Long-term x-ray variability of active galactic nuclei and x-ray binaries

In this thesis I present long-term X-ray variability studies of sources belonging to two of the big groups of objects present in the X-ray universe: the Active Galactic Nuclei (AGN) and the X-ray Binaries (XRBs). After an introduction to X-ray astronomy in chapter 1, a description of the classification, obser-vational properties, and variability characteristics of AGN and XRBs are presented in chapter 2. Chapter 3 refers to mathematical methods for the time series analysis. Currently, two methods for the variability analysis of astronomical sources, especially in searching for periodic signals, are common in astronomy: periodogram analysis and epoch-folding. Other methods, as the dynamical power spectra or the wavelet decomposition of the light curve, can give information on the possible variable spectral properties of the data (i.e., change of periods, amplitude, and phases). Methods to examine the X-ray variability directly in the time domain, as the Structure Function (SF) and Excess Pair Fraction (EPF), are also commonly used in time-series analysis in astronomy. An alternative analysis method in the time domain is the Linear State Space Model (LSSM) which explicitly models the noise of astronomical data and allows to estimate the hidden stochastic process. For the detection of periodic signals, it is worth scrutinizing the methods used to determine their significance. Methods to compute significance levels for the existence of QPOs in X-ray light curves which take the red-noise character of the astronomical objects into account are discussed in chapter 4. The following chapters of the thesis contain the results of long-term variability studies applying the methods and theory described in the previous chapters. In chapter 5 two variability studies of AGN are presented. I report on the analysis from ~110 ks of X-ray observations of the AGN Cen A carried out with the Rossi X-ray Timing Explorer (RXTE ) satellite between 1996 and 2000. Spectral and temporal variability on time scales from years to tens of minutes are present. The X-ray spectrum can be well described by a heavily absorbed power-law with photon index 1.8 and a narrow iron line due to fluorescence of cold matter. The measured column depth decreased by about 30% between 1996 and 2000, while the detected 2-10 keV continuum flux remained constant between 1996 and 1998, but increased by 60% in 2000. Since in all observations the iron line ux did not vary, a corresponding decrease in equivalent width was noted. No appreciable evidence for a reection continuum in the spectrum was detected. We present the interpretation of the iron line strength through Monte Carlo computations of various geometries. Applying epoch-folding and periodogram analysis to the XMM-Newton observation of the Sey-fert galaxy Mrk 766, a possible QPO at a time scale of 4200 s has been reported. Our computation of the significance of this QPO, however, shows that the 4200 s peak is not significant at the 95% level. We conclude that the 4200 s feature is an artifact of the red-noise process and not the result of a physical process within the galaxy. In chapter 6 temporal variability behavior from long-term light curves obtained with the All-Sky Monitor (ASM) on board the RXTE is reviewed. Results of searches for periodicities in the ASM light curves from X-ray binaries are presented. The ASM light curves show a wide variety of phenomena. In conclusion, chapter 7 presents a summary and outlook on future work.In dieser Dissertation beschäftige ich mich mit der Langzeitvariabilität von zwei Klassen von Röntgenobjekten: Aktiven Galaxiekernen (engl. Active Galactic Nuclei, AGN) und Röntgendoppelsternen (engl. X-ray Binaries, XRBs). Nach einer Einleitung in die Röntgenastronomie im Kapitel 1 folgt in Kapitel 2 eine Beschreibung der Klassifikationen, der beobachteten Eigenschaften und der Variabilitätscharakteristika von AGN und von XRBs. Kapitel 3 bezieht sich auf mathematische Methoden der Zeitreihenanalyse. Zur Zeit werden in der Astronomie vor allem zwei Techniken für die Variabilitätsanalyse, speziell der Periodensuche, angewandt: Periodogramm- und Faltungsmethoden. Andere Methoden, wie das dynamische Periodogramm oder die Wavelet-Zerlegung einer Lichtkurve können Informationen über eine mögliche spektrale Variabilität der Daten (d.h. eine Änderung von Perioden, Amplituden und Phasen) geben. Methoden, welche die Röntgenvariabilität direkt im Zeitbereich überprüfen, wie die Strukturfunktion (SF) und das excess pair fraction (EPF), werden ebenfalls häufig in der astronomischen Zeitreihenanalyse verwendet. Eine weitere Methode im Zeitbereich ist das lineare Zustandsraummodell (LSSM) welches das Rauschen in den Daten explizit modelliert und eine Abschätzung des versteckten stochastischen Prozesses erlaubt. Im Anschluss daran werden in Kapitel 4 Methoden besprochen, welche die Signifikanzniveaus für das Bestehen von QPOs in Röntgenlichkurven bestimmen und die den Charaker des roten Rauschens der astronomischen Objekte in Betracht ziehen. Die folgenden Kapitel dieser Dissertation enthalten Ergebnisse von Langzeitvariabilitätsstudien, in denen die in den vorhergehenden Kapiteln beschriebenen Methoden und Theorien angewendet wurden. In Kapitel 5 werden zwei Variabilitätsstudien von AGN vorgestellt. Ich berichte über die Analyse von insgesamt ~110 ks Beobachtungen des AGN Cen A, die mit dem Satelliten Rossi X-ray Timing Explorer (RXTE ) zwischen 1996 und 2000 durchgeführt wurden. Spektrale und zeitliche Variabilitäten auf Zeitskalen von Jahren bis zu Minuten sind zu beobachten. Das Röntgenspektrum kann durch ein stark absorbiertes Potenzgesetz mit Photonenindex 1.8 und einer schmalen Eisenlinie gut beschrieben werden. Die gemessene Säulendichte verringerte sich um ungefähr 30% zwischen 1996 und 2000, während der ermittelte 2-10 keV Kontinuums-Fluss zwischen 1996 und 1998 konstant blieb, jedoch in 2000 um 60% zunahm. Da in allen Beobachtungen der Fluss der Eisenlinie nicht schwankte, wurde eine entsprechende Abnahme ihrer Äquivalentsbreite beobachtet. Es wurde kein Hinweis auf ein Reflexions-Kontinuum im Spektrum gefunden. Wir stellen die Deutung der Stärke der Eisenlinie durch Monte-Carlo Simulationen verschiedener Geometrien dar. Durch die Anwendung von epoch-folding und Periodogrammanalyse auf eine XMM-Newton Beobachtung der Seyfert Galaxie Mrk 766, konnte über eine mögliche QPO auf einer Zeitskala von 4200 s berichtet werden. Unsere Berechnung der Signifikanz dieser QPO zeigt jedoch, dass die 4200 s Modulation nicht auf dem 95% Niveau signifikant ist. Ich stelle fest, dass die 4200 s Eigenschaft ein Kunstprodukt des roten Rauschen und nicht das Resultat eines physikalisches Prozesses innerhalb der Galaxie ist. In Kapitel 6 wird die Zeitvariabilität von Langzeitlichtkurven, die mit dem All-Sky Monitor (ASM) an Bord des Rossi X-ray Timing Explorer RXTE gewonnen wurden, untersucht. Resultate der Suche nach Periodizitäten in den ASM Lichtkurven von Röntgendoppelsternen werden dargestellt. Die ASM Lichtkurven zeigen eine grosse Vielzahl von Phänomenen. Zum Abschluss dieser Dissertation gibt Kapitel 7 eine Zusammenfassung und einen Ausblick auf zukünftige Arbeiten

