Highly Active W2C-Based Composites for the HER in Alkaline Solution: the Role of Surface Oxide Species

The hydrogen evolution reaction (HER) is a crucial electrochemical process for the proposed hydrogen economy since it has the potential to provide pure hydrogen for fuel cells. Nowadays, hydrogen electroproduction is considerably expensive, so promoting the development of new non-noble catalysts for the cathode of alkaline electrolyzers appears as a suitable way to reduce the costs of this technology. In this sense, a series of tungsten-based carbide materials have been synthesized by the urea-glass route as candidates to improve the HER in alkaline media. Moreover, two different pyridinium-based ionic liquids were employed to modify the surface of the carbide grains and control the amount and nature of their surface species. The main results indicate that the catalyst surface composition is modified in the hybrid materials, which are then distinguished by the appearance of tungsten suboxide structures. This implies the action of ionic liquids as reducing agents. Consequently, differential electrochemical mass spectrometry (DEMS) is used to precisely determine the onset potentials and rate-determining steps (RDS) for the HER in alkaline media. Remarkably, the modified surfaces show high catalytic performance (overpotentials between 45 and 60 mV) and RDS changes from Heyrovsky-Volmer to Heyrovsky as the surface oxide structures get reduced. H2O molecule reduction is then faster at tungsten suboxide, which allows the formation of the adsorbed hydrogen at the surface, boosting the catalytic activity and the kinetics of the alkaline HER.

Self-perceived body weight and weight status: analysis of concordance by age group and sex

OBJECTIVES

Previous studies suggest that there is discordance between actual weight status and body-weight perception. This fact has implications when it comes to designing public health interventions. The aim of this study was to estimate the prevalence of the different categories of weight status and body-weight perception and to analyse their concordance in a representative Spanish population sample.

STUDY DESIGN

Cross-sectional study.

METHODS

Data were sourced from the 2018 Galician Risk Behaviour Data System, with the target population being all persons aged 16 years and above. We collected data on self-perceived body weight and assessed weight status on the basis of body mass index (BMI). BMI was estimated using self-reported measures of weight and height. To estimate concordance, Cohen's kappa coefficient, both unweighted and weighted with Cicchetti weights, was calculated.

RESULTS

Data were obtained for 7853 individuals aged 16 years and above, whereas the overall unweighted concordance was 0.393 (95%CI: 0.377-0.409), with an agreement percentage of 61.6%, weighted concordance was 0.503 (0.490-0.517), with an agreement percentage of 86.6%. The highest concordance between self-perceived body weight and weight status was observed in women. By age group, the highest concordance was observed in the youngest group (16-24 years) for the BMI categories of underweight and overweight, and in the 45-64 age group for the category of obesity.

CONCLUSIONS

The results highlight the existence of differences between self-perceived body weight and weight status, according to sex and age.

Electron stimulated desorption from condensed benzene

The electron induced dissociation of condensed benzene (C6H6) in thin films deposited on a Pt substrate is investigated by electron stimulated desorption (ESD) of anions and cations. The desorbed yields are recorded as a function of incident electron energy in the range of 10 to 950 eV for a fixed film thickness of 2 monolayers (ML) and for a fixed energy of 950 eV, as well as a function of film thickness from 0.5 to 8 monolayers (ML) for anions, and from 0.5 to 12ML for cations. Both energy and thickness dependencies are discussed in terms of the three main mechanisms yielding positively and/or negatively charged fragments: dissociative electron attachment (DEA), dipolar dissociation (DD) and dissociative ionization (DI) processes. At the probed energies, DD is the major mechanism, while DEA is predominantly induced by secondary electrons from the Pt substrate. Desorption of the parent positive ion is strongly suppressed. Similar qualitative behaviours are observed for the energy dependence of both anion and cation ESD yields, while some discrepancies exist in the thickness dependence, including a very significant systematic magnitude difference found between such ions formation. An estimation of the effective DD cross-section including the desorption probability is obtained. Feasible mechanisms behind the observed energy and thickness dependences for anion and cation yields are proposed. These results highlight the need for further investigations to better understand the underlying processes of electron induced dissociation in condensed matter.

