13,538 research outputs found
Stability mapping of bipartite tight-binding graphs with losses and gain: symmetry and beyond
We consider bipartite tight-binding graphs composed by nodes split into
two sets of equal size: one set containing nodes with on-site loss, the other
set having nodes with on-site gain. The nodes are connected randomly with
probability . We give a rationale for the relevance of such "throttle/brake"
coupled systems (physically open systems) to grasp the stability issues of
complex networks in areas such as biochemistry, neurons or economy, for which
their modelling in terms of non-hermitian Hamiltonians is still in infancy.
Specifically, we measure the connectivity between the two sets with the
parameter , which is the ratio of current adjacent pairs over the total
number of possible adjacent pairs between the sets. For general
undirected-graph setups, the non-hermitian Hamiltonian of
this model presents pseudo-Hermiticity, where is the loss/gain
strength. However, we show that for a given graph setup
becomes symmetric. In both scenarios (pseudo-Hermiticity and symmetric), depending on the parameter combination, the spectra of
can be real even when it is non-hermitian. Thus, we
numerically characterize the average fractions of real and imaginary
eigenvalues of as a function of the parameter set
. We demonstrate, for both setups, that there is a well
defined sector of the plane (which grows with ) where the
spectrum of is predominantly real.Comment: 10 pages, 9 figure
Spectral and localization properties of random bipartite graphs
Bipartite graphs are often found to represent the connectivity between the
components of many systems such as ecosystems. A bipartite graph is a set of
nodes that is decomposed into two disjoint subsets, having and
vertices each, such that there are no adjacent vertices within the same set.
The connectivity between both sets, which is the relevant quantity in terms of
connections, can be quantified by a parameter that equals the
ratio of existent adjacent pairs over the total number of possible adjacent
pairs. Here, we study the spectral and localization properties of such random
bipartite graphs. Specifically, within a Random Matrix Theory (RMT) approach,
we identify a scaling parameter that fixes the
localization properties of the eigenvectors of the adjacency matrices of random
bipartite graphs. We also show that, when ) the
eigenvectors are localized (extended), whereas the
localization--to--delocalization transition occurs in the interval
. Finally, given the potential applications of our findings, we
round off the study by demonstrating that for fixed , the spectral
properties of our graph model are also universal.Comment: 17 pages, 10 figure
Harmonized cross-sectional surveys focused on fluid intake in children, adolescents and adults: The Liq.In7 initiative
Objective: To assess the intake of water and all other beverages in children, adolescents and adults. Methods: Three thousand six hundred eleven children (8 ± 2 years), 8, 109 adolescents (13 ± 2 years) and 16, 276 adults (40 ± 14 years) (47% men) were recruited in 15 cross-sectional surveys (liquid intake across 7 days, Liq.In7 study) and completed a 7-day fluid-specific record to assess total fluid intake (TFI), where TFI was defined as the sum of drinking water and other type of beverages. Results: The median TFI was 1.2, 1.2 and 1.8 liters/day in children, adolescents and adults respectively, with important differences observed between countries. Only 39% of children, 25% of adolescents and 51% of adults met the European Food Safety Authority adequate intake (AI) recommendations of water from fluids. In the surveys of Spain, France, Belgium, Germany, Turkey, Iran, Indonesia and China, water was the major contributor (47-78%) to TFI. In the adult surveys of UK, Poland, Japan and Argentina, hot beverages were the highest contributor to TFI. The fluid intake of children and adolescents in Mexico, Brazil, Argentina and Uruguay was characterized by a contribution of juices and sweet beverages that was as important as the contribution of water to TFI. Conclusion: Given that a relatively high proportion of subjects, especially children and adolescents, failed to meet the recommended AI of water from fluids and that water intake was not the highest contributor to TFI in all countries, undertaking actions to increase water intake are warranted
Small-scale magnetic flux emergence in the quiet Sun
Small bipolar magnetic features are observed to appear in the interior of
individual granules in the quiet Sun, signaling the emergence of tiny magnetic
loops from the solar interior. We study the origin of those features as part of
the magnetoconvection process in the top layers of the convection zone. Two
quiet-Sun magnetoconvection models, calculated with the
radiation-magnetohydrodynamic (MHD) Bifrost code and with domain stretching
from the top layers of the convection zone to the corona, are analyzed. Using
3D visualization as well as a posteriori spectral synthesis of Stokes
parameters, we detect the repeated emergence of small magnetic elements in the
interior of granules, as in the observations. Additionally, we identify the
formation of organized horizontal magnetic sheets covering whole granules. Our
approach is twofold, calculating statistical properties of the system, like
joint probability density functions (JPDFs), and pursuing individual events via
visualization tools. We conclude that the small magnetic loops surfacing within
individual granules in the observations may originate from sites at or near the
downflows in the granular and mesogranular levels, probably in the first 1 or
1.5 Mm below the surface. We also document the creation of granule-covering
magnetic sheet-like structures through the sideways expansion of a small
subphotospheric magnetic concentration picked up, and pulled out of the
interior, by a nascent granule. The sheet-like structures we found in the
models may match the recent observations of Centeno et al. (2017).Comment: 9 pages, 5 figures, Published in The Astrophysical Journal Letter
Lower Cretaceous (Hauterivian-Albian) ammonite biostratigraphy in the Maestrat Basin (E Spain)
Peer reviewedPublisher PD
Planificador estratégico para operaciones de rescate mediante vehículos terrestres no tripulados
El despliegue de plataformas robóticas como apoyo
a la gestión de situaciones de emergencia constituye
un reto que persigue mejorar la eficiencia
en misiones de búsqueda y rescate. Este artículo
propone un planificador estratégico para el rescate
de víctimas mediante un equipo de robots terrestres.
