2,364 research outputs found
Electronic switching circuit uses complementary non-linear components
Inherent switching properties of saturable inductors and storage diodes are combined to perform large variety of electronic functions, such as pulse shaping, gating, and multiplexing. Passive elements replace active switching devices in generation of complex waveforms
Correcting systematic effects in a large set of photometric light curves
We suggest a new algorithm to remove systematic effects in a large set of light curves obtained by a photometric survey. The algorithm can remove systematic effects, such as those associated with atmospheric extinction, detector efficiency, or point spread function changes over the detector. The algorithm works without any prior knowledge of the effects, as long as they linearly appear in many stars of the sample. The approach, which was originally developed to remove atmospheric extinction effects, is based on a lower rank approximation of matrices, an approach which has already been suggested and used in chemometrics, for example. The proposed algorithm is especially useful in cases where the uncertainties of the measurements are unequal. For equal uncertainties, the algorithm reduces to the Principal Component Analysis (PCA) algorithm. We present a simulation to demonstrate the effectiveness of the proposed algorithm and we point out its potential, in the search for transit candidates in particula
Correcting systematic effects in a large set of photometric lightcurves
We suggest a new algorithm to remove systematic effects in a large set of
lightcurves obtained by a photometric survey. The algorithm can remove
systematic effects, like the ones associated with atmospheric extinction,
detector efficiency, or PSF changes over the detector. The algorithm works
without any prior knowledge of the effects, as long as they linearly appear in
many stars of the sample. The approach, which was originally developed to
remove atmospheric extinction effects, is based on a lower rank approximation
of matrices, an approach which was already suggested and used in chemometrics,
for example. The proposed algorithm is specially useful in cases where the
uncertainties of the measurements are unequal. For equal uncertainties the
algorithm reduces to the Principal Components Analysis (PCA) algorithm. We
present a simulation to demonstrate the effectiveness of the proposed algorithm
and point out its potential, in search for transit candidates in particular.Comment: 6 pages, 2 figure
The orbit of the star S2 around SgrA* from VLT and Keck data
Two recent papers (Ghez et al. 2008, Gillessen et al. 2009) have estimated
the mass of and the distance to the massive black hole in the center of the
Milky Way using stellar orbits. The two astrometric data sets are independent
and yielded consistent results, even though the measured positions do not match
when simply overplotting the two sets. In this letter we show that the two sets
can be brought to excellent agreement with each other when allowing for a small
offset in the definition of the reference frame of the two data sets. The
required offsets in the coordinates and velocities of the origin of the
reference frames are consistent with the uncertainties given in Ghez et al.
(2008). The so combined data set allows for a moderate improvement of the
statistical errors of mass of and distance to Sgr A*, but the overall
accuracies of these numbers are dominated by systematic errors and the
long-term calibration of the reference frame. We obtain R0 = 8.28 +- 0.15(stat)
+- 0.29(sys) kpc and M(MBH) = 4.30 +- 0.20(stat) +- 0.30(sys) x 10^6 Msun as
best estimates from a multi-star fit.Comment: submitted to ApJ
Investigation of the New Local Group Galaxy VV 124
We present the results of our stellar photometry and spectroscopy for the new
Local Group galaxy VV 124 (UGC 4879) obtained with the 6-m BTA telescope. The
presence of a few bright supergiants in the galaxy indicates that the current
star formation process is weak. The apparent distribution of stars with
different ages in VV 124 does not differ from the analogous distributions of
stars in irregular galaxies, but the ratio of the numbers of young and old
stars indicates that VV 124 belongs to the rare Irr/Sph type of galaxies. The
old stars (red giants) form the most extended structure, a thick disk with an
exponential decrease in the star number density to the edge. Definitely, the
young population unresolvable in images makes a great contribution to the
background emission from the central galactic regions. The presence of young
stars is also confirmed by the [O III] emission line visible in the spectra
that belongs to extensive diffuse galactic regions. The mean radial velocity of
several components (two bright supergiants, the unresolvable stellar
population, and the diffuse gas) is v_h = -70+/-15 km/s and the velocity with
which VV 124 falls into the Local Group is v_LG = -12+/-15 km/s. We confirm the
distance to the galaxy D = 1.1+/-0.1 Mpc and the metallicity of red giants
([Fe/H] = -1.37) found by Kopylov et al. (2008).VV 124 is located on the
periphery of the Local Group approximately at the same distance from M 31 and