Evaluated electron scattering cross section dataset for gaseous benzene in the energy range 0.1-1000 eV

In this study, a complete and self-consistent cross section dataset for electron transport simulations through gaseous benzene in the energy range 0.1-1000 eV has been critically compiled. Its reliability has been evaluated through a joint experimental and computational procedure. To accomplish this, the compiled dataset has been used as input for event-by-event Monte Carlo simulations of the magnetically confined electron transport through gaseous benzene, and the simulated transmitted intensity has been compared with the experimental one for different incident energies and benzene gas pressures.

Prospective cohort study of Torque Teno Virus (TTV) viral load kinetics and the association with graft rejection in renal transplant patients

INTRODUCTION

Graft survival is mainly determined by rejections and infectious complications in transplant recipients. Torque Teno Virus (TTV), a nonpathogenic and ubiquitous single-stranded DNA virus, has been proposed as a biomarker of the immune status in transplant patients. This study aimed to determine the correlation between a Home-Brew TTV PCR and R-GENE®PCR; the TTV viral load kinetics in renal transplant recipients and the association with graft rejection.

MATERIALS AND METHODS

Prospective cohort study on 107 adult renal transplant recipients. TTV viral load was determined in 746 plasma samples collected before and after renal transplantation by a Home-Brew PCR and a commercial PCR (R-GENE®PCR). Associations of TTV viral load with graft rejections were analyzed.

RESULTS

Agreement of both PCR assays was 93.2% and Pearson correlation coefficient was r: 0.902 (95%CI: 0.8881-0.9149, p < 0.0001). TTV viral load kinetics showed an initial gradual increase reaching a peak at 3 months. This highest value was followed by a slight decrease, reaching a plateau significantly higher than the initial baseline at 6 months (p < 0.0001). Between (181-270) days post-transplantation, TTV median viral load in patients with graft rejection was significantly lower, 3.59 Log₁₀ copies/mL (by Home-Brew PCR) and 3.10 Log₁₀ copies/mL (by R-GENE®PCR) compared to patients without graft rejection (6.14 and 5.96 Log₁₀ copies/mL, respectively).

CONCLUSIONS

Significantly lower TTV viral load was observed in patients with renal rejection occurring at a median of 243 days post-transplantation. Given the dynamic behavior of TTV viral load post-transplantation, cut-off values for risk stratification to predict rejection might be determined in relation to the post-transplant period.

Temperature-Dependent Potential for the Molecular Dynamics of the superionic conductor β-PbF2

Molecular dynamic (MD) calculations were performed to investigate the thermodynamic and structural properties of lead fluoride (PbF₂) by using a proposed inter-ionic temperature-dependent potential. This potential allows calculating with high precision the linear thermal expansivity and the lattice parameter as a temperature function. In addition, the potential can be represented as a sum of two contributions, a temperature-independent potential added to another temperature-dependent potential, considered last as a correction justified by the one-dimensional Newtonian quantum equation. Two fitting regions were considered, the first region from 300 to 700 K and the other one from 700 to 900 K. These regions arise naturally due to the smooth and continuous transition that PbF₂ undergoes until it reaches the superionic state and, allows us to model with high precision the anomaly in the dependence of the lattice parameter with the temperature of this material, a feature that until now under the molecular dynamic method has not been studied. These results are all in good agreement with the experimental measurements.

Anionic states of C6Cl6 probed in electron transfer experiments

This is the first comprehensive investigation on the anionic species formed during collisions of fast neutral potassium (K) atoms with neutral hexachlorobenzene (C₆Cl₆) molecules in the laboratory frame range from 10 up to 100 eV. In such ion-pair formation experiments we also report a novel K⁺ energy loss spectrum obtained in the forward scattering giving evidence of the most accessible electronic states. The vertical electron affinity of (-3.76 ± 0.20) eV has been obtained and assigned to a purely repulsive transition from the C₆Cl₆ ground state to a state of the temporary negative ion yielding Cl^- formation. These experimental findings are also supported by state-of-the art theoretical calculations on the electronic structure of C₆Cl₆ in the presence of a potassium atom and are used for analysing the lowest unoccupied molecular orbitals participating in the collision process. From the time-of-flight mass spectra recorded in the wide collision energy range, more than 80% of the total anion yield is due to the undissociated parent anion C₆Cl₆^-, C₆Cl₅^- and Cl^- formation. Other fragment anions such as C₆Cl₄^-, C₃Cl₂^-, C₂Cl^- and Cl₂^- that undergo complex internal reactions with the temporary negative ion formed after electron transfer account for less than 20% of the total yield. The joint experimental and theoretical methodologies employed in these electron transfer studies provide the most comprehensive and unique assignments of the hexachlorobenzene anionic species and the role of C₆Cl₆ electronic states in collision induced dissociation to date.

