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  1. It has been recently discovered that the thermosetting matrix of engineering composites can be fully depolymerized in organic solvents through covalent bond exchange reactions (BERs) between the polymer network and solvent molecules. This breakthrough enables the eco-friendly and sustainable recovery of valuable fiber reinforcements using mild processing conditions. However, current investigations have been limited to proof-of-concept experimental demonstrations, leaving unanswered questions regarding the influence of temperature, solvent choice, and fiber arrangement on composite depolymerization performance. These factors are crucial for the commercialization and widespread industrial implementation of this technique. To address this significant knowledge gap, this study aims to establish the relationship between composite depolymerization speed and various material and processing conditions. A multiscale diffusion-reaction computational model is defined based on the finite element method, which links the microscale BER rate to the continuum-level composite depolymerization kinetics. Specifically, it reveals how the processing temperature, solvent diffusivity, fiber content, and fiber arrangement affect the overall composite depolymerization speed. The study enhances our understanding of the underlying mechanisms of composite recycling using organic solvents. As a result, it provides valuable insights for industrial stakeholders, allowing them to optimize depolymerization conditions, make informed material selections, and develop suitable business models for waste management. 
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    Free, publicly-accessible full text available September 1, 2024
  2. Free, publicly-accessible full text available September 30, 2024
  3. We demonstrate a method to obtain homogeneous atom-cavity coupling by selecting and keeping 87Rb atoms that are near maximally coupled to the cavity's standing-wave mode. We select atoms by imposing an AC Stark shift on the ground state hyperfine microwave transition frequency with light injected into the cavity. We then induce a spin flip with microwaves that are resonant for atoms that are near maximally coupled to the cavity mode of interest, after which, we use radiation pressure forces to remove from the cavity all the atoms in the initial spin state. Achieving greater homogeneity in the atom-cavity coupling will potentially enhance entanglement generation, intracavity driving of atomic transitions, cavity-optomechanics, and quantum simulations. This approach can easily be extended to other atomic species with microwave or optical transitions. 
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  4. Abstract Strained materials can exhibit drastically modified physical properties in comparison to their fully relaxed analogues. We report on the x-ray absorption spectra (XAS) and magnetic circular dichroism (XMCD) of a strained NiFe 2 O 4 inverse spinel film grown on a symmetry matched single crystal MgGa 2 O 4 substrate. The Ni XAS spectra exhibit a sizable difference in the white line intensity for measurements with the x-ray electric field parallel to the film plane (normal incidence) vs when the electric field is at an angle (off-normal). A considerable difference is also observed in the Fe L 2,3 XMCD spectrum. Modeling of the XAS and XMCD spectra indicate that the modified energy ordering of the cation 3 d states in the strained film leads to a preferential filling of 3 d states with out-of-plane character. In addition, the results point to the utility of x-ray spectroscopy in identifying orbital populations even with elliptically polarized x-rays. 
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  5. Destruction of pharmaceuticals excreted in urine can be an efficient approach to eliminate these environmental pollutants. However, urine contains high concentrations of chloride, ammonium, and bicarbonate, which may hinder treatment processes. This study evaluated the application of ferrate(VI) (FeVIO42-, Fe(VI)) to oxidize pharmaceuticals (carbamazepine (CBZ), naproxen (NAP), trimethoprim (TMP) and sulfonamide antibiotics (SAs)) in synthetic hydrolyzed human urine and uncovered new effects from urine’s major inorganic constituents. Chloride slightly decreased pharmaceuticals’ removal rate by Fe(VI) due to the ionic strength effect. Ammonium (0.5 M) in undiluted hydrolyzed urine posed a strong scavenging effect, but lower concentrations (≤ 0.25 M) of ammonium enhanced the pharmaceuticals’ degradation by 300 µM Fe(VI), likely due to the reactive ammonium complex form of Fe(V)/Fe(IV). For the first time, bicarbonate was found to significantly promote the oxidation of aniline-containing SAs by Fe(VI) and alter the reaction stoichiometry of Fe(VI) and SA from 4:1 to 3:1. In-depth investigation indicated that bicarbonate not only changed the Fe(VI):SA complexation ratio from 1:2 to 1:1, but provided stabilizing effect for Fe(V) intermediate formed in situ, enabling its degradation of SAs. Overall, results of this study suggested that Fe(VI) is a promising oxidant for the removal of pharmaceuticals in hydrolyzed urine. 
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