Formation of Microaggregates and organo-mineral composite building units: Novel pathways in the soil-parent rock continuum

2020 ◽  
Author(s):  
Kai Uwe Totsche
Keyword(s):  
Transition Zone ◽  
Solid Phase ◽  
Early Stage ◽  
Pore Space ◽  
Spatial Arrangement ◽  
Structural Features ◽  
Parent Rock ◽  
Permeable Media ◽  
Submicron Scale ◽  
Surface Alteration

<p><strong>Formation of Microaggregates and organo-mineral composite building units: Novel pathways in the soil-parent rock continuum</strong></p><p><strong> </strong></p><p><strong>Summary</strong></p><p> </p><p>Microaggregates and organo-mineral composite building seem to be unique structural features of natural permeable media like soils, rocks and aquifers. Thee develop in response to various aggregation processes and mechanisms that result in a non-random spatial arrangement of the solid phase already at the submicron scale. Soil microaggregates are defined as compound structures smaller <0.25mm, comprising the colloidal-sized and nanoparticulate composite building units and the organo-mineral composites (Totsche et al. 2018). Noteworthy, microaggregates, may be present as suspended or colloidally-dispersed components of the mobile phase. As such, they are prone to transport with the seepage and may affect the surface and pore-space properties. Surface alteration by interactions of seepage components with immobile surfaces is likely an important, yet essentially unexplored pathway triggering formation of microaggregates in the soil-parent rock continuum. In matured soils, the commonly found associations of clays with other, often poorly crystallized but highly reactive minerals and organic matter is the consequence of nucleation in the chemically heterogeneous soil suspension. Both pathways coexist and can be studied in the soil-parent-rock transition zone were weathering and formation/alteration of secondary mineral phases are still in the early stage<strong>. </strong>The stability of microaggregates and their interactions are dependent on wetting-drying and in turn by hydration-dehydration cycles. Such moisture-related dynamics regularly take place in soils of the temperate regions even down to the soil-parent-rock transition zone and suggests that the hydraulic and osmotic stress and their history results in attachment, detachment, translocation and accumulation. The presentation will We focus on two so far vastly ignored formation pathways of microaggregates and composite building units, i.e., the “geochemical inheritance” and “heteroaggregation from suspension”, thereby considering the role of dynamic relocation of composite building units and microaggregate forming materials from upstream compartments.</p><p> </p><p>Totsche K.U., Amelung W., Gerzabek M.H., Guggenberger G., Klumpp E., Knief C., Lehndorff E., Mikutta R., Peth S., Prechtel A., Ray N., Kögel-Knabner I. (2018) Microaggregates in soils. Journal of Plant Nutrition and Soil Science 181(1), 104-136.</p>

Synthesis of four new V1 antagonists of arginine-vasopressin (AVP) containing new thioacids at position 1 and their vasoconstrictor activity towards isolated mesenteric arterial vessels of rats

1991 ◽  
Vol 56 (2) ◽  
pp. 491-498 ◽  
Author(s):  
Bernard Lammek ◽  
Izabela Derdowska ◽  
Tomasz M. Wierzba ◽  
Witold Juzwa
Keyword(s):  
Peptide Synthesis ◽  
Arginine Vasopressin ◽  
Solid Phase ◽  
Structural Features ◽  
Phase Method ◽  
Competitive Antagonist ◽  
Vasoconstrictor Effect ◽  
Solid Phase Method

In an attempt to determine some of the structural features in position 1 that account for V1 antagonism, four new analogues of arginine-vasopressin were synthesized and the effect of the modifications on the vasoconstrictor activity was checked using isolated mesenteric arterial vessels of rats. The protected precursors required for these analogues were synthesized by a solid phase method of peptide synthesis. One of the reported analogues, namely [1-(4-mercapto-4-tetrahydrothiopyraneacetic acid)., 2-O-methyltyrosine, 8-arginine]vasopressin appears to be a potent competitive antagonist of the vasoconstrictor effect by AVP.

scholarly journals Synthesis of short-range ordered aluminosilicates at ambient conditions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Katharina R. Lenhardt ◽  
Hergen Breitzke ◽  
Gerd Buntkowsky ◽  
Erik Reimhult ◽  
Max Willinger ◽  
...  
Keyword(s):  
Short Range ◽  
Spatial Arrangement ◽  
Aluminium Chloride ◽  
Ambient Conditions ◽  
Soils And Sediments ◽  
Submicron Scale ◽  
Mineral Structure ◽  
Temperature And Pressure ◽  
Physical And Chemical ◽  
Microscopic Techniques

