423 research outputs found
Wavelength Dependent PSFs and their impact on Weak Lensing Measurements
We measure and model the wavelength dependence of the PSF in the Hyper
Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey. We find that PSF
chromaticity is present in that redder stars appear smaller than bluer stars in
the and -bands at the 1-2 per cent level and in the and
-bands at the 0.1-0.2 per cent level. From the color dependence of the PSF,
we fit a model between the monochromatic PSF trace radius, , and wavelength
of the form . We find values of between -0.2
and -0.5, depending on the epoch and filter. This is consistent with the
expectations of a turbulent atmosphere with an outer scale length of m, indicating that the atmosphere is dominating the chromaticity. We
find evidence in the best seeing data that the optical system and detector also
contribute some wavelength dependence. Meyers and Burchat (2015) showed that
must be measured to an accuracy of not to dominate the
systematic error budget of the Large Synoptic Survey Telescope (LSST) weak
lensing (WL) survey. Using simple image simulations, we find that can be
inferred with this accuracy in the and -bands for all positions in the
LSST field of view, assuming a stellar density of 1 star arcmin and that
the optical PSF can be accurately modeled. Therefore, it is possible to correct
for most, if not all, of the bias that the wavelength-dependent PSF will
introduce into an LSST-like WL survey.Comment: 14 pages, 10 figures. Submitted to MNRAS. Comments welcom
Childhood intermittent and persistent rhinitis prevalence and climate and vegetation: A global ecologic analysis
Background: The effect of climate change and its effects on vegetation growth, and consequently on rhinitis,are uncertain.Objective: To examine between- and within-country associations of climate measures and the normalizeddifference vegetation index with intermittent and persistent rhinitis symptoms in a global context.Methods: Questionnaire data from 6- to 7-year-olds and 13- to 14-year-olds were collected in phase 3 of theInternational Study of Asthma and Allergies in Childhood. Associations of intermittent (>1 symptom reportbut not for 2 consecutive months) and persistent (symptoms for -2 consecutive months) rhinitis symptomprevalences with temperature, precipitation, vapor pressure, and the normalized difference vegetation indexwere assessed in linear mixed-effects regression models adjusted for gross national income and populationdensity. The mean difference in prevalence per 100 children (with 95% confidence intervals [CIs]) perinterquartile range increase of exposure is reported.Results: The country-level intermittent symptom prevalence was associated with several country-levelclimatic measures, including the country-level mean monthly temperature (6.09-C; 95% CI, 2.06e10.11-C per 10.4-C), precipitation (3.10 mm; 95% CI, 0.46e5.73 mm; per 67.0 mm), and vapor pressure(6.21 hPa; 95% CI, 2.17e10.24 hPa; per 10.4 hPa) among 13- to 14-year-olds (222 center in 94 countries).The center-level persistent symptom prevalence was positively associated with several center-level climaticmeasures. Associations with climate were also found for the 6- to 7-year-olds (132 center in 57countries).Conclusion: Several between- and within-country spatial associations between climatic factors and intermittentand persistent rhinitis symptom prevalences were observed. These results provide suggestive evidencethat climate (and future changes in climate) may influence rhinitis symptom prevalence
CoSyR: a novel beam dynamics code for the modeling of synchrotron radiation effects
The self-consistent nonlinear dynamics of a relativistic charged particle
beam interacting with its complete self-fields is a fundamental problem
underpinning many of the accelerator design issues in high brightness beam
applications, as well as the development of advanced accelerators.
Particularly, synchrotron radiation induced effects in a magnetic dispersive
beamline element can lead to collective beam instabilities and emittance
growth. A novel beam dynamic code is developed based on a Lagrangian method for
the calculation of the particles' radiation near-fields using wavefront/wavelet
meshes via the Green's function of the Maxwell equations. These fields are then
interpolated onto a moving mesh for dynamic update of the beam. This method
allows radiation co-propagation and self-consistent interaction with the beam
in the simulation at greatly reduced numerical errors. Multiple levels of
parallelisms are inherent in this method and implemented in our code CoSyR to
enable at-scale simulations of nonlinear beam dynamics on modern computing
platforms using MPI, multi-threading, and GPUs. CoSyR has been used to evaluate
the transverse and longitudinal coherent radiation effects on the beam and to
investigate beam optics designs proposed for mitigation of beam brightness
degradation in a magnetic bunch compressor. In this paper, the design of CoSyR,
as well as the benchmark with other coherent synchrotron radiation models, are
described and discussed.Comment: 17 pages, 14 figure
Observation and simulation of space-charge effects in a radio-frequency photoinjector using a transverse multibeamlet distribution
Are sedatives and hypnotics associated with increased suicide risk of suicide in the elderly?
