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Institution

University of Bremen

EducationBremen, Germany
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.


Papers
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Journal ArticleDOI
TL;DR: CuO and ZnO had the highest toxicity (EC50 values below 1 mg l−1) among all organism groups except for the protozoa, and the high toxicity was mostly due to the shedding of toxic concentrations of Zn and Cu ions.
Abstract: The use of metal-based nanoparticles (NPs) is increasing which leads to their release in water bodies via various waste streams, and thus warrants risk assessment. Consistent biological-effect data of NPs for environmentally relevant test species, which are accompanied by thorough characterization of NPs, are scarce but indispensable for understanding the possible risks of NPs. We composed and tested a library of 12 metal-based nanoparticles (Al2O3, Co3O4, CuO, Fe3O4, MgO, Mn3O4, Sb2O3, SiO2, ZnO, TiO2, WO3 and Pd) using the alga Pseudokirchneriella subcapitata, three bacterial species (Vibrio fischeri, Escherichia coli, Staphylococcus aureus) and the protozoa Tetrahymena thermophila. The NPs were characterized for their physico-chemical properties, solubility and abiotic reactive oxygen species (ROS) production. Also, respective soluble salts were analysed for toxic effects. The algal growth inhibition assay has proven to be the most sensitive and yielded EC50 values for 10 NPs ranging from 0.1 to 58 mg l−1. Algal toxicity correlated with abiotic ROS production of NPs, and the majority of the NPs formed agglomerates that entrapped algal cells. Despite the different sensitivities, there was a common trend in the toxicity of the NPs across different species and test formats: CuO and ZnO had the highest toxicity (EC50 values below 1 mg l−1) among all organism groups except for the protozoa. The high toxicity was mostly due to the shedding of toxic concentrations of Zn and Cu ions; for most of the test species, Al2O3, SiO2, WO3 and Sb2O3 were not toxic below 100 mg l−1 and MgO showed no adverse effects below 100 mg l−1 to any test species in any test setting.

172 citations

Journal ArticleDOI
TL;DR: There is an annually increasing frequency of chronic wounds in Germany and chronic wound epidemiology is sensitive to wound treatment as a filter criterion, and prevalence and incidence increased over 3 years.
Abstract: Epidemiologic analyses in routine care of chronic wounds are scarce, and published studies show wide variations. This study analyzes the population-based prevalence and incidence of chronic wounds in Germany. Secondary analyses of data from a German statutory health insurance with about 9 million insured persons were examined (2010 to 2012). Internal diagnostic validations were used to control for different inclusion criteria. In 2012, 1.04% (95% CI 1.03-1.05) of insured patients had a wound diagnosis, including 0.70% with leg ulcers and 0.27% with diabetic ulcers. Wound treatment was received by 0.43% (0.43-0.44) of patients. Prevalence and incidence increased over 3 years. Extrapolated to the German population, there were 786,407 prevalent and 196,602 incident chronic wounds, including 326,334/172,026 patients who underwent wound-relevant treatment in 2012. There is an annually increasing frequency of chronic wounds in Germany. Chronic wound epidemiology is sensitive to wound treatment as a filter criterion.

172 citations

Book ChapterDOI
24 Mar 2007
TL;DR: Heterogeneous specification becomes more and more important because complex systems are often specified using multiple viewpoints, involving multiple formalisms (see Fig. 1).
Abstract: Heterogeneous specification becomes more and more important because complex systems are often specified using multiple viewpoints, involving multiple formalisms (see Fig. 1). Moreover, a formal software development process may lead to a change of formalism during the development.

172 citations

Journal ArticleDOI
TL;DR: The large exciton binding energy in MoS2 enables two distinctly different excitation methods: above-band gap excitation and quasi-resonant excitation of excitonic resonances below the single-particle band gap.
Abstract: We discuss the photoluminescence (PL) of semiconducting transition metal dichalcogenides on the basis of experiments and a microscopic theory The latter connects ab initio calculations of the single-particle states and Coulomb matrix elements with a many-body description of optical emission spectra For monolayer MoS2, we study the PL efficiency at the excitonic A and B transitions in terms of carrier populations in the band structure and provide a quantitative comparison to an (In)GaAs quantum well-structure Suppression and enhancement of PL under biaxial strain is quantified in terms of changes in the local extrema of the conduction and valence bands The large exciton binding energy in MoS2 enables two distinctly different excitation methods: above-band gap excitation and quasi-resonant excitation of excitonic resonances below the single-particle band gap The latter case creates a nonequilibrium distribution of carriers predominantly in the K-valleys, which leads to strong emission from the A-exciton transition and a visible B-peak even if the band gap is indirect For above-band gap excitation, we predict a strongly reduced emission intensity at comparable carrier densities and the absence of B-exciton emission The results agree well with PL measurements performed on monolayer MoS2 at excitation wavelengths of 405 nm (above) and 532 nm (below the band gap)

171 citations

Journal ArticleDOI
TL;DR: In this paper, two processes of diffusion-limited pyrite formation were identified, i.e., precipitation with the accumulation of iron sulfide precursors with the average chemical composition of FeSn (n = 1.10−1.29), including greigite.

171 citations


Authors

Showing all 14961 results

NameH-indexPapersCitations
Roger Y. Tsien163441138267
Klaus-Robert Müller12976479391
Ron Kikinis12668463398
Ulrich S. Schubert122222985604
Andreas Richter11076948262
Michael Böhm10875566103
Juan Bisquert10745046267
John P. Sumpter10126646184
Jos Lelieveld10057037657
Michael Schulz10075950719
Peter Singer9470237128
Charles R. Tyler9232531724
John P. Burrows9081536169
Hans-Peter Kriegel8944473932
Harald Haas8575034927
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023343
2022709
20212,106
20202,309
20192,191
20181,965