The dangers of reused personal protective equipment: healthcare workers and workstation contamination.

BACKGROUND: Personal protective equipment (PPE) is essential to protect healthcare workers (HCWs). The practice of reusing PPE poses high levels of risk for accidental contamination by HCWs. Scarce medical literature compares practical means or methods for safe reuse of PPE while actively caring for patients. METHODS: In this study, observations were made of 28 experienced clinical participants performing five donning and doffing encounters while performing simulated full evaluations of patients with coronavirus disease 2019. Participants' N95 respirators were coated with a fluorescent dye to evaluate any accidental fomite transfer that occurred during PPE donning and doffing. Participants were evaluated using blacklight after each doffing encounter to evaluate new contamination sites, and were assessed for the cumulative surface area that occurred due to PPE doffing. Additionally, participants' workstations were evaluated for contamination. RESULTS: All participants experienced some contamination on their upper extremities, neck and face. The highest cumulative area of fomite transfer risk was associated with the hook and paper bag storage methods, and the least contamination occurred with the tabletop storage method. Storing a reused N95 respirator on a tabletop was found to be a safer alternative than the current recommendation of the US Centers for Disease Control and Prevention to use a paper bag for storage. All participants donning and doffing PPE were contaminated. CONCLUSION: PPE reusage practices pose an unacceptably high level of risk of accidental cross-infection contamination to healthcare workers. The current design of PPE requires complete redesign with improved engineering and usability to protect healthcare workers.

Solvation effects on self-association and segregation processes in tert-butanol-aprotic solvent binary mixtures.

The present study reveals that the fully miscible binary mixtures consisting of tert-butanol with aprotic solvents form well-defined ordered supermolecular structures, which have been characterized on different length scales. Three different types of microstructures have been determined. They are separated by distinct crossovers that appear as a function of the dilution rate, going from "correlated clusters" to "diluted clusters" and "diluted monomer" microstructures. These observations have been made possible by the combination of Raman vibration spectroscopy, (1)H NMR, and neutron diffraction that probe, respectively, the cluster formation (self-association) and the intercluster correlations (cluster segregation). The solvation effects on both the cluster formation and the intercluster correlations have been assessed by tuning the alcohol-solvent interaction, i.e., changing the chemical nature of the diluting solvent from a purely inert alkane to a weakly interacting aromatic system.

Synaptic changes in Alzheimer's disease and its models.

Alzheimer's disease (AD) is a highly prevalent neurodegenerative disorder characterized by a progressive loss of cognition and the presence of two hallmark lesions, senile plaques (SP) and neurofibrillary tangles (NFT), which result from the accumulation and deposition of the ß-amyloid peptide (Aß) and the aggregation of hyperphosphorylated tau protein, respectively. Initially, it was thought that Aß fibrils, which make up SP, were the root cause of the massive neurodegeneration usual found in AD brains. Over time, the longstanding emphasis on fibrillar Aß deposits and neuronal death slowly gave way to a new paradigm involving soluble oligomeric forms of Aß, which play a prominent role in triggering the cognitive deficits by specifically targeting synapses and disrupting synaptic signaling pathways. While this paradigm is widely accepted today in the AD field, the molecular details have not been fully elucidated. In this review, we address some of the important evidence, which has led to the Aß oligomer-centric hypothesis as well as some of the key findings concerning the effects of Aß oligomers on synapses at a morphological and functional level. Understanding how Aß oligomers target synapses provides an important framework for ongoing AD research, which can lead to the development of successful therapeutic strategies designed to alter or perhaps reverse the course of the disease.

Structural, optical, and dielectric properties of Bi(1.5-x)Zn(0.92-y)Nb(1.5)O(6.92-δ) thin films grown by PLD on R-plane sapphire and LaAlO3 substrates.

Bi(1.5-x)Zn(0.92-y)Nb(1.5)O(6.92-δ) thin films have the potential to be implemented in microwave devices. This work aims to establish the effect of the substrate and of the grain size on the optical and dielectric properties. Bi(1.5-x)Zn(0.92-y)Nb(1.5)O(6.92-δ) thin films were grown at 700 °C via pulsed-laser deposition on R-plane sapphire and (100)(pc) LaAlO(3) substrates at various oxygen pressures (30, 50, and 70 Pa). The structure, morphology, dielectric and optical properties were investigated. Despite bismuth and zinc deficiencies, with respect to the Bi(1.5)Zn(0.92)Nb(1.5)O(6.92) stoichiometry, the films show the expected cubic pyrochlore structure with a (100) epitaxial-like growth. Different morphologies and related optical and dielectric properties were achieved, depending on the substrate and the oxygen pressure. In contrast to thin films grown on (100)(pc) LaAlO(3), the films deposited on R-plane sapphire are characterized by a graded refractive index along the layer thickness. The refractive index (n) at 630 nm and the relative permittivity (ε(r)) measured at 10 GHz increase with the grain size: on sapphire, n varies from 2.29 to 2.39 and ε(r) varies from 85 to 135, when the grain size increases from 37 nm to 77 nm. On the basis of this trend, visible ellipsometry can be used to probe the characteristics in the microwave range quickly, nondestructively, and at a low cost.

