Radiative relaxation in isolated large carbon clusters: Vibrational emission versus recurrent fluorescence.

Recurrent fluorescence (RF) from isolated carbon clusters containing between 24 and 60 atoms is theoretically investigated as a function of internal energy, cluster size, and structural features. The vibrational relaxation kinetics and the associated IR emission spectra are determined by means of a Monte Carlo approach with vibrational density of states computed in the harmonic approximation. RF is generally found to be highly competitive with vibrational emission. The behaviors predicted for clusters of various sizes and archetypal structures indicate that the IR emission spectra are strongly influenced by RF, an energy gap law being obtained for the evolution of the RF rate constant depending on the electronic excitation state. The present results are relevant to the photophysics of the interstellar medium and could contribute to elucidating the carriers of the extended red emission bands and the continuum emission lying below the aromatic infrared bands believed to originate from mixed aromatic-aliphatic compounds.

Low-energy vibrational spectra of flexible diphenyl molecules: biphenyl, diphenylmethane, bibenzyl and 2-, 3- and 4-phenyltoluene.

Gas phase absorption far-infrared (FIR) spectra of six flexible hydrocarbon molecules containing two phenyl groups -biphenyl, diphenylmethane, bibenzyl and 2-, 3-, 4-phenyltoluene- are reported for the first time, allowing an accurate determination of most of their active low-frequency vibrational modes. DFT calculations have been carried out at the harmonic and perturbative anharmonic levels to predict the vibrational spectra of these molecules and unambiguously assign observed vibrational modes.

Atomistic modeling of vibrational action spectra in polyatomic molecules: nuclear quantum effects.

The response of a polyatomic molecule to an infrared (IR) laser pulse of varying frequency has been simulated by classical molecular dynamics simulations and by quantum methods based on the path-integral framework (PIMD), as well as quantum thermal baths (QTBs). The outcome of the trajectories was subsequently processed to predict a dissociation spectrum, from the precalculated rate constant. Naphthalene described by a tight-binding potential energy surface was chosen as a testing ground for the present problem, possibly emitting an hydrogen atom after a 12 ps long pulse. At low field intensities, the heating efficiency of the pulse is found to vary similarly as the IR absorption spectrum for all methods considered, reflecting the validity of linear response in this regime. At fields that are sufficiently high to induce statistical dissociation over mass spectrometry timescales, marked differences appear with the spectral features exhibiting additional broadenings and redshift, especially for quantum mechanical descriptions of nuclear motion. Those excessive broadenings are mostly caused by anharmonicities but also convey the inherent approximations of the semiclassical QTB method and point at limitations of the PIMD simulations when used in such strong out-of-equilibrium conditions.

Validation of the French version of the Hospital Survey on Patient Safety Culture questionnaire.

OBJECTIVE: To assess the psychometric properties of the French version of the Hospital Survey on Patient Safety Culture questionnaire (HSOPSC) and study the hierarchical structure of the measured dimensions. DESIGN: Cross-sectional survey of the safety culture. SETTING: 18 acute care units of seven hospitals in South-western France. PARTICIPANTS: Full- and part-time healthcare providers who worked in the units. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Item responses measured with 5-point agreement or frequency scales. Data analyses A principal component analysis was used to identify the emerging components. Two structural equation modeling methods [LInear Structural RELations (LISREL) and Partial Least Square (PLS)] were used to verify the model and to study the relative importance of the dimensions. Internal consistency of the retained dimensions was studied. A test-retest was performed to assess reproducibility of the items. RESULTS: Overall response rate was 77% (n = 401). A structure in 40 items grouped in 10 dimensions was proposed. The LISREL approach showed acceptable data fit of the proposed structure. The PLS approach indicated that three dimensions had the most impact on the safety culture: 'Supervisor/manager expectations & actions promoting safety' 'Organizational learning-continuous improvement' and 'Overall perceptions of safety'. Internal consistency was above 0.70 for six dimensions. Reproducibility was considered good for four items. CONCLUSIONS: The French HSOPSC questionnaire showed acceptable psychometric properties. Classification of the dimensions should guide future development of safety culture improving action plans.

Healthcare worker protection against mpox contamination: position paper of the French Society for Hospital Hygiene.

