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Institution

Leibniz University of Hanover

EducationHanover, Niedersachsen, Germany
About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Population. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.


Papers
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Journal ArticleDOI
TL;DR: It is hypothesized that subtle, but important, differences in the U-O coordination shell between dissolved and adsorbed U are responsible for the fractionation observed in the authors' experiments as well as for some U isotope variations in nature.
Abstract: Previous work has shown uranium (U) isotope fractionation between natural ferromanganese crusts and seawater. Understanding the mechanism that causes 238U/235U fractionation during adsorption to ferromanganese oxides is a critical step in the utilization of 238U/235U as a tracer of U adsorption reactions in groundwater as well as a potential marine paleoredox proxy. We conducted U adsorption experiments using synthetic K-birnessite and U-bearing solutions. These experiments revealed a fractionation matching that observed between seawater and natural ferromanganese sediments: adsorbed U is isotopically lighter by ∼0.2‰ (δ238/235U) than dissolved U. As the redox state of U does not change during adsorption, a difference in the coordination environment between dissolved and adsorbed U is likely responsible for this effect. To test this hypothesis, we analyzed U adsorbed to K-birnessite in our experimental study using extended X-ray absorption fine structure (EXAFS) spectroscopy, to obtain information about U...

154 citations

Journal ArticleDOI
TL;DR: In this paper, a canonical form of mixed states in bipartite quantum systems in terms of a convex combination of a separable state and a so-called edge state is provided.
Abstract: We provide a canonical form of mixed states in bipartite quantum systems in terms of a convex combination of a separable state and a so-called edge state. We construct entanglement witnesses for all edge states, which allows us to introduce a canonical form of nondecomposable entanglement witnesses and the corresponding positive maps. We also present a nontrivial necessary condition for entanglement witnesses and positive maps to be extremal.

154 citations

Journal ArticleDOI
TL;DR: The results of an electron microscopy analysis of ATP synthase dimers purified from Saccharomyces cerevisiae strongly support the hypothesized role of ATP synthesis oligomers in structural determination of the mitochondrial inner membrane.

154 citations

Journal ArticleDOI
TL;DR: Data verify that the choice of individual parameters for cell propagation, such as duration of cell expansion and cell seeding density, has a substantial impact on the quality of UC-derived cell populations.
Abstract: Up to 2.8 × 10(7) fibroblast-like cells displaying an abundant presence of mesenchymal stem cell (MSC) markers CD73, CD90, CD105 and a low level of HLA-I expression can be isolated from one whole human umbilical cord (UC) using a simple and highly reproducible explant culture approach. Cells derived from whole UC, similar to cells collected from separate compartments of UC, display a distinct chondrogenic and adipogenic potential. Therefore they are potential candidates for cartilage and adipose tissue engineering. Cell differentiation along the osteogenic pathway is, however, less efficient, even after the addition of 1.25-dihydroxyvitamin D3, a potent osteoinductive substance. Isolated cells are highly proliferative, tolerate cryopreservation with an average survival rate of about 75% and after thawing can be propagated further, at least over 20 population doublings before their proliferative activity begins to decline. More importantly, they synthesize numerous trophic factors including neurotrophins and factors which facilitate angiogenesis and hematopoiesis. In conclusion, cells isolated from whole UC satisfies all requirements essential for the generation of stem cell banks containing permanently available cell material for applications in the field of regenerative medicine. Nevertheless, further studies are needed to improve and adjust the methods which are already employed for adult MSC expansion and differentiation to specific properties and requirements of the primitive stem cells collected from UC. So, our data verify that the choice of individual parameters for cell propagation, such as duration of cell expansion and cell seeding density, has a substantial impact on the quality of UC-derived cell populations.

153 citations


Authors

Showing all 14621 results

NameH-indexPapersCitations
Hyun-Chul Kim1764076183227
Peter Zoller13473476093
J. R. Smith1341335107641
Chao Zhang127311984711
Benjamin William Allen12480787750
J. F. J. van den Brand12377793070
J. H. Hough11790489697
Hans-Peter Seidel112121351080
Karsten Danzmann11275480032
Bruce D. Hammock111140957401
Benno Willke10950874673
Roman Schnabel10858971938
Jan Harms10844776132
Hartmut Grote10843472781
Ik Siong Heng10742371830
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023221
2022520
20212,280
20202,210
20192,105
20181,959