Summation of Power Series by Self-Similar Factor Approximants

A novel method of summation for power series is developed. The method is based on the self-similar approximation theory. The trick employed is in transforming, first, a series expansion into a product expansion and in applying the self-similar renormalization to the latter rather to the former. This results in self-similar factor approximants extrapolating the sought functions from the region of asymptotically small variables to their whole domains. The method of constructing crossover formulas, interpolating between small and large values of variables is also analysed. The techniques are illustrated on different series which are typical of problems in statistical mechanics, condensed-matter physics, and, generally, in many-body theory.Comment: 30 pages + 5 ps figures, some misprints have been correcte

Learning-based Ensemble Average Propagator Estimation

By capturing the anisotropic water diffusion in tissue, diffusion magnetic resonance imaging (dMRI) provides a unique tool for noninvasively probing the tissue microstructure and orientation in the human brain. The diffusion profile can be described by the ensemble average propagator (EAP), which is inferred from observed diffusion signals. However, accurate EAP estimation using the number of diffusion gradients that is clinically practical can be challenging. In this work, we propose a deep learning algorithm for EAP estimation, which is named learning-based ensemble average propagator estimation (LEAPE). The EAP is commonly represented by a basis and its associated coefficients, and here we choose the SHORE basis and design a deep network to estimate the coefficients. The network comprises two cascaded components. The first component is a multiple layer perceptron (MLP) that simultaneously predicts the unknown coefficients. However, typical training loss functions, such as mean squared errors, may not properly represent the geometry of the possibly non-Euclidean space of the coefficients, which in particular causes problems for the extraction of directional information from the EAP. Therefore, to regularize the training, in the second component we compute an auxiliary output of approximated fiber orientation (FO) errors with the aid of a second MLP that is trained separately. We performed experiments using dMRI data that resemble clinically achievable $q$-space sampling, and observed promising results compared with the conventional EAP estimation method.Comment: Accepted by MICCAI 201

Hybridization between damselfishes Dascyllus aruanus and D. reticulatus on the Great Barrier Reef

[Extract] Hybridization among closely related species is relatively common in marine fishes thatspawn mid-water. Although at least 81 species of tropical coral-reef fish have been reported to hybridize in nature (primarily Chaetodontidae, Pomacanthidae and Labridae), hybridization is thought to be exceedingly rare among benthic-nesting species that engage in pair spawning, such as the Pomacentridae (Montanari et al.2016 ). The Pomacentridae include >385 species, most of which form breeding pairs and nest on the benthos. Yet only four Pomacentridae hybridshave been confirmed based on strong molecular evidence (e.g., Yaakub et al. 2006), and only from areas where one or both species are rare, such as degraded habitats and/or geographic zones of overlap

Timing of preemptive vascular access placement: do we understand the natural history of advanced CKD?: an observational study

BACKGROUND: Little is known about the targets and expectations of practicing nephrologists with regard to timing of preemptive AV access surgery and how these relate to actual observed practice patterns in clinical care. METHODS: We administered a 8-question survey to assess nephrologists’ expectations for preemptive vascular access placement to 53 practicing nephrologists in California. We performed a retrospective chart review of 116 patients who underwent preemptive vascular access placement at a large academic medical center and examined progression to ESRD. RESULTS: According to our survey of nephrologists, most aimed to have preemptive vascular access created about 6 months prior to start of ESRD or when the chances of ESRD within the next year is two-thirds or greater. The estimated GFR level at which they believe match these conditions is approximately 18 ml/min/1.73 m(2). Among the 116 patients with CKD who underwent preemptive vascular access creation, the mean estimated GFR at the time of access creation was 16.1 (6.8) ml/min/1.73 m(2). Only 57 out of the 116 patients (49.1%) patients initiated maintenance HD within 1 year after surgery. CONCLUSIONS: In our study, most nephrologists aim for preemptive vascular access surgery approximately 6 months prior to the start of HD. However in fact, only approximately 50% of patients who underwent preemptive vascular access surgery started HD within 1 year. Better tools are needed to predict the natural history of advanced CKD

Artificial radionuclides in neon flying squid from the northwestern Pacific in 2011 following the Fukushima accident

In order to better understand the impact of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on a commercial marine species, neon flying squid (Ommastrephes bartramii) samples obtained from the northwestern Pacific in November 2011 were analyzed for a range of artificial and natural radionuclides (Cs-134, Cs-137, Ag-110m, U-238, Ra-226, and K-40). Short-lived radionuclides Cs-134 and Ag-110m released from the FDNPP accident were found in the samples, with an extremely high water-to-organism concentration ratio for Ag-110m ( &gt; 2.9×104). While accident-derived radionuclides were present, their associated dose rates for the squid were far lower than the relevant benchmark of 10&thinsp;µGy&thinsp;h−1. For human consumers ingesting these squid, the dose contribution from natural radionuclides, including Po-210, was far greater ( &gt; 99.9&thinsp;%) than that of Fukushima-accident radionuclides ( &lt; 0.1&thinsp;%). The whole-body to tissue and whole-body to gut concentration ratios were calculated and reported, providing a simple method to estimate the whole-body concentration in environmental monitoring programs, and filling a data gap for concentration ratios in cephalopods. Our results help fill data gaps in uptake of nuclear power plant radionuclides in the commercially important Cephalopoda class and add to scarce data on open-ocean nekton in the northwestern Pacific shortly after the Fukushima accident.</p

