682 research outputs found
Educando para la ciudadanía global. Una experiencia de investigación cooperativa entre docentes y profesionales de las ONGD
En este artículo se describe el proceso y se
presentan los resultados de un proyecto de investigación
cooperativa (IC) realizado en Valencia entre febrero
2010 y marzo 2011. Su objetivo fue reflexionar
sobre los significados y las prácticas educativas que docentes
de primaria, secundaria y universidad pueden
realizar en conjunto con las ONGD para potenciar la
ciudadanía global en el sistema educativo formal. El
artículo comienza con una reflexión sobre la educación
para el desarrollo. Posteriormente, se destacan
algunos aspectos relevantes de la IC, se describe el proceso
seguido y las técnicas empleadas y se discuten algunas
reflexiones que se dieron sobre la ciudadanía
global y los espacios educativos. Por último se detallan
unas conclusiones sobre lo que la metodología de la
IC puede aportar a la investigación en educación
Integration of stochastic models for long-term eruption forecasting into a Bayesian event tree scheme: a basis method to estimate the probability of volcanic unrest
Eruption forecasting refers, in general, to the
assessment of the occurrence probability of a given erup-
tive event, whereas volcanic hazards are normally associated
with the analysis of superficial and evident phenomena
that usually accompany eruptions (e.g., lava, pyroclastic
flows, tephra fall, lahars, etc.). Nevertheless, several hazards
of volcanic origin may occur in noneruptive phases dur-
ing unrest episodes. Among others, remarkable examples
are gas emissions, phreatic explosions, ground deforma-
tion, and seismic swarms. Many of such events may lead to
significant damages, and for this reason, the “risk” associ-
ated to unrest episodes could not be negligible with respect
to eruption-related phenomena. Our main objective in this
paper is to provide a quantitative framework to calculate
probabilities of volcanic unrest. The mathematical frame-
work proposed is based on the integration of stochastic mod-
els based on the analysis of eruption occurrence catalogs
into a Bayesian event tree scheme for eruption forecast-
ing and volcanic hazard assessment. Indeed, such models
are based on long-term eruption catalogs and in many
cases allow a more consistent analysis of long-term tem-
poral modulations of volcanic activity. The main result of
this approach is twofold: first, it allows to make inferences
about the probability of volcanic unrest; second, it allows
to project the results of stochastic modeling of the eruptive
history of a volcano toward the probabilistic assessment of
volcanic hazards. To illustrate the performance of the pro-
posed approach, we apply it to determine probabilities of
unrest at Miyakejima volcano, Japan
Chapter 3-20: From multi-risk assessment to multi-risk governance: Recommendations for future directions
Disasters caused by natural hazards can trigger chains of multiple natural and man-made hazardous events over different spatial and temporal scales. Multi-hazard and multi-risk assessments make it possible to take into account interactions between different risks. Classes of interactions include triggered events, cascade effects, and the rapid increase of vulnerability during successive hazards.
Recent research has greatly increased the risk assessment community's understanding of interactions between risks. Several international sets of guidelines and other documents now advocate adopting an all-hazard approach to risk assessments.
Nevertheless, barriers to the application of multirisk assessment remain. The challenges for the development of multi-risk approaches are related not only to the applicability of results, but also to the link between risk assessment and decision making, the interactions between science and practice in terms of knowledge transfer, and more generally to the development of capacities at the local level. So far, research has focused on the scientific aspects of risk assessment. But the institutional aspects, such as the issues arising when multi-risk assessment results need to be implemented within existing risk management regimes, are also important, though they have received less attention.
The project described here focused on the institutional context of disasters, which includes a variety of elements ranging from sociopolitical to governance components. It looked at how to maximize the benefits arising from, and overcome the barriers to, the implementation of a multihazard and multi-risk assessment approach within current risk management regimes. Working at two test sites, one in Naples and one in Guadeloupe, the research team engaged with local authorities and practitioners to better understand how to effectively implement the results of multi-risk assessment. Among the hazards considered were earthquakes, volcanic eruptions, landslides, floods, tsunamis, wildfires, cyclones, and marine inundation. Beside the practitioners working in the two test sites, risk and emergency managers from 11 countries also provided feedback. In total, more than 70 practitioners took part in the research
Towards spin injection from silicon into topological insulators: Schottky barrier between Si and Bi2Se3
A scheme is proposed to electrically measure the spin-momentum coupling in
the topological insulator surface state by injection of spin polarized
electrons from silicon. As a first approach, devices were fabricated consisting
of thin (<100nm) exfoliated crystals of Bi2Se3 on n-type silicon with
independent electrical contacts to silicon and Bi2Se3. Analysis of the
temperature dependence of thermionic emission in reverse bias indicates a
barrier height of 0.34 eV at the Si-Bi2Se3 interface. This robust Schottky
barrier opens the possibility of novel device designs based on sub-band gap
internal photoemission from Bi2Se3 into Si
A Brownian Model for Recurrent Volcanic Eruptions: an Application to Miyakejima Volcano (Japan)
The definition of probabilistic models as mathematical structures to describe the
response of a volcanic system is a plausible approach to characterize the temporal behavior
of volcanic eruptions, and constitutes a tool for long-term eruption forecasting. This kind
of approach is motivated by the fact that volcanoes are complex systems in which a com-
pletely deterministic description of the processes preceding eruptions is practically impos-
sible. To describe recurrent eruptive activity we apply a physically-motivated probabilistic
model based on the characteristics of the Brownian passage-time (BPT) distribution; the
physical process defining this model can be described by the steady rise of a state variable
from a ground state to a failure threshold; adding Brownian perturbations to the steady load-
ing produces a stochastic load-state process (a Brownian relaxation oscillator) in which an
eruption relaxes the load state to begin a new eruptive cycle. The Brownian relaxation os-
cillator and Brownian passage-time distribution connect together physical notions of unob-
servable loading and failure processes of a point process with observable response statistics.
