Operando probing of the surface chemistry during the Haber-Bosch process.

The large-scale conversion of N2 and H2 into NH3 (refs. 1,2) over Fe and Ru catalysts3 for fertilizer production occurs through the Haber-Bosch process, which has been considered the most important scientific invention of the twentieth century4. The active component of the catalyst enabling the conversion was variously considered to be the oxide5, nitride2, metallic phase or surface nitride6, and the rate-limiting step has been associated with N2 dissociation7-9, reaction of the adsorbed nitrogen10 and also NH3 desorption11. This range of views reflects that the Haber-Bosch process operates at high temperatures and pressures, whereas surface-sensitive techniques that might differentiate between different mechanistic proposals require vacuum conditions. Mechanistic studies have accordingly long been limited to theoretical calculations12. Here we use X-ray photoelectron spectroscopy-capable of revealing the chemical state of catalytic surfaces and recently adapted to operando investigations13 of methanol14 and Fischer-Tropsch synthesis15-to determine the surface composition of Fe and Ru catalysts during NH3 production at pressures up to 1 bar and temperatures as high as 723 K. We find that, although flat and stepped Fe surfaces and Ru single-crystal surfaces all remain metallic, the latter are almost adsorbate free, whereas Fe catalysts retain a small amount of adsorbed N and develop at lower temperatures high amine (NHx) coverages on the stepped surfaces. These observations indicate that the rate-limiting step on Ru is always N2 dissociation. On Fe catalysts, by contrast and as predicted by theory16, hydrogenation of adsorbed N atoms is less efficient to the extent that the rate-limiting step switches following temperature lowering from N2 dissociation to the hydrogenation of surface species.

Direct observation of ultrafast hydrogen bond strengthening in liquid water.

Water is one of the most important, yet least understood, liquids in nature. Many anomalous properties of liquid water originate from its well-connected hydrogen bond network1, including unusually efficient vibrational energy redistribution and relaxation2. An accurate description of the ultrafast vibrational motion of water molecules is essential for understanding the nature of hydrogen bonds and many solution-phase chemical reactions. Most existing knowledge of vibrational relaxation in water is built upon ultrafast spectroscopy experiments2-7. However, these experiments cannot directly resolve the motion of the atomic positions and require difficult translation of spectral dynamics into hydrogen bond dynamics. Here, we measure the ultrafast structural response to the excitation of the OH stretching vibration in liquid water with femtosecond temporal and atomic spatial resolution using liquid ultrafast electron scattering. We observed a transient hydrogen bond contraction of roughly 0.04 Å on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of approximately 1 picosecond. Molecular dynamics simulations reveal the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on femtosecond timescales. Our experiment and simulations unveil the intermolecular character of the water vibration preceding the relaxation of the OH stretch.

Demonstrating Pressure Jumping as a Tool to Address the Pressure Gap in High Pressure Photoelectron Spectroscopy of CO and CO2 Hydrogenation on Rh(211).

Operando probing by x-ray photoelectron spectroscopy (XPS) of certain hydrogenation reactions are often limited by the scattering of photoelectrons in the gas phase. This work describes a method designed to partially circumvent this so called pressure gap. By performing a rapid switch from a high pressure (where acquisition is impossible) to a lower pressure we can for a short while probe a "remnant" of the high pressure surface as well as the time dynamics during the re-equilibration to the new pressure. This methodology is demonstrated using the CO2 and the CO hydrogenation reaction over Rh(211). In the CO2 hydrogenation reaction, the remnant surface of a 2 bar pressure shows an adsorbate distribution which favors chemisorbed CHx adsorbates over chemisorbed CO. This contrasts against previous static operando spectra acquired at lower pressures. Furthermore, the pressure jumping method yields a faster acquisition and more detailed spectra than static operando measurements above 1 bar. In the CO hydrogenation reaction, we observe that CHx accumulated faster during the 275 mbar low pressure regime, and different hypotheses are presented regarding this observation.

Bacterial species in cord blood and their significance in the context of clinical use.

