Parity violation in resonant inelastic soft x-ray scattering at entangled core holes.

Resonant inelastic x-ray scattering (RIXS) is a major method for investigation of electronic structure and dynamics, with applications ranging from basic atomic physics to materials science. In RIXS applied to inversion-symmetric systems, it has generally been accepted that strict parity selectivity applies in the sub-kilo-electron volt region. In contrast, we show that the parity selection rule is violated in the RIXS spectra of the free homonuclear diatomic O2 molecule. By analyzing the spectral dependence on scattering angle, we demonstrate that the violation is due to the phase difference in coherent scattering at the two atomic sites, in analogy with Young's double-slit experiment. The result also implies that the interpretation of x-ray absorption spectra for inversion symmetric molecules in this energy range must be revised.

COVID-19 in a Portuguese whole blood donor population.

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), leading to pneumonia and acute respiratory distress syndrome. The COVID-19 pandemic had a major impact on the stock of blood banks worldwide. This study aims to assess the prevalence of COVID-19 in a population of whole blood donors and analyze the possible association between blood group and susceptibility to the disease and the impact of adopting preventive measures against SARS-CoV-2 infection. Material and methods: This retrospective study included all whole blood donors from a Portuguese hospital between July and September 2021. A self-assessment questionnaire was used to collect data on COVID-19 infection, vaccination, and preventive measures. Statistical analysis was performed using Chi-square and Mann-Whitney U tests. Results: The prevalence of COVID-19 in the donor population was 11.96% (n = 97), with only 2 cases of serious illness requiring hospitalization. No association was found between blood group and disease susceptibility. Older men were less likely to adopt preventive measures. The vaccination rate was high, with 84.26% of donors having received at least one dose of the vaccine. Seven donors declined COVID-19 vaccination. Preventive measures did not differ based on COVID-19 infection status or vaccination. Discussion: Although there was a higher frequency of COVID-19 in group A donors, the blood group was not associated with susceptibility to infection. The donor population consisted of young individuals without comorbidities, showing a COVID-19 prevalence like the general population and few severe cases. The high vaccination rate and adoption of preventive measures likely contributed to these findings.

Superficial Tale of Two Functional Groups: On the Surface Propensity of Aqueous Carboxylic Acids, Alkyl Amines, and Amino Acids.

The gas-liquid interface of water is environmentally relevant due to the abundance of aqueous aerosol particles in the atmosphere. Aqueous aerosols often contain a significant fraction of organics. As aerosol particles are small, surface effects are substantial but not yet well understood. One starting point for studying the surface of aerosols is to investigate the surface of aqueous solutions. We review here studies of the surface composition of aqueous solutions using liquid-jet photoelectron spectroscopy in combination with theoretical simulations. Our focus is on model systems containing two functional groups, the carboxylic group and the amine group, which are both common in atmospheric organics. For alkanoic carboxylic acids and alkyl amines, we find that the surface propensity of such amphiphiles can be considered to be a balance between the hydrophilic interactions of the functional group and the hydrophobic interactions of the alkyl chain. For the same chain length, the neutral alkyl amine has a lower surface propensity than the neutral alkanoic carboxylic acid, whereas the surface propensity of the corresponding alkyl ammonium ion is higher than that of the alkanoic carboxylate ion. This different propensity leads to a pH-dependent surface composition which differs from the bulk, with the neutral forms having a much higher surface propensity than the charged ones. In aerosols, alkanoic carboxylic acids and alkyl amines are often found together. For such mixed systems, we find that the oppositely charged molecular ions form ion pairs at the surface. This cooperative behavior leads to a more organic-rich and hydrophobic surface than would be expected in a wide, environmentally relevant pH range. Amino acids contain a carboxylic and an amine group, and amino acids of biological origin are found in aerosols. Depending on the side group, we observe surface propensity ranging from surface-depleted to enriched by a factor of 10. Cysteine contains one more titratable group, which makes it exhibit more complex behavior, with some protonation states found only at the surface and not in the bulk. Moreover, the presence of molecular ions at the surface is seen to affect the distribution of inorganic ions. As the charge of the molecular ions changes with protonation, the effects on the inorganic ions also exhibit a pH dependence. Our results show that for these systems the surface composition differs from the bulk and changes with pH and that the results obtained for single-component solutions may be modified by ion-ion interactions in the case of mixed solutions.

Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory.

By combining results and analysis from cylindrical microjet photoelectron spectroscopy (cMJ-PES) and theoretical simulations, we unravel the microscopic properties of ethanol-water solutions with respect to structure and intermolecular bonding patterns following the full concentration scale from 0 to 100% ethanol content. In particular, we highlight the salient differences between bulk and surface. Like for the pure water and alcohol constituents, alcohol-water mixtures have attracted much interest in applications of X-ray spectroscopies owing to their potential of combining electronic and geometric structure probing. The water mixtures of the two simplest alcohols, methanol and ethanol, have generated particular attention due to their delicate hydrogen bonding networks that underlie their structural and thermodynamic properties. Macroscopically ethanol-water seems to mix very well, however microscopically this is not true. The aberrant thermodynamics of water-alcohol mixtures have been suggested to be caused by energy differences of hydrogen bonding between water-water, alcohol-alcohol and alcohol-water molecules. These networks may perturb the local character of the interaction between X-rays and matter, calling for analysis that go beyond the normally applied local selection and building block rules and that can combine the effects of light-matter, intra- and intermolecular interactions. However, despite decades of ongoing research there are still controversies of the precise nature of hydrogen bonding networks that underlie the mixing of these simple molecules. Our combined analysis indicates that at low concentration ethanol molecules form a film at the surface since ethanol at the surface can expose its hydrophobic part to the vacuum retaining its two (or three) possible hydrogen bonds, while water at the surface cannot retain all its four possible hydrogen bonds. Thus, ethanol at the surface becomes energetically favorable. Ethanol molecules show a tilting angle variation of the C-C axis with respect to the surface normal as large as 60° at very low concentration. In bulk, around ca. ten %, the ethanol oxygen atoms tend to make a third acceptor hydrogen bond to water molecules. At ca. 20 %, there is a U-shaped change in the CH3 to CH2OH binding energy (BE) shift indicating the presence of ring-like agglomerates called clathrate structures. At the surface, between 5 and 25%, ethanol forms a closely packed layer with the smallest C-C tilting angle variation down to ∼20°. Above 25% and below the azeotrope at the surface, ethanol shows an increase in the tilting angle variation, while at very high ethanol concentrations water tends to move to the surface so giving a microscopic explanation of the azeotrope effect. This migration is connected to the presence of longer (shorter) ethanol chains in the bulk (surface). A brief comparison with discussions and predictions from other spectroscopic techniques is also given. We emphasize the execution of an integrated approach that combines molecular structural dynamics with quantum predictions of the core electronic chemical shift, so establishing a protocol with considerable interpretative as well as predictive power for cMJ-PES measurements. We believe that this protocol can valorize cMJ-PES for studies of properties of other alcohol mixtures as well as of binary solutions in general.

An atomistic explanation of the ethanol-water azeotrope.

Ethanol and water form an azeotropic mixture at an ethanol molecular percentage of ∼91% (∼96% by volume), which prohibits ethanol from being further purified via distillation. Aqueous solutions at different concentrations in ethanol have been studied both experimentally and theoretically. We performed cylindrical micro-jet photoelectron spectroscopy, excited by synchrotron radiation, 70 eV above C1s ionization threshold, providing optimal atomic-scale surface-probing. Large model systems have been employed to simulate, by molecular dynamics, slabs of the aqueous solutions and obtain an atomistic description of both bulk and surface regions. We show how the azeotropic behaviour results from an unexpected concentration-dependence of the surface composition. While ethanol strongly dominates the surface and water is almost completely depleted from the surface for most mixing ratios, the different intermolecular bonding patterns of the two components cause water to penetrate to the surface region at high ethanol concentrations. The addition of surface water increases its relative vapour pressure, giving rise to the azeotropic behaviour.

Correction: The molecular structure of the surface of water-ethanol mixtures.

Correction for 'The molecular structure of the surface of water-ethanol mixtures' by Johannes Kirschner et al., Phys. Chem. Chem. Phys., 2021, 23, 11568-11578, DOI: 10.1039/D0CP06387H.

The molecular structure of the surface of water-ethanol mixtures.

