Scanline calculation of radial influence for image processing

Efficient methods for the calculation of radial influence are described and applied to two image processing problems, digital halftoning and mixed content image compression. The methods operate recursively on scanlines of image values, spreading intensity from scanline to scanline in proportions approximating a Cauchy distribution. For error diffusion halftoning, experiments show that this recursive scanline spreading provides an ideal pattern of distribution of error. Error diffusion using masks generated to provide this distribution of error alleviate error diffusion "worm" artifacts. The recursive scanline by scanline application of a spreading filter and a complementary filter can be used to reconstruct an image from its horizontal and vertical pixel difference values. When combined with the use of a downsampled image the reconstruction is robust to incomplete and quantized pixel difference data. Such gradient field integration methods are described in detail proceeding from representation of images by gradient values along contours through to a variety of efficient algorithms. Comparisons show that this form of gradient field integration by convolution provides reduced distortion compared to other high speed gradient integration methods. The reduced distortion can be attributed to success in approximating a radial pattern of influence. An approach to edge-based image compression is proposed using integration of gradient data along edge contours and regularly sampled low resolution image data. This edge-based image compression model is similar to previous sketch based image coding methods but allows a simple and efficient calculation of an edge-based approximation image. A low complexity implementation of this approach to compression is described. The implementation extracts and represents gradient data along edge contours as pixel differences and calculates an approximate image by performing integration of pixel difference data by scanline convolution. The implementation was developed as a prototype for compression of mixed content image data in printing systems. Compression results are reported and strengths and weaknesses of the implementation are identified

Virtual viewpoint three-dimensional panorama

Conventional panoramic images are known to provide for an enhanced field of view in which the scene always has a fixed appearance. The idea presented in this paper focuses on the use of the concept of virtual viewpoint creation to generate different panoramic images of the same scene with three-dimensional component. Three-dimensional effect in a resultant panorama is realized by superimposing a stereo-pair of panoramic images

The magnetic fields of large Virgo Cluster spirals

Because of its proximity the Virgo Cluster is an excellent target for studying interactions of galaxies with the cluster environment. Both the high-velocity tidal interactions and effects of ram pressure stripping by the intracluster gas can be investigated. Optical and/or \ion{H}{i} observations do not always show effects of weak interactions between galaxies and their encounters with the cluster medium. For this reason we searched for possible anomalies in the magnetic field structure in Virgo Cluster spirals which could be attributed to perturbations in their gas distribution and kinematics. Five angularly large Virgo Cluster spiral galaxies (NGC 4501, NGC 4438, NGC 4535, NGC 4548 and NGC 4654) were the targets for a sensitive total power and polarization study using the 100-m radio telescope in Effelsberg at 4.85 GHz. For two objects polarization data at higher frequencies have been obtained allowing Faraday rotation analysis. Distorted magnetic field structures were identified in all galaxies. Interaction-induced magnetized outflows were found in NGC 4438 (due to nuclear activity) and NGC 4654 (a combination of tidal tails and ram pressure effects). Almost all objects (except the anaemic NGC 4548) exhibit distortions in polarized radio continuum attributable to influence of the ambient gas. For some galaxies they agree with observations of other species, but sometimes (NGC 4535) the magnetic field is the only tracer of the interaction with the cluster environment. The cluster environment clearly affects the evolution of the galaxies due to ram pressure and tidal effects. Magnetic fields provide a very long-lasting memory of past interactions. Therefore, they are a good tracer of weak interactions which are difficult to detect by other observations.Comment: 13 pages, 12 figure

Toward Understanding the Origin of Turbulence in Molecular Clouds: Small Scale Structures as Units of Dynamical Multi-Phase Interstellar Medium

