Helium permeation through mixed matrix membranes based on polyimides and silicalite-1

Mixed matrix membranes based on modified polyimides and silicalite-1 were prepared and studied. The novel preparation approach consists in improvement of the interfacial adhesion by employment of the coupling agent 3-aminopropyltriethoxysilane in such a way which leads to forming of chemical bonds between polyimide and silicalite-1. Firstly polyimide chains were endcapped by this agent which subsequently enabled their reaction with groups naturally present on silicalite-1 surface. Membranes with silicalite-1 content up to 60 wt. % were prepared and characterized by SEM, light microscopy and permeation of gases, prevailingly of He. The accessibility of sililicalite-1 pores prior to embedding and after embedding into polymeric matrices was studied by an iodine indicator technique. The permeability of membranes for gases was measured using a semi-open permeation apparatus with a small volume. Helium permeability depended on filler content and increased monotonously with the increasing content of filler. There were, however, significant deviations of the permeability dependences on filler content from shapes predicted by Bruggeman’s model. The qualitative explanation of the data disagreement with the model was proposed based on a stratification of mixed matrix membranes found by SEM

Study of the Accessibility of Zeolite Crystals in Polyimide Matrices. A Route to Coatings Exhibiting Selective Permeation

The accessibility of void space in MFI-type zeolite crystals, isolated and embedded in a polyimide (PI) matrix, was studied using optical microscopy coupled with an iodine indicator technique (IIT). IIT was used to estimate the adhesion between the PI matrix and the zeolitic phase, the accessibility of the zeolite void space for gas molecules as well as for characterizing the spatial distribution of embedded crystals in the composite. The channel system of the zeolitic phase in as-synthesized composites with the majority of crystals covered by a layer of PI is occupied by the solvent molecules used in composite synthesis. In untreated composites, the zeolitic phase is inaccessible to iodine sorption. Colouring patterns and colouring kinetics have been used to characterize the efficiency of the treatment for removing the PI covering layer from the crystal surface. The same techniques can be applied to characterize the treatment with regard to the desorption of solvents ( N- methyl-2-pyrrolidone, N,N -dimethylformamide, n-heptane) from the silicalite-1 channel system

Depression in healthcare workers during COVID-19 pandemic:results from Czech arm of HEROES Study

The pandemic due to COVID-19 brought new risks for depression of health care workers, which may have differently influenced men and women. We aimed to investigate (1) whether health care workers in Czechia experienced an increase in depression during the COVID-19 pandemic, (2) which factors contributed the most to this change, and (3) whether the magnitude of the associations differed by gender. We studied 2564 participants of the Czech arm of the international COVID-19 HEalth caRe wOrkErS (HEROES) Study. Online questionnaire was administered to health care workers in summer 2020 (wave 0) and spring 2021 (wave 1). Depression was defined by reaching 10 or more points on the Patient Health Questionnaire. Logistic regression investigated the association of participant´s characteristics with depression and multivariable decomposition for non-linear models assessed, to what extent the characteristic explained the change in depression occurrence. The prevalence of depression increased twice during the pandemic (11% in wave 0 and 22% in wave 1). Stress accounted for 50% of the difference, experience of death due to COVID-19 for 15% and contact with COVID-19 patients for 14%. Greater resilience and sufficient personal protective equipment were strongly associated with lower occurrence of depression. The protective association of resilience with depression was stronger in men than in women. We conclude that interventions to promote mental health of health care workers in future health crisis should aim at decreasing stress and enhancing resilience. They should be delivered especially to individuals who have contact with the affected patients and may face their death.</p

Legislative Documents

Also, variously referred to as: House bills; House documents; House legislative documents; legislative documents; General Court documents

Helium permeation through mixed matrix membranes based on polyimides and silicalite-1

Mixed matrix membranes based on modified polyimides and silicalite-1 were prepared and studied. The novel preparation approach consists in improvement of the interfacial adhesion by employment of the coupling agent 3-aminopropyltriethoxysilane in such a way which leads to forming of chemical bonds between polyimide and silicalite-1. Firstly polyimide chains were endcapped by this agent which subsequently enabled their reaction with groups naturally present on silicalite-1 surface. Membranes with silicalite-1 content up to 60 wt. % were prepared and characterized by SEM, light microscopy and permeation of gases, prevailingly of He. The accessibility of sililicalite-1 pores prior to embedding and after embedding into polymeric matrices was studied by an iodine indicator technique. The permeability of membranes for gases was measured using a semi-open permeation apparatus with a small volume. Helium permeability depended on filler content and increased monotonously with the increasing content of filler. There were, however, significant deviations of the permeability dependences on filler content from shapes predicted by Bruggeman’s model. The qualitative explanation of the data disagreement with the model was proposed based on a stratification of mixed matrix membranes found by SEM