Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are ...irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal rate by 50%, facilitating precise and reliable mass-manufacturing of chips for nanoelectronics. We doped the ceria system with titanium, using flame temperatures that facilitate crystallization of the ceria yet retain the titania in a molten state. In conjunction with molecular dynamics simulation, we show that under these conditions, the inner ceria core evolves in a single-crystal spherical shape without faceting, because throughout the crystallization it is completely encapsulated by a molten 1- to 2-nanometer shell of titania that, in liquid state, minimizes the surface energy. The principle demonstrated here could be applied to other oxide systems.
Free-electron lasers have been successfully operated with ultrahigh brightness and excellent transverse coherence at X-ray wavelengths. One of the next goals for further improvements is full ...coherence. An obvious approach is to seed the free-electron laser interaction using a conventional source that has good temporal coherence. Here, we show the first lasing of a free-electron laser with an echo-enabled harmonic generation scheme, which shows great promise for producing coherent lasing at short wavelengths, even in the X-ray regime. The experiment was conducted at a test facility that combines a 135.4 MeV electron accelerator with an amplifier consisting of a series of undulator magnets. Lasing was achieved at the third harmonic of the seed with a gain of ∼100,000 over spontaneous radiation. The measurements show typical exponential growth and excellent spectral characteristics, as well as good intensity stability.
A measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GWth nuclear power reactors of the Daya Bay and Ling Ao nuclear power ...facilities served as intense sources of ν¯e’s. Comparison of the ν¯e rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors (∼1500–1950 m) relative to detectors near the reactors (∼350–600 m) allowed a precise measurement of ν¯e disappearance. More than 2.5 million ν¯e inverse beta-decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (December, 2011–July, 2012) with a subsequent 1013 days using the complete configuration of eight detectors (October, 2012–July, 2015). The ν¯e rate observed at the far detectors relative to the near detectors showed a significant deficit, R=0.949±0.002(stat)±0.002(syst). The energy dependence of ν¯e disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle sin22θ13=0.0841±0.0027(stat)±0.0019(syst) and the effective neutrino mass-squared difference of |Δmee2|=(2.50±0.06(stat)±0.06(syst))×10−3 eV2. Analysis using the exact three-flavor probability found Δm322=(2.45±0.06(stat)±0.06(syst))×10−3 eV2 assuming the normal neutrino mass hierarchy and Δm322=(−2.56±0.06(stat)±0.06(syst))×10−3 eV2 for the inverted hierarchy.
We investigate a new laser-driven spherically convergent plasma fusion scheme (SCPF) that can produce thermonuclear neutrons stably and efficiently. In the SCPF scheme, laser beams of nanosecond ...pulse duration and 10^{14}-10^{15} W/cm^{2} intensity uniformly irradiate the fuel layer lined inside a spherical hohlraum. The fuel layer is ablated and heated to expand inwards. Eventually, the hot fuel plasmas converge, collide, merge, and stagnate at the central region, converting most of their kinetic energy to internal energy, forming a thermonuclear fusion fireball. With the assumptions of steady ablation and adiabatic expansion, we theoretically predict the neutron yield Y_{n} to be related to the laser energy E_{L}, the hohlraum radius R_{h}, and the pulse duration τ through a scaling law of Y_{n}∝(E_{L}/R_{h}^{1.2}τ^{0.2})^{2.5}. We have done experiments at the ShengGuangIII-prototype facility to demonstrate the principle of the SCPF scheme. Some important implications are discussed.
Investigation of helicon wave heating and current drive (CD) in toroidal plasma has been carried out with the ray-tracing code GENRAY. The wave trajectories, profiles of power deposition and ...driven-currents are presented. It is shown that increasing the poloidal launch angle does not change the absorption rate of the wave, but moves the peak of the wave deposition toward the plasma core. Wave frequencies in the range of our interest (460 MHz ∼ 480 MHz) do not change the absorption of the wave. Under low parameter plasmas, we find that both the peak position and magnitude of the wave power deposition are dependent on the launched parallel refractive index n||. With increasing the refractive index, the driving efficiency first increases and then decreases. The parallel refractive index figure of merit for mid-plane launching in HL-2M configuration is 3.2. With high plasma parameters, both the position and magnitude of the driving current are weakly dependent on n||. The magnitude of the driven current is determined by both the absorption rate and the value of ξe, which is related to n||. It is also demonstrated that driven current increases with increase of the core plasma temperature and decrease of the core plasma density. The plasma ohmic current seems do not significantly affect the helicon CD efficiency, but moves the driven current toward the plasma core region and narrows the width of the driven current profile. In addition, the preliminary calculations including scrape-off-layer (SOL) suggest that the power absorption rate loss in SOL is about 5%-20%. These results provide a reference and theoretical basis for the design and construction of HL-2M helicon wave system.
