8,373 research outputs found
The Detection of a 3.5-h Period in the Classical Nova Velorum 1999 (V382 Vel) and the Long Term Behavior of the Nova Light Curve
We present CCD photometry, light curve and time series analysis of the
classical nova V382 Vel (N Vel 1999). The source was observed for 2 nights in
2000, 21 nights in 2001 and 7 nights in 2002 using clear filters. We report the
detection of a distinct period in the light curve of the nova P=0.146126(18) d
(3.5 h). The period is evident in all data sets, and we interpret it as the
binary period of the system. We also measured an increase in the amplitude
modulation of the optical light (in magnitude) by more than 55% from 2000 to
2001 and about 64% from 2001 to 2002. The pulse profiles in 2001 show
deviations from a pure sinusoidal shape which progressively become more
sinusoidal by 2002. The main cause of the variations in 2001 and 2002 can be
explained with the occultation of the accretion disk by the secondary star. We
interpret the observed deviations from a pure sinusoidal shape as additional
flux resulting from the aspect variations of the irradiated face of the
secondary star.Comment: 16 pages and 4 figures, accepted as it stands to be published in the
Astronomical Journal (AJ
Fully broadband vAPP coronagraphs enabling polarimetric high contrast imaging
We present designs for fully achromatic vector Apodizing Phase Plate (vAPP)
coronagraphs, that implement low polarization leakage solutions and achromatic
beam-splitting, enabling observations in broadband filters. The vAPP is a pupil
plane optic, inducing the phase through the inherently achromatic geometric
phase. We discuss various implementations of the broadband vAPP and set
requirements on all the components of the broadband vAPP coronagraph to ensure
that the leakage terms do not limit a raw contrast of 1E-5. Furthermore, we
discuss superachromatic QWPs based of liquid crystals or quartz/MgF2
combinations, and several polarizer choices. As the implementation of the
(broadband) vAPP coronagraph is fully based on polarization techniques, it can
easily be extended to furnish polarimetry by adding another QWP before the
coronagraph optic, which further enhances the contrast between the star and a
polarized companion in reflected light. We outline several polarimetric vAPP
system designs that could be easily implemented in existing instruments, e.g.
SPHERE and SCExAO.Comment: 11 pages, 5 figures, presented at SPIE Astronomical Telescopes and
Instrumentation 201
Lagrangian dynamics and statistical geometric structure of turbulence
The local statistical and geometric structure of three-dimensional turbulent
flow can be described by properties of the velocity gradient tensor. A
stochastic model is developed for the Lagrangian time evolution of this tensor,
in which the exact nonlinear self-stretching term accounts for the development
of well-known non-Gaussian statistics and geometric alignment trends. The
non-local pressure and viscous effects are accounted for by a closure that
models the material deformation history of fluid elements. The resulting
stochastic system reproduces many statistical and geometric trends observed in
numerical and experimental 3D turbulent flows, including anomalous relative
scaling.Comment: 5 pages, 5 figures, final version, publishe
QCD Corrections to Production of Higgs Pseudoscalars
Models of electroweak symmetry breaking with more than a single doublet of
Higgs scalars contain a neutral pseudoscalar boson. The production of such a
pseudoscalar in hadron collisions proceeds primarily via gluon fusion through a
top-quark loop (except for those models in which the pseudoscalar coupling to
bottom quarks is strongly enhanced). We compute the QCD corrections to this
process in the heavy-quark limit, using an effective Lagrangian derived from
the axial anomaly.Comment: 9 pages, (BNL number added, 1 typo corrected, PHYZZX format, 4
figures not included, available on request), BNL-4906
Biphasic positive airway pressure ventilation (PeV+) in children
BACKGROUND: Biphasic positive airway pressure (BIPAP) (also known as PeV+) is a mode of ventilation with cycling variations between two continuous positive airway pressure levels. In adults this mode of ventilation is effective and is being accepted with a decrease in need for sedatives because of the ability to breathe spontaneously during the entire breathing cycle. We studied the use of BIPAP in infants and children. METHODS: We randomized 18 patients with respiratory failure for ventilation with either BIPAP (n = 11) or assisted spontaneous breathing (ASB) (n = 7) on Evita 4. Lorazepam and, if necessary, morphine were used as sedatives and adjusted in accordance with the Comfort scale. We compared number of randomized mode failure, duration and complications of ventilation and number and dosages of sedatives administered. RESULTS: No differences in patient characteristics, ventilatory parameters, complications of ventilation or use of sedatives were noted. Ten out of eleven patients that we intended to ventilate with BIPAP were successfully ventilated with BIPAP. Four out of seven patients that we intended to ventilate with ASB could not be ventilated adequately with ASB but were successfully crossed over to BIPAP without the need for further sedatives. CONCLUSIONS: BIPAP is an effective, safe and easy to use mode of ventilation in infants and children
