@phdthesis{Schramm2006, author = {Schramm, Claudia}, title = {Ultraschneller Ladungstransfer und Energierelaxation an Grenzfl{\"a}chen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-18344}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2006}, abstract = {Ziel der vorliegenden Arbeit ist es, den ultraschnellen Transport und die Energierelaxation von Ladungstr{\"a}gern an der Grenzfl{\"a}che von heterogenen Systemen zu untersuchen. Dabei wird gezeigt, dass zeitaufgel{\"o}ste Zweifarb-Mehrphotonen-Photoemissionsspektroskopie eine gute Methode ist, um Einblick in das Relaxationsverhalten und den dynamischen Ladungstr{\"a}gertransport in den untersuchten Systemen zu erhalten. Es werden Messungen an zwei unterschiedlichen Systemen vorgestellt: Silbernanoteilchen auf Graphit und ultrad{\"u}nne Silberfilme auf Silizium. Die Untersuchung von heterogenen Systemen erfordert einen selektiven Photoemissionsprozess, d.h. es muss m{\"o}glich sein, Photoemission von den Nanoteilchen bzw. vom Silberfilm und vom Substrat zu trennen. F{\"u}r Silbernanoteilchen auf Graphit kann dies erreicht werden, indem die Abfragewellenl{\"a}nge auf die Resonanz des Plasmon-Polaritons abgestimmt wird. So erh{\"a}lt man dominant Photoemission von den Nanoteilchen, Photoemission vom Graphit kann dagegen vernachl{\"a}ssigt werden. Die transiente Elektronenverteilung in den Nanoteilchen kann aus der Form der Photoemissionsspektren bestimmt werden. Die transiente Verschiebung der Spektren gibt Aufschluss {\"u}ber die Auf- oder Entladung des Nanoteilchens. Dadurch wird es hier m{\"o}glich, zeitaufgel{\"o}ste Photoemissionsspektroskopie als ultraschnelle Sonde im Nanometerbereich zu verwenden. Zusammen mit einem Modell f{\"u}r die Relaxation und den Ladungstransfer ist es m{\"o}glich, quantitative Ergebnisse f{\"u}r die Kopplung zwischen Nanoteilchen und Substrat zu erhalten. Das vorgestellte semiempirische Modell enth{\"a}lt dabei zus{\"a}tzlich zu Termen f{\"u}r die Relaxation in Nanoteilchen und Substrat die M{\"o}glichkeit eines zeitabh{\"a}ngigen Ladungstransfers zwischen Teilchen und Substrat. Die Kopplung wird durch eine Tunnelbarriere beschrieben, deren starke Energieabh{\"a}ngigkeit der Transferwahrscheinlichkeit die experimentellen Ergebnisse gut wiedergibt. Die St{\"a}rke des Ladungstransfers und das zeitabh{\"a}ngige Verhalten sind dabei stark von den gew{\"a}hlten Parametern f{\"u}r die Tunnelbarriere abh{\"a}ngig. Insbesondere zeigt der Vergleich der Simulationsergebnisse mit dem Experiment, dass transienter Ladungstransfer ein wichtiger Effekt ist und die K{\"u}hlungsdynamik, die im Elektronengas der Nanoteilchen beobachtet wird, wesentlich beeinflusst. Auch im Fall der ultrad{\"u}nnen Silberfilme auf Silizium ist es durch gezielte Wahl der Wellenl{\"a}ngen m{\"o}glich, die Photoelektronenausbeute selektiv dem Silberfilm oder dem Siliziumsubstrat zuzuordnen. Bei Anregung mit 3.1 eV Photonenenergie dominiert Photoemission aus dem Silberfilm, w{\"a}hrend es bei Anregung mit 4.65 eV m{\"o}glich ist, Informationen {\"u}ber die Grenzschicht und das Siliziumsubstrat zu erhalten. Intensit{\"a}tsabh{\"a}ngige Messungen zeigen den Einfluss der optischen Anregung auf den Verlauf der Schottkybarriere an der Metall-Halbleiter-Grenzschicht. Dieser Effekt ist als Oberfl{\"a}chen-Photospannung bekannt. Die Anregung mit 4.65 eV Photonenenergie bewirkt zus{\"a}tzlich eine S{\"a}ttigung langlebiger Zust{\"a}nde an der Metall-Halbleiter-Grenzfl{\"a}che, was zu einer linearen Abh{\"a}ngigkeit der Photoemissionsausbeute von der Laserfluenz f{\"u}hrt. Zeitaufgel{\"o}ste Zweifarb-Mehrphotonen-Photoemissionsmessungen machen es m{\"o}glich, die Elektronendynamik an der Metall-Halbleiter-Grenzschicht und im Siliziumsubstrat zu untersuchen. Das Relaxationsverhalten der Ladungstr{\"a}ger zeigt dabei eine komplexe Dynamik, die auf die Anregung von Ladungstr{\"a}gern in unterschiedlichen Bereichen zur{\"u}ckgef{\"u}hrt werden kann. Dabei dominiert f{\"u}r verschiedene Zwischenzustandsenergien die Dynamik entweder aus dem Film, der Grenzschicht oder dem Siliziumsubstrat, so dass das Relaxationsverhalten grob in