20,957 research outputs found
Numerical studies of planar closed random walks
Lattice numerical simulations for planar closed random walks and their
winding sectors are presented. The frontiers of the random walks and of their
winding sectors have a Hausdorff dimension . However, when properly
defined by taking into account the inner 0-winding sectors, the frontiers of
the random walks have a Hausdorff dimension .Comment: 15 pages, 15 figure
Circular 90
The growth regulators chlormequat (Cycocel), paclobutrazol (Bonzi), daminozide (B-Nine) and
Bayleton 25WP (triadimefon) were studied for their ability to control plant height in seed propagated tuberous begonia (‘Nonstop’ begonias). Bayleton is a fungicide used for powdery mildew control that also has growth regulator effects. Two ml growth regulator solution was evenly sprayed on each plant two weeks after transplanting. Cycocel (500 parts per million [ppm], 1 mg active ingredient [a.i.] per plant) resulted in 23% shorter plants than the control plants 15 weeks after
transplant. Bonzi (5 ppm, 0.01 mg a.i. per plant) treated begonias were 65% and Bayleton (150 mg•liter-1, 0.3 mg
per plant) treated plants 43% shorter than the control plants. The number of flowers and shoots was severely
reduced on plants treated with Bonzi or Bayleton. BNine was ineffective at the rate of 3000 ppm (6 mg a.i.
per plant) for controlling plant height of seed propagated tuberous begonia
Element Abundance Determination in Hot Evolved Stars
The hydrogen-deficiency in extremely hot post-AGB stars of spectral class
PG1159 is probably caused by a (very) late helium-shell flash or a AGB final
thermal pulse that consumes the hydrogen envelope, exposing the usually-hidden
intershell region. Thus, the photospheric element abundances of these stars
allow us to draw conclusions about details of nuclear burning and mixing
processes in the precursor AGB stars. We compare predicted element abundances
to those determined by quantitative spectral analyses performed with advanced
non-LTE model atmospheres. A good qualitative and quantitative agreement is
found for many species (He, C, N, O, Ne, F, Si, Ar) but discrepancies for
others (P, S, Fe) point at shortcomings in stellar evolution models for AGB
stars. Almost all of the chemical trace elements in these hot stars can only be
identified in the UV spectral range. The Far Ultraviolet Spectroscopic Explorer
and the Hubble Space Telescope played a crucial role for this research.Comment: To appear in: Recent Advances in Spectroscopy: Theoretical,
Astrophysical, and Experimental Perspectives, Proceedings, Jan 28 - 31, 2009,
Kodaikanal, India (Springer
Improved Limit on theta_{13} and Implications for Neutrino Masses in Neutrino-less Double Beta Decay and Cosmology
We analyze the impact of a measurement, or of an improved bound, on
theta_{13} for the determination of the effective neutrino mass in
neutrino-less double beta decay and cosmology. In particular, we discuss how an
improved limit on (or a specific value of) theta_{13} can influence the
determination of the neutrino mass spectrum via neutrino-less double beta
decay. We also discuss the interplay with improved cosmological neutrino mass
searches.Comment: 22 pages, 5 figures. Minor corrections, matches version in PR
The NASA Spitzer Space Telescope
The National Aeronautics and Space Administration's Spitzer Space Telescope (formerly the Space Infrared Telescope Facility) is the fourth and final facility in the Great Observatories Program, joining Hubble Space Telescope (1990), the Compton Gamma-Ray Observatory (1991–2000), and the Chandra X-Ray Observatory (1999). Spitzer, with a sensitivity that is almost three orders of magnitude greater than that of any previous ground-based and space-based infrared observatory, is expected to revolutionize our understanding of the creation of the universe, the formation and evolution of primitive galaxies, the origin of stars and planets, and the chemical evolution of the universe. This review presents a brief overview of the scientific objectives and history of infrared astronomy. We discuss Spitzer's expected role in infrared astronomy for the new millennium. We describe pertinent details of the design, construction, launch, in-orbit checkout, and operations of the observatory and summarize some science highlights from the first two and a half years of Spitzer operations. More information about Spitzer can be found at http://spitzer.caltech.edu/
Evidence for shape coexistence in Mo
A angular correlation experiment has been performed to
investigate the low-energy states of the nucleus Mo. The new data,
including spin assignments, multipole mixing ratios and lifetimes reveal
evidence for shape coexistence and mixing in Mo, arising from a proton
intruder configuration. This result is reproduced by a theoretical calculation
within the proton-neutron interacting boson model with configuration mixing,
based on microscopic energy density functional theory. The microscopic
calculation indicates the importance of the proton particle-hole excitation
across the Z=40 sub-shell closure and the subsequent mixing between spherical
vibrational and the -soft equilibrium shapes in Mo.Comment: 6 pages, 5 figures, 3 tables; published in Phys. Rev.
Evidence for Hydrodynamic Evolution in Proton-Proton Scattering at LHC Energies
In scattering at LHC energies, large numbers of elementary scatterings
will contribute significantly, and the corresponding high multiplicity events
will be of particular interest. Elementary scatterings are parton ladders,
identified with color flux-tubes. In high multiplicity events, many of these
flux tubes are produced in the same space region, creating high energy
densities. We argue that there are good reasons to employ the successful
procedure used for heavy ion collisions: matter is assumed to thermalizes
quickly, such that the energy from the flux-tubes can be taken as initial
condition for a hydrodynamic expansion. This scenario gets spectacular support
from very recent results on Bose-Einstein correlations in scattering at
900 GeV at LHC.Comment: 11 pages, 20 figure
Transforming fixed-length self-avoiding walks into radial SLE_8/3
We conjecture a relationship between the scaling limit of the fixed-length
ensemble of self-avoiding walks in the upper half plane and radial SLE with
kappa=8/3 in this half plane from 0 to i. The relationship is that if we take a
curve from the fixed-length scaling limit of the SAW, weight it by a suitable
power of the distance to the endpoint of the curve and then apply the conformal
map of the half plane that takes the endpoint to i, then we get the same
probability measure on curves as radial SLE. In addition to a non-rigorous
derivation of this conjecture, we support it with Monte Carlo simulations of
the SAW. Using the conjectured relationship between the SAW and radial SLE, our
simulations give estimates for both the interior and boundary scaling
exponents. The values we obtain are within a few hundredths of a percent of the
conjectured values
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