39 results on '"Wagner, Siegfried"'
Search Results
2. Association of retinal neurodegeneration with the progression of cognitive decline in Parkinson's disease.
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Murueta-Goyena, Ane, Romero-Bascones, David, Teijeira-Portas, Sara, Urcola, J. Aritz, Ruiz-Martínez, Javier, Del Pino, Rocío, Acera, Marian, Petzold, Axel, Wagner, Siegfried Karl, Keane, Pearse Andrew, Ayala, Unai, Barrenechea, Maitane, Tijero, Beatriz, Gómez Esteban, Juan Carlos, and Gabilondo, Iñigo
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- 2024
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3. Evaluating an automated machine learning model that predicts visual acuity outcomes in patients with neovascular age-related macular degeneration.
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Abbas, Abdallah, O'Byrne, Ciara, Fu, Dun Jack, Moraes, Gabriella, Balaskas, Konstantinos, Struyven, Robbert, Beqiri, Sara, Wagner, Siegfried K., Korot, Edward, and Keane, Pearse A.
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MACULAR degeneration ,VISUAL acuity ,MACHINE learning ,ENDOTHELIAL growth factors ,TREATMENT effectiveness - Abstract
Purpose: Neovascular age-related macular degeneration (nAMD) is a major global cause of blindness. Whilst anti-vascular endothelial growth factor (anti-VEGF) treatment is effective, response varies considerably between individuals. Thus, patients face substantial uncertainty regarding their future ability to perform daily tasks. In this study, we evaluate the performance of an automated machine learning (AutoML) model which predicts visual acuity (VA) outcomes in patients receiving treatment for nAMD, in comparison to a manually coded model built using the same dataset. Furthermore, we evaluate model performance across ethnic groups and analyse how the models reach their predictions. Methods: Binary classification models were trained to predict whether patients' VA would be 'Above' or 'Below' a score of 70 one year after initiating treatment, measured using the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. The AutoML model was built using the Google Cloud Platform, whilst the bespoke model was trained using an XGBoost framework. Models were compared and analysed using the What-if Tool (WIT), a novel model-agnostic interpretability tool. Results: Our study included 1631 eyes from patients attending Moorfields Eye Hospital. The AutoML model (area under the curve [AUC], 0.849) achieved a highly similar performance to the XGBoost model (AUC, 0.847). Using the WIT, we found that the models over-predicted negative outcomes in Asian patients and performed worse in those with an ethnic category of Other. Baseline VA, age and ethnicity were the most important determinants of model predictions. Partial dependence plot analysis revealed a sigmoidal relationship between baseline VA and the probability of an outcome of 'Above'. Conclusion: We have described and validated an AutoML-WIT pipeline which enables clinicians with minimal coding skills to match the performance of a state-of-the-art algorithm and obtain explainable predictions. [ABSTRACT FROM AUTHOR]
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- 2022
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4. Predicting sex from retinal fundus photographs using automated deep learning.
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Korot, Edward, Pontikos, Nikolas, Liu, Xiaoxuan, Wagner, Siegfried K., Faes, Livia, Huemer, Josef, Balaskas, Konstantinos, Denniston, Alastair K., Khawaja, Anthony, and Keane, Pearse A.
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DEEP learning ,RETINAL imaging ,RECEIVER operating characteristic curves ,SENSITIVITY & specificity (Statistics) ,BIOMARKERS - Abstract
Deep learning may transform health care, but model development has largely been dependent on availability of advanced technical expertise. Herein we present the development of a deep learning model by clinicians without coding, which predicts reported sex from retinal fundus photographs. A model was trained on 84,743 retinal fundus photos from the UK Biobank dataset. External validation was performed on 252 fundus photos from a tertiary ophthalmic referral center. For internal validation, the area under the receiver operating characteristic curve (AUROC) of the code free deep learning (CFDL) model was 0.93. Sensitivity, specificity, positive predictive value (PPV) and accuracy (ACC) were 88.8%, 83.6%, 87.3% and 86.5%, and for external validation were 83.9%, 72.2%, 78.2% and 78.6% respectively. Clinicians are currently unaware of distinct retinal feature variations between males and females, highlighting the importance of model explainability for this task. The model performed significantly worse when foveal pathology was present in the external validation dataset, ACC: 69.4%, compared to 85.4% in healthy eyes, suggesting the fovea is a salient region for model performance OR (95% CI): 0.36 (0.19, 0.70) p = 0.0022. Automated machine learning (AutoML) may enable clinician-driven automated discovery of novel insights and disease biomarkers. [ABSTRACT FROM AUTHOR]
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- 2021
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5. Code-free deep learning for multi-modality medical image classification.
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Korot, Edward, Guan, Zeyu, Ferraz, Daniel, Wagner, Siegfried K., Zhang, Gongyu, Liu, Xiaoxuan, Faes, Livia, Pontikos, Nikolas, Finlayson, Samuel G., Khalid, Hagar, Moraes, Gabriella, Balaskas, Konstantinos, Denniston, Alastair K., and Keane, Pearse A.
