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Search Results: 1 - 10 of 5531 matches for " Christoph Schumacher "
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Optimal Costly Information Gathering in Public Service Provision  [PDF]
Paul Geertsema, Christoph Schumacher
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23060
Abstract: Imperfect information regarding the true needs of recipients is a common problem for governmental or not-for-profit service providers. This can lead to potentially dangerous under-provision or wasteful over-provision of services. We provide a method for optimally improving a service provider’s information regarding true client need through costly information gathering. Our contribution is to allow providers to endogenously and optimally choose the intensity of information gathering. Providers do so by specifying the level of correlation between observed and true recipient need, subject to an arbitrary cost function over the specified correlation. We derive the conditions that characterize the choice of optimal correlation for providers with quadratic utility. Using a realistic exponential correlation cost function, we show that there exists a critical value of true client need variance below which it is never optimal to engage in information gathering. Further, for true client variance above this critical level the optimal correlation will always exceed 0.5. Our findings have a wide range of policy implications in areas such as health care, social wellfare and even counter-terroism.
Magic Mushrooms: Screening for Novel Biocatalysts in the Phylum Basidiomycota  [PDF]
Christoph Loderer, Marion B. Ansorge-Schumacher
Advances in Bioscience and Biotechnology (ABB) , 2016, DOI: 10.4236/abb.2016.711043
Abstract: The ascending application of enzymes in organic synthesis creates a growing demand for novel biocatalysts. The applied methods for their identification range from microbial enrichment cultures over metagenome screenings to solely computational methods. In this communication, we demonstrate a straightforward screening approach for the detection of novel biocatalysts in fungi belonging to the phylum Basidiomycota. It basically relies on mincing of the whole fruit bodies of freshly collected mushrooms with subsequent direct screening. Suitability was demonstrated with eight different mushrooms which were investigated for carbonyl reductase activity on sterically demanding carbonyl compounds. The results indicate the presence of potentially useful carbonyl reductases (KREDs) in all tested fungi. Closer characterization of the preparation from pigskin poison puffball (Scleroderma citrinum) showed the presence of KRED exhibiting a broad substrate range. Thus, applicability of this low-tech screening approach could be verified in this study.
Classical Motion in Random Potentials
Andreas Knauf,Christoph Schumacher
Physics , 2011,
Abstract: We consider the motion of a classical particle under the influence of a random potential on R^d, in particular the distribution of asymptotic velocities and the question of ergodicity of time evolution.
Erratum: "The problem of deficiency indices for discrete Schr?dinger operators on locally finite graphs"
Sylvain Golenia,Christoph Schumacher
Mathematics , 2012, DOI: 10.1063/1.4803899
Abstract: In this note we answer negatively to our conjecture concerning the deficiency indices. More precisely, given any non-negative integer $n$, there is locally finite graph on which the adjacency matrix has deficiency indices $(n,n)$.
Approximation of the integrated density of states on sofic groups
Christoph Schumacher,Fabian Schwarzenberger
Mathematics , 2012,
Abstract: In this paper we study spectral properties of self-adjoint operators on a large class of geometries given via sofic groups. We prove that the associated integrated densities of states can be approximated via finite volume analogues. This is investigated in the deterministic as well as in the random setting. In both cases we cover a wide range of operators including in particular unbounded ones. The large generality of our setting allows to treat applications from long-range percolation and the Anderson model. Our results apply to operators on Z^d, amenable groups, residually finite groups and therefore in particular to operators on trees. All convergence results are established without any ergodic theorem at hand.
Graph Laplacians do not generate strongly continuous semigroups
Thomas Kalmes,Christoph Schumacher
Mathematics , 2015,
Abstract: We show that for graph Laplacians $\Delta_G$ on a connected locally finite simplicial undirected graph $G$ with countable infinite vertex set $V$ none of the operators $\alpha\,\mathrm{Id}+\beta\Delta_G, \alpha,\beta\in\mathbb{K},\beta \ne 0$, generate a strongly continuous semigroup on $\mathbb{K}^V$ when the latter is equipped with the product topology.
The problem of deficiency indices for discrete Schr?dinger operators on locally finite graphs
Sylvain Golénia,Christoph Schumacher
Mathematics , 2010, DOI: 10.1063/1.3596179
Abstract: The number of self-adjoint extensions of a symmetric operator acting on a complex Hilbert space is characterized by its deficiency indices. Given a locally finite unoriented simple tree, we prove that the deficiency indices of any discrete Schr\"odinger operator are either null or infinite. We also prove that almost surely, there is a tree such that all discrete Schr\"odinger operators are essentially self-adjoint. Furthermore, we provide several criteria of essential self-adjointness. We also adress some importance to the case of the adjacency matrix and conjecture that, given a locally finite unoriented simple graph, its the deficiency indices are either null or infinite. Besides that, we consider some generalizations of trees and weighted graphs.
