25,015 research outputs found
The electromagnetic form factors of the proton in the timelike region
The reactions ppbar -> e+e- and e+e- -> ppbar are analyzed in the
near-threshold region. Specific emphasis is put on the role played by the
interaction in the initial- or final antinucleon-nucleon state which is taken
into account rigorously. For that purpose a recently published NNbar potential
derived within chiral effective field theory and fitted to results of a new
partial-wave analysis of ppbar scattering data is employed. Our results provide
strong support for the conjecture that the pronounced energy dependence of the
e+e- ppbar cross section, seen in pertinent experiments, is primarily due
to the ppbar interaction. Predictions for the proton electromagnetic form
factors G_E and G_M in the timelike region, close to the NNbar threshold, and
for spin-dependent observables are presented. The steep rise of the effective
form factor for energies close to the ppbar threshold is explained solely in
terms of the ppbar interaction. The corresponding experimental information is
quantitatively described by our calculation.Comment: 14 pages, 11 figure
Multipole Gravitational Lensing and High-order Perturbations on the Quadrupole Lens
An arbitrary surface mass density of gravitational lens can be decomposed
into multipole components. We simulate the ray-tracing for the multipolar mass
distribution of generalized SIS (Singular Isothermal Sphere) model, based on
the deflection angles which are analytically calculated. The magnification
patterns in the source plane are then derived from inverse shooting technique.
As have been found, the caustics of odd mode lenses are composed of two
overlapping layers for some lens models. When a point source traverses such
kind of overlapping caustics, the image numbers change by \pm 4, rather than
\pm 2. There are two kinds of images for the caustics. One is the critical
curve and the other is the transition locus. It is found that the image number
of the fold is exactly the average value of image numbers on two sides of the
fold, while the image number of the cusp is equal to the smaller one. We also
focus on the magnification patterns of the quadrupole (m = 2) lenses under the
perturbations of m = 3, 4 and 5 mode components, and found that one, two, and
three butterfly or swallowtail singularities can be produced respectively. With
the increasing intensity of the high-order perturbations, the singularities
grow up to bring sixfold image regions. If these perturbations are large enough
to let two or three of the butterflies or swallowtails contact, eightfold or
tenfold image regions can be produced as well. The possible astronomical
applications are discussed.Comment: 24 pages, 6 figure
Galaxy alignment on large and small scales
Galaxies are not randomly distributed across the universe but showing
different kinds of alignment on different scales. On small scales satellite
galaxies have a tendency to distribute along the major axis of the central
galaxy, with dependence on galaxy properties that both red satellites and
centrals have stronger alignment than their blue counterparts. On large scales,
it is found that the major axes of Luminous Red Galaxies (LRGs) have
correlation up to 30Mpc/h. Using hydro-dynamical simulation with star
formation, we investigate the origin of galaxy alignment on different scales.
It is found that most red satellite galaxies stay in the inner region of dark
matter halo inside which the shape of central galaxy is well aligned with the
dark matter distribution. Red centrals have stronger alignment than blue ones
as they live in massive haloes and the central galaxy-halo alignment increases
with halo mass. On large scales, the alignment of LRGs is also from the
galaxy-halo shape correlation, but with some extent of mis-alignment. The
massive haloes have stronger alignment than haloes in filament which connect
massive haloes. This is contrary to the naive expectation that cosmic filament
is the cause of halo alignment.Comment: 4 pages, 3 figures, To appear in the proceedings of the IAU Symposium
308 "The Zeldovich Universe: Genesis and Growth of the Cosmic Web
Extracting CP violation and strong phase in D decays by using quantum correlations in psi(3770)-> D0\bar{D}0 -> (V1V2)(V3V4) and psi(3770)->D0\bar{D}0 -> (V1V2)(K pi)
The charm quark offers interesting opportunities to cross-check the mechanism
of CP violation precisely tested in the strange and beauty sectors. In this
paper, we exploit the angular and quantum correlations in the D\bar{D} pairs
produced through the decay of the psi(3770) resonance in a charm factory to
investigate CP-violation in two different ways. We build CP-violating
observables in psi(3770) -> D\bar{D} -> (V_1V_2)(V_3 V_4) to isolate specific
New Physics effects in the charm sector. We also consider the case of psi(3770)
-> D\bar{D} -> (V_1V_2)(K\pi) decays, which provide a new way to measure the
strong phase difference delta between Cabibbo-favored and doubly-Cabibbo
suppressed D decays required in the determination of the CKM angle gamma.
