2,641 research outputs found
Recurrence relations and vector equilibrium problems arising from a model of non-intersecting squared Bessel paths
In this paper we consider the model of non-intersecting squared Bessel
processes with parameter , in the confluent case where all particles
start, at time , at the same positive value , remain positive, and
end, at time , at the position . The positions of the paths have a
limiting mean density as which is characterized by a vector
equilibrium problem. We show how to obtain this equilibrium problem from
different considerations involving the recurrence relations for multiple
orthogonal polynomials associated with the modified Bessel functions.
We also extend the situation by rescaling the parameter , letting it
increase proportionally to as increases. In this case we also analyze
the recurrence relation and obtain a vector equilibrium problem for it.Comment: 28 pages, 10 figure
Multi-GPU maximum entropy image synthesis for radio astronomy
The maximum entropy method (MEM) is a well known deconvolution technique in
radio-interferometry. This method solves a non-linear optimization problem with
an entropy regularization term. Other heuristics such as CLEAN are faster but
highly user dependent. Nevertheless, MEM has the following advantages: it is
unsupervised, it has a statistical basis, it has a better resolution and better
image quality under certain conditions. This work presents a high performance
GPU version of non-gridding MEM, which is tested using real and simulated data.
We propose a single-GPU and a multi-GPU implementation for single and
multi-spectral data, respectively. We also make use of the Peer-to-Peer and
Unified Virtual Addressing features of newer GPUs which allows to exploit
transparently and efficiently multiple GPUs. Several ALMA data sets are used to
demonstrate the effectiveness in imaging and to evaluate GPU performance. The
results show that a speedup from 1000 to 5000 times faster than a sequential
version can be achieved, depending on data and image size. This allows to
reconstruct the HD142527 CO(6-5) short baseline data set in 2.1 minutes,
instead of 2.5 days that takes a sequential version on CPU.Comment: 11 pages, 13 figure
Quantitative Structure-Property Relationships for Predicting the Retention Indices of Fragrances on Stationary Phases of Different Polarity
El objetivo de este trabajo fue el desarrollo de relaciones cuantitativas estructura–propiedad predictivas para el modelado de índices de retención (I) de fragancias, medidas en tres fases estacionarias de diferente polaridad: DB–225MS, HP5–MS y HP–1. Se ha prestado particular atención al curado de los datos experimentales. Posteriormente, se usó el método de subconjuntos balanceados (BSM) para dividir cada base de datos en grupos de calibración, validación y predicción. Los modelos se construyeron a partir de 1819 descriptores moleculares independientes de la conformación, los cuales fueron analizados mediante el método de reemplazo (RM) para la selección de los mismos, con la finalidad de obtener los mejores modelos. Para la fase estacionaria DB–225MS se obtuvo un modelo basado en cuatro descriptores, mientras que para las columnas HP5–MS y HP–1 se propusieron modelos con tres descriptores. Los modelos fueron validados mediante validación cruzada de dejar–uno–fuera y dejar–varios–fuera, así como otros criterios de validación. Adicionalmente, con la finalidad de cumplir los principios propuestos por la Organization for Economic Co–operation and Development (OECD), la capacidad predictiva de los modelos se evaluó mediante la predicción de los índices de retención del grupo externo de predicción, el dominio de aplicabilidad fue apropiadamente definido y se realizó una interpretación de cada descriptor molecular involucrado.The purpose of this work was to develop predictive quantitative structure–property relationships for modeling the retention indices (I) of fragrances measured in three stationary phases of different polarities: DB–225MS, HP5–MS and HP–1. Attention was paid to the curation of the experimental data. Subsequently, the Balanced Subsets method (BSM) was used to split each dataset into training, validation and test sets. Models were established by using 1819 conformation–independent molecular descriptors which were analyzed by the replacement method (RM) variable subset selection in order to obtain the optimal models. A four–descriptor model was obtained for the DB–225MS stationary phase while a three–parametric model was proposed for both the HP5–MS and HP–1 columns. Models were validated by means of the leave–one–out and leave–many–out cross–validation procedures, as well as other validation criteria. Moreover, in order to accomplish the principles proposed by the Organization for Economic Co–operation and Development (OECD), the model’s predictive ability was measured by predicting retention indices of the external test set. The applicability domain was properly defined and the interpretation of each of the molecular descriptors used in this study was provided.Fil: Rojas Villa, Cristian Xavier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Duchowicz, Pablo Román. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Tripaldi, P.. Universidad de Azuay; EcuadorFil: Pis Diez, Reinaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentin
Universal geometric entanglement close to quantum phase transitions
Under successive Renormalization Group transformations applied to a quantum
