A Disentangled Recognition and Nonlinear Dynamics Model for Unsupervised Learning

This paper takes a step towards temporal reasoning in a dynamically changing video, not in the pixel space that constitutes its frames, but in a latent space that describes the non-linear dynamics of the objects in its world. We introduce the Kalman variational auto-encoder, a framework for unsupervised learning of sequential data that disentangles two latent representations: an object's representation, coming from a recognition model, and a latent state describing its dynamics. As a result, the evolution of the world can be imagined and missing data imputed, both without the need to generate high dimensional frames at each time step. The model is trained end-to-end on videos of a variety of simulated physical systems, and outperforms competing methods in generative and missing data imputation tasks.Comment: NIPS 201

Directional supercontinuum generation: the role of the soliton

In this paper we numerically study supercontinuum generation by pumping a silicon nitride waveguide, with two zero-dispersion wavelengths, with femtosecond pulses. The waveguide dispersion is designed so that the pump pulse is in the normal-dispersion regime. We show that because of self-phase modulation, the initial pulse broadens into the anomalous-dispersion regime, which is sandwiched between the two normal-dispersion regimes, and here a soliton is formed. The interaction of the soliton and the broadened pulse in the normal-dispersion regime causes additional spectral broadening through formation of dispersive waves by non-degenerate four-wave mixing and cross-phase modulation. This broadening occurs mainly towards the second normal-dispersion regime. We show that pumping in either normal-dispersion regime allows broadening towards the other normal-dispersion regime. This ability to steer the continuum extension towards the direction of the other normal-dispersion regime beyond the sandwiched anomalous-dispersion regime underlies the directional supercontinuum notation. We numerically confirm the approach in a standard silica microstructured fiber geometry with two zero-dispersion wavelengths

Implicit Transfer Operator Learning: Multiple Time-Resolution Surrogates for Molecular Dynamics

Computing properties of molecular systems rely on estimating expectations of the (unnormalized) Boltzmann distribution. Molecular dynamics (MD) is a broadly adopted technique to approximate such quantities. However, stable simulations rely on very small integration time-steps ($10^{-15}\,\mathrm{s}$), whereas convergence of some moments, e.g. binding free energy or rates, might rely on sampling processes on time-scales as long as $10^{-1}\, \mathrm{s}$, and these simulations must be repeated for every molecular system independently. Here, we present Implict Transfer Operator (ITO) Learning, a framework to learn surrogates of the simulation process with multiple time-resolutions. We implement ITO with denoising diffusion probabilistic models with a new SE(3) equivariant architecture and show the resulting models can generate self-consistent stochastic dynamics across multiple time-scales, even when the system is only partially observed. Finally, we present a coarse-grained CG-SE3-ITO model which can quantitatively model all-atom molecular dynamics using only coarse molecular representations. As such, ITO provides an important step towards multiple time- and space-resolution acceleration of MD.Comment: 21 pages, 10 figure

Rapid sea ice changes in the future Barents Sea

Observed and future winter Arctic sea ice loss is strongest in the Barents Sea. However, the anthropogenic signal of the sea ice decline is superimposed by pronounced internal variability that represents a large source of uncertainty in future climate projections. A notable manifestation of internal variability is rapid ice change events (RICEs) that greatly exceed the anthropogenic trend. These RICEs are associated with large displacements of the sea ice edge which could potentially have both local and remote impacts on the climate system. In this study we present the first investigation of the frequency and drivers of RICEs in the future Barents Sea, using multi-member ensemble simulations from CMIP5 and CMIP6. A majority of RICEs are triggered by trends in ocean heat transport or surface heat fluxes. Ice loss events are associated with increasing trends in ocean heat transport and decreasing trends in surface heat loss. RICEs are a common feature of the future Barents Sea until the region becomes close to ice-free. As their evolution over time is closely tied to the average sea ice conditions, rapid ice changes in the Barents Sea may serve as a precursor for future changes in adjacent seas.publishedVersio

Health and cost-effectiveness of telehealthcare for heart failure:study protocol for a randomized controlled trial

BACKGROUND: Several heart failure studies have shown promising results for implementing telehealthcare. These studies have led to clinical and political interest in telehealthcare as a way to improve heart failure outcomes and lower costs. However, there is a need for large-scale clinical trials with cost-effectiveness assessments. METHODS/DESIGN: The present study is known as the TeleCare North Heart Failure Trial in Denmark. We are studying the health effectiveness and cost-effectiveness of a telehealth (Telekit) solution compared with usual care for patients with heart failure. The design is a multicenter, two-arm, parallel-group, nonblinded, superiority randomized controlled trial. Outpatient healthcare centers will be responsible for recruiting eligible participants (600 participants are expected) for the trial in the geographic area of the North Denmark Region. Participants are qualified for inclusion if they have been diagnosed according to national guidelines and are categorized in New York Heart Association class 2, 3, or 4. Patients must have a permanent residence and be motivated to use telehealth care. The primary outcomes are changes in health-related quality of life (assessed using the Kansas City Cardiomyopathy Questionnaire, the EuroQol EQ-5D-5L questionnaire, and the Short Form Health Survey [SF-36]) and in the incremental cost-effectiveness ratio measured from baseline to follow-up. The secondary outcomes are changes in mortality and in physiological indicators such as blood pressure, pulse, and weight. DISCUSSION: The TeleCare North Heart Failure Trial is intended to improve the international evidence base for the health effectiveness and cost-effectiveness of telehealthcare for patients with heart failure. The expectation is that the results of the trial can be generalized to all municipalities in Denmark and serve as an inspiration for further international research. TRIAL REGISTRATION: ClinicalTrials.gov (NCT02860013). Registered on 28 July 2016. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13063-016-1722-5) contains supplementary material, which is available to authorized users