2,013 research outputs found
Secure self-calibrating quantum random bit generator
Random bit generators (RBGs) are key components of a variety of information
processing applications ranging from simulations to cryptography. In
particular, cryptographic systems require "strong" RBGs that produce
high-entropy bit sequences, but traditional software pseudo-RBGs have very low
entropy content and therefore are relatively weak for cryptography. Hardware
RBGs yield entropy from chaotic or quantum physical systems and therefore are
expected to exhibit high entropy, but in current implementations their exact
entropy content is unknown. Here we report a quantum random bit generator
(QRBG) that harvests entropy by measuring single-photon and entangled
two-photon polarization states. We introduce and implement a quantum
tomographic method to measure a lower bound on the "min-entropy" of the system,
and we employ this value to distill a truly random bit sequence. This approach
is secure: even if an attacker takes control of the source of optical states, a
secure random sequence can be distilled.Comment: 5 pages, 2 figure
Strong low-frequency quantum correlations from a four-wave mixing amplifier
We show that a simple scheme based on nondegenerate four-wave mixing in a hot
atomic vapor behaves like a near-perfect phase-insensitive optical amplifier,
which can generate bright twin beams with a measured quantum noise reduction in
the intensity difference of more than 8 dB, close to the best optical
parametric amplifiers and oscillators. The absence of a cavity makes the system
immune to external perturbations, and the strong quantum noise reduction is
observed over a large frequency range.Comment: 4 pages, 4 figures. Major rewrite of the previous version. New
experimental results and further analysi
Mask-R 2 CNN: a distance-field regression version of Mask-RCNN for fetal-head delineation in ultrasound images
Background and objectives: Fetal head-circumference (HC) measurement from ultrasound (US) images provides useful hints for assessing fetal growth. Such measurement is performed manually during the actual clinical practice, posing issues relevant to intra- and inter-clinician variability. This work presents a fully automatic, deep-learning-based approach to HC delineation, which we named Mask-R2CNN. It advances our previous work in the field and performs HC distance-field regression in an end-to-end fashion, without requiring a priori HC localization nor any postprocessing for outlier removal. Methods: Mask-R2CNN follows the Mask-RCNN architecture, with a backbone inspired by feature-pyramid networks, a region-proposal network and the ROI align. The Mask-RCNN segmentation head is here modified to regress the HC distance field. Results: Mask-R2CNN was tested on the HC18 Challenge dataset, which consists of 999 training and 335 testing images. With a comprehensive ablation study, we showed that Mask-R2CNN achieved a mean absolute difference of 1.95 mm (standard deviation = ± 1.92 mm), outperforming other approaches in the literature. Conclusions: With this work, we proposed an end-to-end model for HC distance-field regression. With our experimental results, we showed that Mask-R2CNN may be an effective support for clinicians for assessing fetal growth
Metronomic Chemotherapy with Vinorelbine Produces Clinical Benefit and Low Toxicity in Frail Elderly Patients Affected by Advanced Non-Small Cell Lung Cancer
Lung cancer is the leading cause of death worldwide. The treatment choice for advanced stage of lung cancer may depend on histotype, performance status (PS), age, and comorbidities. In the present study, we focused on the effect of metronomic vinorelbine treatment in elderly patients with advanced unresectable non-small cell lung cancer (NSCLC). Methods. From January 2016 to December 2016, 44 patients affected by non-small cell lung cancer referred to our oncology day hospital were progressively analyzed. The patients were treated with oral vinorelbine 30 mg x 3/wk or 40 mg x 3/wk meaning one day on and one day off. The patients were older than 60, stage IIIB or IV, ECOG PS â„ 1, and have at least one important comorbidity (renal, hepatic, or cardiovascular disease). The schedule was based on ECOG-PS and comorbidities. The primary endpoint was progression-free survival (PFS). PFS was used to compare patients based on different scheduled dosage (30 or 40 mg x3/weekly) and age (more or less than 75 years old) as exploratory analysis. We also evaluated as secondary endpoint toxicity according to Common Toxicity Criteria Version 2.0. Results. Vinorelbine showed a good safety profile at different doses taken orally and was effective in controlling cancer progression. The median overall survival (OS) was 12 months. The disease control rate (DCR) achieved 63%. The median PFS was 9 months. A significant difference in PFS was detected comparing patients aged below with those over 75, and the HR value was 0.72 (p<0.05). Not significant was the difference between groups with different schedules. Conclusions. This study confirmed the safety profile of metronomic vinorelbine and its applicability for patients unfit for standard chemotherapies and adds the possibility of considering this type of schedule not only for very elderly patients
Weak Galactic Halo--Fornax dSph Connection from RR Lyrae Stars
For the first time accurate pulsation properties of the ancient variable
stars of the Fornax dwarf spheroidal galaxy (dSph) are discussed in the broad
context of galaxy formation and evolution. Homogeneous multi-band optical
photometry of spanning {\it twenty} years has allowed us to identify and
characterize more than 1400 RR Lyrae stars (RRLs) in this galaxy. Roughly 70\%
are new discoveries. We investigate the period-amplitude distribution and find
that Fornax shows a lack of High Amplitude (A_V\gsim0.75 mag) Short Period
fundamental-mode RRLs (P\lsim0.48 d, HASPs). These objects occur in stellar
populations more metal-rich than [Fe/H]-1.5 and they are common in the
Galactic halo (Halo) and in globulars. This evidence suggests that old (age
older than 10 Gyr) Fornax stars are relatively metal-poor.
