The Lamina Cribrosa is a part of the optic nerve head acting as a scaffold for collecting the retinal ganglion cell axons. It can be modeled as a poroelastic material where the saturated porosity ...stands for the capillary network running inside the collagen beams. Our aim is to study the interaction between tissue porosity, deformation and hemodynamics. To this end we first focus on the derivation of a poroelastic model in a rather general case, using as a prototype a model of species diffusion in an elastic material. Then we outline the clinical significance of the mechanical behavior of the Lamina Cribrosa and show, through numerical simulations, how an increased intraocular pressure results in a deformation affecting porosity and blood perfusion. We emphasize how the model behavior relies on the free energy expression.
This Letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97 GeV/c bunched and polarized deuteron beam in the Cooler Synchrotron ...(COSY) storage ring in order to control both the precession rate (≈121 kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a 1 standard deviation range of σ=0.21 rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.
In the aspect of medical imaging, it is crucial to obtain certain structures or even cellular features in microscopic resolution. Unfortunately, the field of view is inherently limited by the ...capability of capturing instruments. Thus, mosaicing of such microstructure is of utmost importance in order to restore original visual information for establishing broad structure morphology. Large panoramic images with microscopic resolution can be rewarding and practical for conducting comprehensive observation and exploration of the object of interest and surrounding biological structure. But mosaicing can be challenging if there are deformable, motion-blurred, textureless, feature-poor frames. Feature-based methods perform poorly in such cases for the lack of distinctive keypoints. Standard single block correlation matching strategies might not provide robust registration due to deformable content. In addition, the panorama suffers if there is motion blur present in a sequence. To handle these challenges, we propose a novel algorithm, Deformable Normalized Cross Correlation (DNCC) image matching with RANSAC to establish robust registration. Besides, to produce seamless panorama from motion-blurred frames we present gradient blending method based on image edge information. The DNCC algorithm is applied on Frog Mesentery sequences. Our result is compared with PSS/AutoStitch 1, 2 to establish the efficiency and robustness of the proposed DNCC method.
When a layer of fluid is oscillated up and down with a sufficiently large amplitude, patterns form on the surface, a phenomenon first observed by Faraday. A wide variety of such patterns have been ...observed from regular squares and hexagons to superlattice and quasipatterns and more exotic patterns such as oscillons. Previous work has investigated the mechanisms of pattern selection using the tools of symmetry and bifurcation theory. The hypotheses produced by these generic arguments have been tested against an equation derived by Zhang and Viñals in the weakly viscous and large depth limit. However, in contrast, many of the experiments use shallow viscous layers of fluid to counteract the presence of high frequency weakly damped modes that can make patterns hard to observe. Here we develop a weakly nonlinear analysis of the full Navier-Stokes equations for the two-frequency excitation Faraday experiment. The problem is formulated for general depth, although results are presented only for the infinite depth limit. We focus on a few particular cases where detailed experimental results exist and compare our analytical results with the experimental observations. Good agreement with the experimental results is found.
This paper provides an overview of the worldwide first commissioning of a gantry beamline with a rotator at the MedAustron synchrotron-based proton/ion cancer therapy facility in Wiener Neustadt, ...Austria. The gantry beamline consists of the high energy beam transfer (HEBT) line and the gantry beam transport system. It transports the beam from the synchrotron to the gantry-room isocenter. The HEBT transports the beam from the synchrotron to the gantry entrance, which is the coupling point between the HEBT and the gantry. The rotator is one of the HEBT modules, thus it is an integral part of the gantry beamline. The MedAustron rotator is the worldwide first rotator system used to match slowly extracted asymmetric beams from the synchrotron to the rotating gantry. In this paper, main attention is paid to ion-optical and beam-alignment aspects of the beamline commissioning. A novel orbit-correction and beam-alignment technique has been developed specifically for the beamline with the rotator. While the theoretical concept of the rotator has existed for almost two decades, the MedAustron rotator is the first hardware implementation of this concept all over the world. The presented overview of the beamline commissioning includes a description of the principal technical solutions and main results of the first beam-transport measurements. Since the measured beam size and beam position agree well with theoretical predictions, one can conclude that the proof-of-concept of the rotator-matching has been successfully accomplished.
Automated curvilinear image segmentation is a crucial step to characterize and quantify the morphology of blood vessels across scale. We propose a dual pipeline RF_OFB+U-NET that fuses U-Net deep ...learning features with a low level image feature filter bank using the random forests classifier for vessel segmentation. We modify the U-Net CNN architecture to provide a foreground vessel regression likelihood map that is used to segment both arteriole and venule blood vessels in mice dura mater tissues. The hybrid approach combining both hand-crafted and learned features was tested on 60 epifluores-cence microscopy images and improved the segmentation of thin vessel structures by nearly 5% using the Dice similarity coefficient compared to U-Net.
The main goal of this article is to investigate the capability of an operator-splitting/finite elements based methodology at handling accurately incompressible viscous flow at large Reynolds number ...(Re) in regions with corners and curved boundaries. To achieve this goal the authors have selected a wall-driven flow in a semi-circular cavity. On the basis of the numerical experiments reported in this article it seems that the method under investigation has no difficulty at capturing the formation of primary, secondary and tertiary vortices as Re increases; it has also the capability of identifying a Hopf bifurcation phenomenon taking place around Re=6600.
This paper describes a time-marking system that enables a measurement of the in-plane (horizontal) polarization of a 0.97-GeV/c deuteron beam circulating in the Cooler Synchrotron (COSY) at the ...Forschungszentrum Julich. The clock time of each polarimeter event is used to unfold the 120-kHz spin precession and assign events to bins according to the direction of the horizontal polarization. After accumulation for one or more seconds, the down-up scattering asymmetry can be calculated for each direction and matched to a sinusoidal function whose magnitude is proportional to the horizontal polarization. This requires prior knowledge of the spin tune or polarization precession rate. An initial estimate is refined by resorting the events as the spin tune is adjusted across a narrow range and searching for the maximum polarization magnitude. The result is biased toward polarization values that are too large, in part because of statistical fluctuations but also because sinusoidal fits to even random data will produce sizable magnitudes when the phase is left free to vary. An analysis procedure is described that matches the time dependence of the horizontal polarization to templates based on emittance-driven polarization loss while correcting for the positive bias. This information will be used to study ways to extend the horizontal polarization lifetime by correcting spin tune spread using ring sextupole fields and thereby to support the feasibility of searching for an intrinsic electric dipole moment using polarized beams in a storage ring. This paper is a combined effort of the Storage Ring EDM collaboration and the JEDI collaboration.
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