Discovery and Characterization of a Metastable Cubic Interstitial Nickel-Carbon System with an Expanded Lattice.

Metastable, , kinetically favored but thermodynamically not stable, interstitial solid solutions of carbon in iron are well-understood. Carbon can occupy the interstitial atoms of the host metal, altering its properties. Alloying of the host metal results in the stabilization of the FeC phases, widening its application.

Quantifying the regime of thermodynamic control for solid-state reactions during ternary metal oxide synthesis.

The success of solid-state synthesis often hinges on the first intermediate phase that forms, which determines the remaining driving force to produce the desired target material. Recent work suggests that when reaction energies are large, thermodynamics primarily dictates the initial product formed, regardless of reactant stoichiometry. Here, we validate this principle and quantify its constraints by performing in situ characterization on 37 pairs of reactants.

Aluminothermic reduction of CeO: mechanism of an economical route to aluminum-cerium alloys.

Cerium oxide is a low-value byproduct of rare-earth mining yet constitutes the largest fraction of the rare earth elements. The reduction of cerium oxide by liquid aluminum is proposed as an energy- and cost-efficient route to produce high-strength Al-Ce alloys. This work investigated the mechanism of a multi-step reduction reaction to facilitate the industrial adaptation of the process.

Self-Limiting Sub-5 nm Nanodiamonds by Geochemistry-Inspired Synthesis.

Controlling diamond structures with nanometer precision is fundamentally challenging owing to their extreme and far-from-equilibrium synthetic conditions. State-of-the-art techniques, including detonation, chemical vapor deposition, mechanical grinding, and high-pressure-high-temperature synthesis, yield nanodiamond particles with a broad distribution of sizes. Despite many efforts, the direct synthesis of nanodiamonds with precisely controlled diameters remains elusive.

Direct Observation of the Pressure-Induced Structural Variation in Gold Nanoclusters and the Correlated Optical Response.

The ability to gradually modify the atomic structures of nanomaterials and directly identify such structural variation is important in nanoscience research. Here, we present the first example of a high-pressure single-crystal X-ray diffraction analysis of atomically precise metal nanoclusters. The pressure-dependent, subangstrom structural evolution of an ultrasmall gold nanoparticle, AuS, has been directly identified.

Anomalous thermal transport under high pressure in boron arsenide.

High pressure represents extreme environments and provides opportunities for materials discovery. Thermal transport under high hydrostatic pressure has been investigated for more than 100 years and all measurements of crystals so far have indicated a monotonically increasing lattice thermal conductivity. Here we report in situ thermal transport measurements in the newly discovered semiconductor crystal boron arsenide, and observe an anomalous pressure dependence of the thermal conductivity.

Zirconium Carbide Mediates Coke-Resistant Methane Dry Reforming on Nickel-Zirconium Catalysts.

Graphitic deposits anti-segregate into Ni nanoparticles to provide restored CH adsorption sites and near-surface/dissolved C atoms, which migrate to the Ni /ZrO interface and induce local Zr C formation. The resulting oxygen-deficient carbidic phase boundary sites assist in the kinetically enhanced CO activation toward CO(g). This interface carbide mechanism allows for enhanced spillover of carbon to the ZrO support, and represents an alternative catalyst regeneration pathway with respect to the reverse oxygen spillover on Ni-CeZr O catalysts.

Atomic-Scale Insights into Nickel Exsolution on LaNiO Catalysts via Electron Microscopy.

Using a combination of bulk and surface characterization techniques, we provide atomic-scale insight into the complex surface and bulk dynamics of a LaNiO perovskite material during heating . Driven by the outstanding activity LaNiO in the methane dry reforming reaction (DRM), attributable to the decomposition of LaNiO during DRM operation into a Ni//LaO composite, we reveal the Ni exsolution dynamics both on a local and global scale by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. To reduce the complexity and disentangle thermal from self-activation and reaction-induced effects, we embarked on a heating experiment in vacuo under comparable experimental conditions in all methods.

Mapping completeness.

