92,772 research outputs found
From top-hat masking to smooth transitions: P-filter and its application to polarized microwave sky maps
In CMB science, the simplest idea to remove a contaminated sky region is to
multiply the sky map with a mask that is 0 for the contaminated region and 1
elsewhere, which is also called a top-hat masking. Although it is easy to use,
such top-hat masking is known to suffer from various leakage problems.
Therefore, we want to extend the top-hat masking to a series of semi-analytic
functions called the P-filters. Most importantly, the P-filters can seamlessly
realize the core idea of masking in CMB science, and, meanwhile, guarantee
continuity up to the first derivative everywhere. The P-filters can
significantly reduce many leakage problems without additional cost, including
the leakages due to low-, high-, and band-pass filtering, and the E-to-E,
B-to-B, B-to-E, and E-to-B leakages. The workings of the P-filter are
illustrated by using the WMAP and Planck polarization sky maps. By comparison
to the corresponding WMAP/Planck masks, we show that the P-filter performs much
better than top-hat masking, and meanwhile, has the potential to supersede the
principal idea of masking in CMB science. Compared to mask apodization, the
P-filter is ``outward'', that tends to make proper use of the region that was
marked as 0; whereas apodization is ``inward'', that always kills more signal
in the region marked as 1.Comment: 19 pages and 11 figure
Contact lines for fluid surface adhesion
When a fluid surface adheres to a substrate, the location of the contact line
adjusts in order to minimize the overall energy. This adhesion balance implies
boundary conditions which depend on the characteristic surface deformation
energies. We develop a general geometrical framework within which these
conditions can be systematically derived. We treat both adhesion to a rigid
substrate as well as adhesion between two fluid surfaces, and illustrate our
general results for several important Hamiltonians involving both curvature and
curvature gradients. Some of these have previously been studied using very
different techniques, others are to our knowledge new. What becomes clear in
our approach is that, except for capillary phenomena, these boundary conditions
are not the manifestation of a local force balance, even if the concept of
surface stress is properly generalized. Hamiltonians containing higher order
surface derivatives are not just sensitive to boundary translations but also
notice changes in slope or even curvature. Both the necessity and the
functional form of the corresponding additional contributions follow readily
from our treatment.Comment: 8 pages, 2 figures, LaTeX, RevTeX styl
The circular SiZer, inferred persistence of shape parameters and application to early stem cell differentiation
We generalize the SiZer of Chaudhuri and Marron (J. Amer. Statist. Assoc. 94
(1999) 807-823, Ann. Statist. 28 (2000) 408-428) for the detection of shape
parameters of densities on the real line to the case of circular data. It turns
out that only the wrapped Gaussian kernel gives a symmetric, strongly Lipschitz
semi-group satisfying "circular" causality, that is, not introducing possibly
artificial modes with increasing levels of smoothing. Some notable differences
between Euclidean and circular scale space theory are highlighted. Based on
this, we provide an asymptotic theory to make inference about the persistence
of shape features. The resulting circular mode persistence diagram is applied
to the analysis of early mechanically-induced differentiation in adult human
stem cells from their actin-myosin filament structure. As a consequence, the
circular SiZer based on the wrapped Gaussian kernel (WiZer) allows the
verification at a controlled error level of the observation reported by Zemel
et al. (Nat. Phys. 6 (2010) 468-473): Within early stem cell differentiation,
polarizations of stem cells exhibit preferred directions in three different
micro-environments.Comment: Published at http://dx.doi.org/10.3150/15-BEJ722 in the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Discriminating dynamical from additive noise in the Van der Pol oscillator
We address the distinction between dynamical and additive noise in time
series analysis by making a joint evaluation of both the statistical continuity
of the series and the statistical differentiability of the reconstructed
measure. Low levels of the latter and high levels of the former indicate the
presence of dynamical noise only, while low values of the two are observed as
soon as additive noise contaminates the signal. The method is presented through
the example of the Van der Pol oscillator, but is expected to be of general
validity for continuous-time systems.Comment: 12 pages (Elsevier LaTeX class), 4 EPS figures, submitted to Physica
D (4 july 2001
Integrated Analysis of Pressure Transient Tests in the Gulf of Mexico
Imperial Users onl
- …