Variety of the drift pumice clasts from the 2021 Fukutoku-Oka-no-Ba eruption, Japan.

Pumice rafts that arrived at the Nansei Islands, Japan, provided a unique opportunity to investigate the Fukutoku-Oka-no-Ba (FOB) eruption of August 2021. Despite drifting for two months for >1300 km, the drift pumice raft had a large volume and contained a variety of pumice clasts, some of which were deposited during a high tide in a typhoon, while others were washed up on a sandy beach. Most of the drift pumice clasts are gray in color, vesicular, and have a groundmass containing black enclaves, which are similar to those collected in the ocean near FOB about one week after the eruption. Rare black pumice and the main gray pumice components have similar trachytic compositions, with SiO2 = 61–62 mass% and total alkalis = 8.6–10 mass% (on an anhydrous basis). Both pumice types contain clinopyroxene, plagioclase, and rare olivine phenocrysts. Thin-section observations show that the gray pumice has more elongated vesicles as compared with the black pumice that has spherical vesicles, even where the two types of pumice are in the same clast. The glass in the black pumice is transparent and brown in color, while that in the gray pumice is colorless. No micro or nano-crystals were observed during electron and optical microscopy in the brown domain. Raman spectra of the brown-colored glass exhibit a clear magnetite peak, suggesting magnetite nanolites cause the brown color. High-Mg (100 × Mg/[Mg+Fe] = 92) olivine in the black pumice has an equilibrium temperature of 1240 °C and a rim diffusion profile indicative of re-equilibration with the surrounding melt over a period of hours to days.The textural relationships between the gray and black pumice suggest that the black pumice had become black and viscous before the two types of pumice mixed. Therefore, crystallization of magnetite nanolites and a corresponding increase in melt viscosity were important in the eruption preparation process, which then resulted in a large-scale Plinian eruption.

Diffusive transport of uranium and americium through clay rock down to ultra-trace levels

Clay rock is a potential host rock for the final disposal of nuclear waste in deep geological formations. In the scenario of ground water intrusion into the nuclear waste repository and subsequent corrosion of canisters and waste, possibly released actinides, such as uranium (U) and americium (Am), would be transported through the engineered barrier and clay host rock mainly by diffusion. Actinides are known to exhibit low solubility and are strongly sorbing under the reducing conditions of deep geological formations. Diffusion experiments are therefore difficult to perform due to analytical constraints. To our knowledge, the diffusion of U in clay rock has not been investigated below concentrations of 10-7molkg-1 clay (e.g., Joseph et al., 2013) and for Am, no diffusion experiments have been performed in a clay rock, considered suitable as host rock, such as Opalinus clay (OPA). This work aimed at the investigation of the diffusive behavior of U and Am down to ultra-trace concentrations (≪10-7molkg-1) in OPA. Laboratory-scale diffusion experiments were conducted with samples of OPA, obtained from the Mont Terri underground laboratory, Switzerland for up to 240 d. The OPA samples were placed in contact with synthetic pore water (I=0.22molL-1, pH=7.24), spiked with 5×10-9molL-1 of 233U and 243Am, respectively. After termination of the experiment, the OPA samples were segmented into thin layers of 20–400 µm. The obtained clay segments were analyzed for the 233U and 243Am content with accelerator mass spectrometry. Concentration profiles were determined down to 10-12molkg-1 clay for 233U and 5×10-10molkg-1 clay for 243Am. U showed a typical diffusion profile which can be interpreted by applying Fick's laws, while the Am profile was more complex, requiring further investigation of transport modes. These results will provide relevant insights into the transport behavior of U and Am in OPA over a wide range of concentrations down to ultra-trace levels.

Diffusion profile embedding as a basis for graph vertex similarity

We describe here a notion of diffusion similarity, a method for defining similarity between vertices in a given graph using the properties of random walks on the graph to model the relationships between vertices. Using the approach of graph vertex embedding, we characterize a vertex vi by considering two types of diffusion patterns: the ways in which random walks emanate from the vertex vi to the remaining graph and how they converge to the vertex vi from the graph. We define the similarity of two vertices vi and vj as the average of the cosine similarity of the vectors characterizing vi and vj. We obtain these vectors by modifying the solution to a differential equation describing a type of continuous time random walk.This method can be applied to any dataset that can be assigned a graph structure that is weighted or unweighted, directed or undirected. It can be used to represent similarity of vertices within community structures of a network while at the same time representing similarity of vertices within layered substructures (e.g., bipartite subgraphs) of the network. To validate the performance of our method, we apply it to synthetic data as well as the neural connectome of the C. elegans worm and a connectome of neurons in the mouse retina. A tool developed to characterize the accuracy of the similarity values in detecting community structures, the uncertainty index, is introduced in this paper as a measure of the quality of similarity methods.