drei unterschiedliche Energiebereiche eingeteilt werden kann. Im Silizium k{\"o}nnen aufgrund der Bandl{\"u}cke mit 3.1 eV Photonenenergie Elektronen nur bis zu Zwischenzustandsenergien von EF + 2.0 eV angeregt werden. In der Tat stimmen die Relaxationszeiten, die man in diesem Bereich aus den zeitaufgel{\"o}sten Messungen bestimmt, mit Werten von reinen Siliziumsubstraten {\"u}berein. F{\"u}r Zwischenzustandsenergien oberhalb von EF + 2.0 eV findet man {\"u}berwiegend Anregung im Silberfilm. Die Relaxationszeiten f{\"u}r diese Energien entsprechen Werten von Silberfilmen auf einem isolierenden Substrat. F{\"u}r sehr niedrige Zwischenzustandsenergien unterhalb von EF + 0.6 eV sind die Zust{\"a}nde wegen der vorliegenden experimentellen Bedingungen permanent besetzt. Der Anregepuls regt Elektronen aus diesen Zust{\"a}nden an und f{\"u}hrt daher in diesem Bereich zu einer Reduktion der Besetzung nach der Anregung mit Licht. Die Zeitkonstante f{\"u}r die Wiederbesetzung liegt im Bereich von mehreren 100 ps bis Nanosekunden. Solch lange Zeiten sind aus Rekombinationsprozessen an der Dipolschicht von Metall-Halbleiter-Grenzfl{\"a}chen bekannt. Zeitaufgel{\"o}ste Mehrphotonen-Photoemissionsspektroskopie ist also sehr gut geeignet, das komplexe Relaxationsverhalten und den Ladungstr{\"a}gertransfer an der Grenzfl{\"a}che eines Schichtsystems zu untersuchen.}, subject = {Elektronischer Transport}, language = {de} } @article{AsoHerbOguetaetal.2012, author = {Aso, Yoshinori and Herb, Andrea and Ogueta, Maite and Siwanowicz, Igor and Templier, Thomas and Friedrich, Anja B. and Ito, Kei and Scholz, Henrike and Tanimoto, Hiromu}, title = {Three Dopamine Pathways Induce Aversive Odor Memories with Different Stability}, series = {PLoS Genetics}, volume = {8}, journal = {PLoS Genetics}, number = {7}, doi = {10.1371/journal.pgen.1002768}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-130631}, pages = {e1002768}, year = {2012}, abstract = {Animals acquire predictive values of sensory stimuli through reinforcement. In the brain of Drosophila melanogaster, activation of two types of dopamine neurons in the PAM and PPL1 clusters has been shown to induce aversive odor memory. Here, we identified the third cell type and characterized aversive memories induced by these dopamine neurons. These three dopamine pathways all project to the mushroom body but terminate in the spatially segregated subdomains. To understand the functional difference of these dopamine pathways in electric shock reinforcement, we blocked each one of them during memory acquisition. We found that all three pathways partially contribute to electric shock memory. Notably, the memories mediated by these neurons differed in temporal stability. Furthermore, combinatorial activation of two of these pathways revealed significant interaction of individual memory components rather than their simple summation. These results cast light on a cellular mechanism by which a noxious event induces different dopamine signals to a single brain structure to synthesize an aversive memory.}, language = {en} } @article{PoethkePfenningHovestadt2007, author = {Poethke, Hans J. and Pfenning, Brenda and Hovestadt, Thomas}, title = {The relative contribution of individual and kin selection to the evolution of density-dependent dispersal rates}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48225}, year = {2007}, abstract = {Questions: What are the relative contributions of kin selection and individual selection to the evolution of dispersal rates in fragmented landscapes? How do environmental parameters influence the relative contributions of both evolutionary forces? Features of the model: Individual-based simulation model of a metapopulation. Logistic local growth dynamics and density-dependent dispersal. An optional shuffling algorithm allows the continuous destruction of any genetic structure in the metapopulation. Ranges of key variables: Depending on dispersal mortality (0.05-0.4) and the strength of environmental fluctuations, mean dispersal probability varied between 0.05 and 0.5. Conclusions: For local population sizes of 100 individuals, kin selection alone could account for dispersal probabilities of up to 0.1. It may result in a ten-fold increase of optimal dispersal rates compared with those predicted on the basis of individual selection alone. Such a substantial contribution of kin selection to dispersal is restricted to cases where the overall dispersal probabilities are small (textless 0.1). In the latter case, as much as 30\% of the total fitness of dispersing individuals could arise from the increased reproduction of kin left in the natal patch.