state of finite correlation length , there is typically a
loss of entanglement after each iteration. How good it is then to replace
by a product state at every step of the process? In this paper we
give a quantitative answer to this question by providing first analytical and
general proofs that, for translationally invariant quantum systems in one
spatial dimension, the global geometric entanglement per region of size diverges with the correlation length as
close to a quantum critical point with central charge , where is
a cut-off at short distances. Moreover, the situation at criticality is also
discussed and an upper bound on the critical global geometric entanglement is
provided in terms of a logarithmic function of .Comment: 4 pages, 3 figure
¿Existe alguna relación entre la capacidad de movimiento funcional y el estado ponderal? Un estudio en escolares españoles
Indexación: Scopus.Background: to examine relations between functional movement patterns and weight status in Spanish primary school children and to determine the differences between sexes. Methods: three hundred and thirty-three, 6-13 years old children (164 boys and 169 girls), participated in this study. The main outcome measures were the body mass index (BMI) and the Functional Movement Screen™ (FMS). Children were classified as normal weight (NW), overweight (OV) or obese (OB) according to international cut-offs. Results: total FMS score was negatively correlated with BMI (p < 0.001). FMS score was different between children from NW, OV and OB groups (p = 0.001), lower with the increased BMI (p < 0.001 between all groups). Significant differences (p < 0.05) between NW, OV and OB were found in deep squat, hurdle step, in-line lunge, shoulder mobility, straight leg-raise and push-up tests. As for the sex differences, girls obtained higher scores (p < 0.05) in in-line lunge, shoulder mobility and straight leg-raise, whereas boys did it in push-up (p = 0.044) test. Conclusions: these results confirm that total FMS score significantly and inversely correlates with BMI in a group of 333 school-age children. As for the sex differences, girls outperform boys in movements requiring flexibility and balance, whilst boys outperform girls in tests where muscular strength is required. © 2018 SENPE and Arán Ediciones S.L.Introducción: examinar la relación entre los patrones de movimiento funcional y el estado ponderal en escolares españoles, determinando
también la infl uencia de la variable sexo.
Métodos: trescientos treinta y tres niños de 6-13 años de edad (164 niños y 169 niñas), participaron voluntariamente en este estudio. Las
variables objeto de estudio fueron el índice de masa corporal (IMC) y la batería de test Functional Movement ScreenTM (FMS). Los niños fueron
clasifi cados como normopeso (NW), sobrepeso (OV) y obesos (OB) de acuerdo con los puntos de corte internacionales.
Resultados: la puntuación total en el FMS correlacionó de forma negativa y signifi cativa con el IMC (p < 0,001). La puntuación en FMS fue
diferente entre las categorías de peso (p = 0,001), hallando un peor rendimiento en FMS conforme aumenta el IMC (p < 0,001 entre todos los
grupos). Se hallaron diferencias signifi cativas (p < 0,05) entre NW, OV y OB en los test de deep squat, hurdle step, in-line lunge, shoulder mobility,
straight leg-raise and push-up. En cuanto a las diferencias por sexo, las chicas obtuvieron puntuaciones más altas en FMS (p < 0,05) en los test
in-line lunge, shoulder mobility and straight leg-raise; mientras los chicos obtuvieron puntuaciones superiores en el test de push-up (p = 0,044).
Conclusiones: los resultados confi rman que la puntuación total en el FMS correlaciona signifi cativa y negativamente con el IMC en este grupo
de 333 escolares. En cuanto a la infl uencia del sexo, las chicas obtuvieron mayor puntuación que los chicos en los test que requerían fl exibilidad
y equilibrio, mientras los chicos fueron superiores en los test en los que predominaba la fuerza muscular.https://www.nutricionhospitalaria.org/index.php/articles/01670/show#
Multi-Point Propagators in Cosmological Gravitational Instability
We introduce the concept of multi-point propagators between linear cosmic
fields and their nonlinear counterparts in the context of cosmological
perturbation theory. Such functions express how a non-linearly evolved Fourier
mode depends on the full ensemble of modes in the initial density field. We
identify and resum the dominant diagrams in the large- limit, showing
explicitly that multi-point propagators decay into the nonlinear regime at the
same rate as the two-point propagator. These analytic results generalize the
large- limit behavior of the two-point propagator to arbitrary order. We
measure the three-point propagator as a function of triangle shape in numerical
simulations and confirm the results of our high- resummation. We show that
any point spectrum can be reconstructed from multi-point propagators, which
leads to a physical connection between nonlinear corrections to the power
spectrum at small scales and higher-order correlations at large scales. As a
first application of these results, we calculate the reduced bispectrum at
one-loop in renormalized perturbation theory and show that we can predict the
decrease in its dependence on triangle shape at redshift zero, when standard
perturbation theory is least successful.Comment: 21 pages, 14 figures. Minor changes to match published version (Fig
11 changed, added reference
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