Characterizing Low-Permeable Granitic Rock from Micrometer to Centimeter Scale: X-ray Microcomputed Tomography, Confocal Laser Scanning Microscopy and 14C-PMMA Method

AbstractFirst results of combining X-ray microcomputer tomography (µCT), confocal laser-scanning microscopy (CLSM) and 14C-polymethylmethacrylate (14C-PMMA) impregnation techniques in the study of granitic rock samples are reported. Combining results of µCT and CLSM with those of the 14C-PMMA technique, the mineral-specific porosity and morphology of the open pore space, as well as its connectivity, could be analyzed from a micrometer up to a decimeter scale.Three different types of granite were studied. In two cases part of the micro-fissure and pore apertures were found to be in a micrometer scale, but in one case all grain-boundary openings were below the detection limit. Micrometer-scal…

KPZ equation with realistic short-range-correlated noise

We study a realistic simulation model for the propagation of slow-combustion fronts in paper. In the simulations the deterministic part of the dynamics is that of the KPZ equation. The stochastic part, including in particular the short-range noise correlations, is taken from images of the structure of real paper samples. The parameters of the simulations are determined by using an inverse method applied to the experimental front data and by comparing the simulated and the experimental effective-noise distributions. Our model predicts well the shape of the spatial and temporal correlation functions, including the location of the crossovers from short-range (SR) to long-range (LR) behavior. T…

Soft X-ray tomography of phenotypic switching and the cellular response to antifungal peptoids in Candida albicans.

The opportunistic pathogen Candida albicans can undergo phenotypic switching between a benign, unicellular phenotype and an invasive, multicellular form that causes candidiasis. Increasingly, strains of Candida are becoming resistant to antifungal drugs, making the treatment of candidiasis difficult, especially in immunocompromised or critically ill patients. Consequently, there is a pressing need to develop new drugs that circumvent fungal drug-resistance mechanisms. In this work we used soft X-ray tomography to image the subcellular changes that occur as a consequence of both phenotypic switching and of treating C. albicans with antifungal peptoids, a class of candidate therapeutics unaf…

X-ray microtomography and laser ablation in the analysis of ink distribution in coated paper

A novel method was developed for studying the ink-paper interface and the structural variations of a deposited layer of ink. Combining high-resolution x-ray tomography with laser ablation, the depth profile of ink (toner), i.e., its varying thickness, could be determined in a paper substrate. X-ray tomography was used to produce the 3D structure of paper with about 1 μm spatial resolution. Laser ablation combined with optical imaging was used to produce the 3D structure of the printed layer of ink on top of that paper with about 70 nm depth resolution. Ablation depth was calibrated with an optical profilometer. It can be concluded that a toner layer on a light-weight-coated paper substrate …

A prospect for computing in porous materials research: Very large fluid flow simulations

Abstract Properties of porous materials, abundant both in nature and industry, have broad influences on societies via, e.g. oil recovery, erosion, and propagation of pollutants. The internal structure of many porous materials involves multiple scales which hinders research on the relation between structure and transport properties: typically laboratory experiments cannot distinguish contributions from individual scales while computer simulations cannot capture multiple scales due to limited capabilities. Thus the question arises how large domain sizes can in fact be simulated with modern computers. This question is here addressed using a realistic test case; it is demonstrated that current …

Temporal and spatial persistence of combustion fronts in paper

The spatial and temporal persistence, or first-return distributions are measured for slow-combustion fronts in paper. The stationary temporal and (perhaps less convincingly) spatial persistence exponents agree with the predictions based on the front dynamics, which asymptotically belongs to the Kardar-Parisi-Zhang universality class. The stationary short-range and the transient behavior of the fronts are non-Markovian, and the observed persistence properties thus do not agree with the predictions based on Markovian theory. This deviation is a consequence of additional time and length scales, related to the crossovers to the asymptotic coarse-grained behavior. Peer reviewed

Herpes simplex virus 1 induces egress channels through marginalized host chromatin

AbstractLytic infection with herpes simplex virus type 1 (HSV-1) induces profound modification of the cell nucleus including formation of a viral replication compartment and chromatin marginalization into the nuclear periphery. We used three-dimensional soft X-ray tomography, combined with cryogenic fluorescence, confocal and electron microscopy, to analyse the transformation of peripheral chromatin during HSV-1 infection. Our data showed an increased presence of low-density gaps in the marginalized chromatin at late infection. Advanced data analysis indicated the formation of virus-nucleocapsid-sized (or wider) channels extending through the compacted chromatin of the host. Importantly, co…

Putting molecules in their place.

