146 research outputs found
EXPERIENCIAS DEMOSTRATIVAS SOBRE LA GESTIÓN SOSTENIBLE DEL USO DEL AGUA DE RIEGO, PARA REDUCIR EL GASTO ENERGÉTICO Y LAS EMISIONES DE GEI
[ES] La elección de un marco de riego y el estudio de materiales que permitan
reducir las pérdidas de carga de una instalación, de manera que se consiga reducir
la demanda de presión y por tanto la factura eléctrica con la misma efectividad de
riego es clave, teniendo en cuenta que su vida útil es mayor de 20 años. Esto
supondrá un ahorro continuado en el tiempo de explotación de la instalación.
Además de este factor energético, es crucial determinar la Huella de Carbono de las
intalaciones de riego, así como establecer la comparativa de la Huella de Carbono
de los materiales utilizados en los dos marcos de riego (18 x 15T vs 12 x 15T) con
sus diferentes variantes de instalación.Goñi Labat, M.; Puig Arrastia, J.; Ederra Gil, I. (2015). EXPERIENCIAS DEMOSTRATIVAS SOBRE LA GESTIÓN SOSTENIBLE DEL USO DEL AGUA DE RIEGO, PARA REDUCIR EL GASTO ENERGÉTICO Y LAS EMISIONES DE GEI. En XXXIII CONGRESO NACIONAL DE RIEGOS. Valencia 16-18 junio de 2015. Editorial Universitat Politècnica de València. https://doi.org/10.4995/CNRiegos.2015.1448OC
APOE ɛ4 is associated with postictal confusion in patients with medically refractory temporal lobe epilepsy
This study examined the relationship between the APOE ɛ4 allele and postictal confusion in patients with medically intractable temporal lobe epilepsy (TLE). Patients with at least one ɛ4 allele (n = 22) were three times more likely to exhibit postictal confusion (68%) than the 63 patients without ɛ4 (43%). These preliminary results demonstrate that APOE ɛ4 is associated with an increased risk of postictal confusion in patients with medically intractable TLE, suggesting possible dysfunction in neuronal recovery mechanisms
Time singularities of correlators from Dirichlet conditions in AdS/CFT
Within AdS/CFT, we establish a general procedure for obtaining the leading
singularity of two-point correlators involving operator insertions at different
times. The procedure obtained is applied to operators dual to a scalar field
which satisfies Dirichlet boundary conditions on an arbitrary time-like surface
in the bulk. We determine how the Dirichlet boundary conditions influence the
singularity structure of the field theory correlation functions. New
singularities appear at boundary points connected by null geodesics bouncing
between the Dirichlet surface and the boundary. We propose that their
appearance can be interpreted as due to a non-local double trace deformation of
the dual field theory, in which the two insertions of the operator are
separated in time. The procedure developed in this paper provides a technical
tool which may prove useful in view of describing holographic thermalization
using gravitational collapse in AdS space.Comment: 30 pages, 3 figures. Version as in JHE
Thermalization from gauge/gravity duality: Evolution of singularities in unequal time correlators
We consider a gauge/gravity dual model of thermalization which consists of a
collapsing thin matter shell in asymptotically Anti-de Sitter space. A central
aspect of our model is to consider a shell moving at finite velocity as
determined by its equation of motion, rather than a quasi-static approximation
as considered previously in the literature. By applying a divergence matching
method, we obtain the evolution of singularities in the retarded unequal time
correlator , which probes different stages of the thermalization. We
find that the number of singularities decreases from a finite number to zero as
the gauge theory thermalizes. This may be interpreted as a sign of decoherence.
Moreover, in a second part of the paper, we show explicitly that the thermal
correlator is characterized by the existence of singularities in the complex
time plane. By studying a quasi-static state, we show the singularities at real
times originate from contributions of normal modes. We also investigate the
possibility of obtaining complex singularities from contributions of
quasi-normal modes.Comment: 35 pages, 4 figure
Holographic Evolution of Entanglement Entropy
We study the evolution of entanglement entropy in a 2-dimensional
equilibration process that has a holographic description in terms of a Vaidya
geometry. It models a unitary evolution in which the field theory starts in a
pure state, its vacuum, and undergoes a perturbation that brings it far from
equilibrium. The entanglement entropy in this set up provides a measurement of
the quantum entanglement in the system. Using holographic techniques we recover
the same result obtained before from the study of processes triggered by a
sudden change in a parameter of the hamiltonian, known as quantum quenches.