In the context of the recent re-emergence of mpox worldwide, the French Society for Hospital Hygiene (SF2H) performed a literature review of the transmission paths and proposed specific recommendations for healthcare workers (HCWs) caring for patients with suspected or confirmed MPXV. In developed countries, the risk of contamination among HCWs in healthcare facilities seemed to be very low, limited to contamination through needle stick injuries. Two additional contamination cases were reported and not fully explained. Beyond healthcare settings, the analysis of the literature highlighted (i) a main contamination route during sexual intercourse, mainly among men who have sex with men, and (ii) a very low secondary attack rate in other contexts, such as schools or jails. Numerous studies have reported molecular or virus identification on surfaces or in the air surrounding patients, without any association with the low secondary case incidence; moreover, the minimum infectious dose through air or mucosal exposure is still unknown. Owing to the lack of evidence of MPXV respiratory transmission in the healthcare setting, the SF2H recommends the implementation of standard and contact precautions combined with medical/surgical mask use. Owing to the lack of evidence of transcutaneous contamination, the SF2H recommends the use of gloves only if contact with cutaneous lesions or mucous membranes occurs. Regarding the risk of contamination from the environment in healthcare facilities, additional studies must be conducted to investigate this.

Amplification of anharmonicities in multiphoton vibrational action spectra.

The influence of one or several infrared laser pulses on the stability of bare and argon-tagged sodium chloride clusters is investigated theoretically by a combination of computational methods involving explicit molecular dynamics and properly calibrated unimolecular rate theories. The fragmentation spectra obtained by varying the laser frequency in the far-IR range is compared to the linear absorption spectrum resulting from the dipole moment autocorrelation function. Under appropriate laser field parameters, the action spectra are found to resemble the absorption spectra quite accurately in terms of positions, line widths, and even relative intensities. However, the action spectra exhibit residual and systematic redshifts of a few percent, which are partly due to the finite spectral bandwidth but are amplified by the progressive heating by the laser. A quantitative analysis suggests that these anharmonicity effects should generally arise upon multiple photon absorption.

Temperature effects on the rovibrational spectra of pyrene-based PAHs.

Absorption infrared spectra have been computed for a variety of polycyclic aromatic hydrocarbon molecules of the pyrene family, taking into account anharmonicity and temperature effects, rovibrational quantization, and couplings. The energy levels are described by a second-order perturbative expansion of the rovibrational Hamiltonian in the vibrational and rotational quantum numbers, as relevant for a symmetric-top molecule, with ingredients obtained from quantum chemistry calculations. Multicanonical Monte Carlo simulations are carried out to compute bidimensional IR intensity histograms as a function of total energy and vibrational frequency, which then provide the absorption spectrum at arbitrary temperatures via a Laplace transformation. The main spectral features analyzed for neutral, anionic, and cationic pyrene indicate a strong dependence on temperature, in agreement with existing laboratory experiments, and a significant contribution of rotational degrees of freedom to the overall broadenings. The spectral shifts and broadenings reveal some sensitivity of anharmonicities to the charge and protonation states and, in the case of protonated pyrene and pyrenyl cation, on possible isomers and between aromatic and aliphatic C-H bands. Implications of the present work to the general issue of interstellar emission features are discussed.

Finite-temperature IR spectroscopy of polyatomic molecules: a theoretical assessment of scaling factors.

With a recently developed simulation method (Basire, M.; et al. J. Phys. Chem. A 2009, 113, 6947), the infrared vibrational spectra of several polyatomic molecules are calculated over a broad range of temperature, taking into account quantum, anharmonic, and couplings effects. Anharmonic force fields, generated from static first-principle calculations, are sampled in the microcanonical ensemble to provide energy-resolved absorption intensities and their finite temperature analogues after Laplace transformation. Effective anharmonic frequencies are characterized as a continuous function of temperature for vinyl fluoride, the N-acetyl-Phe-NH(2) peptide, and protonated naphthalene. These frequencies generally deviate increasingly from the harmonic value with increasing temperature, although the overestimation due to the harmonic approximation is particularly salient for high-frequency modes. Anharmonicities may also be sufficient to alter structural assignment of experimental spectra with respect to empirically scaled harmonic bands. These results emphasize some possible limitations and inaccuracies inherent to using such static scaling factors for correcting harmonic IR spectra.

Finite-temperature infrared spectroscopy of polycyclic aromatic hydrocarbon molecules. II. Principal mode analysis and self-consistent phonons.