Each class of microscope is limited to imaging specific aspects of cell structure and/or molecular organization. However, imaging the specimen by complementary microscopes and correlating the data can overcome this limitation. Whilst not a new approach, the field of correlative imaging is currently benefitting from the emergence of new microscope techniques. Here we describe the correlation of cryogenic fluorescence tomography (CFT) with soft X‐ray tomography (SXT). This amalgamation of techniques integrates 3D molecular localization data (CFT) with a high‐resolution, 3D cell reconstruction of the cell (SXT). Cells are imaged in both modalities in a near‐native, cryopreserved state. Here we…

Detection of local specular gloss and surface roughness from black prints

A combination of optical and tomographic imaging techniques for inspection of local surface roughness and specular gloss of black prints and coated paper are introduced. A diffractive optical-element-based glossmeter (DOG) and a low-coherence interferometer (LCI) were used to obtain local information about the print in terms of topographic and gloss maps. X-ray microcomputed tomography (μCT) was used to obtain 3D local structural information of the coated paper. Gloss and topographic maps were used to determine statistical gloss and roughness parameters. These parameters were useful when analysing the surface condition of prints and coated paper. We found an orientation-dependent gloss slop…

Dual-capillary electroencapsulation of mesoporous silicon drug carrier particles for controlled oral drug delivery

Abstract The feasibility of electroencapsulation of mesoporous silicon (PSi) micro- and nanoparticles as a method to seal the PSi particles in mechanically processable solid units, and to facilitate time and site specific drug release from the pores of PSi particles, is of interest in the present work. Suitable microcapsules and micromatrix particles were produced in a single-step process using a setup with two electrospraying nozzles kept at high electric potentials of opposite polarities. The structures of the produced particles were analyzed by microscope and X-ray micro- and nanotomography imaging, and optimization of the electroencapsulation process production efficiency is discussed.

Chromatin organization regulates viral egress dynamics.

Various types of DNA viruses are known to elicit the formation of a large nuclear viral replication compartment and marginalization of the cell chromatin. We used three-dimensional soft x-ray tomography, confocal and electron microscopy, combined with numerical modelling of capsid diffusion to analyse the molecular organization of chromatin in herpes simplex virus 1 infection and its effect on the transport of progeny viral capsids to the nuclear envelope. Our data showed that the formation of the viral replication compartment at late infection resulted in the enrichment of heterochromatin in the nuclear periphery accompanied by the compaction of chromatin. Random walk modelling of herpes s…

Quantifying Changes in Nuclear Organization in Normal vs. Cancer Cells using X-ray Tomography

Kinetic Roughening in Slow Combustion of Paper

Results of experiments on the dynamics and kinetic roughening of one-dimensional slow-combustion fronts in three grades of paper are reported. Extensive averaging of the data allows a detailed analysis of the spatial and temporal development of the interface fluctuations. The asymptotic scaling properties, on long length and time scales, are well described by the Kardar-Parisi-Zhang (KPZ) equation with short-range, uncorrelated noise. To obtain a more detailed picture of the strong-coupling fixed point, characteristic of the KPZ universality class, universal amplitude ratios, and the universal coupling constant are computed from the data and found to be in good agreement with theory. Below …

Effect of a columnar defect on the shape of slow-combustion fronts

We report experimental results for the behavior of slow-combustion fronts in the presence of a columnar defect with excess or reduced driving, and compare them with those of mean-field theory. We also compare them with simulation results for an analogous problem of driven flow of particles with hard-core repulsion (ASEP) and a single defect bond with a different hopping probability. The difference in the shape of the front profiles for excess vs. reduced driving in the defect, clearly demonstrates the existence of a KPZ-type of nonlinear term in the effective evolution equation for the slow-combustion fronts. We also find that slow-combustion fronts display a faceted form for large enough e…

X-ray microtomography and laser ablation in the analysis of ink distribution in coated paper

A novel method was developed for studying the ink-paper interface and the structural variations of a deposited layer of ink. Combining high-resolution x-ray tomography with laser ablation, the depth profile of ink (toner), i.e., its varying thickness, could be determined in a paper substrate. X-ray tomography was used to produce the 3D structure of paper with about 1 lm spatial resolution. Laser ablation combined with optical imaging was used to produce the 3D structure of the printed layer of ink on top of that paper with about 70 nm depth resolution. Ablation depth was calibrated with an optical profilometer. It can be concluded that a toner layer on a light-weight-coated paper substrate …

Evaluating pulp stiffness from fibre bundles by ultrasound

A non-destructive ultrasonic tester was developed to measure the stiffness of pulp bundles. The mechanical properties of pulp are important when estimating the behaviour of paper under stress. Currently available pulp tests are tedious and alter the fibres structurally and mechanically. The developed tester employs (933 ± 15) kHz tweezer-like ultrasonic transducers and time-of-flight measurement through (9.0 ± 2.5) mm long and (0.8 ± 0.1) mm thick fibre bundles kept at (19.1 ± 0.4) °C and (62 ± 1)% RH. We determined the stiffness of soft wood pulps produced by three kraft pulping modifications: standard kraft pulp, (5.2 ± 0.4) GPa, prehydrolysis kraft pulp, (4.3 ± 0.4) GPa, and alkali extra…

Microstructure, porosity and mineralogy around fractures in Olkiluoto bedrock

3D distributions of minerals and porosities were determined for rock-core samples that included water-conducting fractures. The analysis of these samples was performed using conventional petrography methods, C-14-PMMA porosity analysis and X-ray tomography. It seems that the properties of rock around a water-conducting fracture depend on so many uncorrelated factors that no clear pattern emerged even for rock samples with a given type of fracture. We can conclude, however, that the present combination of methods can be used to infer novel structural information about alteration zones adjacent to fracture surfaces.

