247 research outputs found
In situ spectroscopy of the solar corona
Context. Future spacecraft missions, such as the proposed Solar Probe mission, will venture close to the Sun, allowing spectrometers measuring emission from heavy ions or neutrals in the solar wind to have radial lines of sight (LOS) pointing away from the Sun, or indeed in any direction other than sunwards.
Aims. We show that a radial LOS gives excellent solar wind diagnostics, with tight constraints on ion density, outflow velocity, and effective temperature parallel to the coronal magnetic field. In addition, we present the concept that a spectrometer onboard a spacecraft reaching the solar corona can yield measurements somewhat similar to an in situ sampling instrument, in that the 3D velocity distribution and density of the emitting ions can be measured.
Methods. The well-studied OâVI doublet at 1031.96 and 1037.6Â Ă
âand the HâLy-αâline at 1215.67 Ă
âare chosen as examples. Solar wind parameters obtained from a 2D three-fluid magnetohydrodynamic (MHD) model, and formulations for collisional and radiative emission along a radial LOS, are used to calculate spectral line profiles for these lines at various heights within a streamer and coronal hole.
Results. For OâVI, the collisional line profiles directly measure the ion velocity distribution in the radial direction, with the general Doppler shift of the profiles related to the bulk ion outflow velocity and the width of the line related to the effective ion temperature parallel to the magnetic field. An obvious skew in the collisional profiles is seen in regions with a high gradient in outflow velocity and/or temperature. The resonant (or radiative) line profiles behave very differently from those currently observed in 90° scattering. They are more closely related to the profile and distribution of the exciting chromospheric spectrum: the lines are narrow and are centered at wavelengths mirrored around the rest wavelength of the ion emission, allowing easy separation of the collisional and radiative components. Despite the Ly-αâline being much more intense than the OâVI lines, the large width and high intensity of the Ly-αâradiative component in comparison to the collisional component is such that these two components cannot be separated. The Ly-αâline is therefore less suitable for solar wind diagnostics.
Conclusions. The prospect of coronal in situ spectral observations, combined with simultaneous in situ sampling measurements of the solar wind and magnetic field will give unsurpassed constraints on models of solar wind heating and acceleration
Bosnian pine (Pinus heldreichii syn. Pinus leucodermis)
Technical guidelines are targeted to practical forest managers and provide summarized information on the biology and ecology of tree species, distribution ranges, importance and use, genetic knowledge, threats to genetic diversity and recommendations for long-term genetic conservation. For the full list of Technical guidelines produced, please visit http://www.euforgen.org/publications/technical_guidelines.htm
Design and Fabrication of the All-Reflecting H-Lyman alpha Coronagraph/Polarimeter
We have designed, analyzed, and are now fabricating an All-Reflecting H-Lyman alpha Coronagraph/Polarimeter for solar research. This new instrument operates in a narrow bandpass centered at lambda 1215.7 A-the neutral hydrogen Lyman alpha (Ly-alpha) line. It is shorter and faster than the telescope which produced solar Ly-alpha images as a part of the MSSTA payload that was launched on May 13, 1991. The Ly-alpha line is produced and linearly polarized in the solar corona by resonance scattering, and the presence of a magnetic field modifies this polarization according to the Hanle effect. The Lyman alpha Coronagraph/Polarimeter instrument has been designed to measure coronal magnetic fields by interpreting, via the Hanle effect, the measured linear polarization of the coronal Ly-alpha line. Ultrasmooth mirrors, polarizers, and filters are being flow-polished for this instrument from CVD silicon carbide substrates. These optical components will be coated using advanced induced transmission and absorption thin film multilayer coatings, to optimize the reflectivity and polarization properties at 1215.7 A. We describe some of the solar imaging results obtained with the MSSTA Lyman alpha coronagraph. We also discuss the optical design parameters and fabrication plans for the All-Reflecting H-Lyman alpha Coronagraph/Polarimeter
B-type natriuretic peptide levels predict extent and severity of coronary disease in non-ST elevation coronary syndromes and normal left ventricular systolic function.
