3,879 research outputs found
Front-end Electronics for Timing with pico-seconds precision using 3D Trench Silicon Sensors
The next generation of experiments at colliders demands detectors with
extreme performance in terms of spatial resolution, radiation hardness and
timing capabilities. In this sense, pixel sensors with sizes of a few tens of
, timing resolution of tens of pico-seconds and radiation resistance to
particle fluences in the range of MeV neutron equivalent per cm
are required. 3D silicon sensors, recently developed within the TimeSPOT
initiative, appear as a suitable solution to cope with such demanding
requirements. In order to accurately characterize the timing performance of
this new sensors, several read-out boards, based on discrete active components,
have been designed, assembled, and tested. The same electronics is also
suitable for the characterization of similar pixel sensors whenever timing
performance in the range and below 10-ps is a requirement. This paper describes
the general characteristics needed by front-end electronics to exploit solid
state sensors with high timing capabilities and in particular illustrates the
performance of the developed electronics in the test and characterization of
fast 3D silicon sensors
Nonuniformly hyperbolic systems arising from coupling of chaotic and gradient-like systems
We investigate dynamical systems obtained by coupling two maps, one of which
is chaotic and is exemplified by an Anosov diffeomorphism, and the other is of
gradient type and is exemplified by a N-pole-to-S-pole map of the circle.
Leveraging techniques from the geometric and ergodic theories of hyperbolic
systems, we analyze three different ways of coupling together the two maps
above. For weak coupling, we offer an addendum to existing theory showing that
almost always the attractor has fractal-like geometry when it is not normally
hyperbolic. Our main results are for stronger couplings in which the action of
the Anosov diffeomorphism on the circle map has certain monotonicity
properties. Under these conditions, we show that the coupled systems have
invariant cones and possess SRB measures even though there are genuine
obstructions to uniform hyperbolicity
Comparison of functional connectivity metrics using an unsupervised approach: A source resting-state EEG study
The study of inter-regional synchronization between brain regions represents an important challenge in neuroimaging. Electroencephalography, given the high temporal resolution, allows the investigation of brain activity, connectivity, and network organization in time and frequency domains. Here, some of the most common metrics used to estimate the strength of functional
interaction between pairs of brain regions are compared using source reconstructed time-series from resting-state high-density
electroencephalography. Results show that the investigated metrics, on the basis of their connectivity profiles, may be naturally
grouped into two main clusters. In particular, this finding shows that metrics which tend to limit the effects of volume conduction/signal leakage, although based on different properties of the original signals, may be partitioned into a specific homogeneous cluster, whilst the metrics which do not correct for these effects form a separate cluster. Moreover, this effect is even
clearer when the analysis is replicated at scalp level. In conclusion, although within each cluster different metrics may still capture specific connectivity profiles, this study provides evidence that the result of an arbitrary choice of metric that either does or
does not correct for volume conduction and signal leakage is more relevant
Sleeping Beauty goes to the lab: The psychology of self-locating evidence
Analyses of the Sleeping Beauty Problem are polarised between those advocating the “1/2 view” (“halfers”) and those endorsing the “1/3 view” (“thirders”). The disagreement concerns the evidential relevance of self-locating information. Unlike halfers, thirders regard self-locating information as evidentially relevant in the Sleeping Beauty Problem. In the present study, we systematically manipulate the kind of information available in different formulations of the Sleeping Beauty Problem. Our findings indicate that patterns of judgment on different formulations of the Sleeping Beauty Problem do not fit either the “1/2 view” or the “1/3 view.” Human reasoners tend to acknowledge self-locating evidence as relevant, but discount its weight significantly. Accordingly, self-locating information may trigger more cautious judgments of confirmation than familiar kinds of statistical evidence. We also discuss how these results can advance the debate by providing a more nuanced and empirically grounded account or explication of the evidential impact of self-locating information
Intrinsic timing properties of ideal 3D-trench silicon sensor with fast front-end electronics
This paper describes the fundamental timing properties of a single-pixel
sensor for charged particle detection based on the 3D-trench silicon structure.
