Remote sensing of red and far-red sun-induced chlorophyll fluorescence to estimate gross primary productivity and plant stress in sugar beet

Ohne den Prozess der Photosynthese wäre das Leben auf der Erde, so wie wir es kennen, nicht möglich. Die Quantifizierung des Photosynthese-Prozesses und die Darstellung seiner räumlichen und zeitlichen Adaptierung ist eine der zentralen Herausforderungen in der terrestrischen Umweltforschung. Von Pflanzen absorbiertes Licht kann für den Photosynthese Prozess genutzt, oder aber auch in Form von Wärme (nichtphotochemisches Quenching, NPQ) oder als Fluoreszenz abgegeben werden. Jüngste Fortschritte in der Sensorentechnik ermöglichen es nun, die von der Vegetation emittierte, sonneninduzierte Chlorophyll Fluoreszenz (F) mit Fernerkundungsmethoden zu erfassen. Aufgrund der direkten physikalischen Verbindung zwischen Fluoreszenz und Photosynthese eröffnen sich dadurch neue Möglichkeiten, die Photosynthese-Leistung (normalerweise beschrieben als brutto Primärproduktion, GPP) räumlich und zeitlich zu quantifizieren und Pflanzenstress zu bestimmen. In dieser Dissertation wurden neuartigen boden- (SIF-Sys) und flugzeuggestützte (HyPlant) gestützten Messsysteme genutzt, um die zeitlichen und räumlichen Beziehungen zwischen F, dem photochemischen Reflexionsindex (PRI – als Indikator für NPQ) und der Lichtnutzungseffizienz (LUE) unter wechselnden Umweltbedingungen zu analysieren. Dabei hat sich gezeigt, dass die Kombination aus roter und fern-roter Fluoreszenz Effizienz (F687yield und F760yield) und dem PRI 65% der täglichen und 89% der saisonalen Variabilität der LUE von Zuckerrübe erklärt. Zusätzlich wurden flugzeuggestützte Messungen genutzt, um die räumliche und zeitliche Variabilität von F760yield, F680yield, dem Verhältnis zwischen roter und fern-roter Fluoreszenz (Fratio) und dem sogenannten verbesserten Vegetationsindex (EVI) innerhalb eines Flugstreifens und eines Tages zu bestimmen. Die Ergebnisse zeigen in Abhängigkeit zur Wasserverfügbarkeit eine hohe Variabilität von F760yield und Fratio im Laufe eines Tages und hinsichtlich der Feldfruchtart. Dies deutet darauf hin, dass Fluoreszenz-Produkte sensitiv auf Pflanzenstress reagieren. Die oben beschriebenen Ergebnisse wurden genutzt, um ein empirisches GPP Modell zu entwickeln, das auf F760yield, F687yield und PRI basiert. Die Ergebnisse wurden anschließend mit GPP-Werten, die aus Eddy Kovarianz Messungen (GPPEC) abgeleitet wurden, validiert und mit den Ergebnissen dreier derzeitig genutzten Modellen verglichen, die auf Fluoreszenz und Reflexion basieren. Die Ergebnisse zeigen, dass das neuentwickelte Modell, welches auf Fyield und PRI Informationen basiert, die Tages- und saisonale Variabilität von GPP am besten bestimmt. Die Anwendung der Modelle auf räumlich aufgelöste Daten zeigt, dass generell fluoreszenzbasierte Modelle die räumliche Variabilität von GPP besser erfassen als das Modell, welches allein auf Reflexionsindizes basiert. Abschließend wird der Entwurf für ein Modell vorgeschlagen, welches, basierend auf der photosynthetischen Energiebilanz, den PRI und die absolute Fluoreszenz (Ftot) nutzt, um GPP in einer stärkeren prozessorientierten weise zu bestimmen. Zusammengefasst stellt diese Arbeit heraus, dass sonneninduzierte Fluoreszenz die Abschätzung von GPP verbessert, wobei insbesondere die Kombination aus F und PRI die vielversprechendsten Ergebnisse liefert. Zusätzlich wird gezeigt, dass das Verhältnis von roter zu fern-roter Fluoreszenz sowie Fyield ein großes Potenzial haben, um stressbedingte raum-zeitlichen Pflanzenanpassungsstrategien abzubilden

Performance Measures for Social CRM: A Literature Review

Social CRM deals with the integration of Web 2.0 and Social Media into Customer Relationship Management (CRM). Social CRM is a business strategy supported by technology platforms to provide mutually beneficial value for companies and their target groups. In practice, one factor impeding Social CRM implementation is the lack of performance measures, which assess Social CRM activities and monitor their success. Little research has been conducted investigating performance measures in order to develop a Social CRM performance measurement model. To address this gap, this article presents the qualitative part of a two-stage multi-method approach. It comprises a systematic and rigorous literature review as well as a sorting procedure. In this effort, 16 Social CRM performance measures and four categories of a performance measurement system are identified. The sorting procedure validates the corresponding classification and ensures a high degree of external validity. In a subsequent study, formative survey instruments are developed from the respective findings and are tested by applying a confirmatory factor analysis