AbstractWe report here on structure-related aggregation effects of short-range ordered aluminosilicates (SROAS) that have to be considered in the development of synthesis protocols and may be relevant for the properties of SROAS in the environment. We synthesized SROAS of variable composition by neutralizing aqueous aluminium chloride with sodium orthosilicate at ambient temperature and pressure. We determined elemental composition, visualized morphology by microscopic techniques, and resolved mineral structure by solid-state 29Si and 27Al nuclear magnetic resonance and Fourier-transform infrared spectroscopy. Nitrogen sorption revealed substantial surface loss of Al-rich SROAS that resembled proto-imogolite formed in soils and sediments due to aggregation upon freezing. The effect was less pronounced in Si-rich SROAS, indicating a structure-dependent effect on spatial arrangement of mass at the submicron scale. Cryomilling efficiently fractured aggregates but did not change the magnitude of specific surface area. Since accessibility of surface functional groups is a prerequisite for sequestration of substances, elucidating physical and chemical processes of aggregation as a function of composition and crystallinity may improve our understanding of the reactivity of SROAS in the environment.

scholarly journals Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait

Plants ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 774
Author(s):  
Max Langer ◽  
Thomas Speck ◽  
Olga Speck
Keyword(s):  
Transition Zone ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Body Plan ◽  
The Body ◽  
Vascular Bundles ◽  
Cross Sectional ◽  
Thin Sections ◽  
Transition Zones ◽  
The Cross

Although both the petiole and lamina of foliage leaves have been thoroughly studied, the transition zone between them has often been overlooked. We aimed to identify objectively measurable morphological and anatomical criteria for a generally valid definition of the petiole–lamina transition zone by comparing foliage leaves with various body plans (monocotyledons vs. dicotyledons) and spatial arrangements of petiole and lamina (two-dimensional vs. three-dimensional configurations). Cross-sectional geometry and tissue arrangement of petioles and transition zones were investigated via serial thin-sections and µCT. The changes in the cross-sectional geometries from the petiole to the transition zone and the course of the vascular bundles in the transition zone apparently depend on the spatial arrangement, while the arrangement of the vascular bundles in the petioles depends on the body plan. We found an exponential acropetal increase in the cross-sectional area and axial and polar second moments of area to be the defining characteristic of all transition zones studied, regardless of body plan or spatial arrangement. In conclusion, a variety of terms is used in the literature for describing the region between petiole and lamina. We prefer the term “petiole–lamina transition zone” to underline its three-dimensional nature and the integration of multiple gradients of geometry, shape, and size.

scholarly journals Structure-Acid Lability Relationship of N-alkylated α,α-dialkylglycine Obtained via a Ugi Multicomponent Reaction

Molecules ◽  
2021 ◽  
Vol 26 (1) ◽  
pp. 197
Author(s):  
Iván Ramos-Tomillero ◽  
Marisa K. Sánchez ◽  
Hortensia Rodríguez ◽  
Fernando Albericio
Keyword(s):  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Structural Features ◽  
Amide Bond ◽  
Acidic Media ◽  
Phase Synthesis ◽  
Acyl Chains ◽  
Cyclic Compounds ◽  
Relationship Of ◽  
Fine Tune

Using the classical Ugi four-component reaction to fuse an amine, ketone, carboxylic acid, and isocyanide, here we prepared a short library of N-alkylated α,α-dialkylglycine derivatives. Due to the polyfunctionality of the dipeptidic scaffold, this highly steric hindered system shows an interesting acidolytic cleavage of the C-terminal amide. In this regard, we studied the structure-acid lability relationship of the C-terminal amide bond (cyclohexylamide) of N-alkylated α,α-dialkylglycine amides 1a–n in acidic media and, afterward, it was established that the most important structural features related to its cleavage. Then, it was demonstrated that electron-donating effects in the aromatic amines, flexible acyl chains (Gly) at the N-terminal and the introduction of cyclic compounds into dipeptide scaffolds, increased the rate of acidolysis. All these effects are related to the ease with which the oxazolonium ion intermediate forms and they promote the proximity of the central carbonyl group to the C-terminal amide, resulting in C-terminal amide cleavage. Consequently, these findings could be applied for the design of new protecting groups, handles for solid-phase synthesis, and linkers for conjugation, due to its easily modulable and the fact that it allows to fine tune its acid-lability.

