694 research outputs found
Computational limit analysis for anchors and retaining walls
The computation of the bearing capacity of engineering structures commonly relays on results obtained for simple academic examples. Recent developments in computational limit analysis have allowed engineers to compute bounds of the bearing capacity of arbitrary geometries. We here extend these formulations to problems with practical interest such as retaining walls, anchors, or excavations with particular interface conditions. These situations require the special treatment of the contact conditions between different materials, or the modelling of joints and anchors. We demonstrate the potential of the resulting tool with some practical examples
Numerical modelling of multicellular dynamics
En este trabajo se desarrollar un modelo computacional que permite simular y predecir las deformaciones sucesivas que tienen lugar durante fases de la embriogénesis que han sido biológicamente bien detalladas. Las simulaciones resultantes tienen como objetivo reproducir la sincronización en la dinámica celular, las fuerzas que la dirigen, y la regulación genética y química del desarrollo embrionario.
Los modelos numéricos tradicionales, basados mayoritariamente en elementos finitos, muestran dificultades en capturar tanto los cambios de geometría como las propiedades no lineales del material. El modelo propuesto hereda la partición física en células biológicas, y está consecuentemente basado en un medio discontinuo, en vez de un medio continuo. El modelo resuelve el equilibrio mecánico de las fuerzas intra- e inter-celulares, y para ello, combina estrategias de modelos centrados y de vértices, que a su vez son ampliados con ecuaciones de difusión/reacción que simulan y controlan la respuesta mecánica de la célula.This work aims to develop a computational model that can simulate and predict those successive deformations that biologically well understood cell shape changes take place in embryogenesis. The resulting simulations aim to reproduce the synchronised cell dynamics, the mechanical forces that drive them, and also the chemical and genetic regulation of embryo development.
Traditional numerical models, which are mainly based on finite element techniques, are unable to capture the geometrical changes and the non-linear material properties. The proposed model inherits the physical partition in biological cells, and is thus based in a discontinuum rather than a continuum medium. The model aims to solve the mechanical equilibrium of intra- and inter-cellular forces, and in order to do so, it combines cell-centred and vertex strategies, which are in turn enhanced with diffusion-reaction equations that simulate and control the cell mechanical response.Peer Reviewe
Estudio de viabilidad para la emisión de títulos de deuda para financiar la ampliación del colegio balandra cruz del sur
empresas. Nuestra empresa a analizar, PREDUCA S.A, se ha desenvuelto en el sector educativo clase alta, manteniendo un prestigio por 17 años, lo cual la coloca como una de las mejores dentro de su estrato social. Su objetivo de reestructuración de pasivos y expansión futura, nos llevaron a establecer pautas para la utilización de nuevas herramientas de financiamiento.
La emisión de obligaciones es una herramienta, conocida y utilizada en varios países incluidos el nuestro, que ha dado paso a un mayor desarrollo en el mercado de capitales ya que se muestra como una opción rentable al momento de invertir.
Los análisis de los estados financieros de nuestra empresa en mención fueron factores cruciales para poder determinar la factibilidad de una emisión, además de una estrategia de introducción de este tipo de empresas en el mercado de valores, ya que de incursionar PREDUCA S.A. en este mercado sería la primera en su clase y sector. Las oportunidades y amenazas que una decisión como esta conlleva y los beneficios futuros asociados son tratados en nuestro estudio, a fin de dar al lector una visión del entorno de la empresa y proporcionar una guía de procedimientos a seguir en caso de realizarse una emisión de obligaciones. Todo ello asociado con la experiencia tanto al interior de nuestro país, la realidad que se ha vivido en los últimos años en nuestro mercado de obligaciones conjuntamente con lo sucedido en países latinoamericanos, nos muestra el escenario en que se desenvolvería PREDUCA S.A. al momento de emitir una obligación
Halo based reconstruction of the cosmic mass density field
We present the implementation of a halo based method for the reconstruction
of the cosmic mass density field. The method employs the mass density
distribution of dark matter haloes and its environments computed from
cosmological N-body simulations and convolves it with a halo catalog to
reconstruct the dark matter density field determined by the distribution of
haloes. We applied the method to the group catalog of Yang etal (2007) built
from the SDSS Data Release 4. As result we obtain reconstructions of the cosmic
mass density field that are independent on any explicit assumption of bias. We
