Line intensity enhancements in stellar coronal X-ray spectra due to opacity effects

Context. The I(15.01 Å)/I(16.78 Å) emission line intensity ratio in Fe xvii has been reported to deviate from its theoretical value
in solar and stellar X-ray spectra. This is attributed to opacity in the 15.01 Å line, leading to a reduction in its intensity, and was
interpreted in terms of a geometry in which the emitters and absorbers are spatially distinct.
Aims. We study the I(15.01 Å)/I(16.78 Å) intensity ratio for the active cool dwarf EV Lac, in both flare and quiescent spectra.
Methods. The observations were obtained with the Reflection Grating Spectrometer on the XMM-Newton satellite. The emission
measure distribution versus temperature reconstruction technique is used for our analysis.
Results. We find that the 15.01 Å line exhibits a significant enhancement in intensity over the optically thin value. To our knowledge,
this is the first time that such an enhancement has been detected on such a sound statistical basis. We interpret this enhancement
in terms of a geometry in which the emitters and absorbers are not spatially distinct, and where the geometry is such that resonant
pumping of the upper level has a greater effect on the observed line intensity than resonant absorption in the line-of-sight.

Early alterations in serum creatine kinase and total cholesterol following high intensity eccentric muscle actions

Aim. The purpose of this experiment was to assess the levels of muscle soreness, serum total cholesterol (TC) and creatine kinase (CK) in the first 48 hours following fatiguing eccentric exercise performed with the triceps brachii.

An experiment for two-color photoionization using high intensity extreme-UNT free electron and near-IR laser pulses

We describe an experimental system designed for single-shot photoelectron spectroscopy on free atoms and molecules at the Free Electron Laser in Hamburg (FLASH at DESY). The combination of the extreme ultra-violet (EUV) Free Electron Laser and a temporally synchronized optical fs laser (Ti:Sapphire) enables a variety of two-color pump-probe experiments. The spectral, temporal and spatial characteristics of both the EUV FEL and the optical laser pulses, the experimental procedure to control their overlap as well as the performance of an electron spectrometer used to obtain single-shot photoelectron spectra are discussed. As an illustration of the capabilities of this set-up, some results on two-photon two-color ionization of rare gases are presented. (c) 2007 Elsevier B.V. All rights reserved.

Where there is smoke, there is (the potential for) fire: soft indicators of research and policy impact

There is a growing literature examining the impact of research on informing policy, and of research and policy on practice. Research and policy do not have the same types of impact on practice but can be evaluated using similar approaches. Sometimes the literature provides a platform for methodological debate but mostly it is concerned with how research can link to improvements in the process and outcomes of education, how it can promote innovative policies and practice, and how it may be successfully disseminated. Whether research-informed or research-based, policy and its implementation is often assessed on such 'hard' indicators of impact as changes in the number of students gaining five or more A to C grades in national examinations or a percentage fall in the number of exclusions in inner city schools. Such measures are necessarily crude, with large samples smoothing out errors and disguising instances of significant success or failure. Even when 'measurable' in such a fashion, however, the impact of any educational change or intervention may require a period of years to become observable. This paper considers circumstances in which short-term change may be implausible or difficult to observe. It explores how impact is currently theorized and researched and promotes the concept of 'soft' indicators of impact in circumstances in which the pursuit of conventional quantitative and qualitative evidence is rendered impractical within a reasonable cost and timeframe. Such indicators are characterized by their avowedly subjective, anecdotal and impressionistic provenance and have particular importance in the context of complex community education issues where the assessment of any impact often faces considerable problems of access. These indicators include the testimonies of those on whom the research intervention or policy focuses (for example, students, adult learners), the formative effects that are often reported (for example, by head teachers, community leaders) and media coverage. The collation and convergence of a wide variety of soft indicators (Where there is smoke …) is argued to offer a credible means of identifying subtle processes that are often neglected as evidence of potential and actual impact (… there is fire).

Interaction of High Intensity Picosecond Laser Pulses with Large Pre-formed Plasmas

The interaction of short (1-2 ps) laser pulses with solid targets at irradiances of over 1016 Wcm~2 , in the presence of a substantial prepulse has been investigated. High absorption of laser energy is found even at high angles of incidence, with evidence for a resonance absorption peak being found for S, P, and circular polarizations. It is considered that this may be a result of refraction and beam filamentation, which causes loss of distinct polarization. Measurements of hard X-ray emission (~ 100 keV) confirm a resonance absorption type peak at 45-50°, again for all three cases. Typically, 5-15% of the incident light is back-reflected by stimulated Brillouin scatter, with spatially resolved spectra showing evidence of beam hot-spots at high intensity. The possibility that filamentation and refraction of the beam can explain the lack of polarization dependence in the absorption and hard X-ray emission data is discussed.