Undisturbed Matrix Research Articles

The importance of a realistic leakage evaluation to support public awareness and acceptance for carbon capture and storage

Carbon Capture and Storage is not only highly recommended by the IPCC as a mechanism to significantly lower carbon emissions to the atmosphere, it is now also gaining traction in terms of large-scale implementation. Its importance is increasing in many parts of the world to directly decrease emissions from industrial sources, but also to lower the carbon footprint of blue hydrogen production.With most CCS projects being planned for offshore locations, public acceptance is less of a determining factor than it used to be 10-20 years ago, where discussions were rather for onshore locations. CO2 leakage has always been a risk highlighted in the public debate, while no or minimal leakage has been reported for current CCS projects worldwide. However, as scientific community, we need to realistically highlight the risk of leakage across sealing units for CO2 stored to inform various stakeholders like regulators, the public and of course also operating companies.Caprock leakage needs to be studied across various length and time scales, considering the undisturbed matrix as well as fracture networks and faults; we need to consider advective and diffusive flow and transport and incorporate mineral alterations, potentially leading to changes in hydraulic or mechanical properties.This talk will highlight the current state of research, advancements and future research required for a realistic evaluation of caprock leakage. It will be based on past research related to matrix transport as well as current research focusing on single and multiphase flow along faults and fractures.

A Scaling Approach for Retention Properties of Crystalline Rock: Case Study of the In‐Situ Long‐Term Sorption and Diffusion Experiment (LTDE‐SD) at the Äspö Hard Rock Laboratory in Sweden

AbstractThe in‐situ long‐term sorption and diffusion (LTDE‐SD) experiment performed at the Äspö Hard Rock Laboratory in Sweden aims at increasing knowledge of sorption and diffusion processes of radionuclides in natural fractures and granodiorite matrix under in‐situ conditions. This paper presents a comprehensive modeling exercise focusing on the scaling approach for sorption and diffusion parameters from laboratory to in‐situ conditions using the LTDE‐SD data set for six representative radionuclides. The near‐surface heterogeneities at both the fracture surface and rock matrix were evaluated by the conceptual model with high porosity, diffusivity, and sorption capacity, as well as their gradual changes at the near‐surface zones. The modeling results for non‐sorbing Cl‐36 and weak‐sorbing Na‐22 validated the model concept and parameter estimation of porosity and diffusivity by considering a 5‐mm‐thick disturbed zone with gradual parameter changes and an undisturbed matrix characterized by constant parameters. The effective diffusivities (De) of these cationic and anionic tracers showed typical cation excess and anion exclusion effects; however, the cation excess diffusion was more pronounced due to the heterogeneous pore networks in this granodiorite. The modeling results for high‐sorbing tracers (Cs‐137, Ra‐226, Ni‐63, and Np‐237) with different sorption mechanisms validated the scaling approaches of distribution coefficients (Kd) as a function of particle size and their relation to near‐surface disturbances. Sorption dependence on particle size could be understood in relation to different sorption mechanisms and mineralogical features. This modeling exercise provided key recommendations toward better scaling approaches for estimating reliable De and Kd parameters under in‐situ conditions.

Structural and Optical Characteristics of 4H-SiC UV Detectors Irradiated with Argon Ions

The results of a study into the effect of irradiation with heavy Ar ions on the structural and optical characteristics of 4H-SiC are presented. It is shown that even upon single-time irradiation with 53-MeV Ar ions at a fluence of 1 × 1010 cm–2 there are at least two powerful local regions with negative deformation dominant in the structure of silicon carbide. Also, a region with positive deformation is observed in the structure. The formation of localized clusters with negative and positive deformations along with the undisturbed matrix gives rise to linear-type defects that partially relieve stresses in the structure. It is assumed that, upon irradiation with Ar ions, the resulting complex defect structure provides the effect of point-defect gettering and leads to a quantum efficiency of 4H-SiC UV photodetectors that is comparable with that of the initial samples.

