1,293 research outputs found
Towards a Fisher-information description of complexity in de Sitter universe
Recent developments on holography and quantum information physics suggest
that quantum information theory come to play a fundamental role in
understanding quantum gravity. Cosmology, on the other hand, plays a
significant role in testing quantum gravity effects. How to apply this idea to
a realistic universe is still missing. Here we show some concepts in quantum
information theory have their cosmological descriptions. Particularly, we show
complexity of a tensor network can be regarded as a Fisher information
measure(FIM) of a dS universe, followed by several observations: (i) the
holographic entanglement entropy has a tensor-network description and admits a
information-theoretical interpretation, (ii) on-shell action of dS spacetime
has a same description of FIM, (iii) complexity/action(CA) duality holds for dS
spacetime. Our result is also valid for gravity, whose FIM exhibits the
same features of a recent proposed norm complexity.Comment: 18 pages, 3 figures. v2: improvements to presentation, fixes typos
and matches published versio
Dependence of Temporal Properties on Energy in Long-Lag, Wide-Pulse Gamma-Ray Bursts
We employed a sample compiled by Norris et al. (2005, ApJ, 625, 324) to study
the dependence of the pulse temporal properties on energy in long-lag,
wide-pulse gamma-ray bursts. Our analysis shows that the pulse peak time, rise
time scale and decay time scale are power law functions of energy, which is a
preliminary report on the relationships between the three quantities and
energy. The power law indexes associated with the pulse width, rise time scale
and decay time scale are correlated and the correlation between the indexes
associated with the pulse width and the decay time scale is more obvious. In
addition, we have found that the pulse peak lag is strongly correlated with the
CCF lag, but the centroid lag is less correlated with the peak lag and CCF lag.
Based on these results and some previous investigations, we tend to believe
that all energy-dependent pulse temporal properties may come from the joint
contribution of both the hydrodynamic processes of the outflows and the
curvature effect, where the energy-dependent spectral lag may be mainly
dominated by the dynamic process and the energy-dependent pulse width may be
mainly determined by the curvature effect.Comment: 20 pages, 7 figures, added references, matched to published version,
accepted for publication in PAS
Characteristics of profiles of gamma-ray burst pulses associated with the Doppler effect of fireballs
In this paper, we derive in a much detail the formula of count rates, in
terms of the integral of time, of gamma-ray bursts in the framework of
fireballs, where the Doppler effect of the expanding fireball surface is the
key factor to be concerned. Effects arising from the limit of the time delay
due to the limited regions of the emitting areas in the fireball surface and
other factors are investigated. Our analysis shows that the formula of the
count rate of fireballs can be expressed as a function of which is the
observation time scale relative to the dynamical time scale of the fireball.
The profile of light curves of fireballs depends only on the relative time
scale, entirely independent of the real time scale and the real size of the
objects. It displays in detail how a cutoff tail, or a turn over, feature
(called a cutoff tail problem) in the decay phase of a light curve can be
formed. This feature is a consequence of a hot spot in the fireball surface,
moving towards the observer, and was observed in a few cases previously. By
performing fits to the count rate light curves of six sample sources, we show
how to obtain some physical parameters from the observed profile of the count
rate of GRBs. In addition, the analysis reveals that the Doppler effect of
fireballs could lead to a power law relationship between the of pulses
and energy, which were observed previously by many authors.Comment: 38 pages, 10 figures; accepted for publication in ApJ (10 December
2004, v617
The signal transduction pathway of PKC/NF-κB/c-fos may be involved in the influence of high glucose on the cardiomyocytes of neonatal rats
