Fermionic origin of dark energy in the inflationary universe from unified spinor fields

In this work we explore the boundary conditions in the Einstein-Hilbert action, by considering a displacement from the Riemannian manifold to an extended one. The latter is characterized by including spinor fields into the quantum geometric description of a noncommutative spacetime. These fields are defined on the background spacetime, emerging from the expectation value of the quantum structure of spacetime generated by matrices that comply with a Clifford algebra. We demonstrate that spinor fields are candidate to describe all known interactions in physics, with gravitation included. In this framework we demonstrate that the cosmological constant Λ, is originated exclusively by massive fermion fields that would be the primordial components of dark energy, during the inflationary expansion of an universe that describes a de Sitter expansion.Fil: Arcodía, Marcos Ramiro Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; ArgentinaFil: Bellini, Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; Argentin

Particle-antiparticle duality from an extra timelike dimension

It is a well known fact that the usual complex structure on the real Clifford Algebra (CA) of Minkowski spacetime can be obtained by adding an extra time-like dimension, instead of the usual complexification of the algebra. In this article we explore the consequences of this approach and reinterpret known results in this new context. We observe that Dirac particles and antiparticles at rest can be interpreted as eigenstates of the generator of rotations in the plane formed by the two time-like coordinates and find an effective finite scale for the extra dimension when no EM fields are present (without postulating compactness). In the case of non-vanishing EM fields, we find a gauge condition to preserve such a scale.Fil: Arcodía, Marcos Ramiro Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; ArgentinaFil: Bellini, Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Físicas de Mar del Plata. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Físicas de Mar del Plata; Argentin

Heterogeneous Computational Model for Landform Attributes Representation on Multicore and Multi-GPU Systems

AbstractMathematical models are often used to simplify landform representation. Its importance is due to the possibility of describing phenomena by means of mathematical models from a data sample. High processing power is needed to represent large areas with a satisfactory level of details. In order to accelerate the solution of complex problems, it is necessary to combine two basic components in heterogeneous systems formed by a multicore with one or more GPUs. In this paper, we present a methodology to represent landform attributes on heterogeneous multicore and multi-GPU systems using high performance computing techniques for efficient solution of two-dimensional polynomial regression model that allow to address large problem instances

La GTPasa endosomal RhoB regula la recuperación de la barrera endotelial durante la inflamación

