False Discovery Rate Control for Lesion-Symptom Mapping with Heterogeneous data via Weighted P-values

Lesion-symptom mapping studies provide insight into what areas of the brain are involved in different aspects of cognition. This is commonly done via behavioral testing in patients with a naturally occurring brain injury or lesions (e.g., strokes or brain tumors). This results in high-dimensional observational data where lesion status (present/absent) is non-uniformly distributed with some voxels having lesions in very few (or no) subjects. In this situation, mass univariate hypothesis tests have severe power heterogeneity where many tests are known a priori to have little to no power. Recent advancements in multiple testing methodologies allow researchers to weigh hypotheses according to side-information (e.g., information on power heterogeneity). In this paper, we propose the use of p-value weighting for voxel-based lesion-symptom mapping (VLSM) studies. The weights are created using the distribution of lesion status and spatial information to estimate different non-null prior probabilities for each hypothesis test through some common approaches. We provide a monotone minimum weight criterion which requires minimum a priori power information. Our methods are demonstrated on dependent simulated data and an aphasia study investigating which regions of the brain are associated with the severity of language impairment among stroke survivors. The results demonstrate that the proposed methods have robust error control and can increase power. Further, we showcase how weights can be used to identify regions that are inconclusive due to lack of power

False discovery rate control for lesion-symptom mapping with heterogeneous data via weighted p-values

Statistic

Quality control in resting-state fMRI: the benefits of visual inspection

Background: A variety of quality control (QC) approaches are employed in resting-state functional magnetic resonance imaging (rs-fMRI) to determine data quality and ultimately inclusion or exclusion of a fMRI data set in group analysis. Reliability of rs-fMRI data can be improved by censoring or “scrubbing” volumes affected by motion. While censoring preserves the integrity of participant-level data, including excessively censored data sets in group analyses may add noise. Quantitative motion-related metrics are frequently reported in the literature; however, qualitative visual inspection can sometimes catch errors or other issues that may be missed by quantitative metrics alone. In this paper, we describe our methods for performing QC of rs-fMRI data using software-generated quantitative and qualitative output and trained visual inspection. Results: The data provided for this QC paper had relatively low motion-censoring, thus quantitative QC resulted in no exclusions. Qualitative checks of the data resulted in limited exclusions due to potential incidental findings and failed pre-processing scripts. Conclusion: Visual inspection in addition to the review of quantitative QC metrics is an important component to ensure high quality and accuracy in rs-fMRI data analysis

Numerische Stroemungsberechnung in einem thermischen Lichtbogentriebwerk mit Wasserstoff als Treibstoff Abschlussbericht

For a further increase of the performance of the high power arcjet 'HIPARC-R' developed and successfully tested at the Stuttgart University, the flowfield of the thruster has been computed. As a first step the flow calculation of the cold propellant gas without electric arc has been performed using the finite volume Navier-Stokes code NSFLEX. The flowfield is idealized as an axisymmetric laminar viscous reacting gas flow with an electric arc. The effects of current discharge and chemical reactions are taken in account by energy source terms resulting from ohmic heating and heat of reaction. For the calculation, the chemistry module, the current discharge code, and the flow field code were combined to determine the flow field, the chemical composition and the current density in the gas, and the calculation was repeated until convergence. The flow field is discretized with a structured curvilinear mesh with increased line concentration at the boundary walls. The discretized field includes a region beyond the nozzle exit to compare the numerical results with the experimental data. (WEN)Available from TIB Hannover: RR 1814(1996,7) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDeutsche Forschungsgemeinschaft (DFG), Bonn (Germany)DEGerman

Numerische Simulation von MPD-Triebwerken und Vergleich mit durchzufuehrenden experimentellen Untersuchungen Endbericht

Available from TIB Hannover: RR 1814(1997,10) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDeutsche Forschungsgemeinschaft (DFG), Bonn (Germany)DEGerman

Instabilitaeten in MPD-Triebwerken Endbericht

This final report of the research project carried out under the promotional identification number 50TA90095 covers the three-year theoretical and experimental work carried out at the Institute for Space Systems (IRS) of Stuttgart University. The theoretical investigations comprised both the formulation and solution of the linear dispersion equation for identification of instabilities in the flow of MPD self-consistent field accelerators and the development of appropriate high-resolution methods for multi-component plasma flow simulation. Two major instabilities were found: a modified space charge instability, which may lead to current interruptions, and a macroscopic electrostatic wave instability, which may cause energy deprivation of the electrons. In accompanying experiments a series of diagnostics was tested and used for measurements in the region of the instabilities. This was carried out both for nozzle-shaped and for purely cylindrical MPD engine types. Diagnostics mainly involved the use of current and voltage measurements, probe measurements (various types of electrostatic triple probes) and Fabry-Perot interferometry. (orig.)Available from TIB Hannover: RR 1814(1993,6)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman