Collapsing dynamics of relativistic fluid in modified gravity admitting a conformal Killing vector

The collapsing dynamics of relativistic fluid are explored in $f(R)$ gravity in a detailed systematic manner for the non-static spherically symmetric spacetime satisfying the equation of the conformal Killing vector. With quasi-homologous condition and diminishing complexity factor condition, exact solutions for dissipative as well as for non-dissipative systems are found and the astrophysical applications of these exact solutions are discussed. Furthermore, it is demonstrated that $f(R)=R$, which is the extensive restriction of $f(R)$ gravity, prior solutions of the collapsing fluid in general relativity, can be retrieved.Comment: 26 pages, version accepted for publication in the European Physical Journal

A full body musculoskeletal model based on flexible multibody simulation approach utilised in bone strain analysis during human locomotion

Load-induced strains applied to bone can stimulate its development and adaptation. In order to quantify the incident strains within the skeleton, in vivo implementation of strain gauges on the surfaces of bone is typically used. However, in vivo strain measurements require invasive methodology that is challenging and limited to certain regions of superficial bones only such as the anterior surface of the tibia. Based on our previous study [Al Nazer et al. (2008) J Biomech. 41:1036&ndash;1043], an alternative numerical approach to analyse in vivo strains based on the flexible multibody simulation approach was proposed. The purpose of this study was to extend the idea of using the flexible multibody approach in the analysis of bone strains during physical activity through integrating the magnetic resonance imaging (MRI) technique within the framework. In order to investigate the reliability and validity of the proposed approach, a three-dimensional full body musculoskeletal model with a flexible tibia was used as a demonstration example. The model was used in a forward dynamics simulation in order to predict the tibial strains during walking on a level exercise. The flexible tibial model was developed using the actual geometry of human tibia, which was obtained from three-dimensional reconstruction of MRI. Motion capture data obtained from walking at constant velocity were used to drive the model during the inverse dynamics simulation in order to teach the muscles to reproduce the motion in the forward dynamics simulation. Based on the agreement between the literature-based in vivo strain measurements and the simulated strain results, it can be concluded that the flexible multibody approach enables reasonable predictions of bone strain in response to dynamic loading. The information obtained from the present approach can be useful in clinical applications including devising exercises to prevent bone fragility or to accelerate fracture healing.<br /

Hubble expansion variance and the cosmic rest frame

Average homogeneity is only reached on scales greater than 70{100h1Mpc yet standard peculiar velocity approaches assume an most Euclidean geometry below this scale. Furthermore, the Friedmann equation is applied in the nonlinear regime, although this has no motivation in the fundamental principles of general relativity. We investigate the variance of the Hubble expansion in a manner which makes no prior geometrical assumptions, other than the existence of a suitably averaged linear Hubble law. We use the COMPOSITE data set of 4534 galaxies [Watkins, Feldman and Hudson (2009)]

Restricción del crecimiento intrauterino como factor de riesgo para malformaciones congénitas

