Bayesian analysis of burst gravitational waves from galactic neutron stars

This thesis summarises my work in relation to data analysis for gravitational wave detection. Most of the personal contribution relates to the assessment of the detectability of potential burst-type gravitational wave signals from the galactic population of neutron stars and to the parameter estimation of the models used to represent these signals. A small part of the work, confined to the last chapter, describes the experimental work carried at the beginning of the research period and aimed to measure the shot-noise level of the modulated laser-light in the gravitational wave detectors. Chapter 1 is introductory and presents generic information about gravitational wave radiation, a postulate of the theory of general relativity. The polarisation of the radiation and the approximate values of amplitudes and frequencies of the signals expected from astrophysical events are presented, together with most important gravitational radiation sources for ground-based detectors. Chapter 2 presents the study on the detectability of burst-type gravitational wave signals incoming from neutron stars located in our galaxy. Three differently shaped galactic neutron star populations are introduced and the detectability of ground-based detectors to signals of different polarisation degree coming from these source populations is investigated. Based on the time- and polarisation-averaged antenna pattern and antenna power values, approximated by Monte Carlo methods, detectability is measured in terms of a) the geographical location and orientation of hypothetical detectors, and b) the current detectors, either working individually or as a part of a network. Also, the sidereal times at which each detector is more sensitive to the sources of the neutron star populations defined are inferred. Chapter 3 introduces a mathematical model of the burst-type gravitational wave ringdown signal investigated in this work, which represents a short-lived gravitational polarised radiation generated by an oscillating neutron star: an exponentially damped sinusoid comprised of a sine and a cosine component, of the same frequency but different amplitude, as the two polarisation components of the signal. The model of the signal is given, in the time- and in the frequency-domain. Chapter 4 is devoted to present the Bayesian probability tools necessary to carry out ‘model comparison’ and ‘parameter estimation’ for the detectability study of our particular burst-type signal. Comparison of models allows choosing the one that better represents the data and subsequently focusing on in order to compute the most likely parameter values of that model. Also, in this section, the way in which the detector data can be simulated in the frequency domain, combining the signal and a noise realisation corresponding to the power spectrum of the noise that characterizes the detector, is explained. The likelihood function for a signal corresponding to one oscillation mode and seen by one detector is derived both in the time- and in the frequency-domain. The nested sampling technique is summarised, a useful tool to compute effectively the marginal likelihood of the hypotheses considered. Chapter 5 presents the results of the model selection and the parameter estimation exercise. The expression of the likelihood is generalised so that it can adopt more than one oscillation mode and been seen by various detectors of a network. Depending whether one, f-mode, or two oscillation modes, f and p, are suspect, two different scenarios of various hypotheses are considered. For each hypothesis the minimum strength of the signal to claim detection is studied and a parameter estimation exercise is carried out to characterise the signal and define the location of the source in the sky. Signals of known parameters and differing strengths were injected into the synthetic noise of three advanced detectors comprising a network. The values of the parameters were estimated using Bayesian inference for two different scenarios: when only the f-mode is suspect (scenario 1), or when both f- and p-modes are suspect (scenario 2). Posterior probabilities of the parameters in Scenario 1 are better defined and constrained than those for Scenario 2, due to the added uncertainty of including another oscillation mode. As expected, the uncertainty of the probability distributions of the parameter values decreases and the mode shifts toward the exact injected value as the signal strength increases. For both scenarios the frequency value can be accurately estimated, but not so well the damping time, especially for the p-mode oscillation, which is suspected to have longer time durations than f-modes, typically several seconds. The ability to estimate the polarisation degree of the signal is also quite limited and strong signals are required for the mode of the distribution to approximate the exact value. Similarly, determining the most probable location for the source is possible in both scenarios. The two-fold degeneracy of the sky position and related to the travel time of the signal to the detectors has been broken; relatively strong (high SNR) signals, especially for scenario 2, are needed for the source location to be constrained with accuracy. Chapter 6 presents the experimental work carried out, by which the measuring of the shot-noise level of differently modulated and demodulated laser light was intended. Due to the poor outcome of this experiment and the lack of useful results the emphasis has been placed on a detailed description of the modulation apparatus, opto-electronic set up and the control system put together. Chapter 7 looks to the future and briefly presents how to take this data analysis work forward

An Event Related Field Study of Rapid Grammatical Plasticity in Adult Second-Language Learners

