49,552 research outputs found
Multifractal analysis of nonhyperbolic coupled map lattices: Application to genomic sequences
Symbolic sequences generated by coupled map lattices (CMLs) can be used to
model the chaotic-like structure of genomic sequences. In this study it is
shown that diffusively coupled Chebyshev maps of order 4 (corresponding to a
shift of 4 symbols) very closely reproduce the multifractal spectrum of
human genomic sequences for coupling constant if .
The presence of rare configurations causes deviations for , which
disappear if the rare event statistics of the CML is modified. Such rare
configurations are known to play specific functional roles in genomic sequences
serving as promoters or regulatory elements.Comment: 7 pages, 6 picture
Red-giant stars in eccentric binaries
The unparalleled photometric data obtained by NASA’s Kepler Space Telescope has led to improved understanding of red-giant stars and binary stars. We discuss the characterization of known eccentric system, containing a solar-like oscillating red-giant primary component. We also report several new binary systems that are candidates for hosting an oscillating companion. A powerful approach to study binary stars is to combine asteroseimic techniques with light curve fitting. Seismology allows us to deduce the properties of red giants. In addition, by modeling the ellipsoidal modulations we can constrain the parameters of the binary system. An valuable independent source are ground-bases, high-resolution spectrographs
Development of hazard analysis and critical control points (HACCP) procedures to control organic chemical hazards in the agricultural production of raw food commodities
Hazard Analysis by Critical Control Points (HACCP) is a systematic approach to the identification, assessment and control of hazards in the food chain. Effective HACCP requires the consideration of all possible hazards, i.e., chemical, microbiological and physical. However, current procedures focus primarily upon microbiological and physical hazards, and, to date, chemical aspects of HACCP have received relatively little attention. Consequently, this report discusses the application of HACCP to organic chemical contaminants and the particular problems that are likely to encounter within the agricultural sector. It also presents generic templates for the development of organic chemical contaminant HACCP procedures for selected raw food commodities, i.e., cereal crops, raw meats and milk
Generation of Magnetic Field in the Pre-recombination Era
We study the possibility of generating magnetic fields during the evolution
of electron, proton, and photon plasma in the pre-recombination era. We show
that a small magnetic field can be generated in the second order of
perturbation theory for scalar modes with adiabatic initial conditions. The
amplitude of the field is \la 10^{-30} \rm G at the present epoch for scales
from sub-kpc to \ga 100 \rm Mpc.Comment: 8 page
Approaching Visual Search in Photo-Realistic Scenes
Visual search is extended from the domain of polygonal figures presented on a uniform background to scenes in which search is for a photo-realistic object in a dense, naturalistic background. Scene generation for these displays relies on a powerful solid modeling program to define the three dimensional forms, surface properties, relative positions, and illumination of the objects and a rendering program to produce an image. Search in the presented experiments is for a rock with specific properties among other, similar rocks, although the method described can be generalized to other situations. Using this technique we explore the effects of illumination and shadows in aiding search for a rock in front of and closer to the viewer than other rocks in the scene. For these scenes, shadows of two different contrast levels can significantly deet·ease reaction times for displays in which target rocks are similar to distractor rocks. However, when the target rock is itself easily distinguishable from dis tractors on the basis of form, the presence or absence of shadows has no discernible effect. To relate our findings to those for earlier polygonal displays, we simplified the non-shadow displays so that only boundary information remained. For these simpler displays, search slopes (the reaction time as a function of the number of distractors) were significantly faster, indicating that the more complex photo-realistic objects require more time to process for visual search. In contrast with several previous experiments involving polygonal figures, we found no evidence for an effect of illumination direction on search times
Can spicules be detected at disc centre in broad-band Ca II H filter imaging data ?
We estimate the formation height range contributing to broad-band and
narrow-band filter imaging data in Ca II H to investigate whether spicules can
be detected in such observations at the centre of the solar disc. We apply
spectral filters of FWHMs from 0.03 nm to 1 nm to observed Ca line profiles to
simulate Ca imaging data. We estimate the relative intensity contributions of
off-limb and on-disc structures. We compare the synthetic Ca filter imaging
data with intensity maps of Ca spectra at different wavelengths and temperature
maps at different optical depths. We determine the intensity response function
for the wavelengths covered by the filters of different FWHM.
