7,544 research outputs found
The influence of self-citation corrections on Egghe's g index
The g index was introduced by Leo Egghe as an improvement of Hirsch's index h
for measuring the overall citation record of a set of articles. It better takes
into account the highly skewed frequency distribution of citations than the h
index. I propose to sharpen this g index by excluding the self-citations. I
have worked out nine practical cases in physics and compare the h and g values
with and without self-citations. As expected, the g index characterizes the
data set better than the h index. The influence of the self-citations appears
to be more significant for the g index than for the h index.Comment: 9 pages, 2 figures, submitted to Scientometric
Dynamical properties of chemical systems near Hopf bifurcation points
In this paper, we numerically investigate local properties of dynamical systems close to a Hopf bifurcation instability. We focus on chemical systems and present an approach based on the theory of normal forms for determining numerical estimates of the limit cycle that branches off at the Hopf bifurcation point. For several numerically ill-conditioned examples taken from chemical kinetics, we compare our results with those obtained by using traditional approaches where an approximation of the limit cycle is restricted to the center subspace spanned by critical eigenvectors, and show that inclusion of higher-order terms in the normal form expansion of the limit cycle provides a significant improvement of the limit cycle estimates. This result also provides an accurate initial estimate for subsequent numerical continuation of the limit cycle
Analytical realization of finite-size scaling for Anderson localization. Does the band of critical states exist for d>2?
An analytical realization is suggested for the finite-size scaling algorithm
based on the consideration of auxiliary quasi-1D systems. Comparison of the
obtained analytical results with the results of numerical calculations
indicates that the Anderson transition point is splitted into the band of
critical states. This conclusion is supported by direct numerical evidence
(Edwards and Thouless, 1972; Last and Thouless, 1974; Schreiber, 1985; 1990).
The possibility of restoring the conventional picture still exists but requires
a radical reinterpretetion of the raw numerical data.Comment: PDF, 11 page
How Millennials Can Lead Us Out of The Mess We're In: A Jew, a Muslim, and a Christian Share Leadership Lessons from the Life of Moses, By M. Schreiber, I. Case Punnett,
Reviewed by Erin Laurvic
Simulation study of a highly efficient, high resolution X-ry sensor based on self-organizing aluminum oxide
State of the art X-ray imaging sensors comprise a trade-off between the
achievable efficiency and the spatial resolution. To overcome such limitations,
the use of structured and scintillator filled aluminum oxide (AlOx) matrices
has been investigated. We used Monte-Carlo (MC) X-ray simulations to determine
the X-ray imaging quality of these AlOx matrices. Important factors which
influence the behavior of the matrices are: filling factor (surface ratio
between channels and 'closed' AlOx), channel diameter, aspect ratio, filling
material etc. Therefore we modeled the porous AlOx matrix in several different
ways with the MC X-ray simulation tool ROSI [1] and evaluated its properties to
investigate the achievable performance at different X-ray spectra, with
different filling materials (i.e. scintillators) and varying channel height and
pixel readout. In this paper we focus on the quantum efficiency, the spatial
resolution and image homogeneity
Multifractality: generic property of eigenstates of 2D disordered metals.
The distribution function of local amplitudes of eigenstates of a
two-dimensional disordered metal is calculated. Although the distribution of
comparatively small amplitudes is governed by laws similar to those known from
the random matrix theory, its decay at larger amplitudes is non-universal and
much slower. This leads to the multifractal behavior of inverse participation
numbers at any disorder. From the formal point of view, the multifractality
originates from non-trivial saddle-point solutions of supersymmetric
-model used in calculations.Comment: 4 two-column pages, no figures, submitted to PRL
Divergence Measure Between Chaotic Attractors
We propose a measure of divergence of probability distributions for
quantifying the dissimilarity of two chaotic attractors. This measure is
defined in terms of a generalized entropy. We illustrate our procedure by
considering the effect of additive noise in the well known H\'enon attractor.
