Athletic performance data are modeled in an effort to better understand the relationship between both hours spent training and a measurement of “commitment” to that training, and improvements in ...performance. Both increased training time and greater commitment were predicted to produce larger increases in performance improvement, and commitment was predicted to be the more important determinant of improvement. The performance of 108 soccer players (ages 9–18) was quantified over a 10-week training program. Hours spent training ranged from 16 to 90 during the course of the study, while commitment scores ranged from 0.55 to 2.00, based on a scale from 0.00 to 2.40. A model selection approach was used to discriminate among models specifying relationships between training hours and improvement, and commitment and improvement. Despite considerable variability in the data, results provided strong evidence for an increase in performance improvement with both training hours and commitment score. The best models for hours and commitment were directly compared by computing an evidence ratio of 5799, indicating much stronger evidence favoring the model based on commitment. Results of analyses such as these go beyond anecdotal experience in an effort to establish a formal evidentiary basis for athletic training programs.
Free space optical communications utilizing orbital angular momentum beams have recently emerged as a new technique for communications with potential for increased channel capacity. Turbulence due to ...changes in the index of refraction emanating from temperature, humidity, and air flow patterns, however, add nonlinear effects to the received patterns, thus making the demultiplexing task more difficult. Deep learning techniques have been previously been applied to solve the demultiplexing problem as an image classification task. Here we make use of a newly developed theory suggesting a link between image turbulence and photon transport through the continuity equation to describe a method that utilizes a "shallow" learning method instead. The decoding technique is tested and compared against previous approaches using deep convolutional neural networks. Results show that the new method can obtain similar classification accuracies (bit error ratio) at a small fraction (1/90) of the computational cost, thus enabling higher bit rates.
Exoplanet-induced Radio Emission from M Dwarfs Turnpenney, Sam; Nichols, Jonathan D.; Wynn, Graham A. ...
Astrophysical journal/The Astrophysical journal,
02/2018, Letnik:
854, Številka:
1
Journal Article
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We consider the magnetic interaction of exoplanets orbiting M dwarfs, calculating the expected Poynting flux carried upstream along Alfvén wings to the central star. A region of emission analogous to ...the Io footprint observed in Jupiter's aurora is produced, and we calculate the radio flux density generated near the surface of the star via the electron-cyclotron maser instability. We apply the model to produce individual case studies for the TRAPPIST-1, Proxima Centauri, and dwarf NGTS-1 systems. We predict steady-state flux densities of up to ∼10 Jy and sporadic bursts of emission of up to ∼1 mJy from each case study, suggesting these systems may be detectable with the Very Large Array and the Giant Metrewave Radio Telescope, and perhaps the Square Kilometre Array in the future. Finally, we present a survey of 85 exoplanets orbiting M dwarfs, identifying 11 such objects capable of generating radio emission above 10 Jy.
•Proposes physics-based model for image sequences degraded by atmospheric turbulence.•Shows the model to be low-dimensional over spatially localized regions of the image.•Provides algorithm for ...identifying local image models and method for combining to form global image model.•Demonstrates the ability to recover clean image from surrogate global image model.
This work exploits a connection between optimal transport theory and the physics of image propagation to yield a locally low-dimensional model of turbulence-corrupted imagery. Optimal transport produces an invertible, pixel-wise linear trajectories to approximate the globally nonlinear turbulence between a clean and turbulence corrupted image pair. We use the low-dimensional model to fit subsets of the optimal transport vector fields and stitch the local models into a surrogate for the global map to be used for image cleaning. Experiments are performed on laboratory generated data of beam propagation using different values of the Fried parameter (a scale measuring turbulence coherence) as well as a toy data set. The results suggest this is a fruitful direction, and first step, towards using multiple realizations of turbulence corrupted images to learn a blind surrogate for the optimal transport vector field for image cleaning.
Polysaccharides have key biological functions and can be harnessed for therapeutic roles, such as the anticoagulant heparin. Their complexity-e.g., >100 monosaccharides with variety in linkage and ...branching structure-significantly complicates analysis compared to other biopolymers such as DNA and proteins. More, and improved, analysis tools have been called for, and here we demonstrate that solid-state silicon nitride nanopore sensors and tuned sensing conditions can be used to reliably detect native polysaccharides and enzymatic digestion products, differentiate between different polysaccharides in straightforward assays, provide new experimental insights into nanopore electrokinetics, and uncover polysaccharide properties. We show that nanopore sensing allows us to easily differentiate between a clinical heparin sample and one spiked with the contaminant that caused deaths in 2008 when its presence went undetected by conventional assays. The work reported here lays a foundation to further explore polysaccharide characterization and develop assays using thin-film solid-state nanopore sensors.
The electromagnetic interaction between Europa and the plasma sheet in the Jovian magnetosphere generates Alfvén waves, ultimately generating auroral footprints in Jupiter's atmosphere. The position ...of Europa's auroral footprint is a proxy for travel time of the Alfvén waves. We measured Europa's footprint position using the far‐ultraviolet images of Jupiter obtained by the Hubble Space Telescope in two observing campaigns in 2014 and 2022. The measured footprint position indicates a longer Alfvén travel time in the 2022 campaign. We retrieved the plasma sheet parameters at Europa's orbit from the footprint position by tracing the Alfvén waves launched at Europa and found an increase of both mass density and temperature in the plasma sheet in 2022. The Poynting flux generated at Europa is calculated with the retrieved plasma sheet parameters, which suggests the total energy transfer from Europa to its auroral footprint is similar to the case of Io.