}, language = {en} } @article{ReinersSobrinoKuenzer2023, author = {Reiners, Philipp and Sobrino, Jos{\´e} and Kuenzer, Claudia}, title = {Satellite-derived land surface temperature dynamics in the context of global change — a review}, series = {Remote Sensing}, volume = {15}, journal = {Remote Sensing}, number = {7}, issn = {2072-4292}, doi = {10.3390/rs15071857}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-311120}, year = {2023}, abstract = {Satellite-derived Land Surface Temperature (LST) dynamics have been increasingly used to study various geophysical processes. This review provides an extensive overview of the applications of LST in the context of global change. By filtering a selection of relevant keywords, a total of 164 articles from 14 international journals published during the last two decades were analyzed based on study location, research topic, applied sensor, spatio-temporal resolution and scale and employed analysis methods. It was revealed that China and the USA were the most studied countries and those that had the most first author affiliations. The most prominent research topic was the Surface Urban Heat Island (SUHI), while the research topics related to climate change were underrepresented. MODIS was by far the most used sensor system, followed by Landsat. A relatively small number of studies analyzed LST dynamics on a global or continental scale. The extensive use of MODIS highly determined the study periods: A majority of the studies started around the year 2000 and thus had a study period shorter than 25 years. The following suggestions were made to increase the utilization of LST time series in climate research: The prolongation of the time series by, e.g., using AVHRR LST, the better representation of LST under clouds, the comparison of LST to traditional climate change measures, such as air temperature and reanalysis variables, and the extension of the validation to heterogenous sites.}, language = {en} } @article{SognoKleinKuenzer2022, author = {Sogno, Patrick and Klein, Igor and Kuenzer, Claudia}, title = {Remote sensing of surface water dynamics in the context of global change — a review}, series = {Remote Sensing}, volume = {14}, journal = {Remote Sensing}, number = {10}, issn = {2072-4292}, doi = {10.3390/rs14102475}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-275274}, year = {2022}, abstract = {Inland surface water is often the most accessible freshwater source. As opposed to groundwater, surface water is replenished in a comparatively quick cycle, which makes this vital resource — if not overexploited — sustainable. From a global perspective, freshwater is plentiful. Still, depending on the region, surface water availability is severely limited. Additionally, climate change and human interventions act as large-scale drivers and cause dramatic changes in established surface water dynamics. Actions have to be taken to secure sustainable water availability and usage. This requires informed decision making based on reliable environmental data. Monitoring inland surface water dynamics is therefore more important than ever. Remote sensing is able to delineate surface water in a number of ways by using optical as well as active and passive microwave sensors. In this review, we look at the proceedings within this discipline by reviewing 233 scientific works. We provide an extensive overview of used sensors, the spatial and temporal resolution of studies, their thematic foci, and their spatial distribution. We observe that a wide array of available sensors and datasets, along with increasing computing capacities, have shaped the field over the last years. Multiple global analysis-ready products are available for investigating surface water area dynamics, but so far none offer high spatial and temporal resolution.