3,814 research outputs found
Inferring the magnetic field vector in the quiet Sun. II. Interpreting results from the inversion of Stokes profiles
In a previous paper, we argued that the inversion of Stokes profiles applied
to spectropolarimetric observations of the solar internetwork yield
unrealistically large values of the inclination of the magnetic field vector
(). This is because photon noise in Stokes and are interpreted
by the inversion code as valid signals, that leads to an overestimation of the
transverse component , thus the inclination . However, our
study was based on the analysis of linear polarization signals that featured
only uncorrelated noise. In this paper, we develop this idea further and study
this effect in Stokes and profiles that also show correlated noise. In
addition, we extend our study to the three components of the magnetic field
vector, as well as the magnetic filling factor . With this, we confirm
the tendency to overestimate when inverting linear polarization
profiles that, although non-zero, are still below the noise level. We also
establish that the overestimation occurs mainly for magnetic fields that are
nearly vertical . This indicates that a reliable
inference of the inclination of the magnetic field vector cannot be achieved by
analyzing only Stokes and . In addition, when inverting Stokes and
profiles below the noise, the inversion code retrieves a randomly uniform
distribution of the azimuth of the magnetic field vector . To avoid these
problems, we propose only inverting Stokes profiles for which the linear
polarization signals are sufficiently above the noise level. However, this
approach is also biased because, in spite of allowing for a very accurate
retrieval of the magnetic field vector from the selected Stokes profiles, it
selects only profiles arising from highly inclined magnetic fields.Comment: Accepted for publication in Astronomy and Astrophysics. 14 pages. 7
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Inferring the magnetic field vector in the quiet Sun. III. Disk variation of the Stokes profiles and isotropism of the magnetic field
We have studied the angular distribution of the magnetic field vector in the
solar internetwork employing high-quality data (noise level in units of the quiet-Sun intensity) at different latitudes
recorded with the Hinode/SP instrument. Instead of applying traditional
inversion codes of the radiative transfer equation to retrieve the magnetic
field vector at each spatial point on the solar surface and studying the
resulting distribution of the magnetic field vector, we surmised a theoretical
distribution function of the magnetic field vector and used it to obtain the
theoretical histograms of the Stokes profiles. These histograms were then
compared to the observed ones. Any mismatch between them was ascribed to the
theoretical distribution of the magnetic field vector, which was subsequently
modified to produce a better fit to the observed histograms. With this method
we find that Stokes profiles with signals above (in units of
the continuum intensity) cannot be explained by an isotropic distribution of
the magnetic field vector. We also find that the differences between the
histograms of the Stokes profiles observed at different latitudes cannot be
explained in terms of line-of-sight effects. However, they can be explained by
a distribution of the magnetic field vector that inherently varies with
latitude. We note that these results are based on a series of assumptions that,
although briefly discussed in this paper, need to be considered in more detail
in the future.Comment: Accepted for publication in Astronomy and Astrophysics. 14 pages, 8
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P53 IMMUNOHISTOCHEMISTRY AS A SURROGATE FOR TP53 MUTATIONAL ANALYSIS IN ENDOMETRIAL CANCER BIOPSIES
Meeting abstract from 17th Biennial Meeting of the International Gynecologic Cancer Society Kyoto, Japan September 14-16, 201
A Universal Scaling Law for Jets of Collapsing Bubbles
Cavitation bubbles collapsing and rebounding in a pressure gradient grad(p)
form a "micro-jet" enveloped by a "vapor jet". This letter presents
unprecedented observations of the vapor jets formed in a uniform
gravity-induced grad(p), modulated aboard parabolic flights. The data uncovers
that the normalized jet volume is independent of the liquid density and
viscosity and proportional to zeta=grad(p)*R0/p, where R0 is the maximal bubble
radius and p is the driving pressure. A derivation inspired by "Kelvin-Blake"
considerations confirms this law and reveals its negligible dependence of
surface tension. We further conjecture that the jet only pierces the bubble
boundary if zeta>0.0004.Comment: 4 page letter, 4 figure
Increased roll tilt thresholds are associated with subclinical postural instability in asymptomatic adults aged 21 to 84 years
BackgroundBalance assessments that intentionally alter the reliability of visual and proprioceptive feedback (e.g., standing on foam with eyes closed) have become a standard approach for identifying vestibular mediated balance dysfunction in older adults. However, such assessments cannot discern which specific element of the vestibular system (e.g., semicircular canal, otolith, or combined canal-otolith) underlies the observed age-related changes in balance performance. The present study was designed to determine the associations between specific sources of vestibular noise and quantitative measures of quiet stance postural control measured during standard âvestibularâ balance conditions.MethodsA group of 52 asymptomatic adults (53.21 ± 19.7, 21 to 84 years) without a history of vestibular or neurologic disorders volunteered for this study. We measured a battery of