BACKGROUND: B-type natriuretic peptide (BNP) has been used recently as a
biological marker in patients with coronary artery disease (CAD) with
ST-elevation, as well as without ST-elevation. BNP is able to predict systolic
dysfunction, adding new prognostic information to existing traditional markers.
However is not known if there is a relation between the quantity of BNP levels
and the severity of coronary artery disease.
METHODS: This study compared B-type natriuretic peptide (BNP) levels in patients
with stable angina (SA) and acute coronary syndromes (ACS) without ST-elevation
in relation to angiographic lesions using TIMI and Gensini Scores. We studied 282
patients with CAD without ST elevation and preserved systolic function. BNP
samples were measured in all recruited patients within 24 hours of
hospitalization.
RESULTS: BNP values were progressively increased in relation to the severity of
diagnosis: SA (52.6±49.4 pg/mL ) UA (243.3±212 pg/mL) NSTE-ACS (421.7±334 pg/mL)
(p<0.0001 and p<0.007 respectively). No statistically significant difference was
observed between patients with SA and controls (21.2±6.8 pg/mL). The analysis of
BNP levels in relation to the number of involved vessels demonstrated
significantly increased levels in patients with multivessel disease compared to
patients with 1 or 2 vessel disease (1-86.2±46.3 pg/mL; 2-127±297 pg/mL;
3-295±318 pg/mL; 4-297±347 pg/mL p<0.001 and p<0.003). Evaluation of BNP using
Gensini Score showed a strong relation between BNP and coronary disease extension
(r=0.38 p<0.0001).This trend was maintained in all CAD groups (SA=r 0.54; UA
r=0.36 NSTE-ACS r=0.28).
CONCLUSIONS: Circulating BNP levels appear elevated in ACS with diffuse coronary
involvement, even in the absence of systolic dysfunction. BNP is also associated
with multi-vessel disease and the extension of coronary disease
Narrow genetic base in forest restoration with holm oak (Quercus ilex L.) in Sicily
In order to empirically assess the effect of actual seed sampling strategy on
genetic diversity of holm oak (Quercus ilex) forestations in Sicily, we have
analysed the genetic composition of two seedling lots (nursery stock and
plantation) and their known natural seed origin stand by means of six nuclear
microsatellite loci. Significant reduction in genetic diversity and significant
difference in genetic composition of the seedling lots compared to the seed
origin stand were detected. The female and the total effective number of
parents were quantified by means of maternity assignment of seedlings and
temporal changes in allele frequencies. Extremely low effective maternity
numbers were estimated (Nfe 2-4) and estimates accounting for both
seed and pollen donors gave also low values (Ne 35-50). These values
can be explained by an inappropriate forestry seed harvest strategy limited to
a small number of spatially close trees
Origins of the slow and the ubiquitous fast solar wind
We present in this Letter the first coordinated radio occultation
measurements and ultraviolet observations of the inner corona below 5.5 Rs,
obtained during the Galileo solar conjunction in January 1997, to establish the
origin of the slow solar wind. Limits on the flow speed are derived from the
Doppler dimming of the resonantly scattered componentof the oxygen 1032 A and
1037 A lines as measured with the UltraViolet Coronagraph Spectrometer (UVCS)
on the Solar and Heliospheric Observatory (SOHO). White light images of the
corona from the Large Angle Spectroscopic Coronagraph (LASCO) on SOHO taken
simultaneously are used to place the Doppler radio scintillation and
ultraviolet measurements in the context ofcoronal structures. These combined
observations provide the first direct confirmation of the view recently
proposed by Woo and Martin (1997) that the slow solar wind is associated with
the axes, also known as stalks, of streamers. Furthermore, the ultraviolet
observations also show how the fast solar wind is ubiquitous in the inner
corona, and that a velocity shear between the fast and slow solar wind develops
along the streamer stalks.Comment: 15 pages, LaTex, 6 jpg figures, accepted Aug. 28, 1997 for
publication in the ApJ Letter
LEMUR: Large European Module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission
Understanding the solar outer atmosphere requires concerted, simultaneous
solar observations from the visible to the vacuum ultraviolet (VUV) and soft
X-rays, at high spatial resolution (between 0.1" and 0.3"), at high temporal
resolution (on the order of 10 s, i.e., the time scale of chromospheric
dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the
chromosphere to the flaring corona), and the capability of measuring magnetic
fields through spectropolarimetry at visible and near-infrared wavelengths.