Mixtures of water and alcohol exhibit an excess surface concentration of alcohol as a result of the amphiphilic nature of the alcohol molecule, which has important consequences for the physico-chemical properties of water-alcohol mixtures. Here we use a combination of intensity vibrational sum-frequency generation (VSFG) spectroscopy, heterodyne-detected VSFG (HD-VSFG), and core-level photoelectron spectroscopy (PES) to investigate the molecular properties of water-ethanol mixtures at the air-liquid interface. We find that increasing the ethanol concentration up to a molar fraction (MF) of 0.1 leads to a steep increase of the surface density of the ethanol molecules, and an increased ordering of the ethanol molecules at the surface. When the ethanol concentration is further increased, the surface density of ethanol remains more or less constant, while the orientation of the ethanol molecules becomes increasingly disordered. The used techniques of PES and VSFG provide complementary information on the density and orientation of ethanol molecules at the surface of water, thus providing new information on the molecular-scale properties of the surface of water-alcohol mixtures over a wide range of compositions. This information is invaluable in understanding the chemical and physical properties of water-alcohol mixtures.

X-ray Photoelectron Fingerprints of High-Valence Ruthenium-Oxo Complexes along the Oxidation Reaction Pathway in an Aqueous Environment.

Recent advances in operando-synchrotron-based X-ray techniques are making it possible to address fundamental questions related to complex proton-coupled electron transfer reactions, for instance, the electrocatalytic water splitting process. However, it is still a grand challenge to assess the ability of the different techniques to characterize the relevant intermediates, with minimal interference on the reaction mechanism. To this end, we have developed a novel methodology employing X-ray photoelectron spectroscopy (XPS) in connection with the liquid-jet approach to probe the electrochemical properties of a model electrocatalyst, [RuII(bpy)2(py)(OH2)]2+, in an aqueous environment. There is a unique fingerprint of the extremely important higher-valence ruthenium-oxo species in the XPS spectra along the oxidation reaction pathway. Furthermore, a sequential method combining quantum mechanics and molecular mechanics is used to illuminate the underlying physical chemistry of such systems. This study provides the basis for the future development of in-operando XPS techniques for water oxidation reactions.

pH-dependent X-ray Photoelectron Chemical Shifts and Surface Distribution of Cysteine in Aqueous Solution.

The distribution and protonation states of amino acids in water droplets are of considerable concern in studies on the formation of clouds in the atmosphere as well as in many biological contexts. In the present work we use the amino acid cysteine as a prototypical example and explore the protonation states of this molecule in aqueous solution, which are strongly affected by the acidity of the environment and also can show different distributions between surface and bulk. We use a combination of X-ray photoelectron chemical shift measurements, density functional theory calculations of the shifts, and reactive force field molecular dynamics simulations of the underlying structural dynamics. We explore how the photoelectron spectra distinctly reflect the different protonation states that are generated by variation of the solution acidity and how the distribution of these protonation states can differ between bulk and surface regions. At specific pH values, we find that the distribution of the cysteine species at the surface is quite different from that in bulk, in particular, for the appearance in the surface region of species which do not exist in bulk. Some ramifications of this finding are discussed.

Intracranial Dural Arteriovenous Fistula as a Reversible Cause of Dementia: Case Series and Literature Review.

OBJECTIVE: Intracranial dural arteriovenous fistulas (DAVFs) can manifest with a reversible form of dementia and parkinsonism that may be related to medullary venous hypertension and impaired cortical venous drainage. We report a consecutive case series of patients with DAVFs who presented with cognitive decline and report angioarchitecture and outcomes of treatment. METHODS: From a prospectively collected database of 389 cranial DAVFs, we identified patients who presented with progressive dementia. Data collected included demographic characteristics, other presenting symptoms, fistula location and type, preoperative and postoperative imaging findings, and treatment outcomes. Descriptive statistics were reported. RESULTS: Of 389 patients with DAVF, 6 patients with progressive dementia (1.4%) were identified. All patients were male. Mean patient age was 68.6 years. Four patients had superior sagittal sinus DAVFs, 1 patient had a tentorial DAVF, and 1 patient had a transverse sinus DAVF. All patients had evidence of medullary venous hypertension on imaging with either reflux and arterialization of the transmedullary veins or venous congestion of the transmedullary veins. All patients underwent endovascular treatment and had reversal of dementia-related symptoms after a mean follow-up of 6.2 months. CONCLUSIONS: Cognitive decline is a rare but reversible manifestation of DAVFs that have impaired venous drainage of the transmedullary veins and associated medullary venous hypertension.

