We investigate the quasiparticle dynamics in the prototypical heavy fermion CeCoIn5 using ultrafast optical pump-probe spectroscopy. Our results indicate that this material system undergoes ...hybridization fluctuations before the establishment of heavy electron coherence, as the temperature decreases from ∼120 K (T†) to ∼55 K (T*). We reveal that the anomalous coherent phonon softening and damping reduction below T* are directly associated with the emergence of collective hybridization. We also discover a distinct collective mode with an energy of ∼8 meV, which may be experimental evidence of the predicted unconventional density wave. Our findings provide important information for understanding the hybridization dynamics in heavy fermion systems.
Applying a novel approach based on the fusion of social media data, land use data and other information, this paper examines the spatio-temporal patterns of public responses towards urban flooding in ...Nanjing city during July 1–21, 2016. Spatially, “pockets” of high public concern towards urban flooding were found in areas with low altitude, high percentage of water bodies, and rapid urban construction in recent years. Temporally, public responses tend to peak during the rainstorm period, rather than prior to that. Within a day, behavioural and emotional changes in relation to the rainstorm were most discernable during the morning peak hours. Variations in the response among people of different backgrounds, and the impact of urban flooding on different domains of people's daily life have been revealed. Based on the knowledge gained from this study, policy measures are proposed to increase urban flooding resilience, covering both physical infrastructure and human elements.
•Examine the spatio-temporal patterns of public responses towards urban flooding.•Integrate social media data with land use and other information in studying urban resilience towards urban flooding.•Propose policy measures on enhancing urban flooding resilience covering both hardware and software components.
A search for invisible decays of the Lambda baryon is carried out in the process J/psi -> Lambda(Lambda) over bar based on (1.0087 +/- 0.0044) x 10(10) J/psi events collected with the BESIII ...detector located at the BEPCII storage ring. No signals are found for the invisible decays of. baryon, and the upper limit of the branching fraction is determined to be 7.4 x 10(-5) at the 90% confidence level. This is the first search for invisible decays of baryons; such searches will play an important role in constraining dark sector models related to the baryon asymmetry.
Correlation between the feedstock powder and the as-printed products is well expected in laser powder bed fusion (LPBF). However, the inheritance/heredity relationship between the feedstock powder ...and the products remains broadly overlooked since most atomized powders are printed without any modification. This study addresses the inheritance issue through comparing the hydrogenation/dehydrogenation (HDH) Ti powder with the ball-milled (BM) Ti powder, as well as the respective as-printed samples. Rietveld refinement, focused ion beam, electron backscatter diffraction, and transmission electron microscopy are employed to characterize the microstructure; uniaxial tensile tests and fractographic observation are performed for the mechanical analysis; single-track finite element simulations are conducted to reveal the varied powder-bed properties. A “core-shell” powder structure has been generated through the ball milling modification. Nano-crystallites in the “shell” and stress-induced twins have brought significant grain refinement to the BM powder. A β-to-αm massive transformation has been observed in the samples printed using HDH powder, whereas the microstructure changes to fully-martensitic when using BM powder as the feedstock. Excellent mechanical performance (∼1000 MPa tensile strength with ∼20% ductility) have been achieved through inheriting the fine microstructure and oxygen content from the BM powder, which are induced by the powder modification process. This study has therefore unveiled the comprehensive correlation between the feedstock powder and the as-printed Ti, highlighting a novel methodology for developing additively-manufactured, cost-effective, and high-performance materials through tailoring the feedstock powder.
•The influence of ball-milling modification on Ti powder has been clarified.•Systematic comparisons of different feedstock powders and as-printed samples.•The inheritance relationship between feedstock and products has been revealed.•Developing novel materials through tailoring the feedstock powders.
We report a branching fraction measurement of the singly Cabibbo-suppressed decay Λ+c → ΛK+ using a data sample collected with the BESIII detector at the BEPCII storage ring. The data span ...center-of-mass energies from 4.599 to 4.950 GeV and correspond to an integrated luminosity of 6.44 fb −1 . The branching fraction of Λ+c → ΛK+ relative to that of the Cabibbo-favored decay Λ+c → Λπ+ is measured to be R = B(Λ+c → ΛK+) / B(Λ+c → Λπ+) = (4.78±0.34±0.20)%. Combining with the world-average value of B(Λ+c → Λπ+), we obtain B(Λ+c → ΛK+) = (6.21±0.44±0.26±0.34) × 10 −4 . Here the first uncertainties are statistical, the second systematic, and the third comes from the uncertainty of the Λ+c→Λπ+ branching fraction. This result, which is more precise than previous measurements, does not agree with theoretical predictions, and suggests that nonfactorizable contributions have been underestimated in current models.
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