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The textural and geometrical properties of the pore networks (i.e., such as pore size distribution, pore shape, connectivity, and tortuosity) provides a primary control on the fluid storage and migration of geofluids within porous carbonate reservoirs. These properties are highly variable because of primary depositional conditions, diagenetic processes and deformation. This issue represents an important challenge for the characterization and exploitation plan in this type of reservoirs. In this study, the complementary properties of neutrons and X-ray experiments are carried out to better understand the effects of pore network properties on the hydraulic behavior of porous carbonates. Neutrons have unique properties and are particularly suitable for this study due to the sensitivity of neutrons to hydrogen-based fluids. The used methodology combines dynamic neutron radiography (NR), integrated X-ray and neutron tomography (XCT, NCT), and computational fluid dynamics simulations (lattice-Boltzmann method) of porous carbonate reservoir analogs from central and southern Italy. Dynamic 2D NR images provide information regarding the fluid transport and the wetting front dynamics related to the effect of heterogeneities (e.g., fractures and deformation bands) at the microscale. The combination of NCT (dry and wet samples) and XCT (dry), generates more information regarding the effective pore space contribution to fluid flow. The fluid flow simulations generate information about the connected pore network and the permeability evaluated rock sample at saturated condition.

Summary: Root hairs and soil water content are crucial in controlling the release and diffusion of root exudates and shaping profiles of biochemical properties in the rhizosphere. But whether root hairs can offset the negative impacts of drought on microbial activity remains unknown.Soil zymography, 14C imaging and neutron radiography were combined to identify how root hairs and soil moisture affect rhizosphere biochemical properties. To achieve this, we cultivated two maize genotypes (wild‐type and root‐hair‐defective rth3 mutant) under ambient and drought conditions.Root hairs and optimal soil moisture increased hotspot area, rhizosphere extent and kinetic parameters (Vmax and Km) of β‐glucosidase activities. Drought enlarged the rhizosphere extent of root exudates and water content. Colocalization analysis showed that enzymatic hotspots were more colocalized with root exudate hotspots under optimal moisture, whereas they showed higher dependency on water hotspots when soil water and carbon were scarce.We conclude that root hairs are essential in adapting rhizosphere properties under drought to maintain plant nutrition when a continuous mass flow of water transporting nutrients to the root is interrupted. In the rhizosphere, soil water was more important than root exudates for hydrolytic enzyme activities under water and carbon colimitation. See also the Commentary on this article by Zhang et al., 237: 707–709. [ABSTRACT FROM AUTHOR]

Soils are considered the largest sink of microplastic (MP) in terrestrial ecosystems. However, little is known about the implications of MP on soil physical properties. We hypothesize that low wettability of MP induces soil water repellency, depending on MP content and size of MP and soil particles. We quantified wettability of mixtures of MP and sand. The sessile drop method (SDM) was applied to measure static contact angle (CA) of MP and glass beads at contents ranging from 0 to 100% (w/w). The results are extrapolated to varying combinations of MP and soil particle sizes based on specific surface area. Capillary rise was imaged with neutron radiography quantifying the effect of MP on dynamic CA, water imbibition, and water saturation distribution in sand. At 5% (w/w) MP content, static CA exhibited a steep increase to 80.2° for MP 20–75 μm and 59.7° for MP 75–125 μm. Dynamic CAs were approximately 40% lower than static CAs. Capillary rise experiments showed that MP 20–75 μm reduced water imbibition into sand columns (700–1,200 μm), with average dynamic CA of 40.3° at 0.35% (w/w) MP content and 51.8° at 1.05%. Decreased water saturation and increased tortuosity of flow paths were observed during imbibition peaking at 3.5% (w/w) local MP content. We conclude, in regions with high MP content. water infiltration and thus MP transport are hindered. Local low wettability induced by MP is expected to limit soil wettability and impede capillary rise. Core Ideas: There is high awareness of microplastic contaminating environments raising concern worldwide.Microplastic is found in terrestrial systems, but little is known about soil environments.Microplastics are inherently hydrophobic and represent a hydrophobic surface addition to soil.Consequently, they are potentially increasing soil water repellency.We present an analysis of microplastic within porous media and show effects on water dynamics. [ABSTRACT FROM AUTHOR]

