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Search Results: 1 - 10 of 1507 matches for " Claus Kordes "
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Stellate Cells from Rat Pancreas Are Stem Cells and Can Contribute to Liver Regeneration
Claus Kordes, Iris Sawitza, Silke G?tze, Dieter H?ussinger
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051878
Abstract: The identity of pancreatic stem/progenitor cells is still under discussion. They were suggested to derive from the pancreatic ductal epithelium and/or islets. Here we report that rat pancreatic stellate cells (PSC), which are thought to contribute to pancreatic fibrosis, have stem cell characteristics. PSC reside in islets and between acini and display a gene expression pattern similar to umbilical cord blood stem cells and mesenchymal stem cells. Cytokine treatment of isolated PSC induced the expression of typical hepatocyte markers. The PSC-derived hepatocyte-like cells expressed endodermal proteins such as bile salt export pump along with the mesodermal protein vimentin. The transplantation of culture-activated PSC from enhanced green fluorescent protein-expressing rats into wild type rats after partial hepatectomy in the presence of 2-acetylaminofluorene revealed that PSC were able to reconstitute large areas of the host liver through differentiation into hepatocytes and cholangiocytes. This developmental fate of transplanted PSC was confirmed by fluorescence in situ hybridization of chromosome Y after gender-mismatched transplantation of male PSC into female rats. Transplanted PSC displayed long-lasting survival, whereas muscle fibroblasts were unable to integrate into the host liver. The differentiation potential of PSC was further verified by the transplantation of clonally expanded PSC. PSC clones maintained the expression of stellate cell and stem cell markers and preserved their differentiation potential, which indicated self-renewal potential of PSC. These findings demonstrate that PSC have stem cell characteristics and can contribute to the regeneration of injured organs through differentiation across tissue boundaries.
ENTROPY - OUR BEST FRIEND
Urban Kordes
Interdisciplinary Description of Complex Systems , 2005,
Abstract: The paper tries to tackle the question of connection between entropy and the living. Definitions of life as the phenomenon that defies entropy are overviewed and the conclusion is reached that life is in a way dependant on entropy - it couldn't exist without it. Entropy is a sort of medium, a fertile soil, that gives life possibility to blossom. Paper ends with presenting some consequences for the field of artificial intelligence.
Participatory Position
Ubran Kordes
Interdisciplinary Description of Complex Systems , 2005,
Abstract: The paper deals with the problems encountered in exploring/describing cognising systems. It is argued that these are mostly an issue of epistemology and that some of the aspects of the above mentioned systems cannot be described without taking into account the researcher’s participation in the process of researching (and describing).
Percursos acelerados de jovens condutores ilegais: o risco entre vida e morte, entre jogo e rito
Jeolás, Leila Sollberger;Kordes, Hagen;
Horizontes Antropológicos , 2010, DOI: 10.1590/S0104-71832010000200008
Abstract: this ethographic study about the "rachas" of motos and cars is grounded around the question, if and in how far the acceleration of motors could serve as a methaphor for the acceleration of fluid, flexible and undetermined par-courses of life in the context of "surmodern" societies. the objective is first to understand the significations given to the experiences of speed and of the risks implied, in order to analyse then the relationship between the youth's risk conduct and the rites of passage. we will discuss the potentialities and limits of comprehending the "rachas" on one side as an individualised form of a passage ritual and on the other side as a ludicrous expression of play and joy. thus we could interpret the "rachas" like other varieties of youth culture as a language of singularisation and affiliation emphasized by practices of traditional hegemonic masculinity.
Simultaneous Echo Refocused Magnetization Transfer Imaging  [PDF]
Claus Kiefer
Open Journal of Medical Imaging (OJMI) , 2014, DOI: 10.4236/ojmi.2014.43021
Abstract: Purpose: To increase the efficiency of densely encoded magnetization transfer imaging of the brain, we time-multiplex multiple slices within the same readout using simultaneous echo refocusing FLASH imaging with magnetization transfer (MT) preparation (MT-SER-FLASH). Materials and Methods: Inefficiency in total scan time results from the number of frequency samples needed for sufficient quality of quantitative parameter maps for a binary spin bath model. We present a highly efficient multiplexing method, simultaneous echo refocused magnetization transfer imaging (MT-SER-FLASH) for reducing the total scan time of MT imaging by one-third. The specific absorption rate (SAR) was also reduced by reducing the number of MT-pulses per volume. Results: 2D-MT-SER-FLASH is performed in 19 minutes rather than 1 hour, acceptable for routine clinical application. The SAR could be reduced to 69% instead of more than 100% with a standard 2D or 3D-FLASH with MT-preparation. Conclusion: The net reduction of scan time and SAR enables the use of quantitative model based magnetization transfer imaging within a clinical environment.