Approximately 90 % of infants born before 28 full weeks(extremely-preterm-infants) receive erythrocyte transfusions in early life. Umbilical cord blood(UCB) has been investigated as an alternative source for erythrocyte transfusions to preterm neonates. This retrospective study aimed to compile/evaluate spectrum of bacteria groups/species intermittently detected in processed UCB at National-Swedish-Cord blood bank, (NS-CBB) during the years 2008-2020. Consecutive data from the years 2008-2020 were investigated. UCB from healthy newborns born after 37 full weeks of gestation was collected following clamping of cord (1 min) through cannulation of umbilical vein(vaginal-and C-section-deliveries). In total, 5194 cord blood units (UCBUs) that met NS-CBB-guidelines for total nucleated-cell-content(TNC) were manufactured from 8875 collections. Of 5194 UCBUs,77,6 % were from vaginal-and 22,4 % from C-section deliveries.Samples(10 mL) were collected from surplus eryhtrocyte fraction post-processing(n = 5194), transferred into BACT/ALERT® aerobic/anaerobic culture flasks and monitored 10 days using BACT/ALERT®-3D-Microbial-Detection-Systems. Positive samples were subcultured and typed for bacterial groups and/or species. Out of 5194 processed sampled UCB units,186 (3,6 %) were discarded due to positive sterility tests, 92 % were detected in samples from vaginal-deliveries and 8 % from C-section-deliveries. In all,16 different groups of bacteria and 27 species were identified. Common bacterial/groups and species were anaerobe gram-negative rods(n = 28),coagulase-negative-staphylococci(n = 21),gram-positive rods(n = 21),anaerobe-gram-positive cocci(n = 20) and viridans-streptococci(n = 13). Extracted from these results,in positive samples(n = 13) from C-section deliveries, bacteria were found:viridans-streptococci(n = 7),Aerococcus-urinae(n = 1), Staphylococcus lugdunensis(n = 1),other coagulase-negative staphylococci(n = 1) or a mix of aerobic/anaerobic bacteria(n = 3). Our results are in alignment with previously published contamination rates in processed UCBUs. Still, results point towards importance of strict microbial monitoring when manufacturing UCBUs to achieve patient-safe- products for stem-cell transplantation/transfusion.

Unveiling a common phase transition pathway of high-density amorphous ices through time-resolved x-ray scattering.

Here, we investigate the hypothesis that despite the existence of at least two high-density amorphous ices, only one high-density liquid state exists in water. We prepared a very-high-density amorphous ice (VHDA) sample and rapidly increased its temperature to around 205 ± 10 K using laser-induced isochoric heating. This temperature falls within the so-called "no-man's land" well above the glass-liquid transition, wherein the IR laser pulse creates a metastable liquid state. Subsequently, this high-density liquid (HDL) state of water decompresses over time, and we examined the time-dependent structural changes using short x-ray pulses from a free electron laser. We observed a liquid-liquid transition to low-density liquid water (LDL) over time scales ranging from 20 ns to 3 µs, consistent with previous experimental results using expanded high-density amorphous ice (eHDA) as the initial state. In addition, the resulting LDL derived both from VHDA and eHDA displays similar density and degree of inhomogeneity. Our observation supports the idea that regardless of the initial annealing states of the high-density amorphous ices, the same HDL and final LDL states are reached at temperatures around 205 K.

Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry.

Knowledge of the temperature dependence of the isobaric specific heat (Cp) upon deep supercooling can give insights regarding the anomalous properties of water. If a maximum in Cp exists at a specific temperature, as in the isothermal compressibility, it would further validate the liquid-liquid critical point model that can explain the anomalous increase in thermodynamic response functions. The challenge is that the relevant temperature range falls in the region where ice crystallization becomes rapid, which has previously excluded experiments. Here, we have utilized a methodology of ultrafast calorimetry by determining the temperature jump from femtosecond X-ray pulses after heating with an infrared laser pulse and with a sufficiently long time delay between the pulses to allow measurements at constant pressure. Evaporative cooling of ∼15-µm diameter droplets in vacuum enabled us to reach a temperature down to ∼228 K with a small fraction of the droplets remaining unfrozen. We observed a sharp increase in Cp, from 88 J/mol/K at 244 K to about 218 J/mol/K at 229 K where a maximum is seen. The Cp maximum is at a similar temperature as the maxima of the isothermal compressibility and correlation length. From the Cp measurement, we estimated the excess entropy and self-diffusion coefficient of water and these properties decrease rapidly below 235 K.