The intensity emitted off the solar limb is about 5% of the intensity at disc
centre. For a 0.3 nm-wide Ca II H filter, up to about 1/3 of the off-limb
intensity comes from emission in Hepsilon. On the disc, only about 15% of the
intensity transmitted through a broad-band filter comes from the line-core
region. No traces of elongated fibrillar structures are visible in imaging data
at disc centre, opposite to the line-core images of the Ca spectra. The
response function for a 0.3 nm-wide filter peaks at about 200 km. Relative
contributions from atmospheric layers above 800 km are about 10%. The inversion
results suggest that the slightly enhanced emission around the photospheric
magnetic network in broad-band Ca imaging data is caused by a thermal canopy at
a height of about 600 km. Broad-band Ca II H imaging data do not trace upper
chromospheric structures such as spicules in observations at the solar disc
because of the too small relative contribution of the line core to the total
wavelength-integrated filter intensity.Comment: 10 pages, 11 figures, accepted for publication in A&
Accounting for Seismic Risk in Financial Analysis of Property Investment
A methodology is presented for making property investment decisions using loss
analysis and the principles of decision analysis. It proposes that the investor choose among
competing investment alternatives on the basis of the certainty equivalent of their net asset value
which depends on the uncertain discounted future net income, uncertain discounted future
earthquake losses, initial equity and the investor’s risk tolerance. The earthquake losses are
modelled using a seismic vulnerability function, the site seismic hazard function, and an
assumption that strong shaking at a site follows a Poisson process. A building-specific
vulnerability approach, called assembly-based vulnerability, or ABV, is used. ABV involves a
simulation approach that includes dynamic structural analyses and damage analyses using
fragility functions and probability distributions on unit repair costs and downtimes for all
vulnerable structural and nonstructural components in a building. The methodology is
demonstrated using some results from a seven-storey reinforced-concrete hotel in Los Angeles
Beneficial and Harmful Agile Practices for Product Quality
There is the widespread belief that Agile neglects the product quality. This
lack of understanding how Agile processes assure the quality of the product
prevents especially companies from regulated domains from an adoption of Agile.
This work aims to identify which Agile Practices contribute towards product
quality. Hence, data from a survey study is analyzed to identify Ag-ile
Practices which are beneficial or harmful for the quality of the product. From
49 practices that were used in the survey so far, 36 were perceived to have a
positive impact on product quality, while four practices were rated as being
harmful. The results enrich understanding of how product quality can be
achieved in Agile, and support selection of practices to improve quality
Spectroscopy at the solar limb: II. Are spicules heated to coronal temperatures ?
Spicules of the so-called type II were suggested to be relevant for coronal
heating because of their ubiquity on the solar surface and their eventual
extension into the corona. We investigate whether solar spicules are heated to
transition-region or coronal temperatures and reach coronal heights (>6 Mm)
using multi-wavelength observations of limb spicules in different chromospheric
spectral lines (Ca II H, Hepsilon, Halpha, Ca II IR at 854.2 nm, He I at 1083
nm). We determine the line width of individual spicules and throughout the
field of view and estimate the maximal height that different types of off-limb
features reach. We derive estimates of the kinetic temperature and the
non-thermal velocity from the line width of spectral lines from different
chemical elements. We find that most regular spicules reach a maximal height of
about 6 Mm above the solar limb. The majority of features found at larger
heights are irregularly shaped with a significantly larger lateral extension
than spicules. Both individual and average line profiles in all spectral lines
show a decrease in their line width with height above the limb with very few
exceptions. Both the kinetic temperature and the non-thermal velocity decrease
with height above the limb. We find no indications that the spicules in our
data reach coronal heights or transition-region or coronal temperatures.Comment: Accepted for publication in Solar Physics, 52 pages, 32 figure
The polarization signature of photospheric magnetic fields in 3D MHD simulations and observations at disk center
Before using 3D MHD simulations of the solar photosphere in the determination
of elemental abundances, one has to ensure that the correct amount of magnetic
flux is present in the simulations. The presence of magnetic flux modifies the
thermal structure of the solar photosphere, which affects abundance
determinations and the solar spectral irradiance. We compare the polarization
signals in disk-center observations of the solar photosphere in quiet-Sun
regions with those in Stokes spectra computed on the basis of 3D MHD
simulations having average magnetic flux densities of about 20, 56, 112 and 224
G. This approach allows us to find the simulation run that best matches the
observations. The observations were taken with the Hinode SP, TIP, POLIS and
the GFPI, respectively. We determine characteristic quantities of full Stokes
profiles in a few photospheric spectral lines in the visible (630 nm) and
near-infrared (1083 and 1565 nm). We find that the appearance of abnormal
granulation in intensity maps of degraded simulations can be traced back to an
initially regular granulation pattern with numerous bright points in the
intergranular lanes before the spatial degradation. The linear polarization
signals in the simulations are almost exclusively related to canopies of strong
magnetic flux concentrations and not to transient events of magnetic flux
emergence. We find that the average vertical magnetic flux density in the
simulation should be less than 50 G to reproduce the observed polarization
signals in the quiet Sun internetwork. A value of about 35 G gives the best
match across the SP, TIP, POLIS and GFPI observations.Comment: 12 pages, 11 figures; accepted for publication in Ap
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