682 research outputs found
Monopolistic Intermediation in the Gehrig (1993) Search Model Revisited
No full textWe modify the basic Gehrig (1993) model. In this model, individual agents are either buyers or sellers. They can choose between joining the search market, joining the monopolistic intermediary or remaining inactive. In the search market, agents are randomly matched and the price at which exchange takes place is set bilaterally. If agents join the intermediary, buyers have to pay an ask price set in advance by the intermediary. Likewise, if sellers decide to deal through the intermediary, they get the bid price set by the intermediary. As Gehrig shows, this model has an equilibrium in which the search market and the market of the monopolistic intermediary are simultaneously open. The intermediary makes positive profits because he trades at a positive ask-bid spread, and the set of individual agents is tripartite: High valuation buyers and low cost sellers deal through the intermediary, buyers and sellers with average valuations and average costs are active in the search market, and low valuation buyers and high cost sellers remain inactive. We modify this basic model by imposing a sequential structure. We assume that the monopolistic intermediary first has to buy the good from sellers on the input market before he can sell it to buyers on the output market. As a consequence of the sequential structure, the subgame following capacity setting has a unique subgame perfect equilibrium with an active search market. On the equilibrium path, the equilibrium analyzed by Gehrig is replicated.market-making; market microstructure; competing exchange mechanisms
102 hpf medaka embryos in 96 well plate (4 embryo/well) - brightfield - 2X magnification - ACQUIFER Imaging Machine
No full textDataset originates from:
Gierten, J., Pylatiuk, C., Hammouda, O. T., Schock, C., Stegmaier, J., Wittbrodt, J., Gehrig, J. and Loosli, F. (2020). Automated high-throughput heartbeat quantification in medaka and zebrafish embryos under physiological conditions. Sci Rep 10, 2046, doi:10.1038/s41598-020-58563-w.
Used as benchmark dataset for Multi-Template-Matching by Thomas and Gehrig
See implementation in Fiji https://github.com/LauLauThom/MultipleTemplateMatching
and in KNIME https://github.com/LauLauThom/MultipleTemplateMatching-KNIME
Contacts: j.gehrig(at)acquifer.de, l.thomas(at)acquifer.de, jakob.gierten(at)cos.uni-heidelberg.d
Die Entdeckung der Unmöglichkeit einer kritischen Theorie gesellschaftlicher Naturverhältnisse durch Thomas Gehrig
No full textIn dem vorliegenden Text wird die „Kritik des ökologischen Diskurses“ analysiert, die von Thomas Gehrig in einem monumentalen zweibändigen Werk vorgetragen wird. Darin kritisiert er fundamental die wissenschaftliche Bearbeitung des Themas in der Sozialen Ökologie. In seiner Studie zieht er 107 Texte von Autorinnen und Autoren aus dem ISOE heran, die in einem Zeitraum von 35 Jahren entstanden sind. Anhand dieser Texte versucht er seine zentralen Thesen zu beweisen: Der ökologische Diskurs lenke von der notwendigen radikalen Kapitalismuskritik ab und treibe die Modernisierung des kapitalistischen Systems voran; eine kritische Theorie der gesellschaftlichen Naturverhältnisse lasse sich philosophisch nicht begründen und sie sei wissenschaftlich unmöglich. Den Maßstab seiner Kritik entnimmt Gehrig der frühen Kritischen Theorie sowie einem von der marxistischen Interpretationsgeschichte gereinigten Marx. In der vorliegenden Analyse wird die aus einer soziologischen Dissertation hervorgegangene Studie als Dokumentation eines politischen Prozesses und eines pseudowissenschaftlichen Tribunals über die Soziale Ökologie detailliert rekonstruiert und dabei gezeigt, wie das von dem Autor beanspruchte Verfahren einer radikalen Kritik funktioniert. Diskutiert wird auch, was aus dem Gehrig’schen Werk dennoch für die Weiterarbeit am theoretischen Programm der Sozialen Ökologie zu lernen ist.Recently, the sociologist Thomas Gehrig has published his monumental two-volume opus “critique of the ecological discourse”. In a fundamental manner he criticized how the issue is treated within Social Ecology. This opus is analyzed in the text presented here. In his study Gehrig refers to 107 articles and books published by authors from ISOE in a period of 35 years. By means of these texts he tries to substantiate his central thesis: the ecological discourse distracts from the necessary radical critique of capitalism and promotes the modernization and green-washing of the destructive capitalist system; philosophically it would be impossible to justify a critical theory of societal relations to nature and therefore for him such a theory turns out to be impossible. Gehrig borrowed the criterion for his criticism from the early critical theory as well as from a Marx purified from the history of Marxist interpretations. In the analysis at hand the opus of Gehrig, emanating from a sociological dissertation, is reconstructed in detail as the documentation of a political trial and a pseudoscientific tribunal against Social Ecology. The functioning of the procedure of a radical Marxist critique claimed by the author is pointed out. Nevertheless, the analysis is discussing what can be learned from Gehrig’s opus for further research within the theoretical program of Social Ecology
Effectiveness of artificial watering of a semi-arid saline wetland for managing riparian vegetation health
No full textCopyright © 2010 John Wiley & Sons, Ltd.Kate L. Holland, Alison H. Charles, Ian D. Jolly, Ian C. Overton, Susan Gehrig and Craig T. Simmon
Buying a pig in a poke : An experimental study of unconditional veto power
No full textWe study an ultimatum experiment in which the responder does not know the offer when accepting or rejecting. Unconditional veto power leads to acceptances, although proposers are significantly greedier than in standard ultimatum games, and this is anticipated by responders. We also elicit responders' willingness to pay for (un)conditional veto power
Canopy level fog occurrence in a tropical lowland forest of French Guiana as a prerequisite for high epiphyte diversity