Ethanol Solvation in Water Studied on a Molecular Scale by Photoelectron Spectroscopy.

Because of the amphiphilic properties of alcohols, hydrophobic hydration is important in the alcohol-water system. In the present paper we employ X-ray photoelectron spectroscopy (XPS) to investigate the bulk and surface molecular structure of ethanol-water mixtures from 0.2 to 95 mol %. The observed XPS binding energy splitting between the methyl C 1s and hydroxymethyl C 1s groups (BES_[CH3-CH2OH]) as a function of the ethanol molar percentage can be divided into different regions: one below 35 mol % with higher values (about 1.53 eV) and one starting at 60 mol % up to 95 mol % with 1.49 eV as an average value. The chemical shifts agree with previous quantum mechanics/molecular mechanics (QM/MM) calculations [ Löytynoja , T. ; J. Phys. Chem. B 2014 , 118 , 13217 ]. According to these calculations, the BES_[CH3-CH2OH] is related to the number of hydrogen bonds between the ethanol and the surrounding molecules. As the ethanol concentration increases, the average number of hydrogen bonds decreases from 2.5 for water-rich mixtures to 2 for pure ethanol. We give an interpretation for this behavior based on how the hydrogen bonds are distributed according to the mixing ratio. Since our experimental data are surface sensitive, we propose that this effect may also be manifested at the interface. From the ratio between the XPS C 1s core lines intensities we infer that below 20 mol % the ethanol molecules have their hydroxyl groups more hydrated and possibly facing the solution's bulk. Between 0.1 and 14 mol %, we show the formation of an ethanol monolayer at approximately 2 mol %. Several parameters are derived for the surface region at monolayer coverage.

Surface Propensity of Atmospherically Relevant Amino Acids Studied by XPS.

Amino acids constitute an important fraction of the water-soluble organic nitrogen (WSON) compounds in aerosols and are involved in many processes in the atmosphere. In this work, we applied X-ray photoelectron spectroscopy (XPS) to study aqueous solutions of four amino acids, glycine, alanine, valine, and methionine, in their zwitterionic forms. We found that amino acids with hydrophilic side chains and smaller size, GLY and ALA, tend to stay in the bulk of the liquid, while the hydrophobic and bigger amino acids, VAL and MET, are found to concentrate more on the surface. We found experimental evidence that the amino acids have preferential orientation relative to the surface, with the hydrophobic side chain being closer to the surface than the hydrophilic carboxylate group. The observed amino acid surface propensity has implications in atmospheric science as the surface interactions play a central role in cloud droplet formation, and they should be considered in climate models.

Hemangioma cavernoso mediastinal / Mediastinal Cavernous Hemangioma

El hemangioma mediastinal es un tumor vascular benigno poco frecuente que representa el 0,5 % de los tumores mediastinales. Se describe el caso de un paciente de 65 años con un tumor de mediastino anterior correspondiente a un hemangioma cavernoso.

The mediastinal hemangioma is a rare benign vascular tumor representing 0.5 % of mediastinal tumors. We describe a case of a 65 year old patient with an anterior tumor of mediastinum corresponding to a cavernous hemangioma.

Surface-Altered Protonation Studied by Photoelectron Spectroscopy and Reactive Dynamics Simulations.

The extent to which functional groups are protonated at aqueous interfaces as compared to bulk is deemed essential to several areas in chemistry and biology. The origin of such changes has been the source of intense debate. We use X-ray photoelectron spectroscopy and all-atom reactive molecular dynamics simulations as two independent methods to probe, at the molecular scale, both bulk and surface distributions of protonated species of cysteine in an aqueous solution. We show that the distribution of the cysteine species at the surface is quite different from that in the bulk. We argue that this finding, however, cannot be simply related to a change in the extent of proton sharing between the two conjugate acid/base pairs that may occur between these two regions. The present theoretical simulations identify species at the surface that are not present in the bulk.

