120 research outputs found

    The c-projective symmetry algebras of K\"ahler surfaces

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    Let MM be a K\"ahler manifold with complex structure JJ and K\"ahler metric gg. A c-projective vector field is a vector field on MM whose flow sends JJ-planar curves to JJ-planar curves, where JJ-planar curves are analogs of what (unparametrised) geodesics are for pseudo-Riemannian manifolds without complex structure. The c-projective symmetry algebras of K\"ahler surfaces with essential (i.e., non-affine) c-projective vector fields are computed

    Metrics admitting projective and c-projective vector fields

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    Vector fields on a smooth manifold with an affine connection are called projective (resp. c-projective) if their local flows preserve geodesics (resp. J-planar curves). In this expository paper, metrics with such vector fields are discussed. Emphasis is put on Lie’s classical 1882 problem of finding a local description of surfaces with projective vector fields, known results on this problem, as well as on various extensions in the literature

    Dosage calculation for intravenous thrombolysis of ischemic stroke: to weigh or to estimate?

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    Background: Estimation is a widely used method of assessing the weight of patients with acute stroke. Because the dosage of tissue plasminogen activator (tPA) is weight-dependent, errors in estimation lead to incorrect dosing. Methods: We installed a ground-level scale in the computed tomography (CT) suite of our hospital and also integrated a scale into the CT table of our Mobile Stroke Unit in order to prospectively assess the differences between reported, estimated, and measured weights of acute stroke patients. An independent rater asked patients to report their weight. The patients’ weights were also estimated by the treating physician and measured with a scale. Differences between reported, estimated, and measured weights were analyzed statistically. Results: For 100 consecutive patients, weighing was possible without treatment delays. Weights estimated by the physician diverged from measured weights by 10% or more for 27 patients and by 20% or more for 6 patients. Weights reported by the patient diverged from measured weights by 10% or more for 12 patients. Weights reported by the patients differed significantly less from measured weights (mean, 4.1 ± 3.1 kg) than did weights estimated by the physician (5.7 ± 4.4 kg; p = 0.003). Conclusion: This first prospective study of weight assessment in acute stroke shows that the use of an easily accessible scale makes it feasible to weigh patients with acute stroke without the treatment delay associated with additional patient transfers. Physicians’ estimates of patients’ weights demonstrated substantial aberrations from measured weights. Avoiding these deviations would improve the accuracy of tPA dosag

    Driven electronic bridge processes via defect states in 229^{229}Th-doped crystals

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    The electronic defect states resulting from doping 229^{229}Th in CaF2_2 offer a unique opportunity to excite the nuclear isomeric state 229m^{229m}Th at approximately 8 eV via electronic bridge mechanisms. We consider bridge schemes involving stimulated emission and absorption using an optical laser. The role of different multipole contributions, both for the emitted or absorbed photon and nuclear transition, to the total bridge rates are investigated theoretically. We show that the electric dipole component is dominant for the electronic bridge photon. In contradistinction, the electric quadrupole channel of the 229^{229}Th isomeric transition plays the dominant role for the bridge processes presented. The driven bridge rates are discussed in the context of background signals in the crystal environment and of implementation methods. We show that inverse electronic bridge processes quenching the isomeric state population can improve the performance of a solid-state nuclear clock based on 229m^{229m}Th

    Effects of state-wide implementation of the Los Angeles Motor Scale for triage of stroke patients in clinical practice

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    Background: The prehospital identification of stroke patients with large-vessel occlusion (LVO), that should be immediately transported to a thrombectomy capable centre is an unsolved problem. Our aim was to determine whether implementation of a state-wide standard operating procedure (SOP) using the Los Angeles Motor Scale (LAMS) is feasible and enables correct triage of stroke patients to hospitals offering (comprehensive stroke centres, CSCs) or not offering (primary stroke centres, PSCs) thrombectomy.Methods: Prospective study involving all patients with suspected acute stroke treated in a 4-month period in a state-wide network of all stroke-treating hospitals (eight PSCs and two CSCs). Primary endpoint was accuracy of the triage SOP in correctly transferring patients to CSCs or PSCs. Additional endpoints included the number of secondary transfers, the accuracy of the LAMS for detection of LVO, apart from stroke management metrics.Results: In 1123 patients, use of a triage SOP based on the LAMS allowed triage decisions according to LVO status with a sensitivity of 69.2% (95% confidence interval (95%-CI): 59.0-79.5%) and a specificity of 84.9% (95%-CI: 82.6-87.3%). This was more favourable than the conventional approach of transferring every patient to the nearest stroke-treating hospital, as determined by geocoding for each patient (sensitivity, 17.9% (95%-CI: 9.4-26.5%); specificity, 100% (95%-CI: 100-100%)). Secondary transfers were required for 14 of the 78 (17.9%) LVO patients. Regarding the score itself, LAMS detected LVO with a sensitivity of 67.5% (95%-CI: 57.1-78.0%) and a specificity of 83.5% (95%-CI: 81.0-86.0%).Conclusions: State-wide implementation of a triage SOP requesting use of the LAMS tool is feasible and improves triage decision-making in acute stroke regarding the most appropriate target hospital.</p