Mixed acoustic phonons and phase modes in an aperiodic composite crystal.

Aperiodic crystals which are long range ordered materials present original dynamics features due to the lack of translational symmetry formally implying the nonvalidity of the Brillouin zone concept. This Letter reports the observation by neutron scattering of an overdamped acousticlike mode at a Bragg peak position in a n-alkane-urea inclusion crystal. This result implies the existence of a gap in the dispersion branch. The gap and anomalous damping of these collective modes are discussed in terms of specific dynamics and interaction in aperiodic materials.

The non-Gaussian dynamics of glycerol.

We have combined incoherent quasielastic neutron scattering experiments and atomistic molecular simulations to investigate the microscopic dynamics of glycerol moving away from the hydrodynamic limit. We relate changes in the momentum transfer (Q) dependence of the relaxation time to distinct changes of the single-particle dynamics. Going from small to large values of Q, a first crossover at about 0.5 Å(-1) is related to the coupling of the translational diffusion dynamics to the non-Debye structural relaxation, while the second crossover at a Q-value near the main diffraction peak is associated with the Gaussian to non-Gaussian crossover of the short-time molecular dynamics, related to the decaging processes. We offer an unprecedented extension of previous studies on polymeric systems towards the case of the typical low-molecular-weight glass-forming system glycerol.

Phase separation of a binary liquid in anodic aluminium oxide templates: a structural study by small angle neutron scattering.

The radial nanostructure of the binary liquid triethylamine/water confined in 60 nm diameter independent cylindrical pores of anodic aluminium oxide membranes is studied by small angle neutron scattering. It is shown that composition inhomogeneities are present in the confined mixtures well below the bulk critical point. An analysis of the neutron scattering form factor reveals the existence of an adsorbed water layer of a few nanometers at the liquid/alumina interface, coexisting with a TEA-rich phase in the core.

Toward a Coarse Graining/All Atoms Force Field (CG/AA) from a Multiscale Optimization Method: An Application to the MCM-41 Mesoporous Silicates.

Many interesting physical phenomena occur on length and time scales that are not accessible by atomistic molecular simulations. By introducing a coarse graining of the degrees of freedom, coarse-grained (CG) models allow ther study of larger scale systems for longer times. Coarse-grained force fields have been mostly derived for large molecules, including polymeric materials and proteins. By contrast, there exist no satisfactory CG potentials for mesostructured porous solid materials in the literature. This issue has become critical among a growing number of studies on confinement effects on fluid properties, which require both long time and large scale simulations and the conservation of a sufficient level of atomistic description to account for interfacial phenomena. In this paper, we present a general multiscale procedure to derive a hybrid coarse grained/all atoms force field CG/AA model for mesoporous systems. The method is applied to mesostructured MCM-41 molecular sieves, while the parameters of the mesoscopic interaction potentials are obtained and validated from the computation of the adsorption isotherm of methanol by grand canonical molecular dynamic simulation.

Molecular dynamics simulation of nanoconfined glycerol.

We present results from molecular dynamics simulations of liquid glycerol confined in a realistic model of a cylindrical silica nanopore. The influence of the hydrophilic surface and the geometrical confinement on the structure, hydrogen-bond lifetime, rotational and translational molecular dynamics are analysed. Layering and dynamical heterogeneities are induced by confinement. These features share some similarities with previous observations in simpler van der Waals glass-forming liquids. In addition, the specificity of glycerol as an associated liquid shows up in confinement by the formation of interfacial hydrogen bonds and some modifications of the in-pore hydrogen-bonding network. Confinement is also seen to influence the relaxation dynamics and the glassy behaviour in the supercooled state. These phenomena revealed by molecular simulation are important inputs for a better understanding of the many recent experimental results on confined glycerol and more generally for the possible manipulation of associated liquids in porous or fluidic devices.

Molecular dynamics of glycerol and glycerol-trehalose bioprotectant solutions nanoconfined in porous silicon.

