3,088 research outputs found
BCG vaccination and leprosy protection: review of current evidence and status of BCG in leprosy control.
The bacillus Calmette-Guérin (BCG) vaccine, initially developed to provide protection against TB, also protects against leprosy; and the magnitude of this effect varies. Previous meta-analyses did not provide a summary estimate of the efficacy due to the heterogeneity of the results. We conducted a meta-analysis of published data including recently published studies (up to June 2009) to determine the efficacy of BCG protection on leprosy and to investigate whether age at vaccination, clinical form, number of doses, type of study, the latitude of study area and year of publication influence the degree of efficacy and explain the variation. In the light of the results, we argue for more emphasis on the role of BCG vaccination in leprosy control and research
Reliability analysis of dynamic systems by translating temporal fault trees into Bayesian networks
Classical combinatorial fault trees can be used to assess combinations of failures but are unable to capture sequences of faults, which are important in complex dynamic systems. A number of proposed techniques extend fault tree analysis for dynamic systems. One of such technique, Pandora, introduces temporal gates to capture the sequencing of events and allows qualitative analysis of temporal fault trees. Pandora can be easily integrated in model-based design and analysis techniques. It is, therefore, useful to explore the possible avenues for quantitative analysis of Pandora temporal fault trees, and we identify Bayesian Networks as a possible framework for such analysis. We describe how Pandora fault trees can be translated to Bayesian Networks for dynamic dependability analysis and demonstrate the process on a simplified fuel system model. The conversion facilitates predictive reliability analysis of Pandora fault trees, but also opens the way for post-hoc diagnostic analysis of failures
Spectroscopic binaries among AGB stars from HERMES/Mercator: the case of V Hya
We report on our search for spectroscopic binaries among a sample of AGB
stars. Observations were carried out in the framework of the monitoring of
radial velocities of (candidate) binary stars performed at the Mercator 1.2m
telescope, using the HERMES spectrograph. We found evidence for duplicity in UV
Cam, TU Tau, BL Ori, VZ Per, T Dra, and V Hya. This short communication focus
on V Hya, found to behave like RV Tau of the b subtype, which are binaries
surrounded by a disc.Comment: Poster presented at IAU Symp. 343 "Why Galaxies Care About AGB
Stars", Vienna, august 201
An Experimental determination of freeplay and its effect on modal complexity and damping
This experiment is designed to address the effects of joint related nonlinearities on system parameters. Specifically, the effects of freeplay on the natural frequency, damping, and modal complexity. Many modal analysis techniques assume a system exhibits linear properties that are time invariant. Large structures are commonly constructed with several pinned and bolted joints and these joints can lead to gap and frictional-type nonlinearities. Joint nonlinearities will result in exaggerated damping estimates and complex time-varying mode shapes. These characteristics will result in incorrect modal parameter estimation when estimation assumes linearity. The experiment\u27s intent is to examine nonlinearities and indicate methods of estimating the amount of nonlinearity and the degree of looseness, of a joint, associated with the nonlinearity. A real system, constructed of masses, springs, and viscoelastic components will be tested to arrive at these results. The results of this experiment indicated that it is possible to identify freeplay in the system. In addition to this, a new method of determining a system\u27s degree of nonlinearity was developed
Annual cycle of subsurface thermal structure in the Tropical Atlantic ocean
The subsurface thermal structure in the Tropical Atlantic ocean (30°N-20°S, East of 80°W) is studied on the basis of an extensive data bank of subsurface soundings. Calendar monthly maps are presented showing mixed layer depth, base of thermocline, thermocline thickness, and vertical temperature gradient across the thermocline. These maps are complemented by vertical cross sections depicting mixed layer depth, base of thermocline, and selected isotherms : a zonal profile along the equator (50°W-10°E), a meridional transect across the Eastern Atlantic (4°N-18°S), and a meridional section across the Central Atlantic (30°N-18°S). (D'après résumé d'auteur
Tomography of the red supergiant star {\mu} Cep
A tomographic method, aiming at probing velocity fields at depth in stellar
atmospheres, is applied to the red supergiant star {\mu} Cep and to snapshots
of 3D radiative-hydrodynamics simulation in order to constrain atmospheric
motions and relate them to photometric variability.Comment: 2 pages, 2 figures, accepted as Proceedings of IAU Symposium No. 343,
201
IP Eri: A surprising long-period binary system hosting a He white dwarf
We determine the orbital elements for the K0 IV + white dwarf (WD) system IP
Eri, which appears to have a surprisingly long period of 1071 d and a
significant eccentricity of 0.25. Previous spectroscopic analyses of the WD,
based on a distance of 101 pc inferred from its Hipparcos parallax, yielded a
mass of only 0.43 M, implying it to be a helium-core WD. The orbital
properties of IP Eri are similar to those of the newly discovered long-period
subdwarf B star (sdB) binaries, which involve stars with He-burning cores
surrounded by extremely thin H envelopes, and are therefore close relatives to
He WDs. We performed a spectroscopic analysis of high-resolution spectra from
the HERMES/Mercator spectrograph and concluded that the atmospheric parameters
of the K0 component are K, , [Fe/H] = 0.09
and km/s. The detailed abundance analysis focuses on C, N, O
abundances, carbon isotopic ratio, light (Na, Mg, Al, Si, Ca, Ti) and s-process
(Sr, Y, Zr, Ba, La, Ce, Nd) elements. We conclude that IP Eri abundances agree
with those of normal field stars of the same metallicity. The long period and
non-null eccentricity indicate that this system cannot be the end product of a
common-envelope phase; it calls instead for another less catastrophic
binary-evolution channel presented in detail in a companion paper (Siess et al.
2014).Comment: 14 pages, 10 figures, 4 tables, accepted for publication in A&A
(Update of Table 3, Fig. 8 and text in Sect. 5.1, 5.3 and 6 due to minor
corrections on N and Y II
Radiative Inflation and Dark Energy
We propose a model based on radiative symmetry breaking that combines
inflation with Dark Energy and is consistent with the WMAP 7-year regions. The
radiative inflationary potential leads to the prediction of a spectral index
0.955 \lesssim n_S \lesssim 0.967 and a tensor to scalar ratio 0.142 \lesssim r
\lesssim 0.186, both consistent with current data but testable by the Planck
experiment. The radiative symmetry breaking close to the Planck scale gives
rise to a pseudo Nambu-Goldstone boson with a gravitationally suppressed mass
which can naturally play the role of a quintessence field responsible for Dark
Energy. Finally, we present a possible extra dimensional scenario in which our
model could be realised.Comment: 15 pages, 4 figures; v2: references added, appendix added, Section 5
slightly modified; content matches published versio
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