A New Algorithm for the Evaluation of the Elastic Forces in the Absolute Nodal Coordinate Formulation

The use of the Absolute Nodal Coordinate Formulation (ANCF) to model flexible multibody systems leads to a system of equations in which the mass matrix is constant. Among other advantages of the ANCF, as the simplicity of the formulation of joint constraint, the constancy of the mass matrix is specially useful since it implies that the mass matrix is calculated once before the analysis and stored as a invariant quantity. On the other hand, the evaluation of the elastic forces has been considered as a difficult task since they result in large nonlinear functions. Both linear and nonlinear formulations based on either Continuum Mechanics or Timoshenko/Euler-Bernoulli approaches have been supposed to lead to the same level of complexity of the elastic force function. The evaluation of the elastic forces when using a nonlinear Continuum Mechanics approach requires, as presented in the literature, the integration over the volume of the element. However, it can be shown that this integration can be avoided for every evaluation since there is a closed form of the elastic force function that can be obtained before the simulation. Finite elements based on ANCF have such a large number of nodal coordinate (24 and 48 for three-dimensional beams and plates, respectively) that the search for a closed form of the elastic force function becomes difficult and costly. This paper presents a set of constant matrices that are integrated in advance (before simulation) and allows the evaluation of the elastic forces without the integration over the volume of the element suggested in the literature. In addition, the amount of data that has to be stored in order to evaluate the function is reduced. These constant matrices together with the mass matrix complete the set of invariants of the ANCF that allows an acceleration of simulations. Numerical simulations comparing CPU time and number of arithmetic operations carried out when these invariant matrices are used with those carried out when they are not used, support the convenience of their use.Ministerio de Ciencia y Tecnología DPI2000-056

Respuestas de alimentación de Scolytus scolytus a extractos del floema de ramillas de olmo

Feeding responses by Scolytus scolytus were tested using elm twig bark extracts in a laboratory bioassay. One to 4- years-old elm twigs or small branches were sampled in spring and their bark extracted separately with methanol and with a mixture of petroleum ether and diethyl ether (1:1) as solvents. Bark extracts were tested in a two choice feeding bioassay consisting of two polyurethane discs placed in a 10 cm diameter Petri dish. Extracts were applied onto the discs and the amount of disc eaten by ten freshly emerged S. scolytus adults was recorded after 24 hours. Ten U. minor, two U. laevis, six U. glabra, three Dutch hybrids (European x Asiatic) and one U. pumila trees were tested in several comparisons. Discs with extracts from both U. laevis trees were significantly less eaten than those from U. pumila or from U. minor trees in two choice tests. Similarly, extracts from all U. glabra trees received less feeding than those from U. minor. On the contrary, S. scolytus showed no difference in feeding between U. pumila and U. minor extracts, and similarly for Dutch hybrids in comparison with two U. minor clones. Again, beetles preferred to feed on Dutch hybrid extracts better than in those from U. laevis. Significant intraspecific differences in feeding were obtained in U. minor. One of the U. minor clones resulted less chosen when compared to other four trees. Extracts from a dying U. minor tree received more feeding than those from a healthy tree. Comparisons were also made between bark extracts from 2-to 4-year-old vs. current-year twigs within the same trees. In one of the four U. minor tested, a significant preference for the older twig extracts was recorded.Se estudió la respuesta de alimentación de S. scolytus a extractos del floema de ramillas de olmo en bioensayos de laboratorio. Se muestrearon en primavera ramillas de olmo de uno a cuatro años de edad y su floema fue extraído independientemente con metanol o con una mezcla de eter de petróleo y eter dietílico (1:1). Los extractos del floema se evaluaron en un bioensayo de doble elección consistente en dos discos de poliuretano dispuestos en una placa Petri de 10 cm de diámetro. Se aplicaron los extractos a los discos y se midió la superficie de disco comida por diez adultos recién emergidos de S. scolytus durante 24 h. Se ensayaron diez U. minor, dos U. laevis, seis U. glabra, tres híbridos holandeses (europeo x asiático) y un U. pumila en diversas comparaciones. Los discos con extractos de ambos U. laevis fueron significativamente menos comidos que aquéllos con los de U. pumila o de U. minor. Igualmente, los extractos de todos los U. glabra recibieron menor alimentación que aquéllos de U. minor. Por el contrario, S. scolytus no mostró preferencias entre los extractos de U. minor y de U. pumila, e igualmente, entre los de U. minor y los de híbridos holandeses. Nuevamente, los escolítidos prefirieron alimentarse menos de los extractos de U. laevis que de los híbridos holandeses. Se encontraron diferencias intraespecíficas significativas en U. minor. Uno de los clones de U. minor resultó menos preferido cuando se le comparó con otros cuatro árboles. Los extractos de un U. minor moribundo recibieron mayor alimentación que los de un árbol sano. Se realizaron comparaciones entre los extractos del floema de ramillas de 2 a 4 años de edad y de ramillas del año en curso de un mismo árbol. En uno de cuatro U. minor ensayados se observó una preferencia significativa por los extractos de las ramillas más viejas

