8,537 research outputs found
Ellipsoidal primary of the RS CVn binary zeta And: Investigation using high-resolution spectroscopy and optical interferometry
We have obtained high-resolution spectroscopy, optical interferometry, and
long-term broad band photometry of the ellipsoidal primary of the RS CVn-type
binary system zeta And. Based on the optical interferometry the apparent limb
darkened diameter of zeta And is 2.55 +/- 0.09 mas using a uniform disk fit.
The Hipparcos distance and the limb-darkened diameter obtained with a uniform
disk fit give stellar radius of 15.9 +/- 0.8 Rsolar, and combined with
bolometric luminosity, it implies an effective temperature of 4665 +/- 140 K.
The temperature maps obtained from high resolution spectra using Doppler
imaging show a strong belt of equatorial spots and hints of a cool polar cap.
The equatorial spots show a concentration around the phase 0.75. This spot
configuration is reminiscent of the one seen in the earlier published
temperature maps of zeta And. Investigation of the Halpha line reveals both
prominences and cool clouds in the chromosphere. Long-term photometry spanning
12 years shows hints of a spot activity cycle, which is also implied by the
Doppler images, but the cycle length cannot be reliably determined from the
current data.Comment: 9 pages, 9 figures, accepted for A&
Determination of pesticide multi-residues in green tea using a modified QuEChERS extraction and liquid chromatography tandem mass spectrometry technique
A modified QuEChERS method was developed and validated for determination of pesticide multi-residues in green tea by liquid chromatography tandem mass spectrometry. Lead acetate was first time used together with primary secondary amine and graphite carbon black to eliminate tannin, caffeine, and other pigments in tea and thus reduced the matrix effects. The method was compared to the original QuEChERS method as well as A.O.A.C. QuEChERS method. For accurate quantification, the matrix matched calibration technique was used. The method showed good performance in the concentration range from 0.01 to 1 mg kg–1. All pesticides could be quantified at and lower than 0.01 mg kg–1. Recoveries were from 70 to 120% and repeatabilities were <15% RSD depending on the compounds
On the transverse mode of an atom laser
The transverse mode of an atom laser beam that is outcoupled from a
Bose-Einstein condensate is investigated and is found to be strongly determined
by the mean--field interaction of the laser beam with the condensate. Since for
repulsive interactions the geometry of the coupling scheme resembles an
interferometer in momentum space, the beam is found show filamentation.
Observation of this effect would prove the transverse coherence of an atom
laser beam.Comment: 4 pages, 4 figure
Generation of spatial antibunching with free propagating twin beams
We propose and implement a novel method to produce a spatial anti-bunched
field with free propagating twin beams from spontaneous parametric
down-conversion. The method consists in changing the spatial propagation by
manipulating the transverse degrees of freedom through reflections of one of
the twin beams. Our method use reflective elements eliminating losses from
absorption by the objects inserted in the beams.Comment: Submitted for publication in Phys. Rev.
The SPHERE data center: a reference for high contrast imaging processing
The objective of the SPHERE Data Center is to optimize the scientific return
of SPHERE at the VLT, by providing optimized reduction procedures, services to
users and publicly available reduced data. This paper describes our motivation,
the implementation of the service (partners, infrastructure and developments),
services, description of the on-line data, and future developments. The SPHERE
Data Center is operational and has already provided reduced data with a good
reactivity to many observers. The first public reduced data have been made
available in 2017. The SPHERE Data Center is gathering a strong expertise on
SPHERE data and is in a very good position to propose new reduced data in the
future, as well as improved reduction procedures.Comment: SF2A proceeding
Histogram Monte Carlo study of next-nearest-neighbor Ising antiferromagnet on a stacked triangular lattice
Critical properties of the Ising model on a stacked triangular lattice, with
antiferromagnetic first and second-neighbor in-plane interactions, are studied
by extensive histogram Monte Carlo simulations. The results, in conjunction
with the recently determined phase diagram, strongly suggest that the
transition from the period-3 ordered state to the paramagnetic phase remains in
the xy universality class. This conclusion is in contrast with a previous
suggestion of mean-field tricritical behavior.Comment: 13 pages (RevTex 3.0), 10 figures available upon request, CRPS-93-0
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