Boron coordination change in barium borate melts and glasses and its contribution to configurational heat capacity, entropy, and fragility.

High-energy x-ray diffraction from molten and glassy BaB2O4 and BaB4O7 has been performed using aerodynamic levitation and laser heating over a wide range of temperatures. Remarkably, even in the presence of a heavy metal modifier dominating x-ray scattering, it was possible to extract accurate values for the tetrahedral, sp3, boron fraction, N4, which declines with increasing temperature, using bond valence-based mapping from the measured mean B-O bond lengths while accounting for vibrational thermal expansion. These are used within a boron-coordination-change model to extract enthalpies, ΔH, and entropies, ΔS, of isomerization between sp2 and sp3 boron. The results for BaB4O7, ΔH = 22(3) kJ mol-1 boron, ΔS = 19(2) J mol-1 boron K-1, agree quantitatively with those found previously for Na2B4O7. Analytical expressions for N4(J, T) and associated configurational heat capacity, CPconf(J, T), and entropy, Sconf(J, T), contributions are extended to cover a wide composition range 0 ≤ J = BaO/B2O3 ≤ 3 using a model for ΔH(J) and ΔS(J) derived empirically for lithium borates. Maxima in the CPconf(J, Tg) and fragility index contributions are thereby predicted for J ≲ 1, higher than the maximum observed and predicted in N4(J, Tg) at J ≃ 0.6. We discuss the utility of the boron-coordination-change isomerization model in the context of borate liquids containing other modifiers and the prospect of neutron diffraction to aid in empirical determinations of modifier-dependent effects, illustrated by new neutron diffraction data on Ba11B4O7 glass, its well-known α-polymorph, and lesser-known δ-phase.

Heterogeneous melting near the Thwaites Glacier grounding line.

Thwaites Glacier represents 15% of the ice discharge from the West Antarctic Ice Sheet and influences a wider catchment1-3. Because it is grounded below sea level4,5, Thwaites Glacier is thought to be susceptible to runaway retreat triggered at the grounding line (GL) at which the glacier reaches the ocean6,7. Recent ice-flow acceleration2,8 and retreat of the ice front8-10 and GL11,12 indicate that ice loss will continue. The relative impacts of mechanisms underlying recent retreat are however uncertain. Here we show sustained GL retreat from at least 2011 to 2020 and resolve mechanisms of ice-shelf melt at the submetre scale. Our conclusions are based on observations of the Thwaites Eastern Ice Shelf (TEIS) from an underwater vehicle, extending from the GL to 3 km oceanward and from the ice-ocean interface to the sea floor. These observations show a rough ice base above a sea floor sloping upward towards the GL and an ocean cavity in which the warmest water exceeds 2 °C above freezing. Data closest to the ice base show that enhanced melting occurs along sloped surfaces that initiate near the GL and evolve into steep-sided terraces. This pronounced melting along steep ice faces, including in crevasses, produces stratification that suppresses melt along flat interfaces. These data imply that slope-dependent melting sculpts the ice base and acts as an important response to ocean warming.

Photoionization from the Xe 4d orbitals of XeF2.

We present a comparison of the photoionization dynamics of the 4d shell of XeF2 from threshold to 250 eV to those of the prototypical 4d shell of atomic Xe. The new experimental data include spin-orbit and ligand-field-resolved partial cross sections, photoelectron angular distributions, branching fractions, and lifetime widths for the 4d-hole states. The spin-orbit branching fractions and angular distributions are remarkably similar to the corresponding distributions from atomic Xe across a broad energy interval that includes both the intense shape resonance in the f continuum and a Cooper minimum in the same channel. The angular distributions and branching fractions are also in reasonably good agreement with our first-principles theoretical calculations on XeF2. Data are also presented on the lifetime widths of the substate-resolved 4d-hole states of XeF2. While the trends in the widths are similar to those in the earlier experimental and theoretical work, the linewidths are considerably smaller than in the previous measurements, which may require some reinterpretation of the decay mechanism. Finally, we present new data and an analysis of the Auger electron spectra for ionization above the 4d thresholds and resonant Auger spectra for several pre-edge features.