Experimental estimation of the residual fatigue life of in-service wind turbine bolts

This study presents an experimental methodology aimed at estimating the residual fatigue life of in-service wind turbine bolts. The main objective is to assess the residual life of the bolts to plan their replacement and to avoid unexpected breakages of wind turbine blade connections. To develop the methodology, M16 bolts of quality 10.9 with controlled predamage were used, simulating in-service operating conditions. The fatigue tests were carried out taking care to place the nut at the point on the bolt that produces the highest damage at the same point where the predamage was performed. In addition, the influence of a possible angular positioning error on the residual fatigue life has been investigated. The residual fatigue life is estimated from the difference in fatigue life of new bolt tests and the fatigue life of predamaged bolt tests, simulating service conditions. Special care has been taken to guarantee that the most damaged zone of the bolt in service is also in the position that produces the highest damage during tests. An experimental procedure for determining the fatigue life of a new bolt from tests conducted on a bolt under the same operating conditions was developed. The developed methodology has been applied to M20 bolts belonging to real turbines in service

Componentes de la corteza del olmo y su posible influencia en la alimentación de los escolítidos

In order to better understand the chemical factors involved in the host feeding selectivity by Scolytus, components were extracted from elm bark and studied. Sampled trees were located in an elm stand that survived the Dutch twig elm disease pandemia, and from elm clones from throughout the Iberian Peninsula. The main samples studied were from Ulmus minor, and the other samples from U. pumila, U. laevis and several hybrids. The main compounds in the extracts obtained from current-year twigs were aliphatic hydrocarbons (particularly heptacosane and nonacosane) and from 2- to 4-year-old stems were triterpenes. Three of the triterpenes were identified for the first time in Ulmus (lupenol, alnulin, and ilexol) and two in Ulmaceae (moretenol and betulin). Differences occurred in the compounds isolated from U. minor from the two locations, and between species.Se analizaron los componentes de la corteza de ramillas de olmos, a fin de determinar los factores químicos involucrados en la selección, por parte de los escolítidos del olmo (Scolytus), de árboles para su alimentación. Las muestras fueron recogidas en árboles de una olmeda que ha sobrevivido a la pandemia de grafiosis y de ejemplares de distintas procedencias de la península Ibérica en un banco clonal. La principal especie estudiada fue Ulmus minor. Se tomaron además muestras de U. pumila, U. laevis y diversos híbridos. Los compuestos más abundantes en los extractos obtenidos de ramillas del año en curso fueron hidrocarburos alifáticos (principalmente heptacosano y nonacosano) y en las ramillas de 2º a 4º año triterpenos pentacíclicos. Tres de los triterpenos (lupenol, alnulina e ilexol) fueron identificados por primera vez en Ulmus y dos (moretenol y betulina) en Ulmaceae. Se observaron diferencias en los compuestos detectados en U. minor de las dos localizaciones así como entre especies

Diseño y simulación de un actuador de rigidez variable

XIX Congreso Nacional de Ingeniería Mecánica (CNIM 2012), Castellón, 14-16 de noviembre de 2012Los actuadores de rigidez variable se han desarrollado como una alternativa a los actuadores convencionales en diversas aplicaciones, como son entre otras los robots de servicio y los robots caminantes. El diseño mecánico de estos actuadores debe dar solución a nuevas necesidades que no eran tenidas en consideración en los actuadores rígidos, como la reducción del daño en caso de impacto o el ajuste de la frecuencia natural del sistema. Han sido muy diversas las soluciones propuestas hasta el momento, caracterizadas por el tipo de mecanismo implementado para variar la rigidez y posición de la articulación. En este trabajo se presenta un nuevo diseño de actuador basado en transmisión por cables, en el que un primer motor controla la posición de equilibrio del eslabón y un segundo motor se encarga de variar la rigidez de la articulación. Además, se ha simulado una situación de impacto hombre-robot para estudiar su contribución en la reducción del daño en hombre y robot.This work has been supported by the CAM Project S2009/DPI-1559/ROBOCITY2030 II, developed by the research team RoboticsLab at the University Carlos III of Madrid

Correlaciones fenotípicas, genéticas y ambientales en cucurbita moschata duch. ex poir

