1,721,054 research outputs found
Two-dimensional photometric analysis of emission lines in quiescent prominences
No full textEmission lines from quiescent prominences were observed simultaneously through narrow-band interference filters, thus integrating the total line intensities without the use of a spectrograph. Simultaneous exposures (50 ms) on three electronically connected CCD cameras at the 70 cm VTT on Tenerife assured almost identical influence of the Earth's atmosphere and a spatial resolution of less than or equal to 1 arc sec. The resulting spatially high-resolution two-dimensional images in H beta, H alpha, and Ca(+)8542, calibrated in units of the disk-center intensities, allow a two-dimensional mapping of emission ratios yielding relevant physical parameters. The emission relation between H alpha and H beta, which depends on the total optical thickness, confirms earlier photometric results from spectra, however, with a large sample of data points from six prominences. It demonstrates the saturation effects towards brighter prominences or prominence locations. The relation between Ca(+)8542 and H beta, which depends on the gas pressure, is found to vary between different prominences but is nearly constant within one prominence. Its mean spatial variation of less than or equal to 30% within one prominence may be interpreted in terms of a magnetic field with variations of less than or equal to5%. The brightness distribution in most prominences is not smooth but indicates preferred values, which are interpreted as superpositions of several fine structures
Spatial offsets between lines and continuum in limb faculae
No full textHigh-spatial-resolution spectra of limb faculae show spatial displacements of line cores relative to the adjacent continuum at cos theta <0.35, confirming results from earlier photographic analyses. The observed displacements are geometric measures which probe the upper atmospheric layers of fluxtubes forming facular grains. We selected spectra with highest contrast and smallest width of the facular continuum streaks, in order to avoid clustered structures. The spatial displacements of Stokes-Q and -V maxima were also measured: we find Q-signals spatially located near the continuum, as is expected from their origin in line wings; V-signals - which should give evidence for the existence of horizontal fields - are not found, except for one case of a `hidden' pore
Solar prominences with Na and Mg emissions and centrally reversed Balmer lines
No full textWe observed bright solar limb prominences with significant emission
of NaD2 and Mgb2 simultaneously with the Hα, Hβ, HeD3,
He+4685, and the Hesingl 5015 Å lines, using the THEMIS telescope
on Tenerife. We find that most prominences with significant NaD2 and Mgb2
emissions show pronounced centrally reversed Hα profiles, and occasionally
even of Hβ; the strongest emissions reach integrated intensities
[ erg/(cm2 s str)] . The centrally reversed
profiles are well reproduced by semi-infinite models. The source function
reaches S [ erg/(cm2 s str Å)] corresponding
to an excitation temperature K; here, the
optically thickness of Hα amounts . The
line widths of the NaD2, Mgb2, and HeD3 profiles yield kinetic
temperatures K and non-thermal broadening
km s-1
Spectroscopy of solar prominences from space and ground
No full textTwo quiescent solar prominences were observed in July 2000 from SUMER aboard SOHO and from the two German solar telescopes at Tenerife. Two-dimensional images taken at the VTT simultaneously in the spectral lines Hbeta at 4862 Angstrom and Ca II at 8542 Angstrom show no significant spatial variation of their pressure-sensitive emission ratio. Slit spectra of the Ca II 8542 Angstrom and He I 10830 Angstrom lines obtained at the Gregory-Coude telescope yield 8000 K < T-kin < 9000 K and 3 km/s < Vn-th < 8 km/s. Among the various spectral ranges observed with SUMER, we first investigate the Lyman emission lines, which were fitted by Gaussians yielding reliable spectral radiances and line widths for the series members 5 < k < 18. A determination of the level population gives for the lower series members a Boltzmann temperature of 60 000 K, the higher members being over-populated. This temperature indicates an origin of the Lyman lines from hot surroundings of the cool prominence body seen in the ground-based data; this also holds for the 'hotter' SUMER lines
Spectroscopy of solar prominences simultaneously from space and ground
No full textWe present a comprehensive set of spectral data from two quiescent solar prominences observed in parallel from space and ground: with the VTT, simultaneous two-dimensional imaging of Hbeta 4862 Angstrom and Ca II 8542 Angstrom yields a constant ratio, indicating small spatial pressure variations over the prominence. With the Gregory, simultaneous spectra of Ca II 8542 Angstrom and He I 10830 Angstrom were taken, their widths yielding 8000 K 6 x 10(4) K, the levels k > 8 appearing more and more overpopulated. The larger widths of the Lyman lines require high non-thermal broadening close to that of 'hot' EUV lines. In contrast, the He II emission is more related to the 'cool' lines
On the origin of the Balmer and Lyman emission lines in solar prominences
No full textAims. We show how the observed hydrogen Balmer and Lyman emission lines
constrain the modeling of quiescent solar prominences.
