571 research outputs found

    Many Masses on One Stroke: Economic Computation of Quark Propagators

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    The computational effort in the calculation of Wilson fermion quark propagators in Lattice Quantum Chromodynamics can be considerably reduced by exploiting the Wilson fermion matrix structure in inversion algorithms based on the non-symmetric Lanczos process. We consider two such methods: QMR (quasi minimal residual) and BCG (biconjugate gradients). Based on the decomposition M/κ=1/κDM/\kappa={\bf 1}/\kappa-D of the Wilson mass matrix, using QMR, one can carry out inversions on a {\em whole} trajectory of masses simultaneously, merely at the computational expense of a single propagator computation. In other words, one has to compute the propagator corresponding to the lightest mass only, while all the heavier masses are given for free, at the price of extra storage. Moreover, the symmetry γ5M=Mγ5\gamma_5\, M= M^{\dagger}\,\gamma_5 can be used to cut the computational effort in QMR and BCG by a factor of two. We show that both methods then become---in the critical regime of small quark masses---competitive to BiCGStab and significantly better than the standard MR method, with optimal relaxation factor, and CG as applied to the normal equations.Comment: 17 pages, uuencoded compressed postscrip

    Spatial Besov Regularity for Stochastic Partial Differential Equations on Lipschitz Domains

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    We use the scale of Besov spaces B^\alpha_{\tau,\tau}(O), \alpha>0, 1/\tau=\alpha/d+1/p, p fixed, to study the spatial regularity of the solutions of linear parabolic stochastic partial differential equations on bounded Lipschitz domains O\subset R^d. The Besov smoothness determines the order of convergence that can be achieved by nonlinear approximation schemes. The proofs are based on a combination of weighted Sobolev estimates and characterizations of Besov spaces by wavelet expansions.Comment: 32 pages, 3 figure

    Design Dimensions for Enterprise-Wide Data Management: A Chief Data Officer’s Journey

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    To unlock additional business value, most enterprises are intensifying their enterprise-wide data management. In the case of the globally operating bank, we base this article on, a Chief Data Officer (CDO) organization is established for providing data governance and, in a second step, pushing data driven innovation forward. As many employees of the bank were not yet familiar with (or did not acknowledge) the need for enterprise-wide data management, this evolution exhibits characteristics of an organizational learning process. CDOs may want to actively steer this learning process by purposefully designing and adjusting their data management approach over time. Based on the major controversies the CDO has been confronted with, we propose four design dimensions for enterprise-wide data management and discuss the considerations for their configuration: (I) objective, (II) governance, (III) organization of data analytics, and (IV) expertise

    Promotion and growth diagrams for fans of Dyck paths and vacillating tableaux

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    We construct an injection from the set of rr-fans of Dyck paths (resp. vacillation tableaux) of length nn into the set of chord diagrams on [n][n] that intertwines promotion and rotation. This is done in two different ways, namely as fillings of promotion--evacuation diagrams and in terms of Fomin growth diagrams. Our analysis uses the fact that rr-fans of Dyck paths and vacillating tableaux can be viewed as highest weight elements of weight zero in crystals of type BrB_r and CrC_r, respectively, which in turn can be analyzed using virtual crystals. On the level of Fomin growth diagrams, the virtualization process corresponds to Krattenthaler's blow up construction. One of the motivations for finding rotation invariant diagrammatic bases such as chord diagrams is the cyclic sieving phenomenon. Indeed, we give a cyclic sieving phenomenon on rr-fans of Dyck paths and vacillating tableaux using the promotion action.Comment: 40 pages, 13 figure

    Spurensuche in Döbeln

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    COVID-19 und Lebererkrankungen

