2,604 research outputs found
Dependence of quantum correlations of twin beams on pump finesse of optical parametric oscillator
The dependence of quantum correlation of twin beams on the pump finesse of an
optical parametric oscillator is studied with a semi-classical analysis. It is
found that the phase-sum correlation of the output signal and idler beams from
an optical parametric oscillator operating above threshold depends on the
finesse of the pump field when the spurious pump phase noise generated inside
the optical cavity and the excess noise of the input pump field are involved in
the Langevin equations. The theoretical calculations can explain the previously
experimental results, quantitatively.Comment: 27 pages, 8 figure
Comparing the performance of FA, DFA and DMA using different synthetic long-range correlated time series
Notwithstanding the significant efforts to develop estimators of long-range
correlations (LRC) and to compare their performance, no clear consensus exists
on what is the best method and under which conditions. In addition, synthetic
tests suggest that the performance of LRC estimators varies when using
different generators of LRC time series. Here, we compare the performances of
four estimators [Fluctuation Analysis (FA), Detrended Fluctuation Analysis
(DFA), Backward Detrending Moving Average (BDMA), and centred Detrending Moving
Average (CDMA)]. We use three different generators [Fractional Gaussian Noises,
and two ways of generating Fractional Brownian Motions]. We find that CDMA has
the best performance and DFA is only slightly worse in some situations, while
FA performs the worst. In addition, CDMA and DFA are less sensitive to the
scaling range than FA. Hence, CDMA and DFA remain "The Methods of Choice" in
determining the Hurst index of time series.Comment: 6 pages (including 3 figures) + 3 supplementary figure
Hominin-specific regulatory elements selectively emerged in oligodendrocytes and are disrupted in autism patients
Speciation is associated with substantial rewiring of the regulatory circuitry underlying the expression of genes. Determining which changes are relevant and underlie the emergence of the human brain or its unique susceptibility to neural disease has been challenging. Here we annotate changes to gene regulatory elements (GREs) at cell type resolution in the brains of multiple primate species spanning most of primate evolution. We identify a unique set of regulatory elements that emerged in hominins prior to the separation of humans and chimpanzees. We demonstrate that these hominin gains perferentially affect oligodendrocyte function postnatally and are preferentially affected in the brains of autism patients. This preference is also observed for human-specific GREs suggesting this system is under continued selective pressure. Our data provide a roadmap of regulatory rewiring across primate evolution providing insight into the genomic changes that underlie the emergence of the brain and its susceptibility to neural disease
A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift
We have compiled a catalog of optically-selected quasars with simultaneous
observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst
Explorer. Objects in this catalog are identified by matching the Swift
pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The
final catalog contains 843 objects, among which 637 have both UVOT and XRT
observations and 354 of which are detected by both instruments. The overall
X-ray detection rate is ~60% which rises to ~85% among sources with at least 10
ks of XRT exposure time. We construct the time-averaged spectral energy
distribution for each of the 354 quasars using UVOT photometric measurements
and XRT spectra. From model fits to these SEDs, we find that the big blue bump
contributes about 0.3 dex to the quasar luminosity. We re-visit the
alpha_ox-L_uv relation by selecting a clean sample with only type 1 radio-quiet
quasars; the dispersion of this relation is reduced by at least 15% compared to
studies that use non-simultaneous UV/optical and X-ray data. We only found a
weak correlation between L/L_Edd and alpha_uv. We do not find significant
correlations between alpha_x and alpha_ox, alpha_ox and alpha_uv, and alpha_x
and Log L(0.3-10 keV). The correlations between alpha_uv and alpha_x, alpha_ox
and alpha_x, alpha_ox and alpha_uv, L/L_Edd and alpha_x, and L/L_Edd and
alpha_ox are stronger amongst low-redshift quasars, indicating that these
correlations are likely driven by the changes of SED shape with accretion
state.Comment: 63 pages, 22 figures, accepted by ApJ
Magnetotransport in the Normal State of La1.85Sr0.15Cu(1-y)Zn(y)O4 Films
We have studied the magnetotransport properties in the normal state for a
series of La1.85Sr0.15Cu(1-y)Zn(y)O4 films with values of y, between 0 and
0.12. A variable degree of compressive or tensile strain results from the
lattice mismatch between the substrate and the film, and affects the transport
properties differently from the influence of the zinc impurities. In
particular, the orbital magnetoresistance (OMR) varies with y but is
strain-independent. The relations for the resistivity and the Hall angle and
the proportionality between the OMR and tan^2 theta are followed about 70 K. We
have been able to separate the strain and impurity effects by rewriting the
above relations, where each term is strain-independent and depends on y only.