our Galaxy and is isolated from other galaxies. The galaxy LeoA nearest to it
is 0.5 Mpc away.Comment: 10 pages, 8 figures. Accepted for publication in Astronomy Letters
(2010, Vol. 36, No. 5, pp. 309-318
On orbifold theory and N=2, D=5 gauged supergravity
We have studied the most general N=2 supergravity in five dimensions in
context with the orbifold theory based on . Various ways to
treat the supersymmetry with singular sources placed in orbifold fixed points
were proposed in past. Supersymmetric branes were consistently introduced in a
bulk where a gauged supergravity was present. In this paper we find that in the
supergravity with general gauging, the possibility to obtain a
supersymmetric brane world is constrained. Imposing the compatibility of
supersymmetry transformation rules with the orbifold condition, we find the
necessary and sufficient condition to obtain supersymmetric branes and bulk
independently. We comment that the same condition guarantees naturally the
presence of singular BPS solutions.Comment: 16 page
Abnormal plasma clot structure and stability distinguish bleeding risk in patients with severe factor XI deficiency
Factor XI (FXI) deficiency is a rare autosomal recessive disorder. Many patients with even very low FXI levels (<20 IU/dL) are asymptomatic or exhibit only mild bleeding, whereas others experience severe bleeding usually following trauma. Neither FXI antigen nor activity predicts bleeding risk in FXI-deficient patients
Primer for Experimental Methods in Organization Theory
Experiments have long played a crucial role in various scientific disciplines and have been gaining ground in organization theory, where they add unique value by establishing causality and uncovering theoretical mechanisms. This essay provides an overview of the merits and procedures of the experimental methodology, with an emphasis on its application to organization theory. Drawing on the historical roots of experiments and their impact across science, we argue the method holds immense potential for furthering organization theory. We highlight key advantages of experimental methods, including high internal and construct validity, vividness in communicating findings, the capacity to examine complex and understudied phenomena, and the identification of microfoundations and theoretical mechanisms. We alleviate some concerns about external validity and offer guidance for designing and conducting sound, reproducible experimental research. Ultimately, we contend that the current experimental turn holds the potential to reorient organization theory. History: This paper has been accepted for the Organization Science Special Issue on Experiments in Organizational Theory. Funding: This work was supported by the Otto Moensted Foundation, which granted the Otto Moensted Visiting Professorship to S. S. Levine, and a National Science Foundation CAREER Award from the Directorate for Social, Behavioral and Economic Sciences [Grant 1943688] to O. Schilke. Supplemental Material: The online appendix is available at https://doi.org/10.1287/orsc.2023.18093
An all-sky search algorithm for continuous gravitational waves from spinning neutron stars in binary systems
Rapidly spinning neutron stars with non-axisymmetric mass distributions are
expected to generate quasi-monochromatic continuous gravitational waves. While
many searches for unknown, isolated spinning neutron stars have been carried
out, there have been no previous searches for unknown sources in binary
systems. Since current search methods for unknown, isolated neutron stars are
already computationally limited, expanding the parameter space searched to
include binary systems is a formidable challenge. We present a new hierarchical
binary search method called TwoSpect, which exploits the periodic orbital
modulations of the continuous waves by searching for patterns in doubly
Fourier-transformed data. We will describe the TwoSpect search pipeline,
including its mitigation of detector noise variations and corrections for
Doppler frequency modulation caused by changing detector velocity. Tests on
Gaussian noise and on a set of simulated signals will be presented.Comment: 22 pages, 10 figures, 1 table, Submitted to Classical and Quantum
Gravit
Identification of Globular Cluster Stars in RAVE data II: Extended tidal debris around NGC 3201
We report the identification of extended tidal debris potentially associated with the globular cluster NGC 3201, using the RAdial Velocity Experiment (RAVE) catalogue. We find the debris stars are located at a distance range of 1â7 kpc based on the forthcoming RAVE distance estimates. The derived space velocities and integrals of motion show interesting connections to NGC 3201, modulo uncertainties in the proper motions. Three stars, which are among the four most likely candidates for NGC 3201 tidal debris, are separated by 80° on the sky yet are well matched by the 12 Gyr, [Fe/H] = â1.5 isochrone appropriate for the cluster. This is the first time tidal debris around this cluster has been reported over such a large spatial extent, with implications for the cluster's origin and dynamical evolution
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