Characterization of the proton pulsed beam at CMAM

In this paper, the technicalities performed to obtain a pulsed beam at the CMAM facility will be explained. The pulsed beam has been characterized with an 8 MeV proton beam, using an existing equipment at CMAM: two pairs of electrostatic plates (RASTER) that deflect the beam, commonly used for homogeneous irradiation of large areas. A pulsed beam is used in many areas such as nuclear physics, material science and, in particular, for proton-therapy medical studies. Rectangular and pyramidal functions have been used to generate different pulses and characterize the response of the RASTER. The results point out that the pulses obtained are suitable for preclinical proton-therapy studies in the FLASH regime, which consists on fractionating the dose in time with short and intense pulses. The set-up for the characterization has been a function generator and a Si-PM outside the chamber.

An improved set of electron-THFA cross sections refined through a neural network-based analysis of swarm data

We review experimental and theoretical cross sections for electron transport in α-tetrahydrofurfuryl alcohol (THFA) and, in doing so, propose a plausible complete set. To assess the accuracy and self-consistency of our proposed set, we use the pulsed-Townsend technique to measure drift velocities, longitudinal diffusion coefficients, and effective Townsend first ionization coefficients for electron swarms in admixtures of THFA in argon, across a range of density-reduced electric fields from 1 to 450 Td. These measurements are then compared to simulated values derived from our proposed set using a multi-term solution of Boltzmann's equation. We observe discrepancies between the simulation and experiment, which we attempt to address by employing a neural network model that is trained to solve the inverse swarm problem of unfolding the cross sections underpinning our experimental swarm measurements. What results from our neural network-based analysis is a refined set of electron-THFA cross sections, which we confirm is of higher consistency with our swarm measurements than that which we initially proposed. We also use our database to calculate electron transport coefficients in pure THFA across a range of reduced electric fields from 0.001 to 10 000 Td.

Selective bond breaking of halothane induced by electron transfer in potassium collisions

We present novel experimental results of negative ion formation of halothane (C₂HBrClF₃) upon electron transfer from hyperthermal neutral potassium atoms (K°) in the collision energy range of 8-1000 eV. The experiments were performed in a crossed molecular beam setup allowing a comprehensive analysis of the time-of-flight (TOF) mass negative ions fragmentation pattern and a detailed knowledge of the collision dynamics in the energy range investigated. Such TOF mass spectra data show that the only negative ions formed are Br^-, Cl^- and F^-, with a strong energy dependence in the low-energy collision region, with the bromine anion being the most abundant and sole fragment at the lowest collision energy probed. In addition, potassium cation (K⁺) energy loss spectra in the forward scattering direction were obtained in a hemispherical energy analyser at different K° impact energies. In order to support our experimental findings, ab initio quantum chemical calculations have been performed to help interpret the role of the electronic structure of halothane. Potential energy curves were obtained along the C-X (X = Br, Cl) coordinate to lend support to the dissociation processes yielding anion formation.

Cytotoxicity in Vero cells and cytokines analyses in Balb/c mice as safety assessments of the probiotic mixture Saccharomyces cerevisiae RC016 and Lactobacillus rhamnosus RC007 for use as a feed additive

