2,635 research outputs found
A Third Planet Orbiting HIP 14810
We present new precision radial velocities and a three-planet Keplerian orbit
fit for the V = 8.5, G5 V star HIP 14810. We began observing this star at Keck
Observatory as part of the N2K Planet Search Project. Wright et al. (2007)
announced the inner two planets to this system, and subsequent observations
have revealed the outer planet planet and the proper orbital solution for the
middle planet. The planets have minimum masses of 3.9, 1.3, and 0.6 M_Jup and
orbital periods of 6.67, 147.7, and 952 d, respectively. We have numerically
integrated the family of orbital solutions consistent with the data and find
that they are stable for at least 10^6 yr. Our photometric search shows that
the inner planet does not transit.Comment: ApJL, accepte
The numerical solution of forwardâbackward differential equations: Decomposition and related issues
NOTICE: this is the authorâs version of a work that was accepted for publication in Journal of computational and applied mathematics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of computational and applied mathematics, 234,(2010), doi: 10.1016/j.cam.2010.01.039This journal article discusses the decomposition, by numerical methods, of solutions to mixed-type functional differential equations (MFDEs) into sums of âforwardâ solutions and âbackwardâ solutions
Error estimates of a high order numerical method for solving linear fractional differential equations
In this paper, we first introduce an alternative proof of the error estimates of the numerical methods for solving linear fractional differential equations proposed in Diethelm [6] where a first-degree compound quadrature formula was used to approximate the Hadamard finite-part integral and the convergence order of the proposed numerical method is O(ât 2âα ), 0 < α < 1, where α is the order of the fractional derivative and ât is the step size. We then use the similar idea to prove the error estimates of a high order numerical method for solving linear fractional differential equations proposed in Yan et al. [37], where a second-degree compound quadrature formula was used to approximate the Hadamard finite-part integral and we show that the convergence order of the numerical method is O(ât 3âα ), 0 < α < 1. The numerical examples are given to show that the numerical results are consistent with the theoretical results
Sustained effect of caftopril on the attenuation of infarct expansion following acute myocardial infarction
Prognostic implications of left ventricular global longitudinal strain in heart failure patients with narrow QRS complex treated with cardiac resynchronization therapy: a subanalysis of the randomized EchoCRT trial
Aim:
Left ventricular (LV) global longitudinal strain (GLS) reflects LV systolic function and correlates inversely with the extent of LV myocardial scar and fibrosis. The present subanalysis of the Echocardiography Guided CRT trial investigated the prognostic value of LV GLS in patients with narrow QRS complex.
Methods and results:
Left ventricular (LV) global longitudinal strain (GLS) was measured on the apical 2-, 4- and 3-chamber views using speckle tracking analysis. Measurement of baseline LV GLS was feasible in 755 patients (374 with cardiac resynchronization therapy (CRT)-ON and 381 with CRT-OFF). The median value of LV GLS in the overall population was 7.9%, interquartile range 6.2â10.1%. After a mean follow-up period of 19.4 months, 95 patients in the CRT-OFF group and 111 in the CRT-ON group reached the combined primary endpoint of all-cause mortality and heart failure hospitalization. Each 1% absolute unit decrease in LV GLS was independently associated with 11% increase in the risk to reach the primary endpoint (Hazard ratio 1.11; 95% confidence interval 95% 1.04â1.17, Pâ<â0.001), after adjusting for ischaemic cardiomyopathy and randomization treatment among other clinically relevant variables. When categorizing patients according to quartiles of LV GLS, the primary endpoint occurred more frequently in patients in the lowest quartile (<6.2%) treated with CRT-ON vs. CRT-OFF (45.6% vs. 28.7%, Pâ=â0.009) whereas, no differences were observed in patients with LV GLSââ„6.2% treated with CRT-OFF vs. CRT-ON (23.7% vs. 24.5%, respectively; P â=â0.62).
