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Beryllium characterization in soils by selective extraction
In the present work, an analytical method has been developed for the determination of the amount of man-made beryllium metal and/or beryllium compounds in soil in addition to the amount of native beryllium that is present. The method is based on the premise that if high-fired beryllium oxide can be extracted efficiently, then beryllium metal and acid-soluble beryllium salts would also be extracted efficiently.
Structural Determinants for Substrate Selectivity in Guanine Deaminase Enzymes of the Amidohydrolase Superfamily
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Ultralow Thermal Conductivity in Diamond-Like Semiconductors: Selective Scattering of Phonons from Antisite Defects
In this work, we discover anomalously low lattice thermal conductivity (<0.25 W/mK at 300 degrees C) in the Hg-containing quaternary diamond-like semiconductors within the Cu2IIBIVTe4 (IIB: Zn, Cd, Hg) (IV: Si, Ge, Sn) set of compositions. Using high-temperature X-ray diffraction, resonant ultrasound spectroscopy, and transport properties, we uncover the critical role of the antisite defects HgCu and CuHg on phonon transport within the Hg-containing systems. Despite the differences in chemistry between Hg and Cu, the high concentration of these antisite defects emerges from the energetic proximity of the kesterite and stannite cation motifs. Our phonon calculations reveal that heavier group IIB elements not only introduce low-lying optical modes, but the subsequent antisite defects also possess unusually strong point defect phonon scattering power. The scattering strength stems from the fundamentally different vibrational modes supported by the constituent elements (e.g., Hg and Cu). Despite the significant impact on the thermal properties, antisite defects do not negatively impact the mobility (>50 cm2/(Vs) at 300 degrees C) in Hg-containing systems, leading to predicted zT > 1.5 in Cu2HgGeTe4 and Cu2HgSnTe4 under optimized doping. In addition to introducing a potentially new p-type thermoelectric material, this work provides (1) a strategy to use the proximity of phase transitions to increase point defect phonon scattering, and (2) a means to quantify the power of a given point defect through inexpensive phonon calculations.
Electrochemical Studies of Selected Lanthanide and Californium Cryptates
Efforts to quantitatively reduce Cf III → Cf II in solution as well as studies of its cyclic voltammetry have been hindered by its scarcity, significant challenges associated with manipulating an unusually intense γ emitter, small reaction scales, the need for nonaqueous solvents, and its radiolytic effects on ligands and solvents. In an effort to overcome these impediments, we report on the stabilization of Cf II by encapsulation in 2.2.2-cryptand and comparisons with the readily reducible lanthanides, Sm 3+ , Eu 3+ , and Yb 3+ . Cyclic voltammetry measurements suggest that Cf III/II displays electrochemical behavior with characteristics of both Sm III/II and Yb III/II . The °E 1/2 values of −1.525 and −1.660 V (vs Fc/Fc + in tetrahydrofuran (THF)) for [Cf(2.2.2-crypt)] 3+/2+ and [Sm(2.2.2-crypt)] 3+/2+ , respectively, are similar. However, the ΔE values upon complexation by 2.2.2-cryptand for Cf III/II more closely parallels Yb III/II with postencapsulation shifts of 705 and 715 mV, respectively, whereas the shift of Sm III/II (520 mV) mirrors that of Eu III/II (524 mV). This suggests more structural similarities between Cf II and Yb II in solution than with Sm II that likely originates from more similar ionic radii and local coordination environments, a supposition that is corroborated by crystallographic and extended X-ray absorption fine structure measurements from other systems. Competitive-ion binding experiments between Eu III/II , Sm III/II , and Yb III/II were also performed and show less favorable binding by Yb III/II . Connectivity structures of [Ln(2.2.2-cryptand)(THF)][BPh 4 ] 2 (Ln = Eu II , Sm II ) are reported to show the important role that THF plays in these redox reactions.
Modeling Nonperturbative Field-Driven Vibronic Dynamics: Selective State Preparation and Nonlinear Spectroscopy
The partially linearized density matrix formalism for nonadiabatic dynamics is adapted to incorporate a classical external electromagentic field into the system Hamiltonian. This advancement encompasses the possibility of describing field-driven dynamics and computing a variety of linear and nonlinear spectroscopic signals beyond the perturbative limit. Here, the capabilities of the developed approach are demonstrated on a simple two-state vibronic model coupled to a bath, for which we (a) perform an exhaustive search in the field parameter space for optimal state preparation and (b) compute time-resolved transient absorption spectroscopy to monitor the effect of different pulse shapes on measurable experimental signals. While no restrictions on the form of the field have to be assumed, we focus here on Gaussian shaped (linearly) chirped pulses.
Co-Casting Highly Selective Dual-Layer Membranes with Disordered Block Polymer Selective Layers
Abstract not provided
Selective Conversion of Carbon Dioxide into Liquid Hydrocarbons and Long-Chain α-Olefins over Fe-Amorphous AlOx Bifunctional Catalysts
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Selective Electrocatalytic Reduction of Nitrous Oxide to Dinitrogen with an Iron Porphyrin Complex
Nitrous oxide (N 2 O) is the third largest contributor to anthropogenic greenhouse gas emissions and plays a detrimental role in the depletion of ozone. Despite the contribution of N 2 O as an atmospheric pollutant, there are currently only a few examples of electrochemical N 2 O remediation to N 2 . Herein we report the electrocatalytic deoxygenation of N 2 O by iron tetraphenylporphyrin (FeTPP) to form N 2 with quantitative Faradaic efficiency and an observed rate of 1.91 s –1 . No degradation was observed after controlled potential electrolysis. Mechanistic investigation of the proposed catalytic steps determined that hydrogen-bond donors are critical for accelerating N 2 O activation and that proton transfer is involved in the rate-determining step.
Electrostatic Control of Shape Selection and Nanoscale Structure in Chiral Molecular Assemblies
Not Available
Structural Basis for the Selective Inhibition of HDAC10, the Cytosolic Polyamine Deacetylase
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Discovery of a JAK3-Selective Inhibitor: Functional Differentiation of JAK3-Selective Inhibition ove
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Environmental, Economic, and Scalability Considerations and Trends of Selected Fuel Economy-Enhancing Biomass-Derived Blendstocks
24 biomass-derived compounds and mixtures, identified based on their physical properties, that could be blended into fuels to improve spark ignition engine fuel economy were assessed for their economic, technology readiness, and environmental viability. These bio-blendstocks were modeled to be produced biochemically, thermochemically, or through hybrid processes. To carry out the assessment, 17 metrics were developed for which each bio-blendstock was determined to be favorable, neutral, or unfavorable. Cellulosic ethanol was included as a reference case. Overall, bio-blendstock yields in biochemical processes were lower than in thermochemical processes, in which all biomass, including lignin, is converted to a product. Bio-blendstock yields were a key determinant in overall viability. Key knowledge gaps included the degree of purity needed for use as a bio-blendstock as compared to a chemical. Less stringent purification requirements for fuels could cut processing costs and environmental impacts. Additionally, more information is needed on the blendability of many of these bio-blendstocks with gasoline to support the technology readiness evaluation. Overall, the technology to produce many of these blendstocks from biomass is emerging and as it matures, these assessments must be revisited. Importantly, considering economic, environmental, and technology readiness factors in addition to physical properties of blendstocks that could be used to boost fuel economy can help spotlight those most likely to be viable in the near term.