We also find that changes in the lattice constants give rise to closely the
same fractional changes in other terms of the equation.The OMR is more strongly
supressed by the addition of impurities than tan^2 theta. We conclude that the
relaxation ratethat governs Hall effect is not the same as for the
magnetoresistance. We also suggest a correspondence between the transport
properties and the opening of the pseudogap at a temperature which changes when
the La-sr ratio changes, but does not change with the addition of the zinc
impurities
Search for psi(3770)\ra\rho\pi at the BESII detector at the Beijing Electron-Positron Collider
Non- decay \psppto \rhopi is searched for using a data sample of
taken at the center-of-mass energy of 3.773 GeV by the
BESII detector at the BEPC. No \rhopi signal is observed, and the upper limit
of the cross section is measured to be \sigma(\EETO \rhopi)<6.0 pb at 90% C.
L. Considering the interference between the continuum amplitude and the \pspp
resonance amplitude, the branching fraction of \pspp decays to is
determined to be \BR(\pspp\ra\rho\pi)\in(6.0\times10^{-6}, 2.4\times10^{-3})
at 90% C. L. This is in agreement with the prediction of the - and -wave
mixing scheme of the charmonium states for solving the ``\rhopi puzzle''
between \jpsi and \psp decays.Comment: 15 pages, 5 figure
Experimental study of decays to \K^+ K^- \pi^+ \pi^- \pi^0 final states
final states are studied using a sample of
decays collected with the Beijing Spectrometer
(BESII) at the Beijing Electron-Position Collider. The branching fractions of
decays to , , , , , and are determined. The first two agree with previous
measurements, and the last five are first measurements.Comment: 19 pages, 9 figure
The DArk Matter Particle Explorer mission
The DArk Matter Particle Explorer (DAMPE), one of the four scientific space
science missions within the framework of the Strategic Pioneer Program on Space
Science of the Chinese Academy of Sciences, is a general purpose high energy
cosmic-ray and gamma-ray observatory, which was successfully launched on
December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE
scientific objectives include the study of galactic cosmic rays up to
TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the
search for dark matter signatures in their spectra. In this paper we illustrate
the layout of the DAMPE instrument, and discuss the results of beam tests and
calibrations performed on ground. Finally we present the expected performance
in space and give an overview of the mission key scientific goals.Comment: 45 pages, including 29 figures and 6 tables. Published in Astropart.
Phy
Measurement of the cross section for e^+e^- -> ppbar at center-of-mass energies from 2.0 to 3.07 GeV
Cross sections for e^+e^- -> ppbar have been measured at 10 center-of-mass
energies from 2.0 to 3.07 GeV by the BESII experiment at the BEPC, and proton
electromagnetic form factors in the time-like region have been determined.Comment: 6 pages, 3 figure
Partial Wave Analysis of
A partial wave analysis of in
decay is presented using a sample of 14 million
events accumulated by the BES II detector. The data are fitted to
the sum of relativistic covariant tensor amplitudes for intermediate resonant
decay modes. From the fit, significant contributions to decays from
the channels , , ,
, , , and are found. Flavor-SU(3)-violating
asymmetry is observed. Values obtained for the masses and
widths of the resonances , , , and
are presented.Comment: 16 pages, 9 figures, and 4 table
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