238 research outputs found
Managing atrial fibrillation in the very elderly patient: challenges and solutions
No full textNikolaos Karamichalakis, Konstantinos P Letsas, Konstantinos Vlachos, Stamatis Georgopoulos, Athanasios Bakalakos, Michael Efremidis, Antonios Sideris Laboratory of Cardiac Electrophysiology, "Evangelismos" General Hospital of Athens, Athens, Greece Abstract: Atrial fibrillation (AF) is the most common arrhythmia affecting elderly patients. Management and treatment of AF in this rapidly growing population of older patients involve a comprehensive assessment that includes comorbidities, functional, and social status. The cornerstone in therapy of AF is thromboembolic protection. Anticoagulation therapy has evolved, using conventional or newer medications. Percutaneous left atrial appendage closure is a new invasive procedure evolving as an alternative to systematic anticoagulation therapy. Rate or rhythm control leads to relief in symptoms, fewer hospitalizations, and an improvement in quality of life. Invasive methods, such as catheter ablation, are the new frontier of treatment in maintaining an even sinus rhythm in this particular population. Keywords: elderly, atrial fibrillation, anticoagulation, drugs, catheter ablatio
Study of the correlation between structure and magnetism in thin films via synchrotron radiation and conventional laboratory techniques
No full textThis work was performed in part in the conventional laboratories of the Materials Science Department and the Lab of High Tech Materials, University of Patras and in part at the European Synchrotron Radiation Facility (ESRF) Grenoble, France. The target of the Thesis is to correlate structure and magnetism in magnetic thin films.At ESRF polycrystalline and amorphous thin films of similar composition were probed by x-ray magnetic circular dichroism - XMCD. For the first time the induced magnetic moment of Zr in amorphous and crystalline magnetic materials was probed. The same holds for Y in amorphous thin films. The spin and orbital magnetic moment contributions were disentangled. It was found, surprisingly, that when Zr or Y is in crystalline environment, its spin and orbital magnetic moments are antiparallel, but in amorphous samples they become parallel. The latter is an apparent violation of Hund’s third rule in matter. The effect was attributed to changes in coordination number and interatomic distances. Moreover, the induced magnetic moments of Pd and Pt were studied in certain magnetic thin films and a review was done comparing those results to literature in order the mechanisms, which make magnetic thin films and multilayers with Pd and Pt important in magneto-optical recording, to be elucidated.At lab the main target was to correlate texture and magnetic anisotropy in Co- and Ni-based thin films with fcc structure. Magnetic hysteresis loops were recorded with the field in- and out-of plane with a Kerr magnetometer at room temperature. It was demonstrated that combination of residual strain (stress) with certain texture can give rise to perpendicular magnetic anisotropy in magnetic thin films. Perpendicular anisotropy is crucial for nanodevices and magneto-optical hard discs of computers. When perpendicular anisotropy appears, then one may record impressive images of magnetic domains by magnetic force microsopy. After all, the mechanism of correlation between structure-texture and magnetic anisotropy in polycrystalline systems was elucidated.Στα πλαίσια της διδακτορικής αυτής διατριβής μελετήθηκε η σχέση δομής και μαγνητισμού σε λεπτά μαγνητικά υμένια. Ένα μέρος της διατριβής έγινε στο εργαστήριο και ένα στο European Synchrotron Radiation Facility. Στο Σύγχροτρον μελετήθηκαν με την τεχνική του κυκλικού μαγνητικού διχρωϊσμού ακτίνων Χ (x-ray magnetic circular dichroism – XMCD) άμορφα και κρυσταλλικά υμένια με παρόμοια σύνθεση. Αφενός, για πρώτη φορά μετρήθηκε η επαγόμενη μαγνητική ροπή στο ζιρκόνιο και το ύττριο σε άμορφα και κρυσταλλικά μαγνητικά υμένια και διαχωρίστηκαν οι μαγνητικές ροπές σπιν και τροχιάς. Αφετέρου, βρέθηκε το εντυπωσιακό φαινόμενο της αλλαγής του σχετικού προσανατολισμού της μαγνητικής ροπής σπιν και τροχιάς, οι οποίες από αντιπαράλληλες στα κρυσταλλικά υμένια γίνονται παράλληλες στα άμορφα. Έγινε κατανοητό πως κάτι τέτοιο οφείλεται στη διαφορά στον αριθμό πρώτων γειτόνων και στις ενδοατομικές αποστάσεις. Ο παράλληλος προσανατολισμός των μαγνητικών ροπών σπιν και τροχιάς σε στοιχεία με λιγότερο από μισογεμάτη ζώνη d αποτελεί μια διαφαινόμενη παραβίαση του τρίτου κανόνα του Hund στην ύλη. Τέλος, έγινε μελέτη ορισμένων μαγνητικών υμενίων με παλλάδιο και πλατίνα, υμένια με ενδιαφέρον στη μαγνητική και μαγνητο-οπτική εγγραφή πληροφορίας, ώστε να κατανοηθούν καλύτερα οι μηχανισμοί που τα καθιστούν ενδιαφέροντα τεχνολογικά.Επίσης, κύρια στο εργαστήριο, μελετήθηκε η σχέση υφής και μαγνητικής ανισοτροπίας σε υμένια με βάση το κοβάλτιο και το νικέλιο σε fcc δομή. Kαταγράφηκαν βρόχοι μαγνητικής υστέρησης με ένα Kerr μαγνητόμετρο σε θερμοκρασία δωματίου. Έγινε φανερό πως οι παραμένουσες τάσεις σε συνδυασμό με την κατάλληλη υφή μπορεί να οδηγήσουν στην εμφάνιση κάθετης ανισοτροπίας σε πολυκρυσταλλικά υμένια. Η κάθετη μαγνητική ανισοτροπία είναι μια ιδιότητα με μεγάλη σημασία στην τεχνολογική αξιοποίηση των μαγνητικών υμενίων σε νανοδιατάξεις και μαγνητο-οπτικούς δίσκους,. Στην περίπτωση αυτή εντυπωσιακές εικόνες μαγνητικών περιοχών με σπιν πάνω και κάτω σε σχέση με το επίπεδο του υμενίου καταγράφηκαν με το μικροσκόπιο σάρωσης ακίδας. Έγινε εμβάθυνση στα φαινόμενα σχέσης μαγνητισμού και υφής σε πολυκρυσταλλικά συστήματα
