Star clusters near and far; tracing star formation across cosmic time

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00690-x.Star clusters are fundamental units of stellar feedback and unique tracers of their host galactic properties. In this review, we will first focus on their constituents, i.e.\ detailed insight into their stellar populations and their surrounding ionised, warm, neutral, and molecular gas. We, then, move beyond the Local Group to review star cluster populations at various evolutionary stages, and in diverse galactic environmental conditions accessible in the local Universe. At high redshift, where conditions for cluster formation and evolution are more extreme, we are only able to observe the integrated light of a handful of objects that we believe will become globular clusters. We therefore discuss how numerical and analytical methods, informed by the observed properties of cluster populations in the local Universe, are used to develop sophisticated simulations potentially capable of disentangling the genetic map of galaxy formation and assembly that is carried by globular cluster populations.Peer reviewedFinal Accepted Versio

The Physics of Star Cluster Formation and Evolution

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe

Dystonia rating scales: critique and recommendations

Item does not contain fulltextMany rating scales have been applied to the evaluation of dystonia, but only few have been assessed for clinimetric properties. The Movement Disorders Society commissioned this task force to critique existing dystonia rating scales and place them in the clinical and clinimetric context. A systematic literature review was conducted to identify rating scales that have either been validated or used in dystonia. Thirty-six potential scales were identified. Eight were excluded because they did not meet review criteria, leaving 28 scales that were critiqued and rated by the task force. Seven scales were found to meet criteria to be "recommended": the Blepharospasm Disability Index is recommended for rating blepharospasm; the Cervical Dystonia Impact Scale and the Toronto Western Spasmodic Torticollis Rating Scale for rating cervical dystonia; the Craniocervical Dystonia Questionnaire for blepharospasm and cervical dystonia; the Voice Handicap Index (VHI) and the Vocal Performance Questionnaire (VPQ) for laryngeal dystonia; and the Fahn-Marsden Dystonia Rating Scale for rating generalized dystonia. Two "recommended" scales (VHI and VPQ) are generic scales validated on few patients with laryngeal dystonia, whereas the others are disease-specific scales. Twelve scales met criteria for "suggested" and 7 scales met criteria for "listed." All the scales are individually reviewed in the online information. The task force recommends 5 specific dystonia scales and suggests to further validate 2 recommended generic voice-disorder scales in dystonia. Existing scales for oromandibular, arm, and task-specific dystonia should be refined and fully assessed. Scales should be developed for body regions for which no scales are available, such as lower limbs and trunk

On the ion and electron temperature recovery after the ELM-crash at ASDEX upgrade

The access to fast measurements, i.e. Δt ≈ 100 µs, of the ions and the electrons during an entire edge localized cycle (ELM) reveals asymmetries in the recovery of the maximum edge gradients. Different magnetic fluctuations are found to correlate with the saturation of the edge ion temperature (Ti), electrons temperature (Te) and density (ne) gradients. In particular, while ∇Ti and ∇ne clamp roughly 3.0 ms after the ELM-crash together with the onset of mid-frequency (f ≲ 50 kHz) magnetic fluctuations, ∇Te recovers to the pre-ELM conditions only after 7.0 ms and saturates with the appearance of high frequency fluctuations (f ≈ 200 kHz). The effect of electron temperature gradient modes (ETGs) and of energy losses induced by ionization of neutrals are discussed as possible reasons for the delayed recovery of ∇Te. The onset and the suppression of ETGs qualitatively follow the requirements of an increased electron heat transport. However, gyro-kinetic simulations are necessary to quantify the impact of ETGs. On the other hand, the impact of the neutral ionization during the density build-up as an electron energy loss channel is measured to be small compared to the total electron energy. The dominant terms in the electron energy balance are instead the radiative power and the ion-electron heat exchange. Keywords: ELM, Ion temperature, ETG, Neutral ionization, Fast Charge Exchang

Distinct stages of radio frequency emission at the onset of pedestal collapse in KSTAR H-mode plasmas

Using a high-speed and broadband radio frequency (RF) (0.1-1 GHz) spectrum analyzer developed on the KSTAR tokamak, it is found that several distinct stages of RF emission appear at the pedestal collapse in high confinement discharges. Comparison with 2D electron cyclotron emission (ECE) images has revealed that each stage is related to the instantaneous condition at the outboard mid-plane edge. First, high-harmonic ion cyclotron emissions (ICE) are intensified with the appearance of a non-modal filamentary perturbation in the edge within several tens of microseconds before the collapse. Then, the RF emission becomes broad toward high-frequency range (<500 MHz) at the burst onset of the non-modal filament. During the pedestal collapse initiated by the filament burst, rapid chirping (1-3 mu s) appear with additional filament bursts. The strong correlation between the RF spectra and the perturbation structure provides important clues on the stability of edge-localized modes and on the ion dynamics in the plasma boundary