311 research outputs found
Conformational Dynamics Guides Coherent Exciton Migration in Conjugated Polymer Materials: A First-Principles Quantum Dynamical Study
We report on high-dimensional quantum dynamical simulations of
torsion-induced exciton migration in a single-chain oligothiophene segment
comprising twenty repeat units, using a first-principles parametrized Frenkel
J-aggregate Hamiltonian. Starting from an initial inter-ring torsional defect,
these simulations provide evidence of an ultrafast two-time scale process at
low temperatures, involving exciton-polaron formation within tens of
femtoseconds, followed by torsional relaxation on a ~300 femtosecond time
scale. The second step is the driving force for exciton migration, as initial
conjugation breaks are removed by dynamical planarization. The quantum coherent
nature of the elementary exciton migration step is consistent with experimental
observations highlighting the correlated and vibrationally coherent nature of
the dynamics on ultrafast time scales.Comment: 4 pages, 4 figure
Cantilever micro-rheometer for the dcharacterization of sugar solutions
The volume required for the rheological characterization of fluids can be minimized by using micromechanical cantilevers as viscosity sensors. Here, a simple measurement tool for the characterization of sugar solutions is proposed. The sensor consists of a micromechanical cantilever as used in an atomic force microscopy which is integrated into a closed fluid handling system. Fluid properties are derived from an analysis of the power spectral density of the fluctuations of the cantilever deflection signal. The data acquisition system is operated with standard consumer computer components, which limits the costs for the hardware. Measurements with different sugar solutions indicate that the sensor system provides reliable viscosity values for sugar concentrations as they occur in biological systems. The viscosities of the sugar solutions could be evaluated with an error smaller than 5%
Automated processing for map generalization using web services
In map generalization various operators are applied to the features of a map in order to maintain and improve the legibility of the map after the scale has been changed. These operators must be applied in the proper sequence and the quality of the results must be continuously evaluated. Cartographic constraints can be used to define the conditions that have to be met in order to make a map legible and compliant to the user needs. The combinatorial optimization approaches shown in this paper use cartographic constraints to control and restrict the selection and application of a variety of different independent generalization operators into an optimal sequence. Different optimization techniques including hill climbing, simulated annealing and genetic deep search are presented and evaluated experimentally by the example of the generalization of buildings in blocks. All algorithms used in this paper have been implemented in a web services framework. This allows the use of distributed and parallel processing in order to speed up the search for optimized generalization operator sequence
A Supervised Approach to Delineate Built-Up Areas for Monitoring and Analysis of Settlements
Monitoring urban growth and measuring urban sprawl is essential for improving urban planning and development. In this paper, we introduce a supervised approach for the delineation of urban areas using commonly available topographic data and commercial GIS software. The method uses a supervised parameter optimization approach along with buffer-based quality measuring method. The approach was developed, tested and evaluated in terms of possible usage in monitoring built-up areas in spatial science at a very fine-grained level. Results show that built-up area boundaries can be delineated automatically with higher quality compared to the settlement boundaries actually used. The approach has been applied to 166 settlement bodies in Germany. The study shows a very efficient way of extracting settlement boundaries from topographic data and maps and contributes to the quantification and monitoring of urban sprawl. Moreover, the findings from this study can potentially guide policy makers and urban planners from other countries
Use of multiple singular value decompositions to analyze complex intracellular calcium ion signals
We compare calcium ion signaling () between two exposures;
the data are present as movies, or, more prosaically, time series of images.