Published: 24 January 2017The present study used magnetoencephalography (MEG) to investigate how Spanish adult learners of Basque respond to morphosyntactic violations after a short period of training on a small fragment of Basque grammar. Participants (n = 17) were exposed to violation and control phrases in three phases (pretest, training, generalization-test). In each phase participants listened to short Basque phrases and they judged whether they were correct or incorrect. During the pre-test and generalization-test, participants did not receive any feedback. During the training blocks feedback was provided after each response. We also ran two Spanish control blocks before and after training. We analyzed the event-related magnetic- field (ERF) recorded in response to a critical word during all three phases. In the pretest, classification was below chance and we found no electrophysiological differences between violation and control stimuli. Then participants were explicitly taught a Basque grammar rule. From the first training block participants were able to correctly classify control and violation stimuli and an evoked violation response was present. Although the timing of the electrophysiological responses matched participants' L1 effect, the effect size was smaller for L2 and the topographical distribution differed from the L1. While the L1 effect was bilaterally distributed on the auditory sensors, the L2 effect was present at right frontal sensors. During training blocks two and three, the violation-control effect size increased and the topography evolved to a more L1-like pattern. Moreover, this pattern was maintained in the generalization test. We conclude that rapid changes in neuronal responses can be observed in adult learners of a simple morphosyntactic rule, and that native-like responses can be achieved at least in small fragments of second language.Support for this project was provided to DD by Spanish Ministry of Science and Innovation (MICINN) under the program “Plan Nacional” (grant reference PSI 2011-24802) and to AB by the Basque Government (Eusko Jaurlaritza) under the program “Ikertzaile ez doktoreen doktoretza-aurreko formakuntza-programa” (grant reference PRE_2015_2_0208)

Closing eyes during auditory memory retrieval modulates alpha rhythm but does not alter tau rhythm

Available online 20 April 2019The alpha power increase that occurs when the eyes are closed is one of the most well-known effects in human electrophysiology. In particular, previous psychological studies have investigated whether eye closure can boost memory performance under certain circumstances, providing contradictory evidence across sensory input modalities. Although alpha power is modulated during different phases of memory and these modulations are correlated with performance, few studies have reported on the relationship between eye closure, memory, and alpha-band power. The present study investigates the influence of eye closure while participants (n = 21) performed an auditory recognition memory task with spoken words during the recording of magnetoencephalography (MEG) data. Our results showed no evidence for a behavioural effect of eye closure in the performance of the task. In addition, electrophysiological responses to the stimuli showed the expected alpha event-related desynchronization (ERD) 0.5–1 s and a high-alpha/beta event-related synchronization (ERS) 1–2 s after word onset. The data showed the expected memory effect, i.e. remembered words elicited greater 10 Hz ERD than forgotten words in the brain regions typically associated with the language network, suggesting a modulation of tau rhythm. Eye closure modulated alpha rhythm only in posterior-parietal and occipital regions. The lack of interaction and the different localizations found for modulations of tau and classical alpha rhythms suggests that these rhythms play distinct functional roles in memory performance.This research was possible thanks to the support of the “Severo Ochoa Program for Centres/Units of Excellence in R&D” (SEV-2015-490). AB was supported by the Basque Government (Eusko Jaurlaritza) under the program “Ikertzaile ez doktoreen doktoretza-aurreko formakuntza programa” ( PRE_2015_2_0208), CCG was supported by the Spanish Ministry of Economy and Competitiveness through the Juan de la Cierva (IJCI- 2014-20821) and Ramon y Cajal (RYC-2017-21845) Fellowships

Mediterranean diet as the ideal model for preventing non-alcoholic fatty liver disease (NAFLD)

The prevalence of nonalcoholic fatty liver disease (NAFLD) has dramatically increased in the 2–3 last decades and it represents the most frequent global cause of liver disease, affecting 25% to 45% of adults in most studies (1). The worldwide elevation in the population rates of NAFLD has come in parallel with rising unprecedented pandemics of obesity and diabetes. There is no specific medication for NAFLD and dietary/lifestyle modifications are the main foundations for the treatment of NAFLD. They are also very likely to be effective for its primary prevention. In this context, a dietary pattern that meets most requirements to become the ideal model for the prevention of NAFLD is the traditional Mediterranean diet (2). In addition to the potential for preventing NAFLD, the Mediterranean diet has sufficiently demonstrated its great ability to improve cardiovascular health. The accrual of prospective and well conducted studies showing cardiovascular benefits associated with better adherence to a high-quality food pattern is superior for the traditional Mediterranean food pattern than for any other dietary pattern (3)

Myocardial Extracellular Volume Quantification by Cardiovascular Magnetic Resonance and Computed Tomography

