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Crystallinity-dependent structural evolution of CoS2 catalysts for enhanced oxygen evolution reaction
Occurrence characteristics and amplitude-frequency relationship of the Pc5 ULF waves from 3 decades of GOES data
Space-filling discrete helices
Proteins are linear chain molecules that play a central role in life and health. Protein native state folds are modular assemblies of space-filling building blocks of α-helices, β-sheets, and tight turns. Here, we deduce the structures of a countable set of space-filling helical forms of a uniform discrete thick string from first principles with no additional input or adjustable parameters. These forms occur in correspondence with the natural numbers, loosely analogous to the energy levels in a Bohr atom. We find the remarkable result that one of these helical forms is an excellent candidate for an α-helix through seemingly improbable quantum chemistry coincidences that fit the geometrical requirements. Our work suggests that geometry and chemistry are complementary ways of looking at proteins and suggests a route for developing a unified framework for understanding proteins.
A Bayesian approach towards atomically-precise localization in fluorescence microscopy
Theoretical and experimental study into laser-induced gold nanoparticles for superior surface-enhanced raman spectroscopy applications
Connected nanoconfinement effects on glass transition temperature, fragility, and dye translational diffusivity in polystyrene thin films depend on molecular weight
Nanoconfined polymer films often display significantly different glass transition temperature (Tg) values, fragilities, and small-molecule diffusivities compared to their bulk counterparts. Here, we probe these effects in supported polystyrene (PS) films of very low molecular weight (MW, ∼6 kg/mol), motivated by our prior hypothesis linking confinement effects on fragility to those on Tg and dye diffusivity. Using ellipsometry and nonradiative energy transfer-based fluorescence measurements, we show that fragility and dye diffusivity of low-MW PS films remain constant with confinement down to ∼100 nm thickness, differing from high-MW PS films that exhibit significant reductions. This behavior implies no narrowing of the α-relaxation time distribution of low-MW PS with confinement; furthermore, Tg reductions appear only upon confinement to thicknesses ≲50 nm, consistent with previous reports and independent of molecular weight. These results validate the proposed framework connecting confinement effects and demonstrate that fragility governs the susceptibility of polymer dynamics to nanoscale confinement.
A multi-resolution systematically improvable quantum embedding scheme for large-scale surface chemistry calculations
Abstract Predictive simulation of surface chemistry is critical in fields from catalysis to electrochemistry and clean energy generation. Ab-initio quantum many-body methods should offer deep insights into these systems at the electronic level but are limited by their steep computational cost. Here, we build upon state-of-the-art correlated wavefunctions to reliably reach ‘gold standard’ accuracy in quantum chemistry for extended surface chemistry. Efficiently harnessing graphics processing unit acceleration along with systematically improvable multi-resolution techniques, we achieve linear computational scaling up to 392 atoms. These large-scale simulations demonstrate the importance of converging to these extended system sizes, achieving consistency between simulations with different boundary conditions for the interaction of water on a graphene surface. We provide a benchmark for this water-graphene interaction that clarifies the preference for water orientations at the graphene interface. This is extended to the adsorption of carbonaceous molecules on chemically complex surfaces, including metal oxides and metal-organic frameworks, where we consistently achieve chemical accuracy compared to experimental references. This advances the simulation of molecular adsorption on surfaces, enabling reliable and improvable first-principles modeling of such problems by ab-initio quantum many-body methods.
Optimal strategies for managing Hepatitis B Virus (HBV) infection: a comprehensive approach through education, vaccination, and therapy
Quantum paraelectricity in the H-bonded ferroelectrics KH2PO4 and KD2PO4 under pressure
By means of path integral Monte Carlo simulations based on a coarse-grained model parameterized by first-principles calculations, we reproduce the large isotope effect observed in H-bonded KH2PO4 (KDP) and deuterated DKDP, showing that the dramatic shift in the ferroelectric critical temperature Tc upon deuteration is governed by the effective mass and local geometry of hydrogen bonds. We find clear evidence of a quantum paraelectric phase in KDP-type ferroelectrics at high pressures, characterized by a universal critical proton off-centering parameter (δc), independent of isotopic substitution. Remarkably, this universality explains the experimentally observed collapse of the isotope effect under pressure, reinforcing the essential role of geometrical effects. Our results suggest that the emergence of quantum paraelectricity and the universal linear behavior of Tc with δ across chemically diverse systems share a common microscopic origin associated with local proton delocalization within the hydrogen bond network.