Valence shell photoelectron angular distributions and vibrationally resolved spectra of imidazole: A combined experimental-theoretical study.

Linearly polarized synchrotron radiation has been used to record polarization dependent valence shell photoelectron spectra of imidazole in the photon energy range 21-100 eV. These have allowed the photoelectron angular distributions, as characterized by the anisotropy parameter ß, and the electronic state intensity branching ratios to be determined. Complementing these experimental data, theoretical photoionization partial cross sections and ß-parameters have been calculated for the outer valence shell orbitals. The assignment of the structure appearing in the experimental photoelectron spectra has been guided by vertical ionization energies and spectral intensities calculated by various theoretical methods that incorporate electron correlation and orbital relaxation. Strong orbital relaxation effects have been found for the 15a', nitrogen lone-pair orbital. The calculations also predict that configuration mixing leads to the formation of several low-lying satellite states. The vibrational structure associated with ionization out of a particular orbital has been simulated within the Franck-Condon model using harmonic vibrational modes. The adiabatic approximation appears to be valid for the X 2A″ state, with the ß-parameter for this state being independent of the level of vibrational excitation. However, for all the other outer valence ionic states, a disparity occurs between the observed and the simulated vibrational structure, and the measured ß-parameters are at variance with the behavior expected at the level of the Franck-Condon approximation. These inconsistencies suggest that the excited electronic states may be interacting vibronically such that the nuclear dynamics occur over coupled potential energy surfaces.

Photoionization of C4H5 Isomers.

Single-photon, photoelectron-photoion coincidence spectroscopy is used to record the mass-selected ion spectra and slow photoelectron spectra of C4H5 radicals produced by the abstraction of hydrogen atoms from three C4H6 precursors by fluorine atoms generated by a microwave discharge. Three different C4H5 isomers are identified, with the relative abundances depending on the nature of the precursor (1-butyne, 1,2-butadiene, and 1,3-butadiene). The results are compared with our previous work using 2-butyne as a precursor [Hrodmarsson, H. R. J. Phys. Chem. A 2019, 123, 1521-1528]. The slow photoelectron spectra provide new information on the three radical isomers that is in good agreement with previous experimental and theoretical results [Lang, M. J. Phys. Chem. A 2015, 119, 3995-4000; Hansen, N. J. Phys. Chem. A 2006, 110, 3670-3678]. The energy scans of the C4H5 photoionization signal are recorded with substantially better resolution and signal-to-noise ratio than those in earlier work, allowing the observation of autoionizing resonances based on excited states of the C4H5 cation. Photoelectron images recorded at several energies are also reported, providing insight into the decay processes of these excited states. Finally, in contrast to the earlier work using 2-butyne as a precursor, where H-atom abstraction was the only observed process, F- and H-atom additions to the present precursors are also observed through the detection of C4H6F, C4H5F, and C4H7.

Universal energy scaling law for optimally excited nonlinear oscillators.

We compute the optimal temporal profile for an external driving force F(t) that can maximize the energy absorption of any driven nonlinear oscillator. The technique is based on constraining the maximum amplitude of the force field such that optimal control theory can provide quasianalytical solutions. We illustrate this computational technique for the undamped Duffing oscillator as well as for a driven quantum mechanical two-level system. We find that under optimal force conditions the asymptotic time-dependence of the maximum amplitude growth is given by a power law X(t)∼t^{2/α}, where the (possibly noninteger) exponent is determined by the highest degree of the oscillator's nonlinearity α. As a universal result, this predicts that the maximal energy absorption of any nonlinear oscillator grows (under an optimized force field) quadratically in time. We also find for the two-level system that-even under optimized excitation conditions-the maximally achievable inversion does not monotonically increase with the force amplitude. It is characterized by an interesting sequence of n-cycle thresholds as well as a self-termination of the growth.

