1,841,185 research outputs found
Statistical inference on the h-index with an application to top-scientist performance
Despite the huge amount of literature on h-index, few papers have been
devoted to the statistical analysis of h-index when a probabilistic
distribution is assumed for citation counts. The present contribution relies on
showing the available inferential techniques, by providing the details for
proper point and set estimation of the theoretical h-index. Moreover, some
issues on simultaneous inference - aimed to produce suitable scholar
comparisons - are carried out. Finally, the analysis of the citation dataset
for the Nobel Laureates (in the last five years) and for the Fields medallists
(from 2002 onward) is proposed.Comment: 14 pages, 3 table
Metrics to evaluate research performance in academic institutions: A critique of ERA 2010 as applied in forestry and the indirect H2 index as a possible alternative
Excellence for Research in Australia (ERA) is an attempt by the Australian
Research Council to rate Australian universities on a 5-point scale within 180
Fields of Research using metrics and peer evaluation by an evaluation
committee. Some of the bibliometric data contributing to this ranking suffer
statistical issues associated with skewed distributions. Other data are
standardised year-by-year, placing undue emphasis on the most recent
publications which may not yet have reliable citation patterns. The
bibliometric data offered to the evaluation committees is extensive, but lacks
effective syntheses such as the h-index and its variants. The indirect H2 index
is objective, can be computed automatically and efficiently, is resistant to
manipulation, and a good indicator of impact to assist the ERA evaluation
committees and to similar evaluations internationally.Comment: 19 pages, 6 figures, 7 tables, appendice
Fractal statistics, fractal index and fractons
The concept of fractal index is introduced in connection with the idea of
universal class of particles or quasiparticles, termed fractons, which obey
fractal statistics. We show the relation between fractons and conformal field
theory(CFT)-quasiparticles taking into account the central charge and
the particle-hole duality , for
integer-value of the statistical parameter. The Hausdorff dimension
which labelled the universal classes of particles and the conformal anomaly are
therefore related. We also establish a connection between Rogers dilogarithm
function, Farey series of rational numbers and the Hausdorff dimension.Comment: Latex, 7 pages, references update, To appear Proceedings Workshop on
Geometrical Aspects Of Quantum Fields, 17 to 22 April 2000, State University
of Londrina (Londrina, Parana, Brazil
Differential effects of EPA vs. DHA on postprandial vascular function and the plasma oxylipin profile in men
Our objective was to investigate the impact of EPA versus DHA, on arterial stiffness and reactivity, and underlying mechanisms (with a focus on plasma oxylipins), in the postprandial state. In a 3-arm cross-over acute test meal trial men (n=26, 35-55y) at increased CVD risk, received a high fat (42.4g) test meal providing 4.16 g of EPA or DHA or control oil in random order. At 0 h and 4 h, blood samples were collected to quantify plasma fatty acids, LCn-3PUFAs derived oxylipins, nitrite and hydrogen sulfide and serum lipids and glucose. Vascular function was assessed using blood pressure, Reactive Hyperaemia Index (RHI), Pulse Wave Velocity and Augmentation Index (AIx). The DHA-rich oil significantly reduced AIx by 13% (P=0.047) with the decrease following EPA-rich oil intervention not reaching statistical significance. Both interventions increased EPA and DHA derived oxylipins in the acute postprandial state, with an (1.3 fold) increase in 19,20-DiHDPA evident after DHA intervention (P < 0.001). In conclusion, a single dose of DHA significantly improved postprandial arterial stiffness as assessed by AIx, which if sustained would be associated with a significant decrease in CVD risk. The observed increases in oxylipins provide a mechanistic insight for the AIx effect
Maser Flare Simulations from Oblate and Prolate Clouds
We investigated, through numerical models, the flaring variability that may
arise from the rotation of maser clouds of approximately spheroidal geometry,
ranging from strongly oblate to strongly prolate examples. Inversion solutions
were obtained for each of these examples over a range of saturation levels from
unsaturated to highly saturated. Formal solutions were computed for rotating
clouds with many randomly chosen rotation axes, and corresponding averaged