We demonstrate a new image processing methodology for resolving gas bubbles travelling through liquid metal from dynamic neutron radiography images with an intrinsically low signal-to-noise ratio. Image pre-processing, denoising and bubble segmentation are described in detail, with practical recommendations. Experimental validation is presented—stationary and moving reference bodies with neutron-transparent cavities are radiographed with imaging conditions representative of the cases with bubbles in liquid metal. The new methods are applied to our experimental data from previous and recent imaging campaigns, and the performance of the methods proposed in this paper is compared against our previously achieved results. Significant improvements are observed as well as the capacity to reliably extract physically meaningful information from measurements performed under highly adverse imaging conditions. The showcased image processing solution and separate elements thereof are readily extendable beyond the present application, and have been made open-source. [ABSTRACT FROM AUTHOR]

Featured Application: The investigations provide information about important parameters needed for the modelling of design bases, and beyond design bases, nuclear accidents and processes occurring during the long-term dry storage of spent nuclear fuel. In situ neutron radiography experiments can provide information about diffusive processes and the kinetics of chemical reactions. The paper discusses requirements for such investigations. As examples of the zirconium alloy Zircaloy-4, the hydrogen diffusion, the hydrogen uptake during high-temperature oxidation in steam, and the reaction in nitrogen/steam and air/steam atmospheres, results of in situ neutron radiography investigations are reviewed, and their benefit is discussed. [ABSTRACT FROM AUTHOR]

Just after the start into the new millennium the concept for combined neutron and X-ray imaging was introduced by extending the standard configuration of the thermal neutron imaging NEUTRA instrument with a complementary 320 kV X-ray tube setup. Using essentially the same detector configuration for both neutron and X-ray imaging enables a pixel-wise (in radiography) and a voxel-wise (in tomography) correlation and combination of attenuation data. The optimal use and analyses of such complementary data sets depend on the specific investigation and research question and range from a combinatory interpretation of separately analyzed images to full data fusion approaches. Here, several examples from more than a decade of bimodal neutron and X-ray imaging at NEUTRA at PSI shall be reviewed. [ABSTRACT FROM AUTHOR]

Moisture is a driving factor in the long-term mechanical deterioration of canvas paintings, as well as for a number of physico--chemical degradation processes. Since the 1990s a number of publications have addressed the equilibrium hygroscopic uptake and the hygro-mechanical deformation of linen canvas, oil paint, animal glue, and ground paint. In order to visualise and quantify the dynamic behaviour of these materials combined in a painting mock-up or reconstruction, we have performed custom-designed experiments with neutron radiography and nuclear magnetic resonance (NMR) imaging. This paper reports how both techniques were used to obtain spatially and temporally resolved information on moisture content, during alternate exposure to high and low relative humidity, or in contact with liquids of varying water activities. We observed how the canvas, which is the dominant component in terms of volumetric moisture uptake, absorbs and dries rapidly, and, due to its low vapour resistance, allows for vapour transfer towards the ground layer. Moisture desorption was generally found to be faster than absorption. The presence of sizing glue leads to a local increase of moisture content. It was observed that lining a painting with an extra canvas results in a damping effect: i.e. absorption and drying are significantly slowed down. The results obtained by NMR are complementary to neutron radiography in that they allow accurate monitoring of water ingress in contact with a liquid reservoir. Quantitative results are in good agreement with adsorption isotherms. The findings can be used for risk analysis of paintings exposed to changing micro-climates or subjected to conservation treatments using water. Future studies addressing moisture-driven deformation of paintings can make use of the proposed experimental techniques. [ABSTRACT FROM AUTHOR]