An experimental and theoretical study of the C 1s ionization satellites in CH3I.

The C 1s ionization spectrum of CH3I has been studied both experimentally and theoretically. Synchrotron radiation has been employed to record polarization dependent photoelectron spectra at a photon energy of 614 eV. These spectra encompass the main-line due to the C 1s single-hole state and the peaks associated with the shake-up satellites. Vertical ionization energies and relative photoelectron intensities have been computed using the fourth-order algebraic-diagrammatic construction approximation scheme for the one-particle Green's function and the 6-311++G** basis set. The theoretical spectrum derived from these calculations agrees qualitatively with the experimental results, thereby allowing the principal spectral features to be assigned. According to our calculations, two 2A1 shake-up states of the C 1s-1 σCI → σCI * type with singlet and triplet intermediate coupling of the electron spins (S' = 0, 1) play an important role in the spectrum and contribute significantly to the overall intensity. Both of these states are expected to have dissociative diabatic potential energy surfaces with respect to the C-I separation. Whereas the upper of these states perturbs the manifold of Rydberg states, the lower state forms a band which is characterized by a strongly increased width. Our results indicate that the lowest shake-up peak with significant spectral intensity is due to the pair (S' = 0, 1) of 2E (C 1s-1 I 5p → σCI *) states. We predict that these 2E states acquire photoelectron intensity due to spin-orbit interaction. Such interactions play an important role here due to the involvement of the I 5p orbitals.

Valence-Shell Photoionization of C4H5: The 2-Butyn-1-yl Radical.

We present new high-resolution data on the photoionization of the 2-butyn-1-yl radical (CH3C≡C-•CH2) formed by H atom abstraction from 2-butyne by F atoms. The spectra were recorded from 7.7 to 11 eV by using double-imaging, photoelectron-photoion coincidence spectroscopy, which allows the unambiguous correlation of photoelectron data and the mass of the species. The photoionization spectrum shows significant resonant autoionizing structure converging to excited states of the C4H5+ cation, similar to what is observed in the closely related propargyl radical (HC≡C-•CH2). The threshold photoelectron spectrum, obtained with a resolution of 17 meV, is also reported. This spectrum is consistent with previous measurements of the first photoionization band but has been extended to higher energy to allow the observation of bands corresponding to excited electronic states of the ion. A refined value of the adiabatic ionization energy is extracted: IE(C4H5) = 7.93 ± 0.01 eV. A determination of the absolute photoionization cross section of the 2-butyn-1-yl radical at 9.7 eV is also reported: σion(C4H5) = 6.1 ± 1.8 Mb.

Antibiotics and open fractures of the lower extremity: less is more.

PURPOSE: Infectious complications in open lower extremity fractures contribute to significant morbidity. Historically, orthopedic guidelines have recommended Grade III fractures receive a first generation cephalosporin and an aminoglycoside. Despite these guidelines, few studies have evaluated the utility of adding an aminoglycoside in this patient population. At our trauma center, we have a unique trauma service where half of our surgeons treat Grade III open fractures with a cephalosporin alone and half use a cephalosporin + aminoglycoside. We hypothesized that our outcomes were the same between the two groups. METHODS: We identified all Grade III fractures of the lower extremity admitted to our urban Level I Trauma Center over the 5-year study period. Charts were retrospectively reviewed to identify demographic information, injury severity score (ISS), fracture location, grade of fracture, type of antibiotic administered, incidence of acute kidney injury (AKI), surgical site infection (SSI), hardware removal, hospital length of stay (HLOS), and disposition. Patients were classified into two groups: those treated with a cephalosporin alone (CEPH) or cephalosporin + an aminoglycoside (CEPH + AG). RESULTS: A total of 126 grade III fractures of the lower extremity were admitted our Trauma Center during the 5-year study period. There were 65 (52%) patients in the CEPH group and 61 (48%) in the CEPH + AG group. Demographics, ISS, fracture location, grade of fracture, rate of SSI, need for hardware removal, and disposition were not different between the two groups. In contrast, patients in the CEPH group had a 4% incidence of AKI, while the incidence was 10% of patients in the CEPH + AG group (p < 0.05). CONCLUSION: The addition of an AG to antibiotic prophylaxis in open lower extremity fractures was associated with a significant increase in AKI with no change in the incidence of wound infection or hardware removal. Cephalosporins alone may be sufficient for prophylaxis in Grade III open fractures of the lower extremity. A large-scale prospective randomized trial is needed to confirm these findings and inform clinical practice.