<p>Abstract</p> <p>Background</p> <p>High glucose could induce structure and function change in cardiomyocytes, PKC plays a core effect in the onset and progression of diabetic cardiomyopathy, but its underlying downstream signal transduction pathway is still not completely understood.</p> <p>Objectives</p> <p>To study the influence of high glucose on the structure, function and signal transduction pathway of PKC (Protein Kinase C)/NF-κB(Nuclear factor-κB)/c-fos in cultured cardiomyocytes.</p> <p>Methods</p> <p>Using cultured cardiomyocytes of neonatal Sprague-Dawley rats as a model, groups were divided into: control group (glucose: 5 mmol/L); high glucose group (glucose: 10 mmol/L, 15 mmol/L, 20 mmol/L, 25.5 mmol/L); equimolar mannital group (5 mmol/L glucose + 20.5 mmol/L maninital); high glucose(25.5 mmol/L) add PKC inhibitor (Ro-31-8220, 50 nmol/L); high glucose (25.5 mmol/L) add NF-κB inhibitor (BAY11-7082, 5 μmol/L). The cellular contracting frequency and volumes were measured and the expression of PKC-α, PKC-β2, p-PKC-α, p-PKC-β2, NF-κB, p-NF-κB, TNF-α (tumor necrosis factor-α) and c-fos were measured by western blot or RT-PCR.</p> <p>Results</p> <p>Cardiomyocytes cultured in high glucose level, but not iso-osmotic mannital, showed an increased pulsatile frequency and higher cellular volumes consistent with the increased glucose levels, and also higher expression of PKC-α, PKC-β2, p-PKC-α, p-PKC-β2, NF-κB, p-NF-κB, TNF-α and c-fos. The addition of Ro-31-8220 and BAY11-7082 could partly reverse these changes induced by high glucose level.</p> <p>Conclusion</p> <p>High glucose significantly increased the pulsatile frequency and cellular volumes of cultured cardiomyocytes via PKC/NF-κB/c-fos pathway, which might lead to diabetic cardiomyopathy.</p
Validity of the “Streitberger” Needle in a Chinese Population with Acupuncture: A Randomized, Single-Blinded, and Crossover Pilot Study
We studied the validity of a “Streitberger” needle as a valid approach in a Chinese population with experience of acupuncture. Volunteers were recruited from students of the School of Acupuncture and Moxibustion, Guangzhou University of Chinese Medicine. Sixty students receiving education in acupuncture theory and experience in practical acupuncture were tested in study determining whether needling with the placebo needle felt any different from conventional acupuncture. Outcomes included measures of penetration sensation, VAS ratings, and Deqi sensation questionnaire. As a result, needle penetration, VAS ratings for either needle and Deqi sensation were not significantly different between two kinds of needles. Our findings show that the use of “Streitberger” needle is credible in a Chinese population with acupuncture experience
Silicon nitride metalenses for unpolarized high-NA visible imaging
As one of nanoscale planar structures, metasurface has shown excellent
superiorities on manipulating light intensity, phase and/or polarization with
specially designed nanoposts pattern. It allows to miniature a bulky optical
lens into the chip-size metalens with wavelength-order thickness, playing an
unprecedented role in visible imaging systems (e.g. ultrawide-angle lens and
telephoto). However, a CMOS-compatible metalens has yet to be achieved in the
visible region due to the limitation on material properties such as
transmission and compatibility. Here, we experimentally demonstrate a divergent
metalens based on silicon nitride platform with large numerical aperture
(NA~0.98) and high transmission (~0.8) for unpolarized visible light,
fabricated by a 695-nm-thick hexagonal silicon nitride array with a minimum
space of 42 nm between adjacent nanoposts. Nearly diffraction-limit virtual
focus spots are achieved within the visible region. Such metalens enables to
shrink objects into a micro-scale size field of view as small as a single-mode
fiber core. Furthermore, a macroscopic metalens with 1-cm-diameter is also
realized including over half billion nanoposts, showing a potential application
of wide viewing-angle functionality. Thanks to the high-transmission and
CMOS-compatibility of silicon nitride, our findings may open a new door for the
miniaturization of optical lenses in the fields of optical fibers,
microendoscopes, smart phones, aerial cameras, beam shaping, and other
integrated on-chip devices.Comment: 16 pages, 7 figure
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