The Brownian passage-time model is parameterized by the mean rate of event occurrence,
μ , and the aperiodicity about the mean, α . We apply this model to analyze the eruptive his-
tory of Miyakejima volcano, Japan, finding a value of 44.2(±6.5 years) for the μ parameter
and 0.51(±0.01) for the (dimensionless) α parameter. The comparison with other models
often used in volcanological literature shows that this pysically-motivated model may be a
good descriptor of volcanic systems that produce eruptions with a characteristic size. BPT
is clearly superior to the exponential distribution and the fit to the data is comparable to
other two-parameters models. Nonetheless, being a physically-motivated model, it provides
an insight into the macro-mechanical processes driving the system
Minimal lepton flavor violating realizations of minimal seesaw models
We study the implications of the global U(1)R symmetry present in minimal
lepton flavor violating implementations of the seesaw mechanism for neutrino
masses. In the context of minimal type I seesaw scenarios with a slightly
broken U(1)R, we show that, depending on the R-charge assignments, two classes
of generic models can be identified. Models where the right-handed neutrino
masses and the lepton number breaking scale are decoupled, and models where the
parameters that slightly break the U(1)R induce a suppression in the light
neutrino mass matrix. We show that within the first class of models,
contributions of right-handed neutrinos to charged lepton flavor violating
processes are severely suppressed. Within the second class of models we study
the charged lepton flavor violating phenomenology in detail, focusing on mu to
e gamma, mu to 3e and mu to e conversion in nuclei. We show that sizable
contributions to these processes are naturally obtained for right-handed
neutrino masses at the TeV scale. We then discuss the interplay with the
effects of the right-handed neutrino interactions on primordial B - L
asymmetries, finding that sizable right-handed neutrino contributions to
charged lepton flavor violating processes are incompatible with the requirement
of generating (or even preserving preexisting) B - L asymmetries consistent
with the observed baryon asymmetry of the Universe.Comment: 21 pages, 4 figures; version 2: Discussion on possible generic models
extended, typos corrected, references added. Version matches publication in
JHE
Thermal stabilization of metal matrix nanocomposites by nanocarbon reinforcements
Metal matrix composites reinforced by nanocarbon materials, such as carbon nanotubes or nanodiamonds, are very promising materials for a large number of functional and structural applications. Carbon
nanotubes and nanodiamonds-reinforced metal matrix nanocomposites with different concentrations of
the carbon phase were processed by high-pressure torsion deformation and the evolving nanostructures
were thoroughly analyzed by electron microscopy. Particular emphasis is placed on the thermal stability
of the nanocarbon reinforced metal matrix composites, which is less influenced by the amount of added
nanocarbon reinforcements than by the nanocarbon reinforcement type and its distribution in the metal
matrix
Reactor mixing angle from hybrid neutrino masses
In terms of its eigenvector decomposition, the neutrino mass matrix (in the
basis where the charged lepton mass matrix is diagonal) can be understood as
originating from a tribimaximal dominant structure with small deviations, as
demanded by data. If neutrino masses originate from at least two different
mechanisms, referred to as "hybrid neutrino masses", the experimentally
observed structure naturally emerges provided one mechanism accounts for the
dominant tribimaximal structure while the other is responsible for the
deviations. We demonstrate the feasibility of this picture in a fairly
model-independent way by using lepton-number-violating effective operators,
whose structure we assume becomes dictated by an underlying flavor
symmetry. We show that if a second mechanism is at work, the requirement of
generating a reactor angle within its experimental range always fixes the solar
and atmospheric angles in agreement with data, in contrast to the case where
the deviations are induced by next-to-leading order effective operators. We
prove this idea is viable by constructing an -based ultraviolet
completion, where the dominant tribimaximal structure arises from the type-I
seesaw while the subleading contribution is determined by either type-II or
type-III seesaw driven by a non-trivial singlet (minimal hybrid model).
After finding general criteria, we identify all the symmetries
capable of producing such -based minimal hybrid models.Comment: 18 pages, 5 figures. v3: section including sum rules added, accepted
by JHE
Phonon assisted dynamical Coulomb blockade in a thin suspended graphite sheet
The differential conductance in a suspended few layered graphene sample is
fou nd to exhibit a series of quasi-periodic sharp dips as a function of bias
at l ow temperature. We show that they can be understood within a simple model
of dyn amical Coulomb blockade where energy exchanges take place between the
charge carriers transmitted trough the sample and a dissipative electromagnetic
envir onment with a resonant phonon mode strongly coupled to the electrons
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