describe in detail the implementation of the method, present a detailed
characterization of the reconstructed density field (mean mass density
distribution, correlation function and counts in cells) and the results of the
classification of large scale environments (filaments, voids, peaks and sheets)
in our reconstruction. Applications of the method include morphological studies
of the galaxy population on large scales and the realization of constrained
simulations.Comment: Accepted for publication in MNRA
Characterizing SL2S galaxy groups using the Einstein radius
We analyzed the Einstein radius, , in our sample of SL2S galaxy
groups, and compared it with (the distance from the arcs to the center of
the lens), using three different approaches: 1.- the velocity dispersion
obtained from weak lensing assuming a Singular Isothermal Sphere profile
(), 2.- a strong lensing analytical method ()
combined with a velocity dispersion-concentration relation derived from
numerical simulations designed to mimic our group sample, 3.- strong lensing
modeling () of eleven groups (with four new models presented in
this work) using HST and CFHT images. Finally, was analyzed as a function
of redshift to investigate possible correlations with L, N, and the
richness-to-luminosity ratio (N/L). We found a correlation between
and , but with large scatter. We estimate = (2.2 0.9)
+ (0.7 0.2), = (0.4 1.5) + (1.1
0.4), and = (0.4 1.5) + (0.9 0.3) for
each method respectively. We found a weak evidence of anti-correlation between
and , with Log = (0.580.06) - (0.040.1), suggesting
a possible evolution of the Einstein radius with , as reported previously by
other authors. Our results also show that is correlated with L and N
(more luminous and richer groups have greater ), and a possible
correlation between and the N/L ratio. Our analysis indicates that
is correlated with in our sample, making useful to
characterize properties like L and N (and possible N/L) in galaxy groups.
Additionally, we present evidence suggesting that the Einstein radius evolves
with .Comment: Accepted for publication in Astronomy & Astrophysics. Typos correcte
Assessing the impact of COVID-19 on liver cancer management (CERO-19)
Background & Aims: The coronavirus disease 2019 (COVID-19) pandemic has posed unprecedented challenges to healthcare
systems and it may have heavily impacted patients with liver cancer (LC). Herein, we evaluated whether the schedule of LC
screening or procedures has been interrupted or delayed because of the COVID-19 pandemic.
Methods: An international survey evaluated the impact of the COVID-19 pandemic on clinical practice and clinical trials from
March 2020 to June 2020, as the first phase of a multicentre, international, and observational project. The focus was on
patients with hepatocellular carcinoma or intrahepatic cholangiocarcinoma, cared for around the world during the first
COVID-19 pandemic wave.
Results: Ninety-one centres expressed interest to participate and 76 were included in the analysis, from Europe, South America,
North America, Asia, and Africa (73.7%,17.1%, 5.3%, 2.6%, and 1.3% per continent, respectively). Eighty-seven percent of the centres
modified their clinical practice: 40.8% the diagnostic procedures, 80.9% the screening programme, 50% cancelled curative and/or
palliative treatments for LC, and 41.7% modified the liver transplantation programme. Forty-five out of 69 (65.2%) centres in
which clinical trials were running modified their treatments in that setting, but 58.1% were able to recruit new patients. The
phone call service was modified in 51.4% of centres which had this service before the COVID-19 pandemic (n = 19/37).
Conclusions: The first wave of the COVID-19 pandemic had a tremendous impact on the routine care of patients with liver
cancer. Modifications in screening, diagnostic, and treatment algorithms may have significantly impaired the outcome of
patients. Ongoing data collection and future analyses will report the benefits and disadvantages of the strategies imple mented, aiding future decision-making
Electronic, vibrational, and thermodynamic properties of ZnS (zincblende and rocksalt structure)
We have measured the specific heat of zincblende ZnS for several isotopic
compositions and over a broad temperature range (3 to 1100 K). We have compared
these results with calculations based on ab initio electronic band structures,
performed using both LDA and GGA exchange- correlation functionals. We have
compared the lattice dynamics obtained in this manner with experimental data
and have calculated the one-phonon and two-phonon densities of states. We have
also calculated mode Grueneisen parameters at a number of high symmetry points
of the Brillouin zone. The electronic part of our calculations has been used to
investigate the effect of the 3d core electrons of zinc on the spin-orbit
splitting of the top valence bands. The effect of these core electrons on the
band structure of the rock salt modification of ZnS is also discussed.Comment: 33pages, 16 Figures, submitted to Phys. Rev.
