The process e+e- → Λ Λ ¯ is studied using data samples at √s = 2.2324, 2.400, 2.800 and 3.080 GeV collected with the BESIII detector operating at the BEPCII collider. The Born cross section is ...measured at √s=2.2324 GeV, which is 1.0 MeV above the Λ Λ ¯ mass threshold, to be 305±$45_{-36}^{+66}$ pb, where the first uncertainty is statistical and the second systematic. The substantial cross section near threshold is significantly larger than that expected from theory, which predicts the cross section to vanish at threshold. The Born cross sections at √s=2.400, 2.800 and 3.080 GeV are measured and found to be consistent with previous experimental results, but with improved precision. Finally, the corresponding effective electromagnetic form factors of Λ are deduced.
Here, in an analysis of a 2.92 fb–1 data sample taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be B(D0 → K–e+νe) = ...(3.505 ± 0.014 ± 0.033)% and B(D0 → π–e+νe) = (0.295 ± 0.004 ± 0.003)%. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f$ $^{K}_{+}$(0)|Vcs| = 0.7172 ± 0.0025 ± 0.0035 and $f$ $^{π}_{+}$(0)|Vcd| = 0.1435 ± 0.0018 ± 0.0009.
Multilayer coatings were prepared on H13k steel substrate by laser cladding, and Fe-based powders mixed with different Mo and Ni contents were used. The microstructure change between layers in the ...multilayer deposit process was analyzed. The effects of Mo and Ni contents on the microstructure, phase transformation, element distribution, and microhardness were also systematically investigated. Results showed that dendrite matrix and interdendrite netlike eutectic structure were found in Fe-based cladding layers. Furthermore, the bonding zone was mainly composed of coarse dendrites because of remelting and reheating induced by secondary energy input. Due to the heat accumulation, relatively large dendrites in the bonding zone and thick bonding zone could be formed in the latter layers rather than in the early layers. The phases of sample 1 and sample 3 at room temperature are martensite, residual austenite, residual δ ferrite, M2B and metal carbide (M23C6, and M7C3). The phases of sample 2 at room temperature are austenite, residual δ ferrite, M2B and metallic carbide (M23C6, and M7C3) because more Ni content leads to the change of solidification mode. With increasing Ni content up to 8 wt %, the microhardness of laser cladding layer decreased from 600 HV0.5 to 400 HV0.5 but was distributed homogenously from the interior region to the bonding zone.
The numbers of psi(3686) events accumulated by the BESIII detector for the data taken during 2009 and 2012 are determined to be (107.0 +/- 0.8)x10(6) and (341.1 +/- 2.1)x10(6), respectively, by ...counting inclusive hadronic events, where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of psi(3686) events for the two data taking periods is (448.1 +/- 2.9) x 10(6).
We presented and demonstrated both n-and p-type vertical C-shaped-channel nanosheet field-effect transistors (VCNFETs) featured with precise control of both channel thickness and gate length. The ...VCNFETs were fabricated by high-quality Si/SiGe epitaxy and atomic layer deposition to obtain nanometer-scale process control and self-aligned high-<inline-formula> <tex-math notation="LaTeX">\textit{k}</tex-math> </inline-formula> metal gate (HKMG). The integration flow is compatible with the process used in the mainstream industry and it can be easily extended to vertically stacked devices. Both the gate length and the channel thickness of the VCNFETs are mainly determined by the thicknesses of Si/SiGe films grown by epitaxy, instead of lithography and etch techniques. Perfect subthreshold swing (SS), small drain-induced barrier lowering (DIBL), and large <inline-formula> <tex-math notation="LaTeX">\textit{I}_{\biosc{on}}</tex-math> </inline-formula>/<inline-formula> <tex-math notation="LaTeX">\textit{I}_{\biosc{off}}</tex-math> </inline-formula> ratio were achieved for both n-and p-VCNFETs due to the crystalline silicon channel and the well-defined doping profiles. The device performance and optimization were also investigated and discussed. Used as access transistors in dynamic random access memory (DRAM) array, VCNFETs were also demonstrated for the potential applications to 10-nm DRAM and beyond.
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•Multilayer coatings mixed different Fe-based powders were investigated.•Microstructure and element distribution between both layers were investigated.•Ni element made alloying ...elements more evenly distributed in the LCed coatings.•Ni element improved impact toughness and corrosion resistance of LCed coatings.•Relationship between hardness and impact toughness of LCed coatings was presented.
Multilayer coatings with Fe-based powders that mixed different elements were prepared in the surface layer of 4Cr5MoSiV1 steel by laser cladding, and the corresponding microstructure and element distribution between both adjacent layers were investigated. Mechanical properties and electrochemical corrosion resistance were subsequently measured and analyzed. Results indicated that there were equiaxed dendrites and netlike eutectic structures at the interfaces between both adjacent layers of multilayer cladding, making the alloying elements more evenly distributed due to the addition of excess Ni element. Furthermore, the introduction and increment of Ni element to the Fe-based alloy significantly improved the impact toughness, and exhibited higher corrosion resistance of the cladding coatings.
In a semimetal, both electrons and holes contribute to the density of states at the Fermi level. The small band overlaps and multiband effects engender novel electronic properties. We show that a ...moderate hydrostatic pressure effectively suppresses the band gap in the elemental semiconductor black phosphorus. An electronic topological transition takes place at approximately 1.2 GPa, above which black phosphorus evolves into a semimetal state that is characterized by a colossal positive magnetoresistance and a nonlinear field dependence of Hall resistivity. The Shubnikov-de Haas oscillations detected in magnetic field reveal the complex Fermi surface topology of the semimetallic phase. In particular, we find a nontrivial Berry phase in one Fermi surface that emerges in the semimetal state, as evidence of a Dirac-like dispersion. The observed semimetallic behavior greatly enriches the material property of black phosphorus and sets the stage for the exploration of novel electronic states in this material.
Using a total of 9.0 fb−1 of e+e− collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes e+e−→γX(3872) with X(3872)→π0χcJ ...for J=0, 1, 2. We report the first observation of X(3872)→π0χc1, a new decay mode of the X(3872), with a statistical significance of more than 5σ for all systematic fit variations. Normalizing to the previously established process e+e−→γX(3872) with X(3872)→π+π−J/ψ, we find B(X(3872)→π0χc1)/B(X(3872)→π+π−J/ψ)=0.88−0.27+0.33±0.10, where the first error is statistical and the second is systematic. We set 90% confidence level upper limits on the corresponding ratios for the decays to π0χc0 and π0χc2 of 19 and 1.1, respectively.
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