Spatial variability of aircraft-measured surface energy fluxes in permafrost landscapes

Arctic ecosystems are undergoing a very rapid change due to global warming and their response to climate change has important implications for the global energy budget. Therefore, it is crucial to understand how energy fluxes in the Arctic will respond to any changes in climate related parameters. However, attribution of these responses is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. Here, we present the potential of environmental response functions for quantitatively linking energy flux observations over high latitude permafrost wetlands to environmental drivers in the flux footprints. We used the research aircraft POLAR 5 equipped with a turbulence probe and fast temperature and humidity sensors to measure turbulent energy fluxes along flight tracks across the Alaskan North Slope with the aim to extrapolate the airborne eddy covariance flux measurements from their specific footprint to the entire North Slope. After thorough data pre-processing, wavelet transforms are used to improve spatial discretization of flux observations in order to relate them to biophysically relevant surface properties in the flux footprint. Boosted regression trees are then employed to extract and quantify the functional relationships between the energy fluxes and environmental drivers. Finally, the resulting environmental response functions are used to extrapolate the sensible heat and water vapor exchange over spatio-temporally explicit grids of the Alaskan North Slope. Additionally, simulations from the Weather Research and Forecasting (WRF) model were used to explore the dynamics of the atmospheric boundary layer and to examine results of our extrapolation

Measuring Social CRM Performance: A Preliminary Measurement Model

Social Customer Relationship Management (Social CRM) deals with the integration of Web 2.0 and Social Media into CRM. Social CRM is a business strategy supported by technology platforms in order to provide mutually beneficial value for both companies and customers. Gartner has identified Social CRM as one of the top innovation-triggered themes in 2013 [1]. In this context, a constraining factor regarding the implementation of Social CRM and the achievement of its objectives is the lack of an appropriate performance measurement model. Little research has been conducted on the relevant performance factors and Social CRM performance measurement models. To address this gap, the article presents the qualitative part of a two-stage multi-method approach. It comprises findings from a literature review, 15 semi-structured interviews and a consolidation procedure. A preliminary Social CRM performance measurement model is developed containing four performance dimensions, 25 classified Social CRM performance factors and corresponding performance measures

Erfolgsfaktoren von On-Demand-Enterprise-Systemen aus der Sicht des Anbieters – eine explorative Studie

Diese Arbeit thematisiert erfolgsrelevante Aspekte für On-Demand-Enterprise-Systeme aus Sicht eines Serviceanbieters. Auf Basis der Forschungsfrage: „Inwiefern bieten in Abgrenzung zu konventionellen On-Premise-Lösungen On-Demand-Enterprise-Systeme Vorteile für Unternehmen“ reduziert die Studie die Wissenslücke bezüglich der Erfolgsfaktoren dieses speziellen Serviceangebotes. Anhand 12 explorativer Interviews mit Experten des führenden deutschen Softwareherstellers werden 17 Erfolgsfaktoren identifiziert und detailliert erläutert. Zur Kategorisierung der Erfolgsfaktoren werden diese dem “IS-Success Model” von DeLone und McLean zugeordnet. Dabei wird verdeutlicht, dass das Potenzial von On-Demand-Enterprise-Systemen sich nicht nur auf reine Kostensenkungsmaßnahmen reduzieren lässt. Wesentliche Erfolgsfaktoren finden sich vielmehr in dem Wirkungsfeld von höherer Flexibilität und Einfachheit. Dem Kunden respektive den Unternehmungen können sich somit durch den Einsatz von Cloud-Applikationen neue strategische Optionen bieten

Variability of surface energy fluxes over high latitude permafrost wetlands

Variability of surface energy fluxes over high latitude permafrost wetlands A. Serafimovich (1), S. Metzger (2,3), J. Hartmann (4), S. Wieneke (5), and T. Sachs (1) (1) GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany ([email protected]), (2) National Ecological Observatory Network, 1685 38th Street, Boulder, CO 80301, USA, (3) University of Colorado, 1560 30th Street, Boulder, CO 80303, USA, (4) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, (5) Institute of Geophysics and Meteorology, Cologne University, 50969 Cologne, Germany Arctic ecosystems are undergoing a very rapid change due to global warming and their response to climate change has important implications for the global energy budget. Therefore, it is crucial to understand how energy fluxes in the Arctic will respond to any changes in climate related parameters. However, attribution of these responses is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. Ground-based measurements of surface fluxes provide continuous in-situ observations of the surface-atmosphere exchange. But these observations may be non-representative, because of spatial and temporal heterogeneity, indicating that local observations cannot easily be extrapolated to represent global scales. Airborne eddy covariance measurements across large areas can reduce uncertainty and improve spatial coverage and spatial representativeness of flux estimates. Here, we present the potential of environmental response functions for quantitatively linking energy flux observations over high latitude permafrost wetlands to environmental drivers in the flux footprints.We used the research aircraft POLAR 5 equipped with a turbulence probe, fast temperature and humidity sensors to measure turbulent energy fluxes across the Alaskan North Slope. We used wavelet transforms of the original high-frequency data, which enable much improved spatial discretization of the flux observations, and determine biophysically relevant land cover properties in the flux footprint. A boosted regression trees technique is then employed to extract and quantify the functional relationships between energy fluxes and environmental drivers. Using extracted environmental response functions and supplemented simulations from the Weather Research and Forecasting (WRF) model the surface energy fluxes were then projected beyond measurement footprints across North Slope of Alaska