Our understanding of soil and plant water relations is limited by the lack of experimental methods to measure water fluxes in soil and plants. Here, we describe a new method to noninvasively quantify water fluxes in roots. To this end, neutron radiography was used to trace the transport of deuterated water (D20) into roots. The results showed that (1) the radial transport of D2O from soil to the roots depended similarly on diffusive and convective transport and (2) the axial transport of D2O along the root xylem was largely dominated by convection. To quantify the convective fluxes from the radiographs, we introduced a convection-diffusion model to simulate the D2O transport in roots. The model takes into account different pathways of water across the root tissue, the endodermis as a layer with distinct transport properties, and the axial transport of D20 in the xylem. The diffusion coefficients of the root tissues were inversely estimated by simulating the experiments at night under the assumption that the convective fluxes were negligible. Inverse modeling of the experiment at day gave the profile of water fluxes into the roots. For 24-d-old lupine (Lupinus albus) grown in a soil with uniform water content, root water uptake was higher in the proximal parts of lateral roots and decreased toward the distal parts. The method allows the quantification of the root properties and the regions of root water uptake along the root systems. [ABSTRACT FROM AUTHOR]

Abstract: In the framework of the post-test examinations of the large-scale LOCA simulation tests at the fuel rod bundle scale, the hydrogen distributions in specimens prepared from the QUENCH-L0 and -L1 tests were studied by means of neutron radiography and tomography. In order to determine quantitative hydrogen concentrations, both, neutron radiography and tomography were calibrated using cladding tube segments with known hydrogen concentrations. The linear dependence of the total macroscopic neutron cross section with the H/Zr atomic ratio was determined for both methods. The hydrogen distributions in samples prepared from the two tests differ significantly as a first glance to the results obtained for the QUENCH-L1 shows. Whereas clearly visible hydrogen bands were found in samples of the QUENCH-L0 test with a time between burst and quenching of more than 70 s; in some specimens prepared from the QUENCH-L1 test only blurred bands could be detected. The reasons for these different behaviors can be the different times between reaching the temperature maxima and the quenching, as well as bending of the QUENCH-L1 bundle. In the QUENCH-L0 test the bundle was quenched immediately after reaching the maximal temperature. In QUENCH-L1 the hydrogen had about 130 s to diffuse and reach more homogeneous distributions without clear contrasts between the hydrogen bands and the neighboring regions in the neutron images. [Copyright &y& Elsevier]

We compared root responses of the Ni-hyperaccumulator plant Berkheya coddii Rossler with the non-accumulator plant Cicer arietinum L. to Ni heterogeneity in soil. We grew plants in growth containers filled with control soil, homogeneously spiked, and heterogeneously spiked soil with Ni concentrations of 62 and 125 mg kg¿1. Neutron radiography (NR) was used to observe the root distribution and the obtained images were analysed to reveal the root volumes in the spiked and unspiked segments of the growth container. There was no significant difference in root distribution pattern of B. coddii among different concentrations of Ni. Unlike B. coddii, the roots of C. arietinum initially grew into the spiked segments. However, the later developing roots did not penetrate the spiked segment suggesting an avoidance strategy. Our results indicate that, B. coddii does not forage towards the Ni-rich patches, although presence of Ni in soil changes its root morphology. [Copyright &y& Elsevier]