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- 2021
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6. Turbulence Modeling and Detached Eddy Simulation with a High-Order Unstructured Discontinuous Galerkin Code.
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Lübon, Christian, Kessler, Manuel, and Wagner, Siegfried
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In the present paper a high-order Discontinuous Galerkin method is presented for the numerical simulation of the separated turbulent flow around complex geometries using unstructured grids. Bassi and Rebay extended the Discontinuous Galerkin method to solve the Navier-Stokes equations for laminar and 3D turbulent flows. Especially, an extension will be provided to calculate unsteady separated flows with a Detached Eddy Simulation, which is a hybrid method between the Unsteady Reynolds averaged Navier-Stokes approach and the Large Eddy Simulation. Some results, like flows over a flat plate and around a sphere, which could not be predicted with an Unsteady Reynolds averaged Navier-Stokes calculation, are calculated with high accuracy and compared with theory and experiments. [ABSTRACT FROM AUTHOR]
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- 2010
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7. Three-Dimensional Discontinuous Galerkin Codes to Simulate Viscous Flow by Spatial Discretization of High Order and Curved Elements on Unstructured Grids.
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Hirschel, E. H., Schröder, W., Fujii, K., Haase, W., van Leer, B., Leschziner, M. A., Pandolfi, M., Periaux, J., Rizzi, A., Roux, B., Shokin, Yu., Tropea, Cameron, Jakirlic, Suad, Heinemann, Hans-Joachim, Henke, Rolf, Hönlinger, Heinz, Lühon, Christian, and Wagner, Siegfried
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The need of high order boundary discretization in case of a high order code, e.g. a Discontinuous Gaierkin (DG) Code, has already been demonstrated in the literature. Bassi and Rebay extended the DG method to solve the Navier-Stokes equations for laminar and 3D turbulent flow. In the present paper an extension will be provided to include both three-dimensional flows and curved elements to properly represent three-dimensional bodies with curvature. Some results, like Sows around a sphere and around an Onera M6 wing, are calculated and compared with experiments. [ABSTRACT FROM AUTHOR]
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- 2008
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8. Computational Study of the Aeroelastic Equilibrium Configuration of a Swept Wind Tunnel Wing Model in Subsonic Flow.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Reimer, L., Braun, C., and Ballmann, J.
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In the Collaborative Research Center SFB 401 at RWTH Aachen University, the numerical aeroelastic method SOFIA for direct numerical aeroelastic simulation is being progressively developed. Numerical results obtained by applying SOFIA were compared with measured data of static and dynamic aeroelastic wind tunnel tests for an elastic swept wing in subsonic flow. [ABSTRACT FROM AUTHOR]
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- 2007
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9. Aeroelastic Simulations of Isolated Rotors Using Weak Fluid-Structure Coupling.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Dietz, M., Kessler, M., and Krämer, E.
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In this paper we present a weak fluid-structure coupling method for the aeroelastic simulation of isolated helicopter main rotors. The CFD Code FLOWer (by DLR) is coupled to the flight mechanics code HOST (by Eurocopter). HOST is used to compute the blade dynamics and the rotor trim, whereas the aerodynamic loads are determined by FLOWer. The method has been applied to two different rotors: the advanced EC145 rotor in fast forward flight and the well known Bo105 rotor in slow descent flight. [ABSTRACT FROM AUTHOR]
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- 2007
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10. Numerical Investigation and Simulation of Transition Effects in Hypersonic Intake Flows.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Krause, Martin, Reinartz, Birgit, and Ballmann, Josef
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A numerical and experimental analysis of a Scramjet intake flow has been initiated at RWTH Aachen University as part of the Research Training Group GRK 1095: "Aerothermodynamic Design of a Scramjet Engine for a Future Space Transportation System". This report presents an overview of the ongoing work on numerical simulations using Reynolds averaged Navier-Stokes solvers. Two different geometry concepts in 2D and 3D are investigated using several turbulence models to point out the influence of the geometry on the flow behaviour. One with a double ramp/convex curve configuration, the other with a double ramp/convex corner configuration. The data obtained will be compared with results from experiments which will be started in autumn 2006. It has to be said that not all results presented here were achieved using the NEC computing cluster. For comparison several calculations were conducted on the IBM Jump system of the Jülich Research Centre and at the SUN cluster of RWTH Aachen University. At the end of this report the computational performance will be compared. [ABSTRACT FROM AUTHOR]
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- 2007
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11. Investigation of the Influence of the Inlet Geometry on the Flow in a Swirl Burner.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, García-Villalba, Manuel, Fröhlich, Jochen, and Rodi, Wolfgang
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A series of Large Eddy Simulations (LES) of non-reacting flow in a swirl burner has been performed. The configuration consists of two unconfined co-annular jets at a Reynolds number of 81500. The flow is characterized by a Swirl number of 0.93. Two cases are studied differing with respect to the axial location of the inner pilot jet. It was observed in a companion experiment (Bender and Büchner, 2005) [1] that when the inner jet is retracted the flow oscillations are considerably amplified. The present simulations allow to understand this phenomenon: the recirculation zone and the jet interact in such a way that large scale coherent structures are generated. The resulting spectra correspond well to the experimental data. [ABSTRACT FROM AUTHOR]
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- 2007
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12. The Effects of Vortex Generator Arrays on Heat Transfer and Flow Field.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Dietz, C. F., Henze, M., Neumann, S. O., von Wolfersdorf, J., and Weigand, B.