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 23-10-2015El endotelio forma la capa más interna de los vasos sanguíneos y separa el torrente circulatorio de los tejidos subyacentes. Su integridad es un requisito para el correcto desarrollo y terminación de la respuesta inflamatoria. Sin embargo, durante el transcurso de ésta, la función de la monocapa endotelial se ve comprometida debido a la acción combinada de las citoquinas pro-inflamatorias y las células inmunes. La inflamación es un componente de la mayoría de patologías de más prevalencia en nuestra sociedad y la disfunción endotelial es la base para el desarrollo de enfermedades inflamatorias crónicas. Con el objetivo de identificar nuevas proteínas claves en la respuesta inflamatoria humana, hemos descubierto que la GTPasa RhoB aumenta su expresión en respuesta a estímulos pro-inflamatorios y es expresada abundantemente en el endotelio de muestras de tejidos humanos de enfermedades inflamatorias crónicas. RhoB, junto con sus homólogas RhoA y RhoC, presentan funciones aditivas en el mantenimiento de la barrera endotelial, redundantes en la polimerización de actina en condiciones de reposo o inflamadas y no están implicadas en el aumento de permeabilidad a largo plazo inducido por TNF o en la trasnmigración del linfocito in vitro. Sin embargo, RhoB juega un papel específico y relevante en la restauración de la función de barrera tras la acción de agentes pro-coagulantes. RhoB favorece la disfunción endotelial al prevenir la expansión de la célula sobre el sustrato tras la contracción endotelial aguda. Durante la recuperación, detectamos un incremento en el tráfico de vesículas de RhoB hacia y desde protrusiones nacientes de la membrana plasmática y demostramos que RhoB controla el tráfico intracelular de miembros de la maquinaria proteica que regulan la formación de extensiones de membrana. RhoB co-localiza con Rac en vesículas intracelulares e inhibe su activación y el tráfico de esta GTPasa hacia la membrana plasmática. Así mismo, RhoB inhibe la actividad de la serina quinasa Akt y evidencias sugieren que también podría impedir su tráfico hacia la periferia celular. La inhibición directa tanto de Rac como de Akt retrasa la recuperación de la barrera, que además se ve severamente afectada por inhibidores globales del tráfico intracelular. En cambio, la inducción de la translocación de Rac a la membrana plasmática acelera la reformación de la monocapa. En conclusión, nuestros resultados indican que la regulación específica del tráfico intracelular de Rac y Akt por parte de RhoB controla la integridad de la barrera endotelial durante la inflamación, actuando esta GTPasa como un promotor de la disfunción endotelialThe endothelium forms a monolayer of cells that lines on the intimal surface of the blood vessels and physically separates the bloodstream from the underlying tissues. Preserving endothelial integrity is required for the correct termination of the inflammatory reactions. Inflammation is present in some of the most prevalent diseases in our society. Endothelial barrier function could be endangered due to the combined action of pro-inflammatory cytokines and leukocytes , which could lead to an uncontrolled and pathologic inflammatory response. Indeed, endothelial barrier dysfunction underlies chronic inflammatory diseases. In searching for new proteins essential for the human endothelial inflammatory response, we have found that the endosomal Rho GTPase RhoB is upregulated in response to inflammatory cytokines and expressed in the endothelium of chronically inflamed tissues. RhoB, and the closely related RhoA and RhoC, play redundant roles in regulating F-actin levels and additive roles in the maintenance of barrier integrity in unstimulated HUVECs. None of the proteins had relevant roles in long-term barrier disruption in response to TNF or in leukocyte transmigration in vitro. However, RhoB specifically inhibits barrier restoration after acute cell contraction by preventing plasma membrane extension. During barrier restoration, a two-way RhoB trafficking between vesicles containing RhoB nanoclusters and nascent plasma membrane protrusions is induced. We show that RhoB regulates the intracellular trafficking of proteins that controls membrane spreading. We further show that RhoB colocalizes with Rac in Rab5-positive endosomes and negatively regulates Rac1 activity and trafficking to the plasma membrane during barrier recovery. Furthermore, inhibition of endosomal trafficking impairs, whereas induction of Rac translocation to the plasma membrane accelerates, barrier reformation. In addition, we show that RhoB controls Akt activation and we have evidences that RhoB could also regulate Akt trafficking towards plasma membrane during recovery. In conclusion, RhoB-specific regulation of Rac and Akt intracellular trafficking controls endothelial barrier integrity during inflammation. RhoB upregulation exacerbates endothelial responses to stimuli inducing acute contractio

Small-Molecule Therapeutic Perspectives for the Treatment of Progeria

Hutchinson–Gilford progeria syndrome (HGPS), or progeria, is an extremely rare disorder that belongs to the class of laminopathies, diseases characterized by alterations in the genes that encode for the lamin proteins or for their associated interacting proteins. In particular, progeria is caused by a point mutation in the gene that codifies for the lamin A gene. This mutation ultimately leads to the biosynthesis of a mutated version of lamin A called progerin, which accumulates abnormally in the nuclear lamina. This accumulation elicits several alterations at the nuclear, cellular, and tissue levels that are phenotypically reflected in a systemic disorder with important alterations, mainly in the cardiovascular system, bones, skin, and overall growth, which results in premature death at an average age of 14.5 years. In 2020, lonafarnib became the first (and only) FDA approved drug for treating progeria. In this context, the present review focuses on the different therapeutic strategies currently under development, with special attention to the new small molecules described in recent years, which may represent the upcoming first-in-class drugs with new mechanisms of action endowed with effectiveness not only to treat but also to cure progeria.Depto. de Química OrgánicaFac. de Ciencias QuímicasTRUEThe Progeria Research FoundationMinisterio de Ciencia e Innovaciónpu

