The H0H_0 tension in light of vacuum dynamics in the Universe

Despite the outstanding achievements of modern cosmology, the classical dispute on the precise value of $H_0$, which is the first ever parameter of modern cosmology and one of the prime parameters in the field, still goes on and on after over half a century of measurements. Recently the dispute came to the spotlight with renewed strength owing to the significant tension (at $>3\sigma$ c.l.) between the latest Planck determination obtained from the CMB anisotropies and the local (distance ladder) measurement from the Hubble Space Telescope (HST), based on Cepheids. In this work, we investigate the impact of the running vacuum model (RVM) and related models on such a controversy. For the RVM, the vacuum energy density $\rho_{\Lambda}$ carries a mild dependence on the cosmic expansion rate, i.e. $\rho_{\Lambda}(H)$, which allows to ameliorate the fit quality to the overall $SNIa+BAO+H(z)+LSS+CMB$ cosmological observations as compared to the concordance $\Lambda$CDM model. By letting the RVM to deviate from the vacuum option, the equation of state $w=-1$ continues to be favored by the overall fit. Vacuum dynamics also predicts the following: i) the CMB range of values for $H_0$ is more favored than the local ones, and ii) smaller values for $\sigma_8(0)$. As a result, a better account for the LSS structure formation data is achieved as compared to the $\Lambda$CDM, which is based on a rigid (i.e. non-dynamical) $\Lambda$ term.Comment: Accepted for publication in Phys. Lett. B. Significantly extended discussion, two figures and references adde

Programación de un software para el prediseño del sistema de potencia de un satélite de órbita baja "Satellite Power simulation"

Programación de un software para el prediseño del sistema de potencia de un satélite de órbita baja. satellite power simulato

Alteraciones a medio y largo plazo en el rendimiento cognitivo y potenciales evocados (P300) en policonsumidores recreativos de éxtasis

