Using federated data sources and Varian Learning Portal framework to train a neural network model for automatic organ segmentation.

Purpose: In this study we trained a deep neural network model for female pelvis organ segmentation using data from several sites without any personal data sharing. The goal was to assess its prediction power compared with the model trained in a centralized manner.

Methods: Varian Learning Portal (VLP) is a distributed machine learning (ML) infrastructure enabling privacy-preserving research across hospitals from different regions or countries, within the framework of a trusted consortium.

Hydrogen adsorption trends on various metal-doped NiP surfaces for optimal catalyst design.

In this study, we looked at the hydrogen evolution reaction on Mg-, Mo-, Fe-, Co-, V-, and Cu-doped Ni3P2 and Ni3P2 + P terminated Ni2P surfaces. The DFT calculated hydrogen adsorption free energy was employed as a predictor of the materials' catalytic HER activity. Our results indicate that doping can substantially improve the catalytic activity of the Ni3P2 terminated surface.

Hydrogen adsorption trends on Al-doped NiP surfaces for optimal catalyst design.

Nanoparticles of nickel phosphide are promising materials to replace the currently used rare Pt-group metals at cathode-side electrodes in devices for electrochemical hydrogen production. Chemical modification by doping can be used to fine-tune the electrocatalytic activity, but this path requires theoretical, atomic-level support which has not been widely available for Ni-P. We present a density functional theory analysis of Al-doped Ni2P surfaces to identify structural motifs that could contribute to the improved behavior of the catalyst.

Hydrogen adsorption on doped MoS nanostructures.

Electrochemical devices for efficient production of hydrogen as energy carrier rely still largely on rare platinum group metal catalysts. Chemically and structurally modified metal dichalcogenide MoS is a promising substitute for these critical raw materials at the cathode side where the hydrogen evolution reaction takes place. For precise understanding of structure and hydrogen adsorption characteristics in chemically modified MoS nanostructures, we perform comprehensive density functional theory calculations on transition metal (Fe, Co, Ni, Cu) doping at the experimentally relevant MoS surfaces at substitutional Mo-sites.

Hydrogen adsorption on MoS-surfaces: a DFT study on preferential sites and the effect of sulfur and hydrogen coverage.

We report a comprehensive computational study of the intricate structure-property relationships governing the hydrogen adsorption trends on MoS edges with varying S- and H-coverages, as well as provide insights into the role of individual adsorption sites. Additionally, the effect of single- and dual S-vacancies in the basal plane on the adsorption energetics is assessed, likewise with an emphasis on the H-coverage dependency. The employed edge/site-selective approach reveals significant variations in the adsorption free energies, ranging between ∼±1.

Density functional simulation of resonant inelastic X-ray scattering experiments in liquids: acetonitrile.

In this paper we report an experimental and computational study of liquid acetonitrile (HC-C[triple bond, length as m-dash]N) by resonant inelastic X-ray scattering (RIXS) at the N K-edge. The experimental spectra exhibit clear signatures of the electronic structure of the valence states at the N site and incident-beam-polarization dependence is observed as well. Moreover, we find fine structure in the quasielastic line that is assigned to finite scattering duration and nuclear relaxation.

Resonant X-ray emission with a standing wave excitation.

The Borrmann effect is the anomalous transmission of x-rays in perfect crystals under diffraction conditions. It arises from the interference of the incident and diffracted waves, which creates a standing wave with nodes at strongly absorbing atoms. Dipolar absorption of x-rays is thus diminished, which makes the crystal nearly transparent for certain x-ray wave vectors.

Sulphur Kβ emission spectra reveal protonation states of aqueous sulfuric acid.

In this paper we report an X-ray emission study of bulk aqueous sulfuric acid. Throughout the range of molarities from 1 M to 18 M the sulfur Kβ emission spectra from H2SO4 (aq) depend on the molar fractions and related deprotonation of H2SO4. We compare the experimental results with results from emission spectrum calculations based on atomic structures of single molecules and structures from ab initio molecular dynamics simulations.

Intramolecular structure and energetics in supercooled water down to 255 K.

We studied the structure and energetics of supercooled water by means of X-ray Raman and Compton scattering. Under supercooled conditions down to 255 K, the oxygen K-edge measured by X-ray Raman scattering suggests an increase of tetrahedral order similar to the conventional temperature effect observed in non-supercooled water. Compton profile differences indicate contributions beyond the theoretically predicted temperature effect and provide a deeper insight into local structural changes.

X-ray induced dimerization of cinnamic acid: Time-resolved inelastic X-ray scattering study.

A classic example of solid-state topochemical reactions is the ultraviolet-light induced photodimerization of α-trans-cinnamic acid (CA). Here, we report the first observation of an X-ray-induced dimerization of CA and monitor it in situ using nonresonant inelastic X-ray scattering spectroscopy (NRIXS). The time-evolution of the carbon core-electron excitation spectra shows the effects of two X-ray induced reactions: dimerization on a short time-scale and disintegration on a long time-scale.

Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid.

Hydration of sulfuric acid plays a key role in new-particle formation in the atmosphere. It has been recently proposed that proton dynamics is crucial in the stabilization of these clusters. One key question is how water molecules mediate proton transfer from sulfuric acid, and hence how the deprotonation state of the acid molecule behaves as a function concentration.

Inelastic x-ray scattering in heterostructures: electronic excitations in LaAlO₃/SrTiO₃.