Methods. We compare space observations of Lyman lines with ground-based
observations of Balmer lines for quiescent solar prominences
of comparable brightness defined by their Hβ emission.
Results. The effective number densities of hydrogen atoms emitting from
the same upper level u deduced from the corresponding emerging
Lyman and Balmer line emissions show large differences that diminish
with increasing level number and converge at the highest level numbers.
Hydrogen atoms excited in contribute 250 times less, and
those in still contribute 65 times less to the Lyman than
to the corresponding Balmer emission, supporting the idea of distinct
spatial origin of the emissions of both series. This is also
indicated by the line widths. The high optical thickness of all
Lyman members allows the brightness temperature Tb to be estimated
from the spectral radiance at line center, where Tb is found to
be largely independent of the upper level number, in contrast to
the (known) behavior of the Balmer lines
Die Robustheit der Sehleistung während der frühen Neurodegeneration des visuellen Systems in der Primär Progredienten Multiplen Sklerose
No full textWir führten eine Beobachtungsstudie mit 81 Patienten mit Primär Progredienter Multipler Sklerose (PPMS) durch, welche longitudinale Sehleistungsparameter, Messungen mithilfe der optischen Kohärenztomographie (OCT), Magnetresonanztomographie (MRT) und die Bestimmung des Serum Neurofilament Light Chains (sNfL) beinhaltete. Darüber hinaus erfolgte ein querschnittlicher Vergleich mit zwei Kohorten jeweils 52 gesunder Probanden. Ziel der Studie war es, Prädiktoren des klinischen Verlaufs der PPMS zu identifizieren. Diskutiert werden dafür die Atrophie retinaler Nervenschichten und die Konzentration des Proteins sNfL.
Im querschnittlichen Vergleich mit gesunden Probanden hatten PPMS Patienten verminderte Parameter der Kontrastsensitivitätsfunktion, eine dünnere Retinale Nervenfaserschicht (RNFL) und Ganglienzell-/Innere Plexiforme Schicht (GCIPL) sowie ein erhöhtes sNfL. Auch mit zunehmender Krankheitsdauer nahmen die RNFL, GCIPL und das totale Makulavolumen ab. Die Atrophie der retinalen Nervenschichten beeinflusste die Sehleistungsparameter in einem nicht-linearen Zusammenhang. Die Sehleitung blieb lange bis zu einem bestimmten Wendepunkt der retinalen Atrophie weitestgehend stabil, nach welchem ein deutlich steilerer Abstieg der Sehfunktion zu verzeichnen war. Die Fläche unter der logarithmierten Kontrastsensitivitätsfunktion zeigte von allen gemessenen Sehleistungsparametern den steilsten Abstieg und scheint somit ein sensitiverer Parameter für die Neurodegeneration bei PPMS zu sein.Our observational study with 81 primary progressive multiple sclerosis (PPMS) patients includes a longitudinal assessment of the visual function, measurements performed with the optical coherence tomography (OCT), magnetic resonance imaging (MRI) and the evaluation of the serum neurofilament light chain protein (sNfL). Additionally, we performed a cross sectional comparison with two groups of healthy controls, each n=52. The purpose of the study was to identify predictors for clinical worsening of PPMS. As such potential predictors, we discuss the retinal layer atrophy and the concentration of sNfL.
