X-Ray Spectroscopy of Stars

(abridged) Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Low-mass stars on the cooler part of the main sequence and their pre-main sequence predecessors define the dominant stellar population in the galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense, of X-ray spectra from the solar corona. X-ray emission from cool stars is indeed ascribed to magnetically trapped hot gas analogous to the solar coronal plasma. Coronal structure, its thermal stratification and geometric extent can be interpreted based on various spectral diagnostics. New features have been identified in pre-main sequence stars; some of these may be related to accretion shocks on the stellar surface, fluorescence on circumstellar disks due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot stars clearly dominate the interaction with the galactic interstellar medium: they are the main sources of ionizing radiation, mechanical energy and chemical enrichment in galaxies. High-energy emission permits to probe some of the most important processes at work in these stars, and put constraints on their most peculiar feature: the stellar wind. Here, we review recent advances in our understanding of cool and hot stars through the study of X-ray spectra, in particular high-resolution spectra now available from XMM-Newton and Chandra. We address issues related to coronal structure, flares, the composition of coronal plasma, X-ray production in accretion streams and outflows, X-rays from single OB-type stars, massive binaries, magnetic hot objects and evolved WR stars.Comment: accepted for Astron. Astrophys. Rev., 98 journal pages, 30 figures (partly multiple); some corrections made after proof stag

Treatment of chronic anterior shoulder dislocation by open reduction and simultaneous Bankart lesion repair

<p>Abstract</p> <p>Background</p> <p>Untreated chronic shoulder dislocation eventually leads to functional disability and pain. Open reduction with different fixation methods have been introduced for most chronic shoulder dislocation. We hypothesized that open reduction and simultaneous Bankart lesion repair in chronic anterior shoulder dislocation obviates the need for joint fixation and leads to better results than previously reported methods.</p> <p>Methods</p> <p>Eight patients with chronic anterior dislocation of shoulder underwent open reduction and capsulolabral complex repair after an average delay of 10 weeks from injury. Early motion was allowed the day after surgery in the safe position and the clinical and radiographic results were analyzed at an average follow-up of one year.</p> <p>Results</p> <p>The average Rowe and Zarin's score was 86 points. Four out of eight shoulders were graded as excellent, three as good and one as fair (Rowe and Zarins system). All patients were able to perform their daily activities and they had either mild or no pain. Anterior active forward flexion loss averaged 18 degrees, external active rotation loss averaged 17.5 degrees and internal active rotation loss averaged 3 vertebral body levels. Mild degenerative joint changes were noted in one patient.</p> <p>Conclusion</p> <p>The results show that the overall prognosis for this method of operation is more favorable than the previously reported methods and we recommend concomitant open reduction and capsulolabral complex repair for the treatment of old anterior shoulder dislocation.</p> <p>Level of Evidence</p> <p>Therapeutic study, Level IV (case series [no, or historical, control group])</p

Large-scale fabrication of highly ordered sub-20 nm noble metal nanoparticles on silica substrates without metallic adhesion layers

Periodic noble metal nanoparticles offer a wide spectrum of applications including chemical and biological sensors, optical devices, and model catalysts due to their extraordinary properties. For sensing purposes and catalytic studies, substrates made of glass or fused-silica are normally required as supports, without the use of metallic adhesion layers. However, precise patterning of such uniform arrays of silica-supported noble metal nanoparticles, especially at sub-100 nm in diameter, is challenging without adhesion layers. In this paper, we report a robust method to large-scale fabricate highly ordered sub-20 nm noble metal nanoparticles, i.e., gold and platinum, supported on silica substrates without adhesion layers, combining displacement Talbot lithography (DTL) with dry-etching techniques. Periodic photoresist nanocolumns at diameters of ~110 nm are patterned on metal-coated oxidized silicon wafers using DTL, and subsequently transferred at a 1:1 ratio into anti-reflection layer coating (BARC) nanocolumns with the formation of nano-sharp tips, using nitrogen plasma etching. These BARC nanocolumns are then used as a mask for etching the deposited metal layer using inclined argon ion-beam etching. We find that increasing the etching time results in cone-shaped silica features with metal nanoparticles on the tips at diameters ranging from 100 nm to sub-30 nm, over large areas of 3×3 cm2. Moreover, subsequent annealing these sub-30 nm metal nanoparticle arrays at high-temperature results in sub-20 nm metal nanoparticle arrays with ~1010 uniform particles