Indexación: ScieloAntecedentes: La restricción del crecimiento intrauterino (RCIU) se estima que está presente en el 5% de los nacimientos y es la manifestación de procesos aberrantes que impiden el desarrollo normal del feto. Objetivos: Estimar la frecuencia de esta patología en la maternidad del Hospital Clínico de la Universidad de Chile. Obtener la tasa prevalencia al nacimiento de malformaciones congénitas (MFC) y comparar la frecuencia en recién nacidos pequeños (PEG) con los adecuados (AEG) y grandes (GEG) para la edad gestacional. Método: Se estudian todos los nacimientos, vivos y mortinatos, ocurridos entre enero de 1997 a diciembre de 2008, contenidos en la base de datos del ECLAMC (Estudio Colaborativo Latino Americano de Malformaciones Congénitas) desde 1969 a la fecha. Se excluyen los recién nacidos con malformaciones como hidrocefalia, anencefalia e hidrops, que por sus características dificultan la posibilidad de clasificación en PEG, AEG o GEG. Resultados: 10,1% de los nacimientos del período eran PEG. Entre los nacidos vivos 10% fueron PEG, mientras que 33,5% de los mortinatos eran PEG (p<0,05). Eran malformados el 12,9% de los PEG, 8,5% de los AEG y 9,3% de los GEG (p<0,05). La tasa global de malformaciones fue de 9,5%; en NV el 9,4% y en mortinatos el 33%. Conclusión: El RCIU es un factor que aumenta el riesgo de mortalidad fetal tardía y de presentar malformaciones congénitas.Background: Fetal growth restriction (FGR) is the result of anomalies that prevent the normal development of the fetus, it is present in about the 5% of births. Objectives: To estímate the frequency of FGR in the Clini-cal Hospital of the University of Chile. To estímate the congenital malformation prevalence rate at birth and compare it among small (SGE), adequate (AGE) and large (LGE) newborns according their gestational age. Methods: All live births and stillbirths included in the ECLAMC (Estudio Colaborativo Latino Americano de Malformaciones Congénitas) registered from January 1997 and December 2008 were considered. Newborns with congenital malformations that modified per se the size of the child, like hydrocephaly anencephaly and hydrops were excluded. Results: 10.1% of newborns were SGE. Among live births 10% were SGE instead of the 33.5% found in stillbirths (p<0.05). Congenital malformation rate at birth was 12.9% in SGE, 8.5% in AGE and 9.3% in LGE newborns (p<0.05). The global congenital malformation prevalence rate at birth was 9.5%; 9.4% in live newborns and 33% in stillbirth. Conclusión: The FGR increase the risk of late fetal mortality and congenital anomalies.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-75262009000600008&nrm=is

Vigilancia epidemiológica del síndrome de Down en Chile, 1972 a 2005

International audienceRoutledge, 2014, 422

Application of an Improved Neural Network Using Cuckoo Search Algorithm in Short-Term Electricity Price Forecasting under Competitive Power Markets

Accurate and effective electricity price forecasting is critical to market participants in order to make an appropriate risk management in competitive electricity markets. Market participants rely on price forecasts to decide on their bidding strategies, allocate assets and plan facility investments. However, due to its time variant behavior and non-linear and non-stationary nature, electricity price is a complex signal. This paper presents a model for short-term price forecasting according to similar days and historical price data. The main idea of this article is to present an intelligent model to forecast market clearing price using a multilayer perceptron neural network, based on structural and weights optimization. Compared to conventional neural networks, this hybrid model has high accuracy and is capable of converging to optimal minimum. The results of this forecasting method for Market Clearing Price (MCP) of Iranian and Nord Pool Electricity Markets, as well as Locational Marginal Price (LMP) forecasting in PJM electricity market, verify the effectiveness of the proposed approach in short-term price forecasting

Electrophysiological Characterization of Human Atria: The understated Role of Temperature

Ambient temperature has a profound influence on cellular electrophysiology through direct control over the gating mechanisms of different ion channels. In the heart, low temperature is known to favor prolongation of the action potential. However, not much is known about the influence of temperature on other important characterization parameters such as the resting membrane potential (RMP), excitability, morphology and characteristics of the action potential (AP), restitution properties, conduction velocity (CV) of signal propagation, etc. Here we present the first, detailed, systematic in silico study of the electrophysiological characterization of cardiomyocytes from different regions of the normal human atria, based on the effects of ambient temperature (5−50°C). We observe that RMP decreases with increasing temperature. At ~ 48°C, the cells lose their excitability. Our studies show that different parts of the atria react differently to the same changes in temperature. In tissue simulations a drop in temperature correlated positively with a decrease in CV, but the decrease was region-dependent, as expected. In this article we show how this heterogeneous response can provide an explanation for the development of a proarrhythmic substrate during mild hypothermia. We use the above concept to propose a treatment strategy for atrial fibrillation that involves severe hypothermia in specific regions of the heart for a duration of only ~ 200 ms. © Copyright © 2021 Majumder, Mohamed Nazer, Panfilov, Bodenschatz and Wang.This work was supported by the Max Planck Society and the German Center for Cardiovascular Research. Research at Sechenov University was financed by the Ministry of Science and Higher Education of the Russian Federation within the framework of state support for the creation and development of World-Class Research Centers Digital biodesign and personalized healthcare No. 075-15-2020-926