A fast and exact ww-stacking and ww-projection hybrid algorithm for wide-field interferometric imaging

The standard wide-field imaging technique, the $w$-projection, allows correction for wide-fields of view for non-coplanar radio interferometric arrays. However, calculating exact corrections for each measurement has not been possible due to the amount of computation required at high resolution and with the large number of visibilities from current interferometers. The required accuracy and computational cost of these corrections is one of the largest unsolved challenges facing next generation radio interferometers such as the Square Kilometre Array. We show that the same calculation can be performed with a radially symmetric $w$-projection kernel, where we use one dimensional adaptive quadrature to calculate the resulting Hankel transform, decreasing the computation required for kernel generation by several orders of magnitude, whilst preserving the accuracy. We confirm that the radial $w$-projection kernel is accurate to approximately 1% by imaging the zero-spacing with an added $w$-term. We demonstrate the potential of our radially symmetric $w$-projection kernel via sparse image reconstruction, using the software package PURIFY. We develop a distributed $w$-stacking and $w$-projection hybrid algorithm. We apply this algorithm to individually correct for non-coplanar effects in 17.5 million visibilities over a $25$ by $25$ degree field of view MWA observation for image reconstruction. Such a level of accuracy and scalability is not possible with standard $w$-projection kernel generation methods. This demonstrates that we can scale to a large number of measurements with large image sizes whilst still maintaining both speed and accuracy.Comment: 9 Figures, 19 Pages. Accepted to Ap

Biomechanical Indicators of Steeplechase Hurdle Success

The steeplechase is a long-distance running event that requires competitors to jump over 28 hurdles and 7 water jumps over the course of the race. This frequent jumping means that hurdling technique is important and the ability to maintain speed over the barriers can help a runner succeed. PURPOSE: To determine which variables predict maintenance of speed while hurdling in the steeplechase. METHODS: Data were collected at the USATF outdoor championships and Olympic Trials from 2011 to 2023 for both men and women. A Sony video camera running at 120 Hz was used to evaluate several aspects of the runner’s mechanics as well as their horizontal velocity before jumping and after landing. The ratio of exit to approach velocity was taken and used as our measure of how successful the jump was, a ratio closer to one means they lost less velocity when jumping over the hurdle. A stepwise linear regression was done for both men and women and was used to determine which variables best predicted hurdle success. RESULTS: Men and women had slightly different variables that predicted successful hurdling. The model for women had an R2 of 0.179 (p \u3c 0.001). For men the R2 was 0.060 (p\u3c0.001). Both models included increased takeoff distance and greater knee flexion angle at takeoff as beneficial. Both models also included the lead knee extension when going over the hurdle, but it was a negative relationship in women and a positive relationship in men. The model for the men also included a less extended hip at takeoff. The model for the women added the clearance of the hip over the hurdle. CONCLUSION: Coaches should focus on having athletes take off a little farther from the barrier and working to have a more flexed knee at takeoff. Men and women have differing hurdling techniques in the steeplechase. While some of the same variables are important, there are also distinct differences. When coaching athletes these differences in technique should be accounted for

Biomechanical Indicators of Water Jump Performance

During the course of the steeplechase track event athletes pass through one water jump obstacle per each of seven laps. There are many different elements of technique that can be used to improve maintenance of horizontal velocity through each obstacle. PURPOSE: This study investigated which biomechanical factors were correlated with higher ratios of exit velocity to approach velocity while negotiating the water jump obstacle. METHODS: Biomechanical data were gathered from the steeplechase event for both men and women at the USATF Outdoor Championships and Olympic Trials. Data were included from 2011 through 2023. Biomechanical data were measured from recorded video using Dartfish video analysis software. Knee and hip angles, time of stepping on the barrier, and take off and landing distances were measured at key points of the movement along with approach and exit velocities. These velocities were measured through 2m sections prior to the barrier and after leaving the water pit. A stepwise linear regression tested for correlations between the exit to approach velocities to a variety of biomechanical measurements. RESULTS: The predictor variables for both men and women were the same, including: landing distance, pushoff angle, and barrier time normalized to average velocity (Women R2=0.290, p2=0.236, pCONCLUSION: According to our data, steeplechase athletes can improve horizontal velocity maintenance through the water jump obstacle by landing further from the barrier into the water, extending more at the knee while pushing off the barrier, and spending less time on the barrier. While previous research showed women lose more velocity during the water jump, the correlated factors were the same and were even entered into the model in the same order showing coaches and athletes the importance of where to focus their technique improvements