We derive the results both analytically and numerically by considering a simple
ideal sensor and the corresponding fast front-end electronics in two different
case scenarios: ideal integrator and real fast electronics (trans-impedance
amplifier). The particular shape of the Time of Arrival (TOA) distribution is
examined and the relation between the time resolution and the spread of
intrinsic charge collection time is discussed, by varying electronics
parameters and discrimination thresholds. The results are obtained with and
without simulated electronics noise. We show that the 3D-trench sensors are
characterized by a , i.e. a portion of the active volume
which leads to the same TOA values when charged particles cross it. The
synchronous region size is dependent on the front-end electronics and
discrimination threshold, and the phenomenon represents an intrinsic physical
effect that leads to the excellent time resolution of these sensors. Moreover,
we show that the TOA distribution is characterized by an intrinsic asymmetry,
due to the 3D geometry only, that becomes negligible in case of significant
electronics jitter
Giant planet engulfment by evolved giant stars: light curves, asteroseismology, and survivability
About ten percent of Sun-like (-) stars will engulf a - planet as they expand during the red giant branch (RGB) or
asymptotic giant branch (AGB) phase of their evolution. Once engulfed, these
planets experience a strong drag force in the star's convective envelope and
spiral inward, depositing energy and angular momentum. For these mass ratios,
the inspiral takes - years (- orbits);
the planet undergoes tidal disruption at a radius of . We use the
Modules for Experiments in Stellar Astrophysics (MESA) software instrument to
track the stellar response to the energy deposition while simultaneously
evolving the planetary orbit. For RGB stars, as well as AGB stars with planets, the star responds quasistatically but still
brightens measurably on a timescale of years. In addition, asteroseismic
indicators, such as the frequency spacing or rotational splitting, differ
before and after engulfment. For AGB stars, engulfment of a planet drives supersonic expansion of the envelope, causing a
bright, red, dusty eruption similar to a "luminous red nova." Based on the peak
luminosity, color, duration, and expected rate of these events, we suggest that
engulfment events on the AGB could be a significant fraction of low-luminosity
red novae in the Galaxy. We do not find conditions where the envelope is
ejected prior to the planet's tidal disruption, complicating the interpretation
of short-period giant planets orbiting white dwarfs as survivors of
common-envelope evolution.Comment: 24 pages, 11 figures, 1 table. Accepted to Ap
Peritoneal dialysis in older adults: evaluation of clinical, nutritional, metabolic outcomes, and quality of life
The number of older adults requiring dialysis is increasing worldwide, whereas the use of peritoneal dialysis (PD) in this population is lower respect to younger patients, despite the theoretical advantages of PD respect to hemodialysis. This is most likely due to the concern that older patients may not be able to correctly and safely manage PD.
We aimed to prospectively compare clinical, nutritional and metabolic outcomes and measures of quality of life between younger (<65years old) and older (≥65years old) patients on PD.
PD patients were enrolled and divided into 2 groups according to age (Group A < 65 years, Group B ≥ 65 years). Clinical and instrumental parameters, and quality of life were evaluated at baseline (start of PD) (T0) and at 24 months (T1). Technique survival, mortality, total number of hospitalizations, and the index of peritonitis (episodes of peritonitis/month) were also evaluated.
Fifty-one patients starting PD were enrolled. Group A included 22 patients (48.7±8.3 years), and Group B consisted of 29 patients (74.1 ± 6.4 years). At baseline, the 2 groups showed no differences in cognitive status, whereas Group A showed higher total cholesterol (p=0.03), LDL (p=0.03), and triglycerides (p=0.03) levels and lower body mass index (p=0.02) and carotid intima media thickness (p<0.0001) with respect to Group B. At T1 Group B showed, compared to baseline, a significant reduction in albumin (p<0.0001) and phosphorus (p=0.045) levels, while no significant differences on body composition, technique survival, total number of hospitalizations, index of peritonitis and quality of life indices were observed.
Our data do not show clinically relevant barriers to use PD in older adult patients, supporting its use in this population. Nutritional and metabolic parameters should be carefully monitored in older PD patients
Thin corrugated-edge shells inspired by Nervi’s dome: Numerical insight about their mechanical behaviour
During the last decades, the constant evolution of the construction systems has led to the possibility of carrying out increasingly complex architectural project. Among the wide range of construction systems, thin concrete shells with corrugated-edge stand out for their relevance.
In this paper, the mechanical behaviour of thin concrete corrugated-edge shell inspired by Nervi’s Flaminio dome has been analysed in detail, considering different load configurations (self-weight, uniform normal pressure and antisymmetric vertical load) and constraints (pure membrane vs. displacements restrained boundary conditions).
Non-linear static analysis has been performed to assess the vertical load-bearing capacity of the corrugatededge shell considering a Concrete Damaged Plasticity (CDP) constitutive model and linear and non-linear buckling analyses have been carried out to evaluate the effects of the corrugation on buckling behaviour.
The results obtained from linear and non-linear analyses have been compared with those obtained for a concrete thin smooth-edge shell having the same geometric global characteristics. The comparison highlighted improvements provided by corrugated-edge in terms of structural behaviour
Meaningful characterisation of perturbative theoretical uncertainties
We consider the problem of assigning a meaningful degree of belief to
uncertainty estimates of perturbative series. We analyse the assumptions which
are implicit in the conventional estimates made using renormalisation scale
variations. We then formulate a Bayesian model that, given equivalent initial
hypotheses, allows one to characterise a perturbative theoretical uncertainty
in a rigorous way in terms of a credibility interval for the remainder of the
series. We compare its outcome to the conventional uncertainty estimates in the
simple case of the calculation of QCD corrections to the e+e- -> hadrons
process. We find comparable results, but with important conceptual differences.
This work represents a first step in the direction of a more comprehensive and
rigorous handling of theoretical uncertainties in perturbative calculations
used in high energy phenomenology.Comment: 28 pages, 5 figures. Language modified in order to make it more
'bayesian'. No change in results. Version published in JHE
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