Use of coping strategies in multiple sclerosis: Association with demographic and disease-related characteristics✰.

BACKGROUND: Coping positively and negatively influences psychosocial and other outcomes in multiple sclerosis (MS), but there is conflicting evidence about the use of different coping strategies and their associations with demographic and disease characteristics. Our aims were to examine which coping strategies are used by a large sample of people with MS, then to identify any associations between demographic and disease related factors with use of individual coping strategies. METHODS: Participants in the Trajectories of Outcomes in Neurological Conditions (TONiC) study completed the Coping Orientations to Problems Experienced (COPE60) questionnaire. Relationships between demographic and clinical characteristics and coping strategies were examined by multiple ordinal logistic regression to assess the effect of each potential predictor after adjustment for other possible covariates. RESULTS: From 722 patients, the most commonly used strategy was Acceptance, followed by Active Coping, Planning and Positive Reinterpretation and Growth. All but two strategies showed significant associations with demographic and clinical characteristics. The most marked effects were found for Restraint, with people in employment 2.1 times as likely to utilise this strategy compared to those unemployed, and Seeking of Emotional Social Support and Focus on and Venting of Emotions, which were utilised twice as much by women compared to men. Behavioural and Mental Disengagement were highly associated with greater disability and not being in employment. CONCLUSION: Clinicians should be aware of several disease and demographic characteristics that are associated with use of potentially maladaptive coping strategies.

Factors Affecting the Response of Pomegranate Fruit to Alternaria alternata, the Causal Agent of Heart Rot.

Heart rot, caused by Alternaria alternata, is a major pomegranate disease that impacts production worldwide; most fruits in orchards are colonized by A. alternata but, nevertheless, symptoms are apparent on only a small proportion of the colonized fruits. During the years of our previous research it was noticed that within individual orchards, the incidence of pomegranate fruits exhibiting heart rot symptoms was related to the visual appearance of the trees: trees that appeared visually frail bore more diseased fruits than robust trees. Furthermore, it was noticed that the disease responses of different pomegranate accessions and possibly of different variants of the same cultivar varied markedly. The specific objectives of the present study were: (i) to characterize the relationship between the visual appearance of pomegranate plants or individual stems and the incidence of heart rot and their vulnerability to heart rot; and (ii) to elucidate factors affecting the response of pomegranate fruit to A. alternata. Analysis of heart rot incidence in four orchards in 2014 revealed large differences in heart rot incidence among trees growing side by side in the same orchard; these differences were related to the visual appearance of the pomegranate trees. There were significant differences among germination rates of A. alternata spores in juice prepared from asymptomatic fruits originating from these trees, and comparable differences were found among the acidity levels (pH) of the juices. These differences may reflect differences among the physiological responses of pomegranate trees to heart rot. Fruits collected from the pomegranate collection located in Newe Ya'ar, which comprised 95 accessions in 2015 and 110 accessions in 2016, were also examined. There were differences among the acidity levels (pH) of the juices produced from these fruits and among the germination rates of A. alternata spores in the juices. These differences may reflect variances among the genetic responses of pomegranate accessions to heart rot. Results of studying the relationship between the acidity levels of pomegranate juice and the germination rates of A. alternata spores supported the hypothesis that, apart from pH, a compound(s) present in the juice regulates the germination of A. alternata spores in the juice.

