3,453 research outputs found
Extracting -wave scattering lengths from cusp effect in heavy quarkonium dipion transitions
Charge-exchange rescattering leads to a cusp
effect in the invariant mass spectrum of processes with
in the final state which can be used to measure -wave
scattering lengths. Employing a non-relativistic effective field theory, we
discuss the possibility of extracting the scattering lengths in heavy
quarkonium transitions. The transition
is studied in details. We discuss the
precision that can be reached in such an extraction for a certain number of
events.Comment: 15 pages, 7 figures, 1 tabl
Testing and comparing two self-care-related instruments among older Chinese adults
OBJECTIVES:The study aimed to test and compare the reliability and validity, including sensitivity and specificity of the two self-care-related instruments, the Self-care Ability Scale for the Elderly (SASE), and the Appraisal of Self-care Agency Scale-Revised (ASAS-R), among older adults in the Chinese context. METHODS:A cross-sectional design was used to conduct this study. The sample consisted of 1152 older adults. Data were collected by a questionnaire including the Chinese version of SASE (SASE-CHI), the Chinese version of ASAS-R (ASAS-R-CHI) and the Exercise of Self-Care Agency scale (ESCA). Homogeneity and stability, content, construct and concurrent validity, and sensitivity and specificity were assessed. RESULTS:The Cronbach's alpha (α) of SASE-CHI was 0.89, the item-to-total correlations ranged from r = 0.15 to r = 0.81, and the test-retest correlation coefficient (intra-class correlation coefficient, ICC) was 0.99 (95% CI, 0.99-1.00; P<0.001). The Cronbach's α of ASAS-R-CHI was 0.78, the item-to-total correlations ranged from r = 0.20 to r = 0.65, and the test-retest ICC was 0.95 (95% CI, 0.92-0.96; P<0.001). The content validity index (CVI) of SASE-CHI and ASAS-R-CHI was 0.96 and 0.97, respectively. The findings of exploratory and confirmatory factor analyses (EFA and CFA) confirmed a good construct validity of SASE-CHI and ASAS-R-CHI. The Pearson's rank correlation coefficients, as a measure of concurrent validity, between total score of SASE-CHI and ESCA and ASAS-R-CHI and ESCA were assessed to 0.65 (P<0.001) and 0.62 (P<0.001), respectively. Regarding ESCA as the criterion, the area under the receiver operator characteristic (ROC) curve for the cut-point of SASE-CHI and ASAS-R-CHI were 0.93 (95% CI, 0.91-0.94) and 0.83 (95% CI, 0.80-0.86), respectively. CONCLUSION:There is no significant difference between the two instruments. Each has its own characteristics, but SASE-CHI is more suitable for older adults. The key point is that the users can choose the most appropriate scale according to the specific situation
Tetraquarks, hadronic molecules, meson-meson scattering and disconnected contributions in lattice QCD
There are generally two types of Wick contractions in lattice QCD
calculations of a correlation function --- connected and disconnected ones. The
disconnected contribution is difficult to calculate and noisy, thus it is often
neglected. In the context of studying tetraquarks, hadronic molecules and
meson-meson scattering, we show that whenever there are both connected and
singly disconnected contractions, the singly disconnected part gives the
leading order contribution, and thus should never be neglected. As an explicit
example, we show that information about the scalar mesons sigma, f0(980),
a0(980) and kappa will be lost when neglecting the disconnected contributions.Comment: 9 pages, 2 figure
I know you are beautiful even without looking at you: discrimination of facial beauty in peripheral vision
Prior research suggests that facial attractiveness may capture attention at parafovea. However, little is known about how well facial beauty can be detected at parafoveal and peripheral vision. Participants in this study judged relative attractiveness of a face pair presented simultaneously at several eccentricities from the central fixation. The results show that beauty is not only detectable at parafovea but also at periphery. The discrimination performance at parafovea was indistinguishable from the performance around the fovea. Moreover, performance was well above chance even at the periphery. The results show that the visual system is able to use the low spatial frequency information to appraise attractiveness. These findings not only provide an explanation for why a beautiful face could capture attention when central vision is already engaged elsewhere, but also reveal the potential means by which a crowd of faces is quickly scanned for attractiveness
Interactions of Charmed Mesons with Light Pseudoscalar Mesons from Lattice QCD and Implications on the Nature of the D_{s0}^*(2317)
We study the scattering of light pseudoscalar mesons (, ) off charmed
mesons (, ) in full lattice QCD. The S-wave scattering lengths are
calculated using L\"uscher's finite volume technique. We use a relativistic
formulation for the charm quark. For the light quark, we use domain-wall
fermions in the valence sector and improved Kogut-Susskind sea quarks. We
calculate the scattering lengths of isospin-3/2 , , ,
isospin-0 and isospin-1 channels on the lattice. For the
chiral extrapolation, we use a chiral unitary approach to next-to-leading
order, which at the same time allows us to give predictions for other channels.
It turns out that our results support the interpretation of the
as a molecule. At the same time, we also update a
prediction for the isospin breaking hadronic decay width
to keV.Comment: 22 pages, 5 figures; a typo in Table II corrected (for the
coefficients of the NLO amplitudes
A non-perturbative study of the interplay between electron-phonon interaction and Coulomb interaction in undoped graphene
In condensed-matter systems, electrons are subjected to two different
interactions under certain conditions. Even if both interactions are weak, it
is difficult to perform perturbative calculations due to the complexity caused
by the interplay of two interactions. When one or two interactions are strong,
ordinary perturbation theory may become invalid. Here we consider undoped
graphene as an example and provide a non-perturbative quantum-field-theoretic
analysis of the interplay of electron-phonon interaction and Coulomb
interaction. We treat these two interactions on an equal footing and derive the
exact Dyson-Schwinger integral equation of the full Dirac-fermion propagator.
This equation depends on several complicated correlation functions and thus is
difficult to handle. Fortunately, we find that these correlation functions obey
a number of exact identities, which allows us to prove that the Dyson-Schwinger
equation of the full fermion propagator is self-closed. After solving this
self-closed equation, we obtain the renormalized velocity of Dirac fermions and
show that its energy (momentum) dependence is dominantly determined by the
electron-phonon (Coulomb) interaction. In particular, the renormalized velocity
exhibits a logarithmic momentum dependence and a non-monotonic energy
dependence.Comment: 32 pages, 5 figure
Si-based anode materials for lithium rechargeable batteries
Silicon is a very promising candidate to replace graphite as the anode in Li-ion batteries because of its very high theoretical capacity, relatively low cost and low toxicity. However, it has not yet made its way into commercial cells. This review highlights recent progress on Si-based anode materials for lithium rechargeable batteries
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