Vesicular Pores Research Articles

Engineered loose nanofiltration membrane for efficient dye/salt separation by starting from poly(ether sulfone) powder modification

Loose nanofiltration (LNF) is increasingly considered as the powerful technique for dye desalination due to its clear advantages at energy efficiency, selectivity and low pollution. But the membrane materials for loose nanofiltration process still suffer from the low permeance, unsatisfactory selectivity, membrane fouling and high cost. Herein, we propose a new three-step route to fabricate efficient poly(ether sulfone) (PES) LNF membrane, which starts from PES powder modification via mutual radiation-induced grafting polymerization and ensues immersion precipitation phase inversion and amination processes. The obtained PES-based LNF membrane possessed a thinner skin layer and an unusual irregular vesicular pore structure in sublayer instead of the finger-like macrovoids of conventional PES membrane. Thus, it achieved larger filtration permeance (35.5 L m–2 h−1 bar−1), high dye rejection (93.7 % to Congo Red) but low salt rejection (2.9 % to NaCl) during the filtration process of Congo red-containing saline water. It also showed excellent separation stability at high operation pressure and tolerance to acidic, alkaline and chlorine-oxidative conditions. Therefore, such a three-step strategy could endow the PES membrane with both loose and thinner skin layer in a reliable and scalable way, enlightening the development of high-performance LNF membrane for wastewater treatment and resource recovery.

Microbial activity and temperature change affect growth of vesicular pores

Vesicular pores are observed in many different soil-forming environments. They can also be re-created in the lab through exposure to cyclic wetting and drying. However, little is known about the physical, chemical, and biological mechanisms involved in vesicular pore formation. This study was conducted to test the hypotheses that 1) microbial activity and 2) thermal expansion are important drivers of vesicular pore growth. These hypotheses were tested through laboratory experiments employing treatments to manipulate the biota (i.e., sterile, non-sterile, and glucose-amended treatments) and temperature change (i.e., wetting at 7 °C, 23 °C, and 40 °C before drying at 40 °C). The growth of vesicular pores, as well as vughs and planar voids, was compared among the treatments using bulk densities measured by three-dimensional laser scanning and pore analysis by computed tomography. Pore growth was found to be significantly greater in sterile soils compared to non-sterile and glucose-amended soils. Comparison among the temperature treatments showed the greatest pore growth in the samples that experienced the greatest temperature change between wetting and drying (7 °C to 40 °C). These results support the thermal expansion hypothesis of vesicular pore development, but contradict the microbial activity hypothesis.

Investigation on pore structure, fluid mobility and water huff-n-puff oil recovery of tight volcanic oil reservoir

The pore structure of tight volcanic oil reservoirs is very complex and the permeability is extremely low. The oil recovery effect of traditional water-driven and gas-driven development is not ideal. In this paper, we first analyzed the pore structure characteristics and fluid movability characteristics of tight volcanic rocks. Then, the feasibility of water huff-n-puff in tight volcanic rocks was analyzed. Finally, we investigated the oil recovery characteristics, pore motility characteristics, and ORM of water huff-n-puff in tight volcanic rocks by using a high temperature and ultra-high pressure water huff-n-puff physical simulation experimental device under NMR monitoring. The study shows that the mineral composition of tight volcanic rocks is relatively simple, but the pore structure is very complex. The pores are mainly amygdule pores, and contain some vesicular pores and matrix pores. The fractures include structural fractures, dissolution fractures, and shrinkage fractures. Fractures are of great significance for communicating relatively independent pores and improving the seepage ability of fluids in tight volcanic rocks. The fluid movable saturation of tight volcanic rocks is 32.93%–83.75%, and the minimum movable pore radius is 0.0178 μm. The seepage capacity of large pores (r > 0.1 μm) is 2.19–7.75 times that of middle pores (0.001 μm < r < 0.1 μm). The oil recovery efficiency (the ratio of the volume of recovered oil to the volume of injected water) of the first two cycles of water huff-n-puff of tight volcanic rocks exceeds 20%, which is high-efficiency oil recovery period. However, with the increasing huff and puff cycles, the recovery factor and oil change rate both decrease rapidly. After five cycles of water huff-n-puff, the recovery factor of tight volcanic rocks increases by 29.13%. For the selected experimental core, middle pores are the main oil-producing pores, and their contribution rates in natural energy depletion and five cycles of water huff-n-puff are 59.665% and 78.173%. In five cycles of water huff-n-puff, the contribution rates of elastic displacement are 96.491%, 93.846%, 86.667%, 64.706%, and 55.556%, and the effect of imbibition displacement is relatively small. Increasing the water injection pressure is beneficial to water huff-n-puff oil recovery of tight volcanic rocks. The research can provide a good theoretical basis for the efficient development of tight volcanic oil reservoirs.