This paper describes novel uses of singular value decompositions (SVD) and
weighted versions of them (WSVD) to extract the signals from such movies, in a
way that is semi-automatic and tuned closely to the actual data and their many
complexities. These complexities include the following. First, the images
themselves are of no interest: all interest focuses on the behavior of
individual cells across time, and thus, the cells need to be segmented in an
automated manner. Second, the cells themselves have 100 pixels, so that they
form 100 curves measured over time, so that data compression is required to
extract the features of these curves. Third, some of the pixels in some of the
cells are subject to image saturation due to bit depth limits, and this
saturation needs to be accounted for if one is to normalize the images in a
reasonably unbiased manner. Finally, the signals have
oscillations or waves that vary with time and these signals need to be
extracted. Thus, our aim is to show how to use multiple weighted and standard
singular value decompositions to detect, extract and clarify the signals. Our signal extraction methods then lead to simple although
finely focused statistical methods to compare signals
across experimental conditions.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS253 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Übungsklausur für das erste Staatsexamen: »Brandanschlag nach Trennung«
Dieser Beitrag ist mit Zustimmung des Rechteinhabers (De Gruyter) frei zugänglich.Peer Reviewe
Alternative options of using processing knowledge to populate ontologies for the recognition of urban concepts
In this paper, we present an ontology-driven approach for cartographic pattern recognition in support of map generalisation. Spatial patterns are formalised by means of ontologies which are then used to deductively trigger appropriate low level pattern recognition techniques. Modelling ontologies suited for spatial pattern recognition is discussed by example of an ontology of terraced houses. The paper subsequently focuses on approaches for inferring the instances of higher level concepts. Three different approaches are employed to detect terraced houses in Ordnance Survey MasterMap® vector data: Weighted summation; Joint Bayes classifier; and Support Vector Machines. An evaluation by comparison to a manual classification reveals that weighted summation and the Joint Bayes classifier both have satisfactory prediction accuracy, but the Joint Bayes classifier has advantages when considering the calibration effort involved. In conclusion, we claim that the ontology-driven approach better captures the complex structure of spatial patterns and provides enhanced transparency and flexibility of the pattern recognition process in comparison to conventional, purely geometric and/or statistical techniques
Osteopontin: a leading candidate adhesion molecule for implantation in pigs and sheep
Osteopontin (OPN; also known as Secreted Phosphoprotein 1, SPP1) is a secreted extra-cellular matrix (ECM) protein that binds to a variety of cell surface integrins to stimulate cell-cell and cell-ECM adhesion and communication. It is generally accepted that OPN interacts with apically expressed integrin receptors on the uterine luminal epithelium (LE) and conceptus trophectoderm to attach the conceptus to the uterus for implantation. Research conducted with pigs and sheep has significantly advanced understanding of the role(s) of OPN during implantation through exploitation of the prolonged peri-implantation period of pregnancy when elongating conceptuses are free within the uterine lumen requiring extensive paracrine signaling between conceptus and endometrium. This is followed by a protracted and incremental attachment cascade of trophectoderm to uterine LE during implantation, and development of a true epitheliochorial or synepitheliochorial placenta exhibited by pigs and sheep, respectively. In pigs, implanting conceptuses secrete estrogens which induce the synthesis and secretion of OPN in adjacent uterine LE. OPN then binds to αvβ6 integrin receptors on trophectoderm, and the αvβ3 integrin receptors on uterine LE to bridge conceptus attachment to uterine LE for implantation. In sheep, implanting conceptuses secrete interferon tau that prolongs the lifespan of CL. Progesterone released by CL then induces OPN synthesis and secretion from the endometrial GE into the uterine lumen where OPN binds integrins expressed on trophectoderm (αvβ3) and uterine LE (identity of specific integrins unknown) to adhere the conceptus to the uterus for implantation. OPN binding to the αvβ3 integrin receptor on ovine trophectoderm cells induces in vitro focal adhesion assembly, a prerequisite for adhesion and migration of trophectoderm, through activation of: 1) P70S6K via crosstalk between FRAP1/MTOR and MAPK pathways; 2) MTOR, PI3K, MAPK3/MAPK1 (Erk1/2) and MAPK14 (p38) signaling to stimulate trohectoderm cell migration; and 3) focal adhesion assembly and myosin II motor activity to induce migration of trophectoderm cells. Further large in vivo focal adhesions assemble at the uterine-placental interface of both pigs and sheep and identify the involvement of sizable mechanical forces at this interface during discrete periods of trophoblast migration, attachment and placentation in both species. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/2049-1891-5-56) contains supplementary material, which is available to authorized users