Estimation of menstrual blood loss volume based on menstrual diary and laboratory data
Ulrike Schumacher, Jens Schumacher, Uwe Mellinger, Christoph Gerlinger, Andreas Wienke, Jan Endrikat
BMC Women's Health , 2012, DOI: 10.1186/1472-6874-12-24
Abstract: We estimated blood loss volume using data from two clinical studies in women suffering abnormal menstrual bleeding. These estimations were derived from mixed linear models based on diary data, hematological parameters and age. To validate the models, we applied our results to data from a third study with a similar patient population.The resulting best fitting model uses diary entries on bleeding intensity at a particular day, information on occurrence and frequency of single bleeding intensities in defined time windows, hemoglobin and ferritin values and age of the patient all as predictors of menstrual blood loss volume. Sensitivity and specificity for the diagnosis of excessive bleeding were 87% and 70%, respectively. Our model-based estimates reflect the subjective assessment by physicians and patients in the same way as the measured values do.When applying the model to an independent study, we found a correlation of 0.73 between estimated and measured values for the blood loss in a single day. Further models with reduced number of parameters (simplified for easier practical use) still showed correlation values between 0.69 and 0.73.We present a method for estimating menstrual blood loss volume in women suffering from prolonged or excessive menstrual bleeding. Our statistical model includes entries from bleeding diaries, laboratory parameters and age and produces results which correlate well with data derived by the alkaline-hematin-method. Therefore, this model may be used to estimate menstrual blood loss volume in both routine gynecological counseling and clinical studies.Abnormal uterine bleeding is an important clinical topic both within clinical studies and during gynecological consultation [1-3]. Changes in bleeding intensity or intracyclic bleeding might be symptoms of pathological processes. Dysfunctional uterine bleedings, including heavy, frequent and prolonged bleedings may not only substantially decrease quality of life, but can also cause iron-defici
Understanding competing risks: a simulation point of view
Arthur Allignol, Martin Schumacher, Christoph Wanner, Christiane Drechsler, Jan Beyersmann
BMC Medical Research Methodology , 2011, DOI: 10.1186/1471-2288-11-86
Abstract: We advocate a simulation point of view for understanding competing risks. The hazards are envisaged as momentary event forces. They jointly determine the event time. Their relative magnitude determines the event type. 'Empirical simulations' using data from a recent study on cardiovascular events in diabetes patients illustrate subsequent interpretation. The method avoids concerns on identifiability and plausibility known from the latent failure time approach.The 'empirical simulations' served as a proof of concept. Additionally manipulating baseline hazards and treatment effects illustrated both scenarios that require greater care for interpretation and how the simulation point of view aids the interpretation. The simulation algorithm applied to real data also provides for a general tool for study planning.There are as many hazards as there are competing risks. All of them should be analysed. This includes estimation of baseline hazards. Study planning must equally account for these aspects.The analysis of time-to-event data ('survival analysis') has evolved into a well established application of advanced statistical methodology in medicine. E.g., in the New England Journal of Medicine, survival methods have evolved from an occasionally used technique in the late 70s over moderate use in the late 80s into the leading statistical procedure by 2005 [1]. The archetypical application analyses time until death, but combined endpoints are also frequently considered. E.g., a recent literature review in clinical oncology [2] found a multitude of combined endpoints including, e.g., progression-free survival, distant metastasis-free survival, locoregional relapse-free survival, etc. The medical problems at hand will, as these endpoints exemplarily suggest, usually be more complex than can be addressed by the analysis of time until one potentially combined event type.Competing risks techniques allow for a more specific analysis in that they consider time until occurrence of t
Benchmarking the quality of breast cancer care in a nationwide voluntary system: the first five-year results (2003–2007) from Germany as a proof of concept
Sara Y Brucker, Claudia Schumacher, Christoph Sohn, Mahdi Rezai, Michael Bamberg, Diethelm Wallwiener, the Steering Committee
BMC Cancer , 2008, DOI: 10.1186/1471-2407-8-358
Abstract: BC centres participated voluntarily in a scientific benchmarking procedure. A generic XML-based data set was developed and used for data collection. Nine guideline-based quality targets serving as rate-based QIs were initially defined, reviewed annually and modified or expanded accordingly. QI changes over time were analysed descriptively.During 2003–2007, respective increases in participating breast centres and postoperatively confirmed BCs were from 59 to 220 and from 5,994 to 31,656 (> 60% of new BCs/year in Germany). Starting from 9 process QIs, 12 QIs were developed by 2007 as surrogates for long-term outcome. Results for most QIs increased. From 2003 to 2007, the most notable increases seen were for preoperative histological confirmation of diagnosis (58% (in 2003) to 88% (in 2007)), appropriate endocrine therapy in hormone receptor-positive patients (27 to 93%), appropriate radiotherapy after breast-conserving therapy (20 to 79%) and appropriate radiotherapy after mastectomy (8 to 65%).Nationwide external benchmarking of BC care is feasible and successful. The benchmarking system described allows both comparisons among participating institutions as well as the tracking of changes in average quality of care over time for the network as a whole. Marked QI increases indicate improved quality of BC care.Implementing and maintaining quality assurance procedures and improving cancer care are two key areas of multidisciplinary oncology today. With the high incidence of breast cancer (BC) and the recognised necessity for a multidisciplinary approach to its treatment, the management of this cancer can be considered a prototypical example of an entire process chain ranging from early detection, diagnosis and treatment to follow-up.Multidisciplinary and intersectoral, i.e. in- and out-patient, BC care requires elements of quality management, particularly at various interfaces along the process chain. In addition, maintaining a quality management system (QMS) with contin
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