Knowing little about how porosity and permeability are distributed at depth, we commonly develop models of groundwater by treating the subsurface as a homogeneous black box even though porosity and ...permeability vary with depth. One reason for this depth variation is that infiltrating meteoric water reacts with minerals to affect porosity in localized zones called reaction fronts. We are beginning to learn to map and model these fronts beneath headwater catchments and show how they are distributed. The subsurface landscapes defined by these fronts lie subparallel to the soil‐air interface but with lower relief. They can be situated above, below, or at the water table. These subsurface landscapes of reaction are important because porosity developed from weathering can control subsurface water storage. In addition, porosity often changes at the weathering fronts, and when this affects permeability significantly, the front can act like a valve that re‐orients water flowing through the subsurface. We explore controls on the positions of reaction fronts under headwater landscapes by accounting for the timescales of erosion, chemical equilibration, and solute transport. One strong control on the landscape of subsurface reaction is the land surface geometry, which is in turn a function of the erosion rate. In addition, the reaction fronts, like the water table, are strongly affected by the lithology and water infiltration rate. We hypothesize that relationships among the land surface, reaction fronts, and the water table are controlled by feedbacks that can push landscapes towards an ‘ideal hill’. In this steady state, reaction‐front valves partition water volumes into shallow and deep flowpaths. These flows dissolve low‐ and high‐solubility minerals, respectively, allowing their reaction fronts to advance at the erosion rate. This conceptualization could inform better models of subsurface porosity and permeability, replacing the black box.
The subsurface is often treated as a black box in hydrologic models. But we are beginning to understand interactions among the land surface, weathering fronts, and the water table that push landscapes toward steady‐state morphologies. Weathering fronts that change the porosity act like valves that partition water into shallow‐ and deep‐flowing fractions. These flows then allow fronts for low‐ and high‐solubility minerals, respectively, to advance at the erosion rate. This conceptualization could help to replace the black box when modelling headwater catchments.
The number, phenotypic composition, and functional properties of macrophages in the liver of Wistar rats change depending on the stages of fibrosis induced by thioacetamide. In the sinusoidal ...capillaries of the liver of control rats, CD68
+
wing-shaped cells were mainly detected. The number of CD68
+
cells at the stages of fibrosis before the process of its transformation into cirrhosis was 2-fold higher (
p
=0.0000) than in the control. At later terms of the experiment, no significant differences were found. Immunohistochemical method revealed two morphologically different groups of CD68
+
cells differing in shape and localization. At all stages of the experiment, round and elongated CD206
+
cells of were detected in the sinusoidal capillaries. At the stage of cirrhosis (13 weeks), the number of CD206
+
cells was higher than during the third week of the experiment by 3.21 times (
p
=0.0000). Later, a decrease in the number of CD206
+
cells was observed. At the same time, in the portal zones and connective tissue septa around the false hepatic lobules, round CX3CR1
+
cells were noted. By the end of the experiment (17 weeks), their number exceeded that on the third week of the experiment by 5.66 times (
p
=0.0000).
The analytical two-chain Frenkel-Kontorova model is used to describe domain wall networks in bilayer graphene upon biaxial stretching of one of the layers. We show that the ...commensurate-incommensurate phase transition leading to formation of a regular triangular domain wall network at the relative biaxial elongation of 3.0×10^{-3} is followed by the transition to another incommensurate phase with a striped network at the elongation of 3.7×10^{-3}. The reentrant transition to the phase with a triangular domain wall network is predicted for the elongation ∼10^{-2}.
Cytokinin is an important regulator of symbiotic nodule development. Recently, KNOTTED1-LIKE HOMEOBOX 3 transcription factor (TF) was shown to regulate symbiotic nodule development possibly via the ...activation of cytokinin biosynthesis genes. However, the direct interaction between the KNOX3 TF and its target genes has not been investigated up to date. Here, using EMSA analysis and SPR-based assay, we found that MtKNOX3 homeodomain directly binds to the regulatory sequences of the MtLOG1, MtLOG2, and MtIPT3 genes involved in nodulation in Medicago truncatula. Moreover, we showed that MtLOG2 and MtIPT3 expression patterns partially overlap with MtKNOX3 expression in developing nodules as it was shown by promoter:GUS analysis. Our data suggest that MtKNOX3 TF may directly activate the MtLOG1, MtLOG2, and MtIPT3 genes during nodulation thereby increasing cytokinin biosynthesis in developing nodules.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The discovery of ammonia-oxidizing archaea (AOA) of the phylum Thaumarchaeota and the high abundance of archaeal ammonia monooxygenase subunit A encoding gene sequences in many environments have ...extended our perception of nitrifying microbial communities. Moreover, AOA are the only aerobic ammonia oxidizers known to be active in geothermal environments. Molecular data indicate that in many globally distributed terrestrial high-temperature habits a thaumarchaeotal lineage within the Nitrosopumilus cluster (also called "marine" group I.1a) thrives, but these microbes have neither been isolated from these systems nor functionally characterized in situ yet. In this study, we report on the enrichment and genomic characterization of a representative of this lineage from a thermal spring in Kamchatka. This thaumarchaeote, provisionally classified as "Candidatus Nitrosotenuis uzonensis", is a moderately thermophilic, non-halophilic, chemolithoautotrophic ammonia oxidizer. The nearly complete genome sequence (assembled into a single scaffold) of this AOA confirmed the presence of the typical thaumarchaeotal pathways for ammonia oxidation and carbon fixation, and indicated its ability to produce coenzyme F420 and to chemotactically react to its environment. Interestingly, like members of the genus Nitrosoarchaeum, "Candidatus N. uzonensis" also possesses a putative artubulin-encoding gene. Genome comparisons to related AOA with available genome sequences confirmed that the newly cultured AOA has an average nucleotide identity far below the species threshold and revealed a substantial degree of genomic plasticity with unique genomic regions in "Ca. N. uzonensis", which potentially include genetic determinants of ecological niche differentiation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The presence of defects in graphene has an essential influence on its physical and chemical properties. The formation, behaviour and healing of defects are determined by energetic characteristics of ...atomic scale structure changes. In this article, we review recent studies devoted to atomic scale reactions during thermally activated and irradiation-induced processes in graphene. The formation energies of vacancies, adatoms and topological defects are discussed. Defect formation, healing and migration are quantified in terms of activation energies (barriers) for thermally activated processes and by threshold energies for processes occurring under electron irradiation. The energetics of defects in the graphene interior and at the edge is analysed. The effects of applied strain and a close proximity of the edge on the energetics of atomic scale reactions are overviewed. Particular attention is given to problems where further studies are required.
An overview of theoretical and experimental studies concerned with energetics of atomic scale structure changes in graphene, including thermally activated and electron irradiation-induced processes.
PDF
