Multi Facet Learning in Hilbert Spaces

We extend the kernel based learning framework to learning from linear functionals, such as partial derivatives. The learning problem is formulated as a generalized regularized risk minimization problem, possibly involving several different functionals. We show how to reduce this to conventional kernel based learning methods and explore a specific application in Computational Condensed Matter Physics

Gaussian Approximation Potentials: the accuracy of quantum mechanics, without the electrons

We introduce a class of interatomic potential models that can be automatically generated from data consisting of the energies and forces experienced by atoms, derived from quantum mechanical calculations. The resulting model does not have a fixed functional form and hence is capable of modeling complex potential energy landscapes. It is systematically improvable with more data. We apply the method to bulk carbon, silicon and germanium and test it by calculating properties of the crystals at high temperatures. Using the interatomic potential to generate the long molecular dynamics trajectories required for such calculations saves orders of magnitude in computational cost.Comment: v3-4: added new material and reference

Realistic atomistic structure of amorphous silicon from machine-learning-driven molecular dynamics

Amorphous silicon (a-Si) is a widely studied noncrystalline material, and yet the subtle details of its atomistic structure are still unclear. Here, we show that accurate structural models of a-Si can be obtained using a machine-learning-based interatomic potential. Our best a-Si network is obtained by simulated cooling from the melt at a rate of 1011 K/s (that is, on the 10 ns time scale), contains less than 2% defects, and agrees with experiments regarding excess energies, diffraction data, and 29Si NMR chemical shifts. We show that this level of quality is impossible to achieve with faster quench simulations. We then generate a 4096-atom system that correctly reproduces the magnitude of the first sharp diffraction peak (FSDP) in the structure factor, achieving the closest agreement with experiments to date. Our study demonstrates the broader impact of machine-learning potentials for elucidating structures and properties of technologically important amorphous materials

The effect of substitution and isomeric imperfection on the photophysical behaviour of p-phenylenevinylene trimers

Spectroscopic and photophysical properties of two p-phenylenevinylene (PV) trimers, 2,5-substituted diheptyl-(p-phenylenevinylene) and di-[(2-ethylhexyl)oxy]-(p-phenylenevinylene), were studied using absorption spectroscopy, fluorescence and laser flash photolysis. The change from alkyl to alkyloxy groups red-shifts the absorption and fluorescence bands. The rate of internal conversion is independent of the substitution, whereas alkyloxy substitution increases the S1 [rightwards wave arrow] T1 intersystem crossing rate by an order of magnitude. The relevance for the behaviour of conjugated PPV polymers is discussed. For diheptyl-PV, a sample having ca. 3% of the cis-configuration was also studied. Comparison between the all-trans and the cis-contaminated samples revealed no significant differences in their photophysical properties.http://www.sciencedirect.com/science/article/B6TFN-4C0TKVG-4/1/bb1be7e4a272bb7910483cae927d04a

Variability of M giant stars based on Kepler photometry: general characteristics

M giants are among the longest-period pulsating stars which is why their studies were traditionally restricted to analyses of low-precision visual observations, and more recently, accurate ground-based data. Here we present an overview of M giant variability on a wide range of time-scales (hours to years), based on analysis of thirteen quarters of Kepler long-cadence observations (one point per every 29.4 minutes), with a total time-span of over 1000 days. About two-thirds of the sample stars have been selected from the ASAS-North survey of the Kepler field, with the rest supplemented from a randomly chosen M giant control sample. We first describe the correction of the light curves from different quarters, which was found to be essential. We use Fourier analysis to calculate multiple frequencies for all stars in the sample. Over 50 stars show a relatively strong signal with a period equal to the Kepler-year and a characteristic phase dependence across the whole field-of-view. We interpret this as a so far unidentified systematic effect in the Kepler data. We discuss the presence of regular patterns in the distribution of multiple periodicities and amplitudes. In the period-amplitude plane we find that it is possible to distinguish between solar-like oscillations and larger amplitude pulsations which are characteristic for Mira/SR stars. This may indicate the region of the transition between two types of oscillations as we move upward along the giant branch.Comment: 12 pages, 13 figures, accepted for publication in MNRAS. The normalized light curves are available upon reques