No full textFog frequency and the meteorological processes leading to fog formation have never been studied in depth in tropical lowland forest areas. This study provides detailed evidence of frequent fog occurrence in lowland valleys of central French Guiana. Fog frequency showed a clear diurnal course, with a maximum before sunrise; average fog duration was 4.6 h. The diurnal course of visibility was positively correlated with the diurnal course of humidity in the above-canopy air. Fog persistence correlated significantly with atmospheric parameters during the dry season, but not during the rainy season. The main trigger of fog development in the lowland forest seemed to be precipitation, leading to higher soil moisture, greater evapotranspiration and, thus, higher water content of air. An increasing temperature difference between valley and hill sites after sunset, together with more frequent down-slope winds during nights with long fog periods, points at some influence of katabatic flows. The frequent occurrence of fog in the valleys correlated with significantly higher epiphyte diversities in valley forests as compared to hill forests, and supported the occurrence of the hitherto undescribed, epiphyte-rich "tropical lowland cloud forest" (LCF) in the valleys. The higher epiphyte diversity in LCF coincided with significantly higher relative air humidity in LCF than in hill forest. The ecological benefits of fog for the epiphytes in LCF are surplus of moisture and delayed onset of the stress period, particularly in the dry season. (C) 2010 Elsevier B.V. All rights reserved.German Research Foundation (DFG) [BE 1780/13-1, GR 1588/12-1
Two at the Top: Quality Differentiation in Markets with Switching Costs
No full textWe explore the effects of switching costs on the subgame perfect quality decisions of oligopolists with repeated price competition. We establish a strong strategic quality premium. We show that competition for the establishment of customer relationships will eliminate low-quality firms in period 1 and that low-quality firms can survive only based on poaching profits. The equilibrium configuration is characterized by an agglomeration of two providers of top-quality as soon as switching cost heterogeneity is sufficiently significant. We demonstrate a finiteness property, according to which the two top-quality firms dominate the market with a joint market share exceeding 50 %.quality choice; switching costs; poaching; natural oligopoly
Venture Cycles: Theory and Evidence
No full textWe demonstrate how endogenous information acquisition in venture capital markets creates investment cycles when competing financiers undertake their screening decisions in an uncoordinated way, thereby highlighting the role of intertemporal screening externalities induced by competition among venture capitalists as a structural source of instability. We show that uncoordinated screening behavior of competing financiers is an independent source of fluctuations inducing venture investment cycles. We also empirically document the existence of cyclical features in a number of industries such as biotechnology, electronics, financial services, healthcare, medical services and consumer products.screening, venture capital, investment cycles
Competition between market-making Intermediaries
No full textWe introduce capacity constrained competition between market-making intermediaries in a model in which agents can choose between trading with intermediaries, joining a search market or remaining inactive. Recently, market-making by a monopolistic intermediary has been analyzed by Rust and Hall (2003) and Gehrig (1993). Market-makers set publicly observable ask and bid prices. Because market-making involves price setting, without further restrictions competition between market-making intermediaries is Bertrand-like and yields the Walrasian outcome, where the ask-bid spread is zero (Rust and Hall 2003, Gehrig 1993). However, positive ask-bid spreads and competition between market-makers can be observed in reality, e.g. in banking and in retailing. Following Kreps and Scheinkman (1983) and Boccard and Wauthy (2000), we therefore introduce physical capacity constraints. This allows for a gradual transition from monopolistic to perfectly competitive intermediation as the number of intermediaries increases. In particular, we show that given Cournot capacities, intermediaries will set Cournot bid and ask prices in the subsequent subgames, so that the equilibrium of the intermediated market coincides with the Walrasian equilibrium as the number of intermediaries becomes largeMarket-making, capacity constrained competition, market microstructure
An evaluation framework for stereo-based driver assistance
No full textThis is the post-print version of the Article - Copyright @ 2012 Springer VerlagThe accuracy of stereo algorithms or optical flow methods is commonly assessed by comparing the results against the Middlebury
database. However, equivalent data for automotive or robotics applications
rarely exist as they are difficult to obtain. As our main contribution, we introduce an evaluation framework tailored for stereo-based driver assistance able to deliver excellent performance measures while
circumventing manual label effort. Within this framework one can combine several ways of ground-truthing, different comparison metrics, and use large image databases.
Using our framework we show examples on several types of ground truthing techniques: implicit ground truthing (e.g. sequence recorded without a crash occurred), robotic vehicles with high precision sensors, and to a small extent, manual labeling. To show the effectiveness of our evaluation framework we compare three different stereo algorithms on
pixel and object level. In more detail we evaluate an intermediate representation
called the Stixel World. Besides evaluating the accuracy of the Stixels, we investigate the completeness (equivalent to the detection rate) of the StixelWorld vs. the number of phantom Stixels. Among many findings, using this framework enables us to reduce the number of phantom Stixels by a factor of three compared to the base parametrization. This base parametrization has already been optimized by test driving vehicles for distances exceeding 10000 km
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