Conclusion:
Low LV GLS is associated with poor outcome in heart failure patients with QRS widthâ<130âms, independent of randomization to CRT or not. Importantly, in the group of patients with the lowest LV GLS quartile, CRT may have a detrimental effect on clinical outcomes
Near-Infrared Thermal Emission from the Hot Jupiter TrES-2b: Ground-Based Detection of the Secondary Eclipse
We present near-infrared Ks-band photometry bracketing the secondary eclipse
of the hot Jupiter TrES-2b using the Wide-field Infrared Camera on the
Canada-France-Hawaii Telescope. We detect its thermal emission with an eclipse
depth of 0.062 +/- 0.012% (5-sigma). Our best-fit secondary eclipse is
consistent with a circular orbit (a 3-sigma upper limit on the eccentricity, e,
and argument or periastron, omega, of |ecos(omega)| < 0.0090), in agreement
with mid-infrared detections of the secondary eclipse of this planet. A
secondary eclipse of this depth corresponds to a day-side Ks-band brightness
temperature of TB = 1636 +/- 88 K. Our thermal emission measurement when
combined with the thermal emission measurements using Spitzer/IRAC from
O'Donovan and collaborators suggest that this planet exhibits relatively
efficient day to night-side redistribution of heat and a near isothermal
dayside atmospheric temperature structure, with a spectrum that is well
approximated by a blackbody. It is unclear if the atmosphere of TrES-2b
requires a temperature inversion; if it does it is likely due to chemical
species other than TiO/VO as the atmosphere of TrES-2b is too cool to allow
TiO/VO to remain in gaseous form. Our secondary eclipse has the smallest depth
of any detected from the ground at around 2 micron to date.Comment: ApJ accepted, 8 pages, 9 figures, in emulateapj format
Authenticated private information retrieval
This paper introduces protocols for authenticated private information retrieval. These schemes enable a client to fetch a record from a remote database server such that (a) the server does not learn which record the client reads, and (b) the client either obtains the authentic record or detects server misbehavior and safely aborts. Both properties are crucial for many applications. Standard private-information-retrieval schemes either do not ensure this form of output authenticity, or they require multiple database replicas with an honest majority. In contrast, we offer multi-server schemes that protect security as long as at least one server is honest. Moreover, if the client can obtain a short digest of the database out of band, then our schemes require only a single server. Performing an authenticated private PGP-public-key lookup on an OpenPGP key server\u27s database of 3.5 million keys (3 GiB), using two non-colluding servers, takes under 1.2 core-seconds of computation, essentially matching the time taken by unauthenticated private information retrieval. Our authenticated single-server schemes are 30-100 more costly than state-of-the-art unauthenticated single-server schemes, though they achieve incomparably stronger integrity properties
New observations of the extended hydrogen exosphere of the extrasolar planet HD209458b
Atomic hydrogen escaping from the planet HD209458b provides the largest
observational signature ever detected for an extrasolar planet atmosphere.
However, the Space Telescope Imaging Spectrograph (STIS) used in previous
observational studies is no longer available, whereas additional observations
are still needed to better constrain the mechanisms subtending the evaporation
process, and determine the evaporation state of other `hot Jupiters'. Here, we
aim to detect the extended hydrogen exosphere of HD209458b with the Advanced
Camera for Surveys (ACS) on board the Hubble Space Telescope (HST) and to find
evidence for a hydrogen comet-like tail trailing the planet, which size would
depend on the escape rate and the amount of ionizing radiation emitted by the
star. These observations also provide a benchmark for other transiting planets,
in the frame of a comparative study of the evaporation state of close-in giant
planets. Eight HST orbits are used to observe two transits of HD209458b.
Transit light curves are obtained by performing photometry of the unresolved
stellar Lyman-alpha emission line during both transits. Absorption signatures
of exospheric hydrogen during the transit are compared to light curve models
predicting a hydrogen tail. Transit depths of (9.6 +/- 7.0)% and (5.3 +/-
10.0)% are measured on the whole Lyman-alpha line in visits 1 and 2,
respectively. Averaging data from both visits, we find an absorption depth of
(8.0 +/- 5.7)%, in good agreement with previous studies. The extended size of
the exosphere confirms that the planet is likely loosing hydrogen to space.
Yet, the photometric precision achieved does not allow us to better constrain
the hydrogen mass loss rate.Comment: Accepted for publication in Astronomy & Astrophysics. 5 pages, 3
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