Pressure Shifts in High-Precision Hydrogen Spectroscopy: I. Long-Range Atom-Atom and Atom-Molecule Interactions

We study the theoretical foundations for the pressure shifts in high-precision atomic beam spectrosopy of hydrogen, with a particular emphasis on transitions involving higher excited P states. In particular, the long-range interaction of an excited hydrogen atom in a 4P state with a ground-state and metastable hydrogen atom is studied, with a full resolution of the hyperfine structure. It is found that the full inclusion of the 4P_1/2 and 4P_3/2 manifolds becomes necessary in order to obtain reliable theoretical predictions, because the 1S ground state hyperfine frequency is commensurate with the 4P fine-structure splitting. An even more complex problem is encountered in the case of the 4P-2S interaction, where the inclusion of quasi-degenerate 4S-2P_1/2 state becomes necessary in view of the dipole couplings induced by the van der Waals Hamiltonian. Matrices of dimension up to 40 have to be treated despite all efforts to reduce the problem to irreducible submanifolds within the quasi-degenerate basis. We focus on the phenomenologically important second-order van der Waals shifts, proportional to 1/R^6 where R is the interatomic distance, and obtain results with full resolution of the hyperfine structure. The magnitude of van der Waals coefficients for hydrogen atom-atom collisions involving excited P states is drastically enhanced due to energetic quasi-degeneracy; we find no such enhancement for atom-molecule collisions involving atomic nP states, even if the complex molecular spectrum involving ro-vibrational levels requires a deeper analysis.Comment: 32 pages; 2 figures; this is part 1 of a series of two papers; part 1 carries article number 075005, while part 2 carries article number 075006 in the journal (online journal version has been rectified). arXiv admin note: text overlap with arXiv:1711.1003

Deep learning cardiac motion analysis for human survival prediction

Motion analysis is used in computer vision to understand the behaviour of moving objects in sequences of images. Optimising the interpretation of dynamic biological systems requires accurate and precise motion tracking as well as efficient representations of high-dimensional motion trajectories so that these can be used for prediction tasks. Here we use image sequences of the heart, acquired using cardiac magnetic resonance imaging, to create time-resolved three-dimensional segmentations using a fully convolutional network trained on anatomical shape priors. This dense motion model formed the input to a supervised denoising autoencoder (4Dsurvival), which is a hybrid network consisting of an autoencoder that learns a task-specific latent code representation trained on observed outcome data, yielding a latent representation optimised for survival prediction. To handle right-censored survival outcomes, our network used a Cox partial likelihood loss function. In a study of 302 patients the predictive accuracy (quantified by Harrell's C-index) was significantly higher (p < .0001) for our model C=0.73 (95$\%$ CI: 0.68 - 0.78) than the human benchmark of C=0.59 (95$\%$ CI: 0.53 - 0.65). This work demonstrates how a complex computer vision task using high-dimensional medical image data can efficiently predict human survival

Don’t Go Breaking My Heart: The Effects of Ability-Based Training on the Health and Fitness Characteristics of Custody Assistant Recruits

Custody Assistants (CAs) are responsible for security in detention facilities, where they may be required to complete high-intensity physical actions to ensure the personal safety of themselves, personnel, and inmates. Due to these job demands, and need for overall fitness, physical training (PT) programs are commonly implemented during academy. A paramilitary one-size-fits-all model, via modalities such as formation runs and bodyweight calisthenics, are a common form of PT. However, this type of training may not be optimal for each individual CA recruit to make positive adaptations. The purpose of this study was to analyze an ability-based approach to PT in a CA academy compared to the traditional approach. Retrospective analysis was performed on data from two CA classes consisting of 39 (23 men, 16 women) and 36 (22 men, 13 women) recruits. Recruits in the first class received 15 PT sessions in the traditional training (TT) model, where recruits were expected to all complete the same exercises and distance runs. Recruits in the ability-based training (ABT) group were subject to 15 PT sessions comprising of an ABT circuit and interval running workouts. Pre- and post-academy training, health and fitness assessments were performed, which included: resting heart rate (RHR); systolic and diastolic blood pressure (BP); push-ups and sit-ups in 60 s; and recovery heart rate from the YMCA step test. Changes in these assessments were compared using 2x2 factorial ANOVA for each measure, and a repeated measures ANOVA for each class (p &lt; 0.05). Results revealed significant differences in performance in both classes for both the recovery heart rate for the YMCA (reduced) and push-ups (increased), with no difference between the groups. The ABT group significantly lowered their RHR post academy (6.5 mean reduction in bpm). Systolic BP did not significantly change post-academy for either group, while diastolic BP increased in the TT group (5.8 mmHg mean increase) but not the ABT group. Although TT and ABT achieved similar changes in fitness as measured in this study, the ABT group was able to achieve these while also reducing RHR and maintaining diastolic BP. RHR can be a predictor of cardiovascular and all-cause mortality. Any increases in diastolic BP for the TT group could be a maladaptation to the rigors of academy, including chronic stress and the physical training load. BP is also a factor in predicting the development of coronary heart disease. Given these positive adaptations in heart rate and BP for CAs, further research should be done to confirm these results and investigate the wider and systemic implementation of ABT in CA