Glycerol and trehalose-glycerol binary solutions are glass-forming liquids with remarkable bioprotectant properties. Incoherent quasielastic neutron scattering is used to reveal the different effects of nanoconfinement and addition of trehalose on the molecular dynamics in the normal liquid and supercooled liquid phases, on a nanosecond time scale. Confinement has been realized in straight channels of diameter D=8 nm formed by porous silicon. It leads to a faster and more inhomogeneous relaxation dynamics deep in the liquid phase. This confinement effect remains at lower temperature where it affects the glassy dynamics. The glass transitions of the confined systems are shifted to low temperature with respect to the bulk ones. Adding trehalose tends to slow down the overall glassy dynamics and increases the nonexponential character of the structural relaxation. Unprecedented results are obtained for the binary bioprotectant solution, which exhibits an extremely non-Debye relaxation dynamics as a result of the combination of the effects of confinement and mixing of two constituents.

Rich polymorphism of a rod-like liquid crystal (8CB) confined in two types of unidirectional nanopores.

We present a neutron and X-rays scattering study of the phase transitions of 4-n-octyl-4' -cyanobiphenyl (8CB) confined in unidirectional nanopores of porous alumina and porous silicon (PSi) membranes with an average diameter of 30 nm. Spatial confinement reveals a rich polymorphism, with at least four different low temperature phases in addition to the smectic A phase. The structural study as a function of thermal treatments and conditions of spatial confinement allows us to get insights into the formation of these phases and their relative stability. It gives the first description of the complete phase behavior of 8CB confined in PSi and provides a direct comparison with results obtained in bulk conditions and in similar geometric conditions of confinement but with reduced quenched disorder effects using alumina anopore membranes.

Molecular dynamics of a short-range ordered smectic phase nanoconfined in porous silicon.

4-n-octyl-4-cyanobiphenyl has been recently shown to display an unusual sequence of phases when confined into porous silicon (PSi). The gradual increase of oriented short-range smectic (SRS) correlations in place of a phase transition has been interpreted as a consequence of the anisotropic quenched disorder induced by confinement in PSi. Combining two quasielastic neutron scattering experiments with complementary energy resolutions, the authors present the first investigation of the individual molecular dynamics of this system. A large reduction of the molecular dynamics is observed in the confined liquid phase, as a direct consequence of the boundary conditions imposed by the confinement. Temperature fixed window scans reveal a continuous glasslike reduction of the molecular dynamics of the confined liquid and SRS phases on cooling down to 250 K, where a solidlike behavior is finally reached by a two-step crystallization process.

Solid state NMR and DSC methods for quantifying the amorphous content in solid dosage forms: an application to ball-milling of trehalose.

The purpose of this study was to determine quantitatively the amorphous fraction in crystalline-amorphous powder mixtures of trehalose, in order to assess the ability of the (13)C NMR technique for quantitative amorphous characterization. The NMR method is described in detail and its accuracy is compared to that of the DSC technique. Amorphous trehalose was prepared by mechanical milling. Samples with different amorphous fractions were prepared by physical mixing of purely amorphous and purely crystalline powders. The results reveal a close correlation between the imposed compositions of the physical mixtures and those determined by NMR and DSC, indicating that both are useful and accurate methods for compositional characterization of powders. The NMR method is then used to determine the evolution of the amorphous fraction in a trehalose powder, during a milling procedure which ultimately leads to a fully amorphous state.

[On pre-requirements to the use of audio-visual techniques in deviant children. Thoughts from the psychoanalytical treatment of a thirteen months aged child (author's transl)]. / De la condition préalable à l'emploi des techniques audio-visuelles chez les enfants déviants. Réflexion à partir du traitement psychanalytique d'une enfant de 13 mois.

This paper deals with the analytical cure of a child between 13 and 21 months and hospitalized since birth. In a first phase, one can see the start of a relationship, then the objectal relationship to primary objects: on the one hand the object food and on the other hand the therapist within the transfert. These two objects, impossible in the reality dimension from the start, are progressively characterized by "neantisation", which can reach symbolic tone. A scene in front of the picture of a child on knees of a nurse progressively introduces Nadia to the third register: the imagery one. Her behaviour is exemplary during the 17 scences on the mirror, during which she can progressively assume the image of her unified body under the view of the other, in demonstrating that she can only do it by symbolizing primary objects, in particular "to drink nothing". The symbolisation acquired at the oral level permits to verbalise on the same mode her relationship to the anal object, i.e. on the non destructive symbolic mode. This treatment raises the question of the use of audio-visual techniques for psychotic and autistic subjects, and recuses the pedagogic use of image for such subjects, taking into account the primary importance of symbolic function on imagery function demonstrated in this paper. This is a prerequisite for any research in the field of audiovisual techniques with psychotics.