Key Factor Study for Amphiphilic Block Copolymer‐Templated Mesoporous SnO2 Thin Film Synthesis: Influence of Solvent and Catalyst

AbstractAs a crucial material in the field of energy storage, SnO2 thin films are widely applied in daily life and have been in the focus of scientific research. Compared to the planar counterpart, mesoporous SnO2 thin films with high specific surface area possess more attractive physical and chemical properties. In the present work, a novel amphiphilic block copolymer‐assisted sol–gel chemistry is utilized for the synthesis of porous tin oxide (SnO2). Two key factors for the sol–gel stock solution preparation, the solvent category and the catalyst content, are systematically varied to tune the thin film morphologies. A calcination process is performed to remove the polymer template at 500 °C in ambient conditions. The surface morphology and the buried inner structure are probed with scanning electron microscope and grazing‐incidence small‐angle X‐ray scattering. Crystallinity is characterized by X‐ray diffraction. The multi‐dimensional characterization results suggest that cassiterite SnO2 with spherical, cylindrical, and vesicular pore structures are obtained. The variation of the film morphology is governed by the preferential affinity of the utilized solvent mixture and the hydrogen bond interaction between the employed cycloether and H2O molecules in the solution.

Formation of Vesicular Pores in Aggregates from the Eluvial Horizon of Albic Glossic Retisol during Freeze-Thaw Cycles

In this article, we discuss the contribution of capillary wetting and multiple freezing and thawing to the formation and evolution of vesicular micro– and mesoporosity in an aggregate of 3 mm in diameter from the eluvial horizon of soddy–podzolic soil (Albic Glossic Retisol (Loamic, Cutanic)). The main visible changes occur during capillary wetting and the first four cycles of freezing and thawing. Capillary wetting of the air-dry aggregate initiates the formation of vesicular micropores in the soil mass. The first freezing fixates the newly formed vesicles and contributes to the development of microschlieren in the aggregate. The first thawing causes the isolation and growth of individual vesicular pores. In the subsequent three freeze–thaw cycles, freezing fixates the vesicular pore space pattern, whereas thawing promotes the coalescence of small vesicular pores into larger vesicular pores. During the fifth and next cycles, many large vesicular pores leave the deformed aggregates aggregate, so that horizontally oriented cryogenic microschlieren tend to predominate in the frozen aggregate after 10–20 freeze–thaw cycles.

Disturbance impacts on porosity and hydraulic properties of vesicular horizons

AbstractRapid formation of vesicular pores has been observed following disturbance of vesicular (V) horizons. This study investigates the post‐disturbance recovery of V horizons and the impact on hydraulic properties. At nine study sites, infiltration rates were measured using a tension disk infiltrometer, and intact samples were collected for analysis using high‐resolution x‐ray computed tomography (CT). The V horizon material was then removed, crushed, replaced, and left to recover for 1 yr before repeating the infiltration measurement and CT analysis. Some recovery of vesicular and vugh porosity was observed at all of the study sites. However, the V horizons formed in the first year after disturbance were thinner, with smaller pores, and with a reduction in vesicle and vugh porosity from an average of 2.9% before disturbance to 0.4% after disturbance. The saturated hydraulic conductivity of the V horizons was also significantly lowered, from an average of 20 cm d−1 prior to disturbance to 6.6 cm d−1 at 1 yr after disturbance. Vesicle and vugh porosity formed 1 yr after disturbance was positively correlated with predisturbance vesicle and vugh porosity (R2 = .57; P = 0.02) and sand percentage (R2 = .51; P = .03) and negatively correlated with silt percentage (R2 = .51; P = .03). No relationship was observed between post‐disturbance formation of vesicle and vugh porosity and precipitation events during the recovery period, clay percentage, CaCO3 percentage, or saline‐sodic classification. V horizons show incipient development at 1 yr after disturbance, but porosity and hydraulic properties are significantly altered from their undisturbed state.

