2,336 research outputs found
OpenSPIM - an open access platform for light sheet microscopy
Light sheet microscopy promises to revolutionize developmental biology by
enabling live in toto imaging of entire embryos with minimal phototoxicity. We
present detailed instructions for building a compact and customizable Selective
Plane Illumination Microscopy (SPIM) system. The integrated OpenSPIM hardware
and software platform is shared with the scientific community through a public
website, thereby making light sheet microscopy accessible for widespread use
and optimization to various applications.Comment: 7 pages, 3 figures, 6 supplementary videos, submitted to Nature
Methods, associated public website http://openspim.or
Magnetic order in the quasi-two-dimensional easy-plane XXZ model
A Green's-function theory of antiferromagnetic short-range and long-range
order (LRO) in the quasi-two-dimensional easy-plane XXZ model is
presented. As the main new result, {\it two} phase transitions due to the
combined influence of spatial and spin anisotropy are found, where below the
higher and lower N\'{e}el temperature there occurs LRO in the transverse and in
both the transverse and longitudinal spin correlators, respectively. Comparing
the theory with neutron-scattering data for the correlation length of , a very good agreement in the whole temperature dependence is
obtained. Moreover, for , , and the second phase with longitudinal LRO is predicted to
appear far below room temperature.Comment: 7 pages, 5 figure
Green's-function theory of the Heisenberg ferromagnet in a magnetic field
We present a second-order Green's-function theory of the one- and
two-dimensional S=1/2 ferromagnet in a magnetic field based on a decoupling of
three-spin operator products, where vertex parameters are introduced and
determined by exact relations. The transverse and longitudinal spin correlation
functions and thermodynamic properties (magnetization, isothermal magnetic
susceptibility, specific heat) are calculated self-consistently at arbitrary
temperatures and fields. In addition, exact diagonalizations on finite lattices
and, in the one-dimensional case, exact calculations by the Bethe-ansatz method
for the quantum transfer matrix are performed. A good agreement of the
Green's-function theory with the exact data, with recent quantum Monte Carlo
results, and with the spin polarization of a quantum Hall ferromagnet
is obtained. The field dependences of the position and height of the maximum in
the temperature dependence of the susceptibility are found to fit well to power
laws, which are critically analyzed in relation to the recently discussed
behavior in Landau's theory. As revealed by the spin correlation functions and
the specific heat at low fields, our theory provides an improved description of
magnetic short-range order as compared with the random phase approximation. In
one dimension and at very low fields, two maxima in the temperature dependence
of the specific heat are found. The Bethe-ansatz data for the field dependences
of the position and height of the low-temperature maximum are described by
power laws. At higher fields in one and two dimensions, the temperature of the
specific heat maximum linearly increases with the field.Comment: 9 pages, 9 figure
New Perspectives in Sinographic Language Processing Through the Use of Character Structure
Chinese characters have a complex and hierarchical graphical structure
carrying both semantic and phonetic information. We use this structure to
enhance the text model and obtain better results in standard NLP operations.
