Entwicklung und Anwendung von Hochleistungs-Software für Mantelkonvektionssimulationen

The Earth mantle convects on a global scale, coupling the stress field at every point to every other location at an instant. This way, any change in the buoyancy field has an immediate impact on the convection patterns worldwide. At the same time, mantle convection couples to processes at scales of a few kilometers or even a few hundred meters. Dynamic topography and the geoid are examples of such small-scale expressions of mantle convection. Also, the depth of phase transitions varies locally, with strong influences on the buoyancy, and thus the global stress field. In order to understand these processes dynamically it is essential to resolve the whole mantle at very high numerical resolutions. At the same time, geodynamicists are trying to answer new questions with their models, for example about the rheology of the mantle, which is most likely highly nonlinear. Also, due to the extremely long timescales we cannot observe past mantle states, which calls for simulations backwards in time. All these issues lead to an extreme demand in computing power. To cater to those needs, the physical models of the mantle have to be matched with efficient solvers and fast algorithms, such that we can efficiently exploit the enormous computing power of current and future high performance systems. Here, we first give an extensive overview over the physical models and introduce some numerical concepts to solve the equations. We present a new two-dimensional software as a testbed and elaborate on the implications of realistic mineralogic models for efficient mantle convection simulations. We find that phase transitions present a major challenge and suggest some procedures to incorporate them into mantle convection modeling. Then we give an introduction to the high-performance mantle convection prototype HHG, a multigrid-based software framework that scales to some of the fastest computers currently available. We adapt this framework to a spherical geometry and present first application examples to answer geodynamic questions. In particular, we show that a very thin and very weak asthenosphere is dynamically plausible and consistent with direct and indirect geological observations.Englische Übersetzung des Titels: Development and application of high performance software for mantle convection modelin

Entwicklung und Anwendung von Hochleistungs-Software für Mantelkonvektionssimulationen

The Earth mantle convects on a global scale, coupling the stress field at every point to every other location at an instant. This way, any change in the buoyancy field has an immediate impact on the convection patterns worldwide. At the same time, mantle convection couples to processes at scales of a few kilometers or even a few hundred meters. Dynamic topography and the geoid are examples of such small-scale expressions of mantle convection. Also, the depth of phase transitions varies locally, with strong influences on the buoyancy, and thus the global stress field. In order to understand these processes dynamically it is essential to resolve the whole mantle at very high numerical resolutions. At the same time, geodynamicists are trying to answer new questions with their models, for example about the rheology of the mantle, which is most likely highly nonlinear. Also, due to the extremely long timescales we cannot observe past mantle states, which calls for simulations backwards in time. All these issues lead to an extreme demand in computing power. To cater to those needs, the physical models of the mantle have to be matched with efficient solvers and fast algorithms, such that we can efficiently exploit the enormous computing power of current and future high performance systems. Here, we first give an extensive overview over the physical models and introduce some numerical concepts to solve the equations. We present a new two-dimensional software as a testbed and elaborate on the implications of realistic mineralogic models for efficient mantle convection simulations. We find that phase transitions present a major challenge and suggest some procedures to incorporate them into mantle convection modeling. Then we give an introduction to the high-performance mantle convection prototype HHG, a multigrid-based software framework that scales to some of the fastest computers currently available. We adapt this framework to a spherical geometry and present first application examples to answer geodynamic questions. In particular, we show that a very thin and very weak asthenosphere is dynamically plausible and consistent with direct and indirect geological observations.Englische Übersetzung des Titels: Development and application of high performance software for mantle convection modelin

Visualization of climate simulation data in virtual reality using commercial game engines