Inference on co-integration parameters in heteroskedastic vector autoregressions

We consider estimation and hypothesis testing on the coefficients of the co-integrating relations and the adjustment coefficients in vector autoregressions driven by shocks which display both conditional and unconditional heteroskedasticity of a quite general and unknown form. We show that the conventional results in Johansen (1996) for the maximum likelihood estimators and associated likelihood ratio tests derived under homoskedasticity do not in general hold under heteroskedasticity. As a result, standard confidence intervals and hypothesis tests on these coefficients are potentially unreliable. Solutions based on Wald tests (using a “sandwich” estimator of the variance matrix) and on the use of the wild bootstrap are discussed. These do not require the practitioner to specify a parametric model for volatility. We establish the conditions under which these methods are asymptotically valid. A Monte Carlo simulation study demonstrates that significant improvements in finite sample size can be obtained by the bootstrap over the corresponding asymptotic tests in both heteroskedastic and homoskedastic environments. An application to the term structure of interest rates in the US illustrates the difference between standard and bootstrap inferences regarding hypotheses on the co-integrating vectors and adjustment coefficients

Automatic yield-line analysis of practical slab configurations via discontinuity layout optimization

The yield-line method provides a powerful means of rapidly estimating the ultimate load that can be carried by a reinforced concrete slab. The method can reveal hidden reserves of strength in existing slabs and can lead to highly economic slabs when used in design. Originally conceived before the widespread availability of computers, the yield-line method subsequently proved difficult to computerize, limiting its appeal in recent years. However, it was recently demonstrated that the discontinuity layout optimization (DLO) procedure could be used to systematically automate the method, and various isotropically reinforced, uniformly loaded slab examples were used to demonstrate this. The main purpose of this paper is to demonstrate that the DLO procedure can also be applied to a wide range of more practical slab problems, for example involving orthotropic reinforcement, internal columns, and point, line, and patch loads. The efficacy of the procedure is demonstrated via application to a variety of example problems from the literature; for all problems considered solutions are presented that improve upon existing numerical solutions. Furthermore, in a number of cases, solutions derived using previously proposed automated yield-line analysis procedures are shown to be highly nonconservative

Birkhoff's theorem in the f(T) gravity

Generalized from the so-called teleparallel gravity which is exactly equivalent to general relativity, the $f(T)$ gravity has been proposed as an alternative gravity model to account for the dark energy phenomena. In this letter we prove that the external vacuum gravitational field for a spherically symmetric distribution of source matter in the $f(T)$ gravity framework must be static and the conclusion is independent of the radial distribution and spherically symmetric motion of the source matter that is, whether it is in motion or static. As a consequence, the Birkhoff's theorem is valid in the general $f(T)$ theory. We also discuss its application in the de Sitter space-time evolution phase as preferred to by the nowadays dark energy observations.Comment: 5p

Multiscale Topological Properties Of Functional Brain Networks During Motor Imagery After Stroke

In recent years, network analyses have been used to evaluate brain reorganization following stroke. However, many studies have often focused on single topological scales, leading to an incomplete model of how focal brain lesions affect multiple network properties simultaneously and how changes on smaller scales influence those on larger scales. In an EEG-based experiment on the performance of hand motor imagery (MI) in 20 patients with unilateral stroke, we observed that the anatomic lesion affects the functional brain network on multiple levels. In the beta (13-30 Hz) frequency band, the MI of the affected hand (Ahand) elicited a significantly lower smallworldness and local efficiency (Eloc) versus the unaffected hand (Uhand). Notably, the abnormal reduction in Eloc significantly depended on the increase in interhemispheric connectivity, which was in turn determined primarily by the rise in regional connectivity in the parieto-occipital sites of the affected hemisphere. Further, in contrast to the Uhand MI, in which significantly high connectivity was observed for the contralateral sensorimotor regions of the unaffected hemisphere, the regions that increased in connection during the Ahand MI lay in the frontal and parietal regions of the contralaterally affected hemisphere. Finally, the overall sensorimotor function of our patients, as measured by Fugl-Meyer Assessment (FMA) index, was significantly predicted by the connectivity of their affected hemisphere. These results increase our understanding of stroke-induced alterations in functional brain networks.Comment: Neuroimage, accepted manuscript (unedited version) available online 19-June-201