Το τραύμα της πανώλης στο ύστερο Βυζάντιο

Σύμφωνα με την Αμερικανική Ψυχολογική Εταιρεία, ως τραύμα ορίζεται ο τρόπος με τον οποίο αντιδρά κανείς συναισθηματικά απέναντι σε μία υπερβολικά δυσάρεστη ε-μπειρία. Το φαινόμενο αυτό όμως, μπορεί να λάβει και συλλογικές διαστάσεις, καθώς και μία ομάδα μπορεί να βιώσει ένα κοινό τραύμα. Με την έλευση του Μαύρου Θανά-του το 1347, οι κοινότητες της Ευρώπης που υπέστησαν τα απανωτά πλήγματά της, ανταποκρίθηκαν με ποικίλους τρόπους στην τραυματική εμπειρία της καταστροφής που προκάλεσε. Οι πηγές περιγράφουν μία ανείπωτη και πολύνεκρη καταστροφή, που κατέστησε την ζωή πιο εύθραυστη και αβέβαιη από ποτέ. Παράλληλα, το βίωμα της πανώλης και οι συνέπειές της αποτέλεσαν πηγή έμπνευσης για νέες ταφικές πρακτικές, καλλιτεχνικές θεματικές και νέες θεωρήσεις για την ζωή και τον θάνατο. Η πανώλη ωστόσο, είχε ήδη πλήξει αιώνες νωρίτερα το Βυζάντιο και πιο συγκεκριμένα, το 541. Ο Προκόπιος και ο Ιωάννης Εφέσου, μας παρέχουν τις πιο δραματικές περιγραφές της πανωλεθρίας που έφερε η πανώλη στην Βασιλεία των Ρωμαίων. Η Κωνσταντινούπο-λη είχε γεμίσει με τόσους νεκρούς που δεν έφταναν οι τάφοι, ενώ παράλληλα η ύπαι-θρος ήταν γεμάτη με άδεια χωριά, οι κάτοικοι των οποίων κείτονταν νεκροί, πρησμέ-νοι από την αποσύνθεση. Επιπλέον, ο Ιωάννης Εφέσου περιγράφει πως κάθε βράδυ φοβόταν ότι το επόμενο πρωί δεν θα ξυπνούσε, διότι η πανώλη θα του είχε πάρει τη ζωή. Όταν όμως ο Μαύρος Θάνατος έπληξε το Βυζάντιο το 1347, οι Ρωμαίοι δεν α-ντέδρασαν με τρόπο όμοιο με αυτόν των συγχρόνων τους, αλλά ούτε και με αυτόν των προγόνων τους. Αντίθετα, το στίγμα της πανώλης φαίνεται να απουσιάζει παντελώς και οι πηγές επιδεικνύουν πλήρη αδιαφορία στην εξιστόρηση των επιδημικών ξεσπα-σμάτων. Η αδιαφορία αυτή μάλιστα, φτάνει σε τέτοια επίπεδα, που η παράλειψη των επιδημικών ξεσπασμάτων από τις πηγές αποτελεί συχνό φαινόμενο. Συνεπώς, σχημα-τίζεται μία εντύπωση που θέλει την δράση της πανώλης να ήταν σχεδόν ανύπαρκτη. Στόχος της παρούσας μεταπτυχιακής διπλωματικής εργασίας, είναι η απόδειξη της ύ-παρξης του τραύματος της πανώλης στο ύστερο Βυζάντιο. Αυτό θα επιτευχθεί μέσω του εντοπισμού όσο το δυνατόν περισσότερων στοιχείων στις πηγές της εποχής, που θα μαρτυρούν το στίγμα της πανώλης στον ψυχισμό της βυζαντινής κοινωνίας. Πέραν του εντοπισμού των ενδείξεων αυτών, κύριος στόχος της εργασίας αποτελεί η σύγκρι-ση των διαφόρων εκδηλώσεων του φαινομένου, με αντίστοιχα παραδείγματα από την δυτική Ευρώπη του 14ου και 15ου αιώνα, αλλά και από το πρώιμο Βυζάντιο.According to the American Psychological Association, trauma is an emotional re-sponse to a terrible event. This phenomenon however may exist to a collective level, a collective of people as well can experience a shared trauma. When the Black Death arrived in Europe in 1347, the various societies that got afflicted repeatedly, reacted in a variety of ways to the traumatic experience of the calamities it caused. Sources of that era, give us descriptions of an unspeakable and deadly disaster which rendered life frailer and more uncertain than ever. Meanwhile, living in the time of plague and the various consequences that the disease caused, worked as a source of inspiration for new burial practices, creative themes and views on life and death. The plague made its first appearance in the Byzantine Empire centuries earlier, in the year 541. Procopius and John of Ephesus give us the most dramatic accounts on the disaster the plague caused to the Byzantine Empire. The death toll was so high in Constantinople, that there was not enough space to bury the dead, while at the same time the countryside included many deserted villages, whose inhabitants were lying dead on the streets, bloated and in a partial state of decomposition. Furthermore, John of Ephesus narrates that every night, he was scared to fall asleep for he feared that the plague would kill him. However, when the Black Death struck Byzantium in 1347, the people acted in a manner dissimilar to that of both their contemporaries and their ancestors. The scars left by the plague are absent and the sources of the era show a total lack of interest into recording the various plague outbreaks. This lack of motivation goes to such ex-tremes, that the exclusion of the plague outbreaks is a common theme in the sources of that era. As a result, an impression is given according to which the plague’s conse-quences were nonexistent. The main goal of the current thesis is to prove the existence of plague trauma in the late Byzantine Empire. That goal shall be achieved through the tracking of as much evidence in the sources as possible, that indicate the existence of any consequences of the plague to the byzantine psyche. In addition to that, this thesis aims to compare examples of the phenomenon to similar ones from Western Europe of the 14th and 15th centuries and from the early Byzantine period

