135,863 research outputs found
An Implication on the Pion Distribution Amplitude from the Pion-Photon Transition Form Factor with the New BABAR Data
The new BABAR data on the pion-photon transition form factor arouses people's
new interests on the determination of pion distribution amplitude. To explain
the data, we take both the leading valence quark state's and the non-valence
quark states' contributions into consideration, where the valence quark part up
to next-to-leading order is presented and the non-valence quark part is
estimated by a phenomenological model based on its limiting behavior at both
and . Our results show that to be consistent with the
new BABAR data at large region, a broader other than the asymptotic-like
pion distribution amplitude should be adopted. The broadness of the pion
distribution amplitude is controlled by a parameter . It has been found that
the new BABAR data at low and high energy regions can be explained
simultaneously by setting to be around 0.60, in which the pion distribution
amplitude is closed to the Chernyak-Zhitnitsky form.Comment: 19 pages, 6 figures, 2 tables. Slightly changed, references updated.
To be published in Phys.Rev.
Hamiltonian formalism of the DNLS equation with nonvanished boundary value
Hamiltonian formalism of the DNLS equation with nonvanishing boundary value
is developed by the standard procedure.Comment: 11 page
Comparison of wind and turbulence measurements from Doppler lidar and instrumented aircraft
Wind fields were measured with the ground based lidar, NOAA Wave Propagation Laboratory and with the NASA B-57B instrumented aircraft. The remotely sensed winds are compared with the in situ aircraft measurements. Three flight plans were carried out during the two different field programs. At NASA/MSFC the aircraft circled while the lidar scanned conically and the aircraft flew 6 deg approach path along the fixed lidar beam. The aircraft flew an approach along the lidar beam directed south-north (parallel to the mountain range) and a climbout along the lidar beam which alternately shifted east-west (perpendicular to the mountain range). Turbulence intensities and spectra were calculated from the temporal fluctuations in the lidar-measured radial wind speed component. These field tests provided unique sets of data to examine the mean wind and turbulence measurements made by remote sensing instruments. The comparison of aircraft measured turbulence intensities and spectra with lidar time histories of radial wind speed were in good agreement
Heterogeneous responses of dorsal root ganglion neurons in neuropathies induced by peripheral nerve trauma and the antiretroviral drug stavudine
Ā© 2014 The Authors. European Journal of Pain published by John Wiley & Sons Ltd on behalf of European Pain Federation - EFICĀ®. Funding sources E.K.B. was funded by a BBSRC PhD studentship. A.N., A.S.C.R. and T.P. were funded by a Wellcome Trust Strategic Award (London Pain Consortium; ref. 083259). A.S.C.R. and W.H. were funded by the Innovative Medicines Initiative Joint Undertaking (Europain; grant agreement no. 115007). We thank Pfizer for providing stavudine. Conflicts of interest None declared. Funded by BBSRC PhD studentship Wellcome Trust Strategic Award. Grant Number: 083259 Innovative Medicines Initiative Joint Undertaking. Grant Number: 115007Peer reviewedPublisher PD
Spin Chain with Magnetic Field and Spinning String in Magnetic Field Background
We analyze the fast-moving string in the magnetic Melvin field background and
find that the associated effective Lagrangian of string sigma model describes
the spin chain model with external magnetic field. The spin vector in the spin
chain has been properly deformed and is living on the deformed two-sphere or
deformed two-dimensional hyperboloid, depending on the direction around which
the string is spinning. We describe in detail the characters of spin
deformation and, in particular, see that this is a general property for a
string moving in a class of deformed background.Comment: Latex 10 pages, add a figure and a section, change titl
Secondary Rayleigh-Taylor type Instabilities in the Reconnection Exhaust Jet as a Mechanism for Supra-Arcade Downflows
Supra-arcade downflows (hereafter referred to as SADs) are low-emission,
elongated, finger-like features usually observed in active-region coronae above
post-eruption flare arcades. Observations exhibit downward moving SADs
intertwined with bright upward moving spikes. Whereas SADs are dark voids,
spikes are brighter, denser structures. Although SADs have been observed for
decades, the mechanism of formation of SADs remains an open issue. In our
three-dimensional resistive magnetohydrodynamic simulations, we demonstrate
that secondary Rayleigh-Taylor type instabilities develop in the downstream
region of a reconnecting current sheet. The instability results in the
formation of low-density coherent structures that resemble SADs, and
high-density structures that appear to be spike-like. Comparison between the
simulation results and observations suggests that secondary Rayleigh-Taylor
type instabilities in the exhaust of reconnecting current sheets provide a
plausible mechanism for observed SADs and spikes
Temperature, light and nitrate sensing coordinate Arabidopsis seed dormancy cycling resulting in winter and summer annual phenotypes
Seeds use environmental cues to sense the seasons and their surroundings to initiate the plants life cycle. Dormancy cycling underlying this process is extensively described, but the molecular mechanism is largely unknown. To address this we selected a range of representative genes from published array experiments in the laboratory and investigated their expression patterns in seeds of Arabidopsis ecotypes, having contrasting life cycles, over an annual dormancy cycle in the field. We show how mechanisms identified in the laboratory are coordinated in response to the soil environment to determine dormancy cycles that result in winter and summer annual phenotypes. Our results are consistent with a seed specific response to seasonal temperature patterns (temporal sensing) involving the gene DELAY OF GERMINATION1 (DOG1) that indicates the correct season; and concurrent temporally driven co-opted mechanisms that sense spatial signals i.e. nitrate via CBL-INTERACTING PROTEIN KINASE 23 (CIPK23) phosphorylation of the NITRATE TRANSPORTER 1 (NRT1.1) and light via PHYTOCHROME A (PHYA). In both ecotypes studied, when all three genes have low expression there is enhanced GIBBERELLIN 3 BETA-HYDROXYLASE 1 (GA3ox1) expression, exhumed seeds have the potential to germinate in the laboratory, and the initiation of seedling emergence occurs following soil disturbance (exposure to light) in the field. Unlike DOG1, expression of MOTHER of FLOWERING TIME (MFT) has an opposite thermal response in seeds of the two ecotypes indicating a role in determining their different dormancy cycling phenotypes
Physical Parameters Of The Relativistic Shock Waves In GRBs: The Case Of 30 GRBs
Using the modified internal shock wave model we fit the gamma ray burst (GRB)
light and spectral curves of 30 GRBs observed with BATSE. From the best fitting
we obtain basic parameters of the relativistic shells which are in good
agreement with predictions given earlier. We compare measured GRB parameters
with those obtained from the model and discuss connections between them in the
frame of the physical processes laying behind GRB events.Comment: 18 pages, 30 figures, 2 tables, Accepted for publication in IJMP
Transition Temperature of a Uniform Imperfect Bose Gas
We calculate the transition temperature of a uniform dilute Bose gas with
repulsive interactions, using a known virial expansion of the equation of
state. We find that the transition temperature is higher than that of an ideal
gas, with a fractional increase K_0(na^3)^{1/6}, where n is the density and a
is the S-wave scattering length, and K_0 is a constant given in the paper. This
disagrees with all existing results, analytical or numerical. It agrees exactly
in magnitude with a result due to Toyoda, but has the opposite sign.Comment: Email correspondence to [email protected] ; 2 pages using REVTe
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