436 research outputs found
Spectroscopic measurements of solar wind generation
Spectroscopically observable quantities are described which are sensitive to the primary plasma parameters of the solar wind's source region. The method is discussed in which those observable quantities are used as constraints in the construction of empirical models of various coronal structures. Simulated observations are used to examine the fractional contributions to observed spectral intensities from coronal structures of interest which co-exist with other coronal structures along simulated lines-of-sight. The sensitivity of spectroscopic observables to the physical parameters within each of those structures is discussed
Identification of the Coronal Sources of the Fast Solar Wind
The present spectroscopic study of the ultraviolet coronal emission in a
polar hole, detected on April 6-9, 1996 with the Ultraviolet Coronagraph
Spectrometer aboard the SOHO spacecraft, identifies the inter-plume lanes and
background coronal hole regions as the channels where the fast solar wind is
preferentially accelerated. In inter-plume lanes, at heliocentric distance 1.7
\rsun, the corona expands at a rate between 105 km/s and 150 km/s, that is,
much faster than in plumes where the outflow velocity is between 0 km/s and 65
km/s. The wind velocity is inferred from the Doppler dimming of the O VI
1032, 1037 \AA lines, within a range of values, whose lower
and upper limit corresponds to anisotropic and isotropic velocity distribution
of the oxygen coronal ions, respectively.Comment: 14 pages, 4 figures, 3 tables, Accepted by ApJ Letter
Coronal emission lines as thermometers
Coronal emission line intensities are commonly used to measure electron
temperatures using emission measure and/or line ratio methods. In the presence
of systematic errors in atomic excitation calculations and data noise, the
information on underlying temperature distributions is fundamentally limited.
Increasing the number of emission lines used does not necessarily improve the
ability to discriminate between different kinds of temperature distributions.Comment: Accepted by ApJ, November 200
The effect of temperature anisotropy on observations of Doppler dimming and pumping in the inner corona
Recent observations of the spectral line profiles and intensity ratio of the
O VI 1032 {\AA} and 1037.6 {\AA} doublet by the Ultraviolet Coronagraph
Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO), made in
coronal holes below 3.5 , provide evidence for Doppler dimming of the O VI
1037.6 {\AA} line and pumping by the chromospheric C II 1037.0182 {\AA} line.
Evidence for a significant kinetic temperature anisotropy of O ions was
also derived from these observations. We show in this Letter how the component
of the kinetic temperature in the direction perpendicular to the magnetic
field, for both isotropic and anisotropic temperature distributions, affects
both the amount of Doppler dimming and pumping. Taking this component into
account, we further show that the observation that the O VI doublet intensity
ratio is less than unity can be accounted for only if pumping by C II 1036.3367
{\AA} in addition to C II 1037.0182 {\AA} is in effect. The inclusion of the C
II 1036.3367 {\AA} pumping implies that the speed of the O ions can
reach 400 km/s around 3 which is significantly higher than the reported
UVCS values for atomic hydrogen in polar coronal holes. These results imply
that oxygen ions flow much faster than protons at that heliocentric distance.Comment: 9 pages, 3 figure
The LH/hCG Axis in Endometrial Cancer: A New Target in the Treatment of Recurrent or Metastatic Disease
Endometrial cancer (EC) is a hormone-dependent cancer that currently represents the most frequent malignancy of the female reproductive tract. The involvement of steroid hormones in EC etiology and progression has been reported. More recently, gonadotropins, and, in particular LH/hCG, are emerging as novel regulators of tumor progression. In the present review, we discuss the role of the LH/hCG axis (i.e. LH/hCG and its receptors, LH/hCG-R) in both gonadal and nongonadal tissues, in physiological and neoplastic conditions. In cancer cells, LH/hCG mainly controls cell proliferation and apoptosis. In particular, in EC LH/hCG improves cell invasiveness, through a mechanism which involves the LH/hCG-R, which in turn activate protein kinase A and modulate integrin adhesion receptors. Indeed, the LH/hCG-R mRNA is expressed in primary ECs and this expression correlates with LH/hCG-induced cell invasiveness in vitro. These results lead to hypothesize that recurrent and metastatic ECs, which express LH/hCG-R, could benefit from therapies aimed at decreasing LH levels, through Gn-RH analogues. Hence, the LH/hCG axis could represent a prognostic factor and a new therapeutic target in EC