Materials Inclusius a l’Aula

Dotzenes Jornades de Foment de la Investigació de la FCHS (Any 2006-2007

eSGarden: a European initiative to incorporate ICT in schools

[EN] Knowledge transfer to the society is undoubtedly one of the main objectives of Universities. However, it is important that these advances reach the youngest, many of them, future university students. Having this in mind, a European project around how incorporating ICT in school gardens was proposed (SCHOOL GARDENS FOR FUTURE CITIZENS, 2018-1-ES01-KA201-050599). In this project, both universities and schools, belonging to five European countries, are collaborating with public and private organizations with social concerns, environmental responsibility and sustainability. School gardens is a broad topic that combine technological needs for managing and control with education in values of environmental sustainability, social inclusion and citizenship, transmission of tradition, and the promotion of digital culture in both girls and boys from the early school stages. These last aspects are aligned with some sustainable development targets (SDGs), such as ensuring healthy lives and promote well-being for all at all ages, inclusive and equitable quality education, gender equality or responsible consumption. A further challenge of the consortium is to extend the proposed approach to other schools throughout Europe with the same interests and impact, considering cultural diversity and climate differences.Blanc Clavero, S.; Benlloch-Dualde, J. (2019). eSGarden: a European initiative to incorporate ICT in schools. En Proceedings 5th CARPE Conference: Horizon Europe and beyond. Editorial Universitat Politècnica de València. 29-37. https://doi.org/10.4995/CARPE2019.2019.10209OCS293

Learning supported by peer production and digital ink

© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper describes experiences that combine digital peer production with digital ink affordances. Rather than preparing papers to obtain a summative final mark, students work over the course of the term producing different small learning resources such as short engineering problems, reasoning or synthesis where the lecturer acts as manager and supervisor. Teacher intervention is carried out using digital ink over each individual student production being possible to share the results throughout a public or group repository and in class offering a pro-active argument about preventing common mistakes. In order to enhance students programming skills important efforts are oriented to produce learning objects in the form of Java applets. It has the additional advantage of fostering collaborative knowledge construction because any object serves to the whole group as learning material as soon as it is already produced and validated. Qualitative and quantitative results show both an overall satisfaction from students participating in the experiences, and better results in the common written exams, when compared to the other groups following the traditional method.Benlloch-Dualde, J.; Blanc Clavero, S. (2014). Learning supported by peer production and digital ink. IEEE. doi:10.1109/FIE.2014.7044090