Differential Release of Exocytosis Marker Dyes Indicates Stimulation-Dependent Regulation of Synaptic Activity.

There is a general consensus that synaptic vesicular release by a full collapse process is the primary machinery of synaptic transmission. However, competing view suggests that synaptic vesicular release operates via a kiss-and-run mechanism. By monitoring the release dynamics of a synaptic vesicular marker, FM1-43 from individual synapses in hippocampal neurons, we found evidence that the release of synaptic vesicle was delayed by several seconds after the start of field stimulation. This phenomenon was associated with modified opening kinetics of fusion pores. Detailed analysis revealed that some synapses were completely inactive for a few seconds after stimulation, despite immediate calcium influx. This delay in vesicular release was modulated by various stimulation protocols and different frequencies, indicating an activity-dependent regulation mechanism for neurotransmitter exocytosis. Staurosporine, a drug known to induce “kiss-and-run” exocytosis, increased the proportion of delayed synapses as well as the delay duration, while fluoxetine acted contrarily. Besides being a serotonin reuptake inhibitor, it directly enhanced vesicle mobilization and reduced synaptic fatigue. Exocytosis was never delayed, when it was monitored with pH-sensitive probes, synaptopHlourin and αSyt-CypHerE5 antibody, indicating an instantaneous formation of a fusion pore that allowed rapid equilibration of vesicular lumenal pH but prevented FM1-43 release because of its slow dissociation from the inner vesicular membrane. Our observations suggest that synapses operate via a sequential “kiss-and-run” and “full-collapse” exocytosis mechanism. The initially narrow vesicular pore allows the equilibration of intravesicular pH which then progresses toward full fusion, causing FM1-43 release.

El papel de los hongos en la conservación de Andosols: estudio de caso en Tlaxcala, México

Tlaxcala state, Mexico, show environmental problems related to soil erosion; however, in some areas of Andosols, with pine forests and even in agricultural areas, it has been observed that their degradation is minimal. The abundant presence of mycelium even in subsurface horizons can be the reason why soils are conserved. The objectives of this study were to characterize the edaphic properties in different geo-morphological positions, to identify the species of arbuscular mycorrhizal fungi (AMF) and to determine the relationship of the mycelium with aggregates and elementary particles in a Vitric Andosols of Calpulalpan, Tlaxcala, Mexico. The results showed that soils have different sequences and thicknesses of ashes and lapillis pomaceous and have moderate to high fertility. The crumbly structure dominated in upper horizons and simple granular in sub-horizons. The horizons showed high retention of humidity and permeability facilitating mycelial development and formation of AMF spores up to 120 cm deep. Ten species of AMF were recorded and the most abundant was Funneliformis mosseae. The micro-morphological analysis showed different relationships between the mycelium, horizon and soil particles, with organic waste (horizon O), with macro and micro aggregates (horizons A and B), with allophane and imogolite (horizons B) and lapillis (horizon C). The fungal mycelium forms networks throughout the soil, and in the lapillis it inserts the pumice particles (like a rosary) through the tubular vesicular pores, which provides stability to the Andosols and prevents their degradation.

Extracellular ATP Regulates the Vesicular Pore Opening in Chromaffin Cells and Increases the Fraction Released During Individual Exocytosis Events.

Adenosine triphosphate (ATP) is the main energy source for cellular metabolism. Besides that, ATP is a neurotransmitter and a cotransmitter that acts on purinergic receptors present either pre- or postsynaptically. Almost all types of secretory vesicles from any neuron or animal species contain high concentrations of ATP, being an essential factor in the accumulation of neurotransmitters. In this work, we studied the effects of ATP on quantum catecholamine release and vesicular storage in chromaffin cells. We combined three electrochemical methods: conventional amperometry with intracellular vesicle impact electrochemical cytometry and vesicle impact electrochemical cytometry. We found that extracellular ATP increased the released quantal fraction of catecholamine but not its vesicular content. Studying the dynamics of exocytosis events in ATP treated cells showed that ATP affects the release fusion pore. To elucidate the mechanisms of the observed ATP effects, cells and vesicles were pharmacologically treated with suramin (a purinergic blocker) and ARL-67156 (an antagonist of ecto-ATPases). The data indicate that the catecholamine content of vesicles increased compared to control after these drugs. Our data suggest that ATP acting on purinergic receptors increases the quantum releasable size through an increased fusion pore opening and that ARL-67156 and/or suramin protect the vesicle from neurotransmitter leakage by functioning as competitive inhibitors to ATP.