Namely, entanglement in 2-dimensional conformal field theories propagates with
velocity v^2=1. Both in quantum quenches and in the Vaidya model equilibration
is only achieved at the local level. Remarkably, the holographic derivation of
this last fact requires information from behind the apparent horizon generated
in the process of gravitational collapse described by the Vaidya geometry. In
the early stages of the evolution the apparent horizon seems however to play no
relevant role with regard to the entanglement entropy. We speculate on the
possibility of deriving a thermalization time for occupation numbers from our
analysis.Comment: 26 pages, 10 figure
Fast Scramblers, Horizons and Expander Graphs
We propose that local quantum systems defined on expander graphs provide a
simple microscopic model for thermalization on quantum horizons. Such systems
are automatically fast scramblers and are motivated from the membrane paradigm
by a conformal transformation to the so-called optical metric.Comment: 22 pages, 2 figures. Added further discussion in section 3. Added
reference
Thermal quenches in N=2* plasmas
We exploit gauge/gravity duality to study `thermal quenches' in a plasma of
the strongly coupled N=2* gauge theory. Specifically, we consider the response
of an initial thermal equilibrium state of the theory under variations of the
bosonic or fermionic mass, to leading order in m/T<<1. When the masses are made
to vary in time, novel new counterterms must be introduced to renormalize the
boundary theory. We consider transitions the conformal super-Yang-Mills theory
to the mass deformed gauge theory and also the reverse transitions. By
construction, these transitions are controlled by a characteristic time scale
\calt and we show how the response of the system depends on the ratio of this
time scale to the thermal time scale 1/T. The response shows interesting
scaling behaviour both in the limit of fast quenches with T\calt<<1 and slow
quenches with T\calt>>1. In the limit that T\calt\to\infty, we observe the
expected adiabatic response. For fast quenches, the relaxation to the final
equilibrium is controlled by the lowest quasinormal mode of the bulk scalar
dual to the quenched operator. For slow quenches, the system relaxes with a
(nearly) adiabatic response that is governed entirely by the late time profile
of the mass. We describe new renormalization scheme ambiguities in defining
gauge invariant observables for the theory with time dependant couplings.Comment: 78 pages, 17 figure
Holographic Geometry of Entanglement Renormalization in Quantum Field Theories
We study a conjectured connection between the AdS/CFT and a real-space
quantum renormalization group scheme, the multi-scale entanglement
renormalization ansatz (MERA). By making a close contact with the holographic
formula of the entanglement entropy, we propose a general definition of the
metric in the MERA in the extra holographic direction, which is formulated
purely in terms of quantum field theoretical data. Using the continuum version
of the MERA (cMERA), we calculate this emergent holographic metric explicitly
for free scalar boson and free fermions theories, and check that the metric so
computed has the properties expected from AdS/CFT. We also discuss the cMERA in
a time-dependent background induced by quantum quench and estimate its
corresponding metric.Comment: 42pages, 9figures, reference added, minor chang
Pathological Computed Tomography Features Associated with Adverse Outcomes after Mild Traumatic Brain Injury:A TRACK-TBI Study with External Validation in CENTER-TBI
Importance: A head computed tomography (CT) with positive results for acute intracranial hemorrhage is the gold-standard diagnostic biomarker for acute traumatic brain injury (TBI). In moderate to severe TBI (Glasgow Coma Scale [GCS] scores 3-12), some CT features have been shown to be associated with outcomes. In mild TBI (mTBI; GCS scores 13-15), distribution and co-occurrence of pathological CT features and their prognostic importance are not well understood. Objective: To identify pathological CT features associated with adverse outcomes after mTBI. Design, Setting, and Participants: The longitudinal, observational Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study enrolled patients with TBI, including those 17 years and older with GCS scores of 13 to 15 who presented to emergency departments at 18 US level 1 trauma centers between February 26, 2014, and August 8, 2018, and underwent head CT imaging within 24 hours of TBI. Evaluations of CT imaging used TBI Common Data Elements. Glasgow Outcome Scale-Extended (GOSE) scores were assessed at 2 weeks and 3, 6, and 12 months postinjury. External validation of results was performed via the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study. Data analyses were completed from February 2020 to February 2021. Exposures: Acute nonpenetrating head trauma. Main Outcomes and Measures: Frequency, co-occurrence, and clustering of CT features; incomplete recovery (GOSE scores <8 vs 8); and an unfavorable outcome (GOSE scores <5 vs ≥5) at 2 weeks and 3, 6, and 12 months. Results: In 1935 patients with mTBI (mean [SD] age, 41.5 [17.6] years; 1286 men [66.5%]) in the TRACK-TBI cohort and 2594 patients with mTBI (mean [SD] age, 51.8 [20.3] years; 1658 men [63.9%]) in an external validation cohort, hierarchical cluster analysis identified 3 major clusters of CT features: contusion, subarachnoid hemorrhage, and/or subdural hematoma; intraventricular and/or petechial hemorrhage; and epidural hematoma. Contusion, subarachnoid hemorrhage, and/or subdural hematoma features were associated with incomplete recovery (odds ratios [ORs] for GOSE scores <8 at 1 year: TRACK-TBI, 1.80 [95% CI, 1.39-2.33]; CENTER-TBI, 2.73 [95% CI, 2.18-3.41]) and greater degrees of unfavorable outcomes (ORs for GOSE scores <5 at 1 year: TRACK-TBI, 3.23 [95% CI, 1.59-6.58]; CENTER-TBI, 1.68 [95% CI, 1.13-2.49]) out to 12 months after injury, but epidural hematoma was not. Intraventricular and/or petechial hemorrhage was associated with greater degrees of unfavorable outcomes up to 12 months after injury (eg, OR for GOSE scores <5 at 1 year in TRACK-TBI: 3.47 [95% CI, 1.66-7.26]). Some CT features were more strongly associated with outcomes than previously validated variables (eg, ORs for GOSE scores <5 at 1 year in TRACK-TBI: neuropsychiatric history, 1.43 [95% CI.98-2.10] vs contusion, subarachnoid hemorrhage, and/or subdural hematoma, 3.23 [95% CI 1.59-6.58]). Findings were externally validated in 2594 patients with mTBI enrolled in the CENTER-TBI study. Conclusions and Relevance: In this study, pathological CT features carried different prognostic implications after mTBI to 1 year postinjury. Some patterns of injury were associated with worse outcomes than others. These results support that patients with mTBI and these CT features need TBI-specific education and systematic follow-up
Entanglement Entropy from a Holographic Viewpoint
The entanglement entropy has been historically studied by many authors in
order to obtain quantum mechanical interpretations of the gravitational
entropy. The discovery of AdS/CFT correspondence leads to the idea of
holographic entanglement entropy, which is a clear solution to this important
problem in gravity. In this article, we would like to give a quick survey of
recent progresses on the holographic entanglement entropy. We focus on its
gravitational aspects, so that it is comprehensible to those who are familiar
with general relativity and basics of quantum field theory.Comment: Latex, 30 pages, invited review for Classical and Quantum Gravity,
minor correction
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