Multidimensional Motivational Climate Questionnaire in Physical Education at the Situational Level of Generality (MUMOC-PES)
No full textThe main aim of this study was to investigate the construct validity of a new MUltidimensional MOtivational Climate questionnaire in Physical Education (PE) at the Situational level of generality (MUMOC-PES), capturing four dimensions of empowering (autonomy support, task-involvement, relatedness support, structure) and three dimensions of disempowering (controlling, relatedness thwarting, ego-involvement) climate. Nine hundred and fifty-six adolescent students completed the new measure alongside measures of mastery and performance approach/avoidance climate and satisfaction. Confirmatory factor analysis supported the construct validity of the MUMOC-PES. Student satisfaction in PE corresponded positively to empowering and negatively to disempowering climate dimensions. Controlling for age, gender and within-class individual differences in perceived empowering and disempowering dimensions, class average scores on perceived empowering climate had significant effects on student satisfaction, implying predictive validity for the MUMOC-PES. Structural Equation Modeling (SEM) suggested that perceived autonomy support and relatedness thwarting had direct positive and negative effects on satisfaction respectively. Moreover, effects of perceived structure and thwarting relationships on satisfaction were mediated through a mastery climate construct capturing the linkage between perception and mastery goal. The results are discussed in relation to existing measures and literature on motivational climate and the future use of MUMOC-PES in research and PE teachers’ training
Evaluation of Crop Water Requirements estimated from Sentinel 2 MSI and Landsat 8 OLI Earth Observation data in MOSES DSS
No full textMOSES DSS web-platform aims to assist stakeholders such as governments and farmers in order to manage water irrigation distribution in a higher efficiency and sustainability. The constructed algorithms are focused on forecast using weather models, data, as well as satellite multispectral observations in such a way that a 7-day ahead crop water requirement estimation is generated. The current drawback of the system in using the available and free satellite products such as Landsat 8 and Sentinel 2, is that it assumes that the crops are under standard conditions, e.g. there is no water stress, diseases etc.. The current work investigates how possible errors due to this assumption can be potentially tackled in the future by comparing Crop Water Requirement (CWR) with S2REP VI and/or with water stress index and see the discriminative power of the latter. Furthermore, a comparison between several discrepancies between S2 and L8 (e.g. AC and co-registration) are studied since it is a crucial issue especially in temporal applications such as MOSES. On the one hand, the results showed that a harmonization of the two products is certainly needed. On the other hand, it seems that S2REP is capable of revealing crop stress information based on the methodologies of this work, thus it could potentially give more information compared to NDVI which is not sensitive to crop stress.MOSES projec
Investigation of meso-scale Sentinel-3 product along-track correlations and the potential of inter-track SSHA estimation using machine learning
No full textSatellite altimetry is an important technology used to measure sea level with high spatial and temporal resolution. Sentinel-3, a Copernicus satellite mission, offers three types of variables captured simultaneously for the first time; sea level (SSH), sea surface temperature (SST) and ocean colour (OC) variables. Sea level is measured with SAR altimetry, a technique that considerably increases spatial resolution compared to other means of observation. Altimetry measures sea level across a line that coincides with the satellite ground track, whereas SST and OC are measured on a grid. What we lack are sea level observations in-between ground tracks that would better resolve meso-scale variability. This thesis is focused on two objectives, considering previous work that has indicated associations between those variables. The first objective was to investigate the correlations among SSH, SST and OC, while the second objective was to assess to what extent inter-track sea level can be estimated using SST and OC as predictors in machine learning algorithms. Daily Sentinel-3 data over a period of eleven months were pre-processed and brought into a form that allowed for computation of metrics such as auto- and cross-correlations in the along-track direction. The focus was on