Differential topographic organization and retinal inheritance of direction and orientation selectivity in the visual thalamus
Peripheral cytokine levels in patients with idiopathic parkinson’s disease undergoing subthalamic nucleus deep brain stimulation
Quasi-classical trajectory study of the CN− + CH3I reaction on a high-dimensional neural network PES
The gas-phase dynamics of bimolecular nucleophilic substitution (SN2) reactions have been extensively studied by both experimental and theoretical groups due to their broad applicability and the emergence of new mechanistic insights. The reaction between CN− and CH3I is particularly intriguing, as it can yield two isomeric products (NCCH3 or CNCH3 + I−) owing to the ambident nature of the CN− nucleophile. Previous velocity map imaging experiments revealed predominantly direct rebound dynamics and high internal energy excitation in the reaction products. In another study, direct dynamics simulations were performed employing the PM7 semi-empirical method and B3LYP/aug-cc-pVDZ/ECP density functional theory (DFT); however, these approaches were limited by an insufficient number of DFT trajectories (due to high computational costs) and an overestimation of hydrogen transfer reactions with PM7. In the present study, a high-dimensional neural network-based potential energy surface (PES) was developed using extensive electronic structure data. The PES was rigorously validated using established benchmarks and subsequently employed in quasi-classical trajectory simulations. A substantial number of reactive trajectories were generated, enabling a detailed analysis of the reaction dynamics. The simulation results are consistent with previous findings and provide new insights into the mechanistic pathways of this SN2 reaction.
Reply to Brandes et al.: A first step, not a final word, on modeling microplastics-induced crop losses
Non-volatile tuning of cryogenic silicon photonic micro-ring modulators
A machine solution for math word problems based on semantic understanding enhancement
Exchange-driven self-diffusion of nanoscale crystalline parahydrogen clusters on graphite
Computer simulations yield evidence of superfluid behavior of nanoscale size clusters of parahydrogen adsorbed on a graphite substrate at low temperature (T ≲ 0.25 K). Clusters with a number of molecules between 7 and 12 display concurrent superfluidity and crystalline order, reflecting the corrugation of the substrate. Remarkably, it is found that specific clusters with a number of molecules ranging between 7 and 12 self-diffuse on the surface like free particles, despite the strong pinning effect of the substrate. This effect is underlain by coordinated quantum-mechanical exchanges of groups of identical molecules; that is, it has no classical counterpart.
Rapid retreat of Berry Glacier, West Antarctica, linked to seawater intrusions revealed by radar interferometry
Abstract We employ a time series of ERS-1/2, ALOS-1/2 PALSAR, Sentinel-1, COSMO-SkyMed, and RCM differential synthetic-aperture radar interferometry data from 1996 to 2023 to document the short and long-term migrations of the grounding line (GL) of Berry Glacier, West Antarctica, a tributary of Getz Ice Shelf that controls 10% of its ice discharge. In 2019–2021, we detected a short-term GL migration of 18.0 ± 0.9 km, which is exceptionally long and implies that the glacier bed is up to 1300 m deeper than previously known. On short time scales, the GL migrates between three states controlled by bed topography. The observed flexing of the glacier suggests that seawater is trapped in the newly formed ice shelf cavity in an irregular fashion during the tidal cycle. From 1996 to 2021, the most inland position of the GL retreated by 18.1 ± 0.4 km, or 0.7 km/year, the ice thickness decreased by 11 ± 1 m/year, the ice sped up by 64 ± 5%, and the glacier lost a total mass of 131 ± 23 Gt. We attribute the rapid retreat to an enhanced ocean heat flux from warm Circumpolar Deep Water (CDW) reaching the grounding line through favorable bathymetry channels, combined with km-sized seawater intrusions beneath the glacier that cause rapid melting of basal ice.