A detailed statistical analysis of the role of the present-day Fornax dSph in
reproducing the Halo period distribution shows that it can account for only a
few to 20\% of the Halo when combined with RRLs in massive dwarf galaxies
(Sagittarius dSph, Large Magellanic Cloud). This finding indicates that
Fornax-like systems played a minor role in building up the Halo when compared
with massive dwarfs. We also discuss the occurrence of HASPs in connection with
the luminosity and the early chemical composition of nearby dwarf galaxies. We
find that, independently of their individual star formation histories, bright
(M_V\lsim-13.5 mag) galaxies have HASPs, whereas faint ones (M_V\gsim-11
mag) do not. Interestingly enough, Fornax belongs to a luminosity range
(--11M--13.5 mag) in which the occurrence of HASPs appears to be
correlated with the early star formation and chemical enrichment of the host
galaxy.Comment: 7 pages, 5 figures, A&A, accepte
Massive Star cluster formation under the microscope at z=6
We report on a superdense star-forming region with an effective radius (R_e)
smaller than 13 pc identified at z=6.143 and showing a star-formation rate
density \Sigma_SFR~1000 Msun/yr/kpc2 (or conservatively >300 Msun/yr/kpc2).
Such a dense region is detected with S/N>40 hosted by a dwarf extending over
440 pc, dubbed D1 (Vanzella et al. 2017b). D1 is magnified by a factor
17.4+/-5.0 behind the Hubble Frontier Field galaxy cluster MACS~J0416 and
elongated tangentially by a factor 13.2+/-4.0 (including the systematic
errors). The lens model accurately reproduces the positions of the confirmed
multiple images with a r.m.s. of 0.35", and the tangential stretch is well
depicted by a giant multiply-imaged Lya arc. D1 is part of an interacting
star-forming complex extending over 800 pc. The SED-fitting, the very blue
ultraviolet slope (\beta ~ -2.5, F(\lambda) ~ \lambda^\beta) and the prominent
Lya emission of the stellar complex imply that very young (< 10-100 Myr),
moderately dust-attenuated (E(B-V)<0.15) stellar populations are present and
organised in dense subcomponents. We argue that D1 (with a stellar mass of 2 x
10^7 Msun) might contain a young massive star cluster of M < 10^6 Msun and
Muv~-15.6 (or m_uv=31.1), confined within a region of 13 pc, and not dissimilar
from some local super star clusters (SSCs). The ultraviolet appearance of D1 is
also consistent with a simulated local dwarf hosting a SSC placed at z=6 and
lensed back to the observer. This compact system fits into some popular
globular cluster formation scenarios. We show that future high spatial
resolution imaging (e.g., E-ELT/MAORY-MICADO and VLT/MAVIS) will allow us to
spatially resolve light profiles of 2-8 pc.Comment: 21 pages, 14 figures, 1 table, MNRAS accepte
Probing the early chemical evolution of the Sculptor dSph with purely old stellar tracers
We present the metallicity distribution of a sample of 471 RR Lyrae (RRL)
stars in the Sculptor dSph, obtained from the -band Period-Luminosity
relation. It is the first time that the early chemical evolution of a dwarf
galaxy is characterized in such a detailed and quantitative way, using
photometric data alone. We find a broad metallicity distribution (FWHM=0.8 dex)
that is peaked at [Fe/H]-1.90 dex, in excellent agreement with
literature values obtained from spectroscopic data. Moreover, we are able to
directly trace the metallicity gradient out to a radius of 55 arcmin. We
find that in the outer regions (r32 arcmin) the slope of the metallicity
gradient from the RRLs (-0.025 dex arcmin) is comparable to the
literature values based on red giant (RG) stars. However, in the central part
of Sculptor we do not observe the latter gradients. This suggests that there is
a more metal-rich and/or younger population in Sculptor that does not produce
RRLs. This scenario is strengthened by the observation of a metal-rich peak in
the metallicity distribution of RG stars by other authors, which is not present
in the metallicity distribution of the RRLs within the same central area.Comment: 5 pages, 4 figures. Accepted for publication on MNRAS Letter
A regression framework to head-circumference delineation from US fetal images