}, language = {en} } @article{KuenzerKleinUllmannetal.2015, author = {Kuenzer, Claudia and Klein, Igor and Ullmann, Tobias and Georgiou, Efi Foufoula and Baumhauer, Roland and Dech, Stefan}, title = {Remote Sensing of River Delta Inundation: Exploiting the Potential of Coarse Spatial Resolution, Temporally-Dense MODIS Time Series}, series = {Remote Sensing}, volume = {7}, journal = {Remote Sensing}, doi = {10.3390/rs70708516}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-151552}, pages = {8516 -- 8542}, year = {2015}, abstract = {River deltas belong to the most densely settled places on earth. Although they only account for 5\% of the global land surface, over 550 million people live in deltas. These preferred livelihood locations, which feature flat terrain, fertile alluvial soils, access to fluvial and marine resources, a rich wetland biodiversity and other advantages are, however, threatened by numerous internal and external processes. Socio-economic development, urbanization, climate change induced sea level rise, as well as flood pulse changes due to upstream water diversion all lead to changes in these highly dynamic systems. A thorough understanding of a river delta's general setting and intra-annual as well as long-term dynamic is therefore crucial for an informed management of natural resources. Here, remote sensing can play a key role in analyzing and monitoring these vast areas at a global scale. The goal of this study is to demonstrate the potential of intra-annual time series analyses at dense temporal, but coarse spatial resolution for inundation characterization in five river deltas located in four different countries. Based on 250 m MODIS reflectance data we analyze inundation dynamics in four densely populated Asian river deltas-namely the Yellow River Delta (China), the Mekong Delta (Vietnam), the Irrawaddy Delta (Myanmar), and the Ganges-Brahmaputra (Bangladesh, India)-as well as one very contrasting delta: the nearly uninhabited polar Mackenzie Delta Region in northwestern Canada for the complete time span of one year (2013). A complex processing chain of water surface derivation on a daily basis allows the generation of intra-annual time series, which indicate inundation duration in each of the deltas. Our analyses depict distinct inundation patterns within each of the deltas, which can be attributed to processes such as overland flooding, irrigation agriculture, aquaculture, or snowmelt and thermokarst processes. Clear differences between mid-latitude, subtropical, and polar deltas are illustrated, and the advantages and limitations of the approach for inundation derivation are discussed.}, language = {en} } @article{DuerigGudmundssonKarmannetal.2015, author = {D{\"u}rig, Tobias and Gudmundsson, Magn{\´u}s Tumi and Karmann, Sven and Zimanowski, Bernd and Dellino, Pierfrancesco and Rietze, Martin and B{\"u}ttner, Ralf}, title = {Mass eruption rates in pulsating eruptions estimated from video analysis of the gas thrust-buoyancy transition-a case study of the 2010 eruption of Eyjafjallaj{\"o}kull, Iceland}, series = {Earth, Planets and Space}, volume = {67}, journal = {Earth, Planets and Space}, number = {180}, doi = {10.1186/s40623-015-0351-7}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-138635}, year = {2015}, abstract = {The 2010 eruption of Eyjafjallajokull volcano was characterized by pulsating activity. Discrete ash bursts merged at higher altitude and formed a sustained quasi-continuous eruption column. High-resolution near-field videos were recorded on 8-10 May, during the second explosive phase of the eruption, and supplemented by contemporary aerial observations. In the observed period, pulses occurred at intervals of 0.8 to 23.4 s (average, 4.2 s). On the basis of video analysis, the pulse volume and the velocity of the reversely buoyant jets that initiated each pulse were determined. The expansion history of jets was tracked until the pulses reached the height of transition from a negatively buoyant jet to a convective buoyant plume about 100 m above the vent. Based on the assumption that the density of the gas-solid mixture making up the pulse approximates that of the surrounding air at the level of transition from the jet to the plume, a mass flux ranging between 2.2 and 3.5 . 