• Soil water evaporation can be delayed by the complex biofilm producer B. subtilis. • An accelerated retreat of the evaporation front initiates decelerated water loss. • Reduced soil hydraulic conductivity and surface tension explain the process. • Modifications are result of a continuous adaptation. When soils dry, water flow and nutrient diffusion cease as the hydraulic microenvironments vital for soil life become fragmented. To delay soil drying locally and related adverse effects, bacteria and plants modify their surroundings by releasing extracellular polymeric substances (EPS). As a result, the physical properties of hotspots like biological soil crusts or the rhizosphere differ from those of the surrounding bulk soil. Specifically, the presence of EPS delays evaporative soil drying. Despite the evidence of reduced evaporation from EPS-amended soils, the mechanisms controlling soil water content dynamics remain elusive. Thus, our study aimed to elucidate the potential of bacteria to modify their local environment when exposed to oscillations in soil water content induced by evaporative drying. We incubated sand microcosms with two contrasting strains of Bacillus subtilis for one week in a flow cabinet. At the end of the incubation period, local water loss was quantified and spatially resolved using time-series neutron radiography. Strain NCIB 3610, a complex biofilm producer steadily modified soil evaporation dynamics during the incubation period resulting in a substantial delay in soil drying due to hydraulic decoupling of the evaporation front from the soil surface. Evaporation dynamics remained largely unaltered in the microcosms inoculated with the domesticated strain 168 trp+ compared to the control treatment. The mechanism of hydraulic decoupling induced by NCIB 3610 was verified by estimates of diffusive fluxes and the position of the evaporation plane in the microcosm. Additionally, the role of polymeric substances in hydraulic decoupling was confirmed by an evaporation experiment using xanthan as an EPS analogue. [ABSTRACT FROM AUTHOR]

Composite specimens of steel-reinforced concrete (RC) strengthened with strain-hardening cement-based composite (SHCC) were characterized according to their water uptake and drying kinetics by neutron radiography imaging. The specimens were cracked in well-defined patterns, and some cracks were hydrophobized at the RC/SHCC interface. Qualitative and quantitative image evaluation revealed that capillary suction was very intense; within 1.2 min the cracks in both SHCC and RC filled with water completely, deep into the interior. Capillary transport through the matrices followed and led to moisture distribution throughout the body up to an elapsed time of 27 h. When drying, only macro-sized cracks emptied within about 1 h. Up until 46 h the original water frontier progressed further into the matrix. In parallel the specimen dried from its bottom face. Hydrophobization of cracked areas prior to application of SHCC proved a highly efficient measure to inhibit long-term ingress of water deep into the structure. [ABSTRACT FROM AUTHOR]

The drying process has a prominent impact on the volume changes, crack propagation and durability of concrete structures. This study is to quantify the moisture distribution in real-time drying cement mortars. Mortar prisms with different water-to-cement ratios (w/c) and superabsorbent polymers (SAP) amounts were cut into slices and prepared with distinct lengths of cut notches. They were subjected to accelerated drying during neutron radiography measurements. In mortars with higher w/c, the coarser pores accelerate water transport and lead to more rapid drying. The large voids and the SAP in the bulk of the specimens are emptied well before the exposed surface starts to dry out. The presence of notches enhances drying. However, the moisture loss through the notches is less efficient than through the external surfaces. The competition between evaporation from the surfaces and moisture transport within the material, in both liquid and gas forms, governs the moisture distribution evolution. [ABSTRACT FROM AUTHOR]

Cork is the natural material stripped from the outer bark of cork oak. It is still the most used stopper to seal wine bottles and to preserve wine during storage. Cork stoppers are sorted in different classes according to apparent defects, named lenticels, which can be related to the cork macroporosity. The more lenticels there are, the worst cork quality is. The present work aims at investigating defects analysis of cork stoppers from two classes by comparing images recorded by digital photography and neutron imaging. Surface analysis of defects obtained from photography leads to more surface defects in class 4 (6.7%) than in class 0 (4.1%). Neutron radiography and tomography are powerful methods that really show the defects inside the material. From neutron radiography and tomography, class 4 contains 7.5% of volume defects and class 0 5.9%. Moreover, tomography also allows observing defects distribution along the whole stopper and possible interconnectivity. [ABSTRACT FROM AUTHOR]

