1,229 research outputs found
3D Dune Skeleton Model as a Coupled Dynamical System of 2D Cross-Sections
To analyze theoretically the stability of the shape and the migration process
of transverse dunes and barchans, we propose a {\it skeleton model} of 3D dunes
described with coupled dynamics of 2D cross-sections. First, 2D cross-sections
of a 3D dune parallel to the wind direction are extracted as elements of a
skeleton of the 3D dune, hence, the dynamics of each and interaction between
them is considered. This model simply describes the essential dynamics of 3D
dunes as a system of coupled ordinary differential equations. Using the model
we study the stability of the shape of 3D transversal dunes and their
deformation to barchans depending on the amount of available sand in the dune
field, sand flow in parallel and perpendicular to wind direction.Comment: 6 pages, 6 figures, lette
Computationally efficient algorithms for the two-dimensional Kolmogorov-Smirnov test
Goodness-of-fit statistics measure the compatibility of random samples against some theoretical or reference probability distribution function. The classical one-dimensional Kolmogorov-Smirnov test is a non-parametric statistic for comparing two empirical distributions which defines the largest absolute difference between the two cumulative distribution functions as a measure of disagreement. Adapting this test to more than one dimension is a challenge because there are 2^d-1 independent ways of ordering a cumulative distribution function in d dimensions. We discuss Peacock's version of the Kolmogorov-Smirnov test for two-dimensional data sets which computes the differences between cumulative distribution functions in 4n^2 quadrants. We also examine Fasano and Franceschini's variation of Peacock's test, Cooke's algorithm for Peacock's test, and ROOT's version of the two-dimensional Kolmogorov-Smirnov test. We establish a lower-bound limit on the work for computing Peacock's test of
Omega(n^2.lg(n)), introducing optimal algorithms for both this and Fasano and Franceschini's test, and show that Cooke's algorithm is not a faithful implementation of Peacock's test. We also discuss and evaluate parallel algorithms for Peacock's test
Exploring the SO(32) Heterotic String
We give a complete classification of Z_N orbifold compactification of the
heterotic SO(32) string theory and show its potential for realistic model
building. The appearance of spinor representations of SO(2n) groups is analyzed
in detail. We conclude that the heterotic SO(32) string constitutes an
interesting part of the string landscape both in view of model constructions
and the question of heterotic-type I duality.Comment: 21 pages, 5 figure
Nucleotide– and Mal3-dependent changes in fission yeast microtubules suggest a structural plasticity view of dynamics
Using cryo-electron microscopy, we characterize the architecture of microtubules assembled from Schizosaccharomyces pombe tubulin, in the presence and absence of their regulatory partner Mal3. Cryo-electron tomography reveals that microtubules assembled from S. pombe tubulin have predominantly B-lattice interprotofilament contacts, with protofilaments skewed around the microtubule axis. Copolymerization with Mal3 favors 13 protofilament microtubules with reduced protofilament skew, indicating that Mal3 adjusts interprotofilament interfaces. A 4.6-Å resolution structure of microtubule-bound Mal3 shows that Mal3 makes a distinctive footprint on the S. pombe microtubule lattice and that unlike mammalian microtubules, S. pombe microtubules do not show the longitudinal lattice compaction associated with EB protein binding and GTP hydrolysis. Our results firmly support a structural plasticity view of microtubule dynamics in which microtubule lattice conformation is sensitive to a variety of effectors and differently so for different tubulins
Majorana neutrino versus Dirac neutrino in through radiative corrections
Radiative corrections to from Majorana neutrinos are studied in the context of the
see-saw mechanism. Focusing on the effects of the fourth generation neutrinos,
we calculate W-pair form factors, the differential cross sections and the
forward-backward asymmetries for the polarized electrons at one-loop level. The
behaviour of the form factors at the threshold of Majorana particle pair
productions is found to differ from that of Dirac particle pair productions. In
the cross section for unpolarized electrons, the radiative corrections,
depending on the mass parameters of the see-saw mechanism, are found to be
at the energy range of the LEP200 and the next generation linear
colliders.Comment: 10 pages, Latex, 4 figures(no included, available on request
Spotting the diffusion of New Psychoactive Substances over the Internet
Online availability and diffusion of New Psychoactive Substances (NPS)
represent an emerging threat to healthcare systems. In this work, we analyse
drugs forums, online shops, and Twitter. By mining the data from these sources,
it is possible to understand the dynamics of drugs diffusion and their
endorsement, as well as timely detecting new substances. We propose a set of
visual analytics tools to support analysts in tackling NPS spreading and
provide a better insight about drugs market and analysis
Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity
Magnetic fields generated by human and animal organs, such as the heart,
brain and nervous system carry information useful for biological and medical
purposes. These magnetic fields are most commonly detected using
cryogenically-cooled superconducting magnetometers. Here we present the frst
detection of action potentials from an animal nerve using an optical atomic
magnetometer. Using an optimal design we are able to achieve the sensitivity
dominated by the quantum shot noise of light and quantum projection noise of
atomic spins. Such sensitivity allows us to measure the nerve impulse with a
miniature room-temperature sensor which is a critical advantage for biomedical
applications. Positioning the sensor at a distance of a few millimeters from
the nerve, corresponding to the distance between the skin and nerves in
biological studies, we detect the magnetic field generated by an action
potential of a frog sciatic nerve. From the magnetic field measurements we
determine the activity of the nerve and the temporal shape of the nerve
impulse. This work opens new ways towards implementing optical magnetometers as
practical devices for medical diagnostics.Comment: Main text with figures, and methods and supplementary informatio
Measurement of the electron transmission rate of the gating foil for the TPC of the ILC experiment
We have developed a gating foil for the time projection chamber envisaged as
a central tracker for the international linear collider experiment. It has a
structure similar to the Gas Electron Multiplier (GEM) with a higher optical
aperture ratio and functions as an ion gate without gas amplification. The
transmission rate for electrons was measured in a counting mode for a wide
range of the voltages applied across the foil using an Fe source and a
laser in the absence of a magnetic field. The blocking power of the foil
against positive ions was estimated from the electron transmissions.Comment: 25 pages containing 14 figures and 1 tabl
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