7,649 research outputs found
Collection, spillback, and dissipation in pedestrian evacuation: A network-based method
We present a method of predicting pedestrian route choice behavior and physical congestion during the evacuation of indoor areas with internal obstacles. Under the proposed method, a network is first constructed by discretizing the space into regular hexagonal cells and giving these cells potentials before a modified cell transmission model is employed to predict the evolution of pedestrian flow in the network over time and space. Several properties of this cell transmission model are explored. The method can be used to predict the evolution of pedestrian flow over time and space in indoor areas with internal obstacles and to investigate the collection, spillback, and dissipation behavior of pedestrians passing through a bottleneck. The cell transmission model is further extended to imitate the movements of multiple flows of pedestrians with different destinations. An algorithm based on generalized cell potential is also developed to assign the pedestrian flow. © 2010 Elsevier Ltd.postprin
Topological descriptors for 3D surface analysis
We investigate topological descriptors for 3D surface analysis, i.e. the
classification of surfaces according to their geometric fine structure. On a
dataset of high-resolution 3D surface reconstructions we compute persistence
diagrams for a 2D cubical filtration. In the next step we investigate different
topological descriptors and measure their ability to discriminate structurally
different 3D surface patches. We evaluate their sensitivity to different
parameters and compare the performance of the resulting topological descriptors
to alternative (non-topological) descriptors. We present a comprehensive
evaluation that shows that topological descriptors are (i) robust, (ii) yield
state-of-the-art performance for the task of 3D surface analysis and (iii)
improve classification performance when combined with non-topological
descriptors.Comment: 12 pages, 3 figures, CTIC 201
Tunable ultranarrow linewidth of cavity induced by interacting dark resonances
A scheme for getting a tunable ultranarrow linewidth of a cavity due to an
embedded four-level atomic medium with double-dark resonances is proposed. It
is shown that the steep dispersion induced by double-dark resonances in the
transparency window leads to the ultranarrow transmission peak. Compared with
the case of a single-dark-resonance system, the linewidth can be narrowed even
by one order under proper conditions. Furthermore, the position of the
ultranarrow peak can be engineered by varying the intensity and detuning of the
control field.Comment: 4 pages, 5 figure
Cerebral malaria: Gamma-interferon redux
There are two theories that seek to explain the pathogenesis of cerebral malaria, the mechanical obstruction hypothesis and the immunopathology hypothesis. Evidence consistent with both ideas has accumulated from studies of the human disease and experimental models. Thus, some combination of these concepts seems necessary to explain the very complex pattern of changes seen in cerebral malaria. The interactions between malaria parasites, erythrocytes, the cerebral microvascular endothelium, brain parenchymal cells, platelets and microparticles need to be considered. One factor that seems able to knit together much of this complexity is the cytokine interferon-gamma (IFN-?). In this review we consider findings from the clinical disease, in vitro models and the murine counterpart of human cerebral malaria in order to evaluate the roles played by IFN-? in the pathogenesis of this often fatal and debilitating condition. © 2014 Hunt, Ball, Hansen, Khaw, Guo, Bakmiwewa, Mitchell, Combes and Grau
Evolution of Wurtzite Structured GaAs Shells Around InAs Nanowire Cores
GaAs was radially deposited on InAs nanowires by metal–organic chemical vapor deposition and resultant nanowire heterostructures were characterized by detailed electron microscopy investigations. The GaAs shells have been grown in wurtzite structure, epitaxially on the wurtzite structured InAs nanowire cores. The fundamental reason of structural evolution in terms of material nucleation and interfacial structure is given
Dynamical Axion Field in Topological Magnetic Insulators
Axions are very light, very weakly interacting particles postulated more than
30 years ago in the context of the Standard Model of particle physics. Their
existence could explain the missing dark matter of the universe. However,
despite intensive searches, they have yet to be detected. In this work, we show
that magnetic fluctuations of topological insulators couple to the
electromagnetic fields exactly like the axions, and propose several experiments
to detect this dynamical axion field. In particular, we show that the axion
coupling enables a nonlinear modulation of the electromagnetic field, leading
