56 research outputs found
Effect of Peierls transition in armchair carbon nanotube on dynamical behaviour of encapsulated fullerene
The changes of dynamical behaviour of a single fullerene molecule inside an
armchair carbon nanotube caused by the structural Peierls transition in the
nanotube are considered. The structures of the smallest C20 and Fe@C20
fullerenes are computed using the spin-polarized density functional theory.
Significant changes of the barriers for motion along the nanotube axis and
rotation of these fullerenes inside the (8,8) nanotube are found at the Peierls
transition. It is shown that the coefficients of translational and rotational
diffusions of these fullerenes inside the nanotube change by several orders of
magnitude. The possibility of inverse orientational melting, i.e. with a
decrease of temperature, for the systems under consideration is predicted.Comment: 9 pages, 6 figures, 1 tabl
On the Schoenberg Transformations in Data Analysis: Theory and Illustrations
The class of Schoenberg transformations, embedding Euclidean distances into
higher dimensional Euclidean spaces, is presented, and derived from theorems on
positive definite and conditionally negative definite matrices. Original
results on the arc lengths, angles and curvature of the transformations are
proposed, and visualized on artificial data sets by classical multidimensional
scaling. A simple distance-based discriminant algorithm illustrates the theory,
intimately connected to the Gaussian kernels of Machine Learning
Fast algorithms for computing sequence distances by exhaustive substring composition
The increasing throughput of sequencing raises growing needs for methods of sequence analysis and comparison on a genomic scale, notably, in connection with phylogenetic tree reconstruction. Such needs are hardly fulfilled by the more traditional measures of sequence similarity and distance, like string edit and gene rearrangement, due to a mixture of epistemological and computational problems. Alternative measures, based on the subword composition of sequences, have emerged in recent years and proved to be both fast and effective in a variety of tested cases. The common denominator of such measures is an underlying information theoretic notion of relative compressibility. Their viability depends critically on computational cost. The present paper describes as a paradigm the extension and efficient implementation of one of the methods in this class. The method is based on the comparison of the frequencies of all subwords in the two input sequences, where frequencies are suitably adjusted to take into account the statistical background
Obtaining Statistics of Turbulent Velocity from Astrophysical Spectral Line Data
Turbulence is a crucial component of dynamics of astrophysical fluids
dynamics, including those of ISM, clusters of galaxies and circumstellar
regions. Doppler shifted spectral lines provide a unique source of information
on turbulent velocities. We discuss Velocity-Channel Analysis (VCA) and its
offspring Velocity Coordinate Spectrum (VCS) that are based on the analytical
description of the spectral line statistics. Those techniques are well suited
for studies of supersonic turbulence. We stress that a great advantage of VCS
is that it does not necessary require good spatial resolution. Addressing the
studies of mildly supersonic and subsonic turbulence we discuss the criterion
that allows to determine whether a traditional tool for such a research,
namely, Velocity Centroids are dominated by density or velocity. We briefly
discuss the use of higher order correlations as the means to study
intermittency of turbulence. We discuss observational data available and
prospects of the field.Comment: 12 pages, Invited Talk, Penetrating Bars Through Masks of Cosmic
Dust, Pilanesberg National Park, South Afrika, 7 June-12 June 200
Complexity analysis of the magnetoencephalogram background activity in Alzheimer's disease patients
Inhomogeneous Poisson point process nucleation: comparison of analytical solution with cellular automata simulation
Lectures for chemists on statistics. I. Belief, probability, frequency, and statistics: decision making in a floating world
Did smokefree legislation in England reduce exposure to secondhand smoke among nonsmoking adults? Cotinine analysis from the Health Survey for England.
Background: On 1 July 2007, smokefree legislation was implemented in England, which made virtually all enclosed public places and workplaces smokefree.
Objectives: We examined trends in and predictors of secondhand smoke exposure among nonsmoking adults to determine whether exposure changed after the introduction of smokefree legislation and whether these changes varied by socioeconomic status (SES) and by household smoking status.
Methods: We analyzed salivary cotinine data from the Health Survey for England that were collected in 7 of 11 annual surveys undertaken between 1998 and 2008. We conducted multivariate regression analyses to examine secondhand smoke exposure as measured by the proportion of nonsmokers with undetectable levels of cotinine and by geometric mean cotinine.
Results: Secondhand smoke exposure was higher among those exposed at home and among lower-SES groups. Exposure declined markedly from 1998 to 2008 (the proportion of participants with undetectable cotinine was 2.9 times higher in the last 6 months of 2008 compared with the first 6 months of 1998 and geometric mean cotinine declined by 80%). We observed a significant fall in exposure after legislation was introduced—the odds of having undetectable cotinine were 1.5 times higher [95% confidence interval (CI): 1.3, 1.8] and geometric mean cotinine fell by 27% (95% CI: 17%, 36%) after adjusting for the prelegislative trend and potential confounders. Significant reductions were not, however, seen in those living in lower-social class households or homes where smoking occurs inside on most days.
Conclusions: We found that the impact of England’s smokefree legislation on secondhand smoke exposure was above and beyond the underlying long-term decline in secondhand smoke exposure and demonstrates the positive effect of the legislation. Nevertheless, some population subgroups appear not to have benefitted significantly from the legislation. This finding suggests that these groups should receive more support to reduce their exposure
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