Modelling Magnetization Transfer Considering Spin-Locking Effects  [PDF]
Claus Kiefer
Open Journal of Medical Imaging (OJMI) , 2014, DOI: 10.4236/ojmi.2014.44027
Abstract: Purpose: Recently it was demonstrated that spin-locking (SL) effects can manifest as pseudo magnetization transfer (MT). To our best knowledge the MT models proposed so far cannot distinguish between saturation effects caused by the MT preparation pulses and SL phenomena. Therefore a new MT model is proposed. Materials and Methods: A binary spin-bath model for magnetization transfer was extended in that sense that SL effects are considered. The new modified spin bath model was tested for a phantom with different agar concentrates (2%, 4%, 8%) and a MnCl2 (0.3 mM) solution. Results: The mean fitting error is 3.2 times lower for the modified model compared to the original model. Especially the parameter F for the fractional part of the bounded proton pool describes the situation for the MnCl2 (F = 0) better than the original model (F = 0.004). Conclusion: The proposed mathematical modifications of the binary spin-bath model considering SL seem to be a step in the right direction in that sense that the effects associated with SL are not interpreted as magnetization transfer.
Diversity and abundance of orchid bees (Hymenoptera: Apidae, Euglossini) in a tropical rainforest succession
Rasmussen, Claus;
Neotropical Entomology , 2009, DOI: 10.1590/S1519-566X2009000100006
Abstract: euglossine bee males are easily lured to chemical baits imitating natural fragrances gathered by bees, providing a widely applied measure for estimating the diversity and abundance of euglossines. in here, i report the composition of euglossine bees in three lowland rainforest habitats of peru, a primary old forest, a reforested and managed forest, and a very disturbed forest. a total of 2,072 males of euglossine were collected, belonging to 33 species and four genera. although a comparable diversity relative to other studies from the amazonian region was found, no significant differences among the sampled areas were detected. perhaps, the short time and low intensity surveys here used (< 3 months) were not good enough indicators of forest disturbance without additional data. compared to other major studies on the euglossine bee fauna, loreto is most similar to the species assemblage reported from lowland rainforest in brazil (manaus), central peru (panguana) and southern peru (tambopata).
Quantum cosmology and the arrow of time
Kiefer, Claus;
Brazilian Journal of Physics , 2005, DOI: 10.1590/S0103-97332005000200014
Abstract: although most fundamental laws are invariant under time reversal, experience exhibits the presence of irreversible phenomena - the arrows of time. their origin lies in cosmology, and i argue that only quantum cosmology can provide the appropriate formal framework. after briefly reviewing the formalism, i discuss how a simple and natural boundary condition can lead to the observed arrows of time. this yields at the same time interesting consequences for black holes.
A new solution algorithm for skip-free processes to the left
Bauer,Claus;
Cubo (Temuco) , 2010, DOI: 10.4067/S0719-06462010000200011
Abstract: this paper proposes a new solution algorithm for steady state models describing skip-free processes to the left where each level has one phase. the computational complexity of the algorithm is independent of the number of levels of the system. if the skip parameter of the skip-free process is significantly smaller than the number of levels of the system, our algorithm numerically outperforms existing algorithms for skip-free processes. the proposed algorithm is based on a novel method for applying generalized fibonacci series to the solution of steady state models.
Russia and the OSCE - The Influence of Interested Third and Disinterested Fourth Parties on the Conflicts in Estonia and Moldova
Claus Neukirch
Journal on Ethnopolitics and Minority Issues in Europe , 2001,
Abstract: This article aims to analyse the influence of external actors on the domestic conditions surrounding the conflicts in Estonia and Moldova. It attempts to answer the question why the Moldovan conflict turned violent while the Estonian conflict remained peaceful.
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