Publications

A bstract : To examine adolescent depression as a model for unusual emotion regulation, the current study considered the influence of gender, pubertal development, and cortisol on self‐reported mood. Children and adolescents with major depressive disorder ( n = 35 , mean age 12.5 years) were compared with psychiatrically healthy children and adolescents ( n = 36 , mean age 10.5 years). During a three‐day assessment, participants rated their mood at three time points, pubertal development was determined through physical examination, and plasma cortisol was sampled during the second night. Depressed participants experienced less positive affect and more negative affect than did controls. Diagnostic group, gender, and pubertal status interacted to predict negative affect, with depressed adolescent girls experiencing especially high levels of negative affect. Cortisol was generally unrelated to depression and mood. Findings are consistent with emotion‐based models of depression and with the literature on depression and emotion regulation during adolescence.

Fluorophosphate cathodes with the chemical formula NaxV2(PO4)2O2yF3–2y (0 ≤ x ≤ 4, 0 ≤ y ≤ 1) are some of the few known sodium-ion cathode materials with the potential to be competitive with conventional lithium-ion cathodes. However, the experimentally accessible performance of the fluorophosphates remains limited, primarily due to the fact that only half of the theoretical capacity has been reversibly cycled. In this article, we review the extensive body of literature on the fluorophosphate class of sodium-ion cathodes and, in combination with our own ab initio model of the material, investigate the mechanisms underlying the sodium-extraction limitations in the NaxV2(PO4)2F3 (y = 0) fluorophosphate. Specifically, we focus on the potential to reversibly extract sodium beyond the 1 ≤ x ≤ 3 range. We find that this limitation arises from a combination of the high voltage of the V4+/5+ oxidation reaction associated with sodium extraction in the 0 ≤ x ≤ 1 region and a precipitous drop in sodium diffusivity near the x = 1 composition due to the presence of a strong ordering, which prevents the formation of mobile defects in the structure. We conclude that the accessible capacity of NaxV2(PO4)2F3 can potentially be expanded to 0 ≤ x ≤ 3 by introducing defects into the material and reducing the voltage of the transition metal redox couple, both of which can likely be achieved via transition metal substitution and aliovalent anion doping.

Abstract The use of a sacrificial cathode additive that contains a large amount of lithium is one potential solution to compensate for the irreversible capacity loss associated with next‐generation anodes such as silicon. Antifluorite‐type Li 6 CoO 4 has attracted attention as a potential cathode additive owing to its remarkably high theoretical lithium extraction capacity. However, the complex mechanism of lithium extraction as well as the oxygen loss from Li 6 CoO 4 is not well understood. A generalizable computational thermodynamics and experimental framework is presented to understand the lithium‐extraction pathway of Li 6 CoO 4 . It is found that one lithium per formula unit can be topotactically extracted from Li 6 CoO 4 , followed by an irreversible and nontopotactic phase transformation to Li 2 CoO 3 or LiCoO 2 depending on the temperature. The results show that peroxide species may form to charge‐compensate for Li extraction which is undesirable as this can lead to gas release during battery operation. It is suggested that charging Li 6 CoO 4 at an elevated temperature that the electrolyte can withstand, redirects the reaction pathway and prevents the formation of intermediate peroxide species making it an effective and stable sacrificial cathode additive.

An analog RAM has been designed to act as a cache memory for a CNN Universal Machine. Hence, all the non-standard chips are available for the CNN Chipset architecture. Time-multiplexed analog routines in the CNN processor require fast and efficient short-time signal storage in an analog buffer. This can be achieved by an extended sample and hold scheme able to address every sample to specific memory locations. Several arrays of capacitors are multiplexed sharing controlling circuitry and I/O buses. The design has the following key parameters: 637 analog memory cells/mm/sup 2/ with 0.4% accuracy, 100 ns access time and 170 ms storage time (within 1% error).

Dataset of the paper: "Twisted moiré photonic crystal enabled optical vortex generation through bound states in the continuum".

The borylation of aryl and heteroaryl C–H bonds is valuable for the site-selective functionalization of C–H bonds in complex molecules. Iridium catalysts ligated by bipyridine ligands catalyze the borylation of the aryl C–H bonds that are most acidic and least sterically hindered, but predicting the site of borylation in molecules containing multiple arenes is difficult. To address this challenge, we report a hybrid computational model that predicts the Site of Borylation (SoBo) in complex molecules. The SoBo model combines density functional theory, semi-empirical quantum mechanics, cheminformatics, linear regression, and machine learning to predict site selectivity and to extrapolate these predictions to new chemical space. Experimental validation of SoBo showed that the model predicts the major site of borylation of pharmaceutical intermediates with higher accuracy than prior machine-learning models or human experts, demonstrating that SoBo will be useful to guide experiments for the borylation of specific C(sp2)–H bonds during pharmaceutical development.

Despite the importance of the microenvironment in heterogeneous electrocatalysis, its role remains unclear due to a lack of suitable characterization techniques. Multi-step reactions like the electroconversion of CO2 to multicarbons (C2+) are especially relevant considering the potential creation of a unique microenvironment as part of the reaction pathway. To elucidate the significance of the microenvironment during CO2 reduction, we develop on-stream substitution of reactant isotope (OSRI), a new method which relies on the subsequent introduction of CO2 isotopes. Combining electrolytic experiments with a numerical model, this method reveals the presence of a reservoir of CO molecules concentrated near the catalyst surface that influences C2+ formation. Application of OSRI on a Cu nanoparticle (NP) ensemble and an electropolished Cu foil demonstrates that a CO monolayer covering the surface does not provide the amount of CO intermediates necessary to facilitate C-C coupling. Specifically, the C2+ turnover increases only after reaching a density of ~100 CO molecules per surface Cu atom. The Cu NP ensemble satisfies this criterion at an overpotential 100 mV lower than the foil, making it a better candidate for efficient C2+ formation. Furthermore, given the same reservoir size, the ensemble’s intrinsically higher C-C coupling ability is highlighted by the 4-fold higher C2+ turnover it achieves at a more positive potential. The OSRI method provides an improved understanding of how the presence of CO intermediates in the microenvironment impacts C2+ formation during the electroreduction of CO2 on Cu surfaces.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A novel high surface area heterogeneous catalyst based on solution phase colloidal nanoparticle chemistry has been developed. Monodisperse platinum nanoparticles of 1.7-7.1 nm have been synthesized by alcohol reduction methods and incorporated into mesoporous SBA-15 silica during hydrothermal synthesis. Characterization of the Pt/SBA-15 catalysts suggests that Pt particles are located within the surfactant micelles during silica formation leading to their dispersion throughout the silica structure. After removal of the templating polymer from the nanoparticle surface, Pt particle sizes were determined from monolayer gas adsorption measurements. Infrared studies of CO adsorption revealed that CO exclusively adsorbs to atop sites and red-shifts as the particle size decreases suggesting surface roughness increases with decreasing particle size. Ethylene hydrogenation rates were invariant with particle size and consistent with a clean Pt surface. Ethane hydrogenolysis displayed significant structure sensitivity over the size range of 1-7 nm, while the apparent activation energy increased linearly up to a Pt particle size of approximately 4 nm and then remained constant. The observed rate dependence with particle size is attributed to a higher reactivity of coordinatively unsaturated surface atoms in small particles compared to low-index surface atoms prevalent in large particles. The most reactive of these unsaturated surface atoms are responsible for ethane decomposition to surface carbon. The ability to design catalytic structures with tunable properties by rational synthetic methods is a major advance in the field of catalyst synthesis and for the development of accurate structure-function relationships in heterogeneous reaction kinetics.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.