Multivariate Scaling of the Characteristic Features Based on Pseudo-Inverse Operations for Recognition Problems Solving

Some approach to multidimensional information scaling of the characteristics features based on results of theory of perturbation of pseudo-inverse and projective matrices and solutions of systems of linear algebraic equations is proposed. The method and algorithm of a piecewise hyperplane clusters creating with the verification of a given criterion for effectiveness of the proposed method of clustering is developed. The problem of stability of main indicators of the classifier in presence disturbances in source information is investigated. The proposed method for determining influence of source data errors on main indicators of the classifier provides presentation of undisturbed information matrix in form of splitting matrices of special kind. Advantages of the proposed approach are demonstrated, an example of using the method of scaling characteristic features for recognizing fingerspelling alphabet of sign language is given.

Структурные и оптические характеристики ультрафиолетовых 4H-SiC-детекторов, облученных ионами аргона

Abstract The paper presents the results of a study of the effect of irradiation with heavy Ar ions on the structural and optical characteristics of 4H-SiC. It has been shown that as a result of already single irradiation with Ar ions with an energy of 53 MeV with a fluence of 1٠1010 cm-2, at least 2 powerful local regions with negative deformation prevail in the structure of silicon carbide. Along with this, a region with positive deformation is also observed in the structure. The formation of localized clusters with negative and positive deformations, along with the undisturbed matrix, is accompanied by the formation of linear type defects that partially relieve stresses in the structure. It is assumed that the resulting complex defect structure upon irradiation with Ar ions provides the effect of gettering of point defects and leads to the quantum efficiency of 4H-SiC UV photodetectors at the level of the initial samples.

Preparation of topsoil alternatives for open-pit coal mines in the Hulunbuir grassland area, China

To solve topsoil shortages caused by the thinner topsoil layer resulting from open-pit land reclamation in northwestern Chinese grassland areas, the overlying rock and soil layer of an open-pit coal mine in Inner Mongolia was used as a matrix, and different additives were incorporated to improve topsoil alternatives for dump reclamation. The physical and chemical properties and nutrient composition of the undisturbed matrix and the weathering substances in layers II and III of the topsoil were compared and analyzed, with local topsoil as the control. The results showed that the III layer of the matrix after weathering had higher nutrient content, pH of 7.83, EC of 83 μS/m, and as such was more suitable as a substitute for topsoil. Given the limitations of overlying strata, such as excessive viscosity, an imbalanced nutrient content and a lack of soil microorganisms, additives composed of vermiculite, peat, livestock manure, nitrohumic acid and microbial agents in different proportions were incorporated. Field experiments showed that the optimal formula of substitute material was a ratio of m (subclay):m (peat) = 20:1 and an applied microbial agent concentration of 0.15 kg/m2. Compared to the original topsoil, the substitute material had a higher moisture content (32% for substitute and 20% for original topsoil), significantly higher phosphorus and potassium contents, and similar or greater numbers of microorganisms. The greatest increase in alfalfa plant height was 72%, the dry weight of the aboveground part increased by 26%.

Investigation of InAlN Layers Surface Reactivity after Thermal Annealings: A Complete XPS Study for HEMT

The surface chemistry of InAlN ultra-thin layers, having undergone an oxidation procedure usually running through the HEMT fabrication process (850°C, O2 and O2+Ar) is studied by XPS. The suitability of XPS analysis to operate as a retro-engineering tool for added value microelectronic devices fabrication is shown. A precise examination of the Al2p, In3d5/2, N1s, and O1s peaks directly informs about spatial and atomic arrangement. The formation of a covering 3 nm surface oxide is evidenced after O2 annealing. Once annealed, two specific additional N1s contributions are shown, at higher (404.0 eV) and lower binding energies (397.4 eV) compared to the InAlN matrix one (396.5 eV). To our knowledge, such fingerprint is rather unusual for ternary III-V materials. It reveals the formation of a nitrogen deficient interlayer, situated between the oxide overlayer and the undisturbed matrix, and the presence of interstitial N2 molecules trapped at the interface. After Ar annealing, both oxide and interface layers are partially reorganized. InAlN reactivity toward higher annealing temperature (950°C) and its stability over time is finally discussed. N2 molecules are unstable and progressively eliminated in time although nitrogen deficient interlayer still remains. Thermal treatments below 850°C are recommended to preserve the barrier chemical integrity.

