Nonlinear diffusion in two-dimensional ordered porous media based on a free volume theory.

A continuum nonlinear diffusion model is developed to describe molecular transport in ordered porous media. An existing generic van der Waals equation of state based free volume theory of binary diffusion coefficients is modified and introduced into the two-dimensional diffusion equation. The resulting diffusion equation is solved numerically with the alternating-direction fully implicit method under Neumann boundary conditions. Two types of pore structure symmetries are considered, hexagonal and cubic. The former is modeled as parallel channels while in case of the latter equal-sized channels are placed perpendicularly thus creating an interconnected network. First, general features of transport in both systems are explored, followed by the analysis of the impact of molecular properties on diffusion inside and out of the porous matrix. The influence of pore size on the diffusion-controlled release kinetics is assessed and the findings used to comment recent experimental studies of drug release profiles from ordered mesoporous silicates

Precipitation of metallic chromium during rapid cooling of Cr2O3 slags

The slag systems of CaO-SiO2- Cr2O3 and Al2O3-CaO-MgO-SiO2- Cr2O3 were analyzed. These slag systems occur in the production of stainless steel and are important from the process metallurgy point of view. Synthetic slag samples with different chromium oxide content were prepared and melted. The melted slag samples where then rapidly cooled on large steel plates, so that the high temperature microstructure was preserved. The samples were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The precipitation of different chromium oxide phases was studied, but most importantly the precipitation of metallic chromium was observed. These findings help us interpret industrial slag samples

First-passage statistics of colloids on fractals: Theory and experimental realization

In nature and technology, particle dynamics frequently occur in complex environments, for example in restricted geometries or crowded media. These dynamics have often been modeled invoking a fractal structure of the medium although the fractal structure was only indirectly inferred through the dynamics. Moreover, systematic studies have not yet been performed. Here, colloidal particles moving in a laser speckle pattern are used as a model system. In this case, the experimental observations can be reliably traced to the fractal structure of the underlying medium with an adjustable fractal dimension. First-passage time statistics reveal that the particles explore the speckle in a self-similar, fractal manner at least over four decades in time and on length scales up to 20 times the particle radius. The requirements for fractal diffusion to be applicable are laid out, and methods to extract the fractal dimension are established

Non-ergodicity of a globular protein extending beyond its functional timescale

Internal motions of folded proteins have been assumed to be ergodic, i.e., that the dynamics of a single protein molecule averaged over a very long time resembles that of an ensemble. Here, by performing single-molecule fluorescence resonance energy transfer (smFRET) experiments and molecular dynamics (MD) simulations of a multi-domain globular protein, cytoplasmic protein-tyrosine phosphatase (SHP2), we demonstrate that the functional inter-domain motion is observationally non-ergodic over the time spans 1012 to 107 s and 101 to 102 s. The difference between observational non-ergodicity and simple non-convergence is discussed. In comparison, a single-strand DNA of similar size behaves ergodically with an energy landscape resembling a one-dimensional linear chain. The observed non-ergodicity results from the hierarchical connectivity of the high-dimensional energy landscape of the protein molecule. As the characteristic time for the protein to conduct its dephosphorylation function is 10 s, our findings suggest that, due to the non-ergodicity, individual, seemingly identical protein molecules can be dynamically and functionally different

Microstructural evolution of inconel 625 during thermal aging

Inconel 625 is due to alloying elements prone to precipitation of different intermetallic phases and secondary carbides during thermal aging. The base of investigation is nickel superalloy Inconel 625 in hot rolled state. Thermal aging was conducted at temperature 650 °C with different duration of treatment for each sample. Microstructural analysis was performed by light microscope and scanning electron microscope. The results of microstructure observation showed the precipitation of intermetallic γ››- Ni3Nb phase in the γ matrix and δ-Ni3Nb phase with M23C6 secondary carbides at the grain boundaries

Recognising and Valuing Student Engagement in Science Museums

Student engagement with museum content is an integral part of the mission of many institutions, including science museums. Our research utilises a sociological lens to bring a new perspective on engagement in such spaces. Specifically, we draw on qualitative data from student visits to a science museum to explore what engagement might be possible, by whom, and under what circumstances. The students in focus are of underrepresented ethnic and cultural backgrounds in the museum, and do not have high levels of science capital. Our findings reveal that moments of engagement occur when there is alignment between personal habitus and capital – the students’ dispositions and practices – and the field, the museum's conventions and rules, as well as its objects and exhibits. However, this engagement was often with the historical or social aspects of exhibits, rather than the science behind them. We propose this approach to engagement as a useful tool for museum practitioners

Improved lifestyle is associated with improved depression, anxiety and well-being over time in UK healthcare professionals during the COVID-19 pandemic: insights from the CoPE-HCP cohort study.