Gambling and Migration - The Role of Culture and Family.

Problem gambling (PG) is a public health concern with severe repercussions for the individual, concerned significant others and the society. Foreign borns generally gamble less but are overrepresented among those with PG. Previous research has suggested that other factors, such as socio-economic status, might explain this, but also that cultural factors might play a role in the relationship to gambling and the development of PG. This qualitative study using content analysis investigates the experiences of and opinions about gambling and PG among 12 males living in Sweden with a migrant background in Afghanistan, the Middle East and North Africa. The results were show that the acculturation process could be a factor in developing PG, as well as a cultural values regarding money and wealth. PG was seen as more stigmatized in the origin country, and the family played a more important role in the rehabilitation of PG compared to the general population. The results of this study could be used to inform preventive and clinical programs to better reach people with a migrant background.

Challenges in downstream dam passage and the effect of dam removal on Atlantic salmon (Salmo salar) smolt migrations.

Migration is critical for life-cycle completion in diadromous fish species. River connectivity is vital in facilitating these large-scale movement events, but the extent of present-day river fragmentation can interfere with these migrations. Fish passage solutions (FPSs) are commonly implemented with the aim of improving river connectivity. In our study, we investigated the performance of two types of FPSs, spill regimes and complete dam removal, on Atlantic salmon (Salmo salar) smolt migrations. We used acoustic telemetry to monitor migration behavior and passage success of 120 wild smolts released in three different groups/sites: one group with two dams to pass to reach the river mouth, a second group with one dam to pass, and a control group without any barriers to pass (upstream of a recently removed hydroelectric dam). Smolt passage probabilities were similar for the two studied dams (87% and 86%) but showed variation in path choice, delay times, and loss rates. Passage success was influenced by several factors, such as body size, diel period, and water temperature, but not flow. Cumulative passage success to the river mouth was 61%, with most individuals being lost within lentic river stretches, either in the forebays of hydroelectric power stations or in naturally wide river stretches. Within the recently rehabilitated river sections (post dam removal), passage speeds were significantly faster than all other sections of the river (post-rehabilitation x¯ = 56.1 km/day) with significantly faster speeds compared to pre-rehabilitation (pre-x¯ = 28.0 km/day). Our findings provide valuable information on the benefits of dam removal and highlight the need for further rehabilitation measures in upriver reaches where barriers still affect downstream passage.

Operando Observation of Oxygenated Intermediates during CO Hydrogenation on Rh Single Crystals.

The CO hydrogenation reaction over the Rh(111) and (211) surfaces has been investigated operando by X-ray photoelectron spectroscopy at a pressure of 150 mbar. Observations of the resting state of the catalyst give mechanistic insight into the selectivity of Rh for generating ethanol from CO hydrogenation. This study shows that the Rh(111) surface does not dissociate all CO molecules before hydrogenation of the O and C atoms, which allows methoxy and other both oxygenated and hydrogenated species to be visible in the photoelectron spectra.

Atom-Specific Probing of Electron Dynamics in an Atomic Adsorbate by Time-Resolved X-Ray Spectroscopy.

The electronic excitation occurring on adsorbates at ultrafast timescales from optical lasers that initiate surface chemical reactions is still an open question. Here, we report the ultrafast temporal evolution of x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) of a simple well-known adsorbate prototype system, namely carbon (C) atoms adsorbed on a nickel [Ni(100)] surface, following intense laser optical pumping at 400 nm. We observe ultrafast (∼100 fs) changes in both XAS and XES showing clear signatures of the formation of a hot electron-hole pair distribution on the adsorbate. This is followed by slower changes on a few picoseconds timescale, shown to be consistent with thermalization of the complete C/Ni system. Density functional theory spectrum simulations support this interpretation.

