, and between the auditory system and centres serving higher order neurocognitive functions. As a result, congenital sensory loss could be thought of as a connectome disease, with interindividual variability in the brain's adaptation to sensory loss underpinning much of the observed variation in outcome of cochlear implantation. Different executive functions, sequential processing, and concept formation are at particular risk in deaf children. A battery of clinical tests can allow early identification of neurocognitive risk factors. Intervention strategies that address these impairments with a personalised approach, taking interindividual variations into account, will further improve outcomes
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