Nuclear aggregation of olfactory receptor genes governs their monogenic expression.

SummaryGene positioning and regulation of nuclear architecture are thought to influence gene expression. Here, we show that, in mouse olfactory neurons, silent olfactory receptor (OR) genes from different chromosomes converge in a small number of heterochromatic foci. These foci are OR exclusive and form in a cell-type-specific and differentiation-dependent manner. The aggregation of OR genes is developmentally synchronous with the downregulation of lamin b receptor (LBR) and can be reversed by ectopic expression of LBR in mature olfactory neurons. LBR-induced reorganization of nuclear architecture and disruption of OR aggregates perturbs the singularity of OR transcription and disrupts the…

Kardar–Parisi–Zhang scaling in kinetic roughening of fire fronts

Abstract We show that the roughening of fire fronts in slow combustion of paper [7] follows the scaling predictions of the Kardar–Parisi–Zhang equation with thermal noise. By improved experimental accuracy it is now possible to observe the short-time and short-range correlations of the interfaces. These do not adhere to any standard picture, and in particular, do not seem to be related to any of the existing models of front propagation in the presence of quenched disorder.

Interface Detection Using a Quenched-Noise Version of the Edwards-Wilkinson Equation

We report here a multipurpose dynamic-interface-based segmentation tool, suitable for segmenting planar, cylindrical, and spherical surfaces in 3D. The method is fast enough to be used conveniently even for large images. Its implementation is straightforward and can be easily realized in many environments. Its memory consumption is low, and the set of parameters is small and easy to understand. The method is based on the Edwards-Wilkinson equation, which is traditionally used to model the equilibrium fluctuations of a propagating interface under the influence of temporally and spatially varying noise. We report here an adaptation of this equation into multidimensional image segmentation, an…

Determination of the stochastic evolution equation from noisy experimental data

We have determined the coefficients of the Kardar-Parisi-Zhang equation as functions of coarse graining, which best describe the time evolution and spatial behavior observed for slow-combustion fronts in sheets of paper and magnetic flux fronts in a thin-film high-Tc superconductor. Reconstruction of the relevant equation of motion and its coefficients was mainly based on the inverse method proposed by Lam and Sander [Phys. Rev. Lett. 71, 561 (1993)]. The coefficient of the nonlinear term was also determined from the local slope-dependence of the front velocity.

Experimental realization of KPZ dynamics : slow combustion of paper

Palorintaman eteneminen paperissa

Scaling and Noise in Slow Combustion of Paper

We present results of high resolution experiments on kinetic roughening of slow combustion fronts in paper, focusing on short length and time scales. Using three different grades of paper, we find that the combustion fronts show apparent spatial and temporal multiscaling at short scales. The scaling exponents decrease as a function of the order of the corresponding correlation functions. The noise affecting the fronts reveals short range temporal and spatial correlations, and non-Gaussian noise amplitudes. Our results imply that the overall behavior of slow combustion fronts cannot be explained by standard theories of kinetic roughening. Peer reviewed

Soft X-Ray Tomography Reveals Gradual Chromatin Compaction and Reorganization during Neurogenesis In Vivo

Summary - The realization that nuclear distribution of DNA, RNA, and proteins differs between cell types and developmental stages suggests that nuclear organization serves regulatory functions. Understanding the logic of nuclear architecture and how it contributes to differentiation and cell fate commitment remains challenging. Here, we use soft X-ray tomography (SXT) to image chromatin organization, distribution, and biophysical properties during neurogenesis in vivo. Our analyses reveal that chromatin with similar biophysical properties forms an elaborate connected network throughout the entire nucleus. Although this interconnectivity is present in every developmental stage, differentiati…

Spinnova - The most sustainable textile fibre in the world

The global challenges that drive the currently emerging sustainable businesses are growing, as the world population grows on a steep curve. Climate change, marine resource pollution and water shortage and waste issues are among the most urgent ones that also drive the forest industry's new innovation. This is also the foundation that Spinnova's innovation is built on. It is directly related to several of the United Nation's Sustainability Goals for 2030. Spinnova's cellulose-based fibre is a solution that solves many sustainability issues in the textile industry, also with other materials than cotton: polluting microplastics from man-made fibres and manufacturing process…