Joint Meeting of the Greek and Italian Sections of The Combustion Institute 1

ABSTRACT The effect of a secondary "weak" jet on a "strong" jet's flow field is of great importance for the evaluation of many staged combustion schemes. The present work is part of ongoing research on turbulent mixing characteristics of the interaction of a weak and a strong jet inside a confining area, with experimental and numerical tools. Preliminary experimental results, obtained with laser Doppler anemometry, will be presented. Measurements of mean and turbulent velocity statistics of a single turbulent axisymmetric jet are presented for reference. At a distance of thirty strong jet's diameters, mean and rms velocity profiles of jets' merging are presented for isothermal conditions. In this test case momentum flux ratio of jets is rather high. Two local maximums corresponding to the central region of each jet are identified. A slight displacement of weak jet's maximum and a small increase of turbulent components at the edges of jets indicate early stages of mixing

The Risk of Getting Worse: Predictors of Deterioration After Decompressive Surgery for Lumbar Spinal Stenosis: A Multicenter Observational Study

ObjectiveTo investigate the frequency and predictors of deterioration after decompressive surgery for single and 2-level lumbar spinal stenosis.MethodsProspectively collected data were retrieved from the Norwegian Registry for Spine Surgery. Clinically significant deterioration was defined as an 8-point increase in Oswestry disability index (ODI) between baseline and 12 months' follow-up.ResultsThere were 2181 patients enrolled in the study. Of 1735 patients with complete 12 months follow-up, 151 (8.7%) patients reported deterioration. The following variables were significantly associated with deterioration at 12 months' follow-up; decreasing age (odds ratio [OR] 1.02, 95% confidence interval [95% CI] 1.00–1.04, P = 0.046), tobacco smoking (OR 2.10, 95% CI 1.42–3.22, P = 0.000), American Society of Anesthesiologists grade ≥3 (OR 1.80, 95% CI 1.07–2.94, P = 0.025), decreasing preoperative ODI (OR 1.05, 95% CI 1.02–1.07, P = 0.000), previous surgery at the same level (OR 2.00, 95% CI 1.18–3.27, P = 0.009), and previous surgery at other lumbar levels (OR 2.10, 95% CI 1.19–3.53, P = 0.009).ConclusionsOverall risk of clinically significant deterioration in patient-reported pain and disability after decompressive surgery for lumbar spinal stenosis is approximately 9%. Predictors for deterioration are decreasing age, current tobacco smoking, American Society of Anesthesiologists grade ≥3, decreasing preoperative ODI, and previous surgery at same or different lumbar level. We suggest that these predictors should be emphasized and discussed with the patients before surgery