The objective was to carry out cytotoxicity assays in Vero cells and cytokines analyses in Balb/c mice as safety assessments to evaluate the probiotic mixture (M) Saccharomyces cerevisiae RC016 (Sc) and Lactobacillus rhamnosus RC007 (Lr) for use as feed additive. Vero cells (10⁴ cells per well) were exposed to Sc (2·08 × 10⁷ , 2·08 × 10⁶ ; 2·08 × 10⁵ cells per ml), Lr (8·33 × 10⁷ ; 8·33 × 10⁶ ; 8·33 × 10⁵ cells per ml) and their M (1 : 1). Sc concentrations did not affect the Vero cells viability; in contrast, they were lower when exposed to Lr (P ˂ 0·0001). Vero cells showed increasing viability with M decreasing concentrations (91% viability with M2). Control BALB/c mice received only phosphate buffer saline and the others received the M. The IL-10, IL-6 and TNFα concentrations from intestinal fluid were analysed and no significant differences were observed among treatments. The same occurred with the ratio between IL-10/TNF-α. Beneficial effects of probiotics are associated with the regulation of the excessive inflammatory response; it is desirable they can modulate the cytokines production only under pathological conditions. Here, M administration to healthy mice did not induce negative side effects and expands the knowledge about beneficial effects of using probiotic microorganisms in mixture for feed additives development.

Combined Experimental and Theoretical Studies on Electron Transfer in Potassium Collisions with CCl4

Negative ion formation in electron transfer experiments from fast neutral potassium (K) atom collisions with neutral tetrachloromethane (CCl₄) molecules has been investigated in the laboratory frame range of 8-1000 eV. Comprehensive calculations on the electronic structure were performed for CCl₄ in the presence of a potassium atom and used to help analyze the lowest unoccupied molecular orbitals participating in the collision process. Additionally, K⁺ energy loss produced in the forward direction has served to further our knowledge on the electronic state spectroscopy of CCl₄. A vertical electron affinity of -0.79 ± 0.20 eV has been obtained and assigned to a purely repulsive transition from CCl₄ ground state to the ²T₂ state of the temporary negative ion yielding Cl^- formation. Other features in the energy loss spectrum were observed for the first time and related to Cl₂^-, CCl₂^-, and CCl₃^- formation. Special attention is also given to the unresolved feature corresponding to a positive electron affinity of 0.24 ± 0.2 eV, assigned to a vibrationally hot transition from CCl₄ ground state into the triply degenerate ²T₂ excited state of the negative ion. The combined time-of-flight mass spectrometry together with K⁺ energy loss data represents the most comprehensive assignment of the tetrachloromethane anion yields and the role of CCl₄ electronic states in collision induced dissociation to date.

Electron scattering cross sections from nitrobenzene in the energy range 0.4-1000 eV: the role of dipole interactions in measurements and calculations

Absolute total electron scattering cross sections (TCS) for nitrobenzene molecules with impact energies from 0.4 to 1000 eV have been measured by means of two different electron-transmission experimental arrangements. For the lower energies (0.4-250 eV) a magnetically confined electron beam system has been used, while for energies above 100 eV a linear beam transmission technique with high angular resolution allowed accurate measurements up to 1000 eV impact energy. In both cases random uncertainties were maintained below 5-8%. Systematic errors arising from the angular and energy resolution limits of each apparatus are analysed in detail and quantified with the help of our theoretical calculations. Differential elastic and integral elastic, excitation and ionisation as well as momentum transfer cross sections have been calculated, for the whole energy range considered here, by using an independent atom model in combination with the screening corrected additivity rule method including interference effects (IAM-SCARI). Due to the significant permanent dipole moment of nitrobenzene, additional differential and integral rotational excitation cross sections have been calculated in the framework of the Born approximation. If we ignore the rotational excitations, our calculated total cross section agrees well with our experimental results for impact energies above 15 eV. Additionally, they overlap at 10 eV with the low energy Schwinger Multichannel method with Pseudo Potentials (SMCPP) calculation available in the literature (L. S. Maioli and M. H. F. Bettega, J. Chem. Phys., 2017, 147, 164305). We find a broad feature in the experimental TCS at around 1.0 eV, which has been related to the formation of the NO2- anion and assigned to the π*(b1) resonance, according to previous mass spectra available in the literature. Other local maxima in the TCSs are found at 4.0 ± 0.2 and 5.0 ± 0.2 eV and are assigned to core excited resonances leading to the formation of the NO2- and O2- anions, respectively. Finally, for energies below 10 eV, differences found between the present measurements, the SMCPP calculation and our previous data for non-polar benzene have revealed the importance of accurately calculating the rotational excitation contribution to the TCS before comparing theoretical and experimental data. This comparison suggests that our dipole-Born calculation for nitrobenzene overestimates the magnitude of the rotational excitation cross sections below 10 eV.

