43,831 research outputs found
Effective theories and constraints on new phyhsics
Anomalous moments of the top quark arises from one loop corrections to the
vertices and . We study these anomalous couplings
in different frameworks: effective theories, Standard Model and 2HDM. We use
available experimental results in order to get bounds on these anomalous
couplings.Comment: 8 pages, 2 figures, talk presented by R. Martinez at the X Mexican
School of Particles and Fields, Playa del Carmen, Mexico, 200
The far-IR spectrum of Sagittarius B2 region: Extended molecular absorption, photodissociation and photoionization
We present large scale 9'x 27'(25 pc x 70 pc) far-IR observations around Sgr
B2 using the Long-wavelength spectrometer (LWS) on board the Infrared Space
Observatory (ISO). The spectra are dominated by the strong continuum emission
of dust, the widespread molecular absorption of light hydrides (OH, CH and H2O)
and the fine structure lines of [NII], [NIII], [OIII], [CII] and [OI]. The
molecular richness in the outer layers of Sgr B2 is probed by the ISO-LWS
Fabry-Perot (35 km s^-1) detections towards Sgr B2(M), where more that 70 lines
from 15 molecular and atomic species are observed at high signal to noise
ratio.Comment: 46 pages, 10 figures, 5 tables, accepted in ApJ part I. (Figs. 1, 2,
3, 9 and 10 have been bitmapped to low resolution
High Angular Resolution Observations of the Collimated Jet Source Associated with a Massive Protostar in IRAS 16547-4247
A triple radio source recently detected in association with the luminous
infrared source IRAS 16547-4247 has been studied with high angular resolution
and high sensitivity with the Very Large Array at 3.6 and 2 cm. Our
observations confirm the interpretation that the central object is a thermal
radio jet, while the two outer lobes are most probably heavily obscured HH
objects. The thermal radio jet is resolved angularly for the first time and
found to align closely with the outer lobes. The opening angle of the thermal
jet is estimated to be , confirming that collimated outflows can
also be present in massive protostars. The proper motions of the outer lobes
should be measurable over timescales of a few years. Several fainter sources
detected in the region are most probably associated with other stars in a young
cluster.Comment: 9 pages, 2 figure
The properties of the stellar populations in ULIRGs I: sample, data and spectral synthesis modelling
We present deep long-slit optical spectra for a sample of 36 Ultraluminous
Infrared Galaxies (ULIRGs), taken with the William Herschel Telescope (WHT) on
La Palma with the aim of investigating the star formation histories and testing
evolutionary scenarios for such objects. Here we present the sample, the
analysis techniques and a general overview of the properties of the stellar
populations. Spectral synthesis modelling has been used in order to estimate
the ages of the stellar populations found in the diffuse light sampled by the
spectra in both the nuclear and extended regions of the target galaxies. We
find that adequate fits can be obtained using combinations of young stellar
populations (YSPs,t_YSP<=2 Gyr), with ages divided into two groups: very young
stellar populations (VYSPs, t_VYSP <=100 Myr) and intermediate-young stellar
populations (IYSPs, 0.1 < t_IYSP <= 2 Gyr). Our results show that YSPs are
present at all locations of the galaxies covered by our slit positions, with
the exception of the northern nuclear region of the ULIRG IRAS 23327+2913.
Furthermore, VYSPs are presents in at least 85% of the 133 extraction apertures
used for this study. Old stellar populations (OSPs, t_{OSP} > 2 Gyr) do not
make a major contribution to the optical light in the majority of the apertures
extracted. In fact they are essential for fitting the spectra in only 5% (7) of
the extracted apertures. The estimated total masses for the YSPs (VYSPs+IYSPs)
are in the range 0.18 x 10^{10} <= M_YSP <= 50 x 10^{10} Msun. We have also
estimated the bolometric luminosities associated with the stellar populations
detected at optical wavelengths, finding that they fall in the range 0.07 x
10^{12} < L_bol < 2.2 x 10^{12} Lsun. In addition, we find that reddening is
significant at all locations in the galaxies.Comment: accepted for publication in MNRA
Controlled nucleation of topological defects in the stripe domain patterns of Lateral multilayers with Perpendicular Magnetic Anisotropy: competition between magnetostatic, exchange and misfit interactions
Magnetic lateral multilayers have been fabricated on weak perpendicular
magnetic anisotropy amorphous Nd-Co films in order to perform a systematic
study on the conditions for controlled nucleation of topological defects within
their magnetic stripe domain pattern. A lateral thickness modulation of period
is defined on the nanostructured samples that, in turn, induces a lateral
modulation of both magnetic stripe domain periods and average
in-plane magnetization component . Depending on lateral multilayer
period and in-plane applied field, thin and thick regions switch independently
during in-plane magnetization reversal and domain walls are created within the
in-plane magnetization configuration coupled to variable angle grain boundaries
and disclinations within the magnetic stripe domain patterns. This process is
mainly driven by the competition between rotatable anisotropy (that couples the
magnetic stripe pattern to in-plane magnetization) and in-plane shape
anisotropy induced by the periodic thickness modulation. However, as the
structural period becomes comparable to magnetic stripe period ,
the nucleation of topological defects at the interfaces between thin and thick
regions is hindered by a size effect and stripe domains in the different
thickness regions become strongly coupled.Comment: 10 pages, 7 figures, submitted to Physical Review
Integrated Flywheel Technology, 1983
Topics of discussion included: technology assessment of the integrated flywheel systems, potential of system concepts, identification of critical areas needing development and, to scope and define an appropriate program for coordinated activity
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