- Abstract
The effect of arrays of single-body, delta shaped vortex generators on heat transfer and flow field has been investigated numerically using RANS (Reynolds averaged Navier-Stokes) methods. The Reynolds number based on the hydraulic diameter of the channel in which the vortex generators are positioned is fixed at 300,000. For the closure of the equation system of the flow field a full differential Reynolds stress model has been used to capture the anisotropic effects of the induced vortex structures. To gain realistic results for the heat transfer the common approach for the closure of the Reynolds-averaged energy equation using a turbulent Prandtl number has been abandoned for explicit algebraic models which deliver more realistic results for complex flows. Simultaneously to the calculations measurements have been performed on some of the geometries to validate the numerical results. [ABSTRACT FROM AUTHOR]
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- 2007
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13. Rheological Properties of Binary and Ternary Amphiphilic Fluid Mixtures.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Harting, Jens, and Giupponi, Giovanni
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Within this project, we perform lattice Boltzmann simulations of spinodal decomposition and structuring effects in binary immiscible and ternary amphiphilic fluid mixtures under shear. We use a highly scalable parallel Fortran 90 code for the implementation of the lattice Boltzmann method. We demonstrate that the domain growth mechanisms in ternary amphiphilic fluid mixtures strongly depend on the amphiphile concentration. For systems under constant and oscillatory shear we analyze domain growth rates in directions parallel and perpendicular to the applied shear and find that these systems undergo structural transitions with tubular and lamellar structures appearing. [ABSTRACT FROM AUTHOR]
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- 2007
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14. Investigations of Flow and Species Transport in Packed Beds by Lattice Boltzmann Simulations.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, and Zeiser, Thomas
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This report summarizes selected results of investigations of the flow and species transport in packed beds. First of all, the difficulty of segmenting image data with respect to the correct choice of the threshold value and thus the resulting porosity is discussed. Then, the accuracy of lattice Boltzmann flow simulations is compared with CFX-5 simulations. The 3-D flow data is furthermore used to show how the pressure drop is made up by shear forces and dissipation owing to elongation and deformation. For the species transport, a random walk particle tracking algorithm is used to complement the lattice Boltzmann method thus allowing a wide range of Peclet numbers. In the last part, preliminary performance results of a new 1-D list based lattice Boltzmann implementation ("sparse lattice") are summarized which soon will replace the currently used full array based code. It is shown that outstanding performance on vector as well as cache based parallel computers can be achieved with this 1-D list based "sparse lattice" code, too. Despite sophisticated optimizations for cache based microprocessors, the sustained application performance of a single NEC SX-8 CPU is about 10-20 times higher than that of any commodity CPU. For parallel calculations, this gap even grows further. [ABSTRACT FROM AUTHOR]
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- 2007
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15. Prediction of the Resonance Characteristics of Combustion Chambers on the Basis of Large-Eddy Simulation.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Magagnato, Franco, Pritz, Balázs, Büchner, Horts, and Gabi, Martin
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Self-excited (thermo-acoustic) oscillations often occur in combustion systems due to the combustion instabilities. The high pressure oscillations can lead to higher emissions and structural damage of the chamber. For the disposal of the undesirable oscillations one must clearly know the mechanism of the feedback of periodic perturbations in the combustion system. In the last years intensive experimental investigations were performed at the University of Karlsruhe to develop an analytical model for the Helmholtz resonator-type combustion system. In order to understand better the flow effects in the chamber and to localize the dissipation large-eddy simulations (LES) were carried out. In this paper the results of the LES are presented, which show good agreement with the experiments. The comparison of the LES study with the experiments sheds light on the significant role of the wall roughness in the exhaust gas pipe. [ABSTRACT FROM AUTHOR]
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- 2007
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16. Large Eddy Simulation of Open-Channel Flow Over Spheres.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Stoesser, Thorsten, and Rodi, Wolfgang
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The paper presents results of several Large Eddy Simulations (LES) of the flow in an open channel where the channel bed is roughened with one or two layers of spheres. The roughness height k, which corresponds to the sphere diameter d is 0.23 of the channel depth. The Reynolds number Reτ, based on the average friction velocity uτ and the channel depth h (distance from the roughness tops of the spheres to the water surface) is approximately 2820. The flow configurations were selected to correspond to recently performed laboratory experiments. Mean streamwise velocities from the LES are compared with the measured data and the distributions of the calculated turbulence intensities are evaluated by comparing them with empirical relationships for flow over rough walls suggested by Nezu [1]. The occurrence of low- and high-speed streaks is examined and their spanwise spacing is quantified. Moreover, sweeps and ejections are shown to occur as well as the amalgamation process i.e. ejection of fluid into the outer layer associated with vortex growth. It is shown that these structures occur irrespective of roughness conditions, however further studies and data analysis are needed to evaluate and quantify the effect of porosity on coherent structures. [ABSTRACT FROM AUTHOR]
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- 2007
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17. Large-Eddy Simulation of Tundish Flow.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Alkishriwi, Nouri, Meinke, Matthias, and Schröder, Wolfgang