Abstract: Conversion of thermal and cold neutrons into a strong ∼1ns electron pulse with an absolute neutron detection efficiency as high as 50–70% makes detectors with 10B-doped Microchannel Plates (MCPs) very attractive for neutron radiography and microtomography applications. The subsequent signal amplification preserves the location of the event within the MCP pore (typically 6–10μm in diameter), providing the possibility to perform neutron counting with high spatial resolution. Different event centroiding techniques of the charge landing on a patterned anode enable accurate reconstruction of the neutron position, provided the charge footprints do not overlap within the time required for event processing. The new fast 2×2 Timepix readout with >1.2kHz frame rates provides the unique possibility to detect neutrons with sub-15μm resolution at several MHz/cm2 counting rates. The results of high resolution neutron radiography experiments presented in this paper, demonstrate the sub-15μm resolution capability of our detection system. The high degree of collimation and cold spectrum of ICON and BOA beamlines combined with the high spatial resolution and detection efficiency of MCP-Timepix detectors are crucial for high contrast neutron radiography and microtomography with high spatial resolution. The next generation of Timepix electronics with sparsified readout should enable counting rates in excess of 107 n/cm2/s taking full advantage of high beam intensity of present brightest neutron imaging facilities. [Copyright &y& Elsevier]

Abstract: A shortened loss of coolant scenario was simulated experimentally at fuel rod bundle scale in the QUENCH-L0 test. All pressurized specimens burst at temperatures between 790 and 855°C. The hydrogen distribution in the cladding of chosen fuel rod simulators was studied by neutron radiography and tomography. As the results of these investigations show, the inner oxidation level, depending on time between burst and cooling and the temperatures occurring during this time, are important parameters for the hydrogen uptake. No hydrogen uptake was measured for the specimen with less than 50s between burst and quenching. For longer time intervals, hydrogen enriched bands were formed. These bended bands are oriented non-symmetrically to the tube axis. The width of the bands and the maximal hydrogen concentrations seem to increase with time between burst and quenching and with the temperatures during this period. [Copyright &y& Elsevier]

Plants stimulate microbial enzyme production in the rhizosphere, regulating soil organic matter decomposition and nutrient cycling. The availability of labile organic compounds (i.e. exudates) and water is the main prerequisite for such microbial activity and enzyme production, thus shaping the rhizosphere. Root morphology (i.e., root hairs) and exudate composition define the spatial distribution of properties and functions in the rhizosphere. However, the role of root architecture and exudate composition in this spatial self-organization of the rhizosphere remains unknown. We coupled three in situ imaging approaches: 14C imaging to localize exudates, soil zymography to analyze enzyme activity distribution, and neutron radiography for water fluxes to trace the spatial structure of the rhizosphere of three maize genotypes (wild-type, mutant with defective root-hair prolongation rth3 , and mutant with reduced benzoxazinoid content in root exudates bx1). The co-localization of these three soil images revealed the pivotal role of both optimal water content (neutron radiography) and root exudation (14C imaging) for β-glucosidase production by the rhizosphere microbiome and its hydrolytic activity (zymography). Root hairs increased the exudate release and enlarged the spatial extent of increased β - glucosidase activity around the root axis by 35%, leading to a two-fold faster decomposition of 14C exudates compared to the mutant with defective root hairs. In contrast, benzoxazinoids suppressed β - glucosidase activity by 30%, reflecting decreased microbial activity, whereas their absence broadened the rhizosphere. Overall, root hairs in wild-type maize increased microbial activity (i.e. β - glucosidase production), whereas the benzoxazinoids in root exudates suppressed microorganisms. [Display omitted] • Zymography, 14C imaging, and neutron radiography were coupled to localize rhizosphere processes. • Exudates are released at root tip in wild-type maize, but along the whole root in rth3 and bx1 mutants. • Root hairs enlarged the spatial extent of increased β - glucosidase activity around the root by 35%. • Benzoxazinoids (secondary metabolites) suppressed β - glucosidase activity in the rhizosphere by 30%. • Hotspot co-localization revealed that exudates and water increased β - glucosidase activity. [ABSTRACT FROM AUTHOR]