Three-dimensional pore structure and ion conductivity of porous ceramic diaphragms

The ion conductivity of two series of porous ceramic diaphragms impregnated with caustic potash was investigated by electrochemical impedance spectroscopy. To understand the impact of the pore structure on ion conductivity, the three-dimensional (3-D) pore geometry of the diaphragms was characterized with synchrotron x-ray absorption tomography. Ion migration was calculated based on an extended pore structure model, which includes the electrolyte conductivity and geometric pore parameters, for example, tortuosity (τ) and constriction factor (β), but no fitting parameters. The calculated ion conductivities are in agreement with the data obtained from electrochemical measurements on the diaphragms. The geometric tortuosity was found to be nearly independent of porosity. Pore path constrictions diminish with increasing porosity. The lower constrictivity provides more pore space that can effectively be used for mass transport. Direct measurements from tomographs of tortuosity and constrictivity opens new possibilities to study pore structures and transport properties of porous materials

Deciphering factors linked with reduced SARS-CoV-2 susceptibility in the Swiss HIV Cohort Study

BACKGROUND Factors influencing susceptibility to SARS-CoV-2 remain to be resolved. Using data of the Swiss HIV Cohort Study (SHCS) on 6,270 people with HIV (PWH) and serologic assessment for SARS-CoV-2 and circulating-human-coronavirus (HCoV) antibodies, we investigated the association of HIV-related and general parameters with SARS-CoV-2 infection. METHODS We analyzed SARS-CoV-2 PCR-tests, COVID-19 related hospitalizations, and deaths reported to the SHCS between January 1, 2020 and December 31, 2021. Antibodies to SARS-CoV-2 and HCoVs were determined in pre-pandemic (2019) and pandemic (2020) bio-banked plasma and compared to HIV-negative individuals. We applied logistic regression, conditional logistic regression, and Bayesian multivariate regression to identify determinants of SARS-CoV-2 infection and Ab responses to SARS-CoV-2 in PWH. RESULTS No HIV-1-related factors were associated with SARS-CoV-2 acquisition. High pre-pandemic HCoV antibodies were associated with a lower risk of subsequent SARS-CoV-2 infection and with higher SARS-CoV-2 antibody responses upon infection. We observed a robust protective effect of smoking on SARS-CoV-2-infection risk (aOR= 0.46 [0.38,0.56], p=2.6*10-14), which occurred even in previous smokers, and was highest for heavy smokers. CONCLUSIONS Our findings of two independent protective factors, smoking and HCoV antibodies, both affecting the respiratory environment, underscore the importance of the local immune milieu in regulating susceptibility to SARS-CoV-2

Methods in Creating, Transferring, & Measuring Cryogenic Samples for APT

ISSN:1431-9276ISSN:1435-811

Confocal microscopy of skin in vitro and ex vivo

Confocal laser scanning microscopy (CLSM) is a modern light microscopy technique that enables high-resolution three-dimensional imaging of biological and technical samples. The concept of a confocal microscope was first patented by Marvin Minsky in 1957; the first laser-scanning microscope was built in the early 1970s by Davidovits and Egger. In the mid-1980s, the commercialization of confocal laser scanning microscopes started, and during the last 15 years, instruments were improved especially regarding velocity and resolution, mainly due to faster computers and more effective optics and electronics. A detailed synopsis of the basics of confocal imaging as well as of various optical and technical aspects of microscope setups and image analysis is given by Pawley (1) or Diaspro (2)

3D geometry and topology of pore pathways in Opalinus clay : implications for mass transport

Clay-rich sedimentary rocks are considered as seal lithologies for hosting radioactive waste or as caprocks for geological carbon sequestration sites. Evaluation of the rock's sealing capacity requires a comprehensive understanding of mass transport processes, which, in turn, demands knowledge of the 3D structure of pore space. Here, the use of focused ion beam nanotomography (FIB-nt) in building realistic pore space models is demonstrated along with a novel approach employed to analyze the topology of the pore space. The method was applied to three samples of the Opalinus clay of in northern Switzerland which is considered as a candidate host rock formation for the disposal of radioactive waste. Due to resolution limitations the lower limit of analyzed pore radii was about 10 nm. Pore radii > 10 nm were related to a physical porosity of about 2 vol.%. Comparing the pore size distribution determined by FIB-nt with the one obtained by N2 adsorption analysis, FIB-nt revealed the structure of about 20% of the total pore space. The total external porosity determined by N2 adsorption analysis was in the range of 10 to 12 vol.%. Our approach to analyze the complex 3D structure of the pore space was based on converting the voxel based 3D structure into a 3D graph of the pore skeleton. A 3D graph representation permitted determination of the spatial distribution of pore space geometrical properties such as pore path orientation, pore path tortuosity and pore path length. Pore-paths in Opalinus clay show a preferred orientation within the bedding plane in combination with a comparatively low pore path tortuosity. Pore path tortuosity perpendicular to the bedding plane is higher by a factor of as much as five. Anisotropy in pore space is caused by spatial density variations of pore path orientation (i.e. preferred orientations of pore paths) in combination with an elongated pore shape (i.e. low tortuosity)