The nature of soil clays and the stability of microaggregates

Soil Research ◽  
1977 ◽  
Vol 15 (2) ◽  
pp. 115 ◽  
Author(s):  
GSRK Murti ◽  
Singh Gurcharan ◽  
P Rengasamy
Keyword(s):  
Iron Oxide ◽  
Clay Mineral ◽  
Size Range ◽  
Alluvial Soils ◽  
Relative Importance ◽  
Clay Particles ◽  
Cohesive Forces ◽  
Soil Clays ◽  
The Stability

The relative importance of the nature of clay fractions in the stability of microaggregates was investigated in the ferruginous soils, black soils and alluvial soils of India widely differing in their mineralogy. The influence of clay-iron oxide interaction was common in all these soils. However, the size range of stable aggregates depended on the dominant clay mineral, kaolinite influencing <50 �m aggregates and smectite in the formation of 250-1000 �m aggregates. The influence of cohesive forces between clay particles was more than the clay-iron oxide interaction in the smectitic soiIs.

The solubility of potassium from soil illites. I. The dependence of solubility on pH.

Soil Research ◽  
1964 ◽  
Vol 2 (1) ◽  
pp. 56 ◽  
Author(s):  
BM Tucker
Keyword(s):  
Clay Mineral ◽  
Hydrogen Ions ◽  
Equilibrium Solubility ◽  
Clay Particles ◽  
Potassium Release ◽  
Ph Values ◽  
Minimum Value ◽  
Soil Clays ◽  
Mineral Structure

The equilibrium solubility of potassium from the lattice of illites in four soil clays has been measured. This solubility is related to the availability of this potassium and, when account is taken of the fineness of the clay particles, it is found to decrease as the illite structure becomes more degraded by loss of lattice potassium. The solubility depends on the pH of the system in the same way for all the clays, and a minimum value is found near to pH 11. Above this pH, potassium release is due to breakdown of the clay mineral. At lower pH values the release is due either to the instability of the clay mineral structure towards hydrogen ions or to displacement of potassium by other cations acting together with hydrogen ions.

Lack of Stability of Aggregates after Thrombin-Induced Reaggregation of Thrombin-Degranulated Platelets

1992 ◽  
Vol 67 (04) ◽  
pp. 453-457 ◽  
Author(s):  
Raelene L Kinlough-Rathbone ◽  
Marian A Packham ◽  
Dennis W Perry ◽  
J Fraser Mustard ◽  
Marco Cattaneo
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Aggregate Stability ◽  
Relative Importance ◽  
Platelet Aggregates ◽  
The Stability ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor

SummaryThe stability of platelet aggregates is influenced by the extent of the release of granule contents; if release is extensive and aggregation is prolonged, deaggregation is difficult to achieve. The relative importance of the contributions of released substances to aggregate stability are not known, although stable thrombin-induced aggregates form in platelet-rich plasma from patients with barely detectable plasma or platelet fibrinogen, and ADP stabilizes thrombin-induced aggregates of platelets from patients with delta storage pool deficiency which otherwise deaggregate more readily than normal platelets. We degranulated platelets with thrombin (0.9 U/ml caused greater than 90% loss of delta and alpha granule contents) and recovered them as individual platelets in fresh medium. The degranulated platelets were reaggregated by thrombin (2 U/ml). To prevent continuing effects of thrombin, FPRCH2C1 was added when thrombin-induced aggregation of thrombin-degranulated platelets reached its maximum. EDTA (5 mM) or EGTA (5 mM) added at maximum aggregation did not deaggregate these platelets, indicating that the stability of these aggregates does not depend on Ca2+ in the medium. Whereas with control platelets a combination of PGE1 (10 μM) and chymotrypsin(10 U/ml) was required for deaggregation, with thrombin-degranulated platelets either PGE1 or chymo-trypsin alone caused extensive deaggregation. The rate and extent of deaggregation of thrombin-degranulated platelets by a combination of PGE1 and chymotrypsin was greater than with control platelets.Electron microscope gold immunocytochemistry using antihuman fibrinogen IgG, anti-von Willebrand factor and anti-fibronectin showed a) that fibrinogen in the vacuoles of degranulated platelets was visible at focal points of platelet contact in the aggregates, but that large areas of platelet contact had no fibrinogen detectable between them; and b) in comparison to fibrinogen, little fibronectin or von Willebrand factor (vWf) was detectable in the platelets.Since the linkages between thrombin-degranulated platelets reaggregated by thrombin can be disrupted either by raising cAMP (thus making glycoprotein IIb/IIIa unavailable) or by proteolysis, these linkages are less stable than those formed between normal platelets. It might therefore be expected that platelets that take part in thrombus formation and then recirculate are likely to form less stable thrombi than platelets that have not released their granule contents.

scholarly journals Green synthesis of magnetic α–Fe2O3 nanospheres using Bridelia retusa leaf extract for Fenton-like degradation of crystal violet dye