Producción de Objetos de Aprendizaje en Cursos de Ingeniería

[EN] This paper presents an innovation research on promoting self-learning in engineering university courses. The work is focused on students' homework activity that consists of producing Learning digital Objects. The digital objects are self-contained and reusable within the course framework attending to a suitable work planning and supported by digital tools. Additionally to help the student on the achievement of curricula competences by producing these objects, the objects are also available to the whole group in the form of a digital collection of self-study material adapted to the group idiosyncrasy. The paper describes a practical case of study, analysesEste trabajo ha sido parcialmente subvencionado por la E.T.S de Ingeniería Informática de la Universitat Politècnica de València.Blanc Clavero, S.; Benlloch-Dualde, JV. (2013). Producción de Objetos de Aprendizaje en Cursos de Ingeniería. VAEP-RITA. Versión Abierta Español-Portugués. 1(2):80-87. http://hdl.handle.net/10251/39135S80871

Helping Teachers Create a Dynamic Learning Environment Using Pen-Based Technology

[EN] There is evidence that Pen-based Technologies (PBTs) can facilitate radical changes that would make it possible to address problems typically associated with lecture-based pedagogical models. In the context of universitylevel Computer Science studies, there is widespread consensus that PBTs—and tablet PCs, in particular—are tools that have great potential for encouraging interaction in the classroom and promoting a far more dynamic learning environment. In view off the complexity of these types of technology and their explosive evolution, it would be advisable to assist teachers who wish to utilize them by developing strategies based on a conceptualization of their educational capabilities. With this objective in mind, this article analyzes the use of concept maps as tools for modeling both the instructional domain and the PBTs domain. To validate the proposed approach, a number of workshops were conducted, in which professors of Engineering were given a presentation on the educational capabilities of these technologies and then had the opportunity to experiment with tablet PCs and other digital ink devices. Participants completed a prequestionnaire at the start of the workshop; its questions were generated from a generic concept map for the instructional domain, and its purpose was to list each professor’s instructional requirements. Next, recommendations for use were developed, based on the PBTs concept map, and converted to the questions on a post-questionnaire completed at the end of the workshop, on which the teachers indicated the degree to which they agreed with the recommendations. More than 70 professors from different departments participated in these workshops, and their overall evaluation was quite favorable.Benlloch-Dualde, JV.; Buendía García, F.; Cano Escribá, JC.; Blanc Clavero, S.; Lemus Zúñiga, LG. (2013). Helping Teachers Create a Dynamic Learning Environment Using Pen-Based Technology. International Journal of Technologies in Learning. 19(2):107-120. http://hdl.handle.net/10251/53173S10712019

Adding value to tumor staging in head and neck cancer: The role of metabolic parameters as prognostic factors

Background: Validated biomarkers in head and neck squamous cell carcinoma (HNSCC) are scarce. Methods: We retrospectively analyzed 62 patients with HNSCC treated with radiotherapy +/− concurrent chemotherapy. Pretreatment metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were measured in a 18F-FDG positron emission tomography using a liver dependent standardized uptake value threshold. Cox regression analyses were performed to find associations with disease-free survival (DFS) and overall survival (OS). Results: High values of MTV (>37 ml) were independently associated with a worse DFS (hazard ratio [HR] = 3.45; 95% confidence interval [CI], 1.52–7.84) and OS (HR = 3.27; 95% CI, 1.41–7.57). Similar results were found for high values of TLG (>247 g) for DFS (HR = 3.32; 95% CI, 1.44–7.65) and OS (HR = 3.42; 95% CI, 1.45–8.07). Conclusions: MTV and TLG can be considered as independent prognostic factors for DFS and OS in patients with HNSCC. Considering how easily obtainable they are, they may be useful for predicting clinical outcomes in these patient

¿Cómo ayudar a los docentes a crear entornos de aprendizaje dinámicos mediante el uso de la tinta digital?

There is evidence that Pen-Based Technologies (PBTs) can facilitate radical changes that would make it possible to address problems typically associated with lecture-based pedagogical models. In the context of university-level Computer Science studies, there is widespread consensus that PBTs —and tablet PCs, in particular— are tools that have great potential for encouraging interaction in the classroom and promoting a far more dynamic learning environment. In view off the complexity of these types of technology and their explosive evolution, it would be advisable to assist teachers who wish to utilize them by developing strategies based on a conceptualization of their edu-cational capabilities. With this objective in mind, this article analyzes the use of concept maps as tools for modeling both the instructional domain and the PBTs domain. To validate the proposed approach, a number of workshops were conducted, in which professors of Engineering were given a presentation on the educational capabilities of these technologies and then had the opportunity to experiment with tablet PCs and other digital ink devices. Participants completed a pre-questionnaire at the start of the workshop; its questions were generated from a generic concept map for the instructional domain, and its purpose was to list each professor’s instructional requirements. Next, recommendations for use were developed, based on the PBTs concept map, and converted to the questions on a post-questionnaire completed at the end of the workshop, on which the teachers indicated the degree to which they agreed with the recommendations. More than 70 professors from different departments participated in these workshops, and their overall evaluation was quite favorable.Benlloch-Dualde, JV.; Buendía García, F.; Cano Escribá, JC.; Blanc Clavero, S.; Lemus Zúñiga, LG. (2013). ¿Cómo ayudar a los docentes a crear entornos de aprendizaje dinámicos mediante el uso de la tinta digital?. TEXTOS de la CiberSociedad. 17(1):85-98. http://hdl.handle.net/10251/40394S859817