35,148 research outputs found
Human Bipedalism, Evolved from Arboreal Locomotion of Two-arm Brachiation
Among all kinds of apes, only gibbons have the slim body as human. Gibbons
can move in the forest by cross arm swing, what was the locomotion mode of our
arboreal ancestor. Since our ancestor had much heavier body but weaker arms
than gibbons, we suppose they had to move with two arm brachiation. Such mode
of locomotion can account reasonably for the transition to bipedalism. Firstly,
it needed our ancestor to straighten knee and hip joints and flex their lumbar
spine. secondly, it evolved the feet of our ancestor with longitudinal arche.
And most importantly, it made the ratio of the length of the upper limbs to
that of the lower limbs unsuitable for quadruped walking.Comment: 10 pages, 4 figure
Configuration mixing effects in neutron-rich carbon isotopes
Shell model calculations are done to study the structure of neutron-rich
carbon isotopes. For both even-A and odd-A neutron-rich carbon isotopes, the
energy levels are strongly affected by the configuration mixing of valence
neutrons. The calculated energy levels in the nucleus C are
significantly improved compared with experimental values when the model space
of the three valence neutrons is enlarged from pure
configuration to full space. We also investigate the configuration mixing
effect on the values in even-even nuclei C
Resonant parameters of the
The vector charmoniumlike state was reported recently in the cross
sections of , , ,
and measured by the BESIII experiment. A combined fit
is performed to the cross sections of these four final states to extract the
resonant parameters of the . We determine a mass ~MeV/ and a total width ~MeV for the
, where the first uncertainties are statistical and the second ones
systematic. Assuming the decays dominantly to the above four modes
and their isospin symmetric modes, we also estimate its leptonic decay width
and decay branching fractions. These information is essential for the
understanding of the nature of this state.Comment: 10 pages, 2 figures, 1 table, accepted for publication in Physical
Review
Determination of the relative phase in \psi' and J/\psi\ decays into baryon and antibaryon
With the recent measurements of psi' and J/psi decay into octet-baryon pairs,
we study the relative phase between the strong and the electromagnetic
amplitudes, and find a large phase by fitting the present data. The fits take
into account the details of experimental effects, including energy spread and
initial state radiation. We also predict some branching fractions of psi'
decays and the continuum production rates at the J/psi mass based on the
relative phase and absolute amplitudes obtained from the fits.Comment: 13 page
Study of the Rho-pi Puzzle in Charmonium Decays
The theoretical explanations about the ``Rho-pi puzzle'' in charmonium decays
are reviewed extensively, and the comparison of theoretical predications with
experimental data is made whenever possible. Three methods to estimate the
ratio of the branching fractions of J/psi and psi' decays are also discussed.
It is pointed out that in order to understand the Rho-pi puzzle, and the
dynamics of charmonium decays, systematic studies should be made in theory,
phenomenology and experiment aspects.Comment: 13 page
Multiple solutions in extracting physics information from experimental data
Multiple solutions exist in various experimental situations whenever the sum
of several amplitudes is used to fit the experimentally measured distributions,
such as the cross section, the mass spectrum, or the angular distribution. We
show a few examples where multiple solutions were found, while only one
solution was reported in the publications. Since there is no existing rules
found in choosing any one of these solutions as the physics one, we propose a
simple rule which agrees with what have been adopted in previous literatures:
the solution corresponding to the minimal magnitudes of the amplitudes must be
the physical solution. We suggest test this rule in the future experiments.Comment: 10 pages, 3 figure
Experimental demonstration of a quantum router
The router is a key element for a network. We describe a scheme to realize
genuine quantum routing of single-photon pulses based on cascading of
conditional quantum gates in a Mach-Zehnder interferometer and report a
proof-of-principle experiment for its demonstration using linear optics quantum
gates. The polarization of the control photon routes in a coherent way the path
of the signal photon while preserving the qubit state of the signal photon
represented by its polarization. We demonstrate quantum nature of this router
by showing entanglement generated between the initially unentangled control and
signal photons, and confirm that the qubit state of the signal photon is well
preserved by the router through quantum process tomography
Possible determination of high-lying single particle components with (p,d) reactions
A detailed feasibility study on deducing the high-lying single-particle
components (HLSPCs), which are important but used to be ignored, in the ground
and low-lying excited states of even-even light nuclei is performed by analyses
of reactions with \nuc{12}{C}, \nuc{24}{Mg}, \nuc{28}{Si}, and
\nuc{40}{Ca} targets at 51.93 MeV. Coupled reaction channels (CRC) analyses
have been made for transitions to the -forbidden excited states in
\nuc{11}{C} (, 4.32 MeV), \nuc{23}{Mg} (,
2.05 MeV), \nuc{27}{Si} (, 2.16 MeV) and \nuc{39}{Ca}
(, 3.64 MeV), including the major allowed transition
components together with direct components of HLSPCs. Spectroscopic amplitudes
of the HLSPCs are deduced by fitting the angular distributions of the ground
and the -forbidden excited states simultaneously. The present analysis
demonstrates for the first time that information about HLSPCs in atomic nuclei
can be obtained from analysis of reactions.Comment: 7 pages, 5 figure
Binding-energy independence of reduced single particle strengths derived from reactions
An overall reduction factor (ORF) is introduced for studying the quenching of
single particle strengths through nucleon transfer reactions. The ORF includes
contributions of all the probed bound states of the residual nucleus in a
transfer reaction and permits a proper comparison with results of inclusive
knockout reactions. A systematic analysis is made with 103 sets of angular
distribution data of reactions on 21 even-even targets with atomic mass
numbers from 8 to 56 using the consistent three-body model reaction methodology
proposed in [J. Lee, J.A. Tostevin, B.A. Brown, et al., Phys. Rev. C 73, 044608
(2006)]. The extracted ORFs are found to be nearly independent on the nuclear
isospin asymmetry, which is different from the systematics of inclusive
knockout reactions but is consistent with the recent measurement of ,
, , and reactions on nitrogen and oxygen isotopes and
\textit{ab initio} calculations.Comment: 15 pages, 3 figure
Possible Phase Separation and Transport Properties in Large Superconducting Ca0.77La0.18Fe0.90As2 Crystals
We synthesized large superconducting single crystal Ca0.77La0.18Fe0.90As2
('112' type) of 2 millimeter size. Scanning electron microscopy (SEM)
measurements revealed that bright and dark stripes alternately spread on the
surface of crystals, indicating possible existence of intrinsic phase
separation. Temperature (T) -dependent resistivity, Hall effect and
magneto-resistance (MR) were measured with magnetic field (H) applied to
different directions of crystal. The upper critical field (Hc2) anisotropy was
estimated with a moderate value around 2.8. Positive Hall coefficient (RH) and
anisotropic MR were found and showed strong T-dependent feature. Below T about
100 K, abnormal behaviors appear simultaneously in resistivity derivative, Hall
coefficient and MR, which indicates that other scattering mechanisms more than
conventional multiband effect may exist.Comment: This paper has been withdrawn by the author due to a crucial sign
error of the Hall coefficien
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