Combinación de fibrosis pulmonar y enfisema / Combination Pulmonary Fibrosis and Emphysema

Objetivo: Describir las manifestaciones en tomografía computarizada de alta resolución (TCAR) de 21 pacientes con diagnóstico de combinación de fibrosis pulmonar y enfisema (CFPE) estudiados en el Hospital Universitario Mayor (HUM). Métodos: Serie de casos, descriptivo. Los 21 pacientes seleccionados cumplían los criterios de CFPE: Enfermedad parenquimatosa difusa con cambios significativos de fibrosis y enfisema mayor del 10 %. Los estudios radiológicos fueron analizados en consenso por dos radiólogos expertos en imágenes del tórax. Los datos clínicos se obtuvieron de la historia clínica y a través de llamadas telefónicas. Resultados: El promedio de edad de los pacientes fue de 67 años. El 68,4 % tenía antecedente de tabaquismo. Las alteraciones más frecuentes en TCAR fueron: opacidades intralobulillares (95,2 %), panal de abejas (95,2 %) y bronquiectasias de tracción (95,2 %). Los patrones de fibrosis y enfisema más frecuentes fueron neumonía intersticial usual (NIU) (54,5 %) y enfisema paraseptal (40,9 %). Predominaron las asociaciones de patrones de fibrosis y enfisema: combinación de patrón de NIU y enfisema paraseptal (33,3 %) y cambios no específicos de fibrosis con enfisema paraseptal (28,6 %). Hubo alta prevalencia de hipertensión pulmonar (81,8 %), sin embargo, el tamaño de muestra analizado fue bajo. Conclusiones: El patrón de NIU y los cambios de enfisema paraseptal fueron la asociación más frecuente, con alta prevalencia de hipertensión pulmonar. Las manifestaciones en TCAR fueron similares a las descritas en trabajos previos. La radiografía presentó un bajo rendimiento para detectar enfisema e hipertensión pulmonar. La mortalidad fue elevada.

Purpose: To describe the findings in high-resolution computed tomography (HRCT) of 21 patients diagnosed with combined pulmonary fibrosis and emphysema (CPFE) studied at the Hospital Universitario Mayor (HUM). Methods: Case series, descriptive. 21 patients studied in the HUM who met the diagnostic criteria of CFPE were selected: Diffuse parenchymal disease with significant changes of fibrosis and presence of emphysema with extension greater than 10%. Radiologic studies were reviewed in consensus by two radiologists experienced in chest images. Clinical data were obtained retrospectively from clinical records and through telephone calls. Results: The mean age of patients was 67 years. 68.4% had a history of smoking. The most frequent alterations in HRCT were: intralobular opacities (95.2%), honeycomb (95.2%) and traction bronchiectasis (95.2%). Patterns of fibrosis and emphysema which were most commonly found were usual interstitial pneumonia (UIP) (54.5%) and paraseptal emphysema (40.9%). The most frequent association patterns were combined NIU pattern and paraseptal emphysema (33.3%) and non-specific changes of fibrosis with paraseptal emphysema (28.6%). The prevalence of pulmonary hypertension in the cases studied was high (81.8%), however the analyzed sample size was low. Conclusions: Combined usual interstitial pneumonia and emphysema paraseptal changes was the most frequent pattern, with a high prevalence of pulmonary hypertension. The HRCT findings were similar to those described in previous studies. The x-ray showed a low capacity for detecting emphysema and pulmonary hypertension. Mortality was high.

Theoretical-experimental study of formic acid photofragmentation in the valence region.

Photoionization and photofragmentation studies of formic acid (HCOOH) are performed for the valence shell electron ionization process. The total and partial ion yield of gaseous HCOOH were collected as a function of photon energy in the ultraviolet region, between 11.12 and 19.57 eV. Measurements of the total and partial ion yield of gaseous formic acid molecule are performed with a time-of-flight mass spectrometer at the Synchrotron Light Brazilian Laboratory. Density functional theory and time dependent density functional theory are employed to calculate the ground and excited electronic state energies of neutral and ionic formic acid as well as their fragments and normal vibration modes. The ionization potential energies, the stability of electronic excited states of HCOOH(+), and the energies of opening fragmentation channels are estimated from theoretical-experimental analysis. Additionally, the main formic acid photofragmentation pathways by exposition of photons within that energy range are determined experimentally. These produced ions primarily have the following mass/charge ratios: 46 (HCOOH(+)), 45 (COOH(+)), 29 (HCO(+)), and 18 (H(2)O(+)).