10\(^4\) kg/s was calculated. This mass eruption rate is in good agreement with results obtained with simple models relating plume height with mass discharge at the vent. Our findings indicate that near-field measurements of eruption source parameters in a pulsating eruption may prove to be an effective monitoring tool. A comparison of the observed pulses with those generated in calibrated large-scale experiments reveals very similar characteristics and suggests that the analysis of near-field sensors could in the future help to constrain the triggering mechanism of explosive eruptions.}, language = {en} } @article{KleinStieglerKleinetal.2014, author = {Klein, Barett Anthony and Stiegler, Martin and Klein, Arno and Tautz, J{\"u}rgen}, title = {Mapping Sleeping Bees within Their Nest: Spatial and Temporal Analysis of Worker Honey Bee Sleep}, series = {PLOS ONE}, volume = {9}, journal = {PLOS ONE}, number = {7}, issn = {1932-6203}, doi = {10.1371/journal.pone.0102316}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-115857}, pages = {e102316}, year = {2014}, abstract = {Patterns of behavior within societies have long been visualized and interpreted using maps. Mapping the occurrence of sleep across individuals within a society could offer clues as to functional aspects of sleep. In spite of this, a detailed spatial analysis of sleep has never been conducted on an invertebrate society. We introduce the concept of mapping sleep across an insect society, and provide an empirical example, mapping sleep patterns within colonies of European honey bees (Apis mellifera L.). Honey bees face variables such as temperature and position of resources within their colony's nest that may impact their sleep. We mapped sleep behavior and temperature of worker bees and produced maps of their nest's comb contents as the colony grew and contents changed. By following marked bees, we discovered that individuals slept in many locations, but bees of different worker castes slept in different areas of the nest relative to position of the brood and surrounding temperature. Older worker bees generally slept outside cells, closer to the perimeter of the nest, in colder regions, and away from uncapped brood. Younger worker bees generally slept inside cells and closer to the center of the nest, and spent more time asleep than awake when surrounded by uncapped brood. The average surface temperature of sleeping foragers was lower than the surface temperature of their surroundings, offering a possible indicator of sleep for this caste. We propose mechanisms that could generate caste-dependent sleep patterns and discuss functional significance of these patterns.}, language = {en} } @article{WaeldchenLehmannKleinetal.2015, author = {W{\"a}ldchen, Sina and Lehmann, Julian and Klein, Teresa and van de Linde, Sebastian and Sauer, Markus}, title = {Light-induced cell damage in live-cell super-resolution microscopy}, series = {Scientific Reports}, volume = {5}, journal = {Scientific Reports}, number = {15348}, doi = {10.1038/srep15348}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145207}, year = {2015}, abstract = {Super-resolution microscopy can unravel previously hidden details of cellular structures but requires high irradiation intensities to use the limited photon budget efficiently. Such high photon densities are likely to induce cellular damage in live-cell experiments. We applied single-molecule localization microscopy conditions and tested the influence of irradiation intensity, illumination-mode, wavelength, light-dose, temperature and fluorescence labeling on the survival probability of different cell lines 20-24 hours after irradiation. In addition, we measured the microtubule growth speed after irradiation. The photo-sensitivity is dramatically increased at lower irradiation wavelength. We observed fixation, plasma membrane permeabilization and cytoskeleton destruction upon irradiation with shorter wavelengths. While cells stand light intensities of similar to 1 kW cm\(^{-2}\) at 640 nm for several minutes, the maximum dose at 405 nm is only similar to 50 J cm\(^{-2}\), emphasizing red fluorophores for live-cell localization microscopy. We also present strategies to minimize phototoxic factors and maximize the cells ability to cope with higher irradiation intensities.