38 research outputs found
Space-Time Distribution of G-Band and Ca II H-Line Intensity Oscillations in Hinode/SOT-FG Observations
We study the space-time distributions of intensity fluctuations in 2 - 3 hour
sequences of multi-spectral, high-resolution, high-cadence broad-band
filtergram images (BFI) made by the SOT-FG system aboard the Hinode spacecraft.
In the frequency range 5.5 < f < 8.0 mHz both G-band and Ca II H-line
oscillations are suppressed in the presence of magnetic fields, but the
suppression disappears for f > 10 mHz. By looking at G-band frequencies above
10 mHz we find that the oscillatory power, both at these frequencies and at
lower frequencies too, lies in a mesh pattern with cell scale 2 - 3 Mm, clearly
larger than normal granulation, and with correlation times on the order of
hours. The mesh pattern lies in the dark lanes between stable cells found in
time-integrated G-band intensity images. It also underlies part of the bright
pattern in time-integrated H-line emission. This discovery may reflect
dynamical constraints on the sizes of rising granular convection cells together
with the turbulence created in strong intercellular downflows.Comment: 24 pages, 15 figure
The continuum intensity as a function of magnetic field I. Active region and quiet Sun magnetic elements
Small-scale magnetic fields are major contributors to the solar irradiance
variations. Hence, the continuum intensity contrast of magnetic elements in the
quiet Sun (QS) network and in active region (AR) plage is an essential quantity
that needs to be measured reliably. By using Hinode/SP disk center data at a
constant, high spatial resolution, we aim at updating results of earlier
ground-based studies of contrast vs. magnetogram signal, and to look for
systematic differences between AR plages and QS network. The field strength,
filling factor and inclination of the field was retrieved by Milne-Eddington
inversion (VFISV). As in earlier studies, we performed a pixel-by-pixel study
of 630.2 nm continuum contrast vs. apparent (i.e. averaged over a pixel)
longitudinal magnetic field over large fields of view in ARs and in the QS. The
contrast of magnetic elements reaches larger values in the QS (on average 3.7%)
than in ARs (1.3%). This could not be attributed to any systematic difference
in the chosen contrast references. At Hinode's spatial resolution, the
relationship between contrast and apparent longitudinal field strength exhibits
a peak at around 700 G in both the QS and ARs, whereas earlier lower resolution
studies only found a peak in the QS and a monotonous decrease in ARs. We
attribute this discrepancy both to our careful removal of the pores and their
close surroundings affected by the telescope diffraction, as well as to the
enhanced spatial resolution and very low scattered light of the Hinode Solar
Optical Telescope. According to our inversions, the magnetic elements producing
the peak of the contrast curves have similar properties (field strength,
inclination, filling factor) in ARs and in the QS, so that the larger
brightness of magnetic elements in the QS remains unexplained.Comment: 8 figures, 14 page
Cerebral blood flow and behavioural effects of caffeine in habitual and non-habitual consumers of caffeine: A near infrared spectroscopy study
Caffeine has been shown to modulate cerebral blood flow, with little evidence of tolerance to these effects following habitual use. However, previous studies have focused on caffeine levels much higher than those found in dietary servings and have compared high caffeine consumers with low consumers rather than 'non-consumers'. The current placebo-controlled double-blind, balanced-crossover study employed near infrared spectroscopy to monitor pre-frontal cerebral-haemodynamics at rest and during completion of tasks that activate the pre-frontal cortex. Twenty healthy young habitual and non-habitual consumers of caffeine received 75mg caffeine or placebo. Caffeine significantly decreased cerebral blood flow but this was subject to a significant interaction with consumption status, with no significant effect being shown in habitual consumers and an exaggerated effect in non-habitual consumers. These findings suggest that caffeine, at levels typically found in a single dietary serving, is able to modulate cerebral blood flow but these effects are subject to tolerance
Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results
The chromosphere is a thin layer of the solar atmosphere that bridges the
relatively cool photosphere and the intensely heated transition region and
corona. Compressible and incompressible waves propagating through the
chromosphere can supply significant amounts of energy to the interface region
and corona. In recent years an abundance of high-resolution observations from
state-of-the-art facilities have provided new and exciting ways of
disentangling the characteristics of oscillatory phenomena propagating through
the dynamic chromosphere. Coupled with rapid advancements in
magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly
investigate the role waves play in supplying energy to sustain chromospheric
and coronal heating. Here, we review the recent progress made in
characterising, categorising and interpreting oscillations manifesting in the
solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review
Effect of cyclooxygenase-2 inhibition with rofecoxib on endothelial dysfunction and inflammatory markers in patients with coronary artery disease
AbstractObjectivesThe aim of this study was to determine whether selective cyclooxygenase-2 (COX-2) inhibition with rofecoxib can modulate endothelial dysfunction and levels of circulating inflammatory markers in patients with established coronary artery disease (CAD).BackgroundExpression of COX-2 is upregulated in atherosclerosis. Thus, it has been hypothesized that COX-2 may contribute to atherogenesis by producing eicosanoids, which mediate vascular inflammation and endothelial dysfunction.MethodsIn a randomized, double-blind, placebo-controlled, parallel-design trial, we studied the vascular effects of rofecoxib on brachial artery vasoreactivity and inflammatory markers in 60 patients with angiographically proven CAD who were taking concomitant low-dose aspirin. Patients were randomly assigned to receive either rofecoxib (25 mg/day; n = 30) or placebo (n = 30) for eight weeks. Brachial artery endothelium-dependent flow-mediated dilation (FMD), endothelium-independent nitroglycerin-mediated dilation (NMD), and inflammatory markers (i.e., high-sensitivity C-reactive protein [CRP], soluble intercellular adhesion molecule-1 [sICAM-1], and soluble interleukin-6 receptor [sIL-6r]) were measured at baseline and after eight-week follow-up.ResultsBaseline clinical characteristics were similar in the two groups. After eight weeks of treatment, FMD did not significantly change in either the rofecoxib or placebo group (4.0 ± 3.0% to 4.0 ± 3.8% vs. 2.7 ± 2.7% to 3.1 ± 2.7%, respectively; p = 0.6 by two-way analysis of variance). Similarly, NMD remained unchanged in both groups. Levels of CRP, sICAM-1, and sIL-6r were not significantly altered in either the rofecoxib or placebo group.ConclusionsThe addition of selective COX-2 inhibition with rofecoxib did not appear to have any favorable or adverse effects on endothelial dysfunction or vascular inflammation in patients with CAD using concomitant low-dose aspirin