3,816 research outputs found
Statistical quantum operation
A generic unital positive operator-valued measure (POVM), which transforms a
given stationary pure state to an arbitrary statistical state with perfect
decoherence, is presented. This allows one to operationally realize
thermalization as a special case. The loss of information due to randomness
generated by the operation is discussed by evaluating the entropy.
Thermalization of the bipartite spin-1/2 system is discussed as an illustrative
example.Comment: 10 pages, no figure
Classical Cepheids, what else?
We present new and independent estimates of the distances to the Magellanic
Clouds (MCs) using near-infrared (NIR) and optical--NIR period--Wesenheit (PW)
relations. The slopes of the PW relations are, within the dispersion, linear
over the entire period range and independent of metal content. The absolute
zero points were fixed using Galactic Cepheids with distances based on the
infrared surface-brightness method. The true distance modulus we found for the
Large Magellanic Cloud--- mag---and the
Small Magellanic Cloud--- mag---agree quite
well with similar distance determinations based on robust distance indicators.
We also briefly discuss the evolutionary and pulsation properties of MC
Cepheids
Variable stars in Terzan 5: additional evidence of multi-age and multi-iron stellar populations
Terzan 5 is a complex stellar system in the Galactic bulge, harboring stellar
populations with very different iron content ({\Delta}[Fe/H] ~1 dex) and with
ages differing by several Gyrs. Here we present an investigation of its
variable stars. We report on the discovery and characterization of three RR
Lyrae stars. For these newly discovered RR Lyrae and for six Miras of known
periods we provide radial velocity and chemical abundances from spectra
acquired with X-SHOOTER at the VLT. We find that the three RR Lyrae and the
three short period Miras (P<300 d) have radial velocity consistent with being
Terzan 5 members. They have sub-solar iron abundances and enhanced
[{\alpha}/Fe], well matching the age and abundance patterns of the 12 Gyr
metal-poor stellar populations of Terzan 5. Only one, out of the three long
period (P>300 d) Miras analyzed in this study, has a radial velocity consistent
with being Terzan 5 member. Its super-solar iron abundance and solar-scaled
[{\alpha}/Fe] nicely match the chemical properties of the metal rich stellar
population of Terzan 5 and its derived mass nicely agrees with being several
Gyrs younger than the short period Miras. This young variable is an additional
proof of the surprising young sub-population discovered in Terzan 5.Comment: 20 pages, 4 figures, in press on the Ap
Differences between families in the amount of salivary H substances *
The saliva ABO inhibition titres of the members of twenty-eight 0X0 and ten BxO mating types were determined. The results of the examinations suggest that: (1) A precursor ‘H’ substance is formed by all secretors which is converted into A, B, or AB depending on the individual's blood group. (2) the titres of the H substance secreted by members of the same sibship and of the same blood group are very uniform (high intra-class correlation) indicating genetic control over the amount of the soluble ABO substances secreted. A genetic hypothesis was put forward to account for these findings.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66443/1/j.1469-1809.1962.tb01308.x.pd
On the metallicity distribution of classical Cepheids in the Galactic inner disk
We present homogeneous and accurate iron abundances for almost four dozen
(47) of Galactic Cepheids using high-spectral resolution (R40,000) high
signal-to-noise ratio (S/N 100) optical spectra collected with UVES at
VLT. A significant fraction of the sample (32) is located in the inner disk (RG
6.9 kpc) and for half of them we provide new iron abundances. Current
findings indicate a steady increase in iron abundance when approaching the
innermost regions of the thin disk. The metallicity is super-solar and ranges
from 0.2 dex for RG 6.5 kpc to 0.4 dex for RG 5.5 kpc. Moreover,
we do not find evidence of correlation between iron abundance and distance from
the Galactic plane. We collected similar data available in the literature and
ended up with a sample of 420 Cepheids. Current data suggest that the mean
metallicity and the metallicity dispersion in the four quadrants of the
Galactic disk attain similar values. The first-second quadrants show a more
extended metal-poor tail, while the third-fourth quadrants show a more extended
metal-rich tail, but the bulk of the sample is at solar iron abundance.