Traffic jams and ordering far from thermal equilibrium

The recently suggested correspondence between domain dynamics of traffic models and the asymmetric chipping model is reviewed. It is observed that in many cases traffic domains perform the two characteristic dynamical processes of the chipping model, namely chipping and diffusion. This correspondence indicates that jamming in traffic models in which all dynamical rates are non-deterministic takes place as a broad crossover phenomenon, rather than a sharp transition. Two traffic models are studied in detail and analyzed within this picture.Comment: Contribution to the Niels Bohr Summer Institute on Complexity and Criticality; to appear in a Per Bak Memorial Issue of PHYSICA

First-Principles Electronic Structure of Solid Picene

To explore the electronic structure of the first aromatic superconductor, potassium-doped solid picene which has been recently discovered by Mitsuhashi et al with the transition temperatures $T_c=7 - 20$ K, we have obtained a first-principles electronic structure of solid picene as a first step toward the elucidation of the mechanism of the superconductivity. The undoped crystal is found to have four conduction bands, which are characterized in terms of the maximally localized Wannier orbitals. We have revealed how the band structure reflects the stacked arrangement of molecular orbitals for both undoped and doped (K$_3$picene) cases, where the bands are not rigid. The Fermi surface for K$_3$picene is a curious composite of a warped two-dimensional surface and a three-dimensional one.Comment: 5 pages, 4 figure

Shortening the length of stay and mechanical ventilation time by using positive suggestions via MP3 players for ventilated patients

Long stay in intensive care unit (ICU) and prolonged ventilation are deleterious for subsequent quality of life and surcharge financial capacity. We have already demonstrated the beneficial effects of using suggestive communication on recovery time during intensive care. The aim of our present study was to prove the same effects with standardized positive suggestive message delivered by an MP3 player. Patients ventilated in ICU were randomized into a control group receiving standard ICU treatment and two groups with a standardized pre-recorded material delivered via headphones: a suggestive message about safety, self-control, and recovery for the study group and a relaxing music for the music group. Groups were similar in terms of age, gender, and mortality, but the SAPS II scores were higher in the study group than that in the controls (57.8 ± 23.6 vs. 30.1 ± 15.5 and 33.7 ± 17.4). Our post-hoc analysis results showed that the length of ICU stay (134.2 ± 73.3 vs. 314.2 ± 178.4 h) and the time spent on ventilator (85.2 ± 34.9 vs. 232.0 ± 165.6 h) were significantly shorter in the study group compared to the unified control. The advantage of the structured positive suggestive message was proven against both music and control groups

Presence of Many Stable Nonhomogeneous States in an Inertial Car-Following Model

A new single lane car following model of traffic flow is presented. The model is inertial and free of collisions. It demonstrates experimentally observed features of traffic flow such as the existence of three regimes: free, fluctuative (synchronized) and congested (jammed) flow; bistability of free and fluctuative states in a certain range of densities, which causes the hysteresis in transitions between these states; jumps in the density-flux plane in the fluctuative regime and gradual spatial transition from synchronized to free flow. Our model suggests that in the fluctuative regime there exist many stable states with different wavelengths, and that the velocity fluctuations in the congested flow regime decay approximately according to a power law in time.Comment: 4 pages, 4 figure

Stearyl methacrylate-based polymers as crystal habit modifiers for triacylglycerols

© 2018 American Chemical Society. Triacrylglycerols (TAGs) are ubiquitous and naturally occurring fat molecules that can make materials with diverse textural, mechanical, and optical properties. These properties are intimately linked to their complex hierarchical crystal structures, which can be controlled by additives that interfere with crystallization. A series of semicrystalline, bottlebrush-like copolymers have been developed to modify TAG crystallization and influence crystal habit. Synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, these copolymer additives combine crystalline poly(stearyl methacrylate) with amorphous poly(oleyl methacrylate) in either block or statistical architecture. Upon cooling mixtures of these copolymers with solutions of tristearin (SSS) in triolein (OOO), the polymeric additives affected SSS crystallization at multiple length-scales. Microscopy analysis revealed control over SSS crystal morphology indicative of crystal aggregation, while small and wide-angle X-ray diffraction (SAXD/WAXD) offered insight into the underlying mechanism of action. Analyzing the physical broadening of lamellar peaks suggested that the fraction of amorphous poly(oleyl methacrylate) controls the thickness of primary nanoplatelets, and crystal structures derived from WAXD showed that the less stable α- or β′-polymorphs of SSS are stabilized by block or statistical copolymers, respectively. Exploiting these additives to simultaneously manipulate the packing of TAG molecules within lamellae, the size of primary crystallites, and the aggregation of crystallites could diversify fat material properties and supplement wide-ranging applications