SIMULTANEOUS ESTIMATION OF BERBERINE HYDROCHLORIDE AND INDOMETHACIN FOR IN VITRO DIFFUSION PROFILE BY UV SPECTROSCOPY

The present work aims to develop a precise, accurate and validation method to estimate berberine hydrochloride and indomethacin in gel formulations. In the present work, 50% phosphate buffer pH 7.4, 25% methanol and 25% ethanol blend was used as a solvent to increase the solubility of both the drugs. The analytical wavelength for berberine hydrochloride and indomethacin was 343 nm and 316nm, respectively. The method was validated for linearity, accuracy, precision, limit of detection, limit of quantification and robustness as per the ICH guidelines. The validated method was then applied in the diffusion study of the drugs from two different gel formulations. Beer’s law was obeyed in the concentration range of 4-14 µg/ml and 10-60 µg/ml for berberine hydrochloride and indomethacin, respectively. The method was found to be accurate and precise with relative standard deviation within 2% as per the ICH guidelines.

Time-dependent diffusion MRI probes cerebellar microstructural alterations in a mouse model of Down syndrome

The cerebellum is a complex system with distinct cortical laminar organization. Alterations in cerebellar microstructure are common and associated with many factors such as genetics, cancer and ageing. Diffusion MRI (dMRI) provides a non-invasive tool to map the brain structural organization, and the recently proposed diffusion-time (td)-dependent dMRI further improves its capability to probe the cellular and axonal/dendritic microstructures by measuring water diffusion at multiple spatial scales. The td-dependent diffusion profile in the cerebellum and its utility in detecting cerebellar disorders, however, are not yet elucidated. Here, we first deciphered the spatial correspondence between dMRI contrast and cerebellar layers, based on which the cerebellar layer-specific td-dependent dMRI patterns were characterized in both euploid and Ts65Dn mice, a mouse model of Down syndrome. Using oscillating gradient dMRI, which accesses diffusion at short td’s by modulating the oscillating frequency, we detected subtle changes in the apparent diffusivity coefficient of the cerebellar internal granular layer and Purkinje cell layer of Ts65Dn mice that were not detectable by conventional pulsed gradient dMRI. The detection sensitivity of oscillating gradient dMRI increased with the oscillating frequency at both the neonatal and adult stages. The td-dependence, quantified by ΔADC map, was reduced in Ts65Dn mice, likely associated with the reduced granule cell density and abnormal dendritic arborization of Purkinje cells as revealed from histological evidence. Our study demonstrates superior sensitivity of short-td diffusion using oscillating gradient dMRI to detect cerebellar microstructural changes in Down syndrome, suggesting the potential application of this technique in cerebellar disorders.

Morphological and diffusional changes in L. lactis biofilms

<p>Through their special way of life, biofilms have several advantages over organisms in planktonic growth. By being surface-attached and producing a mass of extracellular polymeric substances (EPS), microorganisms possess inherent self-immobilization, which decreases the expenditure of downstream processing in industrial applications. Furthermore, they are more resilient against environmental stress and toxic substances, such as antibiotics. An important factor here is diffusion, of substrate into the biofilm and metabolites through and out of the biofilm; however, these mechanisms are still poorly understood. By utilizing a specially developed diffusion model and CLSM FRAP microscopy, diffusion constants in the living, fully hydrated biofilm of <em>L. lactis</em> during development can be assessed. With it, heatmaps of diffusional constants and finally a diffusion profile encompassing a true 3D space of the living biofilm in growth can be generated. With those, possible hotspots and changes of diffusion inside the biofilm structure with regard to changing cultivation conditions and the substratum can be identified, thus furthering our understanding of diffusion in biofilms and how they react to their environment.</p> <p>The project is funded by the DFG (UL 170/14-1) and the collaborative research center (SFB) 926 on “microscale morphology of component surfaces” (MICOS).</p>