The JP=1+J^P=1^+ udsˉsˉud\bar s\bar s Tetraquark

Using the color-magnetic interaction Hamiltonian with SU(3) flavor symmetry breaking, we perform a schematic study of the masses of the $J^P=1^+$ tetraquarks in the anti-decuplet representation. After diagonalizing the mass matrix, we find the $ud\bar s\bar s$ tetraquark lies around 1347 MeV. It decays into $K^+K^0\pi^0, K^+K^+\pi^-, K^0K^0\pi^+$ via P-wave. The dual suppression from the not-so-big three-body phase space and P-wave decay barrier may render this exotic state rather narrow. Future experimental exclusion of this state will cast doubt on the validity of applying the simple color-magnetic Hamiltonian to the multiquark system

AFLP analysis on genetic diversity and population structure of small yellow croaker Larimichthys polyactis

The population genetic structure and diversity of small yellow croaker Larimichthys polyactis in the Bohai Bay, Yellow Sea and East China Sea were analyzed using amplified fragment length polymorphism(AFLP). Ninety-one individuals were collected from six locations representing three stocks of small yellow croaker. A total of 218 putative loci were detected by 3 primer combinations, 148 of which were polymorphic (67.89%). The proportion of polymorphic loci and Nei’s genetic diversity for six populations ranged from 55.34 - 60.09%, and from 0.1244 - 0.1378. AMOVA analysis and pairwise FST revealedsignificant genetic differentiation among the three groups based on the breeding migration routes and over-wintering grounds, supporting separate stocks in this species. The result shows the migratorybehavior might be an important factor which influences the genetic structure of this species. The UPGMA tree also revealed the significant geographic structure in this species. Pattern of isolation bydistance was observed in this species, indicating that significant genetic differentiation among localities of small yellow croaker might be due to the geographic distance