the spatial scales that would enable to detect meso-scale features, such as eddies. With respect to the inter-track sea level estimation two paths were followed. In the first path, Random Forest (RF) and Multilayer Perceptron (MLP) were applied using the complete 11-month dataset as input. Moreover, RF was applied on input data that belong to each separate day. In the second path, 1D Convolutional Neural Network (CNN) was used on the complete 11-month dataset, which inherently honors the spatial dependency of the variables in contrast to the first path. Generally, the correlations between the variables were found to exist in the meso-scale but were not always strong and they depend on several other factors, such as meteorological conditions, scales included in the analysis and techniques used. All three techniques -RF, MLP and 1D CNN- that were applied on the complete 11-month dataset gave poor results. On the contrary, when RF was applied on the per-day data gave promising results that are reliable mostly in the vicinity of the ground track, although they are not based on one single global model. The results from this project suggest that there must be more research on the correlation analysis of Sentinel-3 data. It can be improved by using additional or similar techniques, such as localized cross-correlation metrics on various spatial scales. With respect to the inter-track sea level estimation, far more investigation is needed. However, there are indications that a machine learning data-driven approach could potentially work to some extent. Sentinel-3 data will become more abundant in the next years which will assist data science algorithms such as CNNs which require huge datasets.Geoscience and Remote Sensin
Risk factors for severe perineal lacerations during childbirth
No full textBackground: Severe perineal lacerations represent a significant complication of normal labor with a strong impact on quality of life. Objectives: To identify factors that lead to the occurrence of severe perineal lacerations. Search strategy: We searched MEDLINE, Scopus, ClinicalTrials.gov, the Cochrane Central Register of Controlled Trials, Google Scholar and reference lists from all included studies. Selection criteria: We included prospective and retrospective observational studies. Data collection and analysis: Predetermined data were collected and analyzed with the Mantel-Haenszel fixed-effects model or the DerSimonian-Laird random-effects model. Main results: The meta-analysis included 22 studies (n = 651 934). Women with severe perineal tears were more likely to have had heavier infants (mean difference 192.88 g [95% CI, 139.80-245.96 g]), an episiotomy (OR 3.82 [95% CI, 1.96-7.42]), or an operative vaginal delivery (OR 5.10 [95% CI, 3.33-7.83]). Epidural anesthesia (OR 1.95 [95% CI, 1.63-2.32]), labor induction (OR 1.08 [95% CI, 1.02-1.14]), and labor augmentation (OR 1.95 [95% CI, 1.56-2.44]) were also more common among women with perineal lacerations. Conclusions: Various factors contribute to the occurrence of perineal lacerations. Future studies should consistently evaluate all examined parameters to determine their possible interrelation. (C) 2014 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved
Everyone can learn from Rita’s story
Get PDFThis is a comment made in relation to the contribution of migrants to the UK. The author suggests that the experiences of high-profile immigrants in the field of entertainment must not overshadow the contribution of the many more numerous everyday working migrants. The author also reminds the readership that migration is a two-way process, with millions of British and Irish emigrants all around the world. The topic is of political importance given the on-going debates and still unknown long term effects of Brexit (the UK’s departure from the European Union)
Multi-Camera Plenoptic Particle Image Velocimetry
No full textRecently, plenoptic or lightfield cameras have been proposed for performing single camera three-dimensional fluid velocity field measurement due to their unique nature of recording both the spatial variation and the propagation direction of the incoming light. The combination of both the spatial and angular information of the light yields the lightfield function, which in turn can be used to create three-dimensional reconstructions. Unfortunately single camera plenoptic PIV measurements suffer from the same low angular resolution problems as do the single camera defocusing PIV and holographic PIV techniques. To increase the quality of the volumetric reconstructions a multiplicative, multiple plenoptic camera reconstruction algorithm is derived and it is shown in lightray simulations that using multiple plenoptic cameras can produce three-dimensional intensity fields with much higher fidelity to the true field than the reconstructions produced by a single camera. Moreover, the intensity fields produced using multiple plenoptic cameras have comparable or higher fidelity than those produced using tomographic PIV techniques with the same number and orientation of cameras
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