General method for prediction of thermal conductivity for well-characterized hydrocarbon mixtures and fuels up to extreme conditions using entropy scaling

A general and efficient technique is developed to predict the thermal conductivity of well-characterized hydrocarbon mixtures, rocket propellant (RP) fuels, and jet fuels up to high temperatures and high pressures (HTHP). The technique is based upon entropy scaling using the group contribution method coupled with the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state. The mixture number averaged molecular weight and hydrogen to carbon ratio are used to define a single pseudo-component to represent the compounds in a well-characterized hydrocarbon mixture or fuel. With these two input parameters, thermal conductivity predictions are less accurate when the mixture contains significant amounts of iso-alkanes, but the predictions improve when a single thermal conductivity data point at a reference condition is used to fit one model parameter. For eleven binary mixtures and three ternary mixtures at conditions from 288 to 360 K and up to 4,500 bar, thermal conductivities are predicted with mean absolute percent deviations (MAPDs) of 16.0 and 3.0% using the two-parameter and three-parameter models, respectively. Thermal conductivities are predicted for three RP fuels and three jet fuels at conditions from 293 to 598 K and up to 700 bar with MAPDs of 14.3 and 2.0% using the two-parameter and three-parameter models, respectively

On the formation of string cavitation inside fuel injectors

The formation of vortex or ‘string’ cavitation has been visualised in the flow upstream of the injection hole inlet of an automotive-sized optical diesel fuel injector nozzle operating at pressures up to 2,000 bar. Three different nozzle geometries and three-dimensional flow simulations have been employed to describe how, for two adjacent nozzle holes, their relative positions influenced the formation and hole-to-hole interaction of the observed string cavitation vortices. Each hole was shown to contain two counter-rotating vortices: the first extending upstream on axis with the nozzle hole into the nozzle sac volume and the second forming a single ‘bridging’ string linked to the adjacent hole. Steady-state and transient fuel injection conditions were shown to produce significantly different nozzle-flow characteristics with regard to the formation and interaction of these vortices in the geometries tested, with good agreement between the experimental and simulation results being achieved. The study further confirms that the visualised vortices do not cavitate themselves but act as carriers of gas-phase components within the injector flow

Cloud cavitation vortex shedding inside an injector nozzle

The development and collapse of cloud cavitation and its link to surface erosion within a transparent test single-orifice nozzle operating with a closed Diesel fuel hydraulic circuit, has been characterized using high-speed imaging. Data have been obtained for a range of cavitation and Reynolds numbers under fixed lift positions. Post processing of a large number of images acquired with short exposure time (1 μs) allowed the elucidation of the distinct flow phenomena associated with the highly transient two-phase flow. At the inlet of the flow orifice, the vapour cloud was found to occupy the largest part of the nozzle hole cross-section. Coherent vortical structures of a hairpin shape have been detected to onset at the closure region of this vapour cloud and shed downstream in a fully transient manner. The effect of the operating parameters on the temporal and spatial characteristics with regards to the emergence and collapse of the hairpin vortices has been quantified. It has been established that the cavitation-vortex shedding was taking place in a periodical manner, characterized by a Strouhal number