602 research outputs found
Production of atomic hydrogen by cosmic rays in dark clouds
The presence of small amounts of atomic hydrogen, detected as absorption dips
in the 21 cm line spectrum, is a well-known characteristic of dark clouds. The
abundance of hydrogen atoms measured in the densest regions of molecular clouds
can be only explained by the dissociation of H due to cosmic rays. We want
to assess the role of Galactic cosmic rays in the formation of atomic hydrogen,
by using recent developments in the characterisation of the low-energy spectra
of cosmic rays and advances in the modelling of their propagation in molecular
clouds. We model the attenuation of the interstellar cosmic rays entering a
cloud and compute the dissociation rate of molecular hydrogen due to collisions
with cosmic-ray protons and electrons as well as fast hydrogen atoms. We
compare our results with the available observations. The cosmic-ray
dissociation rate is entirely determined by secondary electrons produced in
primary ionisation collisions. These secondary particles constitute the only
source of atomic hydrogen at column densities above cm. We
also find that the dissociation rate decreases with column density, while the
ratio between the dissociation and ionisation rates varies between about 0.6
and 0.7. From comparison with observations we conclude that a relatively flat
spectrum of interstellar cosmic-ray protons, as the one suggested by the most
recent Voyager 1 data, can only provide a lower bound for the observed atomic
hydrogen fraction. An enhanced spectrum of low-energy protons is needed to
explain most of the observations. Our findings show that a careful description
of molecular hydrogen dissociation by cosmic rays can explain the abundance of
atomic hydrogen in dark clouds. An accurate characterisation of this process at
high densities is crucial for understanding the chemical evolution of
star-forming regions.Comment: 7 pages, 7 figures, accepted by Astronomy and Astrophysic
A simple figure of merit to identify the first layer to degrade and fail in dual layer SiOx/HfO2 gate dielectric stacks
Understanding the degradation dynamics and the breakdown sequence of a bilayer high-k (HK) gate dielectric stack is crucial for the improvement of device reliability. We present a new Figure of Merit (FoM), the IL/HK Degradation Index, that depends on fundamental materials properties (the dielectric breakdown strength and the dielectric constant) and can be used to easily and quickly identify the first layer to degrade and fail in a bilayer SiO2/HK dielectric stack. Its dependence on IL and HK material parameters is investigated and its validity is demonstrated by means of accurate physics-based simulations of the degradation process. The proposed FoM can be easily used to understand the degradation dynamics of the gate dielectric stack, providing critical insights for device reliability improvement
Violenza e paci private in una città di Romagna: Imola nel Quattrocento
Paci e tregue sono state studiate su 280 documenti d'archivio ancora inediti. Emerge, dal materiale raccolto, un quadro di impressionante violenza in ambiente rurale che le magistrature cittadine non riescono a contenere. Di tale instabilit\ue0 trassero profitto le due famiglie in lotta per il potere ad Imola, i guelfi Sassatelli e i ghibellini Vaini, ingrossando le file dei propri adepti in vista dello scontro finale a met\ue0 Cinquecento
The Orion-Taurus ridge: a synchrotron radio loop at the edge of the Orion-Eridanus superbubble
Large-scale synchrotron loops are recognized as the main source of diffuse
radio-continuum emission in the Galaxy at intermediate and high Galactic
latitudes. Their origin, however, remains rather unexplained. Using a
combination of multi-frequency data in the radio band of total and polarized
intensities, for the first time in this letter, we associate one arc --
hereafter, the Orion-Taurus ridge -- with the wall of the most prominent
stellar-feedback blown shell in the Solar neighborhood, namely the
Orion-Eridanus superbubble. We traced the Orion-Taurus ridge using 3D maps of
interstellar dust extinction and column-density maps of molecular gas, . We found the Orion-Taurus ridge at a distance of 400\,pc, with a
plane-of-the-sky extent of \,pc. Its median value is
cm. Thanks to the broadband
observations below 100 MHz of the Long Wavelength Array, we also computed the
low-frequency spectral-index map of synchrotron emissivity, , in the
Orion-Taurus ridge. We found a flat distribution of with a median value
of that we interpreted in terms of depletion of
low-energy ( GeV) cosmic-ray electrons in recent supernova remnants (
- yrs). Our results are consistent with plane-of-the-sky magnetic-field
strengths in the Orion-Taurus ridge larger than a few tens of G (G). We report the first detection of diffuse synchrotron emission from
cold-neutral, partly molecular, gas in the surroundings of the Orion-Eridanus
superbubble. This observation opens a new perspective to study the multiphase
and magnetized interstellar medium with the advent of future high-sensitivity
radio facilities, such as the C-Band All-Sky Survey and the Square Kilometre
Array.Comment: Accepted for publication in Astronomy & Astrophysic
Pakakuna gardens centro geriátrico
Pakakuna Gardens fue concebido con la idea de crear un centro geriátrico que
cuente con todos los elementos para crear una vida placentera para el adulto mayor.