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Large-eddy simulations (LES) of a continuous tundish flow are carried out to investigate the turbulent flow structure and vortex dynamics. The numerical computations are performed by solving the viscous conservation equations for compressible fluids. An implicit dual time stepping scheme combined with low Mach number preconditioning and a multigrid accelerating technique is developed for LES computations. The method is validated by comparing data of turbulent pipe flow at Reτ = 1280 and cylinder flow at Re = 3900 at different Mach numbers with experimental findings from the literature. The impact of jet spreading, jet impingement on the wall, and wall jets on the flow field and steel quality is investigated. The characteristics of the flow field in a one-strand tundish such as the time-dependent turbulent flow structure and vortex dynamics is analyzed and compared with experimental results. [ABSTRACT FROM AUTHOR]
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- 2007
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18. Efficient Implementation of Nonlinear Deconvolution Methods for Implicit Large-Eddy Simulation.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Hickel, S., and Adams, N. A.
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The adaptive local deconvolution method (ALDM) provides a systematic framework for the implicit large-eddy simulation (ILES) of turbulent flows. Exploiting numerical truncation errors, the subgrid scale model of ALDM is implicitly contained within the discretization. An explicit computation of model terms therefore becomes unnecessary. Subject of the present paper is the efficient implementation and the application to large-scale computations of this method. We propose a modification of the numerical algorithm that allows for reducing the amount of computational operations without affecting the quality of the LES results. Computational results for isotropic turbulence and plane channel flow show that the proposed simplified adaptive local deconvolution (SALD) method performs similarly to the original ALDM and at least as well as established explicit models. [ABSTRACT FROM AUTHOR]
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- 2007
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19. LES and DNS of Melt Flow and Heat Transfer in Czochralski Crystal Growth.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Raufeisen, A., Breuer, M., Kumar, V., Botsch, T., and Durst, F.
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In the present work, computations of flow and heat transfer in an idealized cylindrical Czochralski configuration are conducted using Large Eddy Simulation (LES) with the flow solver FASTEST-3D developed at LSTM Erlangen. The results match well with DNS data from the literature. However, detailed data for analysis of turbulent quantities are not available. Therefore, DNS computations are conducted using the code LɛSOCC, employing explicit time marching. Preliminary simulations show the high efficiency of the solver on the NEC SX-8. Furthermore, from a study of the velocity profiles at the wall, the resolution requirements had to be corrected such that the computational grid will now consist of approximately 8 × 106 control volumes. The present run of the DNS took more than 540 hours of walltime on 8 processors. With the results, the LES computations will be thoroughly validated so that appropriate models and parameters can be chosen for efficient and accurate simulations of practically relevant cases. [ABSTRACT FROM AUTHOR]
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- 2007
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20. Parallel Large Eddy Simulation with UG.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Hauser, Andreas, and Wittum, Gabriel
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The simulation of the fluid flow has been simulated on the levels l2, l3, l4. The results on level l2 and l4 are plausible and suggest convergent behavior, whereas the results on l3 does not fit in this sequence. The quantitative comparison along a line within the numerics show good agreement for all three levels. This can be explained with the fact, that the velocities in the middle of the mixer coincide in the cross section after the mixing element too. The ultimate validation with experiments show quite good agreement with respect to quality and quantity. Finally, as uniform refinement increases the complexity of the computation tremendously, effort in adaptive methods for turbulent flow has been invested already and should be applied to the static mixer soon. [ABSTRACT FROM AUTHOR]
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- 2007
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21. Numerical Simulation of the Bursting of a Laminar Separation Bubble.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Marxen, Olaf, and Henningson, Dan
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Numerical simulations of laminar separation bubbles are carried out to investigate the so-called bubble bursting, i.e. the changeover from a short to a long bubble by means of very small variation of one governing parameter. A laminar separation bubble is formed if a laminar boundary layer separates in a region of adverse pressure gradient on a flat plate and undergoes transition, leading to a reattached turbulent boundary layer. Bubble bursting denotes a phenomenon, in which a local, in average closed region of reverse flow (the short separation bubble) suddenly becomes considerably longer as a result of only small changes in the conditions of the surrounding flow. Here, this condition is the disturbance input upstream of separation. Both, long laminar separation bubbles and bubble bursting, are not yet well understood on a fundamental level, but it is commonly accepted that the transition process plays an important role. Simulations in which transition is or is not explicitly triggered are carried out. Depending on this triggering, either a short laminar separation bubble develops or the bursting process is initiated and the flow develops towards a long-bubble state. If the flow is tripped to turbulence prior to the adverse pressure gradient, the boundary layer remains attached. Performance data on a NEC SX-8 super computer are given for two different resolutions. [ABSTRACT FROM AUTHOR]
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- 2007
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22. Direct Numerical Simulation of Mixing and Chemical Reactions in a Round Jet into a Crossflow — a Benchmark.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Denev, J. A., Fröhlich, J., and Bockhorn, H.