five vestibular perceptual thresholds that assay vestibular noise with predominant contributions from the vertical canals, lateral canals, utricles, saccules, and the centrally integrated canal-otolith signal. In addition, participants completed two standard balance assessments that were each designed to prioritize the use of vestibular cues for quiet stance postural controlâeyes closed on foam (Condition 4 of the Modified Romberg Balance Test) and eyes closed, on a sway referenced support surface (Condition 5 of the Sensory Organization Test).ResultsIn age adjusted models, we found strong positive associations between roll tilt vestibular thresholds, a measure of noise in the centrally integrated canal-otolith signal, and the root mean square distance (RMSD) of the anteroposterior and mediolateral center of pressure (CoP) captured during eyes closed stance on a sway referenced support surface. The strength of the association between roll tilt thresholds and the RMSD of the CoP was between 3-times and 30-times larger than the association between postural sway and each of the other vestibular thresholds measured.ConclusionWe posit that noise in the centrally estimated canal-otolith âtiltâ signal may be the primary driver of the subclinical postural instability experienced by older adults during the âvestibularâ conditions of balance assessments. Additional testing in adults with clinical balance impairment are needed to identify if roll tilt thresholds may also serve as a surrogate metric by which to detect vestibular mediated balance dysfunction and/or fall risk
Studies of New Vector Resonances at the CLIC Multi-TeV e+e- Collider
Several models predict the existence of new vector resonances in the
multi-TeV region, which can be produced in high energy e+e- collisions in the
s-channel. In this paper we review the existing limits on the masses of these
resonances from LEP/SLC and TEVATRON data and from atomic parity violation in
some specific models. We study the potential of a multi-TeV e+e- collider, such
as CLIC, for the determination of their properties and nature.Comment: 17 pages, 16 EPS figures, uses JHEP3.cl
Two-Fermion Production in Electron-Positron Collisions
This report summarizes the results of the two-fermion working group of the
LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the
theoretical calculations of the two fermion production process in the
electron-positron collision at LEP2 center of the mass energies are reported.
The Bhabha process and the production of muon, tau, neutrino and quark pairs is
covered. On the basis of comparison of various calculations, theoretical
uncertainties are estimated and compared with those needed for the final LEP2
data analysis. The subjects for the further studies are identified.Comment: 2-fermion working group report of the LEP2 Monte Carlo Workshop
1999/2000, 113 pages, 24 figures, 35 table
The continuum intensity as a function of magnetic field I. Active region and quiet Sun magnetic elements
Small-scale magnetic fields are major contributors to the solar irradiance
variations. Hence, the continuum intensity contrast of magnetic elements in the
quiet Sun (QS) network and in active region (AR) plage is an essential quantity
that needs to be measured reliably. By using Hinode/SP disk center data at a
constant, high spatial resolution, we aim at updating results of earlier
ground-based studies of contrast vs. magnetogram signal, and to look for
systematic differences between AR plages and QS network. The field strength,
filling factor and inclination of the field was retrieved by Milne-Eddington
inversion (VFISV). As in earlier studies, we performed a pixel-by-pixel study
of 630.2 nm continuum contrast vs. apparent (i.e. averaged over a pixel)
longitudinal magnetic field over large fields of view in ARs and in the QS. The
contrast of magnetic elements reaches larger values in the QS (on average 3.7%)
than in ARs (1.3%). This could not be attributed to any systematic difference
in the chosen contrast references. At Hinode's spatial resolution, the
relationship between contrast and apparent longitudinal field strength exhibits
a peak at around 700 G in both the QS and ARs, whereas earlier lower resolution
studies only found a peak in the QS and a monotonous decrease in ARs. We
attribute this discrepancy both to our careful removal of the pores and their
close surroundings affected by the telescope diffraction, as well as to the
enhanced spatial resolution and very low scattered light of the Hinode Solar
Optical Telescope. According to our inversions, the magnetic elements producing
the peak of the contrast curves have similar properties (field strength,
inclination, filling factor) in ARs and in the QS, so that the larger
brightness of magnetic elements in the QS remains unexplained.Comment: 8 figures, 14 page
Micro-fabrication of Carbon Structures by Pattern Miniaturization in Resorcinol-Formaldehyde Gel
A simple and novel method to fabricate and miniaturize surface and
sub-surface micro-structures and micro-patterns in glassy carbon is proposed
and demonstrated. An aqueous resorcinol-formaldehyde (RF) sol is employed for
micro-molding of the master-pattern to be replicated, followed by controlled
drying and pyrolysis of the gel to reproduce an isotropically shrunk replica in
carbon. The miniaturized version of the master-pattern thus replicated in
carbon is about one order of magnitude smaller than original master by
repeating three times the above cycle of molding and drying. The
micro-fabrication method proposed will greatly enhance the toolbox for a facile
fabrication of a variety of Carbon-MEMS and C-microfluidic devices.Comment: 16 pages, 5 figure
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