7 research outputs found
Violent Universe. High-energy astrophysics and cosmology in the twenty-first century
Get PDFWe see the sky and admire its regularity and stability, its apparent immutability. We have always done so; it does not come as a surprise, since humans have always been startled by any change in the sky, associating it with omens or the mood swings of gods. At that time, they might call these changes «new stars», even if they were, for example, a supernova explosion, as in the case of Tycho’s supernova in the sixteenth century
La modelitzación matemática de los procesos de competición entre lenguas: estudio comparativo de la evolución de los usos lingüísticos en Cataluña y el País Valenciano
Get PDFL’article vol respondre la pregunta següent: és aplicable el model dinàmic de la desaparició de les llengües proposat el 2003 per Abrams i Strogatz a les dades demolingüístiques del País Valencià i de Catalunya de què disposem? Les dues recerques que presentem ─elaborades pel nostre grup de recerca─ s’inscriuen en l’anàlisi dels processos de substitució i de reversió lingüística. La modelització del sistema mitjançant equacions diferencials ens permet estudiar si la dinàmica del sistema és de desaparició o no. En el segon cas, serien necessaris nous models que permeteren canvis de tendència. Aquesta modelització és una eina fonamental per a l'estudi de sistemes socials. Concloem que el model d’Abrams i Strogatz és aplicable a la tendència decreixent del nombre de parlants de català que es dóna al País Valencià, però, per contra, no és aplicable a l’evolució del sistema a Catalunya.The article wants to answer the following question: is the dynamic model of the disappearance of languages proposed in 2003 by Abrams and Strogatz applicable to the demolinguisticdata of the Valencian Country and Catalonia? The two research works we present - elaborated by our research group - are part of the analysis of the substitution and linguistic reversal processes. The modeling of the system through differential equations allows us to study whether the dynamics of the system is disappearing or not. In the second case, new models would be necessary to allow changes in trend. This modeling is a fundamental tool for the study of social systems. We conclude that the model of Abrams and Strogatz is applicable to the decreasing trend in the number of Catalan speakers in the Valencian Country, but, on the contrary, is not applicable to the evolution of the system in Catalonia.El artículo pretende responder la siguiente pregunta: ¿es aplicable el modelo dinámico de la desaparición de las lenguas propuesto en 2003 por Abrams i Strogatz a los datos lingüísticos del País Valenciano y Cataluña que tenemos? Las dos investigaciones que presentamos –elaboradas por nuestro equipo de investigación– se inscriben en el análisis de los procesos de substitución lingüística. La modelización del sistema mediante ecuaciones diferenciales nos permite estudiar si la dinámica del sistema es la desaparición o no. En el segundo caso, serían necesarios Nuevos modelos que permiten cambios de tendencia. Esta modelización es una herramienta fundamental para el estudio de sistemas sociales. Concluimos que el modelo de Abrams y Strogatz es aplicable a la tendencia decreciente del número de hablantes de catalán que se da en el País Valenciano, pero no es aplicable a la evolución del sistema en Cataluña
Reduced precipitation can induce ecosystem regime shifts in lakes by increasing internal nutrient recycling
Get PDF© The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Eutrophication is a main threat to continental aquatic ecosystems. Prevention and amelioration actions have been taken under the assumption of a stable climate, which needs reconsideration. Here, we show that reduced precipitation can bring a lake ecosystem to a more productive regime even with a decline in nutrient external load. By analyzing time series of several decades in the largest lake of the Iberian Peninsula, we found autocorrelated changes in the variance of state variables (i.e., chlorophyll and oxygen) indicative of a transient situation towards a new ecosystem regime. Indeed, exceptional planktonic diatom blooms have occurred during the last few years, and the sediment record shows a shift in phytoplankton composition and an increase in nutrient retention. Reduced precipitation almost doubled the water residence time in the lake, enhancing the relevance of internal processes. This study demonstrates that ecological quality targets for aquatic ecosystems must be tailored to the changing climatic conditions for appropriate stewardship.Project "Control limnológico bianual intensivo del lago de Sanabria," funded by the Confederación Hidrográfica del Duero (Ministry for the Ecological Transition and the Demographic Challenge), commissioned to the Centre for Hydrographic Studies (CEDEX), CIEMAT and other research institutions (Ref. 452-A-640.01.01/2014), to study the ecological functioning of Lake Sanabria and its basin (2015–2019).Peer reviewe
Predicció de l'ús del català mitjançant la classificació supervisada
No full textUn dels principals reptes que ha tingut i té la sociologia del llenguatge és esbrinar quines són les variables que influeixen en els usos lingüístics. En la recerca que presentem ens valem dels mètodes d'una àrea de la intel·ligència artificial, l'aprenentatge automàtic (machine learning), que estudia la implementació de mètodes computacionals que permeten induir models de coneixement a partir d'informació que prové de dades d'exemple disponibles, per a escatir si algun d'aquests millora la predicció del grau d'utilització de la llengua catalana aconseguida fins ara. Hi hem fet servir tres mètodes de classificació supervisada: Naive Bayes, arbres de decisió i màquines de vectors de suport.
Per a complir aquesta comesa calia un corpus empíric que ens permetera tant la comprovació del nivell de predicció d'un model teòric com la seua validesa en diferents contextos sociolingüístics. Les recerques que coneixem que tenen uns percentatges més alts de predicció són les dutes a terme per Querol, que han estat avaluades en tots els territoris on es parla català. La investigació que hem fet amb aquestes dades permet concloure que la classificació supervisada pot servir per a construir models de predicció del grau d'ús del català amb un percentatge d'encert que supera els aconseguits en les investigacions precedents. Amb la qual cosa podem establir quines són les variables més informatives. A més, també ens ajuda a resoldre el problema metodològic de la divisió en grups lingüístics i palesa que l'ús és un sistema continu.One of the main challenges that the sociology of language has faced is the determination of the variables that govern the use of a language. Inspired by the field of artificial intelligence, in this study we make use of machine learning as a suitable approach to implement computational methods that permit the induction of linguistic use models derived from the available data. We aim to improve the level of prediction for the degree of use of the Catalan language achieved up to now. To this end, we have used three supervised classification techniques: Naive Bayes, decision trees, and support vector machines.