Revisiting the photoabsorption spectrum of NH3 in the 5.4-10.8 eV energy region

We present a comprehensive revisited experimental high-resolution vacuum ultraviolet (VUV) photoabsorption spectrum of ammonia, NH₃, covering for the first time the full 5.4-10.8 eV energy-range, with absolute cross sections determined. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method restricted to single and double excitation levels and used to help reanalyze the observed Rydberg structures in the photoabsorption spectrum. The VUV spectrum reveals several new features that are not previously reported in the literature, with particular reference to the vibrational progressions of the (D̃¹E^'←X̃¹A₁ ^'), the (F̃¹E^'←X̃¹A₁ ^'), and the (G̃¹A₂ ^″←X̃¹A₁ ^') absorption bands. In addition, new Rydberg members have been identified in nda₁ ^'←1a₂ ^″D̃^''1A₂ ^″←X̃¹A₁ ^', where n > 3 has not been reported before as well as in nde^″←1a₂ ^″F̃¹E^'←X̃¹A₁ ^' and in nsa₁ ^'←1a₂ ^″G̃¹A₂ ^″←X̃¹A₁ ^'. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of ammonia in the Earth's atmosphere (0-50 km).

Experimental and theoretical analysis for total electron scattering cross sections of benzene

Measurements of the total electron scattering cross sections (TCSs) from benzene, in the impact energy range of 1-1000 eV, are presented here by combining two different experimental systems. The first utilizes a magnetically confined electron transmission beam for the lower energies (1-300 eV), while the second utilizes a linear transmission beam apparatus for the higher energies (100-1000 eV). These cross sections have also been calculated by means of two different theoretical methods, the Schwinger Multichannel with Pseudo Potential (SMCPP) procedure, employing two different approaches to account for the polarization of the target for impact energies between 0.1 and 15 eV, and the Independent Atom Model with the Screening Corrected Additivity Rule including Interference effect (IAM-SCAR+I) paradigm to cover the 10-10 000 eV impact energy range. The present results are compared with available theoretical and experimental data, with the level of accord being good in some cases and less satisfactory in others, and some predicted resonances have been identified. In particular, we found a π^* shape resonance at 1.4 eV and another feature in the energy region 4.6-4.9 eV interpreted as a π^* resonance (²B_2g symmetry), which is a mixture of shape and a core excited resonance, as well as a Feshbach resonance at 5.87 eV associated with the 3s (a_1g) Rydberg state. A Born-type formula to extrapolate TCS values for energies above 10 000 eV is also given. This study provides a complete set of TCS data, with uncertainty limits within 10%, ready to be used for modeling electron transport applications.

Change Management in Healthcare Organizations: Soft Skills Training Strategies Through Blended Learning Environments

Teaching soft skills for change management in healthcare organizations is becoming increasingly necessary, even more, when implementing health information systems (HIS). There is little evidence that these skills can be learned through online teaching environments. This paper describes the experience of having taught soft skills to health informatics master's degree students, through blended learning environments.

Morphological and Optical Characterization of Gold Nanoparticles Decorated Porous Silicon

In this article, physical characteristics of porous silicon (PS) obtained by electro chemical etching using HAuCl4 in the electrolyte are described. The morphological and optical features of PS decorated with gold-nanoparticles (AuNPs) were analyzed in function of the chemical etching time. The insertion of AuNPs inside the PS were performed simultaneously with the formation of the porous silicon layer. Scanning electron microscopy (SEM) analysis showed the formation and incorporation of AuNPs with an average size of 20 nm in the PS structure, which has a pore size of 1.5 μm. Also, it was possible to observe the loss of Si in function of the etching time. Photoluminescence spectroscopy analysis shows a decreasing of the PL intensity, which can be related to the presence of oxygen in the samples. Raman spectroscopy was used to estimate the size of the Si nanocrystals in the PS structure, which suffers a reduction in size due to the presence of HAuCl4 in the electrolyte.