Using head-tail galaxies to constrain the intracluster magnetic field: an in-depth study of PKS J0334-3900

We present a multi-wavelength study of the radio galaxy PKS J0334-3900 at the centre of Abell 3135. The spectro-polarimetric radio observations are combined with spectroscopic optical and X-ray data to illustrate the use of Head-Tail radio galaxies to reveal properties of the intracluster medium. ATCA observations at 1.4, 2.5, 4.6 & 8.6 GHz are presented with a detailed analysis of the morphology and spectral indices giving physical parameters to constrain the dynamical history of the galaxy. Using these constraints we produce a simulation of PKS J0334-3900. We find that this Head-Tail morphology can be induced via a combination of orbital motion due to a binary companion and relative motion through the ICM. New Chandra images of A3135 are presented from which we obtain a cluster electron density of n_(e,0) = (1.06 +/- 0.11 x 10^(-3) cm^(-3), a global temperature of 2.4 ^(+0.51)_(-0.38) keV and a lower limit to the radio jet power of PKS J0334-3900 of 1.6 x 10^(44) erg/s. A new redshift analysis of the cluster from available spectroscopic data shows A3135 to be comprised of galaxies with 0.058 < z < 0.066 and gives a new mean cluster redshift of 0.06228 +/- 0.00015. We also uncovered a background subgroup between 0.066 < z < 0.070. Stokes Q and U data of Abell 3135 were used to obtain rotation measure values along the line of sight to PKS J0334-3900. Using our simulation we are able to infer the distance between the jets to be 154 +/- 16 kpc, which when combined with the difference in rotation measure between the jets provides a novel new way to estimate the average magnetic field within a cluster. A lower limit to the cluster B-field was calculated to be 0.09 +/- 0.03 micro Gauss. We show observations of Head-Tail galaxies can be used to infer information on the cluster environment, showing them to be an important class of objects in next generation all sky surveys.Comment: 17 pages, 15 figures, accepted to MNRAS. Version 2 corrects a mistake in the average RM between the jets (and hence the lower estimate of the cluster B-field) which was found during proofin

Effect of Air Resistance on Braking and Propulsive Impulses During Treadmill Running.

Treadmill running is a convenient option for runners looking to avoid adverse environmental conditions or that prefer a gym setting. Outdoor running includes air resistance, whereas treadmill running typically does not. Very little research has been focused on the influence of air resistance and its role on kinetic factors during running. PURPOSE: To determine how anterior/posterior impulses change due to air resistance during two different treadmill speeds. METHODS: A wind tunnel was placed 0.61m from the edge of a force instrumented treadmill (Bertec, Boston, MA) while attempting to run 1.12m from the opening of it. Seven subjects ran at two speeds (3.35 m/s, 4.46 m/s) on two separate visits while alternating the order of speeds run. During each speed, runners completed one minute of running during conditions of no fan and a fan representing air resistance equal to treadmill speed. Forces were collected for the final 25s segment of each air velocity. RESULTS: At the faster treadmill speed, horizontal impulse was significantly greater in the propulsive direction during the air resistance condition (5.3% ± 7.4%, p=0.019). Braking impulses were smaller (-3.2% ± 5.1%, p=0.035) while propulsive impulse remained non-significant (2.1% ± 4.5%, p=0.104). At the slower treadmill speed, horizontal impulse was trending toward significance (3.1% ± 5.9%, p=0.080) while braking impulse remained non-significant (-1.2% ± 2.8%, p=0.147) and propulsive impulse was greater with air resistance (2.3% ± 3.3%, p=0.024). CONCLUSION: The current data begins to explain that in order to keep metabolic costs low while still compensating for air resistance during running, individuals will increase net horizontal impulse by opting to decrease braking impulse while maintaining propulsive impulse. These findings match the work of Chang and Kram (2000) who asserted that “the metabolic cost of generating horizontal propulsive forces during normal running constitutes more than one-third of the total cost of steady-speed running”

