SurfelMeshing: Online Surfel-Based Mesh Reconstruction

We address the problem of mesh reconstruction from live RGB-D video, assuming a calibrated camera and poses provided externally (e.g., by a SLAM system). In contrast to most existing approaches, we do not fuse depth measurements in a volume but in a dense surfel cloud. We asynchronously (re)triangulate the smoothed surfels to reconstruct a surface mesh. This novel approach enables to maintain a dense surface representation of the scene during SLAM which can quickly adapt to loop closures. This is possible by deforming the surfel cloud and asynchronously remeshing the surface where necessary. The surfel-based representation also naturally supports strongly varying scan resolution. In particular, it reconstructs colors at the input camera's resolution. Moreover, in contrast to many volumetric approaches, ours can reconstruct thin objects since objects do not need to enclose a volume. We demonstrate our approach in a number of experiments, showing that it produces reconstructions that are competitive with the state-of-the-art, and we discuss its advantages and limitations. The algorithm (excluding loop closure functionality) is available as open source at https://github.com/puzzlepaint/surfelmeshing .Comment: Version accepted to IEEE Transactions on Pattern Analysis and Machine Intelligenc

Why Having 10,000 Parameters in Your Camera Model is Better Than Twelve

Camera calibration is an essential first step in setting up 3D Computer Vision systems. Commonly used parametric camera models are limited to a few degrees of freedom and thus often do not optimally fit to complex real lens distortion. In contrast, generic camera models allow for very accurate calibration due to their flexibility. Despite this, they have seen little use in practice. In this paper, we argue that this should change. We propose a calibration pipeline for generic models that is fully automated, easy to use, and can act as a drop-in replacement for parametric calibration, with a focus on accuracy. We compare our results to parametric calibrations. Considering stereo depth estimation and camera pose estimation as examples, we show that the calibration error acts as a bias on the results. We thus argue that in contrast to current common practice, generic models should be preferred over parametric ones whenever possible. To facilitate this, we released our calibration pipeline at https://github.com/puzzlepaint/camera_calibration, making both easy-to-use and accurate camera calibration available to everyone.Comment: 15 pages, 12 figures, accepted to CVPR 2020 as an ora

Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

Post-print (lokagerð höfundar)Pulsed electron paramagnetic resonance (EPR) spectroscopy is a valuable technique for the precise determination of distances between paramagnetic spin labels that are covalently attached to macromolecules. Nitroxides have commonly been utilised as paramagnetic tags for biomolecules, but trityl radicals have recently been developed as alternative spin labels. Trityls exhibit longer electron spin relaxation times and higher stability than nitroxides under in vivo conditions. So far, trityl radicals have only been used in pulsed EPR dipolar spectroscopy (PDS) at X-band (9.5 GHz), K-u-band (17.2 GHz) and Q-band (34 GHz) frequencies. In this study we investigated a trityl biradical by PDS at Q-band (34 GHz) and G-band (180 GHz) frequencies. Due to the small spectral width of the trityl (30 MHz) at Q-band frequencies, single frequency PDS techniques, like double-quantum coherence (DQC) and single frequency technique for refocusing dipolar couplings (SIFTER), work very efficiently. Hence, Q-band DQC and SIFTER experiments were performed and the results were compared; yielding a signal to noise ratio for SIFTER four times higher than that for DQC. At G-band frequencies the resolved axially symmetric g-tensor anisotropy of the trityl exhibited a spectral width of 130 MHz. Thus, pulsed electron electron double resonance (PELDOR/DEER) obtained at different pump-probe positions across the spectrum was used to reveal distances. Such a multi-frequency approach should also be applicable to determine structural information on biological macromolecules tagged with trityl spin labels.The authors acknowledge Dr Vasyl Denysenkov for the technical support with the G-band EPR spectrometer and Dr Alice Bowen for useful discussions and for proof reading the manuscript. This work is supported by SPP 1601 New Frontiers in Sensitivity for EPR Spectroscopy: from Biological Cells to Nano Materials from the German Research Society DFG, the Cluster of Excellence Frankfurt (CEF) Macromolecular Complexes and the Icelandic Research Fund (120001021), which are all gratefully acknowledged.Peer reviewe

Hemolysis at low blood flow rates: in-vitro and in-silico evaluation of a centrifugal blood pump

Background Treating severe forms of the acute respiratory distress syndrome and cardiac failure, extracorporeal membrane oxygenation (ECMO) has become an established therapeutic option. Neonatal or pediatric patients receiving ECMO, and patients undergoing extracorporeal CO2 removal (ECCO2R) represent low-flow applications of the technology, requiring lower blood flow than conventional ECMO. Centrifugal blood pumps as a core element of modern ECMO therapy present favorable operating characteristics in the high blood flow range (4 L/min–8 L/min). However, during low-flow applications in the range of 0.5 L/min–2 L/min, adverse events such as increased hemolysis, platelet activation and bleeding complications are reported frequently. Methods In this study, the hemolysis of the centrifugal pump DP3 is evaluated both in vitro and in silico, comparing the low-flow operation at 1 L/min to the high-flow operation at 4 L/min. Results Increased hemolysis occurs at low-flow, both in vitro and in silico. The in-vitro experiments present a sixfold higher relative increased hemolysis at low-flow. Compared to high-flow operation, a more than 3.5-fold increase in blood recirculation within the pump head can be observed in the low-flow range in silico. Conclusions This study highlights the underappreciated hemolysis in centrifugal pumps within the low-flow range, i.e. during pediatric ECMO or ECCO2R treatment. The in-vitro results of hemolysis and the in-silico computational fluid dynamic simulations of flow paths within the pumps raise awareness about blood damage that occurs when using centrifugal pumps at low-flow operating points. These findings underline the urgent need for a specific pump optimized for low-flow treatment. Due to the inherent problems of available centrifugal pumps in the low-flow range, clinicians should use the current centrifugal pumps with caution, alternatively other pumping principles such as positive displacement pumps may be discussed in the future