Improved Constraints on the Preferential Heating and Acceleration of Oxygen Ions in the Extended Solar Corona
We present a detailed analysis of oxygen ion velocity distributions in the
extended solar corona, based on observations made with the Ultraviolet
Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. Polar coronal holes at
solar minimum are known to exhibit broad line widths and unusual intensity
ratios of the O VI 1032, 1037 emission line doublet. The traditional
interpretation of these features has been that oxygen ions have a strong
temperature anisotropy, with the temperature perpendicular to the magnetic
field being much larger than the temperature parallel to the field. However,
recent work by Raouafi and Solanki suggested that it may be possible to model
the observations using an isotropic velocity distribution. In this paper we
analyze an expanded data set to show that the original interpretation of an
anisotropic distribution is the only one that is fully consistent with the
observations. It is necessary to search the full range of ion plasma parameters
to determine the values with the highest probability of agreement with the UVCS
data. The derived ion outflow speeds and perpendicular kinetic temperatures are
consistent with earlier results, and there continues to be strong evidence for
preferential ion heating and acceleration with respect to hydrogen. At
heliocentric heights above 2.1 solar radii, every UVCS data point is more
consistent with an anisotropic distribution than with an isotropic
distribution. At heights above 3 solar radii, the exact probability of isotropy
depends on the electron density chosen to simulate the line-of-sight
distribution of O VI emissivity. (abridged abstract)Comment: 19 pages (emulateapj style), 13 figures, ApJ, in press (v. 679; May
20, 2008
Lipid Oxidation and Sensory Characteristics of Grass-Fed Beef: Effect of Duration of Grazing Prior to Slaughter
Beef from cattle produced from grass has a higher concentration of fatty acids considered to be beneficial to human health than beef produced from more intensive production systems and this increase in fatty acid concentration is dependant on the duration at pasture prior to slaughter (Noci et al., 2003). Improvements in the fatty acid composition of beef must not impair other quality characteristics of beef. Little information is available on the pattern of change of quality characteristics in grazing animals. The objective of this study was to determine the shelf-life and eating quality of beef from cattle produced from a standard Irish grass silage/concentrates finishing system but allowed to graze grass for different periods prior to slaughter
Signatures of Alfven waves in the polar coronal holes as seen by EIS/Hinode
Context. We diagnose the properties of the plume and interplume regions in a
polar coronal hole and the role of waves in the acceleration of the solar wind.
Aims. We attempt to detect whether Alfven waves are present in the polar
coronal holes through variations in EUV line widths. Methods. Using spectral
observations performed over a polar coronal hole region with the EIS
spectrometer on Hinode, we study the variation in the line width and electron
density as a function of height. We use the density sensitive line pairs of Fe
xii 186.88 A & 195.119 A and Fe xiii 203.82 A & 202.04 A . Results. For the
polar region, the line width data show that the nonthermal line-of-sight
velocity increases from 26 km/s at 1000 above the limb to 42 km/s some 15000
(i.e. 110,000 km) above the limb. The electron density shows a decrease from
3:3 10^9 cm^-3 to 1:9 10^8 cm^-3 over the same distance. Conclusions. These
results imply that the nonthermal velocity is inversely proportional to the
quadratic root of the electron density, in excellent agreement with what is
predicted for undamped radially propagating linear Alfven waves. Our data
provide signatures of Alfven waves in the polar coronal hole regions, which
could be important for the acceleration of the solar wind.Comment: 5 pages, 11 figures. Astronomy and Astrophysics Letters (accepted)
http://www.aanda.org/articles/aa/pdf/forth/aa12242-09.pd
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