Plain Language Summary
Europa is an obstacle to the plasma corotating with Jupiter's magnetosphere. Through the interaction between Europa and the magnetospheric plasma flow, Alfvén waves are launched at Europa. The Alfvén waves propagate along the field line and ultimately generate auroral emissions at locations distant from the instantaneous magnetic footprint of Europa. The position of Europa's auroral footprint is a proxy for the travel time of the Alfvén waves. We measured the position of Europa's auroral footprint using the far‐ultraviolet images of Jupiter obtained by the Hubble Space Telescope in two observing campaigns in 2014 and 2022. We found large deviations of the footprint position between the two observing campaigns. By tracing the Alfvén waves launched at Europa, we retrieved plasma mass density and temperature at Europa's orbit from the measured footprint position. It is revealed that time variation in the plasma mass density and temperature caused the deviations in the footprint position. We also calculated the Poynting flux generated at Europa using the retrieved plasma parameters and found that the total energy transfer from Europa to its auroral footprint is similar to the case of Io.
Key Points
We measured the equatorial lead angle of Europa's auroral footprint in Jupiter's atmosphere with the HST data taken in 2014 and 2022
Plasma conditions at Europa's orbit are retrieved from the measured lead angle by tracing the Europa‐originated Alfvén waves
Changes in the plasma conditions at Europa's orbit can account for the variation of the footprint lead angle
ABSTRACT
The structure and dynamics of the magnetospheres of the outer planets, particularly Saturn and Jupiter, have been explored through both remote and in situ observations. Interpreting these ...observations often necessitates simultaneous knowledge of the solar-wind conditions impinging on the magnetosphere. Without an available upstream monitor, solar-wind context is typically provided using models initiated with either the output of magnetogram-constrained coronal models or, more commonly, in situ observations from 1 au. While 1-au observations provide a direct measure of solar-wind conditions, they are single-point observations and thus require interpolation to provide inputs to outer-heliosphere solar-wind models. In this study, we test the different interpolation methods using synthetic 1-au observations of time-evolving solar-wind structure. The simplest method is ‘corotation’, which assumes solar-wind structure is a steady state and rotates with the Sun. This method of reconstruction produces discontinuities in the solar-wind inputs as new observations become available. This can be reduced by corotating both backwards and forwards in time, but this still introduces large errors in the magnitude and timing of solar-wind streams. We show how the dynamic time warping (DTW) algorithm can provide around an order-of-magnitude improvement in solar-wind inputs to the outer-heliosphere model from in situ observations near 1 au. This is intended to build the foundation for further work demonstrating and validating methods to improve inner-boundary conditions of outer-heliosphere solar-wind models, including dealing with solar-wind transients and quantifying the improvements at Saturn and Jupiter.
This work revisits the problem of detecting and localizing point sources in a scene using an imaging array and suggests two improvements over traditional approaches. First, the importance of ...covariance matrix estimation is discussed and several estimators are compared. In particular, the so-called shrinkage estimator is shown to produce better estimates of the covariance matrix and consequently provides improved detection performance over the commonly used naive estimator. We also develop an iterative algorithm for obtaining maximum likelihood estimates of the point source parameters. By using these estimates in forming the detection statistic, further improvements are demonstrated over previously used estimators.
Context. The detection of radio emissions from exoplanets will open up a vibrant new research field. Observing planetary auroral radio emission is the most promising method to detect exoplanetary ...magnetic fields, the knowledge of which will provide valuable insights into the planet’s interior structure, atmospheric escape, and habitability. Aims. We present LOFAR (LOw-Frequency ARray) Low Band Antenna (LBA: 10–90 MHz) circularly polarized beamformed observations of the exoplanetary systems 55 Cancri, υ Andromedae, and τ Boötis. All three systems are predicted to be good candidates to search for exoplanetary radio emission. Methods. We applied the BOREALIS pipeline that we have developed to mitigate radio frequency interference and searched for both slowly varying and bursty radio emission. Our pipeline has previously been quantitatively benchmarked on attenuated Jupiter radio emission. Results. We tentatively detect circularly polarized bursty emission from the τ Boötis system in the range 14–21 MHz with a flux density of ~890 mJy and with a statistical significance of ~3 σ . For this detection, we do not see any signal in the OFF-beams, and we do not find any potential causes which might cause false positives. We also tentatively detect slowly variable circularly polarized emission from τ Boötis in the range 21–30 MHz with a flux density of ~400 mJy and with a statistical significance of >8 σ . The slow emission is structured in the time-frequency plane and shows an excess in the ON-beam with respect to the two simultaneous OFF-beams. While the bursty emission seems rather robust, close examination casts some doubts on the reality of the slowly varying signal. We discuss in detail all the arguments for and against an actual detection, and derive methodological tests that will also apply to future searches. Furthermore, a ~2 σ marginal signal is found from the υ Andromedae system in one observation of bursty emission in the range 14–38 MHz and no signal is detected from the 55 Cancri system, on which we placed a 3 σ upper limit of 73 mJy for the flux density at the time of the observation. Conclusions. Assuming the detected signals are real, we discuss their potential origin. Their source probably is the τ Boötis planetary system, and a possible explanation is radio emission from the exoplanet τ Boötis b via the cyclotron maser mechanism. Assuming a planetary origin, we derived limits for the planetary polar surface magnetic field strength, finding values compatible with theoretical predictions. Further observations with LOFAR-LBA and other low-frequency telescopes, such as NenuFAR or UTR-2, are required to confirm this possible first detection of an exoplanetary radio signal.
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