Structural deformation-metamorphism and exhumation processes of Yuanmou metamorphic complex, Yunnan, China

2021 ◽  
Author(s):  
Xuemei Cheng ◽  
Shuyun Cao
Keyword(s):  
High Temperature ◽  
Electron Backscatter Diffraction ◽  
Early Stage ◽  
Structural Features ◽  
Detachment Fault ◽  
Ductile Deformation ◽  
Structural Deformation ◽  
Subsequent Stage ◽  
Metamorphic Complex ◽  
South Central

<p>Within orogenic zone and continental extensional area, it often developed metamorphic complex or metamorphic gneiss dome that widely exposed continental mid-lower crustal rocks, which is an ideal place to study exhumation processes of deep-seated metamorphic complex and rheology. The Yuanmou metamorphic complex is located in the south-central part of the "Kangdian Axis" in the western margin of Qiangtang Block and Yangtze Block, which is a part of the anticline of the Sichuan-Yunnan platform. Many research works mainly focus on the discussion of intrusion ages, aeromagnetic anomalies, and polymetallic deposits. However, the exhumation process and mechanism of the Yuanmou metamorphic complex are rarely discussed and still unclear. This study, based on detailed field geological observations, optical microscopy (OM), cathodoluminescence (CL), electron backscatter diffraction (EBSD) and electron probe (EMPA) were performed to illustrate the geological structure features, deformation-metamorphic evolution process and its tectonic significance of Yuanmou metamorphic complex during the exhumation process. All these analysis results indicate that the Yuanmou metamorphic complex generally exhibits a dome structure with deep metamorphic rocks and deformed rocks of varying degrees widely developed. Mylonitic gneiss and granitic intrusions are located in the footwall of the Yuanmou, which have suffered high-temperature shearing. The mylonitic fabrics and mineral stretching lineations in the deformed rock are strongly developed, forming typical S-L or L-shaped structural features. The high-temperature ductile deformation-metamorphism environment is high amphibolite facies, that is, the temperature range is between 620 ~ 690 ℃ and the pressure is between 0.8 ~ 0.95 Gpa. In the deformed rocks closed to the detachment fault, some of the mylonite fabric features are retained, but most of them have experienced a strongly overprinted retrogression metamorphism and deformation. At the top of the detachment fault zone, it is mainly composed of cataclasites and fault gouge. The comprehensive macro- and microstructural characteristics, geometry, kinematics, and mineral (amphibole, quartz and calcite) EBSD textures indicate that the Yuanmou metamorphic complex has undergone a progressive exhumation process during regional extension, obvious high-temperature plastic deformation-metamorphism in the early stage, and superimposed of low-temperature plastic-brittle and brittle deformation in the subsequent stage, which is also accompanied by strong fluid activities during the exhumation process.</p>

scholarly journals Effect of char layer on transient thermal oxidative degradation of polyethylene

2007 ◽  
Vol 11 (2) ◽  
pp. 23-36 ◽  
Author(s):  
Javad Esfahani ◽  
Ali Abdolabadi
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Solid Phase ◽  
Early Stage ◽  
Radiation Heat Transfer ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Thermal Oxidative Degradation ◽  
Char Layer ◽  
Effect Of Oxygen

A transient one dimensional model has been presented to simulate degradation and gasification of polyethylene, in early stage of fire growth. In the present model effect of oxygen on degradation and rate of polymer gasification while the sample is subjected to an external radiative heat source is numerically investigated. This model includes different mechanism, which affect the degradation process, such as in depth thermal oxidative decomposition, in depth absorption of radiation, heat transfer, volatiles advection in solid phase and convective heat transfer on surface. Also effects of radiative parameters, due to formation of char layer such as surface reflectivity and absorptivity on thermal degradation of polyethylene are investigated. The results for 40 kW/m2 heat source are reported and yielded realistic results, comparing to the published experimental data. The results show that an increase in oxygen concentration leads to considerable increase in gasification rate and also leads to sharp increase of surface temperature. .

scholarly journals INFLUENCE OF MECHANOMAGNETIC ACTIVATION OF SOLUTIONS CaCl2 AND Na2S2O3 ON PHASE STRUCTURE OF CEMENT STONE