}, language = {en} } @phdthesis{Wilhelm2005, author = {Wilhelm, Thomas}, title = {Konzeption und Evaluation eines Kinematik/Dynamik-Lehrgangs zur Ver{\"a}nderung von Sch{\"u}lervorstellungen mit Hilfe dynamisch ikonischer Repr{\"a}sentationen und graphischer Modellbildung}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-39554}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2005}, abstract = {Auch nach dem herk{\"o}mmlichen Mechanikunterricht in der Oberstufe verf{\"u}gen viele Sch{\"u}ler nicht {\"u}ber angemessene physikalische Vorstellungen {\"u}ber die verwendeten physikalischen Begriffe und deren Zusammenh{\"a}nge. Einf{\"u}hrend wurden in dieser Arbeit allgemeine Aspekte zu Sch{\"u}lervorstellungen (Kapitel 2.1) sowie konkrete Sch{\"u}lervorstellungen zur Mechanik (Kapitel 2.2) und relevante Lehrervorstellungen (Kapitel 2.3) dargelegt. Ein Ziel dieser Arbeit war, ein Gesamtkonzept f{\"u}r einen ver{\"a}nderten Kinematik- und Dynamikunterricht ein- und zweidimensionaler Bewegungen in der Jahrgangsstufe 11 des Gymnasiums zu entwickeln, das m{\"o}glichst vielen Sch{\"u}lern hilft, m{\"o}glichst viele Fehlvorstellungen zur Mechanik aufzuarbeiten. Dazu wurden u.a. computergest{\"u}tzte Experimente und die Visualisierung der physikalischen Gr{\"o}ßen mit dynamisch ikonischen Repr{\"a}sentationen (siehe Kapitel 3.2) eingesetzt, was neue Elementarisierungen und neue Unterrichtsstrategien erm{\"o}glichte (siehe Kapitel 8.2 oder Kapitel 5). Um gute Chancen zu haben, dass dieses Konzept den Schulalltag erreicht, wurde es lehrplankonform zum bayerischen Lehrplan konzipiert. Eine erste Zielsetzung der summativen Evaluation war festzustellen, inwieweit das gesamte Unterrichtskonzept von verschiedenen Lehrern durchf{\"u}hrbar ist und wie diese es einsch{\"a}tzen (siehe Kapitel 8.4 oder Kapitel 6.3). Ein wichtiges Ziel war dann, mit Hilfe von Tests festzustellen, inwieweit es Ver{\"a}nderungen in den Sch{\"u}lervorstellungen gab (Vor-/Nachtest-Design) und diese Ver{\"a}nderungen mit konventionell unterrichteten Klassen zu vergleichen (Trainings-/Kontrollgruppen-Design) (konventionelle Klassen: Kapitel 8.1; Vergleich: Kapitel 8.5; Kapitel 6.4 + 6.5). Dazu wurden haupts{\"a}chlich bereits vorliegende paper-pencil-Tests verwendet, da eine Testneuentwicklung im Rahmen der Arbeit nicht m{\"o}glich gewesen w{\"a}re. Da diese Tests verschiedene Schw{\"a}chen haben, wurden mehrere verschiedene Tests gleichzeitig eingesetzt, die sich gegenseitig erg{\"a}nzen. Die graphische Modellbildung in Verbindung mit Animationen ist ein fakultativer Teil dieses Unterrichtskonzeptes. Hierzu wurde zus{\"a}tzlich eine eigene Interventionsstudie durchgef{\"u}hrt (siehe Kapitel 8.3 und Kapitel 4). Ergebnisse: Dynamisch ikonische Repr{\"a}sentationen k{\"o}nnen dem Lehrer neue unterrichtliche M{\"o}glichkeiten geben und somit dem Sch{\"u}ler helfen, physikalische Konzepte angemessener zu verstehen. Die Einf{\"u}hrung kinematischer Gr{\"o}ßen anhand zweidimensionaler Bewegungen, die nur mit ikonischen Repr{\"a}sentationen in Form von Vektorpfeilen sinnvoll ist (geeignete Elementarisierung), f{\"u}hrt zu einem physikalischeren Verst{\"a}ndnis des Beschleunigungsbegriffes und vermeidet Fehlvorstellungen durch eine ungeeignete Reduktion auf den Spezialfall eindimensionaler Bewegungen. Mehr Sch{\"u}ler konzeptualisieren Beschleunigung wie in der Physik als gerichtete Gr{\"o}ße anstelle einer Gr{\"o}ße, die die {\"A}nderung des Geschwindigkeitsbetrages angibt und allenfalls tangentiale Richtung haben kann. Auch in der Dynamik sind dadurch