ΠΡΟΣΟΜΟΙΩΣΗ ΚΑΤΑΚΟΡΥΦΩΝ ΑΝΩΣΤΙΚΩΝ ΦΛΕΒΩΝ ΑΠΟ ΓΡΑΜΜΙΚΟ ΔΙΑΧΥΤΗ

Στην παρούσα εργασία γίνεται αριθμητική προσομοίωση των μέσων ιδιοτήτων κατακορύφων τυρβωδών ανωστικών φλεβών από γραμμικό διαχύτη με ένα, δύο, τρία ή πέντε ακροφύσια από τα οποία εκβάλλει πόσιμο ύδωρ σε υδάτινο ήρεμο περιβάλλον αλμυρού ύδατος. Οι αριθμητικές προσομοιώσεις πραγματοποιήθηκαν με το λογισμικό ANSYS FLUENT CFD (version R.3). Τα αποτελέσματα που προκύπτουν από την προσομοίωση συγκρίνονται με αντίστοιχα της ολοκληρωματικής μεθόδου για κυκλικές τυρβώδεις ανωστικές φλέβες και παρουσιάζουν αρκετά καλή συμφωνία. Η μοντελοποίηση έγινε σε τρεις διαστάσεις, χρησιμοποιώντας είτε το μοντέλο τύρβης Spalart-Allmaras είτε  το k-ω. Από την σύγκριση των αποτελεσμάτων μεταξύ των μεθόδων συμπεραίνεται η ικανοποιητική ακρίβεια των παραδοχών της ολοκληρωματικής μεθόδου και η καλύτερη συμπεριφορά του Spalart-Allmaras σε ροές πλουμίων

On the origin of the λ\lambda-transition in liquid Sulphur

Developing a novel experimental technique, we applied photon correlation spectroscopy using infrared radiation in liquid Sulphur around $T_\lambda$, i.e. in the temperature range where an abrupt increase in viscosity by four orders of magnitude is observed upon heating within few degrees. This allowed us - overcoming photo-induced and absorption effects at visible wavelengths - to reveal a chain relaxation process with characteristic time in the ms range. These results do rehabilitate the validity of the Maxwell relation in Sulphur from an apparent failure, allowing rationalizing the mechanical and thermodynamic behavior of this system within a viscoelastic scenario.Comment: 5 pages, 4 eps figures, accepted in Phys. Rev. Let

Preoperative paroxysmal atrial fibrillation predicts high cardiovascular mortality in patients undergoing surgical aortic valve replacement with a bioprosthesis: CAREAVR study

Background Preoperative permanent atrial fibrillation (AF) is associated with impaired outcome after surgical aortic valve replacement (SAVR). The impact of preoperative paroxysmal AF, however, has remained elusive. Purpose We assessed the impact of preoperative paroxysmal AF on outcome in patients undergoing SAVR with bioprosthesis. Methods A total of 666 patients undergoing isolated AVR with a bioprosthesis were included. Survival data was obtained from the national registry Statistics Finland. Patients were divided into three groups according to the preoperative rhythm: sinus rhythm (n = 502), paroxysmal AF (n = 90), and permanent AF (n = 74). Results Patients in the sinus rhythm and paroxysmal AF groups did not differ with respect to age (P = .484), gender (P = .402) or CHA(2)DS(2)-VASc score (P = .333). At 12-month follow-up, AF was present in 6.2% of sinus rhythm patients and in 42.4% of paroxysmal AF patients (P <.001). During follow-up, incidence of fatal strokes in the paroxysmal AF group was higher compared to sinus rhythm group (1.9 vs 0.4 per 100 patient-years, HR 4.4 95% Cl 1.8-11.0, P = .001). Cardiovascular mortality was higher in the paroxysmal AF group than in the sinus rhythm group (5.0 vs 3.0 per 100 patient-years, HR 1.70 95% CI 1.05-2.76, P = .03) and equal to patients in the permanent AF (5.0 per 100 patient-years). Conclusion Patients undergoing SAVR with bioprosthesis and history of paroxysmal AF had higher risk of developing permanent AF, cardiovascular mortality and incidence of fatal strokes compared to patients with preoperative sinus rhythm. Life-long anticoagulation should be considered in patients with a history of preoperative paroxysmal AF.Peer reviewe

Late incidence and recurrence of new-onset atrial fibrillation after isolated surgical aortic valve replacement

Publisher Copyright: © 2021 The AuthorsObjectives: Atrial fibrillation (AF) is a common complication after cardiac surgery. More knowledge is needed about long-term AF recurrence and adverse outcomes related to new-onset AF (NOAF) during the index hospitalization. Methods: A total of 1073 patients underwent isolated surgical aortic valve replacement at the 4 participating hospitals (2002-2014). After the exclusion of patients with a history of any preoperative AF, the final study population included 529 patients in the bioprosthetic and 253 patients in the mechanical valve prosthesis cohort. Median follow-up time was 5.4 (interquartile range, 3.4-8.2) years in the combined cohort. Results: Altogether 333 (42.6%) patients had in-hospital NOAF and 250 (32.0%) AF after hospital discharge. In the mechanical cohort, 64 (25.3%) experienced in-hospital NOAF and 74 (29.2%) AF after hospital discharge, whereas in the bioprosthetic cohort, 269 (50.9%) patients had in-hospital NOAF and 176 (33.3%) AF after hospital discharge. Patients with NOAF during the index hospital stay had a multifold risk of AF after hospital discharge in the combined cohort (hazard ratio [HR], 3.68; 95% confidence interval [CI], 2.82-4.81; P <.0001) as well as in both cohorts separately (bioprosthetic: HR, 4.35; 95% CI, 3.05-6.22; P <.001; mechanical: HR, 2.54; 95% CI, 1.59-4.03; P <.001). Patients with an in-hospital NOAF also had a significantly higher adjusted risk of death during the follow-up in the mechanical (HR, 2.05; 95% CI, 1.10-3.82; P =.025) and bioprosthetic (HR, 1.63; 95% CI, 1.17-2.28; P =.004) valve prosthesis cohorts. Conclusions: NOAF during the index hospitalization is associated with a 2- to 4-fold risk of later AF and 1.6- to 2.0-fold risk of all-cause mortality after mechanical and bioprosthetic surgical aortic valve replacement.Peer reviewe