Panoster: End-to-end Panoptic Segmentation of LiDAR Point Clouds

Panoptic segmentation has recently unified semantic and instance segmentation, previously addressed separately, thus taking a step further towards creating more comprehensive and efficient perception systems. In this paper, we present Panoster, a novel proposal-free panoptic segmentation method for LiDAR point clouds. Unlike previous approaches relying on several steps to group pixels or points into objects, Panoster proposes a simplified framework incorporating a learning-based clustering solution to identify instances. At inference time, this acts as a class-agnostic segmentation, allowing Panoster to be fast, while outperforming prior methods in terms of accuracy. Without any post-processing, Panoster reached state-of-the-art results among published approaches on the challenging SemanticKITTI benchmark, and further increased its lead by exploiting heuristic techniques. Additionally, we showcase how our method can be flexibly and effectively applied on diverse existing semantic architectures to deliver panoptic predictions.Comment: Preprint of IEEE RA-L articl

Segmenting Known Objects and Unseen Unknowns without Prior Knowledge

Panoptic segmentation methods assign a known class to each pixel given in input. Even for state-of-the-art approaches, this inevitably enforces decisions that systematically lead to wrong predictions for objects outside the training categories. However, robustness against out-of-distribution samples and corner cases is crucial in safety-critical settings to avoid dangerous consequences. Since real-world datasets cannot contain enough data points to adequately sample the long tail of the underlying distribution, models must be able to deal with unseen and unknown scenarios as well. Previous methods targeted this by re-identifying already-seen unlabeled objects. In this work, we propose the necessary step to extend segmentation with a new setting which we term holistic segmentation. Holistic segmentation aims to identify and separate objects of unseen unknown categories into instances, without any prior knowledge about them, while performing panoptic segmentation of known classes. We tackle this new problem with U3HS, which finds unknowns as highly uncertain regions and clusters their corresponding instance-aware embeddings into individual objects. By doing so, for the first time in panoptic segmentation with unknown objects, our U3HS is trained without unknown categories, reducing assumptions and leaving the settings as unconstrained as in real-life scenarios. Extensive experiments on public data from MS COCO, Cityscapes, and Lost&Found demonstrate the effectiveness of U3HS for this new, challenging, and assumptions-free setting called holistic segmentation.Comment: Accepted at ICCV 202

Depredación de armadillo (dasypus novemcinctus) por jaguar (panthera onca) en México

Researschers have analized the diet of the jaguar (Panthera onca) in several countries throughout its distribution in America.  Their diet has been documented to include a wide variety of species of medium-size mammals such as armadillos. However, and despite being one of the most studied felines in Mexico, until now the predation of armadillos by P. onca had not been documented with photographic evidence. 10 stations with camera traps were set within the sub-evergreen tropical forest near water bodies, roads and trails. This study presents the first record of predation of a nine-banded armadillo (Dasypus novemcinctus) by jaguar in the Nuevo Becal ejido, a site adjacent to the Calakmul Biosphere Reserve, Campeche in the Southeastern Mexico. The documented information helps us to understand the dynamics in the trophic chains of ecologically and socio-economically important species, especially in sites adjacent to nature reserves where the human population is in constant interaction with wildlife. Investigaciones han analizado la dieta del jaguar (Panthera onca) en varios países a lo largo de su distribución en América.  Se ha documentado que su dieta incluye una gran variedad de especies de mamíferos de talla mediana como los armadillos.  Sin embargo, y a pesar de ser uno de los felinos más estudiados en México, hasta ahora no se había documentado con evidencia fotográfica la depredación de los armadillos por P. onca. 10 estaciones con fototrampas fueron establecidas dentro de la selva mediana sub-perennifolia en sitios cercanos a cuerpos de agua, caminos y brechas. En este estudio se presenta el primer registro de depredación de un armadillo de nueve bandas (Dasypus novemcinctus) por jaguar en el ejido Nuevo Becal, un sitio adyacente a la reserva de la Biosfera de Calakmul, Campeche, en el sureste de México.  La información documentada nos ayudaría a comprender la dinámica en las cadenas tróficas de especies ecológica y socio-económicamente importantes, sobre todo, en sitios adyacentes a las reservas naturales en donde la población humana está en constante interacción con la vida silvestre.&nbsp