<p>Abstract</p> <p>Background</p> <p>While antidepressant-induced suicidality is a concern in younger age groups, there is mounting evidence that these drugs may reduce suicidality in the elderly. Regarding a possible association between other types of psychoactive drugs and suicide, results are inconclusive. Sedatives and hypnotics are widely prescribed to elderly persons with symptoms of depression, anxiety, and sleep disturbance. The aim of this case-control study was to determine whether specific types of psychoactive drugs were associated with suicide risk in late life, after controlling for appropriate indications.</p> <p>Methods</p> <p>The study area included the city of Gothenburg and two adjacent counties (total 65+ population 210 703 at the start of the study). A case controlled study of elderly (65+) suicides was performed and close informants for 85 suicide cases (46 men, 39 women mean age 75 years) were interviewed by a psychiatrist. A population based comparison group (n = 153) was created and interviewed face-to-face. Primary care and psychiatric records were reviewed for both suicide cases and comparison subjects. All available information was used to determine past-month mental disorders in accordance with DSM-IV.</p> <p>Results</p> <p>Antidepressants, antipsychotics, sedatives and hypnotics were associated with increased suicide risk in the crude analysis. After adjustment for affective and anxiety disorders neither antidepressants in general nor SSRIs showed an association with suicide. Antipsychotics had no association with suicide after adjustment for psychotic disorders. Sedative treatment was associated with an almost fourteen-fold increase of suicide risk in the crude analyses and remained an independent risk factor for suicide even after adjustment for any DSM-IV disorder. Having a current prescription for a hypnotic was associated with a four-fold increase in suicide risk in the adjusted model.</p> <p>Conclusion</p> <p>Sedatives and hypnotics were both associated with increased risk for suicide after adjustment for appropriate indications. Given the extremely high prescription rates, a careful evaluation of the suicide risk should always precede prescribing a sedative or hypnotic to an elderly individual.</p
Bo\"otes IV: A New Milky Way Satellite Discovered in the Subaru Hyper Suprime-Cam Survey and Implications for the Missing Satellite Problem
We report on the discovery of a new Milky Way (MW) satellite in Bo\"otes
based on data from the on-going Hyper Suprime-Cam (HSC) Subaru Strategic
Program (SSP). This satellite, named Bo\"otes IV, is the third ultra-faint
dwarf that we have discovered in the HSC-SSP. We have identified a
statistically significant (32.3) overdensity of stars having
characteristics of a metal-poor, old stellar population. The distance to this
stellar system is kpc with a -band absolute
magnitude of mag. Bo\"otes IV has a half-light
radius of pc and an ellipticity of
, which clearly suggests that this is a dwarf satellite
galaxy. We also found another overdensity that appears to be a faint globular
cluster with mag and pc
located at kpc. Adopting the recent prediction for the
total population of satellites in a MW-sized halo by Newton et al. (2018),
which combined the characteristics of the observed satellites by SDSS and DES
with the subhalos obtained in CDM models, we estimate that there
should be about two MW satellites at in the deg covered
by HSC-SSP, whereas that area includes six satellites. Thus, the observed
number of satellites is larger than the theoretical prediction. On the face of
it, we have a problem of too many satellites, instead of the well-known missing
satellites problem whereby the CDM theory overpredicts the number of
satellites in a MW-sized halo. This may imply that the models need more
refinements for the assignment of subhalos to satellites such as considering
those found by the current deeper survey. [abridged]Comment: 13 pages, 11 figures, 2 tables, accepted for publication in PAS
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