Due to the size of its customer base the video game industry has long been the best-funded proponent of innovative real-time computer graphics. Many advancements in the field of computer graphics, software and hardware, have become cost-effective due to their use in video games, which in turn funded even further research and breakthroughs. Recent changes in the monetization of commercial game engines made their use in less revenue driven institutions affordable and, hence, possible. This allows us, given suitable hardware, to build and run computationally expensive fully interactive real-time visualizations at a fraction of the cost and time. We can thus investigate and explore the data in our virtual reality application far sooner. Additionally, we are able to spend more time to iteratively refine the user interaction as well as the preprocessing of the raw scientific data. We supply our visualization with the output data of ClimEx’ computational run on the SuperMUC. ClimEx is a research project that studies the effects of climate change on meteorological and hydrological extreme events. It features a multitude of climate-relevant variables and observes the time span between 1950 and 2100. For our use case we chose to compare three different precipitation events. Each event consists of simulated 60 hours of rainfall data anteceding a potential 100-year flood, which is a flood event that has an annual exceedance rate of 1%. The first event draws from historical data and represents the rain leading up to the 1999 Pentecost flood. We compare these data with two computer generated prospective events, which take place in 2060 and 2081, respectively. Since we wish to gain knowledge on strong local extrema as well as the comprehensive overall trend of the attributes, we chose to display the data in virtual reality. The virtually unlimited number of perspectives and points of view simplify investigating and understanding the three-dimensional data. We are also able to place the observer at the center of the data and empower them to interact with and steer the visualization in intuitive ways. By utilizing a tool like virtual reality, we are able to create an immersive, interactive and engaging user experience, which further facilitates the user’s ability to focus on the visual display and extract information from the displayed data. This allows users, especially non-expert users, to grasp the data we present in our visualization with less effort. In our paper we present the necessary steps to create an immersive virtual reality 3D visualization from raw scientific data based on our use case. This entails several aspects of pre-processing, a simple, suitable user interface as well as our solutions to the challenges we encountered

Recurrent primary sclerosing cholangitis in the Adult‐to‐Adult Living Donor Liver Transplantation Cohort Study: Comparison of risk factors between living and deceased donor recipients

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134274/1/lt24496_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134274/2/lt24496.pd

Impact on follow-up strategies in patients with primary sclerosing cholangitis.

BACKGROUND & AIMS Evidence for the benefit of scheduled imaging for early detection of hepatobiliary malignancies in primary sclerosing cholangitis (PSC) is limited. We aimed to compare different follow-up strategies in PSC with the hypothesis that regular imaging improves survival. METHODS We collected retrospective data from 2975 PSC patients from 27 centres. Patients were followed from the start of scheduled imaging or in case of clinical follow-up from 1 January 2000, until death or last clinical follow-up alive. The primary endpoint was all-cause mortality. RESULTS A broad variety of different follow-up strategies were reported. All except one centre used regular imaging, ultrasound (US) and/or magnetic resonance imaging (MRI). Two centres used scheduled endoscopic retrograde cholangiopancreatography (ERCP) in addition to imaging for surveillance purposes. The overall HR (CI95%) for death, adjusted for sex, age and start year of follow-up, was 0.61 (0.47-0.80) for scheduled imaging with and without ERCP; 0.64 (0.48-0.86) for US/MRI and 0.53 (0.37-0.75) for follow-up strategies including scheduled ERCP. The lower risk of death remained for scheduled imaging with and without ERCP after adjustment for cholangiocarcinoma (CCA) or high-grade dysplasia as a time-dependent covariate, HR 0.57 (0.44-0.75). Hepatobiliary malignancy was diagnosed in 175 (5.9%) of the patients at 7.9 years of follow-up. Asymptomatic patients (25%) with CCA had better survival if scheduled imaging had been performed. CONCLUSIONS Follow-up strategies vary considerably across centres. Scheduled imaging was associated with improved survival. Multiple factors may contribute to this result including early tumour detection and increased endoscopic treatment of asymptomatic benign biliary strictures

Using virtual reality to visualize extreme rainfall events derived from climate simulations