First of all, to tackle the problem of graphical variation we define
allographic classes of characters. Next, the relation of inclusion of a
subcharacter in a characters, provides us with a directed graph of allographic
classes. We provide this graph with two weights: semanticity (semantic relation
between subcharacter and character) and phoneticity (phonetic relation) and
calculate "most semantic subcharacter paths" for each character. Finally,
adding the information contained in these paths to unigrams we claim to
increase the efficiency of text mining methods. We evaluate our method on a
text classification task on two corpora (Chinese and Japanese) of a total of 18
million characters and get an improvement of 3% on an already high baseline of
89.6% precision, obtained by a linear SVM classifier. Other possible
applications and perspectives of the system are discussed.Comment: 17 pages, 5 figures, presented at CICLing 201
Efficient Bayesian-based Multi-View Deconvolution
Light sheet fluorescence microscopy is able to image large specimen with high
resolution by imaging the sam- ples from multiple angles. Multi-view
deconvolution can significantly improve the resolution and contrast of the
images, but its application has been limited due to the large size of the
datasets. Here we present a Bayesian- based derivation of multi-view
deconvolution that drastically improves the convergence time and provide a fast
implementation utilizing graphics hardware.Comment: 48 pages, 20 figures, 1 table, under review at Nature Method
Three-dimensional femtosecond laser nanolithography of crystals
Nanostructuring hard optical crystals has so far been exclusively feasible at
their surface, as stress induced crack formation and propagation has rendered
high precision volume processes ineffective. We show that the inner chemical
etching reactivity of a crystal can be enhanced at the nanoscale by more than
five orders of magnitude by means of direct laser writing. The process allows
to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm
feature sizes inside large crystals in absence of brittle fracture. To showcase
the unique potential of the technique, we fabricate photonic structures such as
sub-wavelength diffraction gratings and nanostructured optical waveguides
capable of sustaining sub-wavelength propagating modes inside yttrium aluminum
garnet crystals. This technique could enable the transfer of concepts from
nanophotonics to the fields of solid state lasers and crystal optics.Comment: Submitted Manuscript and Supplementary Informatio
Iterative graph cuts for image segmentation with a nonlinear statistical shape prior
Shape-based regularization has proven to be a useful method for delineating
objects within noisy images where one has prior knowledge of the shape of the
targeted object. When a collection of possible shapes is available, the
specification of a shape prior using kernel density estimation is a natural
technique. Unfortunately, energy functionals arising from kernel density
estimation are of a form that makes them impossible to directly minimize using
efficient optimization algorithms such as graph cuts. Our main contribution is
to show how one may recast the energy functional into a form that is
minimizable iteratively and efficiently using graph cuts.Comment: Revision submitted to JMIV (02/24/13
A high-level 3D visualization API for Java and ImageJ
BACKGROUND: Current imaging methods such as Magnetic Resonance Imaging (MRI), Confocal microscopy, Electron Microscopy (EM) or Selective Plane Illumination Microscopy (SPIM) yield three-dimensional (3D) data sets in need of appropriate computational methods for their analysis. The reconstruction, segmentation and registration are best approached from the 3D representation of the data set.
RESULTS: Here we present a platform-independent framework based on Java and Java 3D for accelerated rendering of biological images. Our framework is seamlessly integrated into ImageJ, a free image processing package with a vast collection of community-developed biological image analysis tools. Our framework enriches the ImageJ software libraries with methods that greatly reduce the complexity of developing image analysis tools in an interactive 3D visualization environment. In particular, we provide high-level access to volume rendering, volume editing, surface extraction, and image annotation. The ability to rely on a library that removes the low-level details enables concentrating software development efforts on the algorithm implementation parts.
CONCLUSIONS: Our framework enables biomedical image software development to be built with 3D visualization capabilities with very little effort. We offer the source code and convenient binary packages along with extensive documentation at http://3dviewer.neurofly.de
Image-based Analysis of Patterns Formed in Drying Drops
Image processing and pattern recognition offer a useful and versatile method
for optically characterizing drops of a colloidal solution during the drying
process and in its final state. This paper exploits image processing techniques
applied to cross-polarizing microscopy to probe birefringence and the
bright-field microscopy to examine the morphological patterns. The
bio-colloidal solution of interest is a mixture of water, liquid crystal (LC)
and three different proteins [lysozyme (Lys), myoglobin (Myo), and bovine serum
albumin (BSA)], all at a fixed relative concentration. During the drying
process, the LC phase separates and becomes optically active detectable through
its birefringence. Further, as the protein concentrates, it forms cracks under
strain due to the evaporation of water. The mean intensity profile of the
drying process is examined using an automated image processing technique that
reveals three unique regimes: a steady upsurge, a speedy rise, and an eventual
saturation. The high values of standard deviation show the complexity, the
roughness, and inhomogeneity of the image surface. A semi-automated image
processing technique is proposed to quantify the distance between the
consecutive cracks by converting those into high contrast images. The outcome
of the image analysis correlates with the initial state of the mixture, the
nature of the proteins, and the mechanical response of the final patterns. The
paper reveals new insights on the self-assembly of the macromolecules during
the drying mechanism of any aqueous solution
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