1,617 research outputs found
A new look at Spitzer primary transit observations of the exoplanet HD189733b
Blind source separation techniques are used to reanalyse two exoplanetary
transit lightcurves of the exoplanet HD189733b recorded with the IR camera IRAC
on board the Spitzer Space Telescope at 3.6m during the "cold" era. These
observations, together with observations at other IR wavelengths, are crucial
to characterise the atmosphere of the planet HD189733b. Previous analyses of
the same datasets reported discrepant results, hence the necessity of the
reanalyses. The method we used here is based on the Independent Component
Analysis (ICA) statistical technique, which ensures a high degree of
objectivity. The use of ICA to detrend single photometric observations in a
self-consistent way is novel in the literature. The advantage of our reanalyses
over previous work is that we do not have to make any assumptions on the
structure of the unknown instrumental systematics. Such "admission of
ignorance" may result in larger error bars than reported in the literature, up
to a factor . This is a worthwhile trade-off for much higher objectivity,
necessary for trustworthy claims. Our main results are (1) improved and robust
values of orbital and stellar parameters, (2) new measurements of the transit
depths at 3.6m, (3) consistency between the parameters estimated from the
two observations, (4) repeatability of the measurement within the photometric
level of in the IR, (5) no evidence of stellar
variability at the same photometric level within 1 year.Comment: 43 pages, 18 figure
Inference on a stochastic two-compartment model in tumor growth
A continuous-time model that incorporates several key elements in tumor dynamics is analyzed. More precisely, the form of proliferating and quiescent cell lines comes out from their relations with the whole tumor mass, giving rise to a two-dimensional diffusion process, generally time non-homogeneous. This model is able to include the effects of the mutual interactions between the two subpopulations. Estimation of the rates of the two subpopulations based on some characteristics of the involved diffusion processes is discussed when longitudinal data are available. To this aim, two procedures are presented. Some simulation results are developed in order to show the validity of these procedures as well as to compare them. An application to real data is finally presented
Verb Semantics modulates neural activity in the left Lateral Temporal Cortex
Here we show that the implicit processing of telicity, dynamicity and agentivity differentially modulate neural activity across different brain clusters and, in particular, within lMTG. We found that selectivity for state and telic verbs identified the most anterior and the most posterior portion of lMTG, respectively. Furthermore, dynamicity and agentivity modulated brain responses in parietal and ventral extrastriate regions. The role of each property was clearly isolated, as the stimuli were specifically controlled for and the task design covertly assessed the representation of those properties. Different event types are differentially mapped based on their semantic representation and, in particular, lMTG represents conceptual semantic properties of verbs: specifically, that kind of conceptual information which is relevant to morphosyntax, that is, telicity, stativity and agentivity, that, unlike referential semantic features, and independently of them, govern morphosyntax in a specified way
Deep Chandra Monitoring Observations of NGC 4649: II. Wide-Field Hubble Space Telescope Imaging of the Globular Clusters
We present g and z photometry and size estimates for globular clusters (GCs)
in the massive Virgo elliptical NGC 4649 (M60) using a five-pointing Hubble
Space Telescope/Advanced Camera for Surveys mosaic. The metal-poor GCs show a
monotonic negative metallicity gradient of (-0.43 +/- 0.10) dex per dex in
radius over the full radial range of the data, out to ~ 24 kpc. There is
evidence for substantial color substructure among the metal-rich GCs. The
metal-poor GCs have typical sizes ~ 0.4 pc larger than the metal-rich GCs out
to large galactocentric distances (~> 20 kpc), favoring an intrinsic
explanation for the size difference rather than projection effects. There is no
clear relation between half-light radius and galactocentric distance beyond ~
15 kpc, suggesting that the sizes of GCs are not generically set by tidal
limitation. Finally, we identify ~ 20 candidate ultra-compact dwarfs that
extend down to surprisingly faint absolute magnitudes (M_z ~ -8.5), and may
bridge the gap between this class and "extended clusters" in the Local Group.
