Spatial Event Detection in Twitter: A Comparison of State-of-the-Art Techniques

Κατά την διάρκεια της τελευταίας δεκαετίας, οι πλατφόρμες κοινωνικής δικτύωσης όπως το Twitter έχουν αναπτυχθεί και ωριμάσει, με αποτέλεσμα τεράστιο πλήθος δεδομένων να δημιουργείται σε πραγματικό χρόνο. Οι χρήστες αυτών των δικτύων, μεταφορτώνουν συνεχώς δεδομένα σχετικά με την κατάσταση του περιβάλλον τους. Αυτή η πλούσια συλλογή δεδομένων μπορεί να χρησιμοποιηθεί για να προσφέρει ανάδραση πραγματικού χρόνου για ενεργά γεγονότα, η οποία μπορεί να αξιοποιηθεί με ποικίλους τρόπους. Σε αυτήν την πτυχιακή εργασία, δοκιμάζουμε δύο συστήματα, ανίχνευσης γεγονότων στοχευμένου τομέα, ένα εκ των οποίων είναι με επίβλεψη, και το άλλο είναι χωρίς. Αυτά τα συστήματα ανίχνευσης γεγονότων, επεξεργάζονται μια συλλογή από χρονικά ταξινομημένα δεδομένα και εκτελούν την διαδικασία της ανίχνευσης γεγονότων ως μια σωλήνωση τριών διακριτών βημάτων, αυτό του φιλτραρίσματος, της χωρικής συσταδοποίησης και της βαθμολόγησης. Στο βήμα του φιλτραρίσματος, τα tweets, έπειτα από επεξεργασία, χωρίζονται σε δύο κατηγορίες, αυτά που είναι συναφή με τον τομέα, και αυτά που δεν είναι. Το επόμενο βήμα της διαδικασίας είναι η χωρική συσταδοποίηση των συναφών tweets σε συναφής περιοχές. Στο τελικό στάδιο της διαδικασίας, οι περιοχές οι οποίες είχαν εξορυχθεί κατά την διαδικασία της χωρικής συσταδοποίησης, ταξινομούνται με τέτοιο τρόπο, ώστε οι περιοχές οι οποίες είχαν επηρεαστεί περισσότερο από το γεγονός, να βαθμολογούνται υψηλότερα. Πιο συγκεκριμένα, το σύστημα με επίβλεψη, απαιτεί ανθρώπινη εργασία και έναν απλό αλγόριθμο για το φιλτράρισμα των tweets. Σε αντίθεση, το σύστημα χωρίς επίβλεψη υιοθετεί έναν αλγόριθμο χωρίς επίβλεψη για αυτήν την διαδικασία. Και τα δύο συστήματα συσταδοποιούν τα συναφή tweets, είτε με τον αλγόριθμο k-Means, είτε με έναν αλγόριθμο συσταδοποίησης γράφων με την χρήση της μετρικής modularity. Τέλος, αυτά τα συστήματα ταξινομούν τις συστάδες με βάση κάποιες στρατηγικές βαθμολόγησης. Κατά την διάρκεια των πειραμάτων μας, κατέστη σαφές πως το σύστημα χωρίς επίβλεψη, είχε χειρότερα αποτελέσματα από το σύστημα με επίβλεψη, αλλά δεν απαιτεί χρόνο για τον χαρακτηρισμό των δεδομένων, και με αυτόν τον τρόπο προσφέρει έναν καλό συμβιβασμό μεταξύ ανθρώπινης εργασίας και ακρίβειας των αποτελεσμάτων.During the last decade, social media platforms such as Twitter have grown and matured to a point where enormous amounts of data are being generated in real-time fashion. Users of these networks are constantly uploading information about the current state of their surroundings. This wealth of information can be exploited in order to provide meaningful real-time feedback about ongoing events for a wide range of applications. In this thesis, we test two targeted domain, event detection systems; one that is supervised and one that is not. These event detection systems, process a collection of time-indexed data and perform the detection procedure as a pipeline of three discrete steps, a filtering phase, a spatial clustering phase, and a scoring phase. In the filtering phase, the tweets get processed, and they are divided into two categories, those that are related to the targeted domain and those that are not. The next step of the process is the spatial clustering, which aggregates the related tweets into areas of interest. As the last part of the process, the regions that were extracted by the clustering phase, are sorted, by ranking higher those regions that were mostly affected by the event. More specifically, the supervised system, requires human labor and a simple algorithm for filtering the tweets. By contrast, the unsupervised system employs an unsupervised algorithm for this process. Both systems cluster the related tweets, either with the k-Means algorithm, or with a modularity based graph clustering algorithm. Finally these systems rank the resulting clusters with the help of several ranking schemes. During our experiments, it became clear that the unsupervised system provides worse results than the supervised approach, but it does not require time for labeling the data, and thus it provides a good trade-off between human labor and accuracy of the results

Acute seizures in acute ischemic stroke: does thrombolysis have a role to play?

