Channeling and radiation of the 855 MeV electrons enhanced by the re-channeling in a periodically bent diamond crystal

Channeling properties and radiation spectra are studied on the grounds of numerical simulations for the 855 MeV electrons in a periodically bent diamond crystal. The bent crystalline profiles are shown to enhance the re-channeling of the projectiles and to produce distinct lines in the radiation spectra. The results obtained are analyzed and contrasted to the properties of the planar channeling and of the channeling in uniformly bent crystals.Comment: 8 pages, 5 figure

Quantum Mechanical Scattering With Absorbing Boundaries

The boundary conditions (BCs) in quantum mechanical scattering are examined in finite nanoscale systems. It was previously shown that scattering BCs can be used with the principle of stationary action to solve for the scattered wave in 1D and 2D. However, the mixed boundary conditions that are required quickly become complicated in finite domains and even more so in open domains. Padding the region of interest with an absorbing region, or Stealth Region , which attenuates the wave while guaranteeing no reflection ensures that the mixed BCs are converted to simpler Dirichlet BCs. Additionally, the parallel codes were tested for scalability. The scalability of the matrix solver was poor, but the scalability of the rest of the codes was very good and overall scalability was reasonable

Evolution of Neutron-Initiated Micro-Big-Bang in superfluid He 3B

A nuclear capture reaction of a single neutron by ultra-cold superfluid $^3$He results in a rapid overheating followed by the expansion and subsequent cooling of the hot subregion, in a certain analogy with the Big Bang of the early Universe. It was shown in a Grenoble experiment that a significant part of the energy released during the nuclear reaction was not converted into heat even after several seconds. It was thought that the missing energy was stored in a tangle of quantized vortex lines. This explanation, however, contradicts the expected lifetime of a bulk vortex tangle, $10^{-5}-10^{-4}\,$s, which is much shorter than the observed time delay of seconds. In this Letter we propose a scenario that resolves the contradiction: the vortex tangle, created by the hot spot, emits isolated vortex loops that take with them a significant part of the tangle's energy. These loops quickly reach the container walls. The dilute ensemble of vortex loops attached to the walls can survive for a long time, while the remaining bulk vortex tangle decays quickly.Comment: 5 pages, PRL submitte

Identification of promising research directions using machine learning aided medical literature analysis

The rapidly expanding corpus of medical research literature presents major challenges in the understanding of previous work, the extraction of maximum information from collected data, and the identification of promising research directions. We present a case for the use of advanced machine learning techniques as an aide in this task and introduce a novel methodology that is shown to be capable of extracting meaningful information from large longitudinal corpora, and of tracking complex temporal changes within it.Postprin

Complex temporal topic evolution modelling using the Kullback-Leibler divergence and the Bhattacharyya distance

The rapidly expanding corpus of medical research literature presents major challenges in the understanding of previous work, the extraction of maximum information from collected data, and the identification of promising research directions. We present a case for the use of advanced machine learning techniques as an aide in this task and introduce a novel methodology that is shown to be capable of extracting meaningful information from large longitudinal corpora and of tracking complex temporal changes within it. Our framework is based on (i) the discretization of time into epochs, (ii) epoch-wise topic discovery using a hierarchical Dirichlet process-based model, and (iii) a temporal similarity graph which allows for the modelling of complex topic changes. More specifically, this is the first work that discusses and distinguishes between two groups of particularly challenging topic evolution phenomena: topic splitting and speciation and topic convergence and merging, in addition to the more widely recognized emergence and disappearance and gradual evolution. The proposed framework is evaluated on a public medical literature corpus.Publisher PDFPeer reviewe