XANES investigation of the local structure of Co nanoclusters embedded in Ag

Ion-implanted cobalt atoms into a silver matrix with a layer thickness of about 20 nm were studied by x-ray absorption near-edge spectroscopy (XANES) at the Co $K$ edge. Full multiple scattering ab initio calculations of Co XANES at the $K$ edge provide a phase fingerprint to distinguish the Co structure of samples prepared at different doses and annealing temperatures. The bcc Co phase is formed for the as-prepared sample with 6 at. % and the fcc Co phase is formed at the expense of the bcc phase for the sample with 12 at. % after annealing at $400\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.

XANES investigation of the local structure of Co nanoclusters embedded in Ag. Phys

Ion-implanted cobalt atoms into a silver matrix with a layer thickness of about 20 nm were studied by x-ray absorption near-edge spectroscopy ͑XANES͒ at the Co K edge. Full multiple scattering ab initio calculations of Co XANES at the K edge provide a phase fingerprint to distinguish the Co structure of samples prepared at different doses and annealing temperatures. The bcc Co phase is formed for the as-prepared sample with 6 at. % and the fcc Co phase is formed at the expense of the bcc phase for the sample with 12 at. % after annealing at 400°C

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Probing calcium and sulfur distribution and pattern in hairs using micro-proton induced X-ray emission (MPIXE)

More than 20 hair strands obtained from several people are analyzed by non-invasive micro-proton induced X-ray emission (PIXE) for probing calcium and sulfur distribution and pattern. The sulfur content in woman's hair along the longitudinal axis shows a monthly rhythm whereas the level of Ca is much higher in the medulla core and exhibits a daily rhythm both in male and female hair. The Ca content gradually decreases from the tip to the root position in the shedding process and more Ca can be found in black hair compared to white hair.NRC publication: Ye

A source study of atmospheric polycyclic aromatic hydrocarbons in Shenzhen, South China

Air pollution has become a serious problem in the Pearl River Delta, South China, particularly in winter due to the local micrometeorology. In this study, atmospheric polycyclic aromatic hydrocarbons (PAHs) were monitored weekly in Shenzhen during the winter of 2006. Results indicated that the detected PAHs were mainly of vapor phase compounds with phenanthrene dominant. The average vapor phase and particle phase PAHs concentration in Shenzhen was 101.3 and 26.7 ng m 123, respectively. Meteorological conditions showed great effect on PAH concentrations. The higher PAHs concentrations observed during haze episode might result from the accumulation of pollutants under decreased boundary layer, slower wind speed, and long-term dryness conditions. The sources of PAHs in the air were estimated by principal component analysis in combination with diagnostic ratios. Vehicle exhaust was the major PAHs source in Shenzhen, accounting for 50.0% of the total PAHs emissions, whereas coal combustion and solid waste incineration contributed to 29.4% and 20.6% of the total PAHs concentration, respectively. The results clearly indicated that the increasing solid waste incinerators have become a new important PAHs source in this region.Peer reviewed: YesNRC publication: Ye

Enhancement of Ne-like Ar 46.9 nm laser intensity by increasing the inner diameter of the capillary

With the ceramic capillaries of 3.2, 4.0 and 4.8 mm inner diameter and the main current of 30 kA, the plasma conditions at the lasing time were simulated by a one-dimensional Lagrangian Magneto-hydrodynamics (MHD) code and the Ne-like Ar 46.9 nm laser pulses were measured. According to the results, when the inner diameter of the capillary was increased from 3.2 mm to 4.0 mm and 4.8 mm, the intensity of the laser produced at the optimum pressure increased to 1.2 and 2.4 times, respectively. The reasons for laser enhancement were analyzed. When the main current amplitude was increased from 30 kA to 40 kA with the 4.8 mm inner diameter capillary, the laser intensity further increased to 2 times. Therefore, increasing the inner diameter of the capillary in a certain range and increasing the amplitude of the main current with a large inner diameter capillary properly, are effective ways to improve the intensity of 46.9 nm laser

Probing cytotoxicity of nanoparticles and organic compounds using scanning proton microscopy, scanning electron microscopy and fluorescence microscopy

Scanning proton microscopy, scanning electron microscopy (SEM) and fluorescence microscopy have been used to probe the cytotoxicity effect of benzo[a]pyrene (BaP), ethidium bromide (EB) and nanoparticles (ZnO, Al\u2082O\u2083 and TiO\u2082) on a T lymphoblastic leukemia Jurkat cell line. The increased calcium ion (from CaCl2) in the culture medium stimulated the accumulation of BaP and EB inside the cell, leading to cell death. ZnO, Al\u2082O\u2083 and TiO\u2082 nanoparticles, however, showed a protective effect against these two organic compounds. Such inorganic nanoparticles complexed with BaP or EB which became less toxic to the cell. Fe\u2082O\u2083 nanoparticles as an insoluble particle model scavenged by macrophage were investigated in rats. They were scavenged out of the lung tissue about 48 h after infection. This result suggest that some insoluble inorganic nanoparticles of PM (particulate matters) showed protective effects on organic toxins induced acute toxic effects as they can be scavenged by macrophage cells. Whereas, some inorganic ions such as calcium ion in PM may help environmental organic toxins to penetrate cell membrane and induce higher toxic effect.NRC publication: Ye