771 research outputs found
Ray tracing of ion-cyclotron waves in a coronal funnel
Remote observations of coronal holes have strongly implicated the kinetic
interactions of ion-cyclotron waves with ions as a principal mechanism for
plasma heating and acceleration of the fast solar wind. In order to study these
waves, a linear perturbation analysis is used in the work frame of the
collisionless multi-fluid model. We consider a non-uniform background plasma
describing a funnel region and use the ray tracing equations to compute the ray
path of the waves as well as the spatial variation of their properties.Comment: 4 pages, 3 figures Modern Solar Facilities, Advanced Solar Science,
Universitatsverlag Goettingen 200
Immunohistochemical characterization of the 'intimal proliferation' phenomenon in Sneddon's syndrome and essential thrombocythaemia
Cellular changes were immunocytochemically characterized in skin vessels of five patients with idiopathic generalized racemose livedo (Sneddon's syndrome), and one patient with localized racemose livedo associated with essential thrombocythaemia. Antibodies against alpha-smooth muscle-actin, tropomyosin, desmin, vimentin, factor VIII-related antigen, human endothelial cells (CD31), human macrophages (CD68), and HLA-DR positive cells (CR3/43) were used. Conventional light microscopy showed, in all cases, intimal thickening of ascending arteries and arterioles as a result of an accumulation of cells and extracellular hyalinized material. None of the specimens showed infiltration with polymorphonuclear leucocytes or macrophages. The cells in the region of the intimal hyperplasia showed intense positive immunostaining for alpha-smooth muscle actin and tropomyosin. Staining for the intermediate filament desmin was localized to the resident smooth muscle cells of the media, whereas staining for vimentin was found in all types of cells in both the intima and media. Positive immunostaining for factor VIII-related antigen and CD31 was strictly confined to the endothelial cells lining the narrowed lumina of the vessels. No positive staining with either antibody was observed in totally occluded vessels. Cells in the subintimal space did not show reactivity for CD68 in any of the specimens, but two cases showed solitary cells with positive staining for HLA-DR in this region. There were no differences in staining pattern between Sneddon's syndrome and essential thrombocythaemia with any of the antibodies. Our results support the assumption that the 'intimal proliferation' in both diseases is caused by colonization of the subendothelial space with contractile cells of possible smooth muscle origin.(ABSTRACT TRUNCATED AT 250 WORDS
Spectroscopic Observations of Propagating Disturbances in a Polar Coronal Hole: Evidence of Slow Magneto-acoustic Waves
We focus on detecting and studying quasi-periodic propagating features that
have been interpreted both in terms of slow magneto-acoustic waves and of high
speed upflows. We analyze long duration spectroscopic observations of the
on-disk part of the south polar coronal hole taken on 1997 February 25 by the
SUMER spectrometer aboard SOHO. We calibrated the velocity with respect to the
off-limb region and obtain time--distance maps in intensity, Doppler velocity
and line width. We also perform a cross correlation analysis on different time
series curves at different latitudes. We study average spectral line profiles
at the roots of propagating disturbances and along the propagating ridges, and
perform a red-blue asymmetry analysis. We find the clear presence of
propagating disturbances in intensity and Doppler velocity with a projected
propagation speed of about km s and a periodicity of
14.5 min. To our knowledge, this is the first simultaneous detection
of propagating disturbances in intensity as well as in Doppler velocity in a
coronal hole. During the propagation, an intensity enhancement is associated
with a blue-shifted Doppler velocity. These disturbances are clearly seen in
intensity also at higher latitudes (i.e. closer to the limb), while
disturbances in Doppler velocity becomes faint there. The spectral line
profiles averaged along the propagating ridges are found to be symmetric, to be
well fitted by a single Gaussian, and have no noticeable red-blue asymmetry.