Simultaneous spectroscopic measurements sampling the entire temperature range
are particularly important.
These requirements are fulfilled by the Japanese Solar-C mission (Plan B),
composed of a spacecraft in a geosynchronous orbit with a payload providing a
significant improvement of imaging and spectropolarimetric capabilities in the
UV, visible, and near-infrared with respect to what is available today and
foreseen in the near future.
The Large European Module for solar Ultraviolet Research (LEMUR), described
in this paper, is a large VUV telescope feeding a scientific payload of
high-resolution imaging spectrographs and cameras. LEMUR consists of two major
components: a VUV solar telescope with a 30 cm diameter mirror and a focal
length of 3.6 m, and a focal-plane package composed of VUV spectrometers
covering six carefully chosen wavelength ranges between 17 and 127 nm. The
LEMUR slit covers 280" on the Sun with 0.14" per pixel sampling. In addition,
LEMUR is capable of measuring mass flows velocities (line shifts) down to 2
km/s or better.
LEMUR has been proposed to ESA as the European contribution to the Solar C
mission.Comment: 35 pages, 14 figures. To appear on Experimental Astronom
Varespladib and cardiovascular events in patients with an acute coronary syndrome: the VISTA-16 randomized clinical trial
IMPORTANCE: Secretory phospholipase A2(sPLA2) generates bioactive phospholipid products implicated in atherosclerosis. The sPLA2inhibitor varespladib has favorable effects on lipid and inflammatory markers; however, its effect on cardiovascular outcomes is unknown. OBJECTIVE: To determine the effects of sPLA2inhibition with varespladib on cardiovascular outcomes. DESIGN, SETTING, AND PARTICIPANTS: A double-blind, randomized, multicenter trial at 362 academic and community hospitals in Europe, Australia, New Zealand, India, and North America of 5145 patients randomized within 96 hours of presentation of an acute coronary syndrome (ACS) to either varespladib (n = 2572) or placebo (n = 2573) with enrollment between June 1, 2010, and March 7, 2012 (study termination on March 9, 2012). INTERVENTIONS: Participants were randomized to receive varespladib (500 mg) or placebo daily for 16 weeks, in addition to atorvastatin and other established therapies. MAIN OUTCOMES AND MEASURES: The primary efficacy measurewas a composite of cardiovascular mortality, nonfatal myocardial infarction (MI), nonfatal stroke, or unstable angina with evidence of ischemia requiring hospitalization at 16 weeks. Six-month survival status was also evaluated. RESULTS: At a prespecified interim analysis, including 212 primary end point events, the independent data and safety monitoring board recommended termination of the trial for futility and possible harm. The primary end point occurred in 136 patients (6.1%) treated with varespladib compared with 109 patients (5.1%) treated with placebo (hazard ratio [HR], 1.25; 95%CI, 0.97-1.61; log-rank P = .08). Varespladib was associated with a greater risk of MI (78 [3.4%] vs 47 [2.2%]; HR, 1.66; 95%CI, 1.16-2.39; log-rank P = .005). The composite secondary end point of cardiovascular mortality, MI, and stroke was observed in 107 patients (4.6%) in the varespladib group and 79 patients (3.8%) in the placebo group (HR, 1.36; 95% CI, 1.02-1.82; P = .04). CONCLUSIONS AND RELEVANCE: In patients with recent ACS, varespladib did not reduce the risk of recurrent cardiovascular events and significantly increased the risk of MI. The sPLA2inhibition with varespladib may be harmful and is not a useful strategy to reduce adverse cardiovascular outcomes after ACS. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01130246. Copyright 2014 American Medical Association. All rights reserved
- âŠ