Irreversible xenon insertion into a small-pore zeolite at moderate pressures and temperatures
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Calculations show that dispersion forces in four-coordinate (Me 2 IPr)Fe(✓NAd)(1-nor) 2 ( 2b ) contribute to greater D(FeR) and subtly slow its migratory insertion relative to the neopentyl analogue.
High energy x-ray characterization methods hold great potential for gaining insight into the behavior of materials and providing comparison datasets for the validation and development of mesoscale modeling tools. A suite of techniques have been developed by the x-ray community for characterizing the 3D structure and micromechanical state of polycrystalline materials; however, combining these techniques with in situ mechanical testing under well characterized and controlled boundary conditions has been challenging due to experimental design requirements, which demand new high-precision hardware as well as access to high-energy x-ray beamlines. We describe the design and performance of a load frame insert with a rotational and axial motion system that has been developed to meet these requirements. An example dataset from a deforming titanium alloy demonstrates the new capability.
One of the simplest and most effective ways to reduce the operating temperature of photovoltaic systems in the field is to reflect unusable, 'sub-bandgap' light with energies below the cell absorber's bandgap energy. In this work, low-refractive index SiO2 nanoparticle films inserted between c-Si wafers and metal electrodes significantly increase the reflectance of sub-bandgap light in fabricated test structures. These films are then integrated into the standard PERC fabrication sequence, revealing that the reflection benefits remains after some processing steps but are lost in certain conditions. The SiO2 nanoparticle films are easily ablated during laser contact opening, but are undesirably etched during post-laser cleaning. After Al metallization, the fully fabricated devices show enhanced sub-bandgap reflection when annealed at moderate temperatures, but energy-dispersive X-ray spectroscopy shows that high-temperature firing causes unwanted Al penetration into the SiO2 nanoparticle film, compromising reflection.
The present invention discloses a device and a method for inserting and positioning a target within a free electron laser, particle accelerator, or other such device that generates or utilizes a beam of energy or particles. The system includes a three-point registration mechanism that insures angular and translational accuracy and repeatability of positioning upon multiple insertions within the same structure.
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In a recent article, Nguyen et al. report the discovery of a new decomposition pathway for small Criegee intermediates. Prior to this publication, the lowest known pathway for decomposition of Criegee intermediates involved ring closure to form a dioxirane followed by ring opening to make a methylenebisoxy biradical, which can then isomerize or decompose via a variety of pathways. The new pathway reported by Nguyen et al. involves the partial cleavage of the OO bond of the Criegee intermediate forming nascent H 2 CO and O( 1 D) fragments. The O( 1 D) fragment then orbits around the H 2 CO fragment in a manner reminiscent of roaming radical reactions and eventually inserts into one of the CH bonds of the H 2 CO fragment leading directly to formic acid. The authors report saddle point geometries for this pathway determined at a number of different levels of theory in which the distance between the oxygen atom and the formaldehyde varies from 2.0 Å to 3.5 Å depending on the level of theory. Density functional theory (DFT) calculations are found to give more compact, planar saddle point structures while coupled cluster, CCSD(T), and complete active space self consistent field, CASSCF, optimizations lead to looser saddle point structures in which the O atom orbits above the plane of the H 2 CO fragment.
During the shutdown of the CERN Large Hadron Collider in 2013-2014, an additional pixel layer was installed between the existing Pixel detector of the ATLAS experiment and a new, smaller radius beam pipe. The motivation for this new pixel layer, the Insertable B-Layer (IBL), was to maintain or improve the robustness and performance of the ATLAS tracking system, given the higher instantaneous and integrated luminosities realized following the shutdown. Because of the extreme radiation and collision rate environment, several new radiation-tolerant sensor and electronic technologies were utilised for this layer. Furthermore, this paper reports on the IBL construction and integration prior to its operation in the ATLAS detector.
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Unlike the more established lithium-ion based energy storage chemistries, the complex intercalation chemistry of multivalent cations in a host lattice is not well understood, especially the relationship between the intercalating species solution chemistry and the prevalence and type of side reactions. Among multivalent metals, a promising model system can be based on nonaqueous Zn2+ ion chemistry. Several examples of these systems support the use of a Zn metal anode, and reversible intercalation cathodes have been reported. This study utilizes a combination of analytical tools to probe the chemistry of a nanostructured delta-MnO2 cathode in association with a nonaqueous acetonitrile-Zn(TFSI)(2) electrolyte and a Zn metal anode. As many of the issues related to understanding a multivalent battery relate to the electrolyte electrode interface, the high surface area of a nanostructured cathode provides a significant interface between the electrolyte and cathode host that maximizes the spectroscopic signal of any side reactions or minor mechanistic pathways. Numerous factors affecting capacity fade and issues associated with the second phase formation including Mn dissolution in heavily cycled Zn/delta-MnO2 cells are presented including dramatic mechanistic differences in the storage mechanism of this couple when compared to similar aqueous electrolytes are noted.
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