1,603 research outputs found
On Neutralization of Charged Black Holes
For non-spinning, charged (Reissner–Nordström) black holes, the particles with an opposite sign of charge with respect to that of the black hole will be pulled into the black hole by the extra electromagnetic force. Such a hole will be quickly neutralized so that there should not exist significantly charged, non-spinning black holes in the universe. The case of spinning, charged (Kerr–Newmann, KN) black holes is more complicated. For a given initial position and initial velocity of the particle, an oppositely charged particle does not always more easily fall into the black hole than a neutral particle. The possible existence of a magnetosphere further complicate the picture. One therefore cannot straightforwardly conclude that a charged spinning black hole will be neutralized. In this paper, we make the first step to investigate the neutralization of KN black holes without introducing a magnetosphere. We track the particle trajectories under the influence of the curved space–time and the electromagnetic field carried by the spinning, charged black hole. A statistical method is used to investigate the neutralization problem. We find a universal dependence of the falling probability into the black hole on the charge of the test particle, with the oppositely charged particles having a higher probability of falling. We therefore conclude that charged, spinning black holes without a magnetosphere should be quickly neutralized, consistent with people’s intuition. The neutralization problem of KN black holes with a corotating force-free magnetosphere is subject to further studies
The Construction of a Williams Design and Randomization in Cross-Over Clinical Trials Using SAS
Local scale air pollution forecasting by artificial intelligence techniques and assess the pollution-related social effects
Since the air pollution can cause serious health problem, the concerns about forecasting air pollution timely
and accurately arise by researchers in order to alert the public avoiding high level pollution and help the
government make decisions. In our research, we take Hong Kong (finished research) and the cities in Mexico
(finishing) and Mainland China (starting), especially the high pollutant areas such as Mexico City and Beijing,
as study cases. Meanwhile, various types of artificial intelligence techniques are employed to achieve the goals. Furthermore, we also extent our research from forecast pollution to assess the air pollution – related social effects, for example health impact and its economic loss, which are also the concerned by public and the governments
Multifunctional Bracts in the Dove Tree Davidia involucrata (Nyssaceae:Cornales)
Although there has been much experimental work on floral traits that are under selection from mutualists and antagonists, selection by abiotic environmental factors on flowers has been largely ignored. Here we test whether pollen susceptibility to rain damage could have played a role in the evolution of the reproductive architecture of Davidia involucrata, an endemic in the mountains of western China. Flowers in this tree species lack a perianth and are arranged in capitula surrounded by large (up to 10 cm#5 cm) bracts that at anthesis turn from green to white, losing their photosynthetic capability. Flowers are nectarless, and pollen grains are presented on the recurved anther walls for 5–7 days. Flower visitors, and likely pollinators, were mainly pollen-collecting bees from the genera Apis, Xylocopa, Halictus, and Lasioglossum. Capitula with natural or white paper bracts attracted significantly more bees per hour than capitula that had their bracts removed or replaced by green paper. Experimental immersion of pollen grains in water resulted in rapid loss of viability, and capitula with bracts lost less pollen to rain than did capitula that had their bracts removed, suggesting that the bracts protect the pollen from rain damage as well as attracting pollinators
Applicability of the Friedberg-Lee-Zhao method
Friedberg, Lee and Zhao proposed a method for effectively evaluating the
eigenenergies and eigen wavefunctions of quantum systems. In this work, we
study several special cases to investigate applicability of the method.
Concretely, we calculate the ground-state eigenenergy of the Hellmann potential
as well as the Cornell potential, and also evaluate the energies of the systems
where linear term is added to the Coulomb and harmonic oscillator potentials as
a perturbation. The results obtained in this method have a surprising agreement
with the traditional method or the numerical results. Since the results in this
method have obvious analyticity compared to that in other methods, and because
of the simplicity for calculations this method can be applied to solving the
Schr\"{o}dinger equation and provides us better understanding of the physical
essence of the concerned systems. But meanwhile applications of the FLZ method
are restricted at present, especially for certain potential forms, but due to
its obvious advantages, it should be further developed.Comment: 14 pages,no figure
meson photoproduction in ultrarelativistic heavy ion collisions
The transverse momentum distributions for inclusive meson
described by gluon-gluon interactions from photoproduction processes in
relativistic heavy ion collisions are calculated. We considered the color
singlet (CS) and color octet (CO) components with the framework of
non-relativistic Quantum Chromodynamics (NRQCD) into the production of heavy
quarkonium. The phenomenological values of the matrix elements for the
color-singlet and color-octet components give the main contribution to the
production of heavy quarkonium from the gluon-gluon interaction caused by the
emission of additional gluon in the initial state. The numerical results
indicate that the contribution of photoproduction processes cannot be
negligible for mid-rapidity in p-p and Pb-Pb collisions at the Large Hadron
Collider (LHC) energies.Comment: 11 pages, 2 figure
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