Virtual reality (VR) is an emerging and powerful tool to visualize and explore complex scientific data sets in an intuitive, interactive and user-friendly manner. In this study, we explore the usage of VR to create an immersive visualization of hydrological extreme events based on climate simulations. We aim to make use of the added values of VR to promote the communication of scientific results on potential natural hazards to the public. The visualization data are taken from climate simulations within the ClimEx project, which is an international collaboration between research facilities, universities and public water agencies in Bavaria and Quélbec. The project investigates the effects of climate change on meteorological and hydrological extreme events and implications for water management in the two regions. Within this project, an ensemble of 50 transient runs of the regional climate model CRCM5 were run at approximately 11 km spatial resolution for two domains in Europe and North America from 1950 to 2100. As each of these runs is initialized with only slightly altered starting conditions, this ensemble can be interpreted as modelled natural variability. From this data set, we extracted precipitation data regarding one historical flooding event, the Pentecost flood in Southern Germany and Austria in May 1999, as well as precipitation data for two designated future intense rainfall events in the 2060s and 2080s for the same region. Data for these three extreme rainfall events were visualized in VR using a 3D representation of topography of the region of interest as the background. This VR representation was enhanced with satellite images (on top of the topography), points of interest (for easier navigation) and images of the historic Pentecost flood event (for emphazising the impact of the flood event). We will present the necessary steps to create this immersive virtual reality 3D visualization from the raw scientific data and discuss several aspects of the visual design and the adopted user interface

1011-116 Myocardial Rb Extraction Fraction: Determination in Humans

Ouantitation of myocardial blood flow (MBF) with diffusion-limited radiotracers as 82Rb and positron emission tomography (PET) requires knowledge of flow dependence of myocardial 82Rb extraction fraction. To determine this dependence we evaluated 7 patients (mean age (61.0±9.7) years, 4 males, 3 females) who had undergone coronary angiography with exclusion of relevant coronary stenoses and normal left ventricular function. 82Rb-PET clearance was simultaneously assessed with global MBF by the argon (Ar) inert gas method. 82Rb clearance was dynamically measured by a CTI-Siemens ECAT 931-08-12 scanner after i.v. injection of 1–1.2 GBq 82Rb. Ar gas desaturation was obtained by simultaneous arterial and coronary sinus blood sampling. Measurements were performed at rest and during vasodilatation induced by i.v. dipyridamole (0.7mg/kg/4min). Mean 82Rb clearance and Ar flow values were (0.39±0,03)ml/g/min and (0.69±0.14)ml/g/min at rest, respectively, and (0.47±0.09)ml/g/min and (1.48±0.49)ml/g/min during hyperemia. A fit with a two compartment model yielded E=PS/(PS+MBF) with PS=(0.82±0.09)ml/g/min (PS: permeability surface area product). These data (figure) provide for the best of our knowledge the first measured 82Rb extraction fraction in humans and may form the basis for more accurate quantitation of myocardial blood flow with 82Rb-PET

Is electrical stimulation during administration of catecholamines required for the evaluation of success after ablation of atrioventricular node re-entrant tachycardias?

AbstractObjectivesThe purpose of this study was to answer the question of whether stimulation after administration of catecholamines is mandatory for identifying unsuccessful ablations of atrioventricular node re-entrant tachycardia (AVNRT).BackgroundThe success of radiofrequency (RF) catheter ablation in AVNRT is confirmed in many centers by noninducibility of tachycardias during stimulation after the administration of catecholamines.MethodsA total of 131 patients (81 women and 50 men; mean age 53.6 ± 13.7 years [range 20 to 77]) were studied. Electrical stimulation was performed without and with the beta-adrenergic amine Orciprenaline (metaproterenol) before and after RF catheter ablation.ResultsIn 100 patients (76.3%; confidence interval [CI] 68.1% to 83.3%) an AVNRT was inducible without administration of Orciprenaline. Thirty minutes after the initially successful ablation in 95 patients, tachycardia was inducible in none of these patients, not even after Orciprenaline administration. In the 31 patients (23.7%; CI 16.7% to 31.9%) in whom there was no tachycardia inducible before ablation, Orciprenaline was given, and the stimulation protocol was repeated. In only five patients (3.8%; CI 1.3% to 8.7%) was there still no tachycardia inducible. After an initially successful ablation in the 26 patients who had inducible tachycardias with Orciprenaline before ablation, no tachycardia could be re-induced. After Orciprenaline, the tachycardia was inducible again in only one patient.ConclusionsOnly patients who require catecholamines for tachycardia induction before ablation need catecholamines for control of the success of the ablation of AVNRT