Engineering topics
Chen, C.
Publications and source records attributed to Chen, C..
Observation of Ultra-high-energy Cosmic Rays with the ANITA Balloon-borne Radio Interferometer
Abstract Not Provided
Ultra-Relativistic Magnetic Monopole Search with the ANITA-II Balloon-Borne Radio Interferometer
Abstract Not Provided
Electroproduction of K+ Λ at JLab Hall-C
A Λ hypernuclear spectroscopic experiment, JLab E05-115 was performed at JLab Hall-C in 2009 by the (e, e' K + ) reaction. Data of Λ hypernuclei with mass numbers from A = 7 to A = 52 were successfully taken, and the analyses are in progress. A polyethylene (CH 2 ) target was used as a proton target to calibrate energy scales, and to study elementary process of the p(e, e' K + )Λ, Σ 0 reaction. We report a preliminary differential cross section of K + Λ electro-production at low Q 2 [~0.01 (GeV/c) 2 ] and at small kaon angles (cosΘ$CM\atop{K}$ ~0.97) in the present article.
Observation of the Λ ⁷He Hypernucleus by the (e, e'K⁺) Reaction
An experiment with a newly developed high-resolution kaon spectrometer and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab. The ground state of a neutron-rich hypernucleus, He Λ ⁷, was observed for the first time with the (e, e'K⁺) reaction with an energy resolution of ~0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The He Λ ⁷ binding energy supplies the last missing information of the A=7, T=1 hypernuclear isotriplet, providing a new input for the charge symmetry breaking effect of the ΛN potential.
Simulation of adiabatic thermal beams in a periodic solenoidal magnetic focusing field
Not Available
New Measurements of the Transverse Beam Asymmetry for Elastic Electron Scattering from Selected Nuclei
Not Available
Molecular mechanism of pancreatic tumor metastasis inhibition by Gd@C 82 (OH) 22 and its implication for de novo design of nanomedicine
Pancreatic adenocarcinoma is the most lethal of the solid tumors and the fourth-leading cause of cancer-related death in North America. Matrix metalloproteinases (MMPs) have long been targeted as a potential anticancer therapy because of their seminal role in angiogenesis and extracellular matrix (ECM) degradation of tumor survival and invasion. However, the inhibition specificity to MMPs and the molecular-level understanding of the inhibition mechanism remain largely unresolved. Here, we found that endohedral metallofullerenol Gd@C 82 (OH) 22 can successfully inhibit the neoplastic activity with experiments at animal, tissue, and cellular levels. Gd@C 82 (OH) 22 effectively blocks tumor growth in human pancreatic cancer xenografts in a nude mouse model. Enzyme activity assays also show Gd@C 82 (OH) 22 not only suppresses the expression of MMPs but also significantly reduces their activities. We then applied large-scale molecular-dynamics simulations to illustrate the molecular mechanism by studying the Gd@C 82 (OH) 22 –MMP-9 interactions in atomic detail. Our data demonstrated that Gd@C 82 (OH) 22 inhibits MMP-9 mainly via an exocite interaction, whereas the well-known zinc catalytic site only plays a minimal role. Steered by nonspecific electrostatic, hydrophobic, and specific hydrogen-bonding interactions, Gd@C 82 (OH) 22 exhibits specific binding modes near the ligand-specificity loop S1', thereby inhibiting MMP-9 activity. Both the suppression of MMP expression and specific binding mode make Gd@C 82 (OH) 22 a potentially more effective nanomedicine for pancreatic cancer than traditional medicines, which usually target the proteolytic sites directly but fail in selective inhibition. Finally, our findings provide insights for de novo design of nanomedicines for fatal diseases such as pancreatic cancer.