Concluding remarks: Photoelectron spectroscopy and the future of surface analysis.

The Faraday Discussion on Photoelectron Spectroscopy and the Future of Surface Analysis was held both in person and virtually in London, April 20-22, 2022. In my concluding lecture I have highlighted three different recent directions in the field; (i) in situ and operando, (ii) buried interfaces and (iii) time resolved measurements. I have based my lecture on most recent studies conducted in my research group in all these 3 directions. In particular, the new operando instrument POLARIS, located at the brightest hard X-ray beamline at DESY for photoelectron spectroscopy, has opened new avenues to address important problems in catalysis that are essential for society to become fossil free.

Symmetry-resolved CO desorption and oxidation dynamics on O/Ru(0001) probed at the C K-edge by ultrafast x-ray spectroscopy.

We report on carbon monoxide desorption and oxidation induced by 400 nm femtosecond laser excitation on the O/Ru(0001) surface probed by time-resolved x-ray absorption spectroscopy (TR-XAS) at the carbon K-edge. The experiments were performed under constant background pressures of CO (6 × 10-8 Torr) and O2 (3 × 10-8 Torr). Under these conditions, we detect two transient CO species with narrow 2π* peaks, suggesting little 2π* interaction with the surface. Based on polarization measurements, we find that these two species have opposing orientations: (1) CO favoring a more perpendicular orientation and (2) CO favoring a more parallel orientation with respect to the surface. We also directly detect gas-phase CO2 using a mass spectrometer and observe weak signatures of bent adsorbed CO2 at slightly higher x-ray energies than the 2π* region. These results are compared to previously reported TR-XAS results at the O K-edge, where the CO background pressure was three times lower (2 × 10-8 Torr) while maintaining the same O2 pressure. At the lower CO pressure, in the CO 2π* region, we observed adsorbed CO and a distribution of OC-O bond lengths close to the CO oxidation transition state, with little indication of gas-like CO. The shift toward "gas-like" CO species may be explained by the higher CO exposure, which blocks O adsorption, decreasing O coverage and increasing CO coverage. These effects decrease the CO desorption barrier through dipole-dipole interaction while simultaneously increasing the CO oxidation barrier.

Direct Evidence of Subsurface Oxygen Formation in Oxide-Derived Cu by X-ray Photoelectron Spectroscopy.

Subsurface oxygen has been proposed to be crucial in oxide-derived copper (OD-Cu) electrocatalysts for enhancing the binding of CO intermediates during CO2 reduction reaction (CO2 RR). However, the presence of such oxygen species under reductive conditions still remains debated. In this work, the existence of subsurface oxygen is validated by grazing incident hard X-ray photoelectron spectroscopy, where OD-Cu was prepared by reduction of Cu oxide with H2 without exposing to air. The results suggest two types of subsurface oxygen embedded between the fully reduced metallic surface and the Cu2 O buried beneath: (i) oxygen staying at lattice defects and/or vacancies in the surface-most region and (ii) interstitial oxygen intercalated in metal structure. This study adds convincing support to the presence of subsurface oxygen in OD-Cu, which previously has been suggested to play an important role to mitigate the σ-repulsion of Cu for CO intermediates in CO2 RR.

Ultrafast Adsorbate Excitation Probed with Subpicosecond-Resolution X-Ray Absorption Spectroscopy.

We use a pump-probe scheme to measure the time evolution of the C K-edge x-ray absorption spectrum from CO/Ru(0001) after excitation by an ultrashort high-intensity optical laser pulse. Because of the short duration of the x-ray probe pulse and precise control of the pulse delay, the excitation-induced dynamics during the first picosecond after the pump can be resolved with unprecedented time resolution. By comparing with density functional theory spectrum calculations, we find high excitation of the internal stretch and frustrated rotation modes occurring within 200 fs of laser excitation, as well as thermalization of the system in the picosecond regime. The ∼100 fs initial excitation of these CO vibrational modes is not readily rationalized by traditional theories of nonadiabatic coupling of adsorbates to metal surfaces, e.g., electronic frictions based on first order electron-phonon coupling or transient population of adsorbate resonances. We suggest that coupling of the adsorbate to nonthermalized electron-hole pairs is responsible for the ultrafast initial excitation of the modes.