In order to investigate the origin of the interstellar turbulence, detailed observations in the CO J=1--0 and 3--2 lines have been carried out in an interacting region of a molecular cloud with an HII region. As a result, several 1,000 to 10,000 AU scale cloudlets with small velocity dispersion are detected, whose systemic velocities have a relatively large scatter of a few km/s. It is suggested that the cloud is composed of small-scale dense and cold structures and their overlapping effect makes it appear to be a turbulent entity as a whole. This picture strongly supports the two-phase model of turbulent medium driven by thermal instability proposed previously. On the surface of the present cloud, the turbulence is likely to be driven by thermal instability following ionization shock compression and UV irradiation. Those small scale structures with line width of ~ 0.6 km/s have a relatively high CO line ratio of J=3--2 to 1--0, 1 < R(3-2/1-0) < 2. The large velocity gradient analysis implies that the 0.6 km/s width component cloudlets have an average density of 10^{3-4} cm^{-3}, which is relatively high at cloud edges, but their masses are only < 0.05 M_{sun}.Comment: 12 pages, 9 figures. To be published in the Astrophysical Journa

Influence of Lipid Heterogeneity and Phase Behavior on Phospholipase A2 Action at the Single Molecule Level

We monitored the action of phospholipase A2 (PLA2) on L- and D-dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers by mounting a Langmuir-trough on a wide-field fluorescence microscope with single molecule sensitivity. This made it possible to directly visualize the activity and diffusion behavior of single PLA2 molecules in a heterogeneous lipid environment during active hydrolysis. The experiments showed that enzyme molecules adsorbed and interacted almost exclusively with the fluid region of the DPPC monolayers. Domains of gel state L-DPPC were degraded exclusively from the gel-fluid interface where the build-up of negatively charged hydrolysis products, fatty acid salts, led to changes in the mobility of PLA2. The mobility of individual enzymes on the monolayers was characterized by single particle tracking (SPT). Diffusion coefficients of enzymes adsorbed to the fluid interface were between 3 mu m^2/s on the L-DPPC and 4.6 mu m^/s on the D-DPPC monolayers. In regions enriched with hydrolysis products the diffusion dropped to approx. 0.2 mu m^2/s. In addition, slower normal and anomalous diffusion modes were seen at the L-DPPC gel domain boundaries where hydrolysis took place. The average residence times of the enzyme in the fluid regions of the monolayer and on the product domain were between approx. 30 and 220 ms. At the gel domains it was below the experimental time resolution, i.e. enzymes were simply reflected from the gel domains back into solution.Comment: 10 pages, 10 figure

The "toothbrush-relic": evidence for a coherent linear 2-Mpc scale shock wave in a massive merging galaxy cluster?

Some merging galaxy clusters host diffuse extended radio emission, so-called radio halos and relics. Here we present observations between 147 MHz and 4.9 GHz of a new radio-selected galaxy cluster 1RXS J0603.3+4214 (z=0.225). The cluster is also detected as an extended X-ray source in the RASS. It hosts a large bright 1.9 Mpc radio relic, an elongated ~2 Mpc radio halo, and two smaller radio relics. The large radio relic has a peculiar linear morphology. For this relic we observe a clear spectral index gradient, in the direction towards the cluster center. We performed Rotation Measure (RM) Synthesis between 1.2 and 1.7 GHz. The results suggest that for the west part of the large relic some of the Faraday rotation is caused by ICM and is not only due to galactic foregrounds. We also carried out a detailed spectral analysis of this radio relic and created radio color-color diagrams. We find (i) an injection spectral index of -0.6 to -0.7, (ii) steepening spectral index and increasing spectral curvature in the post-shock region, and (iii) an overall power-law spectrum between 74 MHz and 4.9 GHz with \alpha=-1.10 \pm 0.02. Mixing of emission in the beam from regions with different spectral ages is probably the dominant factor that determines the shape of the radio spectra. Changes in the magnetic field, total electron content, or adiabatic gains/losses do not play a major role. A model in which particles are (re)accelerated in a first order Fermi process at the front of the relic provides the best match to the observed spectra. We speculate that in the post-shock region particles are re-accelerated by merger induced turbulence to form the radio halo as the relic and halo are connected. The 1RXS J0603.3+4214 merger is probably more complex than the "simple'" binary merger events that are thought to give rise to symmetric double radio relics.Comment: 22 pages, 22 figures, accepted for publication in A\&A on September 3, 201