Preoperative paroxysmal atrial fibrillation predicts high cardiovascular mortality in patients undergoing surgical aortic valve replacement with a bioprosthesis: CAREAVR study

Background Preoperative permanent atrial fibrillation (AF) is associated with impaired outcome after surgical aortic valve replacement (SAVR). The impact of preoperative paroxysmal AF, however, has remained elusive.Purpose We assessed the impact of preoperative paroxysmal AF on outcome in patients undergoing SAVR with bioprosthesis.Methods A total of 666 patients undergoing isolated AVR with a bioprosthesis were included. Survival data was obtained from the national registry Statistics Finland. Patients were divided into three groups according to the preoperative rhythm: sinus rhythm (n = 502), paroxysmal AF (n = 90), and permanent AF (n = 74).Results Patients in the sinus rhythm and paroxysmal AF groups did not differ with respect to age (P = .484), gender (P = .402) or CHA(2)DS(2)-VASc score (P = .333). At 12-month follow-up, AF was present in 6.2% of sinus rhythm patients and in 42.4% of paroxysmal AF patients (P Conclusion Patients undergoing SAVR with bioprosthesis and history of paroxysmal AF had higher risk of developing permanent AF, cardiovascular mortality and incidence of fatal strokes compared to patients with preoperative sinus rhythm. Life-long anticoagulation should be considered in patients with a history of preoperative paroxysmal AF.</p

Entrepreneurial sons, patriarchy and the Colonels' experiment in Thessaly, rural Greece

Existing studies within the field of institutional entrepreneurship explore how entrepreneurs influence change in economic institutions. This paper turns the attention of scholarly inquiry on the antecedents of deinstitutionalization and more specifically, the influence of entrepreneurship in shaping social institutions such as patriarchy. The paper draws from the findings of ethnographic work in two Greek lowland village communities during the military Dictatorship (1967–1974). Paradoxically this era associated with the spread of mechanization, cheap credit, revaluation of labour and clear means-ends relations, signalled entrepreneurial sons’ individuated dissent and activism who were now able to question the Patriarch’s authority, recognize opportunities and act as unintentional agents of deinstitutionalization. A ‘different’ model of institutional change is presented here, where politics intersects with entrepreneurs, in changing social institutions. This model discusses the external drivers of institutional atrophy and how handling dissensus (and its varieties over historical time) is instrumental in enabling institutional entrepreneurship

Raman scattering study of the a-GeTe structure and possible mechanism for the amorphous-to-crystal transition

We report on an inelastic (Raman) light scattering study of the local structure of amorphous GeTe films. A detailed analysis of the temperature-reduced Raman spectra has shown that appreciable structural changes occur as a function of temperature. These changes involve modifications of atomic arrangements such as to facilitate the rapid amorphous-to-crystal transformation, which is the major advantage of phase-change materials used in optical data storage media. A particular structural model, supported by polarization analysis, is proposed being compatible with the experimental data as regards both the structure of a-GeTe and the crystallization transition. The remarkable difference between the Raman spectrum of the crystal and the glass can thus naturally be accounted for.Comment: Published in: J. Phys. Condens. Matter. 18, 965-979 (2006

Remote Ischemic Preconditioning Protects the Brain Against Injury After Hypothermic Circulatory Arrest

Background-Ischemic preconditioning (IPC) is a mechanism protecting tissues from injury during ischemia and reperfusion. Remote IPC (RIPC) can be elicited by applying brief periods of ischemia to tissues with ischemic tolerance, thus protecting vital organs more susceptible to ischemic damage. Using a porcine model, we determined whether RIPC of the limb is protective against brain injury caused by hypothermic circulatory arrest (HCA).Methods and Results-Twelve piglets were randomized to control and RIPC groups. RIPC was induced in advance of cardiopulmonary bypass by 4 cycles of 5 minutes of ischemia of the hind limb. All animals underwent cardiopulmonary bypass followed by 60 minutes of HCA at 18 degrees C. Brain metabolism and electroencephalographic activity were monitored for 8 hours after HCA. Assessment of neurological status was performed for a week postoperatively. Finally, brain tissue was harvested for histopathological analysis.Study groups were balanced for baseline and intraoperative parameters. Brain lactate concentration was significantly lower (P < 0.0001, ANOVA) and recovery of electroencephalographic activity faster (P < 0.05, ANOVA) in the RIPC group. RIPC had a beneficial effect on neurological function during the 7-day follow-up (behavioral score; P < 0.0001 versus control, ANOVA). Histopathological analysis demonstrated a significant reduction in cerebral injury in RIPC animals (injury score; mean [interquartile range]: control 5.8 [3.8 to 7.5] versus RIPC 1.5 [0.5 to 2.5], P < 0.001, t test).Conclusions-These data demonstrate that RIPC protects the brain against HCA-induced injury, resulting in accelerated recovery of neurological function. RIPC might be neuroprotective in patients undergoing surgery with HCA and improve long-term outcomes. Clinical trials to test this hypothesis are warranted. (Circulation. 2011; 123: 714-721.