We needed an empirical corpus that would allow us to test the prediction level of a theoretical model as well as its validity within different sociolinguistic situations. To the best of our knowledge, the work by Querol is the one providing the highest prediction success in all the Catalan-speaking territories. Thus, the research presented in this paper uses that data to conclude that supervised classification can be used to successfully determine prediction models for the degree of use of Catalan that outperform previous attempts and that allow us to identify the most relevant variables of the problem. Moreover, it also helps us to solve the methodological problem of the division of linguistic groups and shows that the use of a language is a continuous system rather than a discrete one
On the location of the supermassive black hole in CTA102
No full textContext. Relativistic jets in active galactic nuclei are one of the most powerful phenomena in the Universe. They form in the surroundings of the supermassive black holes as a by-product of accretion onto the central black hole in active galaxies. The flow in the jets propagates at velocities close to the speed of light. The distance between the first part of the jet that is visible in radio images (core) and the black hole is still a matter of debate. Aims. Only very-long-baseline interferometry observations resolve the innermost compact regions of the radio jet. These observations can access the jet base, and by combining data at different wavelenghts, address the physical parameters of the outflow from its emission. Methods. We have performed an accurate analysis of the frequency-dependent shift of the VLBI core location for a multi-wavelength set of images of the blazar CTA 102 including data from 6 cm down to 3 mm. Results. The measure of the position of the central black hole, with mass ~10^8.93M_⊙, in the blazar CTA 102 reveals a distance of ~8 × 10^4 gravitational radii to the 86 GHz core, in agreement with similar measures obtained for other blazars and distant radio galaxies, and in contrast with recent results for the case of nearby radio galaxies, which show distances between the black hole and the radio core that can be two orders of magnitude smaller
Àlgebra i Geometria
No full textAquest manual recull el contingut de les assignatures d’Àlgebra i Geometria I i II, del primer curs del grau en Física de la Universitat de València, a més de tractar temes complementaris que constitueixen la base matemàtica de les teories físiques actuals: la mecànica quàntica i la teoria de la relativitat. Els conceptes que s’hi desenvolupen són bàsics en la formació de físics, matemàtics i enginyers.Este manual recoge el contenido de las asignaturas Álgebra y Geometría I y II, del primer curso del Grau de Física de la Universitat de València, además de tratar temas complementarios que constituyen la base matemática de las teorías físicas actuales: la mecánica cuántica y la teoría de la relatividad. Los conceptos que se desarrollan son básicos en la formación de físicos, matemáticos e ingenieros
Methylation regulation of Antiviral host factors, Interferon Stimulated Genes (ISGs) and T-cell responses associated with natural HIV control
Get PDFGWAS, immune analyses and biomarker screenings have identified host factors associated within vivoHIV-1 control. However, there is a gap in the knowledge about the mechanisms that regulate the expression of such host factors. Here, we aimed to assess DNA methylation impact on host genome in natural HIV-1 control. To this end, whole DNA methylome in 70 untreated HIV-1 infected individuals with either high (>50,000 HIV-1-RNA copies/ml, n = 29) or low (<10,000 HIV-1-RNA copies/ml, n = 41) plasma viral load (pVL) levels were compared and identified 2,649 differentially methylated positions (DMPs). Of these, a classification random forest model selected 55 DMPs that correlated with virologic (pVL and proviral levels) and HIV-1 specific adaptive immunity parameters (IFNg-T cell responses and neutralizing antibodies capacity). Then, cluster and functional analyses identified two DMP clusters: cluster 1 contained hypo-methylated genes involved in antiviral and interferon response (e.g.PARP9,MX1, andUSP18) in individuals with high viral loads while in cluster 2, genes related to T follicular helper cell (Tfh) commitment (e.g.CXCR5andTCF7) were hyper-methylated in the same group of individuals with uncontrolled infection. For selected genes, mRNA levels negatively correlated with DNA methylation, confirming an epigenetic regulation of gene expression. Further, these gene expression signatures were also confirmed in early and chronic stages of infection, including untreated, cART treated and elite controllers HIV-1 infected individuals (n = 37). These data provide the first evidence that host genes critically involved in immune control of the virus are under methylation regulation in HIV-1 infection. These insights may offer new opportunities to identify novel mechanisms ofin vivovirus control and may prove crucial for the development of future therapeutic interventions aimed at HIV-1 cure. Author summary The infection with the human immunodeficiency virus (HIV), as for other viral infections, induce global DNA Methylation changes in the host genome. Herein, we identified for first time the methylation impact on host genome in untreated HIV-1 infection with different degrees ofin vivovirus control. Specifically, we observed that individuals with a better HIV-1 control showed a hypermethylation of genes associated with antiviral and interferon pathways and the hypomethylation of genes associated with the differentiation process of T follicular helper cells. Interestingly, these epigenetic imprints in host genome were strongly correlated with virus content and HIV-specific T cell responses. Therefore, we propose DNA Methylation as the regulation mechanism of host genes involved in immune HIV-1 control that could interfere in the efficacy of cure strategies. We also highlight the importance of DNA Methylation to regulate immune responses not only in HIV-1 but also in chronic infections or other pathologic situations associated with a sustained activation of the immune system
