1,129 research outputs found
Evidence for trans-cis isomerization of the p-coumaric acid chromophore as the photochemical basis of the photocycle of photoactive yellow protein
AbstractAnalysis of the chromophore p-courmaix acid, extracted from the ground state and the long-lived blue-shifted photocycle intermediate of photoactive yellow protein, shows that the chromophore is reversibly converted from the trans to the cis configuration, while progressing through the photocycle. The detection of the trans and cis isomers was carried out by high performance capillary zone electrophoresis and further substained by 1H NMR spectroscopy. The data presented here establish the photo-isomerization of the vinyl double bond in the chromophore yellow protein, a eubacterial photosensory protein. A similar isomerization process occurs in the structurally very different sensory rhodopsins, offering an explanation for the strong spectroscopic similarities between photoactive yellow protein and the sensory rhodopsins. This is the first demonstration of light-induced isomerization of a chromophore double bond as the photochemical basis for photosensing in the domain of Bacteria
Shape and blocking effects on odd-even mass differences and rotational motion of nuclei
Nuclear shapes and odd-nucleon blockings strongly influence the odd-even
differences of nuclear masses. When such effects are taken into account, the
determination of the pairing strength is modified resulting in larger pair
gaps. The modified pairing strength leads to an improved self-consistent
description of moments of inertia and backbending frequencies, with no
additional parameters.Comment: 7 pages, 3 figures, subm to PR
New Lump-like Structures in Scalar-field Models
In this work we investigate lump-like solutions in models described by a
single real scalar field. We start considering non-topological solutions with
the usual lump-like form, and then we study other models, where the bell-shape
profile may have varying amplitude and width, or develop a flat plateau at its
top, or even induce a lump on top of another lump. We suggest possible
applications where these exotic solutions might be used in several distinct
branches of physics.Comment: REvTex4, twocolumn, 10 pages, 9 figures; new reference added, to
appear in EPJ
Mass Parameterizations and Predictions of Isotopic Observables
We discuss the accuracy of mass models for extrapolating to very asymmetric
nuclei and the impact of such extrapolations on the predictions of isotopic
observables in multifragmentation. We obtain improved mass predictions by
incorporating measured masses and extrapolating to unmeasured masses with a
mass formula that includes surface symmetry and Coulomb terms. We find that
using accurate masses has a significant impact on the predicted isotopic
observables.Comment: 12 pages, 4 figure
Triggering an eruptive flare by emerging flux in a solar active-region complex
A flare and fast coronal mass ejection originated between solar active
regions NOAA 11514 and 11515 on July 1, 2012 in response to flux emergence in
front of the leading sunspot of the trailing region 11515. Analyzing the
evolution of the photospheric magnetic flux and the coronal structure, we find
that the flux emergence triggered the eruption by interaction with overlying
flux in a non-standard way. The new flux neither had the opposite orientation
nor a location near the polarity inversion line, which are favorable for strong
reconnection with the arcade flux under which it emerged. Moreover, its flux
content remained significantly smaller than that of the arcade (approximately
40 %). However, a loop system rooted in the trailing active region ran in part
under the arcade between the active regions, passing over the site of flux
emergence. The reconnection with the emerging flux, leading to a series of jet
emissions into the loop system, caused a strong but confined rise of the loop
system. This lifted the arcade between the two active regions, weakening its
downward tension force and thus destabilizing the considerably sheared flux
under the arcade. The complex event was also associated with supporting
precursor activity in an enhanced network near the active regions, acting on
the large-scale overlying flux, and with two simultaneous confined flares
within the active regions.Comment: Accepted for publication in Topical Issue of Solar Physics: Solar and
Stellar Flares. 25 pages, 12 figure
Comparisons of Statistical Multifragmentation and Evaporation Models for Heavy Ion Collisions
The results from ten statistical multifragmentation models have been compared
with each other using selected experimental observables. Even though details in
any single observable may differ, the general trends among models are similar.
Thus these models and similar ones are very good in providing important physics
insights especially for general properties of the primary fragments and the
multifragmentation process. Mean values and ratios of observables are also less
sensitive to individual differences in the models. In addition to
multifragmentation models, we have compared results from five commonly used
evaporation codes. The fluctuations in isotope yield ratios are found to be a
good indicator to evaluate the sequential decay implementation in the code. The
systems and the observables studied here can be used as benchmarks for the
development of statistical multifragmentation models and evaporation codes.Comment: To appear on Euorpean Physics Journal A as part of the Topical Volume
"Dynamics and Thermodynamics with Nuclear Degrees of Freedo
Exponential Ergodicity of stochastic Burgers equations driven by -stable processes
In this work, we prove the strong Feller property and the exponential
ergodicity of stochastic Burgers equations driven by -subordinated
cylindrical Brownian motions with . To prove the results, we
truncate the nonlinearity and use the derivative formula for SDEs driven by
-stable noises established in Zhang (arXiv:1204.2630v2).Comment: 17p
Isospin Effects in Nuclear Multifragmentation
We develop an improved Statistical Multifragmentation Model that provides the
capability to calculate calorimetric and isotopic observables with precision.
With this new model we examine the influence of nuclear isospin on the fragment
elemental and isotopic distributions. We show that the proposed improvements on
the model are essential for studying isospin effects in nuclear
multifragmentation. In particular, these calculations show that accurate
comparisons to experimental data require that the nuclear masses, free energies
and secondary decay must be handled with higher precision than many current
models accord.Comment: 46 pages, 16 figure
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
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