The Impact of Multiple Freeze–Thaw Cycles on the Microstructure of Aggregates from a Soddy-Podzolic Soil: A Microtomographic Analysis

With the help of computed X-ray microtomography with a resolution of 2.75 μm, changes in the microstructure and pore space of aggregates of 3 mm in diameter from the virgin soddy-podzolic soil (Glossic Retisol (Loamic)) in the air-dry, capillary-moistened, and frozen states after five freeze–thaw cycles were studied in a laboratory experiment. The freezing of the samples was performed at their capillary moistening. It was shown that capillary moistening of initially air-dry samples from the humus (AY), eluvial (EL), and illuvial (BT1) horizons at room temperature resulted in the development of the platy, fine vesicular, and angular blocky microstructure, respectively. The total volume of tomographically visible pores >10 μm increased by 1.3, 2.2, and 3.4 times, respectively. After freeze–thaw cycles, frozen aggregates partly preserved the structural arrangement formed during the capillary moistening. At the same time, in the frozen aggregate from the AY horizon, the total tomographic porosity decreased to the initial level of the air-dry soil. In the frozen aggregate from the EL horizon, large vesicular pores were formed, owing to which the total pore volume retained its increased values. The resistance of aggregate shape to the action of freeze–thaw cycles differed. The aggregate from the EL horizon completely lost its original configuration by the end of the experiment. The aggregate from the AY horizon displayed definite features of sagging after five freeze–thaw cycles, whereas the aggregate from the BT1 horizon preserved its original configuration.

Microtomographic analysis of pore space in a virgin soddy-podzolic soil

The method of X-ray microtomography was applied to study pore space of a virgin soddy-podzolic soil at the natural soil water content. The morphometric parameters of the pores of more than 100 μm in diameter were determined in the vertically oriented undisturbed soil monoliths (d = 3 cm, h = 3–4 cm) from the genetic horizons of the most differentiated part of the soil profile (the AY, AEL, EL, BEL, BT1, and BТ2 horizons). A tendency for the horizontal orientation of these pores was found in all the horizons, except for the humus (AY) horizon. Isolated vesicular pores of different sizes were abundant in the eluvial part of the profile. Numerous recent and relict phytogenic channels were found in the intraped mass of the BT2 horizon. Differently directed interfaces of structural units in the soil horizons were visualized. Cluster analysis was applied to estimate differences between the genetic horizons with respect to their textures, aggregate sizes, and shapes of pores as seen in vertical two-dimensional X-ray images.

