119 research outputs found
Identifying and troubleshooting low-frequency artifacts mimicking atrial flutter caused by deep brain stimulator
Electromagnetic interference from deep brain stimulators (DBS) is known to cause high-frequency artifact on some forms of cardiac telemetry.1 Here, we (1) present a unique case in which a DBS caused a low-frequency artifact mimicking typical atrial flutter leading to referral to electrophysiology; (2) demonstrate a method to confirm this; and (3) provide recommendations of how to minimize artifact and work around this interaction in future rhythm monitoring attempts
Multi-wavelength diagnostics of accretion in an X-ray selected sample of CTTSs
High resolution X-ray spectroscopy has revealed soft X-rays from high density
plasma in Classical T-Tauri stars (CTTSs), probably arising from the accretion
shock region. However, the mass accretion rates derived from the X-ray
observations are consistently lower than those derived from UV/optical/NIR
studies. We aim to test the hypothesis that the high density soft X-ray
emission is from accretion by analysing optical accretion tracers from an X-ray
selected sample of CTTSs in a homogeneous manner. We analyse optical spectra of
a sample of CTTSs and calculate the accretion rates based on measuring optical
emission lines. These are then compared to the accretion rates derived from the
X-ray spectroscopy. We find that, for each CTTS in our sample, the different
optical tracers predict mass accretion rates that agree within the errors,
albeit with a spread of ~1 order of magnitude. Typically, mass accretion rates
derived from Halpha and HeI 5876 Ang are larger than those derived from Hbeta,
Hgamma and OI. When comparisons of the optical mass accretion rates are made to
the X-ray derived mass accretion rates, we find that: a) the latter are always
lower (but by varying amounts); b) the latter range within a factor of ~2
around 2x10^{-10} M_odot yr^{-1}, despite the fact that the former span a range
of ~3 orders of magnitude. We suggest that the systematic underestimation of
the X-ray derived mass accretion rates could depend on the density distribution
inside the accretion streams, where the densest part of the stream is not
visible in the X-ray band because of the absorption by the stellar atmosphere.
We also suggest that a non-negligible optical depth of X-ray emission lines
produced by post-shock accreting plasma may explain the almost constant mass
accretion rates derived in X-rays if the effect is larger in stars with larger
optical mass accretion rates.Comment: 12 pages, 4 figures. Accepted for publication by A&
A Chandra Observation of the Obscured Star-Forming Complex W40
The young stellar cluster illuminating the W40 H II region, one of the
nearest massive star forming regions, has been observed with the ACIS detector
on board the Chandra X-ray Observatory. Due to its high obscuration, this is a
poorly-studied stellar cluster with only a handful of bright stars visible in
the optical band, including three OB stars identified as primary excitation
sources. We detect 225 X-ray sources, of which 85% are confidently identified
as young stellar members of the region. Two potential distances of the cluster,
260 pc and 600 pc, are used in the paper. Supposing the X-ray luminosity
function to be universal, it supports a 600 pc distance as a lower limit for
W40 and a total population of at least 600 stars down to 0.1 Mo under the
assumption of a coeval population with a uniform obscuration. In fact, there is
strong spatial variation in Ks-band-excess disk fraction and non-uniform
obscuration due to a dust lane that is identified in absorption in optical,
infrared and X-ray. The dust lane is likely part of a ring of material which
includes the molecular core within W40. In contrast to the likely ongoing star
formation in the dust lane, the molecular core is inactive. The star cluster
has a spherical morphology, an isothermal sphere density profile, and mass
segregation down to 1.5 Mo. However, other cluster properties, including a
\leq{1} Myr age estimate and ongoing star formation, indicate that the cluster
is not dynamically relaxed. X-ray diffuse emission and a powerful flare from a
young stellar object are also reported.Comment: Accepted for publication in The Astrophysical Journal. 60 pages, 16
figure
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Leo Strauss and International Relations: The politics of modernity's abyss
This article argues that an engagement with the political philosophy of Leo Strauss is of considerable value in International Relations (IR), in relation to the study of both recent US foreign policy and contemporary IR theory. The question of Straussian activities within and close to the foreign policy-making establishment in the United States during the period leading up to the 2003 invasion of Iraq has been the focus of significant scholarly and popular attention in recent years. This article makes the case that several individuals influenced by Strauss exercised considerable influence in the fields of intelligence production, the media and think tanks, and traces the ways in which elements of Strauss’ thought are discernible in their interventions in these spheres. It further argues that Strauss’ political philosophy is of broader significance for IR insofar as it can be read as a securitising response to the dangers he associated with the foundationlessness of the modern condition. The article demonstrates that the politics of this response are of crucial importance for contemporary debates between traditional and critical IR theorists
Climate change and freshwater zooplankton: what does it boil down to?
Recently, major advances in the climate–zooplankton interface have been made some of which appeared to receive much attention in a broader audience of ecologists as well. In contrast to the marine realm, however, we still lack a more holistic summary of recent knowledge in freshwater. We
discuss climate change-related variation in physical and biological attributes of lakes and running waters, high-order ecological functions, and subsequent alteration
in zooplankton abundance, phenology, distribution, body size, community structure, life history parameters, and behavior by focusing on community level responses. The adequacy of large-scale climatic indices in ecology has received considerable support and provided a framework for the interpretation of community and species level responses in freshwater zooplankton. Modeling perspectives deserve particular consideration, since this promising stream of
ecology is of particular applicability in climate change
research owing to the inherently predictive nature of
this field. In the future, ecologists should expand their
research on species beyond daphnids, should address
questions as to how different intrinsic and extrinsic
drivers interact, should move beyond correlative
approaches toward more mechanistic explanations,
and last but not least, should facilitate transfer of
biological data both across space and time
Search for Lepton Flavor Violation in Upsilon Decays Forward-Backward Asymmetry in Top-Quark Production in p(p)over-bar Collisions at root s=1.96 TeV
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