Photoionization dynamics of cis-dichloroethene from investigation of vibrationally resolved photoelectron spectra and angular distributions.

The influence of vibronic coupling on the outer valence ionic states of cis-dichloroethene has been investigated by recording photoelectron spectra over the excitation range 19-90 eV using plane polarized synchrotron radiation, for two polarization orientations. The photoelectron anisotropy parameters and electronic state branching ratios derived from these spectra have been compared to theoretical predictions obtained with the continuum multiple scattering approach. This comparison shows that the photoionization dynamics of the Ã2B2, B̃2A1, C̃2A2, and D̃2B1 states, all of which are formed through the ejection of an electron from a nominally chlorine lone-pair orbital, exhibit distinct evidence of the Cooper minimum associated with the halogen atom. While retaining a high degree of atomic character, these orbital ionizations nevertheless display clear distinctions. Simulations, assuming the validity of the Born-Oppenheimer and the Franck-Condon approximations, of the X̃2B1, Ã2B2, and D̃2B1 state photoelectron bands have allowed some of the vibrational structure observed in the experimental spectra to be assigned. The simulations provide a very satisfactory interpretation for the X̃2B1 state band but appear less successful for the Ã2B2 and D̃2B1 states, with irregularities appearing in both. The B̃2A1 and C̃2A2 state photoelectron bands exhibit very diffuse and erratic profiles that cannot be reproduced at this level. Photoelectron anisotropy parameters, ß, have been evaluated as a function of binding energy across the studied photon energy range. There is a clear step change in the ß values of the Ã2B2 band at the onset of the perturbed peak intensities, with ß evidently adopting the value of the B̃2A1 band ß. The D̃2B1 band ß values also display an unexpected vibrational level dependence, contradicting Franck-Condon expectations. These various behaviors are inferred to be a consequence of vibronic coupling in this system.

An experimental and theoretical study of the photoelectron spectra of cis-dichloroethene: Valence shell vertical ionization and vibronic coupling in the low-lying cationic states.

The valence shell photoelectron spectrum of cis-dichloroethene has been studied both experimentally and theoretically. Photoelectron spectra have been recorded with horizontally and vertically plane polarized synchrotron radiation, thereby allowing the anisotropy parameters, characterizing the angular distributions, to be determined. The third-order algebraic-diagrammatic construction approximation scheme for the one-particle Green's function has been employed to compute the complete valence shell ionization spectrum. In addition, the vertical ionization energies have been calculated using the outer valence Green's function (OVGF) method and the equation-of-motion coupled-cluster, with single and double substitutions for calculating ionization potentials (EOM-IP-CCSD) model. The theoretical results have enabled assignments to be proposed for most of the structure observed in the experimental spectra, including the inner-valence regions dominated by satellite states. The linear vibronic coupling model has been employed to study the vibrational structure of the lowest photoelectron bands, using parameters obtained from ab initio calculations. The ground state optimized geometries and vibrational frequencies have been computed at the level of the second-order Møller-Plesset perturbation theory, and the dependence of the ionization energies on the nuclear configuration has been evaluated using the OVGF method. While the adiabatic approximation holds for the X̃2B1 state photoelectron band, the Ã2B2, B̃2A1, and C̃2A2 states interact vibronically and form a complex photoelectron band system with four distinct maxima. The D̃2B1 and Ẽ2B2 states also interact vibronically with each other. The potential energy surface of the D̃2B1 state is predicted to have a double-minimum shape with respect to the out-of-plane a2 deformations of the molecular structure. The single photoelectron band resulting from this interaction is characterized by a highly irregular structure, reflecting the non-adiabatic nuclear dynamics occurring on the two coupled potential energy surfaces forming a conical intersection close to the minimum of the Ẽ2B2 state.

Photoelectron angular distributions from rotationally resolved autoionizing states of N2.