Seizures appear at stroke presentation, during the acute phase or as a late complication of stroke. Thrombolysis has not been investigated as a risk factor despite its potential neurotoxic effect. We try to identify risk factors for seizures during the acute phase of ischemic stroke in a cohort including thrombolysed patients. We undertook a case-control study at a single stroke center using data from Acute Stroke Registry and Analyse of Lausanne (ASTRAL). Patients with seizure occurring during the first 7days following stroke were retrospectively identified. Bi-variable and multivariable statistical analyses were applied to compare cases and randomly selected controls. We identified 28 patients experiencing from seizures in 2,327 acute ischemic strokes (1.2%). All seizures occurred during the first 72h. Cortical involvement, thrombolysis with rt-PA, arterial recanalization, and higher initial NIHSS were statistically associated with seizures in univariated analysis. Backward linear regression identified cortical involvement (OR 7.53, 95% CI 1.6-35.2, p<0.01) and thrombolysis (OR 4.6, 95% CI 1.6-13.4, p=0.01) as being independently associated with seizure occurrence. Overall, 3-month outcome measured by the modified Rankin scale (mRS) was comparable in both groups. In the subgroup of thrombolysed patients, outcome was significantly worse at 3months in the seizure group with 9/12 (75%) patients with mRS ≥3, compared to 6/18 (33.3%) in the seizure-free group (p=0.03). Acute seizures in acute ischemic stroke were relatively infrequent. Cortical involvement and thrombolysis with rt-PA are the principal risk factors. Seizures have a potential negative influence on clinical outcome in thrombolysed patient

THE PSYCHOLOGICAL AND SOCIO-ECONOMIC IMPACTS OF FESTIVAL CELEBRATIONS ON THE ISLAND OF RHODES, GREECE, DURING THE COVID-19 PANDEMIC

This research paper aims to study the function of the traditional festivals on the island of Rhodes during the period of the COVID-19 pandemic in order to explore community members and official institution representatives’ views on their psychological and socio-economic consequences. A structured interview was designed, which was given online to 168 subjects, of which 96 community members in the villages of the island of Rhodes and to 72 official institutions, representatives of cultural and local authorities, within the context of the beginning of the festivities with some restrictions, in August 2021, in the light of the pandemic. The results of the research show that the majority of community members and official institution representatives of the sample emphasize the communicative, cultural, recreational, and social dimensions of the festivals, however, some claim that there are no longer events that arise interest. Regarding their cancellation during the pandemic period, the majority of community members answer that the entertainment - communication sector was most affected, while the representatives of the institutions emphasize the economic consequences. In general, regarding the consequences of the pandemic on the behavior and psychology of individuals, introversion, isolation, antisociality, belligerence, tension and nervousness, are emphasized, while mistrust seems to prevail even in close family settings. Moreover, the majority of community members and representatives emphasize that social offer and solidarity are not exhibited to a satisfactory degree, while volunteering activities are limited. Regarding the pandemic, vaccination is suggested as the most effective means, mainly by the official institution representatives. Regarding the events of 2021 that shocked them most, the community members focus on economic, social and psychological - personal problems, while the official institution representatives focus on environmental and economic problems. Finally, most of them state that they do not want the transformation of festivals, however, they regard the emphasis on tradition as a sustainable perspective of local festivals.  Article visualizations

European Stroke Organisation (ESO) Guidelines for the Management of Temperature in Patients with Acute Ischemic Stroke

Background Hyperthermia is a frequent complication in patients with acute ischemic stroke. On the other hand, therapeutically induced hypothermia has shown promising potential in animal models of focal cerebral ischemia. This Guideline Document presents the European Stroke Organisation guidelines for the management of temperature in patients with acute ischemic stroke. Methods A multidisciplinary group identified related questions and developed its recommendations based on evidence from randomized controlled trials elaborating the Grading of Recommendations Assessment, Development, and Evaluation approach. This Guideline Document was reviewed within the European Stroke Organisation and externally and was approved by the European Stroke Organisation Guidelines Committee and the European Stroke Organisation Executive Committee. Results We found low-quality evidence, and therefore, we cannot make any recommendation for treating hyperthermia as a means to improve functional outcome and/or survival in patients with acute ischemic stroke and hyperthermia; moderate evidence to suggest against routine prevention of hyperthermia with antipyretics as a means to improve functional outcome and/or survival in patients with acute ischemic stroke and normothermia; very low-quality evidence to suggest against routine induction of hypothermia as a means to improve functional outcome and/or survival in patients with acute ischemic stroke. Conclusions The currently available data about the management of temperature in patients with acute ischemic stroke are limited, and the strengths of the recommendations are therefore weak. We call for new randomized controlled trials as well as recruitment of eligible patients to ongoing randomized controlled trials to allow for better-informed recommendations in the future

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

BACKGROUND: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. METHODS: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). FINDINGS: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29-146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0- 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25-1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39-1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65-1·60]; p=0·92). INTERPRETATION: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention. FUNDING: British Heart Foundation