Nano-engineered electron–hole exchange interaction controls exciton dynamics in core–shell semiconductor nanocrystals

A strong electron–hole exchange interaction (EI) in semiconductor nanocrystals (NCs) gives rise to a large (up to tens of meV) splitting between optically active ('bright') and optically passive ('dark') excitons. This dark–bright splitting has a significant effect on the optical properties of band-edge excitons and leads to a pronounced temperature and magnetic field dependence of radiative decay. Here we demonstrate a nanoengineering-based approach that provides control over EI while maintaining nearly constant emission energy. We show that the dark–bright splitting can be widely tuned by controlling the electron–hole spatial overlap in core–shell CdSe/CdS NCs with a variable shell width. In thick-shell samples, the EI energy reduces to <250 μeV, which yields a material that emits with a nearly constant rate over temperatures from 1.5 to 300 K and magnetic fields up to 7 T. The EI-manipulation strategies demonstrated here are general and can be applied to other nanostructures with variable electron–hole overlap

Die Überwachung börserechtlicher Transparenzpflichten

Die börserechtlichen Transparenzpflichten sind in der Vergangenheit immer weiter ausgebaut worden und sind dadurch auch stärker in den Fokus der Aufsichtsbehörden gelangt. Auf europäischer Ebene wurden mit der MarktmissbrauchsRL im Jahr 2003 und der TransparenzRL im Jahr 2004 umfangreiche Neuerungen eingeführt, die in den EWR-Mitgliedstaaten umzusetzen waren. Das dynamische Gebiet des Kapitalmarktrechts ist auch gegenwärtig sowohl national als auch international im Fluss. Auf europäischer Ebene wird derzeit an einer neuen MarktmissbrauchsVO gearbeitet, die auf eine stärkere Vollharmonisierung abzielt. Ebenso wird die TransparenzRL derzeit novelliert, wobei der Schwerpunkt der Änderungen eindeutig im Bereich der Beteiligungspublizität liegt. Die europäischen Regelungen werden daher in den nächsten Jahren zu einer Ausweitung des Anwendungsbereichs der börserechtlichen Transparenzpflichten führen. Auch auf nationaler Ebene wird die Beteiligungspublizität ab 01.01.2013 erheblich ausgeweitet. Die Änderungen sind vor allem auf verschiedene prominente Übernahmefälle zurückzuführen, in denen feindliche Übernahmen mittels nicht meldepflichtiger Finanzinstrumente vorbereitet wurden. Neben der Schließung dieser Gesetzeslücken werden auch zusätzliche und strengere Sanktionen eingeführt sowie bestehende Reglungen auf Basis bisheriger praktischer Erfahrungen präzisiert. Die Aufsichtspraxis zeigt, dass die Auslegung der börserechtlichen Transparenzpflichten den Akteuren teilweise erhebliche Schwierigkeiten bereitet. Das liegt neben der hohen Komplexität der Regelungen oft auch an Auslegungsspielräumen oder Regelungslücken im Bereich des Börsegesetzes und den darauf basierenden Verordnungen. Teilweise sind auch die Umsetzungsspielräume europarechtlicher Grundlagen nicht richtig eingeschätzt und als Konsequenz nicht ausreichend umgesetzt worden. Die vorliegende Arbeit soll neben einem Beitrag zur Beseitigung von Unsicherheiten durch Klärung der wichtigsten praktischen Auslegungsfragen auch Anregungen und Vorschläge liefern, wie die praktische Handhabung der Rechtsgrundlagen besser gelebt werden kann. Das beinhaltet auch Anpassungsvorschläge der gesetzlichen Grundlagen. Behandelt werden neben Fragen der Behördenzuständigkeit und der anwendbaren Sprachregelungen die materiellen Bestimmungen betreffend die Beteiligungspublizität, die Ad-hoc-Meldepflichten und die Regelpublizität. Dabei wird der Meinungsstand in der österreichischen und teilweise auch deutschen Literatur, die Praxis der Aufsichtsbehörden in Österreich und Deutschland sowie die einschlägige Judikatur, auch auf europäischer Ebene, berücksichtigt. Sofern passend wird ein Vergleich zur Rechtslage in Deutschland gezogen und im Rahmen der Auslegungen des Börsegesetzes bzw für Anpassungsvorschläge berücksichtigt. Die wichtigsten auf diese Weise gewonnenen Erkenntnisse und Legistikvorschläge werden am Ende der Arbeit, zusammen mit einem Ausblick auf die Auswirkungen der bevorstehenden Änderungen auf europäischer und nationaler Ebene und einer Einschätzung möglicher Auswirkungen, zusammengefasst