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A benchmark simulation of the jet in crossflow (JICF) configuration is presented in detail. A Direct Numerical Simulation (DNS) was carried out with a low Reynolds number equal to 275 and a jet-to-crossflow velocity ratio equal to 2.4. The benchmark is carefully selected to provide reference data concerning the following phenomena: the flowfield, the mixing process of passive scalars and three chemical reactions. The data presented concern both instantaneous and time-averaged values as well as the corresponding fluctuations. To facilitate the quantitative comparison with the data from the present work various one-dimensional plots are presented. To allow easy repetition of the present numerical benchmark, both the jet and the crossflow are supplied at laminar flow conditions. As a result of this a transition zone occurs which in turn constitutes a severe test for any simulation methodology. [ABSTRACT FROM AUTHOR]
- Published
- 2007
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23. Direct Numerical Simulation of Primary Breakup Phenomena in Liquid Sheets.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Sander, Wolfgang, and Weigand, Bernhard
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Starting from the first experimental and analytical studies on primary breakup phenomena, many interesting results have been published in the past. It is known that in addition to the typical dimensionless groups (Reynolds and Weber number), inflow conditions can drastically influence primary breakup phenomena. Now that high computational resources are available, direct numerical simulation (DNS) has become a powerful tool in order to study primary breakup phenomena. Nevertheless only a few DNS studies concerning breakup phenomena and the influence of inflow conditions are available. This might be due to the fact that besides high demands of computational resources, sophisticated numerical models are also required in order to prescribe realistic inflow conditions and capture all length scales in the flow. This paper mainly focuses on the influence of different inflow conditions, such as the integral length scale or the fluctuation level inside the turbulent nozzle flow. For this, the breakup phenomena of water sheets at moderate Reynolds numbers injected into an quiescent air environment are considered. Since this study is performed as an numerical experiment by varying the character of the inflow velocity data, it was found that not only the mean axial velocity profile but also the integral length scale and the fluctuation level can have an influence on breakup phenomena. [ABSTRACT FROM AUTHOR]
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- 2007
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24. Direct Numerical Simulation and Analysis of the Flow Field Around a Swept Laminar Separation Bubble.
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Nagel, Wolfgang E., Jäger, Willi, Resch, Michael, Wagner, Siegfried, Hetsch, Tilman, and Rist, Ulrich
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The transition process around a short leading-edge separation bubble subjected to a sweep angle of 30° is studied in detail by means of direct numerical simulation, spatial linear stability theory and solutions of the parabolised stability equations. The combined analysis of the averaged flow field, instantaneous flow visualisations and postprocessing data as amplification curves leads to the distinction of four succeeding stages qualitatively comparable to the unswept case. It is shown that the saturation of background disturbances is the key event, after which a rapid breakdown of transitional structures occurs. The mechanism of the final breakdown of this swept scenario of fundamental resonance is best described as an "oblique K-type transition". Great care is taken to isolate and describe of typical structures within each stage as a foundation for the analysis of complex transition scenarios. [ABSTRACT FROM AUTHOR]
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- 2007
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25. Hepatic artery embolization for treatment of patients with hereditary hemorrhagic telangiectasia and symptomatic hepatic vascular malformations.
