15,397 research outputs found
J/psi suppression at SPS and RHIC in the comovers approach
The NA50 collaboration data on the suppression are compared with the
results obtained in a comovers approach based on the Dual Parton Model (DPM).
Predictions for the suppression versus the charged multiplicity -
measured in the rapidity region of the dimuon trigger - are given for SPS and
RHIC energies.Comment: 4 pages, contribution to QM200
Scale insects (Hemiptera: Coccoidea) of ornamental plants from Sao Carlos, Sao Paulo, Brazil
A list of 35 scale insects collected from 72 ornamental plant species in Sao Carlos, Sao Paulo, Brazil is provided. Regarding host specificity, 30 scale insects were polyphagous, 4 oligophagous, and 1 monophagous. A total of 102 coccoid/plant associations are recorded, 29 of which are new host records for the species; 60 are new host records for the species in Brazil. Pulvinaria urbicola Cockerell, 1893 (Coccidae), Phenacoccus similis Granara de Willink, 1983 (Pseudococcidae), and Orthezia molinarii (Morrison, 1952) (Ortheziidae) are recorded for the first time in Brazil. In addition, we describe the injury caused by scale insects on ornamental plants
Towards the undestanding of radial velocity pulsation in roAp stars
High-resolution spectroscopic time series of rapidly oscillating Ap stars
show evidence for a co-existence of standing and running waves in their
atmospheric layers. With the purpose of understanding these observations we
have carried out a theoretical analysis of the pulsations in the outermost
layers of these stars, starting from the simplest possible model that still
retains all important physical ingredients. In our analysis we considered an
isothermal atmosphere in a plane-parallel approximation. Moreover we assumed
that in the region considered the magnetic pressure is much larger than the gas
pressure and, consequently, that the magnetoacoustic wave has decoupled into
its acoustic and magnetic components. Using the analytical solutions for the
velocity components appropriate to this model we estimate the velocity
component parallel to the line of sight averaged over the visible stellar disk.
Fitting the latter to a function of the form Acos(t+phase), with
the dimensionless oscillation frequency and t the dimensionless time,
we derive the amplitude A and the phase for our model as function of height in
the atmosphere.Comment: 5 pages and 5 figure
NIR spectroscopy of the Sun and HD20010 - Compiling a new linelist in the NIR
Context: Effective temperature, surface gravity, and metallicity are basic
spectroscopic stellar parameters necessary to characterize a star or a
planetary system. Reliable atmospheric parameters for FGK stars have been
obtained mostly from methods that relay on high resolution and high
signal-to-noise optical spectroscopy. The advent of a new generation of high
resolution near-IR spectrographs opens the possibility of using classic
spectroscopic methods with high resolution and high signal-to-noise in the NIR
spectral window. Aims: We aim to compile a new iron line list in the NIR from a
solar spectrum to derive precise stellar atmospheric parameters, comparable to
the ones already obtained from high resolution optical spectra. The spectral
range covers 10 000 {\AA} to 25 000 {\AA}, which is equivalent to the Y, J, H,
and K bands. Methods: Our spectroscopic analysis is based on the iron
excitation and ionization balance done in LTE. We use a high resolution and
high signal-to-noise ratio spectrum of the Sun from the Kitt Peak telescope as
a starting point to compile the iron line list. The oscillator strengths (log
gf) of the iron lines were calibrated for the Sun. The abundance analysis was
done using the MOOG code after measuring equivalent widths of 357 solar iron
lines. Results: We successfully derived stellar atmospheric parameters for the
Sun. Furthermore, we analysed HD20010, a F8IV star, from which we derived
stellar atmospheric parameters using the same line list as for the Sun. The
spectrum was obtained from the CRIRES- POP database. The results are compatible
with the ones found in the literature, confirming the reliability of our line
list. However, due to the quality of the data we obtain large errors.Comment: 9 pages and 9 figure
Chaos and Synchronized Chaos in an Earthquake Model
We show that chaos is present in the symmetric two-block Burridge-Knopoff
model for earthquakes. This is in contrast with previous numerical studies, but
in agreement with experimental results. In this system, we have found a rich
dynamical behavior with an unusual route to chaos. In the three-block system,
we see the appearance of synchronized chaos, showing that this concept can have
potential applications in the field of seismology.Comment: To appear in Physical Review Letters (13 pages, 6 figures
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