Serum docosahexaenoic acid levels are associated with brain volumes in extremely preterm born infants.

BACKGROUND: Docosahexaenoic acid (DHA) and arachidonic acid (AA) are important for fetal brain growth and development. Our aim was to evaluate the association between serum DHA and AA levels and brain volumes in extremely preterm infants. METHODS: Infants born at <28 weeks gestational age in 2013-2015, a cohort derived from a randomized controlled trial comparing two types of parenteral lipid emulsions, were included (n = 90). Serum DHA and AA levels were measured at postnatal days 1, 7, 14, and 28, and the area under the curve was calculated. Magnetic resonance (MR) imaging was performed at term-equivalent age (n = 66), and volumes of six brain regions were automatically generated. RESULTS: After MR image quality assessment and area under the curve calculation, 48 infants were included (gestational age mean [SD] 25.5 [1.4] weeks). DHA levels were positively associated with total brain (B = 7.966, p = 0.012), cortical gray matter (B = 3.653, p = 0.036), deep gray matter (B = 0.439, p = 0.014), cerebellar (B = 0.932, p = 0.003), and white matter volume (B = 3.373, p = 0.022). AA levels showed no association with brain volumes. CONCLUSIONS: Serum DHA levels during the first 28 postnatal days were positively associated with volumes of several brain structures in extremely preterm infants at term-equivalent age. IMPACT: Higher serum levels of DHA in the first 28 postnatal days are positively associated with brain volumes at term-equivalent age in extremely preterm born infants. Especially the most immature infants suffer from low DHA levels in the first 28 postnatal days, with little increase over time. Future research is needed to explore whether postnatal fatty acid supplementation can improve brain development and may serve as a nutritional preventive and therapeutic treatment option in extremely preterm infants.

Serum choline in extremely preterm infants declines with increasing parenteral nutrition.

PURPOSE: Choline is an essential nutrient for fetal and infant growth and development. Parenteral nutrition used in neonatal care lack free choline but contain small amounts of lipid-bound choline in the form of phosphatidylcholine (PC). Here, we examined the longitudinal development of serum free choline and metabolically related compounds betaine and methionine in extremely preterm infants and how the concentrations were affected by the proportion of parenteral fluids the infants received during the first 28 postnatal days (PNDs). METHODS: This prospective study included 87 infants born at gestational age (GA) < 28 weeks. Infant serum samples were collected PND 1, 7, 14, and 28, and at postmenstrual age (PMA) 32, 36, and 40 weeks. The serum concentrations of free choline, betaine, and methionine were determined by 1H NMR spectroscopy. RESULTS: The median (25th-75th percentile) serum concentrations of free choline, betaine, and methionine were 33.7 (26.2-41.2), 71.2 (53.2-100.8), and 25.6 (16.4-35.3) µM, respectively, at PND 1. The choline concentration decreased rapidly between PND one and PND seven [18.4 (14.1-26.4) µM], and then increased over the next 90 days, though never reaching PND one levels. There was a negative correlation between a high intake of parenteral fluids and serum-free choline. CONCLUSION: Circulating free choline in extremely preterm infants is negatively affected by the proportion of parenteral fluids administered. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT02760472, April 29, 2016, retrospectively registered.

Anomalous temperature dependence of the experimental x-ray structure factor of supercooled water.