Este sistema inteligente permitirá planificar
las trayectorias para acceder a las víctimas de
acuerdo con su ubicación y prioridad de asistencia
médica (triaje). Para la planificación se propone
una nueva variante del algoritmo “ fast marching
method” (FMM). En este trabajo se ofrecen resultados
preliminares mediante un ejemplo de aplicación
en condiciones simuladas.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.
Proyecto nacional DPI2015-65186-R.
Ayuda BES-2016-077022 del Fondo Social Europeo FSE
A comparison of drinking behavior using a harmonized methodology (Liq.In 7) in six countries
Purpose: To assess drinking occasions (volume and type) according to consumption with food in or outside meals, and location, for six countries. Methods: A total of 10, 521 participants aged 4–65 years from Argentina, Brazil, China, Indonesia, Mexico and Uruguay completed a validated 7-day fluid intake record. For each drinking event, the volume consumed, the fluid type, the location of intake, and whether the drink was accompanied by food (meal or snack) or not, was recorded. Results: Similar drinking behaviors were found in Mexico and Argentina; fluid intake during meals was 48 and 45% of total fluid intake (TFI), respectively. In Brazil (55%), Indonesia (58%) and China (66%) most fluid was consumed without food. In Uruguay, 34% of TFI was with a main meal, 31% with food between meals and 35% without food. Indonesia had the highest median (25–75th percentile) TFI; 2520 (1750–3347) mL/day, and China the lowest 1138 (818–3347) mL/day. Water was consumed with meals for 37% of Chinese and 87% of Indonesian participants, while the four Latin-American American countries showed a preference for sweet drinks; 54% in Mexico, 67% in Brazil, 55% in Argentina and 59% in Uruguay. Diversity in fluid type was noted when drinking with food between meals. Apart from China, most drinking occasions (> 75%) occurred at home. Conclusions: Three distinct drinking behaviors were identified, namely, drinking with meals, drinking as a stand-alone activity, and a type of ‘grazing’ (i.e., frequent drinks throughout the day) behavior. Most drinking occasions occurred at home
Relevance of assessment methods for fluid intake
Reliable data at population level are essential to firmly establish links between fluid intake, hydration and health, investigate dose-response relationships and develop meaningful public health strategies or reference intake values. However, limited research exists regarding the most appropriate methodology for assessing beverage or total fluid intake (TFI). To date, methodologies have been developed to assess food and nutrient intake without due consideration of water or fluid intake behavior. A recent crossover study showed that a 24-hour food recall significantly underestimated mean TFI by 382 ml (95% CI 299-465) compared with a fluid specific 7-day record. The authors postulated that this average difference was mainly the result of missed drinking acts between meals a 24-hour recall was used. Using a 7-day record administered in paper form or on-line has also been shown to lead to a significantly different mean TFI of 129 ml. Therefore, the choice of methodology might result in measurement errors that limit between-survey or between-country comparisons. Such errors may contribute to variations in estimates of TFI that cannot be explained by differences in climate, physical activity or cultural habits. A recent survey confirmed the variation in methodologies used in European national dietary surveys. Since these surveys form the basis for setting adequate intakes for total water intake, measurement error between surveys should be limited, highlighting the need for the development of a consistent methodology that is validated for water and TFI estimation
Pueblos de indios Postconquista de la jurisdicción de Santiago del Estero : Investigación en las fuentes
Se analizaron fuentes editas e inéditas para localizar “pueblos indios” con los cuales los españoles hicieron contacto en los primeros años de la conquista del territorio de Santiago del Estero.Prime and late sources were analyzed in search of the indian peoples with which the Spaniards were in touch in the first years of the conquest of the territory of Santiago del Estero.Sociedad Argentina de Antropologí
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