Optical tracking systems typically trade off between astrometric precision and field of view. In this work, we showcase a networked approach to optical tracking using very wide field-of-view imagers that have relatively low astrometric precision on the scheduled OSIRIS-REx slingshot manoeuvre around Earth on 22 Sep 2017. As part of a trajectory designed to get OSIRIS-REx to NEO 101955 Bennu, this flyby event was viewed from 13 remote sensors spread across Australia and New Zealand to promote triangulatable observations. Each observatory in this portable network was constructed to be as lightweight and portable as possible, with hardware based off the successful design of the Desert Fireball Network. Over a 4-h collection window, we gathered 15 439 images of the night sky in the predicted direction of the OSIRIS-REx spacecraft. Using a specially developed streak detection and orbit determination data pipeline, we detected 2 090 line-of-sight observations. Our fitted orbit was determined to be within about 10 km of orbital telemetry along the observed 109 262 km length of OSIRIS-REx trajectory, and thus demonstrating the impressive capability of a networked approach to Space Surveillance and Tracking.

The presence of an atrial septal defect in pulmonary hypertension has benefits and detractions. Even in idiopathic pulmonary arterial hypertension, a significant left-to-right shunt at atrial level may increase the pulmonary arterial pressure and exacerbate the disease. However, it is well recognised that the presence of an atrial communication may be protective in subgroups with severe disease, allowing maintenance of cardiac output during times of increased pulmonary resistance. In the present paper, we present the case of a young boy with significant idiopathic pulmonary arterial hypertension and an atrial septal defect. We report our technique of septal occlusion using a device to decrease left-to-right shunting with concomitant stent insertion in that device to maintain the potential for right-to-left shunting during times of high pulmonary arterial pressure.

Hydrogels pose unique challenges to nanoindentation including sample preparation, control of experimental parameters, and limitations imposed by mechanical testing instruments and data analysis originally intended for harder materials. The artifacts that occur during nanoindentation of hydrated samples have been described, but the material properties obtained from hydrated nanoindentation have not yet been related to the material properties obtained from macroscale testing. To evaluate the best method for correlating results from microscale and macroscale tests of soft materials, nanoindentation and unconfined compression stress-relaxation tests were performed on poly-2-hydroxyethyl methacrylate (pHEMA) hydrogels with a range of cross-linker concentrations. The nanoindentation data were analyzed with the Oliver–Pharr elastic model and the Maxwell–Wiechert (j = 2) viscoelastic model. The unconfined compression data were analyzed with the Maxwell–Wiechert model. This viscoelastic model provided an excellent fit for the stress-relaxation curves from both tests. The time constants from nanoindentation and unconfined compression were significantly different, and we propose that these differences are due to differences in equilibration time between the microscale and macroscale experiments and in sample geometry. The Maxwell–Wiechert equilibrium modulus provided the best agreement between nanoindentation and unconfined compression. Also, both nanoindentation analyses showed an increase in modulus with each increasing cross-linker concentration, validating that nanoindentation can discriminate between similar, low-modulus, hydrated samples.

Many studies have focused on the computation of the structural and electronic properties of liquid crystal molecules in a single static conformation. However, a complete and quantitatively accurate description of the macroscopic optical properties of liquid crystals must also include effects due to the long-range nematic order, the anisotropic local environment surrounding the molecules, and the dynamical fluctuations of the molecules. In this paper, we explore methods to simplify computation of the molecular average second hyperpolarizability of the nematogen 4-n-pentyl-4-cyanobiphenyl (5CB). The model we develop relates changes in the geometrical parameters of the molecule to corresponding changes in the hyperpolarizability. The model is first applied to a simple donor-acceptor substituted polyene, and then to 5CB. Use of a small set of geometrical variables results in a slight increase in the RMS deviation of the predicted hyperpolarizability over the deviation obtained from a complete set. We then discuss the importance of this work for the development of means to calculate macroscopic optical properties.