Finally, we found a significant difference between the iron abundance of
Cepheids located close to the edge of the inner disk ([Fe/H]0.4) and
young stars located either along the Galactic bar or in the nuclear bulge
([Fe/H]0). Thus suggesting that the above regions have had different
chemical enrichment histories. The same outcome applies to the metallicity
gradient of the Galactic bulge, since mounting empirical evidence indicates
that the mean metallicity increases when moving from the outer to the inner
bulge regions.Comment: 10 pages, 5 figures; Corrected typos, corrected Table
Scalable Production of Highly-Sensitive Nanosensors Based on Graphene Functionalized with a Designed G Protein-Coupled Receptor
We have developed a novel, all-electronic biosensor for opioids that consists
of an engineered mu opioid receptor protein, with high binding affinity for
opioids, chemically bonded to a graphene field-effect transistor to read out
ligand binding. A variant of the receptor protein that provided chemical
recognition was computationally redesigned to enhance its solubility and
stability in an aqueous environment. A shadow mask process was developed to
fabricate arrays of hundreds of graphene transistors with average mobility of
~1500 cm2 V-1 s-1 and yield exceeding 98%. The biosensor exhibits high
sensitivity and selectivity for the target naltrexone, an opioid receptor
antagonist, with a detection limit of 10 pg/mL.Comment: Nano Letters 201
The RR Lyrae variables and Horizontal Branch of NGC6656 (M22)
The first calibrated broadband UBVI time-series photometry is presented for
the RR Lyrae variable stars in NGC6656 (M22), with observations spanning a
range of twenty-two years. We have also redetermined the variability types and
periods for the RR Lyrae stars identified previously by photographic
observations, revising the number of fundamental-mode RR Lyrae variables (RR0)
to 10 and the number of first-overtone variables (RR1) to 16. The mean periods
of the RR0 and RR1 variables are _{RR0}=0.66 \pm 0.02 d and _{RR1}=0.33
\pm 0.01 d, respectively, supporting an Oosterhoff II classification for the
cluster. The number ratio of RR1- to all RR-type variables is N_1/N_{RR}=0.61,
also consistent with an Oosterhoff II designation. Both the RR Lyrae stars'
minimum light colors and the blue edge of the RR Lyrae instability strip
suggest E(B-V)=0.36 \pm 0.02 mag toward M22. Regarding the HB morphology of
M22, we find (B-R)/(B+V+R)=+0.97 \pm 0.1 and at least one "gap" located in an
unusual part of the blue HB, in the middle of the so-called hot HB stars.Comment: accepted to A
On the kinematic separation of field and cluster stars across the Bulge globular NGC 6528
We present deep and precise multi-band photometry of the Galactic Bulge
globular cluster NGC6528. The current dataset includes optical and
near-infrared images collected with ACS/WFC, WFC3/UVIS, and WFC3/IR on board
the Hubble Space Telescope. The images cover a time interval of almost ten
years and we have been able to carry out a proper-motion separation between
cluster and field stars. We performed a detailed comparison in the m_F814W,
m_F606W - m_F814W Color-Magnitude Diagram with two empirical calibrators
observed in the same bands. We found that NGC6528 is coeval with and more
metal-rich than 47Tuc. Moreover, it appears older and more metal-poor than the
super-metal-rich open cluster NGC6791. The current evidence is supported by
several diagnostics (red horizontal branch, red giant branch bump, shape of the
sub-giant branch, slope of the main sequence) that are minimally affected by
uncertainties in reddening and distance. We fit the optical observations with
theoretical isochrones based on a scaled-solar chemical mixture and found an
age of 11 +- 1 Gyr and an iron abundance slightly above solar ([Fe/H = +0.20).
The iron abundance and the old cluster age further support the recent
spectroscopic findings suggesting a rapid chemical enrichment of the Galactic
Bulge.Comment: 14 pages, 12 figures (2 at low resolution); added references;
corrected figure 3, 4, 5, 8 and 9; results unchanged. Erratum to be published
in Ap
On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk
We present homogeneous and accurate iron abundances for 42 Galactic Cepheids
based on high-spectral resolution (R~38,000) high signal-to-noise ratio
(SNR>100) optical spectra collected with UVES at VLT (128 spectra). The above
abundances were complemented with high-quality iron abundances provided either
by our group (86) or available in the literature. We paid attention in deriving
a common metallicity scale and ended up with a sample of 450 Cepheids. We also
estimated for the entire sample accurate individual distances by using
homogeneous near-infrared photometry and the reddening free Period-Wesenheit
relations. The new metallicity gradient is linear over a broad range of
Galactocentric distances (Rg~5-19 kpc) and agrees quite well with similar
estimates available in the literature (-0.060+/-0.002 dex/kpc). We also uncover
evidence which suggests that the residuals of the metallicity gradient are
tightly correlated with candidate Cepheid Groups (CGs). The candidate CGs have
been identified as spatial overdensities of Cepheids located across the thin
disk. They account for a significant fraction of the residual fluctuations, and
in turn for the large intrinsic dispersion of the metallicity gradient. We
performed a detailed comparison with metallicity gradients based on different
tracers: OB stars and open clusters. We found very similar metallicity
gradients for ages younger than 3 Gyrs, while for older ages we found a
shallower slope and an increase in the intrinsic spread. The above findings
rely on homogeneous age, metallicity and distance scales. Finally we found, by
using a large sample of Galactic and Magellanic Cepheids for which are
available accurate iron abundances, that the dependence of the luminosity
amplitude on metallicity is vanishing.Comment: Accepted in A&A, 11 figures, 7 table
A Bayesian Approach to Calibrating Period-Luminosity Relations of RR Lyrae Stars in the Mid-Infrared
A Bayesian approach to calibrating period-luminosity (PL) relations has
substantial benefits over generic least-squares fits. In particular, the
Bayesian approach takes into account the full prior distribution of the model
parameters, such as the a priori distances, and refits these parameters as part
of the process of settling on the most highly-constrained final fit.
Additionally, the Bayesian approach can naturally ingest data from multiple
wavebands and simultaneously fit the parameters of PL relations for each
waveband in a procedure that constrains the parameter posterior distributions
so as to minimize the scatter of the final fits appropriately in all wavebands.
Here we describe the generalized approach to Bayesian model fitting and then
specialize to a detailed description of applying Bayesian linear model fitting
to the mid-infrared PL relations of RR Lyrae variable stars. For this example
application we quantify the improvement afforded by using a Bayesian model fit.
We also compare distances previously predicted in our example application to
recently published parallax distances measured with the Hubble Space Telescope
and find their agreement to be a vindication of our methodology. Our intent
with this article is to spread awareness of the benefits and applicability of
this Bayesian approach and encourage future PL relation investigations to
consider employing this powerful analysis method.Comment: 6 pages, 1 figure. Accepted for publication in Astrophysics & Space
Science. Following a presentation at the conference The Fundamental Cosmic
Distance Scale: State of the Art and the Gaia Perspective, Naples, May 201
- …