376 research outputs found
The puzzlingly large Ca II triplet absorption in dwarf elliptical galaxies
We present central CaT, PaT, and CaT* indices for a sample of fifteen dwarf
elliptical galaxies (dEs). Twelve of these have CaT* ~ 7 A and extend the
negative correlation between the CaT* index and central velocity dispersion
sigma, which was derived for bright ellipticals (Es), down to 20 < sigma < 55
km/s. For five dEs we have independent age and metallicity estimates. Four of
these have CaT* ~ 7 A, much higher than expected from their low metallicities
(-1.5 < [Z/H] < -0.5). The observed anti-correlation of CaT* as a function of
sigma or Z is in flagrant disagreement with theory. We discuss some of the
amendments that have been proposed to bring the theoretical predictions into
agreement with the observed CaT*-values of bright Es and how they can be
extended to incorporate also the observed CaT*-values of dEs. Moreover, 3 dEs
in our sample have CaT* ~ 5 A, as would be expected for metal-poor stellar
systems. Any theory for dE evolution will have to be able to explain the
co-existence of low-CaT* and high-CaT* dEs at a given mean metallicity. This
could be the first direct evidence that the dE population is not homogeneous,
and that different evolutionary paths led to morphologically and kinematically
similar but chemically distinct objects.Comment: 4 pages, 3 figures, accepted for publication in ApJ Letter
Possible Experience: from Boole to Bell
Mainstream interpretations of quantum theory maintain that violations of the
Bell inequalities deny at least either realism or Einstein locality. Here we
investigate the premises of the Bell-type inequalities by returning to earlier
inequalities presented by Boole and the findings of Vorob'ev as related to
these inequalities. These findings together with a space-time generalization of
Boole's elements of logic lead us to a completely transparent Einstein local
counterexample from everyday life that violates certain variations of the Bell
inequalities. We show that the counterexample suggests an interpretation of the
Born rule as a pre-measure of probability that can be transformed into a
Kolmogorov probability measure by certain Einstein local space-time
characterizations of the involved random variables.Comment: Published in: EPL, 87 (2009) 6000
Classical and Quantum Annealing in the Median of Three Satisfiability
We determine the classical and quantum complexities of a specific ensemble of
three-satisfiability problems with a unique satisfying assignment for up to
N=100 and N=80 variables, respectively. In the classical limit we employ
generalized ensemble techniques and measure the time that a Markovian Monte
Carlo process spends in searching classical ground states. In the quantum limit
we determine the maximum finite correlation length along a quantum adiabatic
trajectory determined by the linear sweep of the adiabatic control parameter in
the Hamiltonian composed of the problem Hamiltonian and the constant transverse
field Hamiltonian. In the median of our ensemble both complexities diverge
exponentially with the number of variables. Hence, standard, conventional
adiabatic quantum computation fails to reduce the computational complexity to
polynomial. Moreover, the growth-rate constant in the quantum limit is 3.8
times as large as the one in the classical limit, making classical fluctuations
more beneficial than quantum fluctuations in ground-state searches
Towards a Solution for the Ca II Triplet Puzzle : Results from Dwarf Elliptical Galaxies
We present new estimates of ages and metallicities, based on FORS/VLT optical
(4400-5500A) spectroscopy, of 16 dwarf elliptical galaxies (dE's) in the Fornax
Cluster and in Southern Groups. These dE's are more metal-rich and younger than
previous estimates based on narrow-band photometry and low-resolution
spectroscopy. For our sample we find a mean metallicity [Z/H] = -0.33 dex and
mean age 3.5 Gyr, consistent with similar samples of dE's in other environments
(Local Group, Virgo). Three dE's in our sample show emission lines and very
young ages. This suggests that some dE's formed stars until a very recent epoch
and were self-enriched by a long star formation history. Previous observations
of large near-infrared (~8500A) Ca II absorption strengths in these dE's are in
good agreement with the new metallicity estimates, solving part of the
so-called Calcium puzzle.Comment: ApJ Letters accepted, 5 pages emulateapj, 2 figure
Marching to a different drummer : a cross-cultural comparison of young adolescents who challenge gender norms
Purpose: Little is known about how gender norms regulate adolescents' lives across different cultural settings. This study aims to illustrate what is considered as violating gender norms for boys and girls in four urban poor sites as well as the consequences that follow the challenging of gender norms.
Methods: Data were collected as part of the Global Early Adolescent Study, a 15-country collaboration to explore gender norms and health in early adolescence. The current study analyzed narrative and in-depth interviews conducted in urban poor sites in two middle-income (Shanghai, China; and New Delhi, India) and two high-income countries (Baltimore, U.S.; and Ghent, Belgium). A total of 238 participants, 59 boys and 70 girls aged 11-13 years old and 109 of their parents/guardians (28 male adults and 81 female adults), were interviewed. A thematic analysis was conducted across sites using Atlas. Ti 7.5 software.
Results: Findings revealed that although most perceptions and expressions about gender were regulated by stereotypical norms, there was a growing acceptability for girls to wear boyish clothes and engage in stereotypical masculine activities such as playing soccer/football. However, there was no comparable acceptance of boys engaging in traditional feminine behaviors. Across all sites, challenging gender norms was often found to lead to verbal, physical, and/or psychological retribution.
Conclusions: While it is sometimes acceptable for young adolescents to cross gender boundaries, once it becomes clear that a behavior is socially defined as typical for the other sex, and the adolescent will face more resistance. Researchers, programmers, and clinicians working in the field of adolescent health need not only attend to those who are facing the consequences of challenging prevailing gender norms, but also to address the environment that fosters exclusion and underscores differences
Effectiveness and tolerability of pegylated interferon alfa-2b in combination with ribavirin for treatment of chronic hepatitis C: the PegIntrust Study
Background and study aims : Large international clinical trials conducted in the past 5 years rapidly improved the treatment of chronic hepatitis C; however, it is unclear whether the advances seen in clinical trials are being paralleled by similar improvements in routine clinical practice. PegIntrust is a Belgian community-based trial evaluating the sustained virological response.
