270 research outputs found
Free Discontinuity Design: With an Application to the Economic Effects of Internet Shutdowns
Thresholds in treatment assignments can produce discontinuities in outcomes,
revealing causal insights. In many contexts, like geographic settings, these
thresholds are unknown and multivariate. We propose a non-parametric method to
estimate the resulting discontinuities by segmenting the regression surface
into smooth and discontinuous parts. This estimator uses a convex relaxation of
the Mumford-Shah functional, for which we establish identification and
convergence. Using our method, we estimate that an internet shutdown in India
resulted in a reduction of economic activity by over 50%, greatly surpassing
previous estimates and shedding new light on the true cost of such shutdowns
for digital economies globally.Comment: 29 pages, 7 figures; authors listed alphabetically; code available at
https://github.com/Davidvandijcke/fd
Zur Polymorphie von TbCl3
3 different modifications of TbCl3 were synthesized. TbCl3 (UCl3type). probably in a metastable state, crystallizes in space group P63/m with a = 737.63(2) pm, c = 405.71(2) pm and Z = 2. TbCl3(PuBr3-type) crystallizes in space group Cmcm with a = 384.71(6) pm, b = 1177.37(7) pm, c = 851.77(4) pm and Z = 4. h-TbCl3, the high temperature phase being stable above 790 K, crystallizes in space group P42/mnm with a = 642.51(4) pm, c = 1177.14(18) pm and Z = 4. Š 1988, Walter de Gruyter. All rights reserved
Die Struktur des PrCl3 bei verschiedenen Temperaturen
Structural investigations on PrCl3 were performed from room temperature down to 40 K (powder) and from room temperature down to 83 K (single crystal). Special interest was focussed on the changes of the coordination geometry of the Pr3+-ion
Usefulness of circulating vascular endothelial growth factor and neutrophil elastase as diagnostic markers of disseminated intravascular coagulation in non-cancer patients
Diagnostic Value of Software-Based Image Fusion of Computed Tomography and F18-FDG PET Scans in Patients with Malignant Lymphoma
Aim. The purpose of this study was to evaluate the accuracy of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) positron emission tomography (PET), computed tomography (CT), and software-based image fusion of both modalities in the imaging of non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). Methods. 77 patients with NHL (n = 58) or HD (n = 19) underwent a FDG PET scan, a contrast-enhanced CT, and a subsequent digital image fusion during initial staging or followup. 109 examinations of each modality were evaluated and compared to each other. Conventional staging procedures, other imaging techniques, laboratory screening, and follow-up data constituted the reference standard for comparison with image fusion. Sensitivity and specificity were calculated for CT and PET separately. Results. Sensitivity and specificity for detecting malignant lymphoma were 90% and 76% for CT and 94% and 91% for PET, respectively. A lymph node region-based analysis (comprising 14 defined anatomical regions) revealed a sensitivity of 81% and a specificity of 97% for CT and 96% and 99% for FDG PET, respectively. Only three of 109 image fusion findings needed further evaluation (false positive). Conclusion. Digital fusion of PET and CT improves the accuracy of staging, restaging, and therapy monitoring in patients with malignant lymphoma and may reduce the need for invasive diagnostic procedures
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