Neglecting the systematics, we give a first rough estimate of the sensitivities
of these measurements at BES-III with an integrated luminosity of 20 fb^-1 at
psi(3770) peak and at a future Super tau-charm factory with a luminosity of
10^35 cm^-2.s^-1.Comment: 13 pages
Two-dimensional structures of ferroelectric domain inversion in LiNbO3 by direct electron beam lithography
We report on the fabrication of domain-reversed structures in LiNbO3 by means
of direct electron beam lithography at room temperature without any static
bias. The LiNbO3 crystals were chemically etched after the exposure of electron
beam and then, the patterns of domain inversion were characterized by atomic
force microscopy (AFM). In our experiment, an interesting phenomenon occurred
when the electron beam wrote a one-dimensional (1-D) grating on the negative
c-face: a two-dimensional (2-D) dotted array was observed on the positive c-
face, which is significant for its potential to produce 2-D and
three-dimensional photonic crystals. Furthermore, we also obtained 2-D
ferroelectric domain inversion in the whole LiNbO3 crystal by writing the 2-D
square pattern on the negative c-face. Such a structure may be utilized to
fabricate 2-D nonlinear photonic crystal. AFM demonstrates that a 2-D
domain-reversed structure has been achieved not only on the negative c-face of
the crystal, but also across the whole thickness of the crystal.Comment: 17 pages, 4 figure
Antioxidantactivity In Vitro And Hepatoprotective Effect Of Phlomis Maximowiczii In Vivo
Background: Anumber of medicinal plants and there compounds played a major role in the treatment of hepatic disorders. They were widely used for the treatment of these disorders, and oxidant stress injury was one of the liver injury mechanisms. The present study evaluated the antioxidant activity and the hepatoprotective effect of each extracts of Phlomis maximowiczii.Materials and Methods: The antioxidant activity was assayed by the methods of ABTS, FRAP and DPPH in vitro. Hepatoprotective effect of P. maximowiczii extracts was examined using carbon tetrachloride-induced acute liver injury in mice.Results: P. maximowiczii n-butanol (PMBU) extract, ABTS (IC50=18.96 μg/mL), DPPH (IC50=25.15 μg/mL), and FRAP (RACT50=2775.6±144.18 μmol/g), showed higher scavenging capacity than that of P. maximowiczii ethyl acetate (PMEA). The n-butanol extract could significantly reduce the level of GPT, GOT and MDA (P<0.05, P<0.001 and P<0.001, respectively) and increase the level of SOD (P<0.001), respectively.Conclusion: The antioxidant activity of n-butanol extract in vitro was related with the level ofMDAand SOD in vivo, and hepatoprotective effect of n-butanol extract also had relationship with its antioxidant activity in vivo.Key words: Phlomis maximowiczii, anti-oxidation, acute liver in jury, carbon tetrachloride
Adsorption/desorption and electrically controlled flipping of ammonia molecules on graphene
In this paper, we evaluate of the adsorption/ desorption of ammonia molecules
on a graphene surface by studying the Fermi level shift. Based on a physically
plausible model, the adsorption and desorption rates of ammonia molecules on
graphene have been extracted from the measured Fermi level shift as a function
of exposure time. An electric field-induced flipping behavior of ammonia
molecules on graphene is suggested, based on field effect transistor (FET)
measurements
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