Three of the brighter candidates have published radial velocities and can be
confirmed as bona fide ultra-compact dwarfs; follow-up spectroscopy will
determine the nature of the remainder of the candidates.Comment: ApJ in press. For redacted long table 1, see:
http://www.pa.msu.edu/~strader/4649/table.te
Genetic diversity and relationships among 192 public common bean inbred lines assessed by SSR markers.
Knowledge of germplasm diversity and of relationships among elite breeding materials has a significant impact on the improvement of crop plants and on the development of strategies for genetic resources management and exploration. The present study was conducted to determine the
level of genetic variation and relatedness among some selected common bean varieties by using microsatellite markers. In this investigation, we used 61 SSRs to fingerprint 192 common bean
inbred public lines released over the last 50 years in the U.S.A. All the lines are commercial seed type classes that are grown in the USA and include both dry bean classes and snap beans for the fresh and processing markets.The 344 alleles identified were used as raw data for estimating the amount of diversity and to describe the genetic structure of the commercial bean gene pool. A model-based clustering analysis placed the varieties in six clusters that correspond to major breeding groups plus a set of lines showing evidence of mixed origins. Neighbor-joining tree was constructed to further assess the genetic structure of common bean lines, showing good agreement with the pedigree information and the cluster analysis. A significant fixation index FST, also revealed genetic substructure within the U.S. common bean gene pool with Kidney and Pinto-Great Northern beans being the most different from the other varietal groups.The results of this study - based on a much larger number of SSRs -confirm a previous observation indicating a relatively low
level of genetic variation and a molecular variability that parallels phenotypic characters distinguishing different commercial groups. Our results indicate also a strong subpopulation
structure and provide additional tools for breeding and breeder’s rights implementation
Coherent electronic and nuclear dynamics in a rhodamine heterodimer-DNA supramolecular complex
Elucidating the role of quantum coherences in energy migration within biological and artificial multichromophoric antenna systems is the subject of an intense debate. It is also a practical matter because of the decisive implications for understanding the biological processes and engineering artificial materials for solar energy harvesting. A supramolecular rhodamine heterodimer on a DNA scaffold was suitably engineered to mimic the basic donor-acceptor unit of light-harvesting antennas. Ultrafast 2D electronic spectroscopic measurements allowed identifying clear features attributable to a coherent superposition of dimer electronic and vibrational states contributing to the coherent electronic charge beating between the donor and the acceptor. The frequency of electronic charge beating is found to be 970 cm-1 (34 fs) and can be observed for 150 fs. Through the support of high level ab initio TD-DFT computations of the entire dimer, we established that the vibrational modes preferentially optically accessed do not drive subsequent coupling between the electronic states on the 600 fs of the experiment. It was thereby possible to characterize the time scales of the early time femtosecond dynamics of the electronic coherence built by the optical excitation in a large rigid supramolecular system at a room temperature in solution. © 2017 the Owner Societies.Multi valued and parallel molecular logi
Geometry Diagnostics of a Stellar Flare from Fluorescent X-rays
We present evidence of Fe fluorescent emission in the Chandra HETGS spectrum
of the single G-type giant HR 9024 during a large flare. In analogy to solar
X-ray observations, we interpret the observed Fe K line as being
produced by illumination of the photosphere by ionizing coronal X-rays, in
which case, for a given Fe photospheric abundance, its intensity depends on the
height of the X-ray source. The HETGS observations, together with 3D Monte
Carlo calculations to model the fluorescence emission, are used to obtain a
direct geometric constraint on the scale height of the flaring coronal plasma.
We compute the Fe fluorescent emission induced by the emission of a single
flaring coronal loop which well reproduces the observed X-ray temporal and
spectral properties according to a detailed hydrodynamic modeling. The
predicted Fe fluorescent emission is in good agreement with the observed value
within observational uncertainties, pointing to a scale height \rstar. Comparison of the HR 9024 flare with that recently observed on II
Peg by Swift indicates the latter is consistent with excitation by X-ray
photoionization.Comment: accepted for publication on the Astrophysical Journal Letter
Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry
We aim at characterizing the accretion properties of several hundred members
of the star-forming cluster NGC 2264 (3 Myr). We performed a deep u,g,r,i
mapping and a simultaneous u+r monitoring of the region with CFHT/MegaCam in
order to directly probe the accretion process from UV excess measurements.
