University of Bremen

About: University of Bremen is a education organization based out in Bremen, Germany. It is known for research contribution in the topics: Population & Glacial period. The organization has 14563 authors who have published 37279 publications receiving 970381 citations. The organization is also known as: Universität Bremen.

Analysis for BrO in zenith‐sky spectra: An intercomparison exercise for analysis improvement

Abstract: [1] The analysis for BrO using the technique of differential optical absorption spectroscopy as applied to spectra of light scattered from the zenith sky has historically presented something of a challenge, leading to uncertainty about the accuracy of measurements. This has largely been due to the large sensitivity of the measurement to many analysis parameters and due to the small size of the absorption features being measured. BrO differential slant columns have been measured by six different groups taking part in an intercomparison exercise at Observatoire de Haute-Provence in France from 23 to 27 June 1996. The data are analyzed in a collaborative attempt to improve the overall analysis for BrO through investigation of a series of sources of errors in the instrumentation, calibration, input to the analysis, and the spectral analysis itself. The study included comprehensive sensitivity tests performed using both actual measurements and synthetic data. The latter proved invaluable for assessing several aspects of the spectral analysis without the limitations of spectral quality and instrument variability. The most significant sources of error are identified as the wavelength calibration of several of the absorption cross sections fitted and of the measured spectra themselves, the wavelength region of the fitting, the temperature dependence of the O3 absorption cross sections, failure to adequately account for the so-called I0 effect, inadequate offset correction, and inadequate measurement of the individual instrument slit functions. Recommendations for optimal analysis settings are presented, and comparing the results from the analysis of the campaign data shows BrO differential slant column observations from the various groups to be in agreement to within 4% on average between 87° and 90° solar zenith angle, with a scatter of 16%.

Market Mechanisms and Funding Dynamics in Equity Crowdfunding

Abstract: We use hand-collected data from four German crowdinvesting portals to analyze what determines individual investment decisions in crowdinvesting. In contrast with the crowdfunding campaigns on Kickstarter where the typical pattern of project support is U-shaped, we find crowdinvesting dynamics to be L-shaped under a first-come, first-serve mechanism and only U-shaped under a sealed-bid second-price auction. The evidence further shows that investors base their decisions on information provided by the entrepreneur in form of updates during the campaign and by the investment behavior and comments of other crowd investors. We also find evidence for herding behavior. As legislators around the world increasingly regulate crowdinvesting activities, knowing how crowd investors behave under no formal information disclosure provides important insights for issuers, portals, and lawmakers.

Primer: administrative health databases in observational studies of drug effects--advantages and disadvantages.

Abstract: Observational database studies provide important information on the safety and benefit of approved medications. As discussed in this Review, the limitations of these studies, and the nature of their design and analysis, should be taken into account when results are interpreted.

Parallelism and concurrency in high-level replacement systems

Abstract: High-level replacement systems are formulated in an axiomatic algebraic framework based on categories pushouts. This approach generalizes the well-known algebraic approach to graph grammars and several other types of replacement systems, especially the replacement of algebraic specifications which was recently introduced for a rule-based approach to modular system design.in this paper basic notions like productions, derivations, parellel and sequential independence are introduced for high-level replacement syetms leading to Church-Rosser, Parallelism and concurrency Theorems previously shown in the literature for special cases only. In the general case of high-level replacement systems specific conditions, called HLR1- and HLR2-conditions, are formulated in order to obtain these results.Several examples of high-level replacement systems are discussed and classified w.r.t. HLR1- and HLR2-conditions showing which of the results are valid in each case.