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During in-situ remediation of contaminated groundwater, a chemical or biological amendment is introduced into the contaminant plume to react with the contaminant. Reactions occur only where the amendment and contaminant are in contact with each other, so active spreading has been proposed to increase the contact area between the two reactants. With active spreading, wells are installed in the vicinity of the contaminant plume and are operated in a pre-defined sequence of injections and extractions to create a spatio-temporally varying flow field that changes the shapes of the reactant plumes, generally leading to an increase in contact area and therefore an increase in reaction. The design of the active spreading system depends on the reaction chemistry of the contaminant. This study considers active spreading scenarios for contaminants with three different types of reactions: (1) non-sorbing aqueous contaminant, A, that degrades irreversibly to a benign chemical, C, through reaction with a non-sorbing aqueous amendment, B; (2) sorbing contaminant, A, the degrades irreversibly to a benign chemical, C, through reaction with a non-sorbing aqueous amendment, B, where sorption of A is independent of the concentration of B; and (3) contaminant, A, that exhibits reversible equilibrium surface complexation with concentrations in the mobile and immobile phases dependent on the concentration of the amendment, B. We compare the active spreading strategies for these three types of reactions and identify the characteristics each strategy that lead to enhanced removal of groundwater contaminants. 

Abstract We present Raman-scattering results for three materials, CeB 6 , TbInO 3 , and YbRu 2 Ge 2 , to illustrate the essential aspects of crystal-field (CF) excitations and quadrupolar fluctuations of 4 f -electron systems. For CF excitations, we illustrate how the 4 f orbits are split by spin-orbit coupling and CF potential by presenting spectra for inter- and intra-multiplet excitations over a large energy range. We discuss identification of the CF ground state and establishment of low-energy CF level scheme from the symmetry and energy of measured CF excitations. In addition, we demonstrate that the CF linewidth is a sensitive probe of electron correlation by virtue of self-energy effect. For quadrupolar fluctuations, we discuss both ferroquadrupolar (FQ) and antiferroquadrupolar (AFQ) cases. Long-wavelength quadrupolar fluctuations of the same symmetry as the FQ order parameter persists well above the transition temperature, from which the strength of electronic intersite quadrupolar interaction can be evaluated. The tendency towards AFQ ordering induces ferromagnetic correlation between neighboring 4 f -ion sites, leading to long-wavelength magnetic fluctuations. 

This Letter reports the first measurement of the oscillation amplitude and frequency of reactor antineutrinos at Daya Bay via neutron capture on hydrogen using 1958 days of data. With over 3.6 million signal candidates, an optimized candidate selection, improved treatment of backgrounds and efficiencies, refined energy calibration, and an energy response model for the capture-on-hydrogen sensitive region, the relative ${\overline{\nu }}_e$rates and energy spectra variation among the near and far detectors gives ${\sin }^{2}2{\theta }_{13}=0.0759_{-0.0049}^{+0.0050}$and $\mathrm{\Delta }{m}_{32}^2=\left(2.72_{-0.15}^{+0.14}\right)\times {10}^{-3}{\mathrm{eV}}^2$assuming the normal neutrino mass ordering, and $\mathrm{\Delta }{m}_{32}^2=(-2.83_{-0.14}^{+0.15})\times {10}^{-3}{\mathrm{eV}}^2$for the inverted neutrino mass ordering. This estimate of ${\sin }^{2}2{\theta }_{13}$is consistent with and essentially independent from the one obtained using the capture-on-gadolinium sample at Daya Bay. The combination of these two results yields ${\sin }^{2}2{\theta }_{13}=0.0833\pm 0.0022$, which represents an 8% relative improvement in precision regarding the Daya Bay full 3158-day capture-on-gadolinium result. Published by the American Physical Society2024