Exciton-polariton based WS2 polarization modulator controlled by optical Stark beam

The recent era of fast optical manipulation and optical devices owe a lot to exciton-polaritons being lighter in mass, faster in speed and stronger in nonlinearity due to hybrid light-matter characteristics. The room temperature existence of polaritons in two dimensional materials opens up new avenues to the design and analysis of all optical devices and has gained the researchers attention. Here, spin-selective optical Stark effect is introduced to form a waveguide effect in uniform community of polaritons, and is used to realize polarization modulation of polaritons. The proposed device basically takes advantage of the spin-sensitive properties of optical Stark effect of polaritons inside the WS2 microcavity so as to guide different modes and modulate polarization of polaritons. It is shown that polaritonic wavepacket of different mode profiles can be generated by changing intensity of the optical Stark beam and the polarization of polaritons can be controlled and changed periodically along the formed waveguide by introduction birefringence that is sensitive to polarization degree of the optical Stark beam

A Densified Binder-jet Printed Powder System Via Viscous-Rearrangement Assisted Sintering

Binder jet 3D printing (BJ3DP) is a non-beam based additive manufacturing technology that can fabricate stress-free metal and ceramic parts with great production efficiency. One of the major challenges for BJ3DP is the consolidation of as-printed green bodies. In preliminary work, gas-atomized Inconel 625 alloy was binder-jetted and isothermal sintered under subsolidus and supersolidus temperatures. Quantitative analyses on 2D sections suggested that under supersolidus sintering, rapid particle rearrangement occurred with the help of a viscous liquid phase, which collapsed large printing defects and facilitated densification. Based on the preliminary results, a new two-step viscous liquid rearrangement assisted (VRA) sintering process was proposed to efficiently densify printed 625 alloy while preventing heavy elemental segregations caused by liquid phase formation in supersolidus sintering. Three-dimensional analyses were performed using X-ray micro-computer tomography (μCT) to quantify the evolution of the microstructure during sintering. This revealed pore defect structures that were attributed to both powder spreading and jetting of the binder. Subsolidus sintering was able to remove those defects attributed to jetting but not all the defects attributed to powder spreading. In contrast, supersolidus sintering in the first step of the VRA process was able to remove all the defects. However, the second step of the VRA process was not able to fully prevent the formation of grain boundary phases on cooling. To further support the attribution of the pore structures to powder spreading and binder jetting, “skin” structures were printed. These samples contained a “core” in which the powder was spread but not jetted surrounded by a “skin” that was both spread and jetted. μCT analysis revealed differences in densification behavior between the “skin” and the “core” that resulted in differential sintering. The microstructure heterogeneity caused by differential sintering could also be repaired by supersolidus sintering

Adaptive Crop Management under Climate Uncertainty: Changing the Game for Sustainable Water Use

Water supplies are projected to become increasingly scarce, driving farmers, energy producers, and urban dwellers towards an urgent and emerging need to improve the effectiveness and the efficiency of water use. Given that agricultural water use is the largest water consumer throughout the U.S. Southwest, this study sought to answer two specific research questions: (1) How does water consumption vary by crop type on a metropolitan spatial scale? (2) What is the impact of drought on agricultural water consumption? To answer the above research questions, 92 Landsat images were acquired to generate fine-resolution daily evapotranspiration (ET) maps at 30 m spatial resolution for both dry and wet years (a total of 1095 ET maps), and major crop types were identified for the Phoenix Active Management Area. The study area has a subtropical desert climate and relies almost completely on irrigation for farming. Results suggest that there are some factors that farmers and water managers can control. During dry years, crops of all types use more water. Practices that can offset this higher water use include double or multiple cropping practice, drought tolerant crop selection, and optimizing the total farmed area. Double and multiple cropping practices result in water savings because soil moisture is retained from one planting to another. Further water savings occur when drought tolerant crop types are selected, especially in dry years. Finally, disproportionately large area coverage of high water consuming crops can be balanced and/or reduced or replaced with more water efficient crops. This study provides strong evidence that water savings can be achieved through policies that create incentives for adopting smart cropping strategies, thus providing important guidelines for sustainable agriculture management and climate adaptation to improve future food security

Search for physics beyond the standard model in top quark production with additional leptons in the context of effective field theory

A search for new physics in top quark production with additional final-state leptons is performed using data collected by the CMS experiment in proton-proton collisions at $\sqrt{s}$ = 13 TeV at the LHC during 2016-2018. The data set corresponds to an integrated luminosity of 138 fb$^{-1}$. Using the framework of effective field theory (EFT), potential new physics effects are parametrized in terms of 26 dimension-six EFT operators. The impacts of EFT operators are incorporated through the event-level reweighting of Monte Carlo simulations, which allows for detector-level predictions. The events are divided into several categories based on lepton multiplicity, total lepton charge, jet multiplicity, and b-tagged jet multiplicity. Kinematic variables corresponding to the transverse momentum ($p_\mathrm{T}$) of the leading pair of leptons and/or jets as well as the $p_\mathrm{T}$ of on-shell Z bosons are used to extract the 95% confidence intervals of the 26 Wilson coefficients corresponding to these EFT operators. No significant deviation with respect to the standard model prediction is found

Observation of new structure in the J/ψ\psiJ/ψ\psi mass spectrum in proton-proton collisions at s\sqrt{s} = 13 TeV

International audienceA search is reported for near-threshold structures in the J/$\psi$J/$\psi$ invariant mass spectrum produced in proton-proton collisions at $\sqrt{s}$ = 13 TeV from data collected by the CMS experiment, corresponding to an integrated luminosity of 135 fb$^{-1}$. A new structure is observed with a significance above 5 standard deviations at a mass of 6552 $\pm$ 10 (stat) $\pm$ 12 (syst) MeV. Another structure with even higher significance is found at a mass of 6927 $\pm$ 9 (stat) $\pm$ 4 (syst) MeV, which is consistent with the X(6900) resonance reported by the LHCb experiment and confirmed by the ATLAS experiment. Evidence for another new structure, with a local significance of 4.1 standard deviations, is found at a mass of 7287$^{+20}_{-18}$ (stat) $\pm$ 5 (syst) MeV. The masses and significances are obtained in a model without considering possible quantum mechanical interference between the resonances. Incorporating this interference provides a better description of the mass spectrum between the resonances and shifts the measured masses by up to 150 MeV