Experimental determination of the ²⁴Mg I (3s3p)³P₂ lifetime

We present the first experimental determination of the electric-dipole forbidden (3s3p)3P?→(3s2)1S? (M2) transition rate in 2?Mg and compare to state-of-the-art theoretical predictions. Our measurement exploits a magnetic trap isolating the sample from perturbations and a magneto-optical trap as an amplifier converting each 3P?→1S? decay event into millions of photons readily detected. The transition rate is determined to be (4.87 ± 0.3)×10?? s?1 corresponding to a 3P? lifetime of 2050(-110)(+140) sec. This value is in agreement with recent theoretical predictions, and to our knowledge the longest lifetime ever determined in a laboratory environment.     

Cold nuclear matter effects on J/ψ yields as a function of rapidity and nuclear geometry in d+A collisions at sqrt[s(NN)]=200 GeV

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200 GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2相似文献   

Observation of transverse polarization asymmetries of charged pion pairs in e+e- annihilation near √s = 10.58 GeV

The interference fragmentation function translates the fragmentation of a quark with a transverse projection of the spin into an azimuthal asymmetry of two final-state hadrons. In e(+)e(-) annihilation the product of two interference fragmentation functions is measured. We report nonzero asymmetries for pairs of charge-ordered π(+)π(-) pairs, which indicate a significant interference fragmentation function in this channel. The results are obtained from a 672 fb(-1) data sample that contains 711 × 10(6) π(+)π(-) pairs and was collected at and near the Υ(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.     

Improvement of <Emphasis Type="Italic">n</Emphasis>-ZnO/<Emphasis Type="Italic">p</Emphasis>-Si photodiodes by embedding of silver nanoparticles

The photo-current of n-ZnO/p-Si heterojunction photodiodes was improved by embedding Ag nanoparticles in the interface (ZnO/nano-P_Ag/p-Si), and the ratio between photo- and dark-current increased by about three orders more than that of a n-ZnO/p-Si specimen. The improvement in the photo-current resulted from the light scattering of embedded Ag nanoparticles. The I–V curve of n-ZnO/p-Si degraded after thermal treatment (A-ZnO/p-Si) because the silicon robbed the oxygen from ZnO to form amorphous silicon dioxide and left an oxygen vacancy. Notably, the properties of ZnO/nano-P_Ag/p-Si were better in the time-dependent photoresponse under 10 V bias. Ag nanoparticles (15–20 nm) scattered the UV light randomly and increased the probability for the absorption of ZnO to enhance the properties of the photodiode.     

惯性约束聚变反应速率测量

 聚变反应速率是表征惯性约束聚变热核反应的重要参数,为测量聚变反应速率,研制了一套由闪烁体及鼻锥部分、光学系统和条纹相机组成的测量系统。在神光Ⅲ原型装置上利用新研制的聚变反应速率测量系统进行了聚变反应速率测量。在DT中子产额约为10¹⁰条件下,首次获得了聚变反应速率随时间的变化过程。对影响聚变反应速率测量的相关因素进行详细分析后表明,系统的时间分辨力优于30 ps。     

AFM analysis of piezoelectric nanogenerator based on n-diamond/n-ZnO heterojunction

We have demonstrated a high performance piezoelectric nanogenerator by scanning a diamond-coated conductive tip on ZnO nanorod arrays in an AFM system with contact-mode. About 95% ZnO nanorods generate piezoelectric current due to the excellent mechanical and electrical properties of the tip. The tip's nitrogen-doped diamond coating is the key factor to maintain effective physical contact and electrical contact to ZnO nanorods, leading to efficient piezoelectric generation. Rectifying n⁺-n heterojunction is formed when the nitrogen-doped diamond tip contacted with a ZnO nanorod, which plays an important role in accumulating and releasing piezoelectric charges of the piezoelectric nanogenerator. Our research indicates that conductive diamond film is an ideal electrode for this type of piezoelectric nanogenerator.     