Electron scattering from 1-butanol at intermediate impact energies: Total cross sections

We report experimental measurements of the absolute total cross sections (TCSs) for electron scattering from 1-butanol at impact energies in the range 80-400 eV. Those measurements were conducted by considering the attenuation of a collimated electron beam, at a given energy, through a gas cell containing 1-butanol, at a given pressure, and through application of the Beer-Lambert law to derive the required TCS. We also report theoretical results using the Independent-Atom Model with Screening Corrected Additivity Rule and Interference approach. Those results include the TCS, the elastic integral cross section (ICS), the ionization total ICS, and the sum over all excitation process ICSs with agreement at the TCS level between our measured and calculated results being encouraging.

Selective Bond Excision in Nitroimidazoles by Electron Transfer Experiments

We have performed comprehensive charge-transfer experiments yielding negative ion formation in collisions of fast neutral potassium atoms with nitroimidazole and methylated derivative molecules. The anionic pattern reveals that in the unimolecular decomposition of the precursor parent anion, single and multiple bond cleavages are attained. Selective excision of hydrogen atoms from the N1 position in 4-nitroimidazole (4NI) is completely blocked upon methylation in 1-methyl-4-nitroimidazole (1m4NI) and 1-methyl-5-nitroimidazole (1m5NI). Additionally, only 4NI and 2-nitroimidazole (2NI) are efficient in selectively producing neutral ^•OH and NO^• radicals in contrast to 1m4NI and 1m5NI. These findings present a novel experimental evidence of selective chemical bond breaking by just tuning the proper collision energy in atom-molecule collision experiments. The present work contributes to the current need of pinpointing a class of charge-transfer collisions that exhibit selective reactivity of the kind demonstrated here, extending to tailored chemical control for different applications such as tumor radiation therapy through nitroimidazole-based radiosensitization.

Total cross section measurements for electron scattering from dichloromethane

Using our magnetically confined electron transmission apparatus, we report the results of total cross sections (TCSs) for electron scattering from dichloromethane (CH₂Cl₂). The energy range of this study is 1-300 eV. Wherever possible, the present data are compared to earlier measured TCSs of Wan et al. [J. Chem. Phys. 94, 1865 (1991)] and Karwasz et al. [Phys. Rev. A 59, 1341 (1999)] and to the corresponding theoretical independent atom model with screening corrected additivity rule and interference term (IAM-SCAR+I) results of Krupa et al. [Phys. Rev. A 97, 042702 (2018)] and a spherical complex optical potential formulation calculation of Naghma et al. [J. Electron Spectrosc. Relat. Phenom. 193, 48 (2014)]. Within their respective uncertainties, the present TCS and those of Karwasz et al. are found to be in very good agreement over their common energy range. However, agreement with the results of Wan et al. is quite poor. The importance of the experimentally inherent 'missing angle' effect (see later) on the measured TCS is investigated and found to be significant at the lower energies studied. Indeed, when this effect is accounted for, agreement between our measured TCSs and the corrected IAM-SCAR+I+rotations calculation results are, for energies above about 3 eV, in good accord (to better than 8%). Finally, we observe two σ ^* shape resonances, consistent with the earlier electron transmission spectroscopy results of Burrow et al. [J. Chem. Phys. 77, 2699 (1982)], at about 2.8 eV and 4.4 eV incident electron energy, in our measured TCS.

Total electron scattering cross sections from para-benzoquinone in the energy range 1-200 eV

Total electron scattering cross sections, from para-benzoquinone, for impact energies ranging between 1 to 200 eV, have been obtained by measuring the attenuation of a linear electron beam under magnetic confinement conditions. Random uncertainty limits on these values have been found to be within 5%. Systematic errors, due to the axial magnetic beam conditions in combination with the acceptance angle of the detector, have been evaluated by integrating our calculated independent atom model with the screening corrected additivity rule and interference term elastic differential cross sections over that detection acceptance angle. Our previous calculations and measurements on this molecule (Jones et al., J. Chem. Phys., 2018, 148, 124312 and J. Chem. Phys., 2018, 148, 204305), have been compiled and complemented with new elastic and inelastic scattering cross section calculations in order to obtain a comprehensive cross section data base, within the considered energy range, for modelling purposes. The self-consistency of the present data set has been evaluated by simulating the electron transport of 15 eV electrons in para-benzoquinone, and comparing those results with the observed transmitted intensity distribution.