The influence of landscape matrix on isolated patch use by wide‐ranging animals: conservation lessons for woodland caribou

For conservation purposes, it is important to design studies that explicitly quantify responses of focal species to different land management scenarios. Here, we propose an approach that combines the influence of landscape matrices with the intrinsic attributes of remaining habitat patches on the space use behavior of woodland caribou (Rangifer tarandus caribou), a threatened subspecies of Rangifer. We sought to link characteristics of forest remnants and their surrounding environment to caribou use (i.e., occurrence and intensity). We tracked 51 females using GPS telemetry north of the Saguenay River (Québec, Canada) between 2004 and 2010 and documented their use of mature forest remnants ranging between 30 and ∼170 000 ha in a highly managed landscape. Habitat proportion and anthropogenic feature density within incremental buffer zones (from 100 to 7500 m), together with intrinsic residual forest patch characteristics, were linked to caribou GPS location occurrence and density to establish the range of influence of the surrounding matrix. We found that patch size and composition influence caribou occurrence and intensity of use within a patch. Patch size had to reach approximately 270 km2 to attain 75% probability of use by caribou. We found that small patches (<100 km2) induced concentration of caribou activities that were shown to make them more vulnerable to predation and to act as ecological traps. Woodland caribou clearly need large residual forest patches, embedded in a relatively undisturbed matrix, to achieve low densities as an antipredator strategy. Our patch-based methodological approach, using GPS telemetry data, offers a new perspective of space use behavior of wide-ranging species inhabiting fragmented landscapes and allows us to highlight the impacts of large scale management. Furthermore, our study provides insights that might have important implications for effective caribou conservation and forest management.

Microstructural observations of shear zones in sensitive clay

The present work assesses the structure and evolution of shear zones in sensitive ‘quick’ clays from the initiation to the well-established state. This assessment is done by utilizing laboratory and small scale field experiments combined with the analysis of thin sections in light microscopy and SEM. High resolution X-ray tomography (‘micro-CT’) is also applied. In combination, detailed 2D and 3D visualization of the shear zones is achieved. Shear zones are suggested to be formed in mm-thick continuous fields of displacement. With increasing shear displacement, sets of micron-sized minor shears develop within the main shear zone. These initiate, terminate and merge both in the plane and out-of-the-plane directions. The minor shears are characterized by distinct particle reorientation where the flaky clay particles and mica grains are aligned parallel to the direction of shear. A porosity reduction is observed in the minor shears. This is a direct observation of material contractancy and implies migration of water from the shear zone into the undisturbed matrix. The width of the main shear zone is considered to be related to the applied rate of shear while the minor shears have a width determined by the micro-texture of the sediment. The observed multi-scale structure of the shear zones, which is governed by complex inner mechanics, is challenging the ‘smooth shear zone’ concept that is commonly applied in numerical simulations. This is motivating a further improvement of such tools and the testing of other types of clay sediments.

Effects of drilling and stress release on transport properties and porewater chemistry of crystalline rocks

► The verification of matrix diffusion in crystalline rocks largely relies on laboratory experiments. ► The effects of sample preparation, drilling and stress release are explored on samples drilled with traced drilling fluid. ► Quantification of the induced uncertainty on derived parameters occurred by mass balance, 1D and 2D transport modelling. ► The mechanically disturbed zone with modified diffusion properties extends to about 6 mm into the drillcore. ► The chemically disturbed zone with modified porewater chemistry makes less than 2.5% of the rock’s total pore volume. The experimental verification of matrix diffusion in crystalline rocks largely relies on indirect methods performed in the laboratory. Such methods are prone to perturbations of the rock samples by collection and preparation and therefore the laboratory-derived transport properties and fluid composition might not represent in situ conditions. We investigated the effects induced by the drilling process and natural rock stress release by mass balance considerations and sensitivity analysis of analytical out-diffusion data obtained from originally saturated, large-sized drillcore material from two locations drilled using traced drilling fluid. For in situ stress-released drillcores of quartz-monzodiorite composition from the Äspö HRL, Sweden, tracer mass balance considerations and 1D and 2D diffusion modelling consistently indicated a contamination of <1% of the original pore water. This chemically disturbed zone extends to a maximum of 0.1 mm into the drillcore (61.8 mm × 180.1 mm) corresponding to about 0.66% of the total pore volume (0.77 vol.%). In contrast, the combined effects of stress release and the drilling process, which have influenced granodioritic drillcore material from 560 m below surface at Forsmark, Sweden, resulted in a maximum contamination of the derived porewater Cl − concentration of about 8%. The mechanically disturbed zone with modified diffusion properties covers the outermost ∼6 mm of the drillcore (50 mm × 189 mm), whereas the chemically disturbed zone extends to a maximum of 0.3 mm based on mass balance considerations, and to 0.15 mm to 0.2 mm into the drillcore based on fitting the observed tracer data. This corresponds to a maximum of 2.4% of the total pore volume (0.62 vol.%) being affected by the drilling-fluid contamination. The proportion of rock volume affected initially by drilling fluid or subsequently with experiment water during the laboratory diffusion and re-saturation experiments depends on the size of the drillcore material and will become larger the smaller the sample used for the experiment. The results are further in support of matrix diffusion taking place in the undisturbed matrix of crystalline rocks at least in the cm range.