The structural changes of water upon deep supercooling were studied through wide-angle x-ray scattering at SwissFEL. The experimental setup had a momentum transfer range of 4.5 Å-1, which covered the principal doublet of the x-ray structure factor of water. The oxygen-oxygen structure factor was obtained for temperatures down to 228.5 ± 0.6 K. Similar to previous studies, the second diffraction peak increased strongly in amplitude as the structural change accelerated toward a local tetrahedral structure upon deep supercooling. We also observed an anomalous trend for the second peak position of the oxygen-oxygen structure factor (q2). We found that q2 exhibits an unprecedented positive partial derivative with respect to temperature for temperatures below 236 K. Based on Fourier inversion of our experimental data combined with reference data, we propose that the anomalous q2 shift originates from that a repeat spacing in the tetrahedral network, associated with all peaks in the oxygen-oxygen pair-correlation function, gives rise to a less dense local ordering that resembles that of low-density amorphous ice. The findings are consistent with that liquid water consists of a pentamer-based hydrogen-bonded network with low density upon deep supercooling.

PSB33 protein sustains photosystem II in plant chloroplasts under UV-A light.

Plants can quickly and dynamically respond to spectral and intensity variations of the incident light. These responses include activation of developmental processes, morphological changes, and photosynthetic acclimation that ensure optimal energy conversion and minimal photoinhibition. Plant adaptation and acclimation to environmental changes have been extensively studied, but many details surrounding these processes remain elusive. The photosystem II (PSII)-associated protein PSB33 plays a fundamental role in sustaining PSII as well as in the regulation of the light antenna in fluctuating light. We investigated how PSB33 knock-out Arabidopsis plants perform under different light qualities. psb33 plants displayed a reduction of 88% of total fresh weight compared to wild type plants when cultivated at the boundary of UV-A and blue light. The sensitivity towards UV-A light was associated with a lower abundance of PSII proteins, which reduces psb33 plants' capacity for photosynthesis. The UV-A phenotype was found to be linked to altered phytohormone status and changed thylakoid ultrastructure. Our results collectively show that PSB33 is involved in a UV-A light-mediated mechanism to maintain a functional PSII pool in the chloroplast.

Anisotropic X-Ray Scattering of Transiently Oriented Water.

We study the structural dynamics of liquid water by time-resolved anisotropic x-ray scattering under the optical Kerr effect condition. In this way, we can separate the anisotropic scattering decay of 160 fs from the delayed temperature increase of ∼0.1 K occurring at 1 ps and quantify transient changes in the O-O pair distribution function. Polarizable molecular dynamics simulations reproduce well the experiment, indicating transient alignment of molecules along the electric field, which shortens the nearest-neighbor distances. In addition, analysis of the simulated water local structure provides evidence that two hypothesized fluctuating water configurations exhibit different polarizability.

Genetic controls of short- and long-term stomatal CO2 responses in Arabidopsis thaliana.

BACKGROUND AND AIMS: The stomatal conductance (gs) of most plant species decreases in response to elevated atmospheric CO2 concentration. This response could have a significant impact on plant water use in a future climate. However, the regulation of the CO2-induced stomatal closure response is not fully understood. Moreover, the potential genetic links between short-term (within minutes to hours) and long-term (within weeks to months) responses of gs to increased atmospheric CO2 have not been explored. METHODS: We used Arabidopsis thaliana recombinant inbred lines originating from accessions Col-0 (strong CO2 response) and C24 (weak CO2 response) to study short- and long-term controls of gs. Quantitative trait locus (QTL) mapping was used to identify loci controlling short- and long-term gs responses to elevated CO2, as well as other stomata-related traits. KEY RESULTS: Short- and long-term stomatal responses to elevated CO2 were significantly correlated. Both short- and long-term responses were associated with a QTL at the end of chromosome 2. The location of this QTL was confirmed using near-isogenic lines and it was fine-mapped to a 410-kb region. The QTL did not correspond to any known gene involved in stomatal closure and had no effect on the responsiveness to abscisic acid. Additionally, we identified numerous other loci associated with stomatal regulation. CONCLUSIONS: We identified and confirmed the effect of a strong QTL corresponding to a yet unknown regulator of stomatal closure in response to elevated CO2 concentration. The correlation between short- and long-term stomatal CO2 responses and the genetic link between these traits highlight the importance of understanding guard cell CO2 signalling to predict and manipulate plant water use in a world with increasing atmospheric CO2 concentration. This study demonstrates the power of using natural variation to unravel the genetic regulation of complex traits.