    Urological cancer care pathways: development and use in the context of systematic reviews and clinical practice guidelines

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    Background: Making healthcare treatment decisions is a complex process involving a broad stakeholder base including patients, their families, health professionals, clinical practice guideline developers and funders of healthcare. Methods: This paper presents a review of a methodology for the development of urological cancer care pathways (UCAN care pathways), which reflects an appreciation of this broad stakeholder base. The methods section includes an overview of the steps in the development of the UCAN care pathways and engagement with clinical content experts and patient groups. Results: The development process is outlined, the uses of the urological cancer care pathways discussed and the implications for clinical practice highlighted. The full set of UCAN care pathways is published in this paper. These include care pathways on localised prostate cancer, locally advanced prostate cancer, metastatic prostate cancer, hormone-resistant prostate cancer, localised renal cell cancer, advanced renal cell cancer, testicular cancer, penile cancer, muscle invasive and metastatic bladder cancer and non-muscle invasive bladder cancer. Conclusion: The process provides a useful framework for improving urological cancer care through evidence synthesis, research prioritisation, stakeholder involvement and international collaboration. Although the focus of this work is urological cancers, the methodology can be applied to all aspects of urology and is transferable to other clinical specialties.11 page(s

    Kriterien für die Auswahl einer Softwarelösung für den Betrieb eines Repositoriums für Forschungsdaten

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    Die öffentliche Bereitstellung von Forschungsdaten zur Nachnutzung im Sinne von Open Science ist Bestandteil des Lebenszyklus von Forschungsdaten und erlangt zunehmende Relevanz. Eine zitierbare Veröffentlichung dieser Daten zeugt von einer transparenten Forschung, belegt die Forschungsleistung eines Forschenden sowie der jeweiligen Einrichtung und macht Forschung reproduzierbar und damit überprüfbar. Forschungsförderer erwarten bereits bei der Antragstellung die Dokumentation und Planung eines umsichtigen und nachhaltigen Umgangs mit Forschungsdaten, bspw. in Form eines Datenmanagementplans, der unter anderem Angaben zu geplanten Lizenzen für Forschungsdaten, Rechten an Daten etc. enthält. Die Umsetzung des Datenmanagementplans ist ein kontinuierlicher Prozess im Laufe eines Projekts und nicht auf eine Datenveröffentlichung zum Projektende hin beschränkt. Der Umgang mit Forschungsdaten wird unter anderem in den Richtlinien Guter Wissenschaftlicher Praxis[1], den Open-Access-Policies von Hochschulen, Forschungsinstituten und Forschungsförderern sowie in den “Data Policies” von Zeitschriften adressiert. Repositorien bilden das technische Grundgerüst für das Forschungsdatenmanagement, da sie den gesamten Prozess von der Übernahme über die Qualitätskontrolle bis hin zur zitierfähigen Veröffentlichung unterstützen. Softwarelösungen für Repositorien sind für unterschiedliche Zwecke und Einsatzszenarien verfügbar. Zu den verbreitetsten zählen beispielsweise Fedora, DSpace, MyCoRe, Islandora, EPrints, Dataverse, Rosetta, Archivematica und Invenio. Die Bestimmung von Kriterien für die Auswahl eines Repositoriums ist nicht trivial und es müssen neben Aspekten der Wirtschaftlichkeit, Skalierbarkeit und Funktionalität noch weitere Kriterien wie die Dokumentation, Verbreitung, Entwicklungsperspektive sowie das Daten- und Lizenzmodell berücksichtigt werden. Der Aufwand für die Erarbeitung eines Kriterienkatalogs darf nicht unterschätzt werden. Im Folgenden bezeichnet Repositorium eine Softwarelösung, die - eingebettet in eine Organisationsstruktur und gegebenenfalls im Kontext weiterer Systeme - Forschungsdaten übernimmt, verwaltet und publiziert. Daraus ergeben sich zwangsläufig Abhängigkeiten zur betreibenden organisatorischen Einheit und der grundlegenden technischen Infrastruktur für den Betrieb der Software und die Speicherung der Daten. In diesem Artikel werden verschiedene Aspekte präsentiert, die für den Auswahlprozess potentiell relevant sind. [1] Siehe auch Kodex der DFG zur guten wissenschaftlichen Praxis: https://www.dfg.de/foerderung/grundlagen_rahmenbedingungen/gwp

    Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

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    A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements
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