From Las Vegas to Long Beach: Desert Pedology, Land Use, and Wild Lands Tour

On 30 Oct.–1 Nov. 2014, the Victorville MLRA Soil Survey Office; Dr. Bob Graham (University of California–Riverside, UCR), and Dr. Brenda Buck (University of Nevada–Las Vegas, UNLV) hosted the Desert Pedology, Land Use, and Wild Lands—Las Vegas to Long Beach two-day tour. The tour was planned and executed by Leon Lato and the rest of the Victorville MLRA Soil Survey, Region 8 team with a special thanks to Carrie Ann Houdeshell who originally initiated the effort before she transferred to her modelling position in Region 2. From Las Vegas, NV to the outskirts of the Los Angeles Basin, CA, there is a wide range of desert landscape, remote wilderness, unique vegetation, and soil formation. This area represents isolation and preservation and, at the same time, promises for the future of open space for renewable energy production, food and fiber production, watershed renovation, and alternative uses for new minerals for green infrastructure and modern technology. The tour started in Las Vegas at the University of Nevada with a lecture and lab tour from NCSS cooperator Dr. Brenda Buck. Her lecture on “Naturally Occurring Asbestos: Potential for Human Exposure, Southern Nevada, USA” was illuminating and a good start to understanding the issues of dust in the Mojave Desert and the southwestern U.S. to humans and the difficulties of studying the subject in an urbanizing environment. The group travelled on to California to the Mojave National Preserve (MNP). Dr. Mandy Williams of UNLV and Dustin Detweiler, NRCS ecological site specialist, started the field discussions with examples of biocrusts, ecological site descriptions, and the function of dust in these systems. Dr. Daniel Hirmas, Kansas University, explained his Ph.D. UCR thesis of Eolian deposits on mountains, and Leon Lato, NRCS soil survey project leader, Mojave National Preserve, led the discussion of the playa soil of Soda Dry Lake. The group stayed at the Desert Studies Center in Zzyzx, CA (named by Dr. Springer, owner of this famous 1930s health spa as the “last” word in health). On the second day, the group visited the basalt flows in the Cima volcanic field with Dr. Yvonne Katzenstein, which illustrated the potential of 1 to 3 m of dust (eolian fines) inflating the landscape over measured geologic time. A highlight of the tour was the taxonomic discussion and illustration of the new master V horizon by Dr. Robert Graham, UCR. This site shows how the V horizon developed from eolian deposits under a desert pavement surface. The vesicular pores and platy structure of the silt loam surface (V horizon) contrasts strongly with the gravelly-sandy material below. The final stop was at the eastern side of the Kelso Dunes with an explanation by Dr. Katherine Kendrick, USGS, on desert dust and dune processes. Pre-meeting SSSA Pedology Tour 2014 group picture on the eastern edge of the Kelso Dune field in MNP in an area stabilized by big galleta grass. Playa soil on Soda Dry Lake looking south at the Desert Studies Center in Zzyzx, CA—coarse-loamy, mixed, superactive, hyperthermic Oxyaquic Udorthents. The tour brought together students, soil scientists, and soil taxonomists from China, Iraq, Syria, India, Europe, Canada, Australia, Africa, and throughout the U.S. Those who attended came away with a clearer understanding of the importance of the V master horizon and dust in desert environments as well as congenial memories of NRCS's work in the region. They enjoyed the spectacular weather including some overnight rain and relatively light desert breezes for the trip. Tour participants scrutinizing samples of the V horizon in MNP. Desert pavement with a V horizon in MNP—sandy-skeletal, mixed, thermic Typic Haplocalcids.

Fabric of topsoil horizons in aridic soils of Central Asia .

Two surface microhorizons – vesicular and platy – were found to be typical of the fabric of topsoil horizons in gravely loamy soils located along an arid/continental climatic gradient in the Subboreal zone of Central Asia (from southern Russia to Uzbekistan, Kazakhstan, and Mongolia). Their genesis is related to active vesiculation (for vesicular А&lt;sub&gt;1&lt;/sub&gt; microhorizon) and cryogenesis (for platy А&lt;sub&gt;2&lt;/sub&gt; microhorizon) against a background of high clay mobility and/or eolian accumulation of fine material. New mechanisms responsible for the formation of vesicular pores are suggested: (a) the leaching of dense complete crystal infillings (moldic voids) and (b) the development of biogenic capsules typical of iron bacteria that were diagnosed by the microbiological method of fouling Agar-covered glasses under natural conditions. In a series of studied soils, Yermic Regosols are characterized by additional specific microfeatures: (1) iron depletion from the material around the pores and formation of iron concentrations in the intrapedal mass owing to biogenic mobilization of iron with participation of sulfate- and iron-reducing bacteria and (2) the accumulation of organic matter (residues of microbial cells) in the vesicular pores.