Based on our analysis, we interpret these disturbances in terms of propagating
slow magneto-acoustic waves.Comment: accepted for publication by A&
Coronal ion-cyclotron beam instabilities within the multi-fluid description
Spectroscopic observations and theoretical models suggest resonant
wave-particle interactions, involving high-frequency ion-cyclotron waves, as
the principal mechanism for heating and accelerating ions in the open coronal
holes. However, the mechanism responsible for the generation of the
ion-cyclotron waves remains unclear. One possible scenario is that ion beams
originating from small-scale reconnection events can drive micro-instabilities
that constitute a possible source for the excitation of ion-cyclotron waves. In
order to study ion beam-driven electromagnetic instabilities, the multi-fluid
model in the low-beta coronal plasma is used. While neglecting the electron
inertia this model allows one to take into account ion-cyclotron wave effects
that are absent from the one-fluid MHD model. Realistic models of density and
temperature as well as a 2-D analytical magnetic field model are used to define
the background plasma in the open-field funnel region of a polar coronal hole.
Considering the WKB approximation, a Fourier plane-wave linear mode analysis is
employed in order to derive the dispersion relation. Ray-tracing theory is used
to compute the ray path of the unstable wave as well as the evolution of the
growth rate of the wave while propagating in the coronal funnel. We demonstrate
that, in typical coronal holes conditions and assuming realistic values of the
beam velocity, the free energy provided by the ion beam propagating parallel
the ambient field can drive micro-instabilities through resonant ion-cyclotron
excitation.Comment: 8 pages, 6 figures, submitted to A&
Gyrokinetic Simulations of Solar Wind Turbulence from Ion to Electron Scales
The first three-dimensional, nonlinear gyrokinetic simulation of plasma
turbulence resolving scales from the ion to electron gyroradius with a
realistic mass ratio is presented, where all damping is provided by resolved
physical mechanisms. The resulting energy spectra are quantitatively consistent
with a magnetic power spectrum scaling of as observed in \emph{in
situ} spacecraft measurements of the "dissipation range" of solar wind
turbulence. Despite the strongly nonlinear nature of the turbulence, the linear
kinetic \Alfven wave mode quantitatively describes the polarization of the
turbulent fluctuations. The collisional ion heating is measured at
sub-ion-Larmor radius scales, which provides the first evidence of the ion
entropy cascade in an electromagnetic turbulence simulation.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Integrating Addiction Treatment into Primary Care Using Mobile Health Technology: Protocol for an Implementation Research Study
Healthcare reform in the United States is encouraging Federally Qualified Health Centers and other primary-care practices to integrate treatment for addiction and other behavioral health conditions into their practices. The potential of mobile health technologies to manage addiction and comorbidities such as HIV in these settings is substantial but largely untested. This paper describes a protocol to evaluate the implementation of an E-Health integrated communication technology delivered via mobile phones, called Seva, into primary-care settings. Seva is an evidence-based system of addiction treatment and recovery support for patients and real-time caseload monitoring for clinicians
On the nature of spectral line broadening in solar coronal dimmings
We analyze the profiles of iron emission lines observed in solar coronal
dimmings associated with coronal mass ejections, using the EUV Imaging
Spectrometer on board Hinode. We quantify line profile distortions with
empirical coefficients (asymmetry and peakedness) that compare the fitted
Gaussian to the data. We find that the apparent line broadenings reported in
previous studies are likely to be caused by inhomogeneities of flow velocities
along the line of sight, or at scales smaller than the resolution scale, or by
velocity fluctuations during the exposure time. The increase in the amplitude
of Alfv\'en waves cannot, alone, explain the observed features. A
double-Gaussian fit of the line profiles shows that, both for dimmings and
active region loops, one component is nearly at rest while the second component
presents a larger Doppler shift than that derived from a single-Gaussian fit.Comment: 16 pages, 11 figures - Accepted for publication in Ap
Legionella bozemanii , an Elusive Agent of Fatal Cavitary Pneumonia
Abstract : A 67-year-old patient died of Legionella bozemanii pneumonia with negative urinary antigen and negative serology. Cystic lesions in pneumonia of unknown origin should lead to the differential diagnosis of L. bozemanii infection
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