Background and Objectives: Measuring head-circumference (HC) length from ultrasound (US) images is a crucial clinical task to assess fetus growth. To lower intra- and inter-operator variability in HC length measuring, several computer-assisted solutions have been proposed in the years. Recently, a large number of deep-learning approaches is addressing the problem of HC delineation through the segmentation of the whole fetal head via convolutional neural networks (CNNs). Since the task is a edge-delineation problem, we propose a different strategy based on regression CNNs. Methods: The proposed framework consists of a region-proposal CNN for head localization and centering, and a regression CNN for accurately delineate the HC. The first CNN is trained exploiting transfer learning, while we propose a training strategy for the regression CNN based on distance fields. Results: The framework was tested on the HC18 Challenge dataset, which consists of 999 training and 335 testing images. A mean absolute difference of 1.90 ( ± 1.76) mm and a Dice similarity coefficient of 97.75 ( ± 1.32) % were achieved, overcoming approaches in the literature. Conclusions: The experimental results showed the effectiveness of the proposed framework, proving its potential in supporting clinicians during the clinical practice
Variable Stars in Local Group Galaxies. I: Tracing the Early Chemical Enrichment and Radial Gradients in the Sculptor dSph with RR Lyrae Stars
We identified and characterized the largest (536) RR Lyrae (RRL) sample in a
Milky Way dSph satellite (Sculptor) based on optical photometry data collected
over 24 years.
The RRLs display a spread in V-magnitude (0.35 mag) which appears
larger than photometric errors and the horizontal branch (HB) luminosity
evolution of a mono-metallic population. Using several calibrations of two
different reddening free and metal independent Period-Wesenheit relations we
provide a new distance estimate =19.62 mag (=0.04 mag) that
agrees well with literature estimates. We constrained the metallicity
distribution of the old population, using the Period-Luminosity relation,
and we found that it ranges from -2.3 to -1.5 dex. The current estimate is
narrower than suggested by low and intermediate spectroscopy of RGBs
([Fe/H] 1.5).
We also investigated the HB morphology as a function of the galactocentric
distance. The HB in the innermost regions is dominated by red HB stars and by
RRLs, consistent with a more metal-rich population, while in the outermost
regions it is dominated by blue HB stars and RRLs typical of a metal-poor
population. Our results suggest that fast chemical evolution occurred in
Sculptor, and that the radial gradients were in place at an early epoch.Comment: 10 pages, 5 figures, MNRAS accepte
Association between serum Mg2+ concentrations and cardiovascular organ damage in a cohort of adult subjects
Magnesium (Mg2+) levels are associated with insulin resistance, hypertension, atherosclerosis, and type 2 diabetes (T2DM). We evaluated the clinical utility of physiological Mg2+ in assessing subclinical cardiovascular organ damage including increased carotid artery intima-media thickness (c-IMT) and left ventricular mass index (LVMI) in a cohort of well-characterized adult non-diabetic individuals. Age-and gender-adjusted correlations between Mg2+ and metabolic parameters showed that Mg2+ circulating levels were correlated negatively with body mass index (BMI), fasting glucose, and 2h-oral glucose tolerance test (OGTT) glucose. Similarly, Mg2+ levels were significantly and negatively related to c-IMT and LVMI. A multivariate regression analysis revealed that age (ÎČ = 0.440; p < 0.0001), BMI (ÎČ = 0.225; p < 0.0001), and Mg2+ concentration (ÎČ = â0.122; p < 0.01) were independently associated with c-IMT. Age (ÎČ = 0.244; p = 0.012), Mg2+ (ÎČ = â0.177; p = 0.019), and diastolic blood pressure (ÎČ = 0.184; p = 0.038) were significantly associated with LVMI in women, while age (ÎČ = 0.211; p = 0.019), Mg2+ (ÎČ = â0.171; p = 0.038) and the homeostasis model assessment index of insulin resistance (HOMA-IR) (ÎČ = â0.211; p = 0.041) were the sole variables associated with LVMI in men. In conclusion, our data support the hypothesis that the assessment of Mg2+ as part of the initial work-up might help unravel the presence of subclinical organ damage in subjects at increased risk of cardiovascular complications
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