Following previous work [F. Calvo et al. J. Chem. Phys. 132, 124308 (2010)], infrared spectra of several polycyclic aromatic hydrocarbon molecules are simulated with classical and quantum molecular dynamics trajectories. The interactions are modeled using a tight-binding potential energy surface and quantum delocalization is accounted for using the partially adiabatic centroid and ring-polymer molecular dynamics frameworks, both built upon the path-integral representation. The spectra obtained directly by Fourier transformation of the dipole moment autocorrelation function are here compared with several quasiharmonic approximations that provide additional information about the vibrational modes. A principal mode analysis (PMA) is carried out from the covariance matrix of atomic displacements in classical and quantum trajectories. The method systematically overestimates the line shifts due to anharmonicities, except in the power spectra of atomic displacements, and is not robust in predicting IR intensities for such large molecules. Alternatively, effective normal modes have also been determined by adapting the self-consistent phonon (SCP) theory of condensed matter physics to the present tight-binding model, in both classical and quantum mechanical descriptions. The SCP approximation turns out as semiquantitative in estimating the redshift of tight stretching modes, and performs better for classical systems. More problematic, it predicts that many low- or medium-frequency modes should be blueshifted, in contradiction with the molecular dynamics results. The sets of anharmonic normal modes extracted from the PMA and SCP approaches reveal important mixings within the tightest C-H and C-C stretching modes, which are also manifested on the corresponding power spectra.

Finite temperature infrared spectroscopy of polycyclic aromatic hydrocarbon molecules: path-integral molecular dynamics.

The vibrational spectra of the naphthalene, pyrene, and coronene molecules have been computed in the 0-3500 cm(-1) infrared range using classical and quantum molecular dynamics simulations based on a dedicated tight-binding potential energy surface. The ring-polymer molecular dynamics (RPMD) and partially adiabatic centroid molecular dynamics (CMD) methods have been employed to account for quantum nuclear effects. The contributions of quantum delocalization to the line shift and broadening are significant in the entire spectral range and of comparable magnitude as pure thermal effects. While the two methods generally produce similar results, the CMD method may converge slower at low temperature with increasing Trotter discretization number. However, and contrary to the CMD method, the RPMD approach suffers from serious resonance problems at high frequencies and low temperatures.

Phase space theory of evaporation in neon clusters: the role of quantum effects.

Unimolecular evaporation of neon clusters containing between 14 and 148 atoms is theoretically investigated in the framework of phase space theory. Quantum effects are incorporated in the vibrational densities of states, which include both zero-point and anharmonic contributions, and in the possible tunneling through the centrifugal barrier. The evaporation rates, kinetic energy released, and product angular momentum are calculated as a function of excess energy or temperature in the parent cluster and compared to the classical results. Quantum fluctuations are found to generally increase both the kinetic energy released and the angular momentum of the product, but the effects on the rate constants depend nontrivially on the excess energy. These results are interpreted as due to the very few vibrational states available in the product cluster when described quantum mechanically. Because delocalization also leads to much narrower thermal energy distributions, the variations of evaporation observables as a function of canonical temperature appear much less marked than in the microcanonical ensemble. While quantum effects tend to smooth the caloric curve in the product cluster, the melting phase change clearly keeps a signature on these observables. The microcanonical temperature extracted from fitting the kinetic energy released distribution using an improved Arrhenius form further suggests a backbending in the quantum Ne(13) cluster that is absent in the classical system. Finally, in contrast to delocalization effects, quantum tunneling through the centrifugal barrier does not play any appreciable role on the evaporation kinetics of these rather heavy clusters.

Temperature and anharmonic effects on the infrared absorption spectrum from a quantum statistical approach: application to naphthalene.

A method is developed to calculate the finite-temperature infrared absorption spectrum of polyatomic molecules with energy levels described by a second-order Dunham expansion. The anharmonic couplings are fully incorporated in the calculation of the quantum density of states, achieved using a Wang-Landau Monte Carlo procedure, as well as in the determination of transition energies. Additional multicanonical simulations provide the microcanonical absorption intensity as a function of both the absorption wavelength and the internal energy of the molecule. The finite-temperature spectrum is finally obtained by Laplace transformation of this microcanonical histogram. The present scheme is applied to the infrared spectrum of naphthalene, for which we quantify the shifting, broadening, and third-order effects as a continuous function of temperature. The influence of anharmonicity and couplings is manifested on the nontrivial variations of these features with increasing temperature.