Patients and Methods : Observational study of 219 patients receiving pegylated interferon alfa-2b (1.5 mu g/kg/wk) and weight. based ribavirin (800-1200 mg/day) for 48 weeks. Primary study end point was sustained virological response (SVR), defined as undetectable HCV RNA 6 months after the completion of treatment.
Results : In total, 108 patients (49.3 %) had undetectable HCV RNA at the end of therapy, 91(41.6%) attaining SVR. Of the 111 patients without an end-of-treatment response, 28 were non-responders, and 21 had virological breakthrough. In total, 134 patients attained early virological response (EVR); 88 (65.7%) of those patients attained SVR. In contrast, 82 (96.5 %) of the 85 patients who did not attain EVR also did not attain SVR. Age, fibrosis score and baseline viral load were identified as important predictors of treatment outcome. The most frequently reported serious adverse events resulting in treatment discontinuation were anemia (n = 10), fatigue/asthenia/malaise (n = 6) and fever (n = 3).
Conclusion : Our data indicate that treatment of chronic hepatitis C with PEG-IFN alfa-2b plus weight-based ribavirin results in favourable treatment outcomes in a Belgian cohort of patients treated in community-based clinical practice. (Ada gastroenterol. belg., 2010, 73, 5-11)
Hubble Space Telescope survey of the Perseus Cluster -III: The effect of local environment on dwarf galaxies
We present the results of a Hubble Space Telescope (HST) study of dwarf
galaxies in the outer regions of the nearby rich Perseus Cluster, down to M_V =
-12, and compare these with the dwarf population in the cluster core from our
previous HST imaging. In this paper we examine how properties such as the
colour magnitude relation, structure and morphology are affected by environment
for the lowest mass galaxies. Dwarf galaxies are excellent tracers of the
effects of environment due to their low masses, allowing us to derive their
environmentally based evolution, which is more subtle in more massive galaxies.
We identify 11 dwarf elliptical (dE) and dwarf spheroidal (dSph) galaxies in
the outer regions of Perseus, all of which are previously unstudied. We measure
the (V-I)_0 colours of our newly discovered dEs, and find that these dwarfs lie
on the same red sequence as those in the cluster core. The morphologies of
these dwarfs are examined by quantifying their light distributions using CAS
parameters, and we find that dEs in the cluster outskirts are on average more
disturbed than those in the core, with =0.13\pm0.09 and =0.18\pm0.08,
compared to =0.02\pm0.04, =0.01\pm0.07 for those in the core. Based on
these results, we infer that these objects are ``transition dwarfs'', likely in
the process of transforming from late-type to early type galaxies as they
infall into the cluster, with their colours transforming before their
structures. When we compare the number counts for both the core and outer
regions of the cluster, we find that below M_V = -12, the counts in the outer
regions of the cluster exceed those in the core. This is evidence that in the
very dense region of the cluster, dwarfs are unable to survive unless they are
sufficiently massive to prevent their disruption by the cluster potential and
interactions with other galaxies.Comment: 14 pages, 11 figures. MNRAS accepte
Formation and Evolution of Dwarf Elliptical Galaxies - II. Spatially resolved star-formation histories
We present optical VLT spectroscopy of 16 dwarf elliptical galaxies (or dEs)
comparable in mass to NGC 205, and belonging to the Fornax cluster and to
nearby groups of galaxies. Using ULySS and STECKMAP, we derive radial profiles
of the SSP-equivalent ages, metallicities and star-formation histories. The old
stellar population of the dEs, which dominates their mass, is likely coeval
with that of massive ellipticals or bulges, but the star formation efficiency
is lower. Important intermediate age (1-5 Gyr) populations, and frequently
tails of star formation until recent times are detected. These histories are
reminiscent of their lower mass dSph counterparts of the Local Group. Most
galaxies (10/16) show significant metallicity gradients, with metallicity
declining by 0.5 dex over one half-light radius on average. These gradients are
already present in the old population. The flattened (or discy), rotating
objects (6/16) have flat metallicity profiles. This may be consistent with a
distinct origin for these galaxies or it may be due to their geometry. The
central SSP-equivalent age varies between 1 and 6 Gyr, with the age slowly
increasing with radius in the vast majority of objects. The group and cluster
galaxies have similar radial gradients and star-formation histories. The strong
and old metallicity gradients place important constraints on the possible
formation scenarios of dEs. Numerical simulations of the formation of spherical
low-mass galaxies reproduce these gradients, but they require a longer time for
them to build up. A gentle depletion of the gas, by ram-pressure stripping or
starvation, could drive the gas-rich, star-forming progenitors to the present
dEs.Comment: 21 pages, 9 figures. Accepted in MNRA
Generation of Intrinsic Vibrational Gap Modes in Three-Dimensional Ionic Crystals
The existence of anharmonic localization of lattice vibrations in a perfect
3-D diatomic ionic crystal is established for the rigid-ion model by molecular
dynamics simulations. For a realistic set of NaI potential parameters, an
intrinsic localized gap mode vibrating in the [111] direction is observed for
fcc and zinc blende lattices. An axial elastic distortion is an integral
feature of this mode which forms more readily for the zinc blende than for the
fcc structure. Molecular dynamics simulations verify that in each structure
this localized mode may be stable for at least 200 cycles.Comment: 5 pages, 4 figures, RevTeX, using epsf.sty. To be published in Phys.
Rev. B. Also available at http://www.msc.cornell.edu/~kiselev
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