9,543 research outputs found
Electrical and optical properties of fluid iron from compressed to expanded regime
Using quantum molecular dynamics simulations, we show that the electrical and
optical properties of fluid iron change drastically from compressed to expanded
regime. The simulation results reproduce the main trends of the electrical
resistivity along isochores and are found to be in good agreement with
experimental data. The transition of expanded fluid iron into a nonmetallic
state takes place close to the density at which the constant volume derivative
of the electrical resistivity on internal energy becomes negative. The study of
the optical conductivity, absorption coefficient, and Rosseland mean opacity
shows that, quantum molecular dynamics combined with the Kubo-Greenwood
formulation provides a powerful tool to calculate and benchmark the electrical
and optical properties of iron from expanded fluid to warm dense region
"Hard-scattering" approach to very hindered magnetic-dipole transitions in quarkonium
For a class of hindered magnetic dipole () transition processes, such as
(the discovery channel of the meson),
the emitted photon is rather energetic so that the traditional approaches based
on multipole expansion may be invalidated. We propose that a "hard-scattering"
picture, somewhat analogous to the pion electromagnetic form factor at large
momentum transfer, may be more plausible to describe such types of transition
processes. We work out a simple factorization formula at lowest order in the
strong coupling constant, which involves convolution of the Schr\"odinger wave
functions of quarkonia with a perturbatively calculable part induced by
exchange of one semihard gluon between quark and antiquark. This formula,
without any freely adjustable parameters, is found to agree with the measured
rate of rather well, and can also reasonably
account for other recently measured hindered transition rates. The
branching fractions of are also
predicted.Comment: v3; 5 pages, 1 figure and 1 table; title changed, presentation
improve
SMA observations of C2H in High-Mass Star Forming Regions
CH is a representative hydrocarbon that is abundant and ubiquitous in the
interstellar medium (ISM). To study its chemical properties, we present
Submillimeter Array (SMA) observations of the CH and HCN
transitions and the 1.1 mm continuum emission toward four OB
cluster-forming regions, AFGL 490, ON 1, W33 Main, and G10.6-0.4, which cover a
bolometric luminosity range of 10--10 . We found that
on large scales, the CH emission traces the dense molecular envelope.
However, for all observed sources, the peaks of CH emission are offset by
several times times 10 AU from the peaks of 1.1 mm continuum emission,
where the most luminous stars are located. By comparing the distribution and
profiles of CH hyperfine lines and the 1.1 mm continuum emission, we find
that the CH column density (and abundance) around the 1.1 mm continuum
peaks is lower than those in the ambient gas envelope. Chemical models suggest
that CH might be transformed to other species owing to increased
temperature and density; thus, its reduced abundance could be the signpost of
the heated molecular gas in the 10 AU vicinity around the embedded
high-mass stars. Our results support such theoretical prediction for centrally
embedded -- OB star-forming cores, while future
higher-resolution observations are required to examine the CH
transformation around the localized sites of high-mass star formation.Comment: 10 pages, 6 figures. ApJ accepted. Comments welcom
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
Generation of Oligodendrocyte Progenitor Cells From Mouse Bone Marrow Cells.
Oligodendrocyte progenitor cells (OPCs) are a subtype of glial cells responsible for myelin regeneration. Oligodendrocytes (OLGs) originate from OPCs and are the myelinating cells in the central nervous system (CNS). OLGs play an important role in the context of lesions in which myelin loss occurs. Even though many protocols for isolating OPCs have been published, their cellular yield remains a limit for clinical application. The protocol proposed here is novel and has practical value; in fact, OPCs can be generated from a source of autologous cells without gene manipulation. Our method represents a rapid, and high-efficiency differentiation protocol for generating mouse OLGs from bone marrow-derived cells using growth-factor defined media. With this protocol, it is possible to obtain mature OLGs in 7-8 weeks. Within 2-3 weeks from bone marrow (BM) isolation, after neurospheres formed, the cells differentiate into Nestin+ Sox2+ neural stem cells (NSCs), around 30 days. OPCs specific markers start to be expressed around day 38, followed by RIP+O4+ around day 42. CNPase+ mature OLGs are finally obtained around 7-8 weeks. Further, bone marrow-derived OPCs exhibited therapeutic effect in shiverer (Shi) mice, promoting myelin regeneration and reducing the tremor. Here, we propose a method by which OLGs can be generated starting from BM cells and have similar abilities to subventricular zone (SVZ)-derived cells. This protocol significantly decreases the timing and costs of the OLGs differentiation within 2 months of culture
An Extended Single-Valued Neutrosophic Projection-Based Qualitative Flexible Multi-Criteria Decision-Making Method
With respect to multi-criteria decision-making (MCDM) problems in which the criteria denote the form of single-valued neutrosophic sets (SVNSs), and the weight information is also fully unknown, a novel MCDM method based on qualitative flexible multiple criteria (QUALIFLEX) is developed. Firstly, the improved cosine measure of the included angle between two SVNSs is defined
A SiO J = 5 - 4 Survey Toward Massive Star Formation Regions
We performed a survey in the SiO line toward a sample of
199 Galactic massive star-forming regions at different evolutionary stages with
the SMT 10 m and CSO 10.4 m telescopes. The sample consists of 44 infrared dark
clouds (IRDCs), 86 protostellar candidates, and 69 young \HII\ regions. We
detected SiO line emission in 102 sources, with a detection
rate of 57\%, 37\%, and 65\% for IRDCs, protostellar candidates, and young
\HII\ regions, respectively. We find both broad line with Full Widths at Zero
Power (FWZP) 20 \kms and narrow line emissons of SiO in objects at various
evolutionary stages, likely associated with high-velocity shocks and
low-velocity shocks, respectively. The SiO luminosities do not show apparent
differences among various evolutionary stages in our sample. We find no
correlation between the SiO abundance and the luminosity-to-mass ratio,
indicating that the SiO abundance does not vary significantly in regions at
different evolutionary stages of star formation.Comment: 25 pages, 9 figures, 5 tables, accepted for publication in Ap
Editorial: Intelligent Recognition and Detection in Neuroimaging
This topic reports the recent intelligent recognition and detection
methods/applications via voice data, EEG, retina images, MRI, PET, and OCT. With the help of intelligent recognition and
detection methods, those models can help realize analysis,
enhancement, reconstruction, segmentation, and classification.
Some of these models yield better performances than state-ofthe-
art. Remarkably, some models are explainable, giving visual
heat maps of the location of regions of interest.
We expect this Research Topic will provide a comprehensive
picture of recent intelligent recognition and detection methods
using artificial intelligence and deep learning. This Research
Topic will serve as a starting point for designing more complex
intelligent recognition and detection methods, which may be
applied in medical image analysis fields
Experimental preparation and verification of quantum money
A quantum money scheme enables a trusted bank to provide untrusted users with
verifiable quantum banknotes that cannot be forged. In this work, we report an
experimental demonstration of the preparation and verification of unforgeable
quantum banknotes. We employ a security analysis that takes experimental
imperfections fully into account. We measure a total of states
in one verification round, limiting the forging probability to based
on the security analysis. Our results demonstrate the feasibility of preparing
and verifying quantum banknotes using currently available experimental
techniques.Comment: 12 pages, 4 figure
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