Quantum densities of states of fluxional polyatomic systems from a superposition approximation.

The superposition method is used to calculate quantum densities of states of polyatomic systems with multiple isomeric structures. For each isomer, anharmonicities are included rigorously using a Dunham expansion of the vibrational energy levels and short exchange Monte Carlo simulations are used to compute the individual quantum densities of states. The method is applied to the computation of thermodynamical properties of the Ar(13) and Ne(13) clusters. The canonical heat capacities are found in very satisfactory agreement with the predictions of quantum or semiclassical sampling methods.

Quantum anharmonic densities of states using the Wang-Landau method.

The Wang-Landau sampling method is adapted to the calculation of quantum densities of states for fully coupled anharmonic systems. The accuracy of the method is illustrated against exact counting for two molecules with separable oscillators, namely, the Zundel complex H(5)O(2) (+) and the Na(11) cluster. Application to the fully coupled naphthalene molecule (C(10)H(8)) reveals significant deviations in the finite temperature thermodynamical properties that are not captured by simple perturbation theory. There are no limitations in the size of the molecules that can be treated with this method.

Atomistic modeling of the infrared response of fullerenes under hydrostatic pressure.

The anharmonic infrared spectrum of individual C60 and C70 fullerenes under hydrostatic pressure was theoretically computed by means of atomistic simulations. Using a tight-binding model for the fullerenes and a simple particle-based pressure-transmitting fluid, the structural and vibrational properties were determined at room temperature and up to 20 GPa. All properties generally exhibit relative variations that are linear with increasing pressure, but whose magnitude can be comparable to pure thermal effects. The bond length contraction usually agrees with existing results, and for C70 our approach manages to reproduce the occasionally negative pressure coefficient found for some low-frequency modes in experiments.

Fighting the good fight: the fallout of fake news in infection prevention and why context matters.

Although misinformation has always existed, the scope and speed at which fake news can reach even the most remote corners of the globe is a modern phenomenon. In the field of infection prevention and control (IPC), we like to believe that our dedication to the field and the process of conducting science protects us from the ravages of 'bad buzz' and fake news. This misconception leads medical professionals to underestimate the negative effects of misinformation on public health. This paper focuses on the nexus of what is happening between the field of IPC and the public. Its aim is to examine how information gets distorted and amplified between the medical community and the public, and outline some of the issues that deserve further attention. It looks at a number of case studies which show that even one badly conducted study can have a severe negative impact on public health, and that a well-conducted study can be distorted to make people believe something fallacious. In the current system of publishing and the proliferation of online journals that publish without peer review, 'bad buzz' and fake news can quickly do a good deal of damage.

Relationship between rates of antimicrobial consumption and the incidence of antimicrobial resistance in Staphylococcus aureus and Pseudomonas aeruginosa isolates from 47 French hospitals.

OBJECTIVE: To investigate relationships between rates of antimicrobial consumption and the incidence of antimicrobial resistance in Staphylococcus aureus and Pseudomonas aeruginosa isolates from hospitals. METHODS: We conducted an observational study that used retrospective data from 2002 and linear regression to model relationships. Hospitals were asked to collect data on consecutive S. aureus and P. aeruginosa isolates, consumption rates for antibiotics (ie, anti-infectives for systemic use as defined by Anatomical Therapeutic Chemical class J01), and hospital characteristics, including infection control policies. Rates of methicillin resistance in S. aureus and rates of ceftazidime and ciprofloxacin resistance in P. aeruginosa were expressed as the percentage of isolates that were nonsusceptible (ie, either resistant or intermediately susceptible) and as the incidence of nonsuceptible isolates (ie, the number of nonsuceptible isolates recovered per 1,000 patient-days). The rate of antimicrobial consumption was expressed as the number of defined daily doses per 1,000 patient-days. SETTING: Data were obtained from 47 French hospitals, and a total of 12,188 S. aureus isolates and 6,370 P. aeruginosa isolates were tested. RESULTS: In the multivariate analysis, fewer antimicrobials showed a significant association between the consumption rate and the percentage of isolates that were resistant than an association between the consumption rate and the incidence of resistance. The overall rate of antibiotic consumption, not including the antibiotics used to treat methicillin-resistant S. aureus infection, explained 13% of the variance between hospitals in the incidence of methicillin resistance among S. aureus isolates. The incidence of methicillin resistance in S. aureus isolates increased with the use of ciprofloxacin and levofloxacin and with the percentage of the hospital's beds located in intensive care units (adjusted multivariate coefficient of determination [aR(2)], 0.30). For P. aeruginosa, the incidence of ceftazidime resistance was greater in hospitals with higher consumption rates for ceftazidime, levofloxacin, and gentamicin (aR(2), 0.37). The incidence of ciprofloxacin resistance increased with the use of fluoroquinolones and with the percentage of a hospital's beds located in intensive care ( aR(2), 0.28). CONCLUSIONS: A statistically significant relationship existed between the rate of fluoroquinolone use and the rate of antimicrobial resistance among S. aureus and P. aeruginosa isolates. The incidence of resistant isolates showed a stronger association with the rate of antimicrobial use than did the percentage of isolates with resistance.

