603 research outputs found
Isospin and a possible interpretation of the newly observed X(1576)
Recently, the BES collaboration observed a broad resonant structure X(1576)
with a large width being around 800 MeV and assigned its number to
. We show that the isospin of this resonant structure should be
assigned to 1. This state might be a molecule state or a tetraquark state. We
study the consequences of a possible - molecular
interpretation. In this scenario, the broad width can easily be understood. By
using the data of , the branching
ratios and are further estimated in this molecular
state scenario. It is shown that the decay mode should have a
much larger branching ratio than the decay mode has. As a
consequence, this resonant structure should also be seen in the and processes, especially in
the former process. Carefully searching this resonant structure in the
and decays should
be important for understanding the structure of X(1567).Comment: 5 pages, ReVTeX4, 3 figures. Version accepted for publication as a
brief report in Phys. Rev.
Comment on " a unified scheme for flavored mesons and baryons"
We would comment on the results of the paper "a unified scheme for flavored
mesons and baryons" (P.C.Vinodkumar, J.N.Panandya, V.M.Bannur, and
S.B.Khadkikar Eur. Phys. J. A4(1999)83), and point out some inconsistencies and
mistakes in the work for solving the Dirac equation. In terms of an example for
a single particle we investigate the reliability of the perturbative method for
computing the Coulomb energy and discuss the contribution to the wavefunction
at origin from the Coulomb potential. We conclude that the accuracy of their
numerical results needs to be reconsidered.Comment: Latex file, 11page
Comparison of gold- and graphene-based resonant nano-structures for terahertz metamaterials and an ultra-thin graphene-based modulator
Graphene exhibits unique material properties and in electromagnetic wave
technology, it raises the prospect of devices miniaturized down to the atomic
length scale. Here we study split-ring resonator metamaterials made from
graphene and we compare them to gold-based metamaterials. We find that
graphene's huge reactive response derived from its large kinetic inductance
allows for deeply subwavelength resonances, although its resonance strength is
reduced due to higher dissipative loss damping and smaller dipole coupling.
Nevertheless, tightly stacked graphene rings may provide for negative
permeability and the electric dipole resonance of graphene meta-atoms turns out
to be surprisingly strong. Based on these findings, we present a terahertz
modulator based on a metamaterial with a multi-layer stack of alternating
patterned graphene sheets separated by dielectric spacers. Neighbouring
graphene flakes are biased against each other, resulting in modulation depths
of over 75% at a transmission level of around 90%.Comment: 16 pages, 5 figure
Protecting the Aging Retina
Aging retina, notably the aging macula, is prone to develop degenerative diseases, such as age-related macular degeneration (AMD), the leading cause of visual loss in individuals aged 65 or above in developed countries. However, current treatments are very limited. Since degeneration, dysfunction, and death of retinal neurons are demonstrated in the pathogenesis of AMD, neuroprotective strategies could serve as a possible way to treat AMD. In this chapter, we will briefly introduce risk factors, pathophysiology, affected neurons, classification, clinical manifestation, and current treatments of AMD. Finally, neuroprotection in both AMD animal models and patients will be discussed
Lutein and the Aging Eye
Lutein is a carotenoid highly concentrated in the macula of the retina. Lutein cannot be synthesized and must be supplied in the diet, for example, dark green leafy vegetable and egg yolk. Lutein is believed to absorb blue light, leading to the protection of retina from light-related damage. It can also protect the retina against oxidative stress and inflammation. In fact, dietary and supplementary lutein have been shown to be associated with possible reduced risk of age-related macular degeneration, a leading cause of elderly blindness, attributed largely to lutein’s antioxidant properties. Lutein is also beneficial as a nutritional supplement in preventing diabetic retinopathy. Moreover, lutein is very safe and widely used. In this chapter, we will discuss the basic chemistry of lutein; its uptake, transport, distribution, and functions in the normal eye. Lastly, the effects of lutein in age-related eye diseases will be summarized
- …