Sun-induced chlorophyll fluorescence II:Review of passive measurement setups, protocols, and their application at the leaf to canopy level

Satellite gravimetry allows for determining large scale mass transport in the system Earth and to quantify ice mass change in polar regions. We provide, evaluate and compare a long time-series of monthly gravity field solutions derived either by satellite laser ranging (SLR) to geodetic satellites, by GPS and K-band observations of the GRACE mission, or by GPS observations of the three Swarm satellites. While GRACE provides gravity signal at the highest spatial resolution, SLR sheds light on mass transport in polar regions at larger scales also in the pre- and post-GRACE era. To bridge the gap between GRACE and GRACE Follow-On, we also derive monthly gravity fields using Swarm data and perform a combination with SLR. To correctly take all correlations into account, this combination is performed on the normal equation level. Validating the Swarm/SLR combination against GRACE during the overlapping period January 2015 to June 2016, the best fit is achieved when down-weighting Swarm compared to the weights determined by variance component estimation. While between 2014 and 2017 SLR alone slightly overestimates mass loss in Greenland compared to GRACE, the combined gravity fields match significantly better in the overlapping time period and the RMS of the differences is reduced by almost 100 Gt. After 2017, both SLR and Swarm indicate moderate mass gain in Greenland

Reliability of human retina organoid generation from hiPSC-derived neuroepithelial cysts

The possible applications for human retinal organoids (HROs) derived from human induced pluripotent stem cells (hiPSC) rely on the robustness and transferability of the methodology for their generation. Standardized strategies and parameters to effectively assess, compare, and optimize organoid protocols are starting to be established, but are not yet complete. To advance this, we explored the efficiency and reliability of a differentiation method, called CYST protocol, that facilitates retina generation by forming neuroepithelial cysts from hiPSC clusters. Here, we tested seven different hiPSC lines which reproducibly generated HROs. Histological and ultrastructural analyses indicate that HRO differentiation and maturation are regulated. The different hiPSC lines appeared to be a larger source of variance than experimental rounds. Although previous reports have shown that HROs in several other protocols contain a rather low number of cones, HROs from the CYST protocol are consistently richer in cones and with a comparable ratio of cones, rods, and Müller glia. To provide further insight into HRO cell composition, we studied single cell RNA sequencing data and applied CaSTLe, a transfer learning approach. Additionally, we devised a potential strategy to systematically evaluate different organoid protocols side-by-side through parallel differentiation from the same hiPSC batches: In an explorative study, the CYST protocol was compared to a conceptually different protocol based on the formation of cell aggregates from single hiPSCs. Comparing four hiPSC lines showed that both protocols reproduced key characteristics of retinal epithelial structure and cell composition, but the CYST protocol provided a higher HRO yield. So far, our data suggest that CYST-derived HROs remained stable up to at least day 200, while single hiPSC-derived HROs showed spontaneous pathologic changes by day 200. Overall, our data provide insights into the efficiency, reproducibility, and stability of the CYST protocol for generating HROs, which will be useful for further optimizing organoid systems, as well as for basic and translational research applications

The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory

We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than $60^\circ$, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the ~2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.Comment: 20 pages, 14 figure

Particle Reconstruction with Optical Transfer Functions Applied to Tomo-PIV-Experiments

A new approach to the weighting function, which describes particle imaging in the reconstruction process of tomographic PIV, is introduced. Instead of assuming a spatially homogeneous mapping function of a voxel to the images, a variable optical transfer function (OTF) is applied. By this method, the effects of optical distor-tions, introduced during the recording process, can be reduced considerably. The effect of blurred particle imaging and astigmatisms on reconstruction and correlation quality is investigated via simulated data. Reconstructions using a spa-tially varying OTF, calibrated to the imaging conditions, show a significant im-provement in reconstruction quality, correlation quality and accuracy of the particle peak position. First results on experimental data indicate a distinct reduc-tion in ghost particle intensity compared to other approaches