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9-ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3-year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more-lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already-declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.

TEM analysis of (Ni,Fe)Si2 precipitates in Si

AbstractThe present article provides evidence that Fe impurity atoms in silicon can be gathered by NiSi2 precipitates at temperatures near RT via solid‐state diffusion. Mixtures of silicon and silicide grains, resulting from annealing at 800–900 °C, were analysed. High supersaturation (about 1019–1020 atoms/cm3) of metal impurities in Si was achieved locally by incorporation of nickel and iron atoms from silicide grains into silicon grains during ion milling for TEM specimen preparation. Consequently, particles with local densities of 1013–1014 precipitates/cm3 and average volumes of 10−18–10−16 cm3 formed via diffusion and precipitation. Precipitates with an irregular octahedra shape and platelet‐like habit were found at dislocations. Less frequently, precipitates with a regular octahedra shape were observed in undisturbed matrix. HRTEM images and SAD patterns demonstrate that all precipitates have NiSi2 structure. Ni contents were detected for all precipitates by EDX analysis, but accumulated amounts of Fe could only be proven for some precipitates at dislocations. Quantitative EDX‐analysis revealed Fe/(Fe + Ni) ratios between 16 and 30 at% for these ternary precipitates.

Neutron spectroscopy of H impurities in PdD: Covibrations of the H and D atoms

Three powder samples of solid isotopic solutions ${\text{PdD}}_{1\ensuremath{-}x}{\text{H}}_{x}$ with $x=0.050$, 0.072, and 0.091 are prepared under high pressure, and the spectra of their optical vibrations are studied by inelastic neutron scattering at ambient pressure and 5 K using the high-luminosity IN1-BeF spectrometer at ILL, Grenoble. These spectra are shown to be well represented by a linear combination of a contribution from the undisturbed matrix of stoichiometric PdD and a contribution due to the H impurity. The optical spectrum of PdD consists of a strong peak at 37 meV with a shoulder extending to 65 meV. The spectrum due to the H impurity is composed of a broad peak of defect H modes centered at 68 meV and superimposed on a broad N-shaped feature with a range of negative intensity near 36 meV and a shallow maximum at 45 meV. Simulations using the Born-von K\'arm\'an model show that this unusual feature is a result of the formation of a band of optical vibrations of the D and H atoms with equal frequencies (covibrations) caused by H-D interactions.

Modelling of transport in fractures with complex matrix properties

ABSTRACTIn the ongoing Swedish site investigations it has been found that the rock matrix adjacent to many open fractures has been altered. The alteration can extend from mm to several cm. The altered rock can have different sorption and diffusion properties compared to the undisturbed rock and this may influence the retardation of the nuclides. The paper presents how the Channel Network model has been adapted to handle diffusion into a matrix composed of several layers with different properties in addition to the infinite undisturbed matrix. For one channel, the solution for the Residence Time Distribution, RTD, may be found in the Laplace-plane. For the transport in the Channel Network, a particle tracking technique is used to determine the paths followed by solute particles. The RTD for this path is obtained using convolution, which in the Laplace-plane means multiplication of the transfer functions for each channel. The inversion to the time-plane is made by numerical inversion of the Laplace transforms for each path. The method has been tested with data from the TRUE (Tracer Retention Understanding Experiments) project, Task 6F, fluid flow and solute transport in two features in 100 m scale where a complex matrix was modelled. The model was used to predict the transport of the tracers (I-129), Cs-137, and Am-241) over some 20 m. The paper also addresses how the RTD is influenced by the different retardation mechanisms under Site Characterisation (SC) as well as Performance Assessment (PA) conditions.