2019 ◽  
Vol 62 (12) ◽  
pp. 101-107
Author(s):  
Tatyana E. Slizneva ◽  
Marina V. Akulova ◽  
Pavel B. Razgovorov
Keyword(s):  
Solid Phase ◽  
Tap Water ◽  
Pore Space ◽  
Control Sample ◽  
Hydrodynamic Cavitation ◽  
Cement Stone ◽  
Cement Pastes ◽  
Carbonate Ion ◽  
Joint Influence ◽  
Reactive Oxygen Forms

The mechanism of the joint influence of the magnetic field and hydrodynamic cavitation on the properties of CaCl2 and Na2S2O3 solutions used for mixing cement pastes is considered. Hydrodynamic cavitation leads to the formation of reactive oxygen forms, HCO3– anions, carbon dioxide nanobubbles, and initiates the interaction of new forms with impurity metal cations dissolved in water. After mechanomagnetic treatment of the solutions, particles of a solid phase with sizes of 5...10 and 10...100 nm were found in them. The observed increase in the ξ- potential indicates the stabilization of such dispersed systems with the preservation of nanoscale fractions in them (up to 3 days). At the same time, the progress of reactions under the conditions of tightness that occur after cement paste has been mixed. The effect of activating factors in tap water is more pronounced than in distilled water, which is explained by the process of hydration of the carbonate ion and the formation of fine nucleation centers. Using X-ray phase analysis, it was found that, along with calcite, aragonite crystallizes in the resulting cement stone, which is practically absent in the control sample. In addition, the analysis of diffraction patterns taken on the modified samples reveals the inclusion of a carbonate ion. Obviously, optimization of the pore space in the cement stone is achieved both by clogging the pores with fine calcium carbonate, and by forming small pores during crystallization of ettringite-like phases. It is established that the resulting cement stone is characterized by increased strength (by 9-30%) and frost resistance (up to 55%) compared to that obtained by the traditional method.

Obvious and less obvious processes of aggregate formation in soil

2021 ◽  
Author(s):  
Hans-Jörg Vogel ◽  
Mar­ia Balseiro-Romero ◽  
Philippe C. Baveye ◽  
Alexandra Kravchenko ◽  
Wilfred Otten ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Structure ◽  
Solid Phase ◽  
Pore Space ◽  
Imaging Techniques ◽  
Mineral Soil ◽  
Aggregate Formation ◽  
Conceptual Approach ◽  
Soil Matrix ◽  
Biophysical Processes

<p>Soil structure, lately referred to as the ''architecture'' is a key to explain and understand all soil functions. The development of sophisticated imaging techniques over the last decades has led to significant progress in the description of this architecture and in particular of the geometry of the hierarchically-branched pore space in which transport of water, gases, solutes and particles occurs and where myriads of organisms live. Moreover, there are sophisticated tools available today to also visualize the spatial structure of the solid phase including mineral grains and organic matter. Hence, we do have access to virtually all components of soil architecture.</p><p>Unfortunately, it has so far proven very challenging to study the dynamics of soil architecture over time, which is of critical importance for soil as habitat and the turnover of organic matter. Several largely conflicting theories have been proposed to account for this dynamics, especially the formation of aggregates. We review these theories, and we propose a conceptual approach to reconcile them based on a consistent interpretation of experimental observations and by integrating known physical and biogeochemical processes. A key conclusion is that rather than concentrating on aggregate formation in the sense of how particles and organic matter reorganize to form aggregates as distinct functional units we should focus on biophysical processes that produce a porous, heterogeneous organo-mineral soil matrix that breaks into fragments of different size and stability when exposed to mechanical stress.  The unified vision we propose for soil architecture and the mechanisms that determine its temporal evolution, should pave the way towards a better understanding of soil processes and functions.</p>

Protein Chains in Wool and Epidermal Keratin IF: Structural Features and Spatial Arrangement

1988 ◽  
pp. 127-144 ◽  
Author(s):  
J. F. Conway ◽  
R. D. B. Fraser ◽  
T. P. Macrae ◽  
D. A. D. Parry
Keyword(s):  
Spatial Arrangement ◽  
Structural Features

Transition Zone in Thermally Activated Solid-Phase Contact of Diamond with Iron and Titanium

2019 ◽  
Vol 39 (12) ◽  
pp. 1034-1042
Author(s):  
P. P. Sharin ◽  
M. P. Akimova ◽  
S. P. Yakovleva ◽  
A. M. Bol’shakov ◽  
V. I. Popov
Keyword(s):  
Transition Zone ◽  
Solid Phase ◽  
Phase Contact ◽  
Thermally Activated
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