Mesoporous Silica Nanoparticles Loaded with Surfactant: Low Temperature Magic Angle Spinning 13C and 29Si NMR Enhanced by Dynamic Nuclear Polarization

We show that dynamic nuclear polarization (DNP) can be used to enhance NMR signals of13C and 29Si nuclei located in mesoporous organic/inorganic hybrid materials, at several hundreds of nanometers from stable radicals (TOTAPOL) trapped in the surrounding frozen disordered water. The approach is demonstrated using mesoporous silica nanoparticles (MSN), functionalized with 3-(N-phenylureido)propyl (PUP) groups, filled with the surfactant cetyltrimethylammonium bromide (CTAB). The DNP-enhanced proton magnetization is transported into the mesopores via 1H–1H spin diffusion and transferred to rare spins by cross-polarization, yielding signal enhancements εon/off of around 8. When the CTAB molecules are extracted, so that the radicals can enter the mesopores, the enhancements increase to εon/off ≈ 30 for both nuclei. A quantitative analysis of the signal enhancements in MSN with and without surfactant is based on a one-dimensional proton spin diffusion model. The effect of solvent deuteration is also investigated

Combustion model for thermite materials integrating explicit and coupled treatment of condensed and gas phase kinetics

Nanothermites are interesting energetic systems as their combustion driven by the oxidation of the metallic fuel associated with the reduction of the oxidizer, can produce extremely fast burning rates exceeding hundreds of m.s-1. In addition, by changing the reactant (composition, stoichiometry) geometry and compaction conditions, the control of the burning rate can be achieved, allowing the designer to customize the chemical energy for each application. To date, only rough combustion models exist, most restricting the combustion mechanisms to only condensed phase processes, thus providing an approximative prediction of structure-combustion performance relationships. This work presents a tri-phasic model for the combustion of Al/CuO powder considering 9 gaseous species (Al, Cu, O2, O, Al2O, Al2O2, AlO, AlO2, N2) and 4 condensed species (Al, Cu, CuO, Al2O3) that can be liquid or solid. The reactionnal scheme involves 12 heterogeneous reactions and 2 phase changes based on diffusional kinetics, while gaseous reactions are considered through a chemical equilibrium. A detailed description of the theoretical formulation and numerical method is presented, followed by a discussion of a closed-bomb simulation. This work highlights the great impact of the Al particles initial diameter on the pressure development in the chamber. After the initiation stage, the decomposition of CuO releases gaseous O2, which is spontaneously absorbed on the surface of submicronic Al particles and diffuses through alumina to react with pure Al. At high temperature, gaseous copper, aluminum sub-oxides and aluminum condense on both particle types. By contrast, Al particle micron-size limits the quantity of O2 absorption and gaseous species surface condensation, leading to the formation of a pressure pre-peak 4 times higher than the final chamber pressure

Covid-19 related fears of patients admitted to a psychiatric emergency department during and post-lockdown in switzerland: Preliminary findings to look ahead for tailored preventive mental health strategies

Background and Objectives: While the impact on mental health of 2019 coronavirus (COVID-19) has been extensively documented, little is known about its influence on subjective fears. Here, we investigate the COVID-19 impact and its related restrictions on fears of patients admitted to a psychiatric Emergency Department (ED) during and post-lockdown. Materials and Methods: A retrospective study on 1477 consultations at the psychiatric ED of the University Hospital of Geneva (HUG) was performed using a mixed-methods analysis. The first analysis section was qualitative, aiming to explore the type of fears, while the second section statistically compared fears (i) during lockdown (16 March 2020–10 May 2020) and (ii) post-lockdown (11 May 2020–5 July 2020). Fears were also explored among different patient-age sub-groups. Results: 334 patients expressed one/more fears. Both in lockdown and post-lockdown, fears mostly pertained to “containment measures” (isolation, loneliness). When compared lockdown vs. post-lockdown, fears about “work status” (deteriorating, losing work) prevailed in lockdown (p = 0.029) while “hopelessness” (powerless feeling, inability to find solutions) in post-lockdown (p = 0.001). “Self around COVID-19” (dying, getting sick) fear was relatively more frequent in youth (p = 0.039), while “hopelessness” in the elderly (p < 0.001). Conclusions: Collectively, these findings highlight that lockdown/post-lockdown periods generated temporally and demographically distinct COVID-19 related fears patterns, with special regard to youth and elderly, two particularly vulnerable populations when faced with sudden and unexpected dramatic events. For this reason, the particular ED “front-line service” status makes it a privileged observatory that can provide novel insights. From a mental health perspective, these latter can be translated into pragmatic, more personalized prevention strategies to reinforce specific resilience resources and mitigate the current and long-term pandemic’s impact