Photometric properties and stellar parameters are determined homogeneously for
about 750 monitored young objects, spanning the mass range 0.1-2 Mo. About 40%
are classical (accreting) T Tauri stars, based on various diagnostics (H_alpha,
UV and IR excesses). The remaining non-accreting members define the
(photospheric+chromospheric) reference UV emission level over which flux excess
is detected and measured. We revise the membership status of cluster members
based on UV accretion signatures and report a new population of 50 CTTS
candidates. A large range of UV excess is measured for the CTTS population,
varying from a few 0.1 to 3 mag. We convert these values to accretion
luminosities and obtain mass accretion rates ranging from 1e-10 to 1e-7 Mo/yr.
Taking into account a mass-dependent detection threshold for weakly accreting
objects, we find a >6sigma correlation between mass accretion rate and stellar
mass. A power-law fit, properly accounting for upper limits, yields M_acc
M^{1.4+/-0.3}. At any given stellar mass, we find a large spread of
accretion rates, extending over about 2 orders of magnitude. The monitoring of
the UV excess on a timescale of a couple of weeks indicates that its
variability typically amounts to 0.5 dex, much smaller than the observed
spread. We suggest that a non-negligible age spread across the cluster may
effectively contribute to the observed spread in accretion rates at a given
mass. In addition, different accretion mechanisms (like, e.g., short-lived
accretion bursts vs. more stable funnel-flow accretion) may be associated to
different M_acc regimes.Comment: 24 pages, 21 figures, accepted for publication in Astronomy &
Astrophysic
Packaging of Wine in Aluminum Cans – A Review
Background and goals - Aluminum cans represent an alternative wine packaging, offering a wide range of styles. Despite the fast-growing nature of the product category and the great market forecast, there is valid concern about the quality of wines in a can. Unfortunately, this leads to the consumer perception that these wines are low-quality products, which must be addressed by the wine industry.
Methods and key findings - Canned wines have a limited shelf life, as they often display unpleasant reductive characteristics (e.g., rotten egg and cooked vegetable off-flavors). Aluminum corrodes in the acidic pH of wine and reacts with sulfur dioxide to yield hydrogen sulfide.
Conclusions and significance - Preparing wine for canned packaging requires extra effort to understand the implications of wine redox chemistry. The wine’s chemical parameters at bottling (in particular, the levels of sulfur and metals) must be managed, and the degradation of the can lining must be limited
Oral amelanotic melanoma: a case report
Objectives. Primary oral melanoma is a very rare malignancy, representing about 0.5% of all melanomas, characterized by a wide clinical-histological variability and a very aggressive behavior. Aim of the present study is to describe
a case of oral amelanotic melanoma, an infrequent variant with a poorer prognosis than that of pigmented
melanomas for a more aggressive biological behavior and frequent delays for the correct diagnosis and for starting the treatment.
Case report. A 53-year-old white man referred at the Department Surgical, Oncological and Oral Sciences for a macular, scarsely pigmented lesion with irregular margins, located on anterior region of hard palate. The lesion, completely asymptomatic and without any history of trauma or injury, was observed by his dentist some months ago. The patient
was a smoker (about 20 cigarettes a day for 30 years) and his anamnesis was negative for any systemic diseases and drug assumption. Histological examination, following the incisional biopsy, showed the hyperplasia of the junctional melanocytes with occasionally dendritic appearance and light atypia; on the recommendation of pathologist, a second incisional biopsy was performed, and a definitive diagnosis of “amelanotic melanoma in situ” was confirmed. After diagnosis,
the patient was referred to the unit of Head and Neck Surgery for staging and surgical approach of the lesion.
Conclusions. This case report underlines the importance to perform biopsy of all lesions of the oral cavity to rule out malignancy, even when slightly colored, asymptomatic and with a clinically harmless presentation. Besides benign
diseases (e.g melanotic macules, nevi, extravasation of blood pigments, amalgam tattoos and deposition of other exogenous/endogenous pigments), rare variant of non-pigmented melanoma should be considered in order to avoid a dangerous diagnostic and therapeutic delay
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