87 research outputs found
Isospin splitting of the Dirac mass probed by the relativistic Brueckner-Hartree-Fock theory in the full Dirac space
The isospin splitting of the Dirac mass obtained with the relativistic
Brueckner-Hartree-Fock (RBHF) theory is thoroughly investigated. From the
perspective in the full Dirac space, the long-standing controversy between the
momentum-independence approximation (MIA) method and the projection method on
the isospin splitting of the Dirac mass in asymmetric nuclear matter (ANM) is
analyzed in detail. We find that, the \textit{assumption procedure} of the MIA
method, which assumes that the single-particle potentials are momentum
independent, is not a sufficient condition that directly leads to the wrong
sign of the isospin splitting of the Dirac mass, while the \textit{extraction
procedure} of the MIA method, which extracts the single-particle potentials
from the single-particle potential energy, leads to the wrong sign. By
approximately solving the set of equations involved in the \textit{extraction
procedure}, a formal expression of the Dirac mass is obtained. The wrong
isospin splitting of the Dirac mass is mainly caused by that the
\textit{extraction procedure} forcely assumes the momentum dependence of the
single-particle potential energy to be a quadratic form where the strength is
solely determined by the constant scalar potential.Comment: 13 pages, 4 figure
Neutron-proton effective mass splitting in neutron-rich matter
Nucleon effective masses in neutron-rich matter are studied with the
relativistic Brueckner-Hartree-Fock (RBHF) theory in the full Dirac space. The
neutron and proton effective masses for symmetric nuclear matter are 0.80,
which agrees well with the empirical values. In neutron-rich matter, the
effective mass of the neutron is found larger than that of the proton, and the
neutron-proton effective mass splittings at the empirical saturation density
are predicted as with being the isospin asymmetry
parameter. The result is compared to other ab initio calculations and is
consistent with the constraints from the nuclear reaction and structure
measurements, such as the nucleon-nucleus scattering, the giant resonances of
Pb, and the Hugenholtz-Van Hove theorem with systematics of nuclear
symmetry energy and its slope. The predictions of the neutron-proton effective
mass splitting from the RBHF theory in the full Dirac space might be helpful to
constrain the isovector parameters in phenomenological density functionals.Comment: 14 pages, 4 figure
RSG: Fast Learning Adaptive Skills for Quadruped Robots by Skill Graph
Developing robotic intelligent systems that can adapt quickly to unseen wild
situations is one of the critical challenges in pursuing autonomous robotics.
Although some impressive progress has been made in walking stability and skill
learning in the field of legged robots, their ability to fast adaptation is
still inferior to that of animals in nature. Animals are born with massive
skills needed to survive, and can quickly acquire new ones, by composing
fundamental skills with limited experience. Inspired by this, we propose a
novel framework, named Robot Skill Graph (RSG) for organizing massive
fundamental skills of robots and dexterously reusing them for fast adaptation.
Bearing a structure similar to the Knowledge Graph (KG), RSG is composed of
massive dynamic behavioral skills instead of static knowledge in KG and enables
discovering implicit relations that exist in be-tween of learning context and
acquired skills of robots, serving as a starting point for understanding subtle
patterns existing in robots' skill learning. Extensive experimental results
demonstrate that RSG can provide rational skill inference upon new tasks and
environments and enable quadruped robots to adapt to new scenarios and learn
new skills rapidly
What influenced the lesion patterns and hemodynamic characteristics in patients with internal carotid artery stenosis? A retrospective study
•Blood perfusion influences ischemic lesions in patients with of ICAS.•Communicating arteries influence intracranial blood flow.•TCD was a convenient and rapid tool to assess cerebral blood flow
Mutation Status and Immunohistochemical Correlation of KRAS, NRAS, and BRAF in 260 Chinese Colorectal and Gastric Cancers
KRAS, NRAS and BRAF are kinases involved in the RAS-RAF-MAPK signaling pathway and also potential tumor-driven genes. Patients with KRAS/NRAS/BRAF mutations are resistant to anti-EGFR monoclonal antibody therapy. The main purpose of this study is to investigate the mutation status and distribution of KRAS/NRAS/BRAF in Chinese colorectal and gastric cancers, and to explore the histopathological changes and related immunohistochemical marker changes caused by these mutations. The mutation status of KRAS (exons 2, codon 12/13), NRAS (exons 2/3/4, codon 12/13/59/61/117/146) and BRAF (exons 15, codon 600) were detected by amplification refractory mutation system polymerase chain reaction (ARMS-PCR) in 86 colon cancer, 140 rectal cancer and 34 gastric cancer tissues. Then, the frequencies and distribution of KRAS/NRAS/BRAF mutations were described in detail. Furthermore, the relationship between KRAS/NRAS/BRAF mutations and the features of histopathological and related immunohistochemical markers were analyzed. The results showed that KRAS/NRAS/BRAF mutation rates in colon cancer were 44.2, 1.2, and 3.5%; in rectal cancer were 37.1, 4.3, and 0.7%; in gastric cancer were none, none and 2.9%. The mutation rate of KRAS in female (48.8%) is significantly higher than that of male (27.8%), and the mutation rate increased with the higher degree of differentiation. Additionally, the mutation rate of BRAF detected by ARMS-PCR (1.77%) was significantly lower than that by immunohistochemistry (4.11%). It also showed that the KRAS/NRAS/BRAF mutation status had a certain relationship with the expression of some immunohistochemical markers. This study provides more data support for clinical research on KRAS/NRAS/BRAF mutation in CRCs or gastric cancers
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