Psychiatric emergency admissions during and after COVID-19 lockdown: short-term impact and long-term implications on mental health

Background: The \u2018lockdown\u2019 measures, adopted to restrict population movements in order to help curb the novel coronavirus disease 2019 (COVID-19) pandemic, contributed to a global mental health crisis. Although several studies have extensively examined the impact of lockdown measures on the psychological well-being of the general population, little is known about long-term implications. This study aimed to identify changes in psychiatric emergency department (ED) admissions between two 8-week periods: during and immediately after lifting the lockdown. Methods: Socio-demographic and clinical information on 1477 psychiatric ED consultations at the University Hospital of Geneva (HUG) were retrospectively analyzed. Results: When grouped according to admission dates, contrary to what we expected, the post-lockdown group presented with more severe clinical conditions (as measured using an urgency degree index) compared to their lockdown counterparts. Notably, after the lockdown had been lifted we observed a statistically significant increase in suicidal behavior and psychomotor agitation and a decrease in behavior disorder diagnoses. Furthermore, more migrants arrived at the HUG ED after the lockdown measures had been lifted. Logistic regression analysis identified diagnoses of suicidal behavior, behavioral disorders, psychomotor agitation, migrant status, involuntary admission, and private resident discharge as predictors of post-lockdown admissions. Conclusions: Collectively, these findings can have implications concerning the prioritization of mental health care facilities and access for patients at risk of psychopathological decompensation in time of confinement policies, but above all, provide a foundation for future studies focusing on the long-term impact of the pandemic and its associated sanitary measures on mental health. Trial registration: Research Ethics Committee of Geneva, Registration number 2020\u201301510, approval date: 29 June 2020

Impact of the COVID\u201019 pandemic on psychiatric admissions to a large swiss emergency department: An observational study

The coronavirus disease 2019 (COVID\u201019) pandemic is a public health emergency with profound mental health consequences. The psychiatric emergency department (ED) plays a key role during this mental health crisis. This study aimed to investigate differences in admissions at a Swiss psychiatric ED from 1 April to 15 May during a \u201cpandemic\u2010free\u201d period in 2016 and a \u201cduringpandemic\u201d period in 2020. The study included 579 consultations at psychiatric ED in the \u201cduringpandemic\u201d period and 702 in the \u201cpandemic\u2010free\u201d period. Sociodemographic and clinical characteristics were compared, and logistic regression analysis was performed to identify variables associated with psychiatric admissions during the pandemic. A reduction in total psychiatric ED admissions was documented during COVID\u201019. Logistic regression analysis predicted the independent variable (ED admission during the pandemic) and estimated odds ratio (OR) for being unmarried/not in a relationship, arrival in an ambulance, suicidal behavior, behavioral disorders and psychomotor agitation. Though only statistically significant in bivariate analysis, patients were also more likely to be involuntarily hospitalized. This picture appears to be reversed from a sociodemographic and clinical point of view to our observation of psychiatric ED consultation in 2016. These findings highlight that the reduction in psychiatric ED admissions during the pandemic seems to be associated with living alone and more severe psychopathologies, which must alert psychiatrists to ensure access to mental health care in times of pandemic