276 research outputs found
Lymphoedema in patients with lentigo maligna treated with imiquimod: A long-term adverse effect
Cut and paste invariants of manifolds via algebraic K-theory
Recent work of Jonathan Campbell and Inna Zakharevich has focused on building machinery for studying scissors congruence problems via algebraic -theory, and applying these tools to studying the Grothendieck ring of varieties. In this paper we give a new application of their framework: we construct a -space that recovers the classical ("schneiden und kleben," German for "cut and paste") groups for manifolds on , and we construct a derived version of the Euler characteristic
Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere
We study horizontal supergranule-scale motions revealed by TRACE observation
of the chromospheric emission, and investigate the coupling between the
chromosphere and the underlying photosphere. A highly efficient
feature-tracking technique called balltracking has been applied for the first
time to the image sequences obtained by TRACE (Transition Region and Coronal
Explorer) in the passband of white light and the three ultraviolet passbands
centered at 1700 {\AA}, 1600 {\AA}, and 1550 {\AA}. The resulting velocity
fields have been spatially smoothed and temporally averaged in order to reveal
horizontal supergranule-scale motions that may exist at the emission heights of
these passbands. We find indeed a high correlation between the horizontal
velocities derived in the white-light and ultraviolet passbands. The horizontal
velocities derived from the chromospheric and photospheric emission are
comparable in magnitude. The horizontal motions derived in the UV passbands
might indicate the existence of a supergranule-scale magnetoconvection in the
chromosphere, which may shed new light on the study of mass and energy supply
to the corona and solar wind at the height of the chromosphere. However, it is
also possible that the apparent motions reflect the chromospheric brightness
evolution as produced by acoustic shocks which might be modulated by the
photospheric granular motions in their excitation process, or advected partly
by the supergranule-scale flow towards the network while propagating upward
from the photosphere. To reach a firm conclusion, it is necessary to
investigate the role of granular motions in the excitation of shocks through
numerical modeling, and future high-cadence chromospheric magnetograms must be
scrutinized.Comment: 5 figures, accepted by Astronomy & Astrophysic
Recommended from our members
The first molecular phylogeny of Chilodontidae (Teleostei: Ostariophysi: Characiformes) reveals cryptic biodiversity and taxonomic uncertainty
Chilodontidae is a small family of eight described characiform species popularly
known as headstanders. These small to moderately sized fishes are well known to
aquarists, who prize their striking spotted pigmentation and unusual behaviors, and to
systematists, who have revised both chilodontid genera in recent memory and studied
their phylogenetic relationships using a comprehensive morphological dataset.
However, no molecular phylogeny for the family has ever been proposed. Here, we
reconstruct phylogenetic relationships for all eight known chilodontid species using
three mitochondrial and two nuclear loci. Results largely agree with the previous
morphological hypothesis, and confirm the monophyly of the family as well as its
included genera, Caenotropus and Chilodus. The molecular topology differs slightly
from the morphological hypothesis by placing Caenotropus maculosus rather than C.
