776 research outputs found
Petrologic and geophysical study of the source of long wavelength crustal magnetic anomalies
The magnetic mineralogy and magnetic signature of banded ion formations, diagenetic (unmetamorphosed) and low grade banded iron formations, high-grade mineralogy, and phase equilibria of magnetite inorogenic magmers are discussed
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
Upflows in the upper transition region of the quiet Sun
We investigate the physical meaning of the prominent blue shifts of Ne VIII,
which is observed to be associated with quiet-Sun network junctions (boundary
intersections), through data analyses combining force-free-field extrapolations
with EUV spectroscopic observations. For a middle-latitude region, we
reconstruct the magnetic funnel structure in a sub-region showing faint
emission in EIT-Fe 195. This funnel appears to consist of several smaller
funnels that originate from network lanes, expand with height and finally merge
into a single wide open-field region. However, the large blue shifts of Ne VIII
are generally not associated with open fields, but seem to be associated with
the legs of closed magnetic loops. Moreover, in most cases significant upflows
are found in both of the funnel-shaped loop legs. These quasi-steady upflows
are regarded as signatures of mass supply to the coronal loops rather than the
solar wind. Our observational result also reveals that in many cases the
upflows in the upper transition region (TR) and the downflows in the middle TR
are not fully cospatial. Based on these new observational results, we suggest
different TR structures in coronal holes and in the quiet Sun.Comment: 4 pages, 4 figures, will appear in the Proceedings of the Solar wind
12 conferenc
On ion-cyclotron-resonance heating of the corona and solar wind
This paper concisely summarizes and critically reviews recent work by the authors on models of the heating of the solar corona by resonance of ions with high-frequency waves (up to the proton cyclotron frequency). The quasi-linear theory of pitch angle diffusion is presented in connection with relevant solar wind proton observations. Hybrid fluid-kinetic model equations, which include wave-particle interactions and collisions, are derived. Numerical solutions are discussed, representative of the inner corona and near-Sun solar wind. A semi-kinetic model for reduced velocity distributions is presented, yielding kinetic results for heavy ions in the solar corona. It is concluded that a self-consistent treatment of particle distributions and wave spectra is required, in order to adequately describe coronal physics and to obtain agreement with observations
COMPARISON OF ORTHODOX WITH FIBREOPTIC OROTRACHEAL INTUBATION UNDER TOTAL I.V. ANAESTHESIA
Fibreoptic orotracheal intubation was compared with orthodox laryngoscopy and tracheal intubation using a total i.v. technique with propofol in 60 ASA I and II patients. There was no significant difference between the two techniques in haemodynamic profile (before, during and following the intubation procedure) and incidence of postoperative sore throat. Minimal oxygen saturation was 96% during the study; maximal end-tidal PCO2 after intubation was 5.4 kPa. Intubation time was faster (P < 0.01) in the orthodox group (30.7 (SEM 2.3) s) than in the fibreoptic group (52.7 (4.8) s
Kinetic Signatures and Intermittent Turbulence in the Solar Wind Plasma
A connection between kinetic processes and intermittent turbulence is
observed in the solar wind plasma using measurements from the Wind spacecraft
at 1 AU. In particular, kinetic effects such as temperature anisotropy and
plasma heating are concentrated near coherent structures, such as current
sheets, which are non-uniformly distributed in space. Furthermore, these
coherent structures are preferentially found in plasma unstable to the mirror
and firehose instabilities. The inhomogeneous heating in these regions, which
is present in both the magnetic field parallel and perpendicular temperature
components, results in protons at least 3-4 times hotter than under typical
stable plasma conditions. These results offer a new understanding of kinetic
processes in a turbulent regime, where linear Vlasov theory is not sufficient
to explain the inhomogeneous plasma dynamics operating near non-Gaussian
structures.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
Pressure enhancement associated with meridional flow in high-speed solar wind: possible evidence for an interplanetary magnetic flux rope
Emission heights of coronal bright points on Fe XII radiance map
We study the emission heights of the coronal bright points (BPs) above the
photosphere in the bipolar magnetic loops that are apparently associated with
them. As BPs are seen in projection against the disk their true emission
heights are unknown. The correlation of the BP locations on the Fe XII radiance
map from EIT with the magnetic field features (in particular neutral lines) was
investigated in detail. The coronal magnetic field was determined by an
extrapolation of the photospheric field to different altitudes above the disk.
It was found that most BPs sit on or near a photospheric neutral line, but that
the emission occurs at a height of about 5 Mm. Some BPs, while being seen in
projection, still seem to coincide with neutral lines, although their emission
takes place at heights of more than 10 Mm. Such coincidences almost disappear
for emissions above 20 Mm. We also projected the upper segments of the 3-D
magnetic field lines above different heights, respectively, on to the x-y
plane. The shape of each BP was compared with the respective field-line segment
nearby. This comparison suggests that most coronal BPs are actually located on
the top of their associated magnetic loops. Finally, we calculated for each
selected BP region the correlation coefficient between the Fe XII intensity
enhancement and the horizontal component of the extrapolated magnetic field
vector at the same x-y position in planes of different heights, respectively.
We found that for almost all the BP regions we studied the correlation
coefficient, with increasing height, increases to a maximal value and then
decreases again. The height corresponding to this maximum was defined as the
correlation height, which for most bright points was found to range below 20
Mm.Comment: 7 pages, 4 figures, 1 tabl
Magnetic Evolution and Temperature Variation in a Coronal Hole
We have explored the magnetic flux evolution and temperature variation in a
coronal-hole region, using Big Bear Solar Observatory (BBSO) deep magnetograms
and {\it SOHO}/EIT images observed from 2005 October 10 to 14. For comparison,
we also investigated a neighboring quiet region of the Sun. The coronal hole
evolved from its mature stage to its disappearance during the observing period.
We have obtained the following results: (1) When the coronal hole was well
developed on October 10, about 60 % of the magnetic flux was positive. The EUV
brightness was 420 counts pixel, and the coronal temperature, estimated
from the line ratio of the EIT 195 {\AA} and 171 {\AA} images, was 1.07 MK. (2)
On October 14, when the coronal hole had almost disappeared, 51 % of the
magnetic flux was positive, the EUV radiance was 530 counts pixel, and
the temperature was 1.10 MK. (3) In the neighboring quiet region, the fraction
of positive flux varied between 0.49 and 0.47. The EUV brightness displayed an
irregular variation, with a mean value of 870 counts pixel. The
temperature was almost constant at 1.11 MK during the five-day observation. Our
results demonstrate that in a coronal hole less imbalance of the magnetic flux
in opposite polarities leads to stronger EUV brightness and higher coronal
temperatures
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