The single-photon, photoelectron-photoion coincidence spectrum of N2 has been recorded at high (∼1.5 cm-1) resolution in the region between the N2+ X Σg2+, v+ = 0 and 1 ionization thresholds by using a double-imaging spectrometer and intense vacuum-ultraviolet light from the Synchrotron SOLEIL. This approach provides the relative photoionization cross section, the photoelectron energy distribution, and the photoelectron angular distribution as a function of photon energy. The region of interest contains autoionizing valence states, vibrationally autoionizing Rydberg states converging to vibrationally excited levels of the N2+ X Σg2+ ground state, and electronically autoionizing states converging to the N2+A2Π and B 2Σu+ states. The wavelength resolution is sufficient to resolve rotational structure in the autoionizing states, but the electron energy resolution is insufficient to resolve rotational structure in the photoion spectrum. A simplified approach based on multichannel quantum defect theory is used to predict the photoelectron angular distribution parameters, ß, and the results are in reasonably good agreement with experiment.

An experimental and theoretical study of the valence shell photoelectron spectra of 2-chloropyridine and 3-chloropyridine.

The valence shell photoelectron spectra of 2-chloropyridine and 3-chloropyridine have been studied both experimentally and theoretically. Synchrotron radiation has been employed to record angle resolved photoelectron spectra in the photon energy range 20-100 eV, and these have enabled anisotropy parameters and branching ratios to be derived. The experimental results have been compared with theoretical predictions obtained using the continuum multiple scattering Xα approach. This comparison shows that the anisotropy parameter associated with the nominally chlorine lone-pair orbital lying in the molecular plane is strongly affected by the atomic Cooper minimum. In contrast, the photoionization dynamics of the second lone-pair orbital, orientated perpendicular to the molecular plane, seem relatively unaffected by this atomic phenomenon. The outer valence ionization has been studied theoretically using the third-order algebraic-diagrammatic construction (ADC(3)) approximation scheme for the one-particle Green's function, the outer valence Green's function method, and the equation-of-motion (EOM) coupled cluster (CC) theory at the level of the EOM-IP-CCSD and EOM-EE-CC3 models. The convergence of the results to the complete basis set limit has been investigated. The ADC(3) method has been employed to compute the complete valence shell ionization spectra of 2-chloropyridine and 3-chloropyridine. The relaxation mechanism for ionization of the nitrogen σ-type lone-pair orbital (σN LP) has been found to be different to that for the corresponding chlorine lone-pair (σCl LP). For the σN LP orbital, π-π* excitations play the main role in the screening of the lone-pair hole. In contrast, excitations localized at the chlorine site involving the chlorine πCl LP lone-pair and the Cl 4p Rydberg orbital are the most important for the σCl LP orbital. The calculated photoelectron spectra have allowed assignments to be proposed for most of the structure observed in the experimental spectra. The theoretical work also highlights the formation of satellite states, due to the breakdown of the single particle model of ionization, in the inner valence region.

Homeless shelter context and tuberculosis illness experiences during a large outbreak in Atlanta, Georgia.

Setting: Persons experiencing homelessness (PEH) represent a population at high risk for tuberculosis (TB). While quantitative studies have characterized some important features of this key group, less has been captured directly from PEH about how they experience TB illness itself and the prevention and control measures implemented in response to an outbreak. This qualitative study aimed to explore PEH's TB disease experiences in the context of a large TB outbreak involving homeless shelters in Atlanta, Georgia, USA. Design: This was a qualitative cross-sectional study involving in-depth interviews with 10 PEH with active TB disease. Key themes were identified through coded data analysis. Results: The central theme to emerge was that stressful social environments of homeless shelters shape illness experiences and health care seeking behaviors, and limit the influence of shelter-based prevention and control measures implemented in response to a TB outbreak. Despite availability, shelter-based latent tuberculous infection (LTBI) testing and education services were minimally engaged. Furthermore, hardships inherent to homelessness were interrelated with disease normalization and symptom minimization. Conclusions: Homeless shelter-related stress may have important implications for the prevention and control of TB outbreaks in this setting. This stress may hinder case finding; a model of supplemental TB education and testing for LTBI at proximal community venues is necessary.