We present an investigation of the valence-electron excitation spectra including the collective plasmon modes of SrTiO3, LaAlO3 and their heterostructures with non-resonant inelastic x-ray scattering. We analyse the spectra using calculations based on first principles and atomic multiplet models. We demonstrate the feasibility of performing valence IXS experiments in a total reflection geometry.

Identification of the dye adsorption modes in dye-sensitised solar cells with X-ray spectroscopy techniques: a computational study.

Adsorption geometry of dye molecules can have a substantial impact on the efficiency and functional lifespan of a dye-sensitised solar cell (DSSC) and therefore, its reliable assessment is an important step in engineering more efficient DSSCs. X-ray photoelectron spectroscopy (XPS) of oxygen is empirically proved to be the most efficient technique in distinguishing between the two most occurring adsorption geometries, i.e.

Effect of the hydrophobic alcohol chain length on the hydrogen-bond network of water.

The microscopic structure of the hydrogen-bond network of water-alcohol mixtures was studied using X-ray Raman scattering (XRS). To systematically examine how the hydrogen-bond network of water is affected by an increasing size of the hydrophobic group, small linear alcohols (methanol, ethanol, and propanol) in constant mole fractions were studied. The oxygen K-edge spectra were not altered upon hydration of the alcohols beyond a simple superposition of signals from alcohol and water.

Molecular-level changes of aqueous poly(N-isopropylacrylamide) in phase transition.

We report a Compton scattering study on the molecular-level structural changes of aqueous poly(N-isopropylacrylamide) (PNIPAM) across the conformational phase transition. PNIPAM is a thermoresponsive polymer that changes its conformation in water from the hydrophilic coil state to the collapsed hydrophobic globule state at 32 °C. Combined with density functional theory calculations, the Compton scattering experiments detect two type of changes in the phase transition.

Interplay between temperature-activated vibrations and nondipolar effects in the valence excitations of the CO₂ molecule.

We report a study on the temperature dependence of the valence electron excitation spectrum of CO2 performed using nonresonant inelastic X-ray scattering spectroscopy. The excitation spectra were measured at the temperatures of 300 and 850 K with momentum-transfer values of 0.4-4.

Crystal-field excitations in NiO under high pressure studied by resonant inelastic x-ray scattering.

We report a study on charge-neutral crystal-field (dd) excitations in NiO as a function of applied pressure up to 55 GPa, using resonant inelastic x-ray scattering spectroscopy at the Ni K edge. We find distinct signatures of the pressure-induced modifications to the 3d orbital energies as a function of pressure. These modifications are experimentally evidenced by a subtle splitting of the dd-excitation resonance energies.

Saturation behavior in X-ray Raman scattering spectra of aqueous LiCl.

We report a study on the hydrogen-bond network of water in aqueous LiCl solutions using X-ray Raman scattering (XRS) spectroscopy. A wide concentration range of 0-17 mol/kg was covered. We find that the XRS spectral features change systematically at low concentrations and saturate at 11 mol/kg.

Microscopic structure of water at elevated pressures and temperatures.

We report on the microscopic structure of water at sub- and supercritical conditions studied using X-ray Raman spectroscopy, ab initio molecular dynamics simulations, and density functional theory. Systematic changes in the X-ray Raman spectra with increasing pressure and temperature are observed. Throughout the studied thermodynamic range, the experimental spectra can be interpreted with a structural model obtained from the molecular dynamics simulations.

Contraction of completeness-optimized basis sets: application to ground-state electron momentum densities.

Completeness-optimization is a novel method for the formation of one-electron basis sets. Contrary to conventional methods of basis set generation that optimize the basis set with respect to ground-state energy, completeness-optimization is a completely general, black-box method that can be used to form cost-effective basis sets for any wanted property at any level of theory. In our recent work [J.

Completeness-optimized basis sets: application to ground-state electron momentum densities.

In the current work we apply the completeness-optimization paradigm [P. Manninen and J. Vaara, J.

ERKALE-A flexible program package for X-ray properties of atoms and molecules.

ERKALE is a novel software program for computing X-ray properties, such as ground-state electron momentum densities, Compton profiles, and core and valence electron excitation spectra of atoms and molecules. The program operates at Hartree-Fock or density-functional level of theory and supports Gaussian basis sets of arbitrary angular momentum and a wide variety of exchange-correlation functionals. ERKALE includes modern convergence accelerators such as Broyden and ADIIS and it is suitable for general use, as calculations with thousands of basis functions can routinely be performed on desktop computers.

Temperature dependence of the near-edge spectrum of water.

The interpretation of the oxygen near-edge spectrum of water has been debated intensively. We present new measurements of the temperature dependence of the spectrum and perform a van't Hoff analysis for the pre-edge intensity. Many microscopical and thermodynamic properties of liquid water have been described in the literature in terms of mixture models, which presume the existence of two distinct species with different local structures.

Experimental and computational study of crystalline formic acid composed of the higher-energy conformer.

Crystalline formic acid (FA) is studied experimentally and by first-principles simulations in order to identify a bulk solid structure composed of the higher-energy (cis) conformer. In the experiments, deuterated FA (HCOOD) was deposited in a Ne matrix and transformed to the cis conformer by vibrational excitation of the ground state (trans) form. Evaporation of the Ne host above 13 K prepared FA in a bulk solid state mainly composed of cis-FA.