DO DISTURBANCES ALTER COMPETITIVE HIERARCHIES? MECHANISMS OF CHANGE FOLLOWING GAP CREATION

Many studies have documented that patterns of species composition change after gap creation, but few have addressed the processes responsible for this change. The idea of competitive reduction, that disturbance removes biomass, reducing competitive intensity and allowing competitively inferior fugitive species to colonize, has been widely accepted but rarely tested. We suggest an alternative hypothesis, competitive change, in which changes associated with disturbance may act to alter the competitive hierarchy. Under these changed conditions, species characteristic of gaps may be competitively superior to species characteristic of undisturbed matrix areas. We quantified competitive response ability for survival and relative growth for three target species (Andropogon gerardii, a matrix grass; Coreopsis tripteris, a matrix forb; and Ratibida pinata, a forb characteristic of gaps) in undisturbed matrix vegetation and in soil mound disturbances in a northern Ohio prairie community. For survival, a weak competitive hierarchy developed following gap creation. In contrast, for relative growth, gap creation shifted a distinct competitive hierarchy to conditions of competitive equivalence. The com- petitive rankings for survival in gaps were opposite those for growth in matrix conditions, with Andropogon being superior in terms of survival and Coreopsis superior in terms of growth. Then, in a factorial design, we teased apart the effects of neighborhood (biomass re- duction, size structure, neighbor identity) and abiotic soil changes (mound formation) as- sociated with soil disturbance on these competitive interactions. Abiotic changes associated with mound formation, rather than neighborhood changes, were responsible for the devel- opment of the survival hierarchy and the loss of the growth hierarchy following gap creation. When hierarchies formed, matrix species were competitively superior to gap species, sup- porting the idea of competitive reduction. However, no one matrix species was consistently competitively superior, and under some conditions species were competitive equivalents, partially supporting the idea of competitive change. When disturbance creates conditions of physical stress, as in this case, trade-offs between growth and survival hierarchies may be important determinants of species response.

The effects of gap creation on competitive interactions: separating changes in overall intensity from relative rankings

A central assumption of disturbance ecology equates gap creation with the reduction of overall competitive intensity. I develop the idea that gap creation, due to changes in addition to biomass removal, could also alter the relative competitive rankings among species. I present a quantitative review using meta‐analysis in which I separate the effect of gap creation from the effect of competition for species characteristic of different disturbance regimes. Twenty‐one studies (with a total of 136 comparisons) directly examined species competitive abilities under gap (disturbed) and matrix (undisturbed) conditions. Overall competitive intensity generally declined in gap conditions, although species characteristic of gap areas responded more strongly to gap creation than did species characteristic of undisturbed matrix areas. Under matrix conditions, matrix species were less affected by competition than gap species, supporting one widespread assumption. However, under gap conditions, matrix and gap species were inhibited to a similar degree by neighbor biomass. These results suggest that gap creation, in addition to decreasing overall competitive intensity, may affect species competitive rankings, possibly due to changes in the environment where the interactions occur.

Annual plant community responses to density of small-scale soil disturbances in the Negev Desert of Israel.