Communication: Site-selective bond excision of adenine upon electron transfer

This work demonstrates that selective excision of hydrogen atoms at a particular site of the DNA base adenine can be achieved in collisions with electronegative atoms by controlling the impact energy. The result is based on analysing the time-of-flight mass spectra yields of potassium collisions with a series of labeled adenine derivatives. The production of dehydrogenated parent anions is consistent with neutral H loss either from selective breaking of C-H or N-H bonds. These unprecedented results open up a new methodology in charge transfer collisions that can initiate selective reactivity as a key process in chemical reactions that are dominant in different areas of science and technology.

Electron transfer driven decomposition of adenine and selected analogs as probed by experimental and theoretical methods

We report on a combined experimental and theoretical study of electron-transfer-induced decomposition of adenine (Ad) and a selection of analog molecules in collisions with potassium (K) atoms. Time-of-flight negative ion mass spectra have been obtained in a wide collision energy range (6-68 eV in the centre-of-mass frame), providing a comprehensive investigation of the fragmentation patterns of purine (Pu), adenine (Ad), 9-methyl adenine (9-mAd), 6-dimethyl adenine (6-dimAd), and 2-D adenine (2-DAd). Following our recent communication about selective hydrogen loss from the transient negative ions (TNIs) produced in these collisions [T. Cunha et al., J. Chem. Phys. 148, 021101 (2018)], this work focuses on the production of smaller fragment anions. In the low-energy part of the present range, several dissociation channels that are accessible in free electron attachment experiments are absent from the present mass spectra, notably NH₂ loss from adenine and 9-methyl adenine. This can be understood in terms of a relatively long transit time of the K⁺ cation in the vicinity of the TNI tending to enhance the likelihood of intramolecular electron transfer. In this case, the excess energy can be redistributed through the available degrees of freedom inhibiting fragmentation pathways. Ab initio theoretical calculations were performed for 9-methyl adenine (9-mAd) and adenine (Ad) in the presence of a potassium atom and provided a strong basis for the assignment of the lowest unoccupied molecular orbitals accessed in the collision process.

Magnetically confined electron beam system for high resolution electron transmission-beam experiments

A novel experimental setup has been implemented to provide accurate electron scattering cross sections from molecules at low and intermediate impact energies (1-300 eV) by measuring the attenuation of a magnetically confined linear electron beam from a molecular target. High-resolution electron energy is achieved through confinement in a magnetic gas trap where electrons are cooled by successive collisions with N₂. Additionally, we developed and present a method to correct systematic errors arising from energy and angular resolution limitations. The accuracy of the entire measurement procedure is validated by comparing the N₂ total scattering cross section in the considered energy range with benchmark values available in the literature.

A process to describe radiation damage at the molecular level. Application to the 125I seeds in water

The correlation between the absorbed energy and the induced biological damage still has unclear aspects, especially in the low energy and low dose rate irradiation regimes. From the knowledge of the molecular-induced effects (dissociations), it would be possible to better understand the side effects of radiation, such as induced cancers or damage to healthy tissue. With this in view, this paper presents results of a simulation of a ¹²⁵I-seed treatment with an event-by-event MC code (LEPTS) specifically designed to account for the low energy secondary particle interactions, such as electron attachment, vibro-rotational and neutral dissociation interactions. This calculation allowed us to analyze the potential radiation damage not only in connection with the energy deposition, but also in terms of induced molecular dissociations by taking into account ionizing and non-ionizing dissociative processes. We propose that this description of the molecular level damage be the basis for nanodosimetric evaluations.

