128 research outputs found

    Impact of Stark Shifts on the Radiation Cooling of Cu-Dominated Plasmas

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    We study the impact of Stark line shifts reported recently for Cu I transitions on the radiative cooling of Cu-dominated plasmas. The observed detuning in absorption between the hot core and cold shell of the arc leads to a reduction in radiation reabsorption compared to the case where Stark line shifts are neglected. Using a modeling based on a phenomenological treatment of the Stark line shift, we show that this reduction is below 2%

    CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter

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    The production of science-ready data from major solar telescopes requires expertise beyond that of the typical observer. This is a consequence of the increasing complexity of instruments and observing sequences, which require calibrations and corrections for instrumental and seeing effects that are not only difficult to measure, but are also coupled in ways that require careful analysis in the design of the correction procedures. Modern space-based telescopes have data-processing pipelines capable of routinely producing well-characterized data products. High resolution imaging spectropolarimeters at ground-based telescopes need similar data pipelines.We present new methods for flat-fielding spectropolarimetric data acquired with telecentric Fabry-Perot instruments and a new approach for accurate camera co-alignment for image restoration. We document a procedure that forms the basis of current state-of-the-art processing of data from the CRISP imaging spectropolarimeter at the Swedish 1 m Solar Telescope (SST). By collecting, implementing, and testing a suite of computer programs, we have defined a data reduction pipeline for this instrument. This pipeline, CRISPRED, streamlines the process of making science-ready data.It is implemented and operated in IDL, with time-consuming steps delegated to C.CRISPRED will also be the basis for the data pipeline of the forthcoming CHROMIS instrument. © ESO, 201

    Investigation of Vacuum Arc Anode Temperatures of Cu-Cr and Pure Cu Contacts

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    The present contribution reports on investigations of electrode temperatures for pure Cu electrodes and Cu–Cr electrodes of different diameters exposed to vacuum arcs with sinusoidal currents of 5-15 kA and an axial magnetic field up to 180 mT. It is found that surface temperatures of pure Cu electrodes are significantly lower than for Cu–Cr electrodes of the same diameter. This must be explained by different thermal properties of both materials. Reducing the diameter of Cu–Cr electrodes it is found that surface temperatures increase, but moreover it is shown that the enthalpy stored in the electrode bulk material may effect electrode temperatures on timescales much longer than the current pulse width, particularly if there is no effective heat dissipation after current zero

    CRISP Spectropolarimetric Imaging of Penumbral Fine Structure

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    We discuss penumbral fine structure in a small part of a pore, observed with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope (SST), close to its diffraction limit of 0.16 arcsec. Milne-Eddington inversions applied to these Stokes data reveal large variations of field strength and inclination angle over dark-cored penumbral intrusions and a dark-cored light bridge. The mid-outer part of this penumbra structure shows 0.3 arcsec wide spines, separated by 1.6 arcsec (1200 km) and associated with 30 deg inclination variations. Between these spines, there are no small-scale magnetic structures that easily can be be identified with individual flux tubes. A structure with nearly 10 deg more vertical and weaker magnetic field is seen midways between two spines. This structure is co-spatial with the brightest penumbral filament, possibly indicating the location of a convective upflow from below.Comment: Accepted for publication in ApJL 17 Oct 2008. One Figure adde

    An Investigation on Bilateral Asymmetry in Electrodermal Activity

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    The Multiple Arousal Theory (Picard et al., 2016) was proposed to explain retrospective observations of bilateral differences in electrodermal activities occurring in threat-related high-stake situations. The theory proposes different cortical and subcortical structures to be involved in the processing of various facets of emotional states. Systematic investigations of this effect are still scarce. This study tested the prediction of bilateral electrodermal effects in a controlled laboratory environment where electrodermal activity (EDA) was recorded bilaterally during normal activity and two stress-tasks in 25 healthy volunteers. A visual search stress task with a performance-related staircase algorithm was used, ensuring intersubjectively comparable stress levels across individuals. After completion of the task, a sense of ownership of an attractive price was created and loss aversion introduced to create a high-stake situation. Confirmation of the theory should satisfy the hypothesis of a bilateral difference in EDA between the dominant and non-dominant hand, which is larger during high-stake stressors than during low-stake stressors. The bilateral difference was quantified and compared statistically between the two stress-tasks, revealing no significant difference between them nor any significant difference between the stress tasks and the period of normal activity. Subgroup analysis of only the participants with maximum self-rating of their desire to win the price (n = 7) revealed neither any significant difference between the two tasks nor between the stress-tasks and the period of normal activity. Although the theory was not confirmed by this study, eight cases suggestive of bilateral difference within the recordings were identified and are presented. Because the study is limited in using one of several possible operationalizations of the phenomenon, it is not possible to draw a general conclusion on the theory. Nevertheless, the study might contribute to a better understanding and encourage systematic review and hypothesis development regarding this new theory. Possible explanations and suggestions for future pathways to systematically investigate the Multiple Arousal Theory are discussed

    Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

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    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

    Risk-adapted targeted intraoperative radiotherapy versus whole-breast radiotherapy for breast cancer: 5-year results for local control and overall survival from the TARGIT-A randomised trial

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    BACKGROUND: The TARGIT-A trial compared risk-adapted radiotherapy using single-dose targeted intraoperative radiotherapy (TARGIT) versus fractionated external beam radiotherapy (EBRT) for breast cancer. We report 5-year results for local recurrence and the first analysis of overall survival. METHODS: TARGIT-A was a randomised, non-inferiority trial. Women aged 45 years and older with invasive ductal carcinoma were enrolled and randomly assigned in a 1:1 ratio to receive TARGIT or whole-breast EBRT, with blocks stratified by centre and by timing of delivery of targeted intraoperative radiotherapy: randomisation occurred either before lumpectomy (prepathology stratum, TARGIT concurrent with lumpectomy) or after lumpectomy (postpathology stratum, TARGIT given subsequently by reopening the wound). Patients in the TARGIT group received supplemental EBRT (excluding a boost) if unforeseen adverse features were detected on final pathology, thus radiotherapy was risk-adapted. The primary outcome was absolute difference in local recurrence in the conserved breast, with a prespecified non-inferiority margin of 2·5% at 5 years; prespecified analyses included outcomes as per timing of randomisation in relation to lumpectomy. Secondary outcomes included complications and mortality. This study is registered with ClinicalTrials.gov, number NCT00983684. FINDINGS: Patients were enrolled at 33 centres in 11 countries, between March 24, 2000, and June 25, 2012. 1721 patients were randomised to TARGIT and 1730 to EBRT. Supplemental EBRT after TARGIT was necessary in 15·2% [239 of 1571] of patients who received TARGIT (21·6% prepathology, 3·6% postpathology). 3451 patients had a median follow-up of 2 years and 5 months (IQR 12–52 months), 2020 of 4 years, and 1222 of 5 years. The 5-year risk for local recurrence in the conserved breast was 3·3% (95% CI 2·1–5·1) for TARGIT versus 1·3% (0·7–2·5) for EBRT (p=0·042). TARGIT concurrently with lumpectomy (prepathology, n=2298) had much the same results as EBRT: 2·1% (1·1–4·2) versus 1·1% (0·5–2·5; p=0·31). With delayed TARGIT (postpathology, n=1153) the between-group difference was larger than 2·5% (TARGIT 5·4% [3·0–9·7] vs EBRT 1·7% [0·6–4·9]; p=0·069). Overall, breast cancer mortality was much the same between groups (2·6% [1·5–4·3] for TARGIT vs 1·9% [1·1–3·2] for EBRT; p=0·56) but there were significantly fewer non-breast-cancer deaths with TARGIT (1·4% [0·8–2·5] vs 3·5% [2·3–5·2]; p=0·0086), attributable to fewer deaths from cardiovascular causes and other cancers. Overall mortality was 3·9% (2·7–5·8) for TARGIT versus 5·3% (3·9–7·3) for EBRT (p=0·099). Wound-related complications were much the same between groups but grade 3 or 4 skin complications were significantly reduced with TARGIT (four of 1720 vs 13 of 1731, p=0·029). INTERPRETATION: TARGIT concurrent with lumpectomy within a risk-adapted approach should be considered as an option for eligible patients with breast cancer carefully selected as per the TARGIT-A trial protocol, as an alternative to postoperative EBRT. FUNDING: University College London Hospitals (UCLH)/UCL Comprehensive Biomedical Research Centre, UCLH Charities, National Institute for Health Research Health Technology Assessment programme, Ninewells Cancer Campaign, National Health and Medical Research Council, and German Federal Ministry of Education and Research
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