Consultable des del TDXDescripció del recurs: el 9 d'abril 2009Títol obtingut de la portada digitalitzadaEn la actualidad se desconocen con certeza los efectos derivados del uso prolongado del "éxtasis" (MDMA) con fines recreativos, aunque existen numerosos indicios de una clara asociación entre el uso habitual e intenso de esta sustancia y la aparición de alteraciones cognitivas y neurofisiológicas en seres humanos. Estos efectos se atribuyen a la neurodegeneración selectiva y persistente del sistema serotoninérgico cerebral observada en experimentación preclínica con animales. Estos indicios son motivo de preocupación ya que cabe la posibilidad que la persistencia de estas alteraciones a lo largo del tiempo pudieran contribuir a la aparición de deterioro cognitivo más allá del proceso de envejecimiento normal. El objetivo principal de este trabajo de investigación es aportar nuevas pruebas de la neurotoxicidad del éxtasis como factor de riesgo en la aparición de déficit cognitivos y cambios electrofisiológicos cerebrales (potencial evocado P300) a medio y largo plazo. Otros objetivos perseguidos fueron: estudiar el curso de dichas alteraciones a lo largo del tiempo, explorar las relaciones existentes entre los parámetros de latencia y amplitud de la onda P300, funciones cognitivas y consumo acumulado de éxtasis a lo largo de la vida (consumo-vida). Por último, se pretendió explorar la contribución del uso concomitante de cannabis sobre dichas alteraciones. Para ello se realizó el seguimiento de una muestra de policonsumidores habituales de éxtasis, consumidores habituales de cannabis y controles no consumidores de sustancias de abuso, durante un período natural de 3 años dividido en dos períodos diferenciados de 24 y 12 meses. Los resultados muestran que los consumidores de éxtasis obtienen rendimientos cognitivos significativamente más pobres en comparación al grupo control pero no respecto al grupo cannabis tanto a nivel basal como a medio y largo plazo. A largo plazo los consumidores de éxtasis presentan déficit persistentes de carácter subclínico en funciones ejecutivas, memoria episódica y velocidad de procesamiento mental. Se hallaron relaciones dosis-respuesta entre el consumo-vida de éxtasis y el rendimiento mnésico y velocidad de procesamiento mental. El consumo-vida de cannabis y una edad de inicio temprana en el uso de esta sustancia contribuyen a explicar los déficit observados en el grupo éxtasis. En cuanto a la respuesta del potencial evocado P300, no se observan diferencias significativas entre los tres grupos, mostrando valores de latencia y amplitud dentro de la normalidad y sin alteraciones clínicamente relevantes a medio plazo. Los análisis muestran correlaciones significativas entre la latencia del potencial y memoria de trabajo, fluencia verbal, atención dividida y reconocimiento verbal. Se observó una asociación significativa aunque paradójica entre el consumo-vida de cannabis y la latencia de este potencial. No se observaron correlaciones significativas con el uso de éxtasis. Los resultados de este trabajo aportan nuevas pruebas de que el consumo de éxtasis de forma habitual y prolongada en el tiempo, especialmente en cantidades elevadas, induce efectos negativos sobre la cognición en forma de alteraciones discretas de magnitud subclínica, las cuales persisten con un curso estable a medio y largo plazo. Estas manifestaciones cognitivas responden a los efectos neurotóxicos inducidos no sólo por el uso del éxtasis, sino por la interacción éxtasis/cannabis sobre el sustrato cerebral. Por el contrario, el consumo de éxtasis no afecta significativamente a la actividad eléctrica cerebral registrada mediante el potencial evocado P300. En cuanto a la contribución del cannabis, su uso concomitante ejerce efectos solapados sobre la cognición, pero tampoco induce cambios significativos sobre la actividad eléctrica cerebral. Independientemente de cual sea la naturaleza de la interacción entre ambas sustancias, la relevancia clínica de los efectos del éxtasis sobre la cognición es discreta pero no por ello despreciable, ya que los policonsumidores de éxtasis manifiestan alteraciones, aunque éstas son de carácter subclínico. PALABRAS CLAVE: Éxtasis, déficit cognitivos, potenciales evocadosUp to date there is no conclusive evidence on the effects induced by long-term recreational "ecstasy" (MDMA) consumption, although extensive research suggests a clear linkage between prolonged and intensive use of this substance and cognitive and neurophysiological changes in humans. Animal studies raise the possibility that these alterations could respond to selective and persistent neurodegenerative effects upon central serotonergic systems. There is concern that in humans the persistency of these alterations over long periods of time could contribute to developing cognitive impairment beyond normal aging processes. The main aim of this investigation was to provide new and additional evidence on the neurotoxic effects of ecstasy use as a risk factor associated with short and long-term changes in neurocognitive performance and neuroelectric brain activity (P300 event-related potentials). Other aims explored in the present study were: examine the course of neurocognitive and electrophysiological changes over time, explore the relationships between P300 main components: latency and amplitude with specific cognitive domains and lifetime MDMA cumulative use (lifetime consumption), as well as the relative contribution of cannabis on these alterations. In other to cover these goals, follow-up of a sample of current ecstasy polydrug users, current cannabis users and drug naïve controls was conducted over a natural period of 3 years, divided in two different periods of time: 24 and 12 months. The results of this study showed that at baseline, one year and two years follow-up assessments, ecstasy polydrug users presented significantly poorer cognitive performance than non-drug using controls. No significant differences were found between ecstasy and cannabis users on cognitive tests. In the long-term, ecstasy polydrug users showed consistently persistent subclinical deficits on executive functions, episodic memory and mental processing speed. Significant dose-response relations were found between ecstasy lifetime consumption and performance in memory and mental processing speed. Age at onset of cannabis use before 15 years predicted lower performance in memory and mental processing speed. Concerning P300 response, no group differences were shown on P300 event-related potentials. The analyses revealed significant correlations between P300 latency and specific cognitive domains of working memory, verbal fluency, divided attention and verbal recognition, although the direction of those associations regarding P300 latency, attention and recognition was counterintuitive. Moreover, a significant but paradoxical association emerged between cannabis lifetime use and P300 latency, but no association was found between ecstasy exposure and P300 main components. The results of this study provide new and additional evidence that regular and prolonged ecstasy consumption, especially an intensive pattern of use, induces negative effects on cognition in terms of mild sub-clinical cognitive deficits, which remain persistent and stable in the short and the long-term. Cognitive impairment observed in ecstasy polydrug users supports that not only ecstasy use but ecstasy/cannabis interaction account for the neurotoxic effects upon the brain substrate. On the contrary, ecstasy intake does not affect significantly brain electric activity (P300). Regarding the role of cannabis, co-use of this substance shows overlapping effects on cognition but does not induce significant changes on brain electric activity (P300). No matter the nature of the dynamic interaction between both drugs, the clinical relevance of their effects on cognition is subtle but not negligible, due to the fact that cognitive deficits are found in recreational ecstasy polydrug users, although these are of sub-clinical magnitude

Inhomogeneous cortical synchronization and partial epileptic seizures

Objective: Interictal synchronization clusters have recently been described in several publications using diverse techniques, including neurophysiological recordings and fMRI, in patients suffering from epilepsy. However, little is known about the role of these hypersynchronous areas during seizures. In this work, we report an analysis of synchronization clusters jointly with several network measures during seizure activity; we then discuss our findings in the context of prior literature.Methods: Subdural activity was recorded by electrocorticography (with 60 electrodesplaced at temporal and parietal lobe locations) in a patient with temporal lobe epilepsywith partial seizures with and without secondary generalization (SG). Both interictal andictal activities (during four seizures) were investigated and characterized using local synchronization and complex network methodology. The modularity, density of links, average clustering coefficient, and average path lengthswere calculated to obtain information about the dynamics of the global network. Functional connectivity changes during the seizures were compared with the time evolution of highly synchronized areas.Results: Our findings reveal temporal changes in local synchronization areas during seizuresand a tight relationship between the cortical locations of these areas and the patterns oftheir evolution over time. Seizure evolution and SG appear to be driven by two differentunderlying mechanisms.Fil: Vega Zelaya, Lorena. Hospital Universitario la Princesa; EspañaFil: Pastor, Jesús Eduardo. Hospital Universitario la Princesa; EspañaFil: García de Sola, Rafael. Hospital Universitario la Princesa; EspañaFil: Ortega, Guillermo José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; Argentin