Phenotypic profiles of cultured glomerular cells following repeated cycles of hydrocarbon injury
Phenotypic profiles of cultured glomerular cells following repeated cycles of hydrocarbon injury.BackgroundThe glomerulus has been implicated as a target of hydrocarbon injury in vitro and in vivo. In the present studies, the phenotypic profiles of cultured rat glomerular cells (GCs) following repeated cycles of hydrocarbon injury were evaluated. Cultured GCs were incubated for 24 hours with benzo[a]pyrene (BaP; 3 μmol/L), a prototypical polycyclic aromatic hydrocarbon, and were allowed to recover overnight before two additional cycles of chemical challenge during serial propagation in vitro. At the end of this regimen, control cultures were characterized by predominance of fusiform cells that grew in “hills and valleys,” while GCs subjected to hydrocarbon injury displayed an epithelial morphology characterized by a rounded, polygonal shape clearly distinct from that normally exhibited by glomerular mesangial cells (GMCs) in culture.MethodsIndirect immunofluorescent detection of cell markers was conducted to identify cells of mesenchymal or epithelial origin. Measurements of DNA synthesis and cell number were performed to determine proliferative capacities of the different cell types in response to hydrocarbon challenge.ResultsImmunofluorescence studies revealed that control GC cultures contained mostly α-smooth muscle (SM) actin-positive cells, with a few (5.1%± 2.6) E-cadherin–positive cells occasionally identified. In contrast, BaP-treated cultures exhibited a mixed cell population in which E-cadherin–positive cells were predominant (66.6%± 4.1). Single-cell cloning of naive cultures of GCs yielded four clones, three of which exhibited a fusiform morphology and were α-SM actin positive (SCC 1 through SCC 3) and one (SCC 4E) that exhibited epithelial characteristics similar to those found in hydrocarbon-treated cultures. Immunofluorescence studies showed that epithelial cells in hydrocarbon-treated cultures, as well as SCC 4E-derived clones, were vimentin positive and cytokeratin negative, characteristics similar to glomerular visceral epithelial cells (GVECs). DNA synthesis and cell proliferation in clone SCC 1 were decreased following acute BaP challenge, while growth rates in SCC 4E-derived clones were unaffected by hydrocarbon injury. Repeated cycles of hydrocarbon challenge in clonal populations yielded different profiles of DNA synthesis, with significant decreases in SCC 1 and no changes in SCC 4E.ConclusionsThese observations suggest that hydrocarbon injury induces differential responses in cells of the glomerulus, resulting in inhibition of GMCs and selective growth advantage of GVECs. These alterations are reminiscent of critical events described in the pathogenesis of focal segmental glomerulosclerosis and raise important questions about the pathogenesis of hydrocarbon-induced nephropathies
Mechanism of Action of Phenethylisothiocyanate and Other Reactive Oxygen Species-Inducing Anticancer Agents
Reactive oxygen species (ROS)-inducing anticancer agents such as phenethylisothiocyanate (PEITC) activate stress pathways for killing cancer cells. Here we demonstrate that PEITC-induced ROS decreased expression of microRNA 27a (miR-27a)/miR-20a:miR-17-5p and induced miR-regulated ZBTB10/ZBTB4 and ZBTB34 transcriptional repressors, which, in turn, downregulate specificity protein (Sp) transcription factors (TFs) Sp1, Sp3, and Sp4 in pancreatic cancer cells. Decreased expression of miR-27a/miR-20a:miR-17-5p by PEITC-induced ROS is a key step in triggering the miR-ZBTB Sp cascade leading to downregulation of Sp TFs, and this is due to ROS-dependent epigenetic effects associated with genome-wide shifts in repressor complexes, resulting in decreased expression of Myc and the Myc-regulated miRs. Knockdown of Sp1 alone by RNA interference also induced apoptosis and decreased pancreatic cancer cell growth and invasion, indicating that downregulation of Sp transcription factors is an important common mechanism of action for PEITC and other ROS-inducing anticancer agents
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