609 research outputs found
Spectroscopic study of early-type multiple stellar systems II. New binary subsystems
Context. This work is part of a long-term spectroscopic study of a sample of
30 multiple stars with early-type components. In this second paper we present
the results of six multiple systems in which new stellar components have been
detected.
Aims. The main aim is to increase the knowledge of stellar properties and
dynamical structure of early-type multiple stellar systems.
Methods. Using spectroscopic observations taken over a time baseline of more
than 5 years we measured RVs by cross-correlations and applied a spectral
disentangling method to double-lined systems. Besides the discovery of objects
with double-lined spectra, the existence of new spectroscopic subsystems have
been inferred from the radial velocity variations of single-lined components
and through the variation of the barycentric velocity of double-lined
subsystems. Orbital elements have been calculated when possible.
Results. Seven new stellar components and two members that we expect to
confirm with new observations have been discovered in the six studied
multiples. We present orbital parameters for two double-lined binaries and
preliminary orbits for three single-lined spectroscopic binaries. Five of the
six analysed systems are quadruples, while the remaining has five components
distributed in four hierarchical levels. These multiplicity orders are in fact
lower limits, since these systems lack high-resolution visual observations and
additional hierarchical level might exist in that separation range.
Conclusions. The six analysed systems have greater multiplicity degree and a
more complex hierarchical structure than previously known, which suggests that
high-order multiple systems are significantly more frequent that it is
currently estimated. The long term spectroscopic monitoring of multiple systems
has shown to be useful for the detection of companions in intermediate
hierarchical levels.Comment: 13 pages, 9 figures. Accepted by Astronomy and Astrophysic
Dynamical detection of three triple stellar systems in open clusters
We present a kinematic analysis of three triple stellar systems belonging to
two open clusters: CPD-60{\deg}961 and HD66137 in NGC2516, and HD315031 in
NGC6530. All three systems are hierarchical triples with a close binary bound
to a third body in a wider orbit, whose presence is detected through velocity
variations of the close binary barycentre. Orbital parameters are derived from
radial velocity curves. Absolute parameters for all stars are estimated
assuming cluster membership. Some dynamical and evolutionary aspects of these
systems are discussed, particularly the possible influence of Kozai cycles. The
two systems of NGC2516 have similar orbital configurations with inner periods
of 11.23 d and 8.70 d and outer periods of 9.79 yr and 9.24 yr. We report also
radial velocity measurements of the components of the visual binary
CPD-60{\deg}944 in NGC2516. Including results from previous works, this cluster
would harbor 5 hierarchical triples. The young system HD315031 has an inner
binary with a period of 1.37 d and a very eccentric (e=0.85) outer orbit with a
period of 483 d. Possible dynamical evolutionary scenarios are discussed.
Long-term radial velocity monitoring is highlighted as strategy for the
detection of subsystems with intermediate separations, which are hard to cover
with normal spectroscopic studies or visual techniques.Comment: 9 pages, 5 figures. Accepted by Monthly Notices of the Royal
Astronomical Societ
The effects of educational choices on labor market, health, and social outcomes
Using a sequential model of educational choices, we investigate the effect of educational choices on labor market, health, and social outcomes. Unobserved endowments drive the correlations in unobservables across choice and outcome equations. We proxy these endowments with numerous measurements and account for measurement error in the proxies. For each schooling level, we estimate outcomes for labor market, health, and social outcome. This allows us to generate counter-factual outcomes for dynamic choices and a variety of policy and treatment effects. In our framework, responses to treatment vary among observationally identical persons and agents may select into the treatment on the basis of their responses. We find important effects of early cognitive and socio-emotional abilities on schooling choices, labor market outcomes, adult health, and social outcomes. Education at most levels causally produces gains on labor market, health, and social outcomes. We estimate the distribution of responses to education and find substantial heterogeneity on which agents act.
Functional Improvement of Human Cardiotrophin 1 Produced in Tobacco Chloroplasts by Co-Expression with Plastid Thioredoxin m
Human cardiotrophin 1 (CT1), a cytokine with excellent therapeutic potential,
was previously expressed in tobacco chloroplasts. However, the growth conditions required to
reach the highest expression levels resulted in an impairment of its bioactivity. In the present
study, we have examined new strategies to modulate the expression of this recombinant protein in
chloroplasts so as to enhance its production and bioactivity. In particular, we assessed the effect of both
the fusion and co-expression of Trx m with CT1 on the production of a functional CT1 by using plastid
transformation. Our data revealed that the Trx m fusion strategy was useful to increase the expression
levels of CT1 inside the chloroplasts, although CT1 bioactivity was significantly impaired, and this
was likely due to steric hindrance between both proteins. By contrast, the expression of functional
CT1 was increased when co-expressed with Trx m, because we demonstrated that recombinant
CT1 was functionally active during an in vitro signaling assay. While Trx m/CT1 co-expression did not
increase the amount of CT1 in young leaves, our results revealed an increase in CT1 protein stability as
the leaves aged in this genotype, which also improved the recombinant protein’s overall production.
This strategy might be useful to produce other functional biopharmaceuticals in chloroplasts
Search for Narrow Diphoton Resonances and for gamma-gamma+W/Z Signatures in p\bar p Collisions at sqrt(s)=1.8 TeV
We present results of searches for diphoton resonances produced both
inclusively and also in association with a vector boson (W or Z) using 100
pb^{-1} of p\bar p collisions using the CDF detector. We set upper limits on
the product of cross section times branching ratio for both p\bar
p\to\gamma\gamma + X and p\bar p\to\gamma\gamma + W/Z. Comparing the inclusive
production to the expectations from heavy sgoldstinos we derive limits on the
supersymmetry-breaking scale sqrt{F} in the TeV range, depending on the
sgoldstino mass and the choice of other parameters. Also, using a NLO
prediction for the associated production of a Higgs boson with a W or Z boson,
we set an upper limit on the branching ratio for H\to\gamma\gamma. Finally, we
set a lower limit on the mass of a `bosophilic' Higgs boson (e.g. one which
couples only to \gamma, W, and Z$ bosons with standard model couplings) of 82
GeV/c^2 at 95% confidence level.Comment: 30 pages, 11 figure
Measurement of the Strong Coupling Constant from Inclusive Jet Production at the Tevatron Collider
We report a measurement of the strong coupling constant, ,
extracted from inclusive jet production in collisions at
1800 GeV. The QCD prediction for the evolution of with
jet transverse energy is tested over the range 40<<450 GeV using
for the renormalization scale. The data show good agreement with QCD in
the region below 250 GeV. In the text we discuss the data-theory comparison in
the region from 250 to 450 GeV. The value of at the mass of the
boson averaged over the range 40<<250 GeV is found to be
. The associated theoretical uncertainties are mainly due to the choice
of renormalization scale (^{+6%}_{-4%}) and input parton distribution
functions (5%).Comment: 7 pages, 3 figures, using RevTeX. Submitted to Physical Review
Letter
Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV
We report on a search for anomalous production of events with at least two
charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1
sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a
signal region containing low background from Standard Model processes. To avoid
bias, we fix the final cuts before examining the event yield in the signal
region using control regions to test the Monte Carlo predictions. We observe no
events in the signal region, consistent with an expectation of
0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new
physics processes in both a signature-based context as well as within a
representative minimal supergravity (tanbeta = 3) model.Comment: 15 pages, 4 figures. Minor textual changes, cosmetic improvements to
figures and updated and expanded reference
- …