Electron stimulated desorption from condensed pyrimidine and pyridazine

Low energy electron (LEE) interactions and the formation of transient negative ions play a dominant role in radiation-induced dissociation of condensed-phase biomolecules (e.g. in radiotherapy). Here we present data on the LEE-induced dissociation and desorption of the DNA/RNA-base and radiosensitizing agent analogues pyrimidine and pyridazine. Vapors of each molecule were condensed on either a Pt or Ar substrate to form a multilayer film or a submonolayer molecular target, respectively. These were irradiated with electrons of 0-80 eV and the desorbing anionic and cationic fragments analysed via time of flight mass spectrometry. The detected cations are the same species seen in gas-phase mass spectra, albeit of differing relative intensity. Anion yield functions exhibit strong maxima, indicating that transient negative ions contribute significantly, via dissociative electron attachment (DEA), to molecular dissociation below 20 eV. For both molecules, the <5 eV shape resonances, seen experimentally and predicted by theory, do not result in fragment desorption. The main anionic fragments are H^- and CN^- for both molecules, additionally the fragments C^-, CH^- C₂H^- and CHN^- desorb from pyrimidine and C^- and C₂H^- from pyridazine, with some resonances lying above the ionization limit. Pyrimidine shows higher anion desorption yields than pyridazine for all species except H^-. The anion signal also comprises dipolar dissociation (DD), investigated in both anionic and cationic yield functions. From analysis of anion and cation yields, fragmentation pathways are suggested. The direct ionization pathway provides information on the appearance energies for cations and their production processes in condensed phase.

Antibiotic resistance and population structure of cystic fibrosis Pseudomonas aeruginosa isolates from a Spanish multi-centre study

The first Spanish multi-centre study on the microbiology of cystic fibrosis (CF) was conducted from 2013 to 2014. The study involved 24 CF units from 17 hospitals, and recruited 341 patients. The aim of this study was to characterise Pseudomonas aeruginosa isolates, 79 of which were recovered from 75 (22%) patients. The study determined the population structure, antibiotic susceptibility profile and genetic background of the strains. Fifty-five percent of the isolates were multi-drug-resistant, and 16% were extensively-drug-resistant. Defective mutS and mutL genes were observed in mutator isolates (15.2%). Considerable genetic diversity was observed by pulsed-field gel electrophoresis (70 patterns) and multi-locus sequence typing (72 sequence types). International epidemic clones were not detected. Fifty-one new and 14 previously described array tube (AT) genotypes were detected by AT technology. This study found a genetically unrelated and highly diverse CF P. aeruginosa population in Spain, not represented by the epidemic clones widely distributed across Europe, with multiple combinations of virulence factors and high antimicrobial resistance rates (except for colistin).

Aflatoxins and Saccharomyces cerevisiae: yeast modulates the intestinal effect of aflatoxins, while aflatoxin B1 influences yeast ultrastructure

The gastrointestinal tract (GIT) is the main site where absorption of food components takes place and the first system coming into contact with mycotoxins of dietary origin. The aim of this work was to study the effect of probiotic Saccharomyces cerevisiae RC016 on intestinal villi of rats exposed to aflatoxins for 60 days. Moreover, the effect of in vitro aflatoxin B1 (AFB1) exposure on yeast cell ultrastructure was evaluated. Six treatments were applied (n=6) to inbred male Wistar rats: (1) uncontaminated feed control (F); (2) yeast control; (3) F + 40 μg/kg AFB1 + 20 μg/kg aflatoxin G1 (AFG1); (4) F + 100 μg/kg AFB1 + 50 μg/kg AFG1; (5) F + 40 μg/kg AFB1 + 20 μg/kg AFG1 + daily oral dose 108 viable S. cerevisiae cells; and (6) F + 100 μg/kg AFB1 + 50 μg/kg AFG1 + daily oral dose 108 viable S. cerevisiae cells. Morphometric measurements (villus length and width, crypt depth, quantification of goblet cells) were assessed using image analysis. S. cerevisiae RC016 cells were exposed to 20 μg/ml of AFB1 in intestinal solutions or in phosphate buffered saline and cells processed for transmission electron microscopy and high resolution light microscopy studies. Dietary exposure to the yeast did not induce significant differences in villus width but increased villus length and crypt depth. Aflatoxin-contaminated diets induced an increase in villus length, width and crypt depth and a significant decrease in the number of goblet cells which were improved by the addition of S. cerevisiae RC016. A significant increase in the yeast cell diameter was observed when RC016 was exposed to aflatoxins, suggesting this as an advantage since a larger cell would be able to adsorb mycotoxins more efficiently. The ability of this strain to act as probiotic and aflatoxin binder makes it a candidate for the formulation of new additives to improve animal performance.