to attenuated total reflection. We propose a novel optical modulators device
based on this principle.Comment: 5 pages, 3 figure
Removal mechanisms and plant species selection by bioaccumulative factors in surface flow constructed wetlands (CWs): In the case of triclosan
© 2015 Elsevier B.V. Plants can bioaccumulate triclosan and bond with microbes and sediments in constructed wetlands (CWs) as well. However, little is known regarding the species-specific removal mechanism of CWs components and the selection of suitable wetland plant species for triclosan disposal. In this work, the use of bioaccumulation factors (BAFs) and biota to sediment accumulation factors (BSAFs) for choosing the best triclosan removal plant species was studied in laboratory-scale CWs. By the end of the experiment, over 80% of triclosan was removed and a specie-effect distribution was revealed in CWs with emergent, submerged and floating plants. By mass balance calculation, negative correlation between triclosan concentration in plants and degradation process was observed. The significant correlations between Log BSAFs values and triclosan concentration in plants or degradation contribution made it possible and reasonable in wetland plants selection. Introductions on plant species were provided considering the target removal process or regulation method. This work provided new information on plant species selection in CWs for triclosan removal or its emergency remediation by using bioaccumulative factors
Parameterized Single-Exponential Time Polynomial Space Algorithm for Steiner Tree
"In the Steiner tree problem, we are given as input a connected n-vertex graph with edge weights in {1,2,...,W}, and a subset of k terminal vertices. Our task is to compute a minimum-weight tree that contains all the terminals. We give an algorithm for this problem with running time O(7.97^k n^4 log W) using O(n^3 log nW log k) space. This is the first single-exponential time, polynomial-space FPT algorithm for the weighted Steiner tree problem."
PLEASE NOTE:This is an author-created version that the author has self-archived to the "Aaltodoc" (aaltodoc.aalto.fi) faculty-level repository at Aalto University. The final publication is available at link.springer.com via the link http://dx.doi.org/10.1007/978-3-662-47672-7_40Peer reviewe
Preconditioning of mesenchymal stromal cells with low-intensity ultrasound: influence on chondrogenesis and directed SOX9 signaling pathways
Background: Continuous low-intensity ultrasound (cLIUS) facilitates the chondrogenic differentiation of human mesenchymal stromal cells (MSCs) in the absence of exogenously added transforming growth factor-beta (TGFβ) by upregulating the expression of transcription factor SOX9, a master regulator of chondrogenesis. The present study evaluated the molecular events associated with the signaling pathways impacting SOX9 gene and protein expression under cLIUS.
Methods: Human bone marrow-derived MSCs were exposed to cLIUS stimulation at 14 kPa (5 MHz, 2.5 Vpp) for 5 min. The gene and protein expression of SOX9 was evaluated. The specificity of SOX9 upregulation under cLIUS was determined by treating the MSCs with small molecule inhibitors of select signaling molecules, followed by cLIUS treatment. Signaling events regulating SOX9 expression under cLIUS were analyzed by gene expression, immunofluorescence staining, and western blotting.
Results: cLIUS upregulated the gene expression of SOX9 and enhanced the nuclear localization of SOX9 protein when compared to non-cLIUS-stimulated control. cLIUS was noted to enhance the phosphorylation of the signaling molecule ERK1/2. Inhibition of MEK/ERK1/2 by PD98059 resulted in the effective abrogation of cLIUS-induced SOX9 expression, indicating that cLIUS-induced SOX9 upregulation was dependent on the phosphorylation of ERK1/2. Inhibition of integrin and TRPV4, the upstream cell-surface effectors of ERK1/2, did not inhibit the phosphorylation of ERK1/2 and therefore did not abrogate cLIUS-induced SOX9 expression, thereby suggesting the involvement of other mechanoreceptors. Consequently, the effect of cLIUS on the actin cytoskeleton, a mechanosensitive receptor regulating SOX9, was evaluated. Diffused and disrupted actin fibers observed in MSCs under cLIUS closely resembled actin disruption by treatment with cytoskeletal drug Y27632, which is known to increase the gene expression of SOX9. The upregulation of SOX9 under cLIUS was, therefore, related to cLIUS-induced actin reorganization. SOX9 upregulation induced by actin reorganization was also found to be dependent on the phosphorylation of ERK1/2.
Conclusions: Collectively, preconditioning of MSCs by cLIUS resulted in the nuclear localization of SOX9, phosphorylation of ERK1/2 and disruption of actin filaments, and the expression of SOX9 was dependent on the phosphorylation of ERK1/2 under cLIUS
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