Gigahertz repetition rate thermionic electron gun concept

We present a novel concept for the generation of gigahertz repetition rate high brightness electron bunches. A custom design 100 kV thermionic gun provides a continuous electron beam, with the current determined by the filament size and temperature. A 1 GHz rectangular RF cavity deflects the beam across a knife-edge, creating a pulsed beam. Adding a higher harmonic mode to this cavity results in a flattened magnetic field profile which increases the duty cycle to 30%. Finally, a compression cavity induces a negative longitudinal velocity-time chirp in a bunch, initiating ballistic compression. Adding a higher harmonic mode to this cavity increases the linearity of this chirp and thus decreases the final bunch length. Charged particle simulations show that with a 0.15 mm radius LaB6 filament held at 1760 K, this method can create 279 fs, 3.0 pC electron bunches with a radial rms core emittance of 0.089 mm mrad at a repetition rate of 1 GHz.Comment: 12 pages, 12 figure

Stellar triples with chemically homogeneously evolving inner binaries

Observations suggest that massive stellar triples are common. However, their evolution is not yet fully understood. We investigate the evolution of hierarchical triples in which the stars of the inner binary experience chemically homogeneous evolution (CHE), particularly to understand the role of the tertiary star in the formation of gravitational-wave (GW) sources. We use the triple-star rapid population synthesis code tres to determine the evolution of these systems at two representative metallicities: Z = 0.005 and Z = 0.0005. About half of all triples harbouring a CHE inner binary (CHE triples) experience tertiary mass transfer (TMT) episodes, an event which is rare for classically evolving stars. In the majority of TMT episodes, the inner binary consists of two main-sequence stars (58--60 per cent) or two black holes (BHs, 24-31 per cent). Additionally, we explore the role of von Zeipel-Lidov-Kozai (ZLK) oscillations for CHE triples. ZLK oscillations can result in eccentric stellar mergers or lead to the formation of eccentric compact binaries in systems with initial outer pericentre smaller than ∼ 1200 R⊙. Approximately 24-30 per cent of CHE triples form GW sources, and in 31 per cent of these, the tertiary star plays a significant role and leads to configurations that are not predicted for isolated binaries. We conclude that the evolution of CHE binaries can be affected by a close tertiary companion, resulting in astronomical transients such as BH--BH binaries that merge via GW emission orders of magnitude faster than their isolated binary counterparts and tertiary-driven massive stellar mergers

Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics

We study the two-dimensional kinematics of the H-alpha-emitting gas in the nearby barred Scd galaxy, NGC 6946, in order to determine the pattern speed of the primary m=2 perturbation mode. The pattern speed is a crucial parameter for constraining the internal dynamics, estimating the impact velocities of the gravitational perturbation at the resonance radii, and to set up an evolutionary scenario for NGC 6946. Our data allows us to derive the best fitting kinematic position angle and the geometry of the underlying gaseous disk, which we use to derive the pattern speed using the Tremaine-Weinberg method. We find a main pattern speed Omega_p=22 km/s/kpc, but our data clearly reveal the presence of an additional pattern speed Omega_p=47 km/s/kpc in a zone within 1.25 kpc of the nucleus. Using the epicyclic approximation, we deduce the location of the resonance radii and confirm that inside the outer Inner Lindblad Resonance radius of the main oval, a primary bar has formed rotating at more than twice the outer pattern speed. We further confirm that a nuclear bar has formed inside the Inner Lindblad Resonance radius of the primary bar, coinciding with the inner Inner Lindblad Resonance radius of the large-scale m=2 mode oval.Comment: Accepted for publication in ApJ Letter

Effect of early intervention on functional outcome at school age:Follow-up and process evaluation of a randomised controlled trial in infants at risk

Item does not contain fulltextBACKGROUND: The long-term effect of early intervention in infants at risk for developmental disorders is unclear. The VIP project (n=46, originally) evaluated by means of a randomised controlled trial the effect of the family centred early intervention programme COPCA (Coping with and Caring for infants with special needs) in comparison to that of traditional infant physiotherapy (TIP). AIMS: To evaluate the effect of early intervention on functional outcome at school age. METHODS AND PROCEDURES: Parents of 40 children (median age 8.3years) participated in this follow-up study. Outcome was assessed with a standardised parental interview (Vineland Adaptive Behaviour Scale) and questionnaires (Developmental Coordination Disorder Questionnaire, Child Behaviour Checklist, Utrechtse Coping List, and questions on educational approach). Quantified video information on physiotherapeutic actions during infancy was available. OUTCOMES AND RESULTS: Child functional outcome in the two randomised groups was similar. Process evaluation revealed that some physiotherapeutic actions were associated with child mobility and parental educational approach at follow-up: e.g., training and instructing were associated with worse mobility. CONCLUSIONS AND IMPLICATIONS: Functional outcome at school age after early intervention with COPCA is similar to that after TIP. However, some specific physiotherapeutic actions, in particular the physiotherapist's approach, are associated with outcome. WHAT THIS PAPER ADDS: Early intervention is generally applied in infants at risk for developing disorders, with the aim of improving overall functional outcome. However, little is known on the long-term effect. The VIP project evaluated by means of a randomised controlled trial the effect of the family centred early intervention programme COPCA (Coping with and Caring for infants with special needs) in comparison to that of traditional infant physical therapy (TIP). Outcome at 18months corrected age was virtually similar. Process evaluation of the physiotherapy actions revealed that some characteristics of COPCA were associated with improved developmental outcome at 18months. This paper presents data on functional outcome at school age (median 8.3years) in 87% of the original participants. Outcome of infants who received three months of COPCA and that of infants who received three months of TIP was similar. Yet, parents of families who had received the COPCA intervention still more often used a trial and error approach when the child learned a new skill than parents of children who had received TIP. Process evaluation showed that more time spent on caregiver training and strict instructions during early intervention was associated with worse mobility. Four other physiotherapeutic actions were associated with parental educational approach. None of the neuromotor actions were associated with child outcome at school age. We conclude that long-term outcome after three months of COPCA or TIP is similar. However, our study does suggest that the professional approach of the physiotherapist can make a difference

Munc18 and Munc13 regulate early neurite outgrowth

Background information. During development, growth cones of outgrowing neurons express proteins involved in vesicular secretion, such as SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) proteins, Munc13 and Munc18. Vesicles are known to fuse in growth cones prior to synapse formation, which may contribute to outgrowth

The RAB3-RIM Pathway Is Essential for the Release of Neuromodulators

Neurons secrete neuromodulators/neuropeptides from dense-core vesicles (DCVs) by a largely unknown mechanism. Persoon et al. identify RAB3 and RIM1/2 as essential factors. RAB3’s indispensable role is the first distinct feature of DCV secretion as compared to synaptic vesicle secretion

Performance-based financing as a health system reform : mapping the key dimensions for monitoring and evaluation

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