33,921 research outputs found
GeoSay: A Geometric Saliency for Extracting Buildings in Remote Sensing Images
Automatic extraction of buildings in remote sensing images is an important
but challenging task and finds many applications in different fields such as
urban planning, navigation and so on. This paper addresses the problem of
buildings extraction in very high-spatial-resolution (VHSR) remote sensing (RS)
images, whose spatial resolution is often up to half meters and provides rich
information about buildings. Based on the observation that buildings in VHSR-RS
images are always more distinguishable in geometry than in texture or spectral
domain, this paper proposes a geometric building index (GBI) for accurate
building extraction, by computing the geometric saliency from VHSR-RS images.
More precisely, given an image, the geometric saliency is derived from a
mid-level geometric representations based on meaningful junctions that can
locally describe geometrical structures of images. The resulting GBI is finally
measured by integrating the derived geometric saliency of buildings.
Experiments on three public and commonly used datasets demonstrate that the
proposed GBI achieves the state-of-the-art performance and shows impressive
generalization capability. Additionally, GBI preserves both the exact position
and accurate shape of single buildings compared to existing methods
Segmentation and Restoration of Images on Surfaces by Parametric Active Contours with Topology Changes
In this article, a new method for segmentation and restoration of images on
two-dimensional surfaces is given. Active contour models for image segmentation
are extended to images on surfaces. The evolving curves on the surfaces are
mathematically described using a parametric approach. For image restoration, a
diffusion equation with Neumann boundary conditions is solved in a
postprocessing step in the individual regions. Numerical schemes are presented
which allow to efficiently compute segmentations and denoised versions of
images on surfaces. Also topology changes of the evolving curves are detected
and performed using a fast sub-routine. Finally, several experiments are
presented where the developed methods are applied on different artificial and
real images defined on different surfaces
Picasso, Matisse, or a Fake? Automated Analysis of Drawings at the Stroke Level for Attribution and Authentication
This paper proposes a computational approach for analysis of strokes in line
drawings by artists. We aim at developing an AI methodology that facilitates
attribution of drawings of unknown authors in a way that is not easy to be
deceived by forged art. The methodology used is based on quantifying the
characteristics of individual strokes in drawings. We propose a novel algorithm
for segmenting individual strokes. We designed and compared different
hand-crafted and learned features for the task of quantifying stroke
characteristics. We also propose and compare different classification methods
at the drawing level. We experimented with a dataset of 300 digitized drawings
with over 80 thousands strokes. The collection mainly consisted of drawings of
Pablo Picasso, Henry Matisse, and Egon Schiele, besides a small number of
representative works of other artists. The experiments shows that the proposed
methodology can classify individual strokes with accuracy 70%-90%, and
aggregate over drawings with accuracy above 80%, while being robust to be
deceived by fakes (with accuracy 100% for detecting fakes in most settings)
Cluster-formation in the Rosette molecular cloud at the junctions of filaments
For many years feedback processes generated by OB-stars in molecular clouds,
including expanding ionization fronts, stellar winds, or UV-radiation, have
been proposed to trigger subsequent star formation. However, hydrodynamic
models including radiation and gravity show that UV-illumination has little or
no impact on the global dynamical evolution of the cloud. The Rosette molecular
cloud, irradiated by the NGC2244 cluster, is a template region for triggered
star-formation, and we investigated its spatial and density structure by
applying a curvelet analysis, a filament-tracing algorithm (DisPerSE), and
probability density functions (PDFs) on Herschel column density maps, obtained
within the HOBYS key program. The analysis reveals not only the filamentary
structure of the cloud but also that all known infrared clusters except one lie
at junctions of filaments, as predicted by turbulence simulations. The PDFs of
sub-regions in the cloud show systematic differences. The two UV-exposed
regions have a double-peaked PDF we interprete as caused by shock compression.
The deviations of the PDF from the log-normal shape typically associated with
low- and high-mass star-forming regions at Av~3-4m and 8-10m, respectively, are
found here within the very same cloud. This shows that there is no fundamental
difference in the density structure of low- and high-mass star-forming regions.
We conclude that star-formation in Rosette - and probably in high-mass
star-forming clouds in general - is not globally triggered by the impact of
UV-radiation. Moreover, star formation takes place in filaments that arose from
the primordial turbulent structure built up during the formation of the cloud.
Clusters form at filament mergers, but star formation can be locally induced in
the direct interaction zone between an expanding HII--region and the molecular
cloud.Comment: A&A Letter, in pres
Collective cell durotaxis emerges from long-range intercellular force transmission
The ability of cells to follow gradients of extracellular matrix stiffness—durotaxis—has been implicated in development, fibrosis, and cancer. Here, we found multicellular clusters that exhibited durotaxis even if isolated constituent cells did not. This emergent mode of directed collective cell migration applied to a variety of epithelial cell types, required the action of myosin motors, and originated from supracellular transmission of contractile physical forces. To explain the observed phenomenology, we developed a generalized clutch model in which local stick-slip dynamics of cell-matrix adhesions was integrated to the tissue level through cell-cell junctions. Collective durotaxis is far more efficient than single-cell durotaxis; it thus emerges as a robust mechanism to direct cell migration during development, wound healing, and collective cancer cell invasion.Peer ReviewedPostprint (author's final draft
Myosin IIA-mediated forces regulate multicellular integrity during vascular sprouting
Angiogenic sprouting is a critical process involved in vascular network formation within tissues. During sprouting, tip cells and ensuing stalk cells migrate collectively into the extracellular matrix while preserving cell-cell junctions, forming patent structures that support blood flow. Although several signaling pathways have been identified as controlling sprouting, it remains unclear to what extent this process is mechanoregulated. To address this question, we investigated the role of cellular contractility in sprout morphogenesis, using a biomimetic model of angiogenesis. Three-dimensional maps of mechanical deformations generated by sprouts revealed that mainly leader cells, not stalk cells, exert contractile forces on the surrounding matrix. Surprisingly, inhibiting cellular contractility with blebbistatin did not affect the extent of cellular invasion but resulted in cell-cell dissociation primarily between tip and stalk cells. Closer examination of cell-cell junctions revealed that blebbistatin impaired adherens-junction organization, particularly between tip and stalk cells. Using CRISPR/Cas9-mediated gene editing, we further identified NMIIA as the major isoform responsible for regulating multicellularity and cell contractility during sprouting. Together, these studies reveal a critical role for NMIIA-mediated contractile forces in maintaining multicellularity during sprouting and highlight the central role of forces in regulating cell-cell adhesions during collective motility.R01 EB000262 - NIBIB NIH HHS; R01 HL115553 - NHLBI NIH HHSPublished versio
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