Comparison of two H\'enon attractors for slighly different parameter values,
has shown that the divergence has complex scaling structure. Finally, we show
how our approach allows to detect non-stationary events in a time series.Comment: 9 pages, 6 figure
The size-star formation relation of massive galaxies at 1.5<z<2.5
We study the relation between size and star formation activity in a complete
sample of 225 massive (M > 5 x 10^10 Msun) galaxies at 1.5<z<2.5, selected from
the FIREWORKS UV-IR catalog of the CDFS. Based on stellar population synthesis
model fits to the observed restframe UV-NIR SEDs, and independent MIPS 24
micron observations, 65% of galaxies are actively forming stars, while 35% are
quiescent. Using sizes derived from 2D surface brightness profile fits to high
resolution (FWHM_{PSF}~0.45 arcsec) groundbased ISAAC data, we confirm and
improve the significance of the relation between star formation activity and
compactness found in previous studies, using a large, complete mass-limited
sample. At z~2, massive quiescent galaxies are significantly smaller than
massive star forming galaxies, and a median factor of 0.34+/-0.02 smaller than
galaxies of similar mass in the local universe. 13% of the quiescent galaxies
are unresolved in the ISAAC data, corresponding to sizes <1 kpc, more than 5
times smaller than galaxies of similar mass locally. The quiescent galaxies
span a Kormendy relation which, compared to the relation for local early types,
is shifted to smaller sizes and brighter surface brightnesses and is
incompatible with passive evolution. The progenitors of the quiescent galaxies,
were likely dominated by highly concentrated, intense nuclear star bursts at
z~3-4, in contrast to star forming galaxies at z~2 which are extended and
dominated by distributed star formation.Comment: 6 pages, 4 figures, accepted for publication in Ap
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Bleeding changes after levonorgestrel 52-mg intrauterine system insertion for contraception in women with self-reported heavy menstrual bleeding.
BackgroundThe levonorgestrel 52-mg intrauterine system has proven efficacy for heavy menstrual bleeding treatment in clinical trials, but few data exist to demonstrate how rapidly the effects occur and the effects in women with self-reported heavy bleeding, as seen commonly in clinical practice.ObjectiveEvaluate changes in bleeding patterns in women with self-reported heavy menstrual bleeding before levonorgestrel 52-mg intrauterine system insertion.Study designA total of 1714 women aged 16-45 years old received a levonorgestrel 52-mg intrauterine system in a multicenter trial evaluating contraceptive efficacy and safety for up to 10 years. At screening, participants described their baseline menstrual bleeding patterns for the previous 3 months. Participants completed daily diaries with subjective evaluation of bleeding information for the first 2 years. For this analysis, we included women with at least 1 complete 28-day cycle of intrauterine system use and excluded women using a hormonal or copper intrauterine contraception in the month prior to study enrollment. We evaluated changes in menstrual bleeding and discontinuation for bleeding complaints per 28-day cycle over 26 cycles (2 years) in women who self-reported their baseline pattern as heavy. We also compared rates of amenorrhea, defined as no bleeding or spotting, within the entire study population in women with subjective heavy menstrual bleeding at baseline compared with those who did not complain of heavy menstrual bleeding.ResultsOf the 1513 women in this analysis, 150 (9.9%) reported baseline heavy menstrual bleeding. The majority of women reported no longer experiencing heavy menstrual bleeding by the end of cycle 1 (112/150, 74.7%) with even greater rates by cycle 2 (124/148, 83.8%). At the end of cycles 6, 13, and 26, 129 of 140 (92.1%; 95% confidence interval, 87.7%-96.6%), 114 of 123 (92.7%; 95% confidence interval, 88.1%-97.3%), and 100 of 103 (97.1%; 95% confidence interval, 93.8%-100%) women reported no heavy menstrual bleeding, respectively. After cycles 13 and 26, 63 of 123 (51.2%; 95% confidence interval, 42.4%-60.1%) and 66 of 103 (64.1%; 95% confidence interval, 54.8%-73.3%), respectively, reported their bleeding as amenorrhea or spotting only. A lower proportion of women with baseline self-reported heavy menstrual bleeding reported amenorrhea as compared with women in the overall study cohort without heavy menstrual bleeding at the end of 6 cycles (319 [25.5%] vs 21 [15.0%], P=.005) and 13 cycles (382 [34.4%] vs 26 [21.1%], P=.003); differences were not significant after 19 cycles (367 [37.2%] vs 36 [31.0%], P=.022) and 26 cycles (383 [43.5%] vs 38 [36.9%], P=.21). Only 4 (2.7%) women with baseline heavy menstrual bleeding discontinued for bleeding complaints (2 for heavy menstrual bleeding and 2 for irregular bleeding), all within the first year.ConclusionMost women who self-report heavy menstrual bleeding experience significant improvement quickly after levonorgestrel 52-mg intrauterine system insertion. Discontinuation for bleeding complaints among women with baseline heavy menstrual bleeding is very low
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