Testing Ocean Tide Models in the Nordic Seas with Tidal Gravity Observations
Examines the accuracy of ocean tide models in the Nordic seas. Tidal gravity observations; Computation of ocean tide loading; Phase lag of the ocean tide models
Psychopathology symptoms in a sample of female cosmetic surgery patients
Objective: During the past decades, cosmetic surgery has become increasingly popular. People with certain psychopathology disorders, for example, body dysmorphic disorder (BDD), are dissatisfied with their physical appearance, and a significant number try to receive cosmetic medical treatment for their complaints. It seems relatively easy for them to receive this type of surgery, despite the fact that it has no or even adverse effects on the symptoms. The present study aimed to investigate the psychological condition and especially the presence of psychopathological symptoms such as BDD in cosmetic surgery patients. Methods: Questionnaires about body image dissatisfaction, symptoms of BDD and psychopathology in general and satisfaction about surgery were sent to patients who had been treated in a large cosmetic surgery clinic. Results: Of the patients who replied, 86% were pleased with the outcome of the cosmetic procedure. Further, 21-59% of these former patients scored higher on questionnaires of body image dissatisfaction and psychopathological symptoms than a norm group from the general population. When differentiating the group on the basis of BDD symptomatology, it appeared that the high BDD symptomatic group displayed significantly worse outcome on all measurements. That is, high BDD symptomatic patients were more dissatisfied about the result of surgery, exhibited higher levels of psychopathology, and had lower self-esteem than the low symptomatic BDD patients. Conclusion: These findings clearly suggest that the evaluation of the psychological condition and motivation of the candidate patient might be a valuable addition to the standard procedure in cosmetic medical treatment settings
Polarization-dependent beam shifts upon metallic reflection in high-contrast imagers and telescopes
(Abridged) Context. To directly image rocky exoplanets in reflected
(polarized) light, future space- and ground-based high-contrast imagers and
telescopes aim to reach extreme contrasts at close separations from the star.
However, the achievable contrast will be limited by reflection-induced
polarization aberrations. While polarization aberrations can be modeled
numerically, such computations provide little insight into the full range of
effects, their origin and characteristics, and possible ways to mitigate them.
Aims. We aim to understand polarization aberrations produced by reflection off
flat metallic mirrors at the fundamental level. Methods. We used polarization
ray tracing to numerically compute polarization aberrations and interpret the
results in terms of the polarization-dependent spatial and angular
Goos-H\"anchen and Imbert-Federov shifts of the beam of light as described with
closed-form mathematical expressions in the physics literature. Results. We
find that all four beam shifts are fully reproduced by polarization ray tracing
and study the origin, characteristics, sizes, and directions of the shifts. Of
the four beam shifts, only the spatial Goos-H\"anchen and Imbert-Federov shifts
are relevant for high-contrast imagers and telescopes because these shifts are
visible in the focal plane and create a polarization structure in the PSF that
reduces the performance of coronagraphs and the polarimetric speckle
suppression close to the star. Conclusions. The beam shifts in an optical
system can be mitigated by keeping the f-numbers large and angles of incidence
small. Most importantly, mirror coatings should not be optimized for maximum
reflectivity, but should be designed to have a retardance close to 180{\deg}.
The insights from our study can be applied to improve the performance of
current and future high-contrast imagers, especially those in space and on the
ELTs.Comment: 19 pages, 13 figures, 1 table, accepted for publication in Astronomy
& Astrophysics, forthcoming articl
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