hilfreiche Darstellungen und so sinnvolle Ver{\"a}nderungen des Unterrichts m{\"o}glich. Um wesentliche Strukturen aufzuzeigen, werden komplexere Versuche mit mehreren Kr{\"a}ften und Reibung eingesetzt, was erst durch eine rechnerunterst{\"u}tzte Aufbereitung mit dynamisch ikonischen Repr{\"a}sentationen erm{\"o}glicht wird. Diese Darstellungen erm{\"o}glichen auch eine aktive Auseinandersetzung der Sch{\"u}ler mit den Themen, indem von ihnen h{\"a}ufig Vorhersagen gefordert werden (geeignete Unterrichtsstrategie). Graphische Modellbildung als weiterer Einsatz bildlicher Darstellungen kann ebenso eine weitere Verst{\"a}ndnishilfe sein. Sch{\"u}ler, die nach dem vorgelegten Unterrichtskonzept unterrichtet wurden, zeigten mehr Verst{\"a}ndnis f{\"u}r den newtonschen Kraftbegriff. Da die entwickelten Ideen tats{\"a}chlich im Unterricht ankamen und dort Ver{\"a}nderungen bewirkten, kann von einer effektiven Lehrerfortbildung mit Transferwirkung gesprochen werden.}, subject = {Physikunterricht}, language = {de} } @article{KimKusudoLoeffleretal.2013, author = {Kim, N. Y. and Kusudo, K. and L{\"o}ffler, A. and H{\"o}fling, S. and Forchel, A. and Yamamoto, Y.}, title = {Exciton-polariton condensates near the Dirac point in a triangular lattice}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {035032}, issn = {1367-2630}, doi = {10.1088/1367-2630/15/3/035032}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-123103}, year = {2013}, abstract = {Dirac particles, massless relativistic entities, obey linear energy dispersions and hold important implications in particle physics. The recent discovery of Dirac fermions in condensed matter systems including graphene and topological insulators has generated a great deal of interest in exploring the relativistic properties associated with Dirac physics in solid-state materials. In addition, there are stimulating research activities to engineer Dirac particles, elucidating their exotic physical properties in a controllable setting. One of the successful platforms is the ultracold atom-optical lattice system, whose dynamics can be manipulated and probed in a clean environment. A microcavity exciton-polariton-lattice system offers the advantage of forming high-orbital condensation in non-equilibrium conditions, which enables one to explore novel quantum orbital order in two dimensions. In this paper, we experimentally construct the band structures near Dirac points, the vertices of the first hexagonal Brillouin zone with exciton-polariton condensates trapped in a triangular lattice. Due to the finite spectral linewidth, the direct map of band structures at Dirac points is elusive; however, we identify the linear part above Dirac points and its associated velocity value is similar to ~0.9-2 x \(10^8 cm s^{-1}\), consistent with the theoretical estimate \(1 x 10^8 cm s^{-1}\) with a \(2 \mu m\) lattice constant. We envision that the exciton-polariton condensates in lattices would be a promising solid-state platform, where the system order parameter can be accessed in both real and momentum spaces.}, language = {en} } @phdthesis{Thom2002, author = {Thom, Corinna}, title = {Dynamics and Communication Structures of Nectar Foraging in Honey Bees (Apis mellifera)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-3601}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2002}, abstract = {In this thesis, I examined honey bee nectar foraging with emphasis on the communication system. To document how a honey bee colony adjusts its daily nectar foraging effort, I observed a random sample of individually marked workers during the entire day, and then estimated the number and activity of all nectar foragers in the colony. The total number of active nectar foragers in a colony changed frequently between days. Foraging activity did not usually change between days. A honey bee colony adjusts its daily foraging effort by changing the number of its nectar foragers rather than their activity. I tested whether volatiles produced by a foraging colony activated nectar foragers of a non-foraging colony by connecting with a glass tube two colonies. Each