M.A.B. Revestimientos vítreos con propiedades bactericidas y fungicidas
This report describes the mosaic M.A.B. (bactericide and fungicide) produced by Togama S.A. belonging to the group Fluidra
S.A., which has been awarded with the Silver Alfa Award by the Spanish Society of Ceramics and Glass at the International
Fair Cevisama 2012. This award recognizes the R & D efforts developed by Togama, SA, already started with participation
in the Alpha Awards 2009 and 201
First-principles study of electronic, vibrational, elastic, and magnetic properties of FeF 2 as a function of pressure
We report systematic ab initio calculations of the electronic band structure, phonon dispersion relation, and the structural characterization of FeF 2 in the rutile (P 4 2 /mnm) structure as well as in several high-pressure phases by means of the generalized gradient approximation (GGA) + U approximation. Using the phonon dispersion relations, we calculated the Gibbs free energy and evaluated the phase transitions at 300 K, at which most experimental measurements are performed. Calculated Raman and infrared vibrational modes, lattice parameters, and electronic structure for all considered crystalline structures are compared with available experimental data. Our calculations show that at 5.33 GPa, the FeF 2 undergoes a second-order proper ferroelastic phase transition, rutile → CaCl 2 -type structure. This result is supported by the softening of the elastic shear module C s in the rutile phase, the softening (hardening) of the B 1g (A g ) Raman active mode in the rutile (CaCl 2 -type) structure near the transition pressure, and the decrease of the square of the spontaneous strain e ss from the CaCl 2 -type structure. This demonstrates that the rutile → CaCl 2 -type phase transition is driven by the coupling between the Raman active B 1g mode and shear modulus C s . At 8.22 GPa, the CaCl 2 -type structure undergoes a first-order phase transition to the P bca phase, a distorted fcc P a3 phase with a volume reduction of V ≈ 7%, as reported in experiments. Upon further increase of the pressure, the P bca phase transforms to a F mmm phase othorhombic center-type structure at ∼20.38 GPa, with V ≈ 2.5%. Finally, at 25.05 GPa, there is a phase transition to the orthorhombic cotunnite structure (P nma space group), with V ≈ 5.8%, which is stable up to 45 GPa, the largest considered pressure. The coordination number for the Fe ion in each phase is 6, 6, 6, 8, and 9 for rutile, CaCl 2 -type, P bca, F mmm, and cotunnite structures, respectively. The evolution of the band gap, phonon frequencies, and magnetic moment of Fe ion as a function of the applied pressure is reported for all studied phases. The exchange constants J 1 , J 2 , and J 3 , calculated for rutile and the lowest Gibbs free-energy high-pressure phases, are reported
Radio continuum and near-infrared study of the MGRO J2019+37 region
(abridged) MGRO J2019+37 is an unidentified extended source of VHE gamma-rays
originally reported by the Milagro Collaboration as the brightest TeV source in
the Cygnus region. Its extended emission could be powered by either a single or
several sources. The GeV pulsar AGL J2020.5+3653, discovered by AGILE and
associated with PSR J2021+3651, could contribute to the emission from MGRO
J2019+37, although extrapolation of the GeV spectrum does not explain the
detected multi-TeV flux. Our aim is to identify radio and NIR sources in the
field of the extended TeV source MGRO J2019+37, and study potential
counterparts that could contribute to its emission. We surveyed a region of
about 6 square degrees with the Giant Metrewave Radio Telescope (GMRT) at the
frequency 610 MHz. We also observed the central square degree of this survey in
the NIR Ks-band using the 3.5 m telescope in Calar Alto. Archival X-ray
observations of some specific fields are included. VLBI observations of an
interesting radio source were performed. We explored possible scenarios to
produce the multi-TeV emission from MGRO J2019+37 and studied which of the
sources could be the main particle accelerator. We present a catalogue of 362
radio sources detected with the GMRT in the field of MGRO J2019+37, and the
results of a cross-correlation of this catalog with one obtained at NIR
wavelengths, as well as with available X-ray observations of the region. Some
peculiar sources inside the ~1 degree uncertainty region of the TeV emission
from MGRO J2019+37 are discussed in detail, including the pulsar PSR J2021+3651
and its pulsar wind nebula PWN G75.2+0.1, two new radio-jet sources, the HII
region Sh 2-104 containing two star clusters, and the radio source NVSS
J202032+363158.Comment: 10 pages, 6 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
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