Resonant Clumping and Substructure in Galactic Discs

We describe a method to extract resonant orbits from N-body simulations exploiting the fact that they close in a frame rotating with a constant pattern speed. Our method is applied to the N-body simulation of the Milky Way by Shen et al. (2010). This simulation hosts a massive bar, which drives strong resonances and persistent angular momentum exchange. Resonant orbits are found throughout the disc, both close to the bar itself and out to the very edges of the disc. Using Fourier spectrograms, we demonstrate that the bar is driving kinematic substructure even in the very outer parts of the disc. We identify two major orbit families in the outskirts of the disc that make significant contributions to the kinematic landscape, namely the m:l = 3:-2 and 1:-1 families resonating with the pattern speed of the bar. A mechanism is described that produces bimodal distributions of Galactocentric radial velocities at selected azimuths in the outer disc. It occurs as a result of the temporal coherence of particles on the 3:-2 resonant orbits, which causes them to arrive simultaneously at pericentre or apocentre. This resonant clumping, due to the in-phase motion of the particles through their epicycle, leads to both inward and outward moving groups which belong to the same orbital family and consequently produce bimodal radial velocity distributions. This is a possible explanation of the bimodal velocity distributions observed towards the Galactic anti-Centre by Liu et al. (2012). Another consequence is that transient overdensities appear and dissipate (in a symmetric fashion) on timescales equal to the their epicyclic period resulting in a periodic pulsing of the disc's surface density.Comment: 11 Figures, 1 Table. Accepted for publication in ApJ. Version 2 reflects minor changes to the text. Animation referenced in Figure 7 is available at http://hubble.shao.ac.cn/~shen/resonantclumping/DensMovie.mp

Is it time to turn our attention toward central mechanisms for post-exertional recovery strategies and performance?

• Central fatigue is accepted as a contributor to overall athletic performance, yet little research directly investigates post-exercise recovery strategies targeting the brain • Current post-exercise recovery strategies likely impact on the brain through a range of mechanisms, but improvements to these strategies is needed • Research is required to optimize post-exercise recovery with a focus on the brain Post-exercise recovery has largely focused on peripheral mechanisms of fatigue, but there is growing acceptance that fatigue is also contributed to through central mechanisms which demands that attention should be paid to optimizing recovery of the brain. In this narrative review we assemble evidence for the role that many currently utilized recovery strategies may have on the brain, as well as potential mechanisms for their action. The review provides discussion of how common nutritional strategies as well as physical modalities and methods to reduce mental fatigue are likely to interact with the brain, and offer an opportunity for subsequent improved performance. We aim to highlight the fact that many recovery strategies have been designed with the periphery in mind, and that refinement of current methods are likely to provide improvements in minimizing brain fatigue. Whilst we offer a number of recommendations, it is evident that there are many opportunities for improving the research, and practical guidelines in this area

Marshall University Music Department Presents the Jazz 12.1, Martin Saunders, Matthew Chaffins, Directors

https://mds.marshall.edu/music_perf/1540/thumbnail.jp

Powered Wheelchair Platform for Assistive Technology Development

Literature shows that numerous wheelchair platforms, of various complexities, have been developed and evaluated for Assistive Technology purposes. However there has been little consideration to providing researchers with an embedded system which is fully compatible, and communicates seamlessly with current manufacturer's wheelchair systems. We present our powered wheelchair platform which allows researchers to mount various inertial and environment sensors, and run guidance and navigation algorithms which can modify the human desired joystick trajectory, so as to assist users with negotiating obstacles, and moving from room to room. We are also able to directly access other currently manufactured human input devices and integrate new and novel input devices into the powered wheelchair platform for clinical and research assessment

Asymmetrically severe internal auditory canal hypoplasia: A case report.