PURPOSE OF REVIEW: This review article discusses the evolution of extracellular volume (ECV) quantification using both cardiovascular magnetic resonance (CMR) and computed tomography (CT). RECENT FINDINGS: Visualizing diffuse myocardial fibrosis is challenging and until recently, was restricted to the domain of the pathologist. CMR and CT both use extravascular, extracellular contrast agents, permitting ECV measurement. The evidence base around ECV quantification by CMR is growing rapidly and just starting in CT. In conditions with high ECV (amyloid, oedema and fibrosis), this technique is already being used clinically and as a surrogate endpoint. Non-invasive diffuse fibrosis quantification is also generating new biological insights into key cardiac diseases. CMR and CT can estimate ECV and in turn diffuse myocardial fibrosis, obviating the need for invasive endomyocardial biopsy. CT is an attractive alternative to CMR particularly in those individuals with contraindications to the latter. Further studies are needed, particularly in CT

Changes in brain activity during language learning in adults measured by magnetoencephalography

278 p.The main goal of this thesis was to characterize language-related short-term learning changes in the adult brain. Previous studies have mainly used longitudinal and cross-sectional designs and therefore they captured brain responses of already consolidated rules. On the other hand, studies that used on line or lab training, and therefore captured short-term changes, were conducted in EEG and provided no source correlates related to these changes. However, short-term and long-term learning seem to elicit different plastic changes hence, the anatomical-correlates of the MEG experiments carried out in this thesis would provide useful information to better understand which plastic changes occur in short-term learning. Subsets of natural languages (miniature languages) were used in two of the experiments in order to study short-term changes. It was hypothesized that miniature languages allow to capture language-related changes without the need of course-like long-lasting training. The third experiment was a memory task in participants' native language, and aimed to provide a better understanding of physiological memory functions, especially the role of oscillations in memory retrieval. Therefore, this thesis opens a door to a new way of studying L2 learning, providing anatomical correlates of short-term language related brain changes.Basque Center on Cognition Brain and Languag

Changes in brain activity during language learning in adults measured by magnetoencephalography

278 p.The main goal of this thesis was to characterize language-related short-term learning changes in the adult brain. Previous studies have mainly used longitudinal and cross-sectional designs and therefore they captured brain responses of already consolidated rules. On the other hand, studies that used on line or lab training, and therefore captured short-term changes, were conducted in EEG and provided no source correlates related to these changes. However, short-term and long-term learning seem to elicit different plastic changes hence, the anatomical-correlates of the MEG experiments carried out in this thesis would provide useful information to better understand which plastic changes occur in short-term learning. Subsets of natural languages (miniature languages) were used in two of the experiments in order to study short-term changes. It was hypothesized that miniature languages allow to capture language-related changes without the need of course-like long-lasting training. The third experiment was a memory task in participants' native language, and aimed to provide a better understanding of physiological memory functions, especially the role of oscillations in memory retrieval. Therefore, this thesis opens a door to a new way of studying L2 learning, providing anatomical correlates of short-term language related brain changes.Basque Center on Cognition Brain and Languag

Fijación activa y perforación ventricular: ¿una nueva entidad?

First, a new active fixation lead was implanted in the interventricular septum; the old lead was then extracted with a Cook stylet. The patient’s clinical course was satisfactory and there were no procedure-related complications. In conclusion, within the battery of diagnostic tests available to investigate suspected cardiac perforation, computed angiotomography of the chest is a highly useful complementary technique for the management of this complication

Incidental computed tomography diagnosis of a rare triad consisting of absence of coronary sinus, persistent left superior vena cava, and scimitar syndrome

We report a case of an unusual congenital triad consisting of absence of coronary sinus, persistent left superior vena cava and scimitar syndrome incidentally found in a CT-scan performed on a female complaining of exertional dyspnea

LIVE FUEL MOISTURE CONTENT AND IGNITION PROBABILITY IN THE IBERIAN PENINSULAR TERRITORY OF SPAIN

This paper presents an operational algorithm to produce Live Fuel Moisture Content (LFMC) at national scale from MODIS data. The algorithm is based on the inversion of Radiative Transfer Models (RTM) that estimate moisture content based on different simulation scenarios. In addition, logistic regression models were calibrated to convert the derived LFMC values into Ignition Probability (IP) maps. The areas under the curve obtained by the Receiver Operating Characteristic (ROC) plot method provided by the models were close to 0.6. Several statistical analyses were performed in order to ascertain whether the variables proposed to be included in the fire danger model were significantly related to forest fires. A non parametric U-Mann-Withney test confirmed significant differences between fire and non-fire pixels (p<0.001). Fire pixels occurred at significantly lower LFMC values than the non-fire pixels