DNA nucleobase synthesis at Titan atmosphere analog by soft X-rays.

Titan, the largest satellite of Saturn, has an atmosphere chiefly made up of N(2) and CH(4) and includes traces of many simple organic compounds. This atmosphere also partly consists of haze and aerosol particles which during the last 4.5 gigayears have been processed by electric discharges, ions, and ionizing photons, being slowly deposited over the Titan surface. In this work, we investigate the possible effects produced by soft X-rays (and secondary electrons) on Titan aerosol analogs in an attempt to simulate some prebiotic photochemistry. The experiments have been performed inside a high vacuum chamber coupled to the soft X-ray spectroscopy beamline at the Brazilian Synchrotron Light Source, Campinas, Brazil. In-situ sample analyses were performed by a Fourier transform infrared spectrometer. The infrared spectra have presented several organic molecules, including nitriles and aromatic CN compounds. After the irradiation, the brownish-orange organic residue (tholin) was analyzed ex-situ by gas chromatographic (GC/MS) and nuclear magnetic resonance ((1)H NMR) techniques, revealing the presence of adenine (C(5)H(5)N(5)), one of the constituents of the DNA molecule. This confirms previous results which showed that the organic chemistry on the Titan surface can be very complex and extremely rich in prebiotic compounds. Molecules like these on the early Earth have found a place to allow life (as we know) to flourish.

Core localization and sigma* delocalization in the O 1s core-excited sulfur dioxide molecule.

Electron-ion-ion coincidence measurements of sulfur dioxide at discrete resonances near the O 1s ionization edge are reported. The spectra are analyzed using a model based upon molecular symmetry and on the geometry of the molecule. We find clear evidence for molecular alignment that can be ascribed to symmetry properties of the ground and core-excited states. Configuration interaction (CI) calculations indicate geometry changes in accord with the measured spectra. For the SO(2) molecule, however, we find that the localized core hole does not produce measurable evidence for valence localization, since the transition dipole moment is not parallel to a breaking sigma* O-S bond, in contrast to the case of ozone. The dissociation behavior based upon the CI calculations using symmetry-broken orbitals while fixing a localized core-hole site is found to be nearly equivalent to that using symmetry-adapted orbitals. This implies that the core-localization effect is not strong enough to localize the sigma* valence orbital.

Size dependent fragmentation of argon clusters in the soft x-ray ionization regime.

Photofragmentation of argon clusters of average size ranging from 10 up to 1000 atoms is studied using soft x-ray radiation below the 2p threshold and multicoincidence mass spectroscopy technique. For small clusters (=10), ionization induces fast fragmentation with neutral emission imparting a large amount of energy. While the primary dissociation takes place on a picosecond time scale, the fragments undergo slow degradation in the spectrometer on a microsecond time scale. For larger clusters ( >or=100) we believe that we observe the fragmentation pattern of multiply charged species on a time-scale which lasts a few hundred nanoseconds. The reason for these slower processes is the large number of neutral atoms which act as an efficient cooling bath where the excess energy ("heat") dissipates among all degrees of freedom. Further degradation of the photoionic cluster in spectrometer then takes place on the microsecond time scale, similar to small clusters.

Photon energy dependence of fragmentation of small argon clusters.

Photofragmentation of small argon clusters with size below ten atoms is reported. In this size range significant modifications from the electronic properties and geometry take place. When tuning the photon energy through the argon 2p edge, the fragmentation pattern is changed. Specifically, cation dimer production is enhanced at the 2p(32)-->4s resonance, while above the 2p edge almost complete atomization is observed. In both cases, the widths of the peaks in the mass spectra indicate that a large amount of kinetic energy is imparted to the fragment due to the formation of multiply charged clusters. A model based on "Coulomb explosion"-charge separation, simply resulting in a complete atomization of the cluster with no dependence on the photon energy-is insufficient to explain the observed photofragmentation of small clusters.