Tratamiento transdiagnóstico por internet de la ansiedad y la depresión

Anxiety and depression are common, chronic, disabling and frequently comorbid, but manypeople experience barriers accessing treatment. Internet-delivered psychological treatments (iPT)have considerable potential to increase access, while transdiagnostic (TD) interventions, which aimto simultaneously treat multiple disorders, represent an emerging approach that may facilitate thetreatment of comorbidity. The present paper describes a conceptual and pragmatic rationale for combiningiPT and TD approaches. It also describes the authors’ experiences in developing and evaluatingTD iPT protocols for anxiety and depression. The results of 4 randomised controlled trials and oneopen trial (N = 572) are reviewed. The results of these trials are encouraging and indicate TD iPT cansignificantly reduce symptoms of both principal and comorbid disorders. However, independent replicationof the existing findings is required and many outstanding questions remain. We watch withinterest how further conceptual and technological developments influence the content and deliveryof these interventions.La ansiedad y la depresión son fenómenos comunes, crónicos, incapacitantes y frecuentementecomórbidos, pero muchas personas tienen dificultades para acceder a su tratamiento. Lostratamientos psicológicos administrados por internet poseen un gran potencial para incrementar elacceso de los pacientes, mientras que las intervenciones transdiagnósticas, que se dirigen a tratarsimultáneamente múltiples trastornos, representan un enfoque emergente que podría facilitar eltratamiento de dicha comorbilidad. El presente trabajo describe los fundamentos conceptuales ypragmáticos para la aplicación del transdiagnóstico a través de internet. También se describe la experienciade los autores en el desarrollo y evaluación de protocolos transdiagnósticos administradospor internet para el tratamiento de la ansiedad y la depresión. Se revisan los resultados procedentesde 4 ensayos controlados aleatorizados y un ensayo abierto (N = 572). Los resultados de estos ensayosson alentadores e indican que el transdiagnóstico administrado por internet puede reducir significativamentetanto los síntomas de los trastornos principales como de los trastornos comórbidos.Sin embargo, aparte de que existen cuestiones sin resolver, se requiere una replicación independientede los resultados existentes. Observamos con interés la forma en que los futuros desarrollos teóricosy tecnológicos influyan sobre el contenido y administración de estas intervenciones

Does early surgery improve outcomes for periprosthetic fractures of the hip and knee? : A systematic review and meta-analysis

Open access via Springer Compact AgreementPeer reviewedPublisher PD

Predicting population responses to environmental change from individual-level mechanisms: towards a standardized mechanistic approach

Animal populations will mediate the response of global biodiversity to environmental changes. Population models are thus important tools for both understanding and predicting animal responses to uncertain future conditions. Most approaches, however, are correlative and ignore the individual-level mechanisms that give rise to population dynamics. Here, we assess several existing population modelling approaches, and find limitations to both ‘correlative’ and ‘mechanistic’ models. We advocate the need for a standardised mechanistic approach for linking individual mechanisms (physiology, behaviour and evolution) to population dynamics in spatially explicit landscapes. Such an approach is potentially more flexible and informative than current population models. Key to realising this goal, however, is overcoming current data limitations, the development and testing of eco-evolutionary theory to represent interactions between individual mechanisms, and standardised multidimensional environmental change scenarios which incorporate multiple stressors. Such progress is essential in supporting environmental decisions in uncertain future conditions