6,609 research outputs found
Design and Testing of Cesium Atomic Concentration Detection System Based on TDLAS
In order to better build the Neutral Beam Injector with Negative Ion Source
(NNBI), the pre-research on key technologies has been carried out for the
Comprehensive Research Facility for Fusion Technology (CRAFT). Cesium seeding
into negative-ion sources is a prerequisite to obtain the required negative
hydrogen ion. The performance of ion source largely depends on the cesium
conditions in the source. It is very necessary to quantitatively measure the
amount of cesium in the source during the plasma on and off periods (vacuum
stage). This article uses the absorption peak of cesium atoms near 852.1nm to
build a cesium atom concentration detection system based on Tunable Diode Laser
Absorption Spectroscopy (TDLAS) technology. The test experiment based on the
cesium cell is carried out, obtained the variation curve of cesium
concentration at different temperatures. The experimental results indicate
that: the system detection range is within 5*10E6-2.5*10E7 pieces/cm3 and the
system resolution better than 1*10E6 pieces/cm3.Comment: 8 pages,7 figures, the 20th International Symposium on Laser-Aided
Plasma Diagnostic
Nonlinear voltage dependence of the shot noise in mesoscopic degenerate conductors with strong electron-electron scattering
It is shown that measurements of zero-frequency shot-noise can provide
information on electron-electron interaction, because the strong interaction
results in the nonlinear voltage dependence of the shot noise in metallic
wires. This is due to the fact that the Wiedemann-Franz law is no longer valid
in the case of considerable electron-electron interaction. The deviations from
this law increase the noise power and make it dependent strongly on the ratio
of electron-electron and electron-impurity scattering rates.Comment: 4 pages, 2 figures, revised version according to referee's comment
First direct observation of the Van Hove singularity in the tunneling spectra of cuprates
In two-dimensional lattices the electronic levels are unevenly spaced, and
the density of states (DOS) displays a logarithmic divergence known as the Van
Hove singularity (VHS). This is the case in particular for the layered cuprate
superconductors. The scanning tunneling microscope (STM) probes the DOS, and is
therefore the ideal tool to observe the VHS. No STM study of cuprate
superconductors has reported such an observation so far giving rise to a debate
about the possibility of observing directly the normal state DOS in the
tunneling spectra. In this study, we show for the first time that the VHS is
unambiguously observed in STM measurements performed on the cuprate Bi-2201.
Beside closing the debate, our analysis proves the presence of the pseudogap in
the overdoped side of the phase diagram of Bi-2201 and discredits the scenario
of the pseudogap phase crossing the superconducting dome.Comment: 4 pages, 4 figure
Auto Segmentation of Lung in Non-small Cell Lung Cancer Using Deep Convolution Neural Network
Segmentation of Lung is the vital first step in radiologic diagnosis of lung cancer. In this work, we present a deep learning based automated technique that overcomes various shortcomings of traditional lung segmentation and explores the role of adding âexplainabilityâ to deep learning models so that the trust can be built on these models. Our approach shows better generalization across different scanner settings, vendors and the slice thickness. In addition, there is no initialization of the seed point making it complete automated without manual intervention. The dice score of 0.98 is achieved for lung segmentation on an independent data set of non-small cell lung cancer
Structural insights into RNA processing by the human RISC-loading complex.
Targeted gene silencing by RNA interference (RNAi) requires loading of a short guide RNA (small interfering RNA (siRNA) or microRNA (miRNA)) onto an Argonaute protein to form the functional center of an RNA-induced silencing complex (RISC). In humans, Argonaute2 (AGO2) assembles with the guide RNA-generating enzyme Dicer and the RNA-binding protein TRBP to form a RISC-loading complex (RLC), which is necessary for efficient transfer of nascent siRNAs and miRNAs from Dicer to AGO2. Here, using single-particle EM analysis, we show that human Dicer has an L-shaped structure. The RLC Dicer's N-terminal DExH/D domain, located in a short 'base branch', interacts with TRBP, whereas its C-terminal catalytic domains in the main body are proximal to AGO2. A model generated by docking the available atomic structures of Dicer and Argonaute homologs into the RLC reconstruction suggests a mechanism for siRNA transfer from Dicer to AGO2
Atomic-scale images of charge ordering in a mixed-valence manganite
Transition-metal perovskite oxides exhibit a wide range of extraordinary but
imperfectly understood phenomena. Charge, spin, orbital, and lattice degrees of
freedom all undergo order-disorder transitions in regimes not far from where
the best-known of these phenomena, namely high-temperature superconductivity of
the copper oxides, and the 'colossal' magnetoresistance of the manganese
oxides, occur. Mostly diffraction techniques, sensitive either to the spin or
the ionic core, have been used to measure the order. Unfortunately, because
they are only weakly sensitive to valence electrons and yield superposition of
signals from distinct mesoscopic phases, they cannot directly image mesoscopic
phase coexistence and charge ordering, two key features of the manganites. Here
we describe the first experiment to image charge ordering and phase separation
in real space with atomic-scale resolution in a transition metal oxide. Our
scanning tunneling microscopy (STM) data show that charge order is correlated
with structural order, as well as with whether the material is locally metallic
or insulating, thus giving an atomic-scale basis for descriptions of the
manganites as mixtures of electronically and structurally distinct phases.Comment: 8 pages, 4 figures, 19 reference
Architecture of Pol II(G) and molecular mechanism of transcription regulation by Gdown1.
Tight binding of Gdown1 represses RNA polymerase II (Pol II) function in a manner that is reversed by Mediator, but the structural basis of these processes is unclear. Although Gdown1 is intrinsically disordered, its Pol II interacting domains were localized and shown to occlude transcription factor IIF (TFIIF) and transcription factor IIB (TFIIB) binding by perfect positioning on their Pol II interaction sites. Robust binding of Gdown1 to Pol II is established by cooperative interactions of a strong Pol II binding region and two weaker binding modulatory regions, thus providing a mechanism both for tight Pol II binding and transcription inhibition and for its reversal. In support of a physiological function for Gdown1 in transcription repression, Gdown1 co-localizes with Pol II in transcriptionally silent nuclei of early Drosophila embryos but re-localizes to the cytoplasm during zygotic genome activation. Our study reveals a self-inactivation through Gdown1 binding as a unique mode of repression in Pol II function
The cyclin-dependent kinase inhibitor p57(Kip2) is epigenetically regulated in carboplatin resistance and results in collateral sensitivity to the CDK inhibitor seliciclib in ovarian cancer
Carboplatin remains a first-line agent in the management of epithelial ovarian cancer (EOC). Unfortunately, platinum-resistant disease ultimately occurs in most patients. Using a novel EOC cell line with acquired resistance to carboplatin: PEO1CarbR, genome-wide micro-array profiling identified the cyclin-dependent kinase inhibitor p57(Kip2) as specifically downregulated in carboplatin resistance. Presently, we describe confirmation of these preliminary data with a variety of approaches
A novel oxygen carrier 'YQ23' suppresses the liver tumor metastasis by decreasing circulating endothelial progenitor cells and regulatory T cells
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