The features of ion and electron fishbone instabilities have been investigated during neutral beam injection (NBI) and electron cyclotron resonance heating (ECRH) on HL-2A. Some new phenomena, such ...as frequency jumps and V-font-style sweeping, have been presented in the paper. Three kinds of i-fishbones, including hybrid sawtooth–fishbone (sawbone), run-on fishbone and classical fishbone, have been identified during NBI. During high power (
P
ECRH
> 0.7 MW) ECRH, the experimental results indicate that the e-fishbone frequencies are higher than those during low power ECRH, and are provided with up- and down-chirping behaviours, and sometimes also with V-font-style sweeping. The periodic mode frequency jumps have also been detected by a soft x-ray array. It is possible to correlate these phenomena with the redistribution of energetic electrons.
It is prevailingly thought that estrogen signaling is not involved in development of estrogen receptor (ER)-negative breast cancer. However, there is evidence indicating that ovariectomy prevents the ...development of both ER-positive and -negative breast cancer, suggesting that estrogen signaling is involved in the development of ER-negative breast cancer. Previously, our laboratory cloned a variant of ER- alpha , ER- alpha 36, and found that ER- alpha 36 mediated nongenomic estrogen signaling and is highly expressed in ER-negative breast cancer cells. In this study, we found that ER- alpha 36 was highly expressed in 10/12 cases of triple-negative breast cancer. We investigated the role of mitogenic estrogen signaling mediated by ER- alpha 36 in malignant growth of triple-negative breast cancer MDA-MB-231 and MDA-MB-436 cells that express high levels of ER- alpha 36 and found that these cells strongly responded to mitogenic estrogen signaling both in vitro and in vivo. Knockdown of ER- alpha 36 expression in these cells using the small hairpin RNA method diminished their responsiveness to estrogen. ER- alpha 36 physically interacted with the EGFR/Src/Shc complex and mediated estrogen-induced phosphorylation of epidermal growth factor receptor (EGFR) and Src. EGFR signaling activated ER- alpha 36 transcription through an AP1 site in the ER- alpha 36 promoter, and ER- alpha 36 expression was able to stabilize EGFR protein. Our results, thus demonstrated that ER- alpha 36 mediates nongenomic estrogen signaling through the EGFR/Src/ERK signaling pathway in ER-negative breast cancer cells and suggested that a subset of ER-negative breast tumors that expresses ER- alpha 36, retains responsiveness to mitogenic estrogen signaling.
The genus
Paphiopedilum
with high ornamental and financial values is sensitive to the chilling temperature, but the underlying physiological and biochemistry mechanism(s) are not clear. The maximum ...quantum yield of photosystem II (PSII) (
F
v
/
F
m
), activities of antioxidant enzymes (SOD, POD, and CAT), malondialdehyde (MDA) content, proline and soluble sugar content were studied in
P. purpuratum
(Lindl.) Stein,
P. dianthum
Tang & F.T. Wang and
P. armeniacum
S.C. Chen & F.Y. Liu during chilling treatment. These three
Paphiopedilum
species displayed significant decreases in
F
v
/
F
m
during chilling treatment, especially in
P. purpuratum
. MDA content was decreased in
P. armeniacum
and
P. dianthum
, but significantly increased in
P. purpuratum
. Proline content was significantly higher in
P. armeniacum
than in
P. dianthum
and
P. purpuratum
, and significantly increased after chilling treatment. The soluble sugar content significantly decreased in
P. purpuratum
but significantly increased in the other species. SOD activity significantly increased while CAT activity significantly decreased in three species after treatment. POD activity significantly increased in
P. purpuratum
but significantly decreased in the other species. In addition, principal component analysis (PCA) was performed and three principal components were extracted with a cumulative contribution rate of 83%. PCA suggested that the effects of chilling stress on the physiological parameters were greatest in
P. purpuratum
and smallest in
P. armeniacum
. These results indicated that
P. purpuratum
was the least cold-tolerant and
P. armeniacum
was the most cold-tolerant among three species of
Paphiopedilum
. Our findings can provide valuable information for the conservation, cultivation, especially for the breeding of cold resistant varieties of
Paphiopedilum
.
In this work, a series of CrAlN coatings with Al/Cr atomic ratio between 0 and 0.6 were deposited on high speed steel substrates by reactive unbalanced magnetron sputtering. The structural, ...mechanical and tribological properties of the as-deposited CrAlN coatings were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction, nanoindentation, and pin-on-disc tribometer experiments. It was found that pure CrN coating exhibited an amorphous structure. With the addition of aluminum, the CrAlN coatings gradually crystallized in the cubic structure, showing a (111) preferential orientation. With increasing aluminum content, coating hardness increased gradually from about 18 GPa up to a maximum value of 30 GPa, and then dropped slightly with further increase in aluminum content. The wear resistance of all the CrAlN coatings is about six times better than that of the pure CrN coating deposited under similar conditions.
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