Tchoń & Makal [ (2021), , 1006-1017] use numerical simulations to explore the dependence of data completeness on crystal orientation, X-ray energy and diamond anvil cell geometry for high-pressure diffraction experiments. Their completeness heat maps for different Laue classes can be used to guide optimization of high-pressure single-crystal diffraction experiments.

Steering the methanol steam reforming reactivity of intermetallic Cu-In compounds by redox activation: stability formation of an intermetallic compound-oxide interface.

To compare the inherent methanol steam reforming properties of intermetallic compounds and a corresponding intermetallic compound-oxide interface, we selected the Cu-In system as a model to correlate the stability limits, self-activation and redox activation properties with the catalytic performance. Three distinct intermetallic Cu-In compounds - CuIn, CuIn and CuIn - were studied both in an untreated and redox-activated state resulting from alternating oxidation-reduction cycles. The stability of all studied intermetallic compounds during methanol steam reforming (MSR) operation is essentially independent of the initial stoichiometry and all accordingly resist substantial structural changes.

Eye movement alterations in presymptomatic C9orf72 expansion gene carriers.

Objective: The clinical manifestation of amyotrophic lateral sclerosis (ALS) is characterized by motor neuron degeneration, whereas frontotemporal dementia (FTD) patients show alterations of behavior and cognition. Both share repeat expansions in C9orf72 as the most prevalent genetic cause. Before disease-defining symptoms onset, structural and functional changes at cortical level may emerge in C9orf72 carriers.

Exploring microstructures in lower mantle mineral assemblages with synchrotron x-rays.

Understanding dynamics across phase transformations and the spatial distribution of minerals in the lower mantle is crucial for a comprehensive model of the evolution of the Earth's interior. Using the multigrain crystallography technique (MGC) with synchrotron x-rays at pressures of 30 GPa in a laser-heated diamond anvil cell to study the formation of bridgmanite [(Mg,Fe)SiO] and ferropericlase [(Mg,Fe)O], we report an interconnected network of a smaller grained ferropericlase, a configuration that has been implicated in slab stagnation and plume deflection in the upper part of the lower mantle. Furthermore, we isolated individual crystal orientations with grain-scale resolution, provide estimates on stress evolutions on the grain scale, and report {110} twinning in an iron-depleted bridgmanite, a mechanism that appears to aid stress relaxation during grain growth and likely contributes to the lack of any appreciable seismic anisotropy in the upper portion of the lower mantle.

Stress-Induced Structural Transformations in Au Nanocrystals.

Nanocrystals can exist in multiply twinned structures like icosahedron or single crystalline structures like cuboctahedron. Transformations between these structures can proceed through diffusion or displacive motion. Experimental studies on nanocrystal structural transformations have focused on high-temperature diffusion-mediated processes.

Potential Control of Oxygen Non-Stoichiometry in Cerium Oxide and Phase Transition Away from Equilibrium.

Cerium oxide (ceria, CeO) is a technologically important material for energy conversion applications. Its activities strongly depend on redox states and oxygen vacancy concentration. Understanding the functionality of chemical active species and behavior of oxygen vacancy during operation, especially in high-temperature solid-state electrochemical cells, is the key to advance future material design.

Nucleation of Dislocations in 3.9 nm Nanocrystals at High Pressure.

As circuitry approaches single nanometer length scales, it has become important to predict the stability of single nanometer-sized metals. The behavior of metals at larger scales can be predicted based on the behavior of dislocations, but it is unclear if dislocations can form and be sustained at single nanometer dimensions. Here, we report the formation of dislocations within individual 3.

High-pressure strengthening in ultrafine-grained metals.

The Hall-Petch relationship, according to which the strength of a metal increases as the grain size decreases, has been reported to break down at a critical grain size of around 10 to 15 nanometres. As the grain size decreases beyond this point, the dominant mechanism of deformation switches from a dislocation-mediated process to grain boundary sliding, leading to material softening. In one previous approach, stabilization of grain boundaries through relaxation and molybdenum segregation was used to prevent this softening effect in nickel-molybdenum alloys with grain sizes below 10 nanometres.

New Estimator for Gravitational Lensing Using Galaxy and Intensity Mapping Surveys.