We present a case of an otherwise healthy 20-month-old with congenital sensorineural hearing loss. CT and MR imaging demonstrated bilateral asymmetrically severe hypoplasia of the internal auditory canals and vestibulocochlear nerves. Additional developmental inner ear anomalies were present in this patient, including unilateral semicircular canal hypoplasia and suspected bilateral cochlear hypoplasia. The patient retained normal facial nerve function bilaterally. We highlight the current research and understanding of congenital IAC abnormalities

Spin Transport in a Mott Insulator of Ultracold Fermions

Strongly correlated materials are expected to feature unconventional transport properties, such that charge, spin, and heat conduction are potentially independent probes of the dynamics. In contrast to charge transport, the measurement of spin transport in such materials is highly challenging. We observed spin conduction and diffusion in a system of ultracold fermionic atoms that realizes the half-filled Fermi-Hubbard model. For strong interactions, spin diffusion is driven by super-exchange and doublon-hole-assisted tunneling, and strongly violates the quantum limit of charge diffusion. The technique developed in this work can be extended to finite doping, which can shed light on the complex interplay between spin and charge in the Hubbard model.Comment: 16 pages, 10 figure

Shades of green: untying the knots of green photoperception

The development of economical LED technology has enabled the application of different light qualities and quantities to control plant growth. Although we have a comprehensive understanding of plants’ perception of red and blue light, the lack of a dedicated green light sensor has frustrated our utilisation of intermediate wavelengths, with many contradictory reports in the literature. We discuss the contribution of red and blue photoreceptors to green light perception and highlight how green light can be used to improve crop quality. Importantly, our meta-analysis demonstrates that green light perception should instead be considered as a combination of distinct ‘green-’ and ‘yellow-’light induced responses. This distinction will enable clearer interpretation of plants’ behaviour in response to green light as we seek to optimise plant growth and nutritional quality in horticultural contexts

High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: part 2, photon noise theory

High-resolution broadband spectroscopy at near-infrared (NIR) wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar, with the TEDI interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec NIR echelle spectrograph. These are the first multidelay EDI demonstrations on starlight. We demonstrated very high (10×) resolution boost and dramatic (20× or more) robustness to point spread function wavelength drifts in the native spectrograph. Data analysis, results, and instrument noise are described in a companion paper (part 1). This part 2 describes theoretical photon limited and readout noise limited behaviors, using simulated spectra and instrument model with noise added at the detector. We show that a single interferometer delay can be used to reduce the high frequency noise at the original resolution (1× boost case), and that except for delays much smaller than the native response peak half width, the fringing and nonfringing noises act uncorrelated and add in quadrature. This is due to the frequency shifting of the noise due to the heterodyning effect. We find a sum rule for the noise variance for multiple delays. The multiple delay EDI using a Gaussian distribution of exposure times has noise-to-signal ratio for photon-limited noise similar to a classical spectrograph with reduced slitwidth and reduced flux, proportional to the square root of resolution boost achieved, but without the focal spot limitation and pixel spacing Nyquist limitations. At low boost (∼1×) EDI has ∼1.4× smaller noise than conventional, and at >10× boost, EDI has ∼1.4× larger noise than conventional. Readout noise is minimized by the use of three or four steps instead of 10 of TEDI. Net noise grows as step phases change from symmetrical arrangement with wavenumber across the band. For three (or four) steps, we calculate a multiplicative bandwidth of 1.8:1 (2.3:1), sufficient to handle the visible band (400 to 700 nm, 1.8:1) and most of TripleSpec (2.6:1)

Reliability of a 2-Bout exercise test on a Wattbike cycle ergometer

Purpose: To determine the intraday and interday reliability of a 2 × 4-min performance test on a cycle ergometer (Wattbike) separated by 30 min of passive recovery (2 × 4MMP). Methods: Twelve highly trained cyclists (mean ± SD; age = 20 ± 2 y, predicted VO2max = 59.0 ± 3.6 mL · kg–1 · min–1) completed six 2 × 4MMP cycling tests on a Wattbike ergometer separated by 7 d. Mean power was measured to determine intraday (test 1 [T1] to test 2 [T2]) and interday reliability (weeks 1–6) over the repeated trials. Results: The mean intraday reliabilities of the 2 × 4MMP test, as expressed by the typical error of measurement (TEM, W) and coefficient of variation (CV, %) over the 6 wk, were 10.0 W (95% confidence limits [CL] 8.2–11.8), and 2.6% (95%CL 2.1–3.1), respectively. The mean interday reliability TEM and CV for T1 over the 6 wk were 10.4 W (95%CL 8.7–13.3) and 2.7% (95%CL 2.3–3.5), respectively, and 11.7 W (95%CL 9.8–15.1) and 3.0% (95%CL 2.5–3.9) for T2. Conclusion: The testing protocol performed on a Wattbike cycle ergometer in the current study is reproducible in highly trained cyclists. The high intraday and interday reliability make it a reliable method for monitoring cycling performance and for investigating factors that affect performance in cycling events