- Author
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Chavan, Ajay, Caselitz, Martin, Gratz, Karl-Friedrich, Lotz, Joachim, Kirchhoff, Timm, Piso, Plinio, Wagner, Siegfried, Manns, Michael, and Galanski, Michael
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THERAPEUTIC embolization ,TELANGIECTASIA ,VASODILATION ,CENTRAL nervous system depressants ,ANTI-infective agents ,ABDOMINAL pain ,ANTIBIOTICS ,PLATINUM ,ANALGESICS ,ANTIEMETICS ,HEART disease complications ,POLYSTYRENE ,ANGIOGRAPHY ,COMPARATIVE studies ,HEART diseases ,HEART failure ,HEPATIC artery ,LONGITUDINAL method ,RESEARCH methodology ,MEDICAL cooperation ,RESEARCH ,STEEL ,EVALUATION research ,HEPATIC veins ,ARTERIOVENOUS malformation ,DISEASE complications ,HEREDITARY hemorrhagic telangiectasia ,THERAPEUTICS - Abstract
At present there is no established therapy for treating patients with hereditary hemorrhagic telangiectasia (HHT) and symptomatic hepatic involvement. We present the results of a prospective study with 15 consecutive patients who were treated with staged hepatic artery embolization (HAE). Branches of the hepatic artery were selectively catheterized and embolized in stages using polyvinyl alcohol particles (PVA) and platinum microcoils or steel macrocoils. Prophylactic antibiotics, analgesics and anti-emetics were administered after every embolization. Clinical symptomatology and cardiac output were assessed before and after therapy as well as at the end of follow-up (median 28 months; range 10-136 months). Five patients had abdominal pain and four patients had symptoms of portal hypertension. The cardiac output was raised in all patients, with cardiac failure being present in 11 patients. After treatment, pain resolved in all five patients, and portal hypertension improved in two of the four patients. The mean cardiac output decreased significantly ( P<0.001) from 12.57+/-3.27 l/min pre-treatment to 8.36+/-2.60 l/min at the end of follow-up. Symptoms arising from cardiac failure resolved or improved markedly in all but one patient. Cholangitis and/or cholecystitis occurred in three patients of whom two required a cholecystectomy. One patient with pre-existent hepatic cirrhosis died as a complication of the procedure. Staged HAE yields long-term relief of clinical symptoms in patients with HHT and hepatic involvement. Patients with pre-existing hepatic cirrhosis may be poor candidates for HAE. [ABSTRACT FROM AUTHOR]
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- 2004
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26. A rare manifestation of Behçet's syndrome: immunological correlates and successful treatment of an esophageal ulcer.
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Wedemeyer, Heiner, Kuipers, Jens G, Streetz, Konrad, Mengel, Michael, Schedel, Ingolf, Kezmic, Nikolina, Meier, Peter, Zeidler, Henning, Manns, Michael P, and Wagner, Siegfried
- Subjects
ANTI-inflammatory agents ,PREDNISONE ,SULFONAMIDES ,BEHCET'S disease ,ESOPHAGUS diseases ,ULCERS ,TREATMENT effectiveness ,DISEASE complications ,THERAPEUTICS - Published
- 2003
27. COACH syndrome associated with multifocal liver tumors
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Kirchner, Gabriele I., Wagner, Siegfried, Flemming, Peer, Bleck, Joerg S., Gebel, Michael, Schedel, Ingolf, Schüler, Andreas, Galanski, Michael, and Manns, Michael P.
- Subjects
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LIVER tumors , *SYNDROMES , *PRECANCEROUS conditions , *ULTRASONIC imaging , *MAGNETIC resonance imaging - Abstract
Here, we describe a 20-yr-old woman with COACH syndome (hypoplasia of Cerebellar vermis, Oligophrenia, congenital Ataxia, Coloboma, and Hepatic fibrosis) developing multiple liver lesions. Epigastric and right upper abdominal pain and lack of appetite led to clinical evaluation. Liver function tests showed an increase in transaminases and cholestatic parameters; α-fetoprotein was in the normal range. Ultrasound and magnetic resonance imaging examinations revealed multiple liver lesions. Histological examinations of ultrasonographically guided biopsies were consistent with regenerative hepatic nodules without features of malignant or dysplastic cells. The sizes of these tumors did not change over a period of 12 months. Our report presents the 10th case of COACH syndrome with a hitherto undescribed association with hepatic tumors. [Copyright &y& Elsevier]
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- 2002
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28. Fate of goblet cells in experimental colitis.
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Makkink, Mireille K., Schwerbrock, Nicole M.J., Mähler, Michael, Boshuizen, Jos A., Renes, Ingrid B., Cornberg, Markus, Hedrich, Hans J., Einerhand, Alexandra W.C., Büller, Hans A., Wagner, Siegfried, Enss, Marie-Luise, Dekker, Jan, Mähler, Michael, and Büller, Hans A
- Subjects
COLITIS ,EXFOLIATIVE cytology - Abstract
We sought to correlate the characteristic changes in goblet cell morphology in the chronically inflamed large intestine of 1L10-/- mice to specific changes in goblet cell gene expression. In healthy as well as IL10-/- mice, marked differences were found among the large intestinal regions in goblet cell morphology and gene expression. The mucin Muc2, which is a major determinant of goblet cell morphology, was expressed in most goblet cells, yet only in cells staining positive for both Alcian blue and high iron diamine. TFF3 was expressed in only a small subset of goblet cells. Inflamed colon of IL10-/- mice still contained high numbers of small, hypotrophic goblet cells with similar histochemical staining and Muc2 and TFF3 expression patterns, contradicting the often reported "goblet cell depletion" in colitis. Quantitatively, the Muc2 and TFF3 levels remained relatively stabile in IL10-/- mice. Muc2 in distal IL10-/- colon contained significantly less sulfate residues than in controls, which may compromise its protective properties. [ABSTRACT FROM AUTHOR]
- Published
- 2002
29. p53 mutation pattern and expression of c-erbB2 and c-met in gastric cancer: relation to histological subtypes, Helicobacter pylori infection, and prognosis.