Surveillance of occupational blood and body fluid exposures among French healthcare workers in 2004.

OBJECTIVE: To estimate the incidence rate of reported occupational blood and body fluid exposures among French healthcare workers (HCWs). DESIGN: Prospective national follow-up of HCWs from January 1 to December 31, 2004. SETTING: University hospitals, hospitals, clinics, local medical centers, and specialized psychiatric centers were included in the study on a voluntary basis. PARTICIPANTS: At participating medical centers, every reported blood and body fluid exposure was documented by the occupational practitioner in charge of the exposed HCW by use of an anonymous, standardized questionnaire. RESULTS: A total of 375 medical centers (15% of French medical centers, accounting for 29% of hospital beds) reported 13,041 blood and body fluid exposures; of these, 9,396 (72.0%) were needlestick injuries. Blood and body fluid exposures were avoidable in 39.1% of cases (5,091 of 13,020), and 52.2% of percutaneous injuries (4,986 of 9,552) were avoidable (5.9% due to needle recapping). Of 10,656 percutaneous injuries, 22.6% occurred during an injection, 17.9% during blood sampling, and 16.6% during surgery. Of 2,065 splashes, 22.6% occurred during nursing activities, 19.1% during surgery, 14.1% during placement or removal of an intravenous line, and 12.0% during manipulation of a tracheotomy tube. The incidence rates of exposures were 8.9 per 100 hospital beds (95% confidence interval [CI], 8.7-9.0 exposures), 2.2 per 100 full-time-equivalent physicians (95% CI, 2.4-2.6 exposures), and 7.0 per 100 full-time-equivalent nurses (95% CI, 6.8-7.2 exposures). Human immunodeficiency virus serological status was unknown for 2,789 (21.4%) of 13,041 patients who were the source of the blood and body fluid exposures. CONCLUSION: National surveillance networks for blood and body fluid exposures help to better document their characteristics and risk factors and can enhance prevention at participating medical centers.

Determinants of glycopeptides consumption in hospitals.

The aim of this study was to describe consumption of glycopeptides and to study factors associated with their use in 47 French hospitals. Consumption of glycopeptides for systemic use (defined daily doses per 1,000 patient-days: DDD/1,000 PD and per 100 admissions), number of methicillin-resistant Staphylococcus aureus (MRSA) (percentage and incidence per 1,000 patient-days), and number of venous central lines and hospital characteristics (size, length of stay, number of beds: total and for each hospital inpatient areas and antibiotic policies) were recorded from January, 2002, through December, 2002. Multiple linear regression was performed to check for hospital characteristics. The median rate of total consumption of glycopeptides was 4.11(range 0.21-27.22) DDD per 1,000 PD with higher consumption in large public hospitals and in intensive care areas (median 46.51; range 7.19-134) than in surgery areas (median 4.5; range 0.17-24.76). The consumption of glycopeptides correlated with MRSA incidence, but not with the proportion of MRSA. In the multivariate analysis, the incidence of MRSA and the number of beds in surgery areas were independent predictors of total glycopeptides use in the hospital, expressed in DDD per 1,000 PD (R2 adjusted, 0.39). The incidence of MRSA, the number of venous central lines, and the number of beds in the medicine areas were significant determinants associated with higher consumption of glycopeptides expressed in DDD per 100 admissions (R2 adjusted, 0.73). To reduce glycopeptides use in hospitals, the first effort required is that hospitals focus increased attention on the prevention of cross transmission for MRSA between patients but also on the use of the venous central line. Furthermore, hospitals have to compare their data with others to identify overuse of glycopeptides and to plan control interventions.