In the cross sectional comparison with healthy controls, PPMS patients showed a lower contrast sensitivity function, thinner retinal nerve fiber layer (RNFL) and ganglion cell/inner plexiform layer (GCIPL) and total macula volume. There was a non-linear association between the visual function and retinal layer atrophy. Visual funcion was largely stable until an inflection point after which a notably steeper decline was observed. The area under the logarithmized contrast sensitivity function had the steepest decline of all measured visual function parameters and therefore, seems to be a more sensitive parameter for neurogedeneration in PPMS
Non-thermal line-broadening in solar prominences
No full textAims. We show that the line broadening in quiescent solar prominences is mainly due to non-thermal velocities.
Methods. We have simultaneously observed a wide range of optically thin lines in quiescent prominences, selected for bright and narrow Mg b emission without line satellites from macro-shifts.
Results. We find a ratio of reduced widths, ΔλD/λ0, of Hγ and Hδ of 1.05 ± 0.03, which can hardly be attributed to saturation, since both are optically thin for the prominences observed: τγ ≤ 0.3, τδ ≤ 0.15. We confirm the ratio of reduced widths of He 4772 (triplet) and He 5015 (singlet) of 1.1 ± 0.05 at higher significance and detect a width ratio of Mg b2 and Mg 4571 (both from the triplet system) of 1.3 ± 0.1.
Conclusions. The discrepant widths of lines from different atoms, and even from the same atom, cannot be represented by a unique pair [Tkin; Vnth]. Values of Tkin deduced from observed line radiances using models indicate low temperatures down to Tkin ≈ 5000 K. Non-thermal velocities, related to different physical states of the respective emitting prominence region, seem to be the most important line broadening mechanism
Feasibility of a smartphone app to enhance physical activity in progressive MS: a pilot randomized controlled pilot trial over three months
No full textBackground: People with chronic progressive multiple sclerosis (CPMS) have limited options in medical treatment. Enhancing physical activity (PA) might promote neuroregeneration in multiple sclerosis (MS) and positively influence disability, thus providing an alternative to medical treatment. Previous studies indicate that evidence-based patient information (EBPI) is essential for inducing behavioral change, e.g. enhancing PA. Objective: To investigate feasibility of a smartphone app providing EBPI about the benefit of PA and a simple activity feedback to enhance PA in people with CPMS in a pilot randomized controlled trial over 3 months. Methods: Thirty-eight people with CPMS (mean age 51 years, median Expanded Disability Status Scale 4.0) were 1:1 randomized into either a control group (n = 20) or an intervention group (n = 18). The intervention group received access to a multimedia EBPI app including activity feedback, texts, figures and videos. In the control group, participants received a leaflet with unspecific information about exercising in general. The EPBI itself was designed based on a systematic review. At baseline and after 3 months, all participants underwent clinical performance tests, filled in questionnaires and received an activity monitor (Actigraph) for 7 days. The primary endpoint was the rate of responders defined as participants with a 20% increase of physical acitivity (time of moderate or vigiorous PA—MVPA) or 20% increase of the number of steps, both assessed with the activity monitor. As secondary endpoints, we compared accelerometry, performance and questionnaires adjusted for baseline measurments between the groups (ANCOVA). Moreover, we used questionnaires to compare knowledge about exercise (activity requiring physical effort, carried out to improve or improve health and fitness) in MS, usability of the app in general and motivation towards a more active lifestyle after 3 months in both groups.
Results: The groups showed significant differences in disease duration and PA according to the Godin–Leisure Time Exercise Questionnaire at baseline. After 3 months, we detected no difference in the rate of responders, which was an overall 22%. However, MVPA significantly increased in both groups (p < 0.001) and the intervention group tended to have a higher motivation towards a more active lifestyle (Cohens D = 0.7, p = 0.09) as measured by the questionnaire. Reponses also showed, that participants appreciated the app but claimed a lack of interactivity as a shortcoming. Conclusion: Just providing information in a multimedia smartphone app did not enhance physical activitiy more than a simple leaflet in this small pilot trial in CPMS. However, the group of app users tended to have a higher motivation towards a more active lifestyle. Overall, the concept of a smartphone app to support an active lifestyle in MS is highly appreciated by participants
Smartphone Accelerometry: A Smart and Reliable Measurement of Real-Life Physical Activity in Multiple Sclerosis and Healthy Individuals
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