El estudio estimó las correlaciones fenotípicas, genéticas y ambientales entre doce caracteres agronómicos en dos dialélicos de zapallo (uno entre cinco variedades y otro entre cinco líneas S1, originadas de las anteriores). Se usó un diseño en bloques completos al azar con 15 tratamientos (5 progenitores + 10 cruzamientos F1) para cada dialélico y cinco repeticiones. Los resultados señalaron mayor estimación de las correlaciones (en magnitud y significancia estadística) a favor del dialélico de líneas S1. Las correlaciones genéticas fueron superiores a las fenotípicas y las ambientales. La producción por planta (PFP) presentó las correlaciones parciales fenotípicas y genéticas más altas con el peso por fruto (PPF) y el número de frutos por planta (NFP) (rPF y rPG and gt; 0.80). El PPF y NFP pueden usarse como criterios de selección para la obtención de cultivares de altos rendimientos en C. moschata. ABSTRACT Phenotypic, genotypic and environmental correlations in Cucurbita moschata Duch. Ex Poir. The study evaluated phenotypic, genotypic and environmental correlations among 12 agronomy characters, in two set diallelic from five parents each one. The first set from five open pollinated varieties and the second one from five self-pollinated lines S1, obtained from the previous varieties. The two experiments were in completely randomized blocks with five replications. A higher estimation of correlation (in magnitude and statistical significance) was observed in favor of the S1 lines diallelic. The genetic correlations were higher than the phenotypic and environmental correlations. The plant yield (PFP) showed the highest partial phenotypic and genetic correlations with the fruit weight (PPF) and fruits per plant (NFP) (rPF and rPG and gt; 0.80). It is suggested to use the PPF and NFP as selection criteria for breeding of C. moschata for development of high yield cultivars. Key words: Calabaza (cucurbita), genetic correlation, agronomic characteristics

Neuropathological findings in fatal COVID-19 and their associated neurological clinical manifestations

9 p.Severe cases of Coronavirus Disease 2019 (COVID-19) can present with multiple neurological symptoms. The available neuropathological studies have described different lesions; the most frequent was the presence of neuroinflammation and vascular-related lesions. The objective of this study was to report the neuropathological studies performed in a medical institution, with abundant long intensive care unit stays, and their associated clinical manifestations. This is a retrospective monocentric case series study based on the neuropathological reports of 13 autopsies with a wide range of illness duration (13-108 days). A neuroinflammatory score was calculated based on the quantification of CD8- and CD68-positive cells in representative areas of the central nervous system. This score was correlated afterwards with illness duration and parameters related to systemic inflammation. Widespread microglial and cytotoxic T-cell activation was found in all patients. There was no correlation between the neuroinflammatory score and the duration of the illness; nor with parameters of systemic inflammation such as the peak of IL-6 or the HScore (a parameter of systemic macrophage activation syndrome). Two patients had global hypoxic ischaemic damage and five patients had subacute infarcts. One patient had many more brain vascular microthrombi compared to the others and multiple subacute pituitary infarcts. SARS-CoV-2 RNA was not detected with qRT-PCR. The proportion of brain lesions in severe COVID-19 patients could be related to illness duration. In our series, with abundant long hospitalisation stays, neuroinflammation was present in all patients and was more prominent between day 34 and day 45 after onset of symptoms. Clinical correlation showed that two patients with the highest neuroinflammatory scores had severe encephalopathies that were not attributable to any other cause. The second most frequent lesions were related to vascular pathology.Instituto de Salud Carlos IIICIBERONCInstituto Ramón y Cajal de Investigación SanitariaMerck, Sharp & Dohme (MSD

Liver injury in non-alcoholic fatty liver disease is associated with urea cycle enzyme dysregulation

The main aim was to evaluate changes in urea cycle enzymes in NAFLD patients and in two preclinical animal models mimicking this entity. Seventeen liver specimens from NAFLD patients were included for immunohistochemistry and gene expression analyses. Three-hundred-and-eighty-two biopsy-proven NAFLD patients were genotyped for rs1047891, a functional variant located in carbamoyl phosphate synthetase-1 (CPS1) gene. Two preclinical models were employed to analyse CPS1 by immunohistochemistry, a choline deficient high-fat diet model (CDA-HFD) and a high fat diet LDLr knockout model (LDLr −/−). A significant downregulation in mRNA was observed in CPS1 and ornithine transcarbamylase (OTC1) in simple steatosis and NASH-fibrosis patients versus controls. Further, age, obesity (BMI > 30 kg/m2), diabetes mellitus and ALT werefound to be risk factors whereas A-allele from CPS1 was a protective factor from liver fibrosis. CPS1 hepatic expression was diminished in parallel with the increase of fibrosis, and its levels reverted up to normality after changing diet in CDA-HFD mice. In conclusion, liver fibrosis and steatosis were associated with a reduction in both gene and protein expression patterns of mitochondrial urea cycle enzymes. A-allele from a variant on CPS1 may protect from fibrosis development. CPS1 expression is restored in a preclinical model when the main trigger of the liver damage disappears

Stimulation of 3D osteogenesis by mesenchymal stem cells using a nanovibrational bioreactor

Bone grafts are one of the most commonly transplanted tissues. However, autologous grafts are in short supply, and can be associated with pain and donor-site morbidity. The creation of tissue-engineered bone grafts could help to fulfil clinical demand and provide a crucial resource for drug screening. Here, we show that vibrations of nanoscale amplitude provided by a newly developed bioreactor can differentiate a potential autologous cell source, mesenchymal stem cells (MSCs), into mineralized tissue in 3D. We demonstrate that nanoscale mechanotransduction can stimulate osteogenesis independently of other environmental factors, such as matrix rigidity. We show this by generating mineralized matrix from MSCs seeded in collagen gels with stiffness an order of magnitude below the stiffness of gels needed to induce bone formation in vitro. Our approach is scalable and can be compatible with 3D scaffolds