Contexte: Les personnes sans domicile fixe (SDF) représentent une population à haut risque de tuberculose (TB). Si les études quantitatives ont caractérisé certains traits importants de ce groupe clé, moins d'informations ont été obtenues directement des SDF sur la façon dont ces personnes expérimentent la TB maladie elle-même et les mesures de prévention et de lutte mises en œuvre en réponse à l'épidémie. Cette étude qualitative visait à explorer l'expérience des SDF en matière de TB maladie dans le contexte d'une vaste flambée épidémique impliquant des centres d'hébergement de SDF à Atlanta, Georgie.Schéma : Une étude qualitative transversale impliquant des entretiens approfondis avec dix SDF atteints de TB active. Les thèmes clés ont été identifiés grâce à une analyse des données codées.Résultats : Le thème central qui a émergé est que l'environnement social stressant des centres d'hébergement façonne les expériences de la maladie et les comportements de recherche de soins et limite l'influence des mesures de prévention et de lutte basées dans ces centres et mises en œuvre en réponse à une flambée de TB. En dépit de leur disponibilité dans les centres d'hébergement, le dépistage de l'infection tuberculeuse latent (ITL) et les services d'éducation ont été très peu engagés. Plus encore, les difficultés inhérentes à l'absence de domicile fixe ont été indissociables de la normalisation de la maladie et de la minimisation des symptômes.Conclusions: Le stress lié à l'hébergement dans un refuge pour SDF peut avoir des implications majeures dans la prévention et la lutte contre les flambées de TB dans ce contexte. Ce stress peut entraver la découverte des cas et soutenir un modèle d'éducation supplémentaire à la TB et une recherche de l'ITL dans les lieux communautaires proches.

Marco de referencia: Las personas que carecen de vivienda constituyen una población con alto riesgo de contraer la tuberculosis (TB). Los estudios cuantitativos han caracterizado algunos aspectos importantes de este grupo poblacional, pero poco se ha captado directamente de su forma de vivenciar la enfermedad tuberculosa y las medidas de prevención y de control que se instauran en respuesta a un brote epidémico. El presente estudio cualitativo tuvo por objeto analizar las vivencias de la enfermedad tuberculosa por parte de las personas que carecen de vivienda, en el contexto de un amplio brote epidémico de TB que ocurrió en los albergues para personas sin techo en Atlanta, Georgia.Método: Fue este un estudio cualitativo transversal, que comportó entrevistas exhaustivas a 10 personas sin vivienda, con enfermedad tuberculosa activa. Se reconocieron los principales temas mediante un análisis temático con datos codificados.Resultados: El principal tema que surgió en el análisis fue que los entornos sociales estresantes de los albergues determinan las experiencias de la enfermedad y el comportamiento de búsqueda de atención y limitan la repercusión de las medidas de prevención y control que se aplican en los albergues en respuesta a un brote epidémico de TB. Pese a su disponibilidad, las pruebas diagnósticas de la infección tuberculosa latente y los servicios educativos prestados en los albergues se utilizaban poco. Además, las adversidades inherentes a la falta de vivienda se correlacionaron con una normalización de la enfermedad y la minimización de los síntomas.Conclusión: El estrés generado en los albergues destinados a las personas sin vivienda puede tener repercusiones importantes en la prevención y el control de los brotes de TB en estos entornos. Este estrés puede obstaculizar la búsqueda de casos y su demostración respalda la aplicación de un modelo de educación complementaria en materia de TB y de pruebas diagnósticas de la infección latente en los centros comunitarios próximos.

Ionization of pyridine: Interplay of orbital relaxation and electron correlation.