- Author
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Kubicka, Stefan, Claas, Christiane, Staab, Sven, Kühnel, Florian, Zender, Lars, Trautwein, Christian, Wagner, Siegfried, Rudolph, Karl, Manns, Michael, Kühnel, Florian, and Rudolph, Karl Lenhard
- Subjects
COMPARATIVE studies ,GENES ,HELICOBACTER diseases ,HELICOBACTER pylori ,RESEARCH methodology ,MEDICAL cooperation ,METASTASIS ,GENETIC mutation ,ONCOGENES ,PROGNOSIS ,RESEARCH ,STOMACH tumors ,EVALUATION research ,DISEASE complications - Abstract
The molecular mechanisms of Helicobacter pylori associated tumor development are poorly understood. The spectra of genetic alterations in neoplasms may provide clues to the molecular carcinogenesis of a tumor and may be relevant for the prognosis of the patients. We investigated the p53 mutation pattern and the protein expression of p53, c-erbB2, and c-met in 42 gastric cancers and correlated these alterations with H. pylori infection, histological subtypes and survival of the patients after curative resection. There were no differences in the incidences of the expression of p53, c-erbB2, and c-met in the tumor tissues according to H. pylori infection. Fifteen p53 mutations in 12 (29%) tumors were identified. More p53 mutations were found in patients with positive serology for H. pylori (43% vs 14%). This difference was not significant, but the small sample size may be insufficient to detect a potential statistical difference. There was neither a H. pylori-associated p53 hot-spot codon mutation nor a H. pylori characteristic mutational pattern of p53. Positive lymph nodes (P = 0.0061) and p53 mutations (P = 0.0035) were the only significant bad prognostic markers for survival after curative resection of the gastric cancers in our study. Our study does not indicate a unique molecular mechanism of p53 mutagenesis through H. pylori infection. The fact that p53 mutations were significantly correlated with poor survival of patients after potentially curative resection of gastric cancer may have clinical implications for multimodal therapies. [ABSTRACT FROM AUTHOR]
- Published
- 2002
- Full Text
- View/download PDF
30. Helicobacter pylori reduces intracellular glutathione in gastric epithelial cells.
- Author
-
Beil, Winfried, Obst, Barbara, Sewing, Karl-Friedrich, Wagner, Siegfried, Beil, W, Obst, B, Sewing, K F, and Wagner, S
- Abstract
Helicobacter pylori infection has been associated with stimulation of gastric mucosal reactive oxygen species (ROS) production, and it was postulated that ROS production is due to neutrophil infiltration and activation. The aim of this study was to investigate the direct effect of H. pylori on ROS formation in gastric epithelial cells in vitro. The human gastric cancer cell line HM02 was incubated with H. pylori for 24 hr, and the effects on cell number and the intracellular radical scavenger reduced glutathione (GSH) were assessed. H. pylori caused a concentration-dependent reduction of cellular GSH concentrations over a broad bacteria-to-cell ratio (1.4-42) in the absence of cell necrosis. The radical scavengers MnTBAP (a cell permeable superoxide dismutase) and ebselen provided protection against H. pylori-induced decrease in cellular GSH concentrations. We conclude that H. pylori directly decreases cellular GSH concentrations in gastric epithelial cells. We suggest that this effect is caused by the release of ROS by H. pylori. [ABSTRACT FROM AUTHOR]
- Published
- 2000
- Full Text
- View/download PDF
31. Seltene Erstmanifestation und Differentialdiagnose einer primär sklerosierenden Cholangitis.
- Author
-
Rehermann, Barbara, Klugewitz, Katja, Seifert, Ulrike, Böker, Klaus, Wagner, Siegfried, and Manns, Michael
- Abstract
Copyright of Medizinische Klinik (Urban & Vogel) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 1997
- Full Text
- View/download PDF
32. Hepatoma With Severe Non-Islet Cell Tumor Hypoglycemia.
- Author
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Tietge, Uwe J., Schöfl, Christof, Ocran, Kenneth W., Wagner, Siegfried, Böker, Klaus H. W., Brabant, Georg, Zapf, Jürgen, and Manns, Michael P.
- Subjects
HEPATITIS B ,PATIENTS ,HEPATOCELLULAR carcinoma ,HYPOGLYCEMIA ,PARANEOPLASTIC syndromes ,SOMATOMEDIN ,PATHOLOGICAL physiology - Abstract
We report a 22-yr-old male patient with chronic hepatitis B and a large, well differentiated hepatoma who developed episodes of symptomatic fasting hypoglycemia, which were caused by paraneoplastic secretion of unprocessed "big" insulin-like growth factor-II. Initially, the patient presented with normal liver function, which deteriorated during the clinical course. Therapeutic attempts to reduce tumor mass failed and the patient subsequently died because of metastases of the hepatoma. The pathophysiology of non-islet cell tumor hypoglycemia, differential diagnosis, and therapeutic options are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 1998
- Full Text
- View/download PDF
33. Helicobacter pylori Infection and Serum Pepsinogen A, Pepsinogen C, and Gastrin in Gastritis and Peptic Ulcer: Significance of Inflammation and Effect of Bacterial Eradication.