2021 ◽  
Author(s):  
Raja Selvaraj ◽  
Shraddha Pai ◽  
Gokulakrishnan Murugesan ◽  
Sadanand Pandey ◽  
Ruchi Bhole ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Green Synthesis ◽  
Crystal Violet ◽  
Leaf Extract ◽  
Bet Analysis ◽  
Crystal Violet Dye ◽  
Pros And Cons ◽  
Manufacturing Techniques ◽  
The Stability ◽  
Bridelia Retusa

AbstractThe reach of nanotechnology has permeated into a range of disciplines and systematically revolutionized many manufacturing techniques. Today, nanoparticles are fabricated using varied approaches, each with its pros and cons. Of them, the green synthesis approach has been very effective in terms of overall economics and the stability of nanoparticles. The current study investigates the use of the leaf extract of Bridelia retusa for the synthesis of iron oxide nanoparticles. Typical of these nanoparticles, no specific peak was discernible on employing UV–visible spectroscopy. The size, morphological features, and crystallinity of the nanoparticles were determined by employing scanning electron microscopy and electron diffraction spectroscopy. Almost uniformly sized at 38.58 nm, the nanoparticles were spherical, constituting elemental iron at 11.5% and elemental oxygen at 59%. Their relative composition confirmed the nanoparticles to be iron oxide. X-ray diffraction studies showed the particles to be hexagonal and rhombohedral, estimating the crystallite size at 24.27 nm. BET analysis put the pore volume at 0.1198 cm3/g and pore diameter at 7.92 nm. The unique feature of the nanoparticles was that the specific surface area was 75.19 m2/g, which is more than 12 times higher than commercial α-Fe2O3. The participation of a variety of biochemicals in the leaf extract towards the reduction-cum-stabilization was confirmed using FTIR analysis. The Fenton-like catalytic activity of the nanoparticles was put to test by attempting to degrade crystal violet dye, which was completely achieved in 270 min. The kinetics of the degradation was also modelled in the study.

The Effect of Time on the Stability of Iron Oxide Nanoparticles in Environmental Acids

2017 ◽  
Vol 89 (5) ◽  
pp. 416-423 ◽  
Author(s):  
Anna Rabajczyk ◽  
Naouale El Yamani ◽  
Maria Dusinska
Keyword(s):  
Iron Oxide ◽  
Iron Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
The Stability

Rapidly rotating thermal convection at low Prandtl number

2001 ◽  
Vol 428 ◽  
pp. 61-80 ◽  
Author(s):  
J. H. P. DAWES
Keyword(s):  
Prandtl Number ◽  
Perturbation Expansion ◽  
Plane Layer ◽  
Interesting Case ◽  
Relative Importance ◽  
Leading Order ◽  
Amplitude Equations ◽  
Onset Of Convection ◽  
Dimensionless Groups ◽  
The Stability

Rotating Boussinesq convection in a plane layer is governed by two dimensionless groups in addition to the Rayleigh number R: the Prandtl number σ and the Taylor number Ta. Scaled equations for fully nonlinear rotating convection in the limit of rapid rotation and small Prandtl number, where the onset of convection is oscillatory, are derived by considering distinguished limits where σnTa1/2 ∼ 1 but σ → 0 and Ta → ∞, for different n > 1. In the resulting asymptotic expansion in powers of Ta−1/2 and the amplitude of convection. Three distinct asymptotic regimes are identified, distinguished by the relative importance of the subdominant buoyancy and inertial terms. For the most interesting case, n = 4, the stability of different planforms near onset is investigated using a double expansion in powers of Ta−1/8 and the amplitude of convection ε. The lack of a buoyancy term at leading order demands that the perturbation expansion be continued through six orders to derive amplitude equations determining the dynamics. The case n = 1 is also analysed. The relevance of this theory to experimental results is briefly discussed.

The role of reactive surface sites and complexation by humic acids in the interaction of clay mineral and iron oxide particles

2004 ◽  
Vol 35 (3) ◽  
pp. 257-267 ◽  
Author(s):  
Etelka Tombácz ◽  
Zsuzsanna Libor ◽  
Erzsébet Illés ◽  
Andrea Majzik ◽  
Erwin Klumpp
Keyword(s):  
Iron Oxide ◽  
Clay Mineral ◽  
Humic Acids ◽  
Iron Oxide Particles ◽  
Surface Sites ◽  
Reactive Surface ◽  
Oxide Particles

Exchangeable calcium, magnesium and sodium and the dispersion of illites in water. II. Dispersion of illites in water

Soil Research ◽  
1977 ◽  
Vol 15 (3) ◽  
pp. 255 ◽  
Author(s):  
WW Emerson ◽  
CL Chi
Keyword(s):  
Water Content ◽  
Particle Aggregation ◽  
The Other ◽  
Clay Particles ◽  
Exchangeable Calcium ◽  
Soil Clays ◽  
Exchangeable Magnesium ◽  
Calcium Magnesium ◽  
Calcium And Magnesium ◽  
Dominant Cation

Samples of illites, two extracted from soils, one from a shale, prepared with a range of exchangeable calcium, magnesium, sodium were immