25 research outputs found
Solar Winds Driven by Nonlinear Low-Frequency Alfven Waves from the Photosphere : Parametric Study for Fast/Slow Winds and Disappearance of Solar Winds
(abridged) We investigate how the properties of the corona and solar wind in
the open coronal holes depend on the properties of the magnetic fields and
their footpoint motions at the surface, by perfoming 1D MHD simulations from
the photosphere to 0.3 or 0.1AU. We impose low-frequency (<0.05Hz) transverse
fluctuations of the field lines at the photosphere with various amplitude,
spectrum, and polarization in the open flux tubes with different photospheric
field strength, B, and super-radial expansion of the cross section, f_max. We
find that a transonic solar wind is the universal consequence. The atmosphere
is also stably heated up to >10^6K by the dissipation of the Alfven waves
through compressive-wave generation and wave reflection in the case of the
sufficient wave input with photospheric amplitude, > 0.7km/s. The density,
and accordingly the mass flux, of solar winds show a quite sensitive dependence
on because of an unstable aspect of the heating by the nonlinear Alfven
waves. A case with =0.4km/s gives ~50 times smaller mass flux than the
fiducial case for the fast wind with =0.7km/s; solar wind almost disappears
only if becomes half. We also find that the solar wind speed has a
positive correlation with B/f_max, which is consistent with recent
observations. We finally show that both fast and slow solar winds can be
explained by the single process, the dissipation of the low-frequency Alfven
waves, with different sets of and B/f_max. Our simulations naturally
explain the observed (i) anticorrelation of the solar wind speed and the
coronal temperature and (ii) larger amplitude of the Alfvenic fluctuations in
the fast winds. In Appendix, we also explain our implementation of the outgoing
boundary condition of the MHD waves with some numerical tests.Comment: 27 pages, 16 figures embedded, accepted for publication in J.
Geophys. Re
Phlebologie an deutschen Hautkliniken: eine Bestandsaufnahme im Auftrag der Deutschen Gesellschaft fĂŒr Phlebologie
Reich-Schupke S, Alm J, Altmeyer P, et al. Phlebologie an deutschen Hautkliniken: Eine Bestandsaufnahme im Auftrag der Deutschen Gesellschaft fĂŒr Phlebologie. Hautarzt. 2013;64(9):685-694.Phlebologic diseases have become extremely common and have major socio-economic impact. However, the percentage of dermatologists working in phlebology appears to be decreasing according to the data of the German Society of Phlebology (DGP). To investigate the reasons for this development, we-on behalf of the DGP-sent a questionnaire to 120 German Departments of Dermatology in autumn 2012. In 76 returned questionnaires, the number of physicians with additional fellowship training in phlebology averaged 1.5; the average number of those who fulfill the criteria for training fellows in phlebology was 0.9. In 71.1 % of the departments there was a phlebologist. A special phlebologic outpatient clinic existed in 73.7 % of the departments. Sonography with Doppler (89.5 %) and duplex (86.8 %) was used as the most frequent diagnostic tool. For therapy, compression (94.7 %), sclerotherapy (liquid 78.9 %, foam 63.2 %, catheter 18.4 %), endoluminal thermic procedures (radio wave 28.9 %, laser 17.1 %) and surgery (especially crossectomy and stripping 67.1 %, phlebectomy of tributaries 75 %) were used. The average number of treatments was very heterogenous in the different departments. Phlebology definitely plays an important role in dermatology. Most departments fulfill the formal criteria for the license to conduct advanced training in phlebology. A wide spectrum of phlebological diagnostic and therapeutic procedures is available.Hintergrund
Venenleiden sind eine Volkskrankheit und haben eine enorme sozioökonomische Bedeutung. Dennoch scheint der Anteil der phlebologisch tĂ€tigen Dermatologen entsprechend den Zahlen der Deutschen Gesellschaft fĂŒr Phlebologie (DGP) abzunehmen.
Methoden
Um die Ursachen dieser Entwicklung zu untersuchen, fĂŒhrten wir im Herbst 2012 im Auftrag der DGP eine Befragungsstudie zur Phlebologie an 120 deutschen Hautkliniken durch.
Ergebnisse
In 76 antwortenden Klinien gab es im Mittel 1,5 Phlebologen und 0,9 Ărzte mit Voraussetzungen zur WeiterbildungsermĂ€chtigung Phlebologie. In 71,1â% der Kliniken gab es einen Phlebologen, in 73,7â% eine phlebologische Sprechstunde. Zur Diagnostik wurden besonders die Doppler- (89,5â%) und Duplexsonographie (86,8â%) eingesetzt. In der Therapie fĂŒhrte die Kompressionstherapie (94,7â%), gefolgt von Sklerosierungstherapien (flĂŒssig 78,9â%, Schaum 63,2â%, Katheter 18,4â%), den endoluminalen thermischen Verfahren (Radiowelle 28,9â%, Laser 17,1â%) und den operativen Eingriffen (vor allem Cross- und Saphenektomie 67,1â%, Seitenastexhairese 75â%). Die durchschnittlichen Behandlungszahlen waren sehr heterogen.
Schlussfolgerung
Die Phlebologie spielt in der Dermatologie weiterhin eine wichtige Rolle. Mehrheitlich sind in den Kliniken die Möglichkeiten zur Weiterbildung Phlebologie gegeben. Es wird ein breites Spektrum an phlebologischen Techniken zur Diagnostik und Therapie angeboten
Nonâinvasive evaluation of newâonset atrial fibrillation after cardiac surgery: a protocol for the BigMap study
Abstract Aims Newâonset atrial fibrillation (NOAF) is the most common complication after cardiac surgery, occurring in 25â50% of patients. It is associated with postâoperative stroke, increased mortality, prolonged hospital length of stay, and higher treatment costs. Previous small observational studies have identified the left atrium as a source of the electrical rotors and foci maintaining NOAF, but confirmation by a large prospective clinical study is still missing. The aim of the proposed study is to investigate whether the source of NOAF lies in the left atrium. The correct identification of NOAFâmaintaining structures in cardiac surgical patients might offer potential therapeutic targets for prophylactic perioperative ablation strategies. Methods and results This is a prospective singleâcentre observational study of patients developing NOAF after cardiac surgery. The primary outcome is the description of NOAFâmaintaining structures within the atria. Key secondary outcomes include overall mortality, intensive care unit length of stay, hospitalâventilatorâfree days, and proportion of persistent NOAF. In NOAF patients, the nonâinvasive electrophysiological mapping will be conducted using a 252âelectrode electrocardiogram vest. After mapping, a lowâdose computed tomography scan of the chest will be performed to integrate the electrophysiological mapping results into a 3D picture of the heart. The study will include approximately 570 patients, of whom 30% (n = 170) are expected to develop NOAF. Sample size calculation revealed that 157 NOAF patients are necessary to assess the primary outcome. Patients will be tracked for a total of 5 years. Conclusions This is the largest prospective study to date describing the electrophysiological mechanisms of NOAF using nonâinvasive mapping