colony had access to a different green house. In 50\% of all experiments, volatile substances from the foraging colony stimulated nectar foragers of the non-foraging colony to fly to an empty feeder. The results of this study show that honey bees can produce a chemical signal or cue that activates nectar foragers. However, more experiments are needed to establish the significance of the activating volatiles for the foraging communication system. The brief piping signal of nectar foragers inhibits forager recruitment by stopping waggle dances (Nieh 1993, Kirchner 1993). However, I observed that many piping signals (approximately 43\%) were produced off the dance floor, a restricted area in the hive where most waggle dances are performed. If the inhibition of waggle dances would be the only function of the brief piping signal, tremble dancers should produce piping signals mainly on the dance floor, where the probability to encounter waggle dancers is highest. To therefore investigate the piping signal in more detail, I experimentally established the foraging context of the brief piping signal, characterized its acoustic properties, and documented for the first time the unique behavior of piping nectar foragers by observing foragers throughout their entire stay in the hive. Piping nectar foragers usually began to tremble dance immediately upon their return into the hive, spent more time in the hive, more time dancing, had longer unloading latencies, and were the only foragers that sometimes unloaded their nectar directly into cells instead of giving it to a nectar receiver bee. Most of the brief piping signals (approximately 99\%) were produced by tremble dancers, yet not all tremble dancers (approximately 48\%) piped. This suggests that piping and tremble dancing have related, but not identical functions in the foraging system. Thus, the brief piping signals may not only inhibit forager recruitment, but have an additional function both on and off the dance floor. In particular, the piping signal might function 1. to stop the recruitment of additional nectar foragers, and 2. as a modulatory signal to alter the response threshold of signal receivers to the tremble dance. The observation that piping tremble dancers often did not experience long unloading delays before they started to dance gave rise to a question. A forager's unloading delay provides reliable information about the relative work capacities of nectar foragers and nectar receivers, because each returning forager unloads her nectar to a nectar receiver before she takes off for the next foraging trip. Queuing delays for either foragers or receivers lower foraging efficiency and can be eliminated by recruiting workers to the group in shortage. Short unloading delays indicate to the nectar forager a shortage of foragers and stimulate waggle dancing which recruits nectar foragers. Long unloading delays indicate a shortage of nectar receivers and stimulate tremble dancing which recruits nectar receivers (Seeley 1992, Seeley et al. 1996). Because the short unloading delays of piping tremble dancers indicated that tremble dancing can be elicited by other factors than long unloading delays, I tested whether a hive-external stimulus, the density of foragers at the food source, stimulated tremble dancing directly. The experiments show that tremble dancing can be caused directly by a high density of foragers at the food source and suggest that tremble dancing can be elicited by a decrease of foraging efficiency either inside (e.g. shortage of receiver bees) or outside (e.g. difficulty of loading nectar) the hive. Tremble dancing as a reaction to hive-external stimuli seems to occur under natural conditions and can thus be expected to have some adaptive significance. The results imply that if the hive-external factors that elicit tremble dancing do not indicate a shortage of nectar receiver bees in the hive, the function of the tremble dance may not be restricted to the recruitment of additional nectar receivers, but might be the inhibition or re-organization of nectar foraging.}, subject = {Bienen }, language = {en} }