maser light curves plotted with statistical information. The dependence of
results on the level of saturation and on the degree of deformation from the
spherical case were investigated in terms of a variability index and duty
cycle. It may be possible to distinguish observationally between flares from
oblate and prolate objects. Maser flares from rotation are limited to long
timescales (at least a few years) and modest values of the variability index
(), and can be aperiodic or quasi-periodic. Rotation is therefore
not a good model for HO variability on timescales of weeks to months, or of
truly periodic flares.Comment: 11 pages, 12 figures, accepted for publication in MNRA
X-ray observations of the Vela pulsar: Statistics and spectrum
The Vela pulsar was observed in the range 2-60 keV by the GSFC proportional counter experiment onboard OSO-8 with temporal resolution sufficient to make possible a sensitive search for pulsed X-rays at the radio pulsar period. A statistical analysis yielded 8 per cent as the 3 sigma upper limit on the pulsed fraction. The energy spectrum is fit well by a structureless power law with number index 2.21 + or - 0.2 and absorption by a hydrogen column density of N sub H equals 2.9 + or - 2.0 times ten to the twenty-second power per sq.cm
Comparative analysis between impact factor and h-index for psychiatry journals
International audienceObjective: Journal Impact Factor (IF) is well known for being the document measure of scientific journal impact, despite several recognised limitations. Our study tried to propose a new rating system (journal h-index) applied to a sample of psychiatry journals and compared to IF. Method: In order to strictly compare their IF and h-index using the same data, we wanted to work on all the citations obtained in 2006 by the articles published in 2004-2005 in the 50 journals of our Web of Science sample of psychiatry. We studied the statistical correlation between the IF 2006 and h-index 2006. Results: The rankings of the 50 psychiatry journals were different when we took into account respectively the descending order of IF 2006 and h-index 2006 which revealed 16 steps and therefore 16 groups of journals. We noted that two journals were up 21 places (record) in h-index 2006 ranking and one journal lost 17 places. Nevertheless we obtained a high correlation coefficient well illustrated by the group of the seven first journals whose the two rankings were very close. We noted that our sample had only two journals really specialised in the publication of reviews. Conclusions: The rating of journals starting from the h-index may represent an interesting and complementary alternative to the well-known rating based on the IF. The h-index rating proposes a categorization of journals making it possible to create classes of journals with the same h-index. This type of ranking by classes is often appreciated and used by experts and scientific committees of evaluation
Analysis of unbounded operators and random motion
We study infinite weighted graphs with view to \textquotedblleft limits at
infinity,\textquotedblright or boundaries at infinity. Examples of such
weighted graphs arise in infinite (in practice, that means \textquotedblleft
very\textquotedblright large) networks of resistors, or in statistical
mechanics models for classical or quantum systems. But more generally our
analysis includes reproducing kernel Hilbert spaces and associated operators on
them. If is some infinite set of vertices or nodes, in applications the
essential ingredient going into the definition is a reproducing kernel Hilbert
space; it measures the differences of functions on evaluated on pairs of
points in . And the Hilbert norm-squared in will represent
a suitable measure of energy. Associated unbounded operators will define a
notion or dissipation, it can be a graph Laplacian, or a more abstract
unbounded Hermitian operator defined from the reproducing kernel Hilbert space
under study. We prove that there are two closed subspaces in reproducing kernel
Hilbert space which measure quantitative notions of limits at
infinity in , one generalizes finite-energy harmonic functions in
, and the other a deficiency index of a natural operator in
associated directly with the diffusion. We establish these
results in the abstract, and we offer examples and applications. Our results
are related to, but different from, potential theoretic notions of
\textquotedblleft boundaries\textquotedblright in more standard random walk
models. Comparisons are made.Comment: 38 pages, 4 tables, 3 figure
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