7,321 research outputs found
Learning from medical data streams: an introduction
Clinical practice and research are facing a new challenge created by the rapid growth of health information science and technology, and the complexity and volume of biomedical data. Machine learning from medical data streams is a recent area of research that aims to provide better knowledge extraction and evidence-based clinical decision support in scenarios where data are produced as a continuous flow. This year's edition of AIME, the Conference on Artificial Intelligence in Medicine, enabled the sound discussion of this area of research, mainly by the inclusion of a dedicated workshop. This paper is an introduction to LEMEDS, the Learning from Medical Data Streams workshop, which highlights the contributed papers, the invited talk and expert panel discussion, as well as related papers accepted to the main conference
Liquid crystals boojum-colloids
Colloidal particles dispersed in a liquid crystal lead to distortions of the
director field. The distortions are responsible for long-range effective
colloidal interactions whose asymptotic behaviour is well understood. The short
distance behaviour of the interaction, however, is sensitive to the structure
and dynamics of the topological defects nucleated near the colloidal particles
in the strong anchoring regime. The full non-linear theory is required in order
to determine the interaction at short separations. Spherical colloidal
particles with sufficiently strong planar degenerate anchoring nucleate a pair
of antipodal surface topological defects, known as boojums. We use the
Landau-de Gennes formalism in order to resolve the mesoscopic structure of the
boojum cores and to determine the pairwise colloidal interaction. We compare
the results in three (3D) and two (2D) spatial dimensions. The corresponding
free energy functionals are minimized numerically using finite elements with
adaptive meshes. Boojums are always point-like in 2D, but acquire a rather
complex structure in 3D which depends on the combination of the anchoring
potential, the radius of the colloid, the temperature and the LC elastic
anisotropy. We identify three types of defect cores in 3D which we call single,
double and split core boojums, and investigate the associated structural
transitions. In the presence of two colloidal particles there are substantial
re-arrangements of the defects at short distances, both in 3D and 2D. These
re-arrangements lead to qualitative changes in the force-distance profile when
compared to the asymptotic quadrupole-quadrupole interaction. In line with the
experimental results, the presence of the defects prevents coalescence of the
colloidal particles in 2D, but not in 3D systems.Comment: 18 pages, 21 figure
Colloidal interactions in two dimensional nematics
The interaction between two disks immersed in a 2D nematic is investigated
(i) analitically using the tensor order parameter formalism for the nematic
configuration around isolated disks and (ii) numerically using finite element
methods with adaptive meshing to minimize the corresponding Landau-de Gennes
free energy. For strong homeotropic anchoring, each disk generates a pair of
defects with one-half topological charge responsible for the 2D quadrupolar
interaction between the disks at large distances. At short distance, the
position of the defects may change, leading to unexpected complex interactions
with the quadrupolar repulsive interactions becoming attractive. This short
range attraction in all directions is still anisotropic. As the distance
between the disks decreases their preferred relative orientation with respect
to the far-field nematic director changes from oblique to perpendicular.Comment: 7 pages, 7 figure
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