422 research outputs found
Magnetic Fluctuations and Turbulence in the Venus Magnetosheath and Wake
Recent research has shown that distinct physical regions in the Venusian
induced magnetosphere are recognizable from the variations of strength and of
wave/fluctuation activity of the magnetic field. In this paper the statistical
properties of magnetic fluctuations are investigated in the Venusian
magnetosheath, terminator, and wake regions. The latter two regions were not
visited by previous missions. We found 1/f fluctuations in the magnetosheath,
large-scale structures near the terminator and more developed turbulence
further downstream in the wake. Location independent short-tailed non-Gaussian
statistics was observed.Comment: 16 pages, 4 figure
On the entropy of plasmas described with regularized -distributions
In classical thermodynamics the entropy is an extensive quantity, i.e.\ the
sum of the entropies of two subsystems in equilibrium with each other is equal
to the entropy of the full system consisting of the two subsystems. The
extensitivity of entropy has been questioned in the context of a theoretical
foundation for the so-called -distributions, which describe plasma
constituents with power-law velocity distributions. We demonstrate here, by
employing the recently introduced {\it regularized -distributions},
that entropy can be defined as an extensive quantity even for such
power-law-like distributions that truncate exponentially.Comment: Preprint accepted for publication in Phys. Rev.
Anatomical investigation of 4,000-years old cedrus libani wood remains from Egypt
The anatomical composition of the 4,000-years old Cedrus libaniremains from an archeological excavation is the same as the anatomical composition of xylem of recent Cedrus libani. The width of growth rings in the remains is narrow. The mean values are 0.82-1.78 mm. Within the growth ring, the early wood is wide and the late wood is fairly narrow. According to the growth ring widht series, as nowadays, too, unfavourable years alternated with more favourable ones. Length of tracheids were formed in the wider growth rings, and longer ones in the narrower. Within the length of tracheids increases from growth ring boundary to growth ring boundary.Frequencies of the length of tracheids within a growth ring show the Gaussian distribution. The tracheid cells end in normal tip. The cell wall thickness is thin (3.1 ”m) in the early wood, and thick (9.6 ”m) in the late wood. The cell lumen is wide in the early wood (44.3”m), and narrow in the late wood (23.8 ”m)
Polyethylene imine-based receptor immobilization for label free bioassays
Polyethylene imine (PEI) based immobilization of antibodies is described and the concept is proved on the
label free assay of C-Reactive Protein (CRP). This novel immobilization method is composed of a hyperbranched
PEI layer which was deposited at a high pH (9.5) on the sensor surface. The free amino groups
of PEI were derivatized with neutravidin by Biotin N-hydroxysuccinimide ester and the biotinylated
anti-CRP antibody immobilized on this layer. Direct binding assay of recombinant CRP was successfully
performed in the low ÎŒg/ml concentrations using a label free optical waveguide biosensor
Multi-scale magnetic field intermittence in the plasma sheet
This paper demonstrates that intermittent magnetic field fluctuations in the
plasma sheet exhibit transitory, localized, and multi-scale features. We
propose a multifractal based algorithm, which quantifies intermittence on the
basis of the statistical distribution of the 'strength of burstiness',
estimated within a sliding window. Interesting multi-scale phenomena observed
by the Cluster spacecraft include large scale motion of the current sheet and
bursty bulk flow associated turbulence, interpreted as a cross-scale coupling
(CSC) process.Comment: 18 pages, 7 figure
Trapping Long-Lifetime Excitons in a Two-Dimensional Harmonic Potential
We report an important step forward for the goal of unambiguous observation
of Bose-Einstein condensation of excitons in semiconductors. We have
demonstrated a system in which excitons live for microseconds, much longer than
their thermalization time, move over distances of hundreds of microns, and can
be trapped in a harmonic potential exactly analous to the traps for atomic
condensates. We also report recent results of a new method for observing
evidence of Bose-Einstein condensation, by angular resolution of the emitted
luminescence.Comment: Invited paper for International Conference on Spontaneous Coherence
in Excitonic Systems, Seven Springs, PA, May 2004. To appear in Solid State
Communication
Quantitative features of multifractal subtleties in time series
Based on the Multifractal Detrended Fluctuation Analysis (MFDFA) and on the
Wavelet Transform Modulus Maxima (WTMM) methods we investigate the origin of
multifractality in the time series. Series fluctuating according to a qGaussian
distribution, both uncorrelated and correlated in time, are used. For the
uncorrelated series at the border (q=5/3) between the Gaussian and the Levy
basins of attraction asymptotically we find a phase-like transition between
monofractal and bifractal characteristics. This indicates that these may solely
be the specific nonlinear temporal correlations that organize the series into a
genuine multifractal hierarchy. For analyzing various features of
multifractality due to such correlations, we use the model series generated
from the binomial cascade as well as empirical series. Then, within the
temporal ranges of well developed power-law correlations we find a fast
convergence in all multifractal measures. Besides of its practical significance
this fact may reflect another manifestation of a conjectured q-generalized
Central Limit Theorem
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