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    Bis zu 53 % der PatientInnen mit Coronavirus Disease 2019 (COVID-19) weisen eine hepatische Beteiligung auf. Durch die Expression der Hauptzielstruktur für „severe acute respiratory syndrome coronavirus type 2“ (SARS-CoV-2), des Angiotensin-converting-Enzym-2(ACE2)-Rezeptors, auch auf Cholangiozyten, sinusoidalen Endothelzellen und Hepatozyten kann es zu einer direkten Schädigung der Leber kommen. Ferner spielt eine indirekte (nicht durch Rezeptoren vermittelte) Schädigung der Leber im Rahmen von COVID-19 durch eine schwere systemische Inflammation mit Zytokinsturm, hepatischen Thrombosen und einer systemischen Hypoxie eine wichtige Rolle. Bei COVID-19 gelten Leberwerte als wichtige Prädiktoren für die Prognose der PatientInnen. Wichtig ist es hierbei Differenzialdiagnosen für die Leberwerterhöhung, wie andere Virusinfektionen, medikamentös-toxisch induzierte Leberschädigung sowie autoimmune, metabolische und andere Lebererkrankungen, abzuklären. Von hoher klinischer Relevanz für die Behandlung kritisch kranker PatientInnen auf der Intensivstation ist das Krankheitsbild der „secondary sclerosing cholangitis in critically ill patients“ (SSC-CIP). Hierfür sind unter anderem hochdosierte Katecholamine, eine Beatmung mit hohem positivem endexspiratorischem Druck (PEEP) und die extrakorporale Membranoxygenierung (ECMO) Risikofaktoren. Eine frühe Diagnose dieser Erkrankung und Behandlung mittels interventioneller endoskopischer retrograder Cholangiographie (ERC) ist hierbei von entscheidender Bedeutung. Auch sollte eine Lebertransplantation evaluiert werden. Bei einer COVID-19-Erkrankung treten Fälle mit SSC, sog. COVID-SSC, auf. Die COVID-SSC und die SSC-CIP sind im klinischen Phänotyp, Risikofaktoren, Prognose und transplantatfreien Überleben vergleichbar. PatientInnen mit vorbestehender Lebererkrankung haben kein erhöhtes Risiko für eine Infektion mit SARS-CoV‑2, erkranken jedoch schwerer an COVID-19 als PatientInnen ohne Lebervorerkrankungen. Bei PatientInnen mit einer vorbestehenden Leberzirrhose kann eine SARS-CoV-2-Infektion ein akut-auf-chronisches Leberversagen (ACLF) induzieren. Hierbei handelt es sich um ein Krankheitsbild mit einer sehr hohen Mortalität, das im Rahmen einer intensivmedizinischen Behandlung therapiert werden muss. ---------------------------------------------------- In patients with coronavirus disease 2019 (COVID-19), hepatic involvement occurs in up to 53% of all cases. Via the primary target for severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), the angiotensin-converting enzyme 2 (ACE2) receptor, expressed on cholangiocytes, sinusoidal endothelial cells, and hepatocytes, direct damage to the liver may occur. Furthermore, indirect (= not receptor-mediated) damage to the liver plays a crucial role in the context of COVID-19 due to severe systemic inflammation with cytokine storm, hepatic thrombosis, and systemic hypoxia. In COVID-19, liver enzymes are considered significant predictors of outcome. Thus, it is essential to rule out other causes of liver enzyme elevation, such as other viral infections, drug-induced liver injury, and metabolic, autoimmune and other liver diseases. Secondary sclerosing cholangitis in critically ill patients (SSC-CIP) is highly relevant in treating critically ill patients in the intensive care unit (ICU). Risk factors for SSC-CIP include high doses of catecholamines, high positive end-expiratory pressure (PEEP), and extracorporeal membrane oxygenation (ECMO) therapy. Early recognition of this disease and treatment by endoscopic retrograde cholangiography (ERC) is crucial. Furthermore, liver transplantation should be evaluated. Some patients with COVID-19 are diagnosed with SSC, which is termed COVID-19-associated SSC. COVID-19-associated SSC and SSC-CIP are comparable with regard to clinical phenotype, risk factors, prognosis, and graft-free survival. Patients with pre-existing liver disease are not at increased risk for infection with SARS-CoV‑2 but show more severe clinical courses of COVID-19 than patients without pre-existing liver disease. Patients with pre-existing liver cirrhosis may develop acute-on-chronic liver failure (ACLF) upon infection with SARS-CoV‑2. ACLF has a high mortality rate, which must be treated in the ICU
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