Soil microstructure as an under-explored feature of biological soil crust hydrological properties: case study from the NW Negev Desert

Biological soil crusts (BSCs) can play an important role in hydrological cycles, especially in dryland ecosystems where the availability of water is limited. Many factors influence the hydrological behavior of BSCs, one of which is the microstructure. In order to describe the influence of the soil microstructure of BSCs on water redistribution, we investigated the change of the pore system of three different successional stages of BSCs, as well as their respective subcrusts in the NW Negev desert, Israel, using 2-dimensional thin sections, as well as non-invasive X-ray 3D computed microtomography (XCMT) and mercury intrusion porosimetry. Our results show that the pore system undergoes significant changes during crust succession. Both the total porosity, as well as the pore sizes significantly increased from cyano- to lichen- to mosscrust and the pore geometry changed from tortuous to straight pore shapes. We introduce two new mechanisms that contribute to the hydrological properties of the BSCs in the NW Negev that impede infiltration: (i) vesicular pores and (ii) a discontinuous pore system with capillary barrier effects, caused by a rapid change of grain sizes due to sand burial. Since both of these mechanisms are present mostly in early stage cyanobacterial crusts and their abundance decreases strongly with succession, it is very likely that they influence BSC hydrology to different extents in the various crust types and that they are partly responsible for differences in runoff in the NW Negev.

The pore space arrangement in podzolic horizons of loamy soils (analysis of 2D AND 3D images)

A comparative analysis of 2D (in thin sections) and 3D (X-ray CT) images allowed obtaining new data about the pore space arrangement in the EL horizon of soddy podzolic soils. The 3D images of the soil mass and the pore space have been made by reconstruction via computer using a great number of 2D shady X-ray projections. It is shown that the EL horizon reveals not only horizontal fissured pores between platy aggregates but also many isolated vesicular pores of unknown genesis. As dinstinct from the podzolic horizon such pores are singly met in the soil-forming mantle loam (C horizon). The major pores with rounded edges are represented by recent and relic root holes. The obtained data serve as an additional information on the podzolic horizon configuration in soddy podzolic soils on the whole and the pore space in these horizons in particular. Thanks to this study iy is reasonable to conclude that the information on genetic differences in the configuration of pedogenic and lithogenic horizons of the soddy podzolic soils is expanded.

A novel approach to generate a recombinant toxoid vaccine against Clostridium difficile

The Clostridium difficile toxins A and B are primarily responsible for symptoms of C. difficile associated disease and are prime targets for vaccine development. We describe a plasmid-based system for the production of genetically modified toxins in a non-sporulating strain of C. difficile that lacks the toxin genes tcdA and tcdB. TcdA and TcdB mutations targeting established glucosyltransferase cytotoxicity determinants were introduced into recombinant plasmids and episomally expressed toxin mutants purified from C. difficile transformants. TcdA and TcdB mutants lacking glucosyltransferase and autoproteolytic processing activities were ~10 000-fold less toxic to cultured human IMR-90 cells than corresponding recombinant or native toxins. However, both mutants retained residual cytotoxicity that could be prevented by preincubating the antigens with specific antibodies or by formalin treatment. Such non-toxic formalin-treated mutant antigens were immunogenic and protective in a hamster model of infection. The remaining toxicity of untreated TcdA and TcdB mutant antigens was associated with cellular swelling, a phenotype consistent with pore-induced membrane leakage. TcdB substitution mutations previously shown to block vesicular pore formation and toxin translocation substantially reduced residual toxicity. We discuss the implications of these results for the development of a C. difficile toxoid vaccine.

Morphology of physical soil crusts and infiltration patterns in an artificial catchment

Hydraulic properties of the soil surface control the partitioning of rainfall between infiltration and runoff. For agricultural soils in humid climate regions, physical soil crusts have mostly been reported to reduce water infiltration. For initial soils developing in such climate on unstructured sediments without organic carbon, effects of soil crusting and slaking on infiltration was largely unknown. The objective was to compare initial soil and porous system formation with infiltration from three locations in a constructed hydrological catchment that has been left to undirected ecological succession for three years. We expected to find characteristic, mainly textural, effects of physical soil crusts during this initial stage of soil development. The three-dimensional (3D) micro-morphology was described using the X-ray computed tomography (CT); two-dimensional (2D) infiltration patterns were obtained from drip infiltration experiments using time-resolved neutron radiography (NT). Selected samples from three locations represent major sediment types of the catchment. The CT data indicated structural crusts on soil consisting of sandy to loamy sediments and depositional crusts on more sandy sediments. A combination of these two types developed at locations with silt to fine sand sediments; probably as a result of aeolian deposition on a structural crust. Moreover, isolated vesicle-shaped pores mostly reported from soils in arid environments were observed in most samples. The 2D infiltration patterns reflected the structural alteration by crusts only in samples containing silt and fine sand. Infiltrating water tended to pond within the aeolian deposits above the underlying structural crust. For all other samples, 2D infiltration pattern were relatively uniform; only negligibly small effect of structural crusts and vesicular pores on infiltration and redistribution could be observed in NR experiments although field measured infiltration rates were different. The relatively small differences in moisture patterns observed using NT suggest that the texture-related differences in physical soil crusts indicated by pore structure images using CT had only little effects on infiltration. The study improved understanding soil structure and water distribution relations in a hydrological catchment during initial ecosystem development.

