3,730 research outputs found
Direct photoluminescence probing of ferromagnetism in monolayer two-dimensional CrBr3
Atomically thin magnets are the key element to build up spintronics based on
two-dimensional materials. The surface nature of two-dimensional ferromagnet
opens up opportunities to improve the device performance efficiently. Here, we
report the intrinsic ferromagnetism in atomically thin monolayer CrBr3,
directly probed by polarization resolved magneto-photoluminescence. The
spontaneous magnetization persists in monolayer CrBr3 with a Curie temperature
of 34 K. The development of magnons by the thermal excitation is in line with
the spin-wave theory. We attribute the layer-number dependent hysteresis loops
in thick layers to the magnetic domain structures. As a stable monolayer
material in air, CrBr3 provides a convenient platform for fundamental physics
and pushes the potential applications of the two-dimensional ferromagnetism.Comment: 27 pages, 10 figure
Analysis of Down syndrome failed to be diagnosed after prenatal screening: A multicenter study.
To analyze the characters of Down syndrome (DS) who failed to be diagnosed after prenatal screening and hope to be able to improve the programs of prenatal screening and reduce the missed diagnosis of DS. In this multicenter study, we collected the missed cases from 3 prenatal diagnosis centers and analyzed their characters. A total of 126 DS babies failed to be diagnosed after prenatal screening. Their mothers accepted the prenatal screening in second trimester. We collected the mothers' blood and detected the levels of alpha-fetoprotein (AFP) and the free beta subunit of human chorionic gonadotropin (fβhCG) by time-resolved fluoroimmunoassay. The values were also presented as multiples of the median (MoM) and determined the risk of carrying a fetus with DS by Wallace LifeCycle Elipse analysis software. Compared with normal control group, the level of fβhCG and hCG MoM were dramatically increased, while AFP and AFP MoM were decreased. The area under the receiver-operating-characteristic curve of trisomy 21 was 0.8387 for hCG-MoM and AFP-MoM testing. The sensitivity, specificity, positive predictive value, and negative predictive value were 84.6%, 74.8%, 75.4%, and 83.6%, respectively. Meanwhile, the prediction mode was "0.39957 + 1.90897HCG-MOM -3.32713AFP-MOM". It was worthwhile noting that the risk of 65.9% DS missed diagnosis group were higher than 1/1000, 92.9% higher than 1/3000. However, 72.5% cases in normal control group were lower than 1/3000. Only 9.2% mothers would be higher than the value of risk in 1/1000. The prediction mode of hCG MoM and AFP MoM might be able to help us reduce the missed diagnosis. It is also necessary to adjust more reasonable range of noninvasive prenatal testing with further clinical researches
Generalized Volume-Complexity for RN-AdS Black Hole
The connection between quantum information and quantum gravity has captured
the imagination of physicists. Recently, a broad new class of gravitational
observables have been proposed to provide new possibilities for holographic
complexity [Phys. Rev. Lett. 128 (2022) 081602], which is an extension of
volume in the Complexity=Volume proposal. In this paper, we investigate
generalized volume-complexity for the 4-dimensional Reissner-Nordstr\"{o}m-AdS
black hole. These new observables satisfy the characteristic of the thermofield
double state, i.e., they grow linearly in time on the late stage. We find that
there are multiple extremal hypersurfaces anchored at a certain boundary time.
In other words, for the same boundary time, more than one observable
(generalized volume) can exist in the bulk. The size relationship of the
observables on the two hypersurfaces changes over time. This will result in the
substitution of the maximum extreme hypersurface which is dual to the
complexity of the thermofield double state. We call the time when one
hypersurface replaces another to become the largest extreme hypersurface the
turning time . That is, a hypersurface dual to the complexity
of the thermofield double state defined on the boundary jumps from one branch
to another. This discontinuous jump is highly reminiscent of a phase
transition, and the turning time denotes the moment at which this phase
transition occurs. Our findings propose a discontinuous variation in bulk
physics that is dual to the complexity of the thermofield double state defined
on the boundary.Comment: 20 pages, 9 figure
Holographic Complexity with Different Gravitational Observables
We investigate a more general conjugate regarding the holographic complexity:
complexity equals any gravitational observables [Phys. Rev. Lett. 128, 081602
(2022)], which is an extension of the complexity equals volume proposal. These
gravitational observables are referred to as generalized volumes.In this paper,
we investigate the generalized volume-complexity for the planar anti-de Sitter
black hole and the charged Banados-Teitelboim-Zanelli black hole with different
gravitational observables. We note that when anchored at the same boundary
time, there may be more than one extremal hypersurface. Determining which one
can represent the complexity has become a question that requires further
discussion. For the complexity equals volume proposal, the complexity is
thought to be proportional to a maximal volume of a hypersurface anchored on
the boundary time slice. However, in our research, we find that the size
relationship of the gravitational observables on these extremal generalized
volume slices are not fixed, but change over time. We refer to this moment of
the change as the turning time.Comment: 18 pages, 11 figure
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