- Author
-
Wagner, Siegfried, Haruma, Ken, Gladziwa, Ulrich, Soudah, Bisharah, Gebel, Michael, Bleck, Jörg, Schmidt, Hartmut, and Manns, Michael
- Subjects
HELICOBACTER pylori infections ,GASTRIN ,PEPSINOGEN ,PEPTIC ulcer ,GASTRIC mucosa - Abstract
Objectives: To study the relationship between Helicobacter pylori infection, gastric inflammatory scores, and fasting gastrin and pepsinogen A and C concentrations, and to evaluate the effect of treatment on these parameters. Methods: Gastrin and pepsinogen A and C concentrations were measured in 36 patients with gastritis, 10 gastric ulcer patients, 12 duodenal ulcer patients, and in 15 subjects with normal gastric mucosa, by standard radioimmunoassay techniques. Fifteen patients with H. pylori infection underwent triple therapy (bismuth subsalicylate, amoxicillin, metronidazole) and were reassessed 1 month later. Results: Fasting gastrin and pepsinogen A and C concentrations were significantly higher in H. pylori-positive gastritis and peptic ulcer patients than in subjects with normal mucosa and in patients with H. pylori-negative gastritis. There was a significant correlation between inflammatory scores and serum gastrin (r = 0.45, p < 0.0001), and pepsinogen A (r = 0.33, p < 0.006) and pepsinogen C (r = 0.55, p < 0.0001) concentrations. Neither sex nor age affected basal gastrin and pepsinogen concentrations. Eradication of H. pylori infection was successful in 12 patients and resulted in a significant fall in serum gastrin and in pepsinogen A and C concentrations, and in a concomitant improvement of the inflammatory scores. Serum peptide levels and gastritis scores were unchanged in those patients in whom H. pylori infection persisted. Conclusions: These findings suggest that hypergastrinemia and hyperpepsinogenemia are secondary to H. pylori infection and are related to mucosal inflammation. [ABSTRACT FROM AUTHOR]
- Published
- 1994
34. Die Aminosäurebelastung als Leberfunktionsprüfung.
- Author
-
Wagner, Siegfried and Gneiting, Werner
- Abstract
Copyright of Zeitschrift Für Die Gesamte Experimentelle Medizin is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 1934
- Full Text
- View/download PDF
35. Zur Isotopieverschiebung im Cul-Spektrum.
- Author
-
Wagner, Siegfried
- Abstract
Copyright of Zeitschrift für Physik is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 1955
- Full Text
- View/download PDF
36. Computational Fluid Dynamics.
- Author
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Krause, Egon, Jäger, Willi, Resch, Michael, and Wagner, Siegfried
- Abstract
Numerical simulation of complex flows has always demanded the biggest com-puters both in storage capacity and in performance that were available on the market. This situation is still going on. The following paragraph repre-sents a selection of papers that were submitted as yearly demanded progress reports to the HLRS. Although most of the reports revealed a very high sci-entific standard those papers were preferably selected for publication that clearly demostrated the unalterable usage of high performance computers (HFC) for the solution of the problem. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
37. Necrotizing tuberculosis with duodenal perforation as a primary manifestation of AIDS.
- Author
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Hartl, Janine, Maier, Judith, Caselitz, Martin, Salzberger, Bernd, Wagner, Siegfried, Zuelke, Carl, Blaas, Stefan, Lubnow, Matthias, Schölmerich, Juergen, and Kirchner, Gabi
- Subjects
LETTERS to the editor ,TUBERCULOSIS diagnosis ,PULMONARY manifestations of general diseases - Abstract
A letter to the editor is presented which discusses a case of a 35-year-old Caucasian male who was diagnosed with tuberculosis, an AIDS-defining disease usually presenting with primary pulmonary manifestation.
- Published
- 2012
- Full Text
- View/download PDF
38. Campylobacter pylori and Gastric Acidity.
- Author
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Wagner, Siegfried, Freise, Jürgen, Beholz, Sven, and Schmidt, Friedrich Werner
- Subjects
LETTERS to the editor ,HELICOBACTER pylori - Abstract
Presents a letter to the editor about Campylobacter pylori and gastric acidity.
- Published
- 1989
39. The Spleen as a Storage Pool in Lipid Metabolism.
- Author
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Schmidt, Hartmut H.-J., Wagner, Siegfried, and Manns, Michael
- Subjects
NEWSPAPERS ,HYPERTRIGLYCERIDEMIA - Abstract
Presents a letter to the editor about a case of exacerbation of hypertriglyceridemia after splenectomy.
- Published
- 1997
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