The valence shell ionization spectrum of pyridine was studied using the third-order algebraic-diagrammatic construction approximation scheme for the one-particle Green's function and the outer-valence Green's function method. The results were used to interpret angle resolved photoelectron spectra recorded with synchrotron radiation in the photon energy range of 17-120 eV. The lowest four states of the pyridine radical cation, namely, 2A2(1a2-1), 2A1(7a1-1), 2B1(2b1-1), and 2B2(5b2-1), were studied in detail using various high-level electronic structure calculation methods. The vertical ionization energies were established using the equation-of-motion coupled-cluster approach with single, double, and triple excitations (EOM-IP-CCSDT) and the complete basis set extrapolation technique. Further interpretation of the electronic structure results was accomplished using Dyson orbitals, electron density difference plots, and a second-order perturbation theory treatment for the relaxation energy. Strong orbital relaxation and electron correlation effects were shown to accompany ionization of the 7a1 orbital, which formally represents the nonbonding σ-type nitrogen lone-pair (nσ) orbital. The theoretical work establishes the important roles of the π-system (π-π* excitations) in the screening of the nσ-hole and of the relaxation of the molecular orbitals in the formation of the 7a1(nσ)-1 state. Equilibrium geometric parameters were computed using the MP2 (second-order Møller-Plesset perturbation theory) and CCSD methods, and the harmonic vibrational frequencies were obtained at the MP2 level of theory for the lowest three cation states. The results were used to estimate the adiabatic 0-0 ionization energies, which were then compared to the available experimental and theoretical data. Photoelectron anisotropy parameters and photoionization partial cross sections, derived from the experimental spectra, were compared to predictions obtained with the continuum multiple scattering approach.

Reducing the risk of mouth-to-mouth transmission of pathogens via re-usable, machine-read parking tickets: an observational cohort study.

The car parks at the study hospital are accessed using re-usable, machine-read tickets. In the initial phase of this study, 598 staff members were observed entering the car park, and 21.6% of them put their parking ticket in their mouth. Ultraviolet dye was used to demonstrate card-to-card cross-contamination. Swabs of the ticket machine yielded commensal bacteria: coagulase-negative staphylococci and a Bacillus sp. After placing a poster on the ticket-reading machine highlighting the potential risk of infection, a further 1366 observations demonstrated a significant and persistent decline in the proportion of staff who put their ticket in their mouth (P<0.001).

Genetic evidence for role of integration of fast and slow neurotransmission in schizophrenia.

The most recent genome-wide association studies (GWAS) of schizophrenia (SCZ) identified hundreds of risk variants potentially implicated in the disease. Further, novel statistical methodology designed for polygenic architecture revealed more potential risk variants. This can provide a link between individual genetic factors and the mechanistic underpinnings of SCZ. Intriguingly, a large number of genes coding for ionotropic and metabotropic receptors for various neurotransmitters-glutamate, γ-aminobutyric acid (GABA), dopamine, serotonin, acetylcholine and opioids-and numerous ion channels were associated with SCZ. Here, we review these findings from the standpoint of classical neurobiological knowledge of neuronal synaptic transmission and regulation of electrical excitability. We show that a substantial proportion of the identified genes are involved in intracellular cascades known to integrate 'slow' (G-protein-coupled receptors) and 'fast' (ionotropic receptors) neurotransmission converging on the protein DARPP-32. Inspection of the Human Brain Transcriptome Project database confirms that that these genes are indeed expressed in the brain, with the expression profile following specific developmental trajectories, underscoring their relevance to brain organization and function. These findings extend the existing pathophysiology hypothesis by suggesting a unifying role of dysregulation in neuronal excitability and synaptic integration in SCZ. This emergent model supports the concept of SCZ as an 'associative' disorder-a breakdown in the communication across different slow and fast neurotransmitter systems through intracellular signaling pathways-and may unify a number of currently competing hypotheses of SCZ pathophysiology.