5,673 research outputs found
High-Resolution Observations of Interstellar Ca I Absorption -- Implications for Depletions and Electron Densities in Diffuse Clouds
We present high-resolution (FWHM ~ 0.3-1.5 km/s) spectra of interstellar Ca I
absorption toward 30 Galactic stars. Comparisons of the column densities of Ca
I, Ca II, K I, and other species -- for individual components identified in the
line profiles and also when integrated over entire lines of sight -- yield
information on relative electron densities and depletions. There is no obvious
relationship between the ratio N(Ca I)/N(Ca II) [equal to n_e/(Gamma/alpha_r)
for photoionization equilibrium] and the fraction of hydrogen in molecular form
f(H2) (often taken to be indicative of the local density n_H). For a smaller
sample of sightlines for which the thermal pressure (n_H T) and local density
can be estimated via analysis of the C I fine-structure excitation, the average
electron density inferred from C, Na, and K (assuming photoionization
equilibrium) seems to be independent of n_H and n_H T. While the n_e obtained
from the ratio N(Ca I)/N(Ca II) is often significantly higher than the values
derived from other elements, the patterns of relative n_e derived from
different elements show both similarities and differences for different lines
of sight -- suggesting that additional processes besides photoionization and
radiative recombination commonly and significantly affect the ionization
balance of heavy elements in diffuse IS clouds. Such additional processes may
also contribute to the (apparently) larger than expected fractional ionizations
(n_e/n_H) found for some lines of sight with independent determinations of n_H.
In general, inclusion of ``grain-assisted'' recombination does reduce the
inferred n_e, but it does not reconcile the n_e estimated from different
elements. The depletion of calcium may have a much weaker dependence on density
than was suggested by earlier comparisons with CH and CN.Comment: aastex, 70 pages, accepted to ApJ
Speed and entropy of an interacting continuous time quantum walk
We present some dynamic and entropic considerations about the evolution of a
continuous time quantum walk implementing the clock of an autonomous machine.
On a simple model, we study in quite explicit terms the Lindblad evolution of
the clocked subsystem, relating the evolution of its entropy to the spreading
of the wave packet of the clock. We explore possible ways of reducing the
generation of entropy in the clocked subsystem, as it amounts to a deficit in
the probability of finding the target state of the computation. We are thus
lead to examine the benefits of abandoning some classical prejudice about how a
clocking mechanism should operate.Comment: 25 pages, 14 figure
Terremoti probabili in Italia tra il 2000 e il 2030: elementi per la definizione di priorità per la riduzione del rischio sismico
The main purpose of Task 3.2 was to introduce the role of local geology in the seismic hazard evaluation at national scale. This was achieved by grouping the geological formation of the 1:500,000 Italian geological map into three classes A, B, C according to the EuroCode8 provisions (GCM, Geological-Class Map). These classes are associated to a variation of the ground motion due to the different seismic properties of the lithologies included in each group (ANNEX 1).
For a critical evaluation of the proposed approach, we have checked the occurrence of a systematic increment of macroseismic intensity as a function of the geological classes at a national scale. The study of distribution of Intensity anomalies associated to the 3 classes show a statistical significant tendency of positive anomalies to be related to classes B and C and negative anomalies to be related to class A (ANNEX 2).
We then assumed that the effect of local geology on ground motion is the one described by variation of elastic response spectra prescribed by EC8 (in terms of PGA, PSA, Housner Intensity). This variation is controlled by a set of parameters depending on the soil classes and earthquake magnitude (ANNEX 3).
We compared the increment factors to those deriving from a numerical simulation of the Città di Castello (Central Italy) basin where many geological and seismological data were available. The results at local scale show a good fit (within a factor of two) with the variations of hazard parameters for classes B e C (ANNEX 4).
Moreover, we launched a national-scale enquiry over the 8101 Italian Municipalities whose main goal was the estimation of the buildings distribution on the three soil classes corresponding to those of the CGM. We collected and organized the received forms in a database (see product 3). The comparison at a Municipality-scale of the GCM and the questionnaire results shows that their information is complementary, the first referring this percentage to the housing, the latter considering all the municipality territory (ANNEX 5). The questionnaire is a good data gathering tool for pointing out area where more detailed microzonation investigation must be performed. The questionnaire can be a powerful tool to increase awareness of Municipality Administration and the lack of involvement could be overcome by coordination at the Region levels.
Products
1. National geologic map at 1:500,000 scale modified according to the EC8 soil classes (geological-class map, GCM)
2. Map of the geology-dependent correction of hazard parameters
3. Database of the Italian municipalities containing information about the distribution of buildings in relation to the surface geology as well as geographical and geotechnical data availability.
