University of Konstanz

About: University of Konstanz is a education organization based out in Konstanz, Baden-Württemberg, Germany. It is known for research contribution in the topics: Population & Membrane. The organization has 12115 authors who have published 27401 publications receiving 951162 citations. The organization is also known as: University of Constance & Universität Konstanz.

Earlier onset of the spring phytoplankton bloom in lakes of the temperate zone in a warmer climate

Abstract: The decoupling of trophic interactions is potentially one of the most severe consequences of climate warming. In lakes and oceans the timing of phytoplankton blooms affects competition within the plankton community as well as food–web interactions with zooplankton and fish. Using Upper Lake Constance as an example, we present a model-based analysis that predicts that in a future warmer climate, the onset of the spring phytoplankton bloom will occur earlier in the year than it does at present. This is a result of the earlier occurrence of the transition from strong to weak vertical mixing in spring, and of the associated earlier onset of stratification. According to our simulations a shift in the timing of phytoplankton growth resulting from a consistently warmer climate will exceed that resulting from a single unusually warm year. The numerical simulations are complemented by a statistical analysis of long-term data from Upper Lake Constance which demonstrates that oligotrophication has a negligible effect on the timing of phytoplankton growth in spring and that an early onset of the spring phytoplankton bloom is associated with high air temperatures and low wind speeds.

Optimization of Polynomials on Compact Semialgebraic Sets

Abstract: A basic closed semialgebraic subset S of $\R^n$ is defined by simultaneous polynomial inequalities $g_1\ge 0,\dotsc,g_m\ge 0$. We give a short introduction to Lasserre's method for minimizing a polynomial f on a compact set S of this kind. It consists of successively solving tighter and tighter convex relaxations of this problem which can be formulated as semidefinite programs. We give a new short proof for the convergence of the optimal values of these relaxations to the infimum $f^\ast$ of f on S which is constructive and elementary. In the case where f possesses a unique minimizer $x^\ast$, we prove that every sequence of "nearly" optimal solutions of the successive relaxations gives rise to a sequence of points in $\R^n$ converging to $x^\ast$.

What makes a creative day? A diary study on the interplay between affect, job stressors, and job control.

Abstract: Applying a within-person perspective to research on creativity at work, this diary study examined daily positive and negative affect (NA) in the morning as well as daily job stressors (time pressure and situational constraints) as predictors of daily creativity. In addition, the general level of job control was investigated as a cross-level moderator in these relationships. Hypotheses were tested in a sample of 90 interior architects (N = 326 days) who completed a general survey and two daily surveys over the course of one work week. Hierarchical linear modeling showed that a higher level of positive affect (PA) in the morning as well as an intermediate level of daily time pressure was related to higher daily creativity. Job control moderated relations between daily NA, daily situational constraints and daily time pressure (curvilinear effect) with daily creativity. Our results stress the importance of daily affect and daily job stressors as well as the moderating role of job control for daily creativity at work. Copyright © 2010 John Wiley & Sons, Ltd.

Structural decomposition and heterogeneity of commercial lipoteichoic Acid preparations.

Abstract: Fractionation of commercial preparations of lipoteichoic acids (LTA) by hydrophobic interaction chromatography (HIC) and nuclear magnetic resonance spectroscopy revealed very inhomogeneous compositions and decomposition of the LTA structure: LTA content of the preparations averaged 61% for Streptococcus pyogenes, 16% for Bacillus subtilis, and 75% for Staphylococcus aureus. The decomposition was characterized by a loss of glycerophosphate units as well as alanine and N-acetylglucosamine substituents. All preparations contained—to varying degrees—non-LTA, non-lipopolysaccharide (LPS) immunostimulatory components as indicated by their elution profile in HIC, lack of phosphate, and negative Limulus amoebocyte lysate (LAL) test results. After purification, the commercial LTA from Bacillus subtilis and S. pyogenes but not LTA from S. aureus induced the release of tumor necrosis factor alpha, interleukin 1 beta (IL-1β), IL-6, and IL-10 in human blood. While pure LTA are negative in the LAL assay, endotoxin equivalents of more than 10 ng of LPS/mg of LTA were found in the commercial preparations. Taken together, these data indicate that these crude preparations with relatively high endotoxin contamination are not suitable for characterizing the activation of immune cells by LTA.