We investigated whether plant diversity and productivity in small-scale soil disturbances, which is known to be higher than in undisturbed soil, decreases as the density of the disturbances increases. We studied this in an experiment with soil diggings (15 cm diameter and 15 cm depth) dug at a range of densities, on a north- and a south-facing slope of a watershed in the central Negev Desert of Israel. The diggings were similar to the commonly occurring pits made by porcupines (Hystrix indica) as they forage for below-ground plant parts. We used four levels of digging density, within the naturally occurring range in the region, represented by a rectangular plot with rows of diggings dug at four distances between diggings. The plots were laid out in a blocked design with three replications on both slopes, with each block containing all four levels of digging density. In the spring of 1992, 1994 and 1995 we measured plant density, species richness and plant productivity in the diggings, and in adjacent equal-sized undisturbed control areas ("soil matrix") and on the mounds made by the removed excess soil. Plant density, species richness and productivity of annual plants were higher in the diggings than in the undisturbed matrix, while these responses were very low on the mounds. Plant density, species richness and productivity in the diggings, but not in the matrix or mounds, decreased as digging density increased. This effect varied slightly with location within a watershed and with annual rainfall. The density of seeds captured in the diggings from outside the digging during the 1995 dispersal season decreased with increasing digging density, but only on one of the slopes. At the highest digging density, plant density and species number in the diggings did not decrease down the slope, as expected if interference between diggings in runoff water capture were the cause of the digging density effect. There was a weak decrease in biomass production in 1994-1995 down the slope. We used a simple mathematical model to estimate whether the distribution of rainfall intensities that occurred during the winter of 1994-1995 could result in differences between digging densities in the amount of water captured by the diggings, and whether this could explain the observed effect of digging density. The model showed that there were four events during which less water was captured by the diggings at high digging densities, except in the topmost row of diggings. Soil moisture measurements, however, showed very little difference between diggings at different digging densities. We explain our findings as the result of the interaction between the properties of the disturbance patch with its surroundings, as the diggings capture resources in the form of runoff water, and seeds moved primarily by wind. The additional resources and seeds captured in diggings increase plant density, species richness and productivity relative to the undisturbed matrix. However, the contrast in plant responses between the disturbed patches and undisturbed soil diminishes at higher digging densities. We explain this as interference among diggings at close proximity. As we did not detect a decrease in plant responses down the slopes, we conclude that interference is due to interception of the wind-driven, non-directional flow of seeds. Interception of the down-slope flow of runoff water by upslope diggings is insufficient to affect plant density, determined at the beginning of the season. Later in the season, runoff interception may become important for biomass production.

Desert Plant Communities in Human‐Made Patches‐‐Implications for Management

We measured productivity and diversity of annual plant communities in human—made pits and mounds (20 ° 30 ° 100 cm) in the Northern Negev of Israel. We differentiated the species according to propagule size, dispersal mode, and geographical distribution in Israel. Our results in 28 experimental units containing a pit, a mound, and a portion of the undisturbed surrounding "matrix" showed that species richness, total plant density, and biomass yield were higher in the pits and mounds than in the matrix. Soil moisture at 0—15 cm depth was higher in the pits, but lower in the mounds relative to the matrix. Species with larger propagules (&gt;5 mm) became more abundant, and those with tinyseeds (&lt;1 mm) became less abundant, in the human—made patches relative to the undisturbed matrix. Wind—dispersed species and those with secondary dispersal by runoff were denser in pits and mounds, while short—distance rain dispersers were more abundant in the matrix. "Edge" species, occurring in the study site at the edge of their geographical distribution in Israel, increased more in density, species richness, and biomass than general "core" species, for which the study site is in the center of their distribution. The annual plant community responded to changes in three environmental factors: (1) microtopographic structure from flat surface to mounds or pits, which function as traps for seeds; (2) soil surface texture from densely packed to loose soil in pits and mounds, which provide suitable sites for larger propagules; (3) soil moisture availability, increasing in the pits but decreasing in the mounds relative to the matrix. The relevance of the study was discussed in relation to (1) combating desertification, (2) sustainable arid land use, and (3) species conservation.

Some effects of scarab beetles in sandy soils of The Netherlands

Samples were taken from sandy soils at six localities in The Netherlands where back-filled burrows of scarab beetles had been observed. Thin sections were prepared and subjected to micromorphometric analysis, using the Quantimet 720. The volume of pores larger than 0.030 mm was up to 38% higher in the back-filled burrows than in the undisturbed matrix, as was the volume of pores larger than 0.195 mm; the latter diameter approximates the critical pore diameter for plant roots in densely packed sandy soils. The suggestion that rooting would be more intensive in the back-filled burrows than in the undisturbed matrix was supported by observations.

Investigation of N-implanted fe single crystals by X-ray line broadening

A long tail in the intensity distribution is observed on the smaller angle side of the (002) Bragg reflection. The asymmetric profiles are decomposed into an asymmetric small peak and a symmetric large one which correspond to the N implanted near surface layer and to the adjacent undisturbed Fe matrix, respectively. The changes after heat treatments up to 550 °C are interpreted in terms of variation of N concentration, N diffusion, and lattice defects. [Russian Text Ignored].