mestomorgmatos as the sister to the remaining three congeners, and by reconstructing
the Curimatidae as the closest outgroup family, rather than the Anostomidae. However,
the topologies supported by the morphological data were only slightly less likely and
could not be rejected via Shimodaira-Hasegawa tests. Within Chilodus, two described
species with distinctive pigmentation (C. fritillus and C. zunevei) appear embedded
within the broad distributed C. punctatus clade, suggesting the presence of cryptic taxa
with polymorphic pigmentation within the present concept of C. punctatus. Future work
should combine morphological and molecular data to revisit the taxonomy and
systematics of Chilodus and determine species limits within the C. punctatus-group
sensu lato.Keywords: Freshwater fishes, Headstanders, Multilocus analysis, AmazonKeywords: Freshwater fishes, Headstanders, Multilocus analysis, Amazo
Biosynthesis of normal and low-molecular-mass complement component C1q by cultured human monocytes and macrophages
The Missing Luminous Blue Variables and the Bistability Jump
We discuss an interesting feature of the distribution of luminous blue
variables on the H-R diagram, and we propose a connection with the bistability
jump in the winds of early-type supergiants. There appears to be a deficiency
of quiescent LBVs on the S Dor instability strip at luminosities between log
L/Lsun = 5.6 and 5.8. The upper boundary, is also where the
temperature-dependent S Dor instability strip intersects the bistability jump
at about 21,000 K. Due to increased opacity, winds of early-type supergiants
are slower and denser on the cool side of the bistability jump, and we
postulate that this may trigger optically-thick winds that inhibit quiescent
LBVs from residing there. We conduct numerical simulations of radiation-driven
winds for a range of temperatures, masses, and velocity laws at log L/Lsun=5.7
to see what effect the bistability jump should have. We find that for
relatively low stellar masses the increase in wind density at the bistability
jump leads to the formation of a modest to strong pseudo photosphere -- enough
to make an early B-type star appear as a yellow hypergiant. Thus, the proposed
mechanism will be most relevant for LBVs that are post-red supergiants. Yellow
hypergiants like IRC+10420 and rho Cas occupy the same luminosity range as the
``missing'' LBVs, and show apparent temperature variations at constant
luminosity. If these yellow hypergiants do eventually become Wolf-Rayet stars,
we speculate that they may skip the normal LBV phase, at least as far as their
apparent positions on the HR diagram are concerned.Comment: 20 pages, 4 figs, accepted by Ap
New developments in ICRF antennas and non-traditional applications of HF power on TEXTOR
This paper reviews the present status of new developments in ICRF antennas, recent results on more realistic modeling of ICRF antennas using the 3-D full electromagnetic code ICANT and, finally, the latest development in the scenarios of non-traditional applications of HF power for wall conditioning
In vivo biocompatibility assessment of (PTFE–PVDF–PP) terpolymer-based membrane with potential application for glaucoma treatment
The aim of the work was to evaluate the in vivo biological behaviour of polymeric membrane materials for glaucoma implants. The base material was biostable synthetic terpolymer (PTFE–PVDF–PP) with proved biocompability (PN-EN ISO 10993). The samples manufactured in the form a membrane were subjected to chemical and physical treatment to create an open pore system within the polymer matrix. As a porogenic phase biodegradable natrium alginate in a fibrous form was employed. The non-perforating deep sclerectomy technique was performed in a rabbit model. The clinical observations were made after 14 and 30 days. During the study clinical symptoms of a moderate degree were observed, and histopathological changes were typical for foreign body implantation. At the end stage of the study no significant difference in histopathological assessment was found between control and experimental group. Similarities observed in both groups and relatively mild histopathological changes in the tissue surrounding the implant indicate that the observed symptoms come from a deep scleral trauma caused by surgery, and not by the presence of the implant itself
DOT Tomography of the Solar Atmosphere VII. Chromospheric Response to Acoustic Events
We use synchronous movies from the Dutch Open Telescope sampling the
G band, Ca II and Halpha with five-wavelength profile sampling to study the
response of the chromosphere to acoustic events in the underlying photosphere.
We first compare the visibility of the chromosphere in Ca II H and Halpha,
demonstrate that studying the chromosphere requires Halpha data, and summarize
recent developments in understanding why this is so. We construct divergence
and vorticity maps of the photospheric flow field from the G-band images and
locate specific events through the appearance of bright Ca II H grains. The
reaction of the Halpha chromosphere is diagnosed in terms of brightness and
Doppler shift. We show and discuss three particular cases in detail: a regular
acoustic grain marking shock excitation by granular dynamics, a persistent
flasher which probably marks magnetic-field concentration, and an exploding
granule. All three appear to buffet overlying fibrils, most clearly in
Dopplergrams. Although our diagnostic displays to dissect these phenomena are
unprecedentedly comprehensive, adding even more information (photospheric
Doppler tomography and magnetograms, chromospheric imaging and Doppler mapping
in the ultraviolet) is warranted.Comment: accepted by Solar Physic
- …