DRD4 Genotype Predicts Longevity in Mouse and Human
N/A
Subchannel analysis on CGNPC SCWR
SCWR, as one of the candidates of six generation 4 reactors, is the water cooled reactor operating above the critical point. The investigation on SCWR was popular worldwide and amount of concepts were proposed by different country. Chinese Guangdong Nuclear Power Company (CGNPC) also designed a SCWR based on the Double-row Assembly. Based on the power distribution in different stage of the fuel cycle obtained by neutronics physics, the first pass and the second pass were calculated using ATHAS code, respectively, and the maximum cladding temperatures were obtained, which was satisfied the design limitation. The sensitivity of the geometry parameters was analyzed, and the optimum on the assembly design was carried. (authors)
An analysis of the sliding pressure start-up of SCWR
In this paper, the preliminary sliding pressure start-up system and scheme of supercritical water-cooled reactor in CGNPC (CGN-SCWR) were proposed. Thermal-hydraulic behavior in start-up procedures was analyzed in detail by employing advanced reactor subchannel analysis software ATHAS. The maximum cladding temperature (MCT for short) and core power of fuel assembly during the whole start-up process were investigated comparatively. The results show that the recommended start-up scheme meets the design requirements from the perspective of thermal-hydraulic. (authors)
Beam-Target Double-Spin Asymmetry A LT in Charged Pion Production from Deep Inelastic Scattering on a Transversely Polarized He 3 Target at 1.4 < Q 2 < 2.7 GeV 2
We report the first measurement of the double-spin asymmetry A LT for charged pion electroproduction in semi-inclusive deep inelastic electron scattering on a transversely polarized 3 He target. The kinematics focused on the valence quark region, 0.16 < x < 0.35 with 1.4 < Q 2 < 2.7 GeV 2 . The corresponding neutron A LT asymmetries were extracted from the measured 3 He asymmetries and proton/ 3 He cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g 1T q and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for π - production on 3 He and the neutron, while our π + asymmetries are consistent with zero.
Observation and Spectral Measurements of the Crab Nebula with Milagro
The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV - 100 TeV gamma ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ~1 and ~100 TeV. The TeV emission is believed to be caused by inverse-Compton up-scattering scattering of ambient photons by an energetic electron population. The location of a Te V steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fit.
First look at the Fomalhaut debris disk with the Spitzer Space Telescope
We present Spitzer Space Telescope early release observations of Fomalhaut, a nearby A-type star with dusty circumstellar debris. The disk is spatially resolved at 24, 70, and 160 mu m using the Multiband Imaging Photometer for Spitzer (MIPS). While the disk orientation and outer radius are comparable to values measured in the submillimeter, the disk inner radius cannot be precisely defined: the central hole in the submillimeter ring is at least partially filled with emission from warm dust, seen in Spitzer Infrared Spectrograph (IRS)17.5-34 mu m spectra and MIPS 24 mu m images. The disk surface brightness becomes increasingly asymmetric toward shorter wavelengths, with the south-southeast ansa always brighter than the north-northwest one. This asymmetry may reflect perturbations on the disk by an unseen interior planet.
Oscillatory Hierarchy Controlling Cortical Excitability and Stimulus Integration
Cortical gamma band oscillations have been recorded in sensory cortices of cats and monkeys, and are thought to aid in perceptual binding. Gamma activity has also been recorded in the rat hippocampus and entorhinal cortex, where it has been shown, that field gamma power is modulated at theta frequency. Since the power of gamma activity in the sensory cortices is not constant (gamma-bursts). we decided to examine the relationship between gamma power and the phase of low frequency oscillation in the auditory cortex of the awake macaque. Macaque monkeys were surgically prepared for chronic awake electrophysiological recording. During the time of the experiments. linear array multielectrodes were inserted in area AI to obtain laminar current source density (CSD) and multiunit activity profiles. Instantaneous theta and gamma power and phase was extracted by applying the Morlet wavelet transformation to the CSD. Gamma power was averaged for every 1 degree of low frequency oscillations to calculate power-phase relation. Both gamma and theta-delta power are largest in the supragranular layers. Power modulation of gamma activity is phase locked to spontaneous, as well as stimulus-related local theta and delta field oscillations. Our analysis also revealed that the power of theta oscillations is always largest at a certain phase of delta oscillation. Auditory stimuli produce evoked responses in the theta band (Le., there is pre- to post-stimulus addition of theta power), but there is also indication that stimuli may cause partial phase re-setting of spontaneous delta (and thus also theta and gamma) oscillations. We also show that spontaneous oscillations might play a role in the processing of incoming sensory signals by 'preparing' the cortex.