929 research outputs found
Is a compact hexaquark state?
The most fascinating dibaryon in the non-strange quark sector is ,
which was reported by WASA-at-COSY Collaboration and confirmed by A2@MAMI
Collaboration. The reported mass and width are GeV,
MeV and the quantum numbers . The structure of
is still in controversy. In the present calculation, the powerful
method in few-body system, Gaussian expansion method is employed to explore the
structure of in the framework of constituent quark models without
assuming the presupposed structure. The results show that the radius of
is around 0.7 fm, a very compact object. Because of the compact
structure, the color singlet-singlet component has a large overlap with the
color octet-octet one, two colorless, large overlapped s dominate the
state is possible.Comment: 7 pages, 8 table
Age-period-cohort effects on the development of cognitive impairment among the elderly
The objectives of the study were to investigate the effects of age, calendar period, and birth cohort on the development of cognitive impairment among the elderly, and to identify factors possibly moderating these effects. Harmonized data were drawn from two community-based cohort studies. A total of 3,021 participants, born after 1895, age 65 years or older with normal cognitive capacities were recruited during 1987-2008 and followed for more than 10 years. Cognitive capability was evaluated periodically using the Clinical Dementia Rating (CDR) scale. Incident mild cognitive impairment (MCI) was defined as the CDR value reaching 0.5. Age-period-cohort (APC) modelling approach was used to evaluate three time-varying effects on the development of MCI. Confounding and moderating effects of gender, education, and ApoE4 allele were also examined. Our analysis results showed that age was the most significant time-dependent factor affecting the MCI incident rates. Within the same calendar period and birth cohort, the MCI rate in the older elderly was significantly higher compared with the younger elderly population. A significant period effect was observed in which the MCI incidence rates were decreasing from the period of 1990-1994 through 2015 after controlling for age and birth cohort. No significant cohort effect was found. Gender showed no significant confounding or moderating effects. The age effects on MCI incidence rate was not moderated or confounded by education, while the period effects were significantly confounded by education. The cohort effect was significantly moderated by education. The cohort effects on MCI incidence rates for individuals who received HS education or higher education were different depending on the levels of education. ApoE4 allele did not show a significant moderating effect.
Public Health Significance
The APC model shows advantages over the traditional modelling approaches as it dissects the independent effects of age, period, and cohort. For public health, chronic disease prevalence often reflects a combination of processes that vary by these three factors. Better understanding the impacts of these time-dependent factors on disease rates help to guide hypotheses about etiologic mechanisms, and more importantly, guides researchers in conducting and presenting surveillance with the best practices
The explanation of some exotic states in the tetraquark system
Inspired by the recent observation of , and
by the LHCb Collaboration and some exotic resonances such as
, , etc. by several experiment collaborations, the
tetraquark systems with , and are
systematically investigated in the framework of the quark delocalization color
screening model(QDCSM). Two structures, the meson-meson and diquark-antidiquark
structures, as well as the channel-coupling of all channels of these two
configurations are considered in this work. The numerical results indicate that
the molecular bound state with can be supposed
to explain the . Besides, by using the stabilization method,
several resonant states are obtained. There are four states
around the resonance mass 4035 MeV, 4385 MeV, 4524 MeV, and 4632 MeV,
respectively; one state around the resonance mass 4327 MeV; and
two states around the resonance mass 4419 MeV and 4526 MeV,
respectively. All of them are compact tetraquarks. Among these states,
, and can be explained as the compact tetraquark
state with , and the is possible to be a candidate of
the compact tetraquark state with . More experimental tests are
expected to check the existence of all these possible resonance states.Comment: 10 pages, 3 figure
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