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Abstract The rise of exascale supercomputing has motivated an increase in high‐fidelity computational fluid dynamics (CFD) simulations. The detail in these simulations, often involving shape‐dependent, time‐variant flow domains and low‐speed, complex, turbulent flows, is essential for fueling innovations in fields like wind, civil, automotive, or aerospace engineering. However, the massive amount of data these simulations produce can overwhelm storage systems and negatively affect conventional data management and postprocessing workflows, including iterative procedures such as design space exploration, optimization, and uncertainty quantification. This study proposes a novel sampling method harnessing the signed distance function (SDF) concept: SDF‐biased flow importance sampling (BiFIS) and implicit compression based on implicit neural network representations for transforming large‐size, shape‐dependent flow fields into reduced‐size shape‐agnostic images. Designed to alleviate the above‐mentioned problems, our approach achieves near‐lossless compression ratios of approximately :, reducing the size of a bridge aerodynamics forced‐vibration simulation from roughly to about while maintaining low reproduction errors, in most cases below , which is unachievable with other sampling approaches. Our approach also allows for real‐time analysis and visualization of these massive simulations and does not involve decompression preprocessing steps that yield full simulation data again. Given that image sampling is a fundamental step for any image‐based flow field prediction model, the proposed BiFIS method can significantly improve the accuracy and efficiency of such models, helping any application that relies on precise flow field predictions. The BiFIS code is available onGitHub. 

Strongly bound surface species like alkylamines adsorbed on the Brønsted acid site of aluminosilicate zeolites exhibit negligible rates of molecular desorption, preventing them from achieving an equilibrated state on experimentally relevant timescales that limit the measurement of their adsorption thermodynamics. Through adsorption-assisted desorption, whereby distinct alkylamines facilitate desorption from Brønsted acid sites, we demonstrate that equilibrated states are achieved. Breakthrough adsorption measurements reveal that while 2-butylammonium on a Brønsted acid site is irreversibly adsorbed, it readily undergoes molecular desorption when exposed to a distinct alkylamine like 2-propanamine. As a result, two-adsorbate equilibrium was achieved when exposing Brønsted acid sites of aluminosilicate zeolites to a binary vapor phase alkylamine mixture. By varying relative vapor phase partial pressures and temperatures, we demonstrate the ability to experimentally measure the adsorption enthalpy and entropy of alkylammonium adsorbates on mostly isolated Brønsted acid sites in H-ZSM-5 (Si/Al = 140). A multi-adsorbate Langmuir isotherm was found to quantitatively describe the co-adsorption of alkylamines varying in size and basicity over a wide range of conditions, through which the relative adsorption enthalpy and entropy of alkylamines were measured. Across a homologous family of sec-alkylamines (C3-C5) adsorbed on isolated Brønsted acid sites, a fixed contribution to the enthalpy (19 ± 4 kJ mol CH2-1) and entropy (25 ± 4 J mol CH2-1 K-1) of adsorption per methylene unit of was found to exist, likely resulting from electrostatic interactions between the alkyl chain and surrounding pore environment. 

Hydrogen gas is a promising renewable energy storage medium when produced via water electrolysis, but this process is limited by the sluggish kinetics of the anodic oxygen evolution reaction (OER). Herein, we used a microkinetic model to investigate promoting the OER using programmable oxide catalysts (i.e., forced catalyst dynamics). We found that programmable catalysts could increase current density at a fixed overpotential (100-600× over static rates) or reduce the overpotential required to reach a fixed current density of 10 mA cm-2 (45-140% reduction vs static). In our kinetic parametrization, the key parameters controlling the quality of the catalytic ratchet were the O*-to-OOH* and O*-to-OH* activation barriers. Our findings indicate that programmable catalysts may be a viable strategy for accelerating the OER or enabling lower-overpotential operation, but a more accurate kinetic parametrization is required for precise predictions of performance, ratchet quality, and resulting energy efficiency. 

AbstractIntrinsically disordered proteins (IDPs) are a subset of proteins that lack stable secondary structure. Given their polymeric nature, previous mean-field approximations have been used to describe the statistical structure of IDPs. However, the amino-acid sequence heterogeneity and complex intermolecular interaction network have significantly impeded the ability to get proper approximations. One such case is the intrinsically disordered tail domain of neurofilament low (NFLt), which comprises a 50 residue-long uncharged domain followed by a 96 residue-long negatively charged domain. Here, we measure two NFLt variants to identify the impact of the NFLt two main subdomains on its complex interactions and statistical structure. Using synchrotron small-angle x-ray scattering, we find that the uncharged domain of the NFLt induces attractive interactions that cause it to self-assemble into star-like polymer brushes. On the other hand, when the uncharged domain is truncated, the remaining charged N-terminal domains remain isolated in solution with typical polyelectrolyte characteristics. We further discuss how competing long- and short-ranged interactions within the polymer brushes dominate their ensemble structure and, in turn, their implications on previously observed phenomena in NFL native and diseased states. Graphic abstractVisual schematic of the SAXS measurement results of the Neurofilament-low tail domain IDP (NFLt). NFLts assemble into star-like brushes through their hydrophobic N-terminal domains (marked in blue). In increasing salinity, brush height (h) is initially increased following a decrease while gaining additional tails to their assembly. Isolating the charged sub-domain of the NFLt (marked in red) results in isolated polyelectrolytes 

Abstract Proper regulation of organelle dynamics and inter-organelle contacts is critical for cellular health and function. Both the endoplasmic reticulum (ER) and actin cytoskeleton are known to regulate organelle dynamics, but how, when, and where these two subcellular components are coordinated to control organelle dynamics remains unclear. Here, we show that ER-associated actin consistently marks mitochondrial, endosomal, and lysosomal fission sites. We also show that actin polymerization by the ER-anchored isoform of the formin protein INF2 is a key regulator of the morphology and mobility of these organelles. Together, our findings establish a mechanism by which INF2-mediated polymerization of ER-associated actin at ER-organelle contacts regulates organelle dynamics. 

The confluence of recent discoveries of the roles of biomolecular liquids in living systems and modern abilities to precisely synthesize and modify nucleic acids (NAs) has led to a surge of interest in liquid phases of NAs. These phases can be formed primarily from NAs, as driven by base-pairing interactions, or from the electrostatic combination (coacervation) of negatively charged NAs and positively charged molecules. Generally, the use of sequence-engineered NAs provides the means to tune microsopic particle properties, and thus imbue specific, customizable behaviors into the resulting liquids. In this way, researchers have used NA liquids to tackle fundamental problems in the physics of finite valence soft materials, and to create liquids with novel structured and/or multi-functional properties. Here, we review this growing field, discussing the theoretical background of NA liquid phase separation, quantitative understanding of liquid material properties, and the broad and growing array of functional demonstrations in these materials. We close with a few comments discussing remaining open questions and challenges in the field.