BACKGROUND: One potential modifiable factor to improve the mental health of healthcare professionals (HCPs) during the pandemic is lifestyle. AIMS: This study aimed to assess whether an improved lifestyle during the pandemic is associated with improved mental health symptoms and mental well-being in HCPs over time. METHODS: This was a cohort study involving an online survey distributed at two separate time points during the pandemic (baseline (July-September 2020) and follow-up (December 2020-March 2021)) to HCPs working in primary or secondary care in the UK. Both surveys assessed for major depressive disorder (MDD) (Patient Health Questionnaire-9 (PHQ-9)), generalised anxiety disorder (GAD) (Generalised Anxiety Disorder-7 (GAD-7)), mental well-being (Short Warwick-Edinburgh Mental Well-being Score (SWEMWBS)) and self-reported lifestyle change (compared with the start of the pandemic) on multiple domains. Cumulative scores were calculated to estimate overall lifestyle change compared with that before the pandemic (at both baseline and follow-up). At each time point, separate logistic regression models were constructed to relate the lifestyle change score with the presence of MDD, GAD and low mental well-being. Linear regression models were also developed relating the change in lifestyle scores from baseline to follow-up to changes in PHQ-9, GAD-7 and SWEMWBS scores. RESULTS: 613 HCPs completed both baseline assessment and follow-up assessment. Consistent significant cross-sectional associations between increased lifestyle change scores and a reduced risk of MDD, GAD and low mental well-being were observed at both baseline and follow-up. Over the study period, a whole unit increase in the change in novel scores (ie, improved overall lifestyle) over 4 months was inversely associated with changes in PHQ-9 (adjusted coefficient: -0.51, 95% confidence interval (CI): -0.73 to -0.30, p<0.001) and GAD-7 scores (adjusted coefficient: -0.32, 95% CI: -0.53 to -0.10, p=0.004) and positively associated with the change in SWEMWBS scores (adjusted coefficient: 0.37, 95% CI: 0.18 to 0.55, p<0.001). CONCLUSIONS: Improved lifestyle over time is associated with improved mental health and mental well-being in HCPs during the pandemic. Improving lifestyle could be a recommended intervention for HCPs to help mitigate the mental health impact during the current and future pandemics. TRIAL REGISTRATION NUMBER: NCT04433260

Lysine/RNA-interactions drive and regulate biomolecular condensation.

Cells form and use biomolecular condensates to execute biochemical reactions. The molecular properties of non-membrane-bound condensates are directly connected to the amino acid content of disordered protein regions. Lysine plays an important role in cellular function, but little is known about its role in biomolecular condensation. Here we show that protein disorder is abundant in protein/RNA granules and lysine is enriched in disordered regions of proteins in P-bodies compared to the entire human disordered proteome. Lysine-rich polypeptides phase separate into lysine/RNA-coacervates that are more dynamic and differ at the molecular level from arginine/RNA-coacervates. Consistent with the ability of lysine to drive phase separation, lysine-rich variants of the Alzheimer's disease-linked protein tau undergo coacervation with RNA in vitro and bind to stress granules in cells. Acetylation of lysine reverses liquid-liquid phase separation and reduces colocalization of tau with stress granules. Our study establishes lysine as an important regulator of cellular condensation

Effect of nanostructuration on compressibility of cubic BN

Compressibility of high-purity nanostructured cBN has been studied under quasi-hydrostatic conditions at 300 K up to 35 GPa using diamond anvil cell and angle-dispersive synchrotron X-ray powder diffraction. A data fit to the Vinet equation of state yields the values of the bulk modulus B0 of 375(4) GPa with its first pressure derivative B0' of 2.3(3). The nanometer grain size (\sim20 nm) results in decrease of the bulk modulus by ~9%