Preparation and annealing study of TaNx coatings on WC-Co substrates

To prevent Co diffusion from cemented carbides at high temperatures, we fabricated TaN_x coatings by reactive direct current (d.c.) magnetron sputtering onto 6 wt.% cobalt cemented carbide substrates, to form diffusion barrier layers. Varying the nitrogen flow ratio, N₂/(Ar + N₂), from 0.05 to 0.4 during the sputtering process had a significant effect on coating structure and content. Deposition rate reduced as the nitrogen flow ratio increased. The effects of nitrogen flow ratio on the crystalline characteristics of the TaN_x coatings were examined by X-ray diffraction. The TaN_x coatings annealing conditions were 500, 600, 700, and 800 °C for 4 h in air. We evaluated the performance of the diffusion barrier using both Auger electron spectroscopy depth-profiles and X-ray diffraction techniques. We also investigated oxidation resistance of the TaN_x coatings annealed in air, and under a 50 ppm O₂-N₂ atmosphere, to evaluate the fabricated layers effectiveness as a protective coating for glass molding dies.     

Effects of substrate temperature on the structure and mechanical properties of (TiVCrZrHf)N coatings

The present paper reports the influence of growth conditions on the characteristics of (TiVCrZrHf)N films prepared by rf reactive magnetron sputtering at various substrate temperatures. The nitrogen content is observed to decrease with increasing substrate temperature. The X-ray diffraction results indicate that all (TiVCrZrHf)N films are simple face centered cubic (FCC) structures. Initially, there is an obvious decrease followed by an increase in grain size with the increase in substrate temperature. The lower part of the microstructure has an amorphous structure. A nano grain structure (size ∼1 nm) with a random orientation is also observed above the amorphous structure. The fully dense columnar structure with an fcc crystal phase then starts to develop. Extreme hardness of around 48 GPa is obtained in the present alloy design.     

Enhanced in vitro biocompatibility of ultrafine-grained biomedical NiTi alloy with microporous surface

Bulk ultrafine-grained Ni_50.8Ti_49.2 alloy (UFG-NiTi) was successfully fabricated by equal-channel angular pressing (ECAP) technique in the present study, and to further improve its surface biocompatibility, surface modification techniques including sandblasting, acid etching and alkali treatment were employed to produce either irregularly roughened surface or microporous surface or hierarchical porous surface with bioactivity. The effect of the above surface treatments on the surface roughness, wettability, corrosion behavior, ion release, apatite forming ability and cytocompatibility of UFG-NiTi alloy were systematically investigated with the coarse-grained NiTi alloy as control. The pitting corrosion potential (E_pit) was increased from 393 mV (SCE) to 704 mV (SCE) with sandblasting and further increased to 1539 mV (SCE) with following acid etching in HF/HNO₃ solution. All the above surface treatment increased the apatite forming ability of UFG-NiTi in varying degrees when soaked them in simulated body fluid (SBF). Meanwhile, both sandblasting and acid etching could promote the cytocompatibility for osteoblasts: sandblasting enhanced cell attachment and acid etching increased cell proliferation. The different corrosion behavior, apatite forming ability and cellular response of UFG-NiTi after different surface modifications are attributed to the topography and wettability of the resulting surface oxide layer.     

Rapid synthesis and luminescence of the Eu, Er codoped ZnO quantum-dot chain via chemical precipitation method

ZnO quantum-dot chains codoped with Eu³⁺ and Er³⁺ were synthesized by the chemical precipitation method and the codoping effects on the structures, morphologies and optical properties of the powders were briefly investigated. The X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) results indicated the Eu³⁺ and Er³⁺ were incorporated into the crystal lattice of ZnO host. Transmission electron microscope (TEM) measurements showed the sizes of the ZnO quantum dots decreased with the increase of Eu³⁺ and Er³⁺ doping concentration, and the quantum-dot chains were formed by codoping with Eu³⁺ and Er³⁺. The green emissions in the photoluminescence spectra were attributed to 4f-4f of Er³⁺ inner shell ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 transitions, and the characteristic red emissions of Eu³⁺ ions were attributed to the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions, respectively. Moreover, the red emission of the Eu³⁺ ions gradually decreased with the Er³⁺ ions doping concentration increased, which may be due to the different energy storage centers in the powders.