Adicionalmente fue creado para permitir que personas de tercera edad que
desean jubilarse, tengan la opción de vivir en un lugar en las afueras de la ciudad, con
gran cantidad de áreas verdes y que cuente con servicios cerca de sus hogares. Por
otro lado la propuesta permite también el crear un lugar de oportunidades turísticas,
ya que personas extranjeras que desean retirarse puedan hacer en un lugar elegante y
sobre todo que cumpla con la accesibilidad y funcionalidad que las personas de
tercera edad necesitan.
Dentro de la propuesta realizada se crean espacios residenciales, la
implementación de un ancianato, la redistribución y creación de áreas comerciales y
de recreación
Investigation of trapping/detrapping mechanisms in Al2O3 electron/hole traps and their influence on TANOS memory operations
The purpose of this work is to investigate the physics of electron/hole trapping/detrapping mechanisms in Al2O3. Combining I-V and C-V measurements with a physical model we derive the energy levels of electron/hole traps and the location of electron/hole charge. The influence of electron/hole alumina traps on TANOS operations and reliability is investigated
Metabolic connectivity of resting-state networks in alpha synucleinopathies, from prodromal to dementia phase
Previous evidence suggests that the derangement of large-scale brain networks reflects structural, molecular, and functional mechanisms underlying neurodegenerative diseases. Although the alterations of multiple large-scale brain networks in Parkinson’s disease (PD) and Dementia with Lewy Bodies (DLB) are reported, a comprehensive study on connectivity reconfiguration starting from the preclinical phase is still lacking. We aimed to investigate shared and disease-specific changes in the large-scale networks across the Lewy Bodies (LB) disorders spectrum using a brain metabolic connectivity approach. We included 30 patients with isolated REM sleep behavior disorder (iRBD), 28 with stable PD, 30 with DLB, and 30 healthy controls for comparison. We applied seed-based interregional correlation analyses (IRCA) to evaluate the metabolic connectivity in the large-scale resting-state networks, as assessed by [18F]FDG-PET, in each clinical group compared to controls. We assessed metabolic connectivity changes by applying the IRCA and specific connectivity metrics, such as the weighted and unweighted Dice similarity coefficients (DC), for the topographical similarities. All the investigated large-scale brain resting-state networks showed metabolic connectivity alterations, supporting the widespread involvement of brain connectivity within the alpha-synuclein spectrum. Connectivity alterations were already evident in iRBD, severely affecting the posterior default mode, attentive and limbic networks. Strong similarities emerged in iRBD and DLB that showed comparable connectivity alterations in most large-scale networks, particularly in the posterior default mode and attentive networks. Contrarily, PD showed the main connectivity alterations limited to motor and somatosensory networks. The present findings reveal that metabolic connectivity alterations in the large-scale networks are already present in the early iRBD phase, resembling the DLB metabolic connectivity changes. This suggests and confirms iRBD as a risk condition for progression to the severe LB disease phenotype. Of note, the neurobiology of stable PD supports its more benign phenotype
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