We introduce the galaxy intensity mapping cross-correlation estimator (GIMCO), which is a new tomographic estimator for the gravitational lensing potential, based on a combination of intensity mapping (IM) and galaxy number counts. The estimator can be written schematically as IM(z_{f})×galaxy(z_{b})-galaxy(z_{f})×IM(z_{b}) for a pair of distinct redshifts (z_{f},z_{b}); this combination allows to greatly reduce the contamination by density-density correlations, thus isolating the lensing signal. As an estimator constructed only from cross-correlations, it is additionally less susceptible to systematic effects.

Longitudinal brain atrophy distribution in advanced Parkinson's disease: What makes the difference in "cognitive status" converters?

We investigated the brain atrophy distribution pattern and rate of regional atrophy change in Parkinson's disease (PD) in association with the cognitive status to identify the morphological characteristics of conversion to mild cognitive impairment (MCI) and dementia (PDD). T1-weighted longitudinal 3T MRI data (up to four follow-up assessments) from neuropsychologically well-characterized advanced PD patients (n = 172, 8.9 years disease duration) and healthy elderly controls (n = 85) enrolled in the LANDSCAPE study were longitudinally analyzed using a linear mixed effect model and atlas-based volumetry and cortical thickness measures.

Olfactory screening of Parkinson's Disease patients and healthy subjects in China and Germany: A study of cross-cultural adaptation of the Sniffin' Sticks 12-identification test.

Background: Olfactory testing is a useful tool in the differential diagnosis of Parkinson's Disease (PD). Although fast and easy to use, the high intercultural variability of odor detection limits the world-wide use of the most common test sets.

Objective: The aim of this study was to test one of the most commonly used olfactory tests (Sniffin' Sticks 12-identification test) in an adapted version for a Chinese population of healthy subjects and PD patients.

Structural brain signature of cognitive decline in Parkinson's disease: DTI-based evidence from the LANDSCAPE study.

Background: The nonmotor symptom spectrum of Parkinson's disease (PD) includes progressive cognitive decline mainly in late stages of the disease. The aim of this study was to map the patterns of altered structural connectivity of patients with PD with different cognitive profiles ranging from cognitively unimpaired to PD-associated dementia.

Methods: Diffusion tensor imaging and neuropsychological data from the observational multicentre LANDSCAPE study were analyzed.

Implementation and application of the peak scaling method for temperature measurement in the laser heated diamond anvil cell.

A new design for a double-sided high-pressure diamond anvil cell laser heating set-up is described. The prototype is deployed at beamline 12.2.

Effects of pressure on the structure and lattice dynamics of ammonium perchlorate: A combined experimental and theoretical study.

Ammonium perchlorate NHClO (AP) was studied using synchrotron angle-dispersive X-ray powder diffraction (XRPD) and Raman spectroscopy. A diamond-anvil cell was used to compress AP up to 50 GPa at room temperature (RT). Density functional theory (DFT) calculations were performed to provide further insight and comparison to the experimental data.

Fate of Large-Scale Structure in Modified Gravity After GW170817 and GRB170817A.

The coincident detection of gravitational waves (GW) and a gamma-ray burst from a merger of neutron stars has placed an extremely stringent bound on the speed of GWs. We showed previously that the presence of gravitational slip (η) in cosmology is intimately tied to modifications of GW propagation. This new constraint implies that the only remaining viable source of gravitational slip is a conformal coupling to gravity in scalar-tensor theories, while viable vector-tensor theories cannot now generate gravitational slip at all.

Dual-Channel, Molecular-Sieving Core/Shell ZIF@MOF Architectures as Engineered Fillers in Hybrid Membranes for Highly Selective CO Separation.

A novel core/shell porous crystalline structure was prepared using a large pore metal organic framework (MOF, UiO-66-NH, pore size, ∼ 0.6 nm) as core surrounded by a small pore zeolitic imidazolate framework (ZIF, ZIF-8, pore size, ∼ 0.4 nm) through a layer-by-layer deposition method and subsequently used as an engineered filler to construct hybrid polysulfone (PSF) membranes for CO capture.