The three products are organized in an attached CD and they are included in the GIS of the project.Gruppo Nazionale per la Difesa dai TerremotiUnpublished1.1. TTC - Monitoraggio sismico del territorio nazionaleope
Symmetries in Classical Field Theory
The multisymplectic description of Classical Field Theories is revisited,
including its relation with the presymplectic formalism on the space of Cauchy
data. Both descriptions allow us to give a complete scheme of classification of
infinitesimal symmetries, and to obtain the corresponding conservation laws.Comment: 70S05; 70H33; 55R10; 58A2
Lack of uniqueness for weak solutions of the incompressible porous media equation
In this work we consider weak solutions of the incompressible 2-D porous
media equation. By using the approach of De Lellis-Sz\'ekelyhidi we prove
non-uniqueness for solutions in in space and time.Comment: 23 pages, 2 fugure
Nonlinear Dynamics of the Perceived Pitch of Complex Sounds
We apply results from nonlinear dynamics to an old problem in acoustical
physics: the mechanism of the perception of the pitch of sounds, especially the
sounds known as complex tones that are important for music and speech
intelligibility
Vortioxetine in major depressive disorder : from mechanisms of action to clinical studies. An updated review
Introduction: Vortioxetine is a multimodal-acting antidepressant that provides improvements on cognitive function aside from antidepressants and anxiolytic effects. Vortioxetine has been found to be one of the most effective and best tolerated options for major depressive disorder (MDD) in head-to-head trials. Areas covered: The present review intends to gather the most relevant and pragmatic data of vortioxetine in MDD, specially focusing on new studies that emerged between 2015 and 2020. Expert opinion: Vortioxetine is the first antidepressant that has shown improvements both in depression and cognitive symptoms, due to the unique multimodal mechanism of action that combine the 5-HT reuptake inhibition with modulations of other key pre- and post-synaptic 5-HT receptors (agonism of 5-HT receptor, partial agonism of 5-HT receptor, and antagonism of 5-HT, 5-HT and 5-HT receptors). This new mechanism of action can explain the dose-dependent effect and can be responsible for its effects on cognitive functioning and improved tolerability profile. Potential analgesic and anti-inflammatory properties observed in preclinical studies as well as interesting efficacy and tolerability results of clinical studies with specific target groups render it a promising therapeutic option for patients with MDD and concomitant conditions (as menopause symptoms, pain, inflammation, apathy, sleep and/or metabolic abnormalities)
Scale-up of CLC oxygen carriers for gaseous fuels
Chemical Looping Combustion, CLC, is one of the most promising processes to capture CO2 at a low cost. It is based on the transfer of the oxygen from air to the fuel by using a solid oxygen carrier that circulates in dual fluidized bed systems. The CO2 capture is inherent to this process, as the air does not get mixed with the fuel. However, the CLC process is still under development waiting for a large scale demonstration experience.
The key issue in the system performance is the oxygen carrier material. The oxygen carrier must fulfil several characteristics such as high reactivity and good fluidization properties, that will rely on their redox system and the support. Therefore, the identification of raw materials, available at multi-tonn scale at a competitive price, is one of requirements for the success of the technology.
Promising impregnated oxygen carriers, based on copper and iron, have been developed to perform well for gaseous fuels (CH4, syngas , LHC..), although they were prepared from not commercially scalable production supports. In this work, the performance of different impregnated materials, prepared with commercial-scale supports, was analyzed during methane combustion in a continuous 500 Wth CLC unit to identify the best material based on reactivity, attrition resistance and sulfur tolerance.
A copper-based material with improved performance than the reference material was identified and therefore proposed as the best oxygen carrier for scale-up CLC technology for gaseous fuels
Invariant Forms and Automorphisms of Locally Homogeneous Multisymplectic Manifolds
It is shown that the geometry of locally homogeneous multisymplectic
manifolds (that is, smooth manifolds equipped with a closed nondegenerate form
of degree > 1, which is locally homogeneous of degree k with respect to a local
Euler field) is characterized by their automorphisms. Thus, locally homogeneous
multisymplectic manifolds extend the family of classical geometries possessing
a similar property: symplectic, volume and contact. The proof of the first
result relies on the characterization of invariant differential forms with
respect to the graded Lie algebra of infinitesimal automorphisms, and on the
study of the local properties of Hamiltonian vector fields on locally
multisymplectic manifolds. In particular it is proved that the group of
multisymplectic diffeomorphisms acts (strongly locally) transitively on the
manifold. It is also shown that the graded Lie algebra of infinitesimal
automorphisms of a locally homogeneous multisymplectic manifold characterizes
their multisymplectic diffeomorphisms.Comment: 25 p.; LaTeX file. The paper has been partially rewritten. Some
terminology has been changed. The proof of some theorems and lemmas have been
revised. The title and the abstract are slightly modified. An appendix is
added. The bibliography is update
Faint solar analogs: at the limit of no reddening
The flux distribution of solar analogs is required for calculating the
spectral albedo of Solar System bodies such as asteroids and trans-Neptunian
objects. Ideally a solar analog should be comparably faint as the target of
interest, but only few analogs fainter than V = 9 were identified so far. Only
atmospheric parameters equal to solar guarantee a flux distribution equal to
solar as well, while only photometric colors equal to solar do not. Reddening
is also a factor to consider when selecting faint analog candidates. We
implement the methodology for identifying faint analogs at the limit of
precision allowed by current spectroscopic surveys. We quantify the precision
attainable for the atmospheric parameters effective temperature (),
metallicity ([Fe/H]), surface gravity (log ) when derived from moderate low
resolution (R=8000) spectra with S/N . We calibrated and
[Fe/H] as functions of equivalent widths of spectral indices by means of the
PCA regression. We derive log , mass, radius, and age from the atmospheric
parameters, Gaia parallaxes and evolutionary tracks. We obtained
/[Fe/H]/log with precision of 97 K/0.06 dex/0.05 dex. We identify
five solar analogs with (located at pc): HIP 991, HIP
5811, HIP 69477, HIP 55619 and HIP 61835. Other six stars have close
to solar but slightly lower [Fe/H]. Our analogs show no evidence of reddening
but for four stars, which present mag, translating to at
least a 200 K decrease in photometric .Comment: Paper accepted. Fundamental parameters of the solar analogs are in
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