Microbiological and micromorphological characteristics of extremely arid desert soils in the Ili Depression (Kazakhstan)

The high biological diversity and the high activity of microorganisms were determined in the extremely arid desert soils developing under very sparse vegetation during the period of rare rains. Green and diatomaceous algae, dinoflagellates, cyanobacteria, and iron bacteria were diagnosed in the edaphon. These microorganisms affect the geochemical processes in the soils, including the biogenic transformation of rock minerals. Amorphous compounds of Fe3+ and Mn3+ are concentrated around the cells of iron bacteria and produce specific iron and iron-manganic pedofeatures. The specific humus-accumulative process is also developed owing to the mineralization of the microbial biomass with the formation of organomineral coagulates in the zones of contact of the intraped mass with rock debris covered by iron films and in the biogenic films on the walls of vesicular pores.

Effects of Ground‐Dwelling Beetle Burrows on Infiltration Patterns and Pore Structure of Initial Soil Surfaces

By modifying the soil structure, flora and fauna play a major role in controlling water infiltration and erosion. Little is known, however, about local feedback effects during the initial stage of soil development. Initial soil formation was studied in an artificial catchment where coarse‐textured, sandy sediments were left to undirected succession. In a patchy moss‐covered area, the surface was colonized by larvae of the ground‐dwelling beetle Cylindera arenaria viennensis [Schrank, 1781], as indicated by millimeter‐sized cylindrical burrows. Our objective was to study the effects of both moss vegetation and beetle larvae on pore structure and infiltration. The pore structure of sparsely and densely moss‐vegetated and unvegetated samples containing a single burrow was characterized by x‐ray computed tomography (CT). Flow patterns of infiltration experiments were visualized using neutron radiography (NR). The micro‐CT scans revealed a variety of more unstable pore systems in the bare soil, locally compacted regions in the moss‐covered samples, and isolated vesicular pores similar to those reported for desert soils. The NR series showed water flow around the cylindrical burrow under initially moist conditions and pronounced preferential flow within the burrow under initially dry soil conditions. Water‐repellent regions in the initially dry sample explained pressure buildup before gravity‐driven flow in the burrow started. The moss cover seemed to stabilize the surface soil, visible in the absence of a depositional sediment layer. The results suggest that moss vegetation and ground beetle burrowing activity control initial soil development by modifying pore structure and water infiltration.

CON: Patients at High Risk for Ovarian Cancer Should Not Undergo Routine Screening

Vesicular pores are observed in many different soil-forming environments. They can also be re-created in the lab through exposure to cyclic wetting and drying. However, little is known about the physical, chemical, and biological mechanisms involved in vesicular pore formation. This study was conducted to test the hypotheses that 1) microbial activity and 2) thermal expansion are important drivers of vesicular pore growth. These hypotheses were tested through laboratory experiments employing treatments to manipulate the biota (i.e., sterile, non-sterile, and glucose-amended treatments) and temperature change (i.e., wetting at 7 °C, 23 °C, and 40 °C before drying at 40 °C). The growth of vesicular pores, as well as vughs and planar voids, was compared among the treatments using bulk densities measured by three-dimensional laser scanning and pore analysis by computed tomography. Pore growth was found to be significantly greater in sterile soils compared to non-sterile and glucose-amended soils. Comparison among the temperature treatments showed the greatest pore growth in the samples that experienced the greatest temperature change between wetting and drying (7 °C to 40 °C). These results support the thermal expansion hypothesis of vesicular pore development, but contradict the microbial activity hypothesis.