510 research outputs found
Comprehensive characterizing of vortex phases in type-II superconductor YBa2Cu3O7-x by a magnetoelectric technique
The vortex phases in type-II superconductors are very important since they
determine many magnetic and electric properties of the parent compound.
However, a universal tool to characterize the vortex phases is still lacking.
We demonstrate in a type-II superconductors YBa2Cu3O7-x polycrystal sample that
its vortex phases and phase boundaries can be comprehensively studied by a
magnetoelectric technique. In this method, a thin piezoelectric material
0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(PMN-PT) is mechanically bonded with YBa2Cu3O7-x
to form a laminate structure and act as a strain gauge. The phase diagram of
the YBa2Cu3O7-x polycrystalline was explored by this method. Surprisingly, it
can accurately estimate the Hc1, irreversible line, Hc2 and distinguish among
vortex glass, vortex liquid, non-vortex states. Moreover, it can probe the
dynamic response under different frequencies and observe the threshold
phenomena of vortex liquid phase. It can even account for the density of
vortices in the vortex solid phase. Our technique is readily extended to
investigate the vortex phases in other type-II superconductors.Comment: 23 pages, 6 figure
Investigation and protection of fishery resources in the middle of Bohai Sea
In May and October 2017, 12 stations were set up in the Central Bohai Sea for fishery resources investigation. The results show that there are many dominant species in this area, and the inshore fishery resources are higher than those in the open sea because of the abundant nutrients from land, the high density of zooplankton and the food of swimming animals. In order to effectively protect the fishery resources in the Central Bohai Sea, this paper puts forward some suggestions, such as strengthening the protection propaganda, scientific and reasonable fishing, and strengthening the management of marine environment
The Global Response of Cronobacter sakazakii Cells to Amino Acid Deficiency
Cronobacter species can cause necrotizing enterocolitis and meningitis in neonates and infants, their infection is closely relevant to their responses to extreme growth conditions. In this study, the response of Cronobacter species to amino acid deficiency has been investigated. Four Cronobacter species formed smooth colonies when grown on the solid LB medium, but formed mucoid colonies when grown on the amino acid deficient M9 medium. When the mucoid colonies were stained with tannin mordant, exopolysaccharide around the cells could be discerned. The exopolysaccharide was isolated, analyzed, and identified as colanic acid. When genes wcaD and wcaE relevant to colanic acid biosynthesis were deleted in Cronobacter sakazakii BAA-894, no exopolysaccharide could be produced, confirming the exopolysaccharide formed in C. sakazakii grown in M9 is colanic acid. On the other hand, when genes rcsA, rcsB, rcsC, rcsD, or rcsF relevant to Rcs phosphorelay system was deleted in C. sakazakii BAA-894, colanic acid could not be produced, suggesting that the production of colanic acid in C. sakazakii is regulated by Rcs phosphorelay system. Furthermore, C. sakazakii BAA-894 grown in M9 supplemented with amino acids could not produce exopolysaccharide. Transcriptomes of C. sakazakii BAA-894 grown in M9 or LB were analyzed. A total of 3956 genes were differentially expressed in M9, of which 2339 were up-regulated and 1617 were down-regulated. When C. sakazakii BAA-894 was grown in M9, the genes relevant to the biosynthesis of exopolysaccharide were significantly up-regulated; on the other hand, the genes relevant to the flagellum formation and chemotaxis were significantly down-regulated; in addition, most genes relevant to various amino acid biosynthesis were also significantly regulated. The results demonstrate that amino acid deficiency has a global impact on C. sakazakii cells
Second-order Band Topology in Antiferromagnetic (MnBiTe)(BiTe) Films
The existence of fractionally quantized topological corner states serves as a
key indicator for two-dimensional second-order topological insulators (SOTIs),
yet has not been experimentally observed in realistic materials. Here, based on
first-principles calculations and symmetry arguments, we propose a strategy for
achieving SOTI phases with in-gap corner states in
(MnBiTe)(BiTe) films with antiferromagnetic (AFM) order.
Starting from the prototypical AFM MnBiTe bilayer, we show by an
effective lattice model that such SOTI phase originate from the interplay
between intrinsic spin-orbital coupling and interlayer AFM exchange
interactions. Furthermore, we demonstrate that the nontrivial corner states are
linked to rotation topological invariants under three-fold rotation symmetry
, resulting in -symmetric SOTIs with corner charges fractionally
quantized to (mod ). Due to the great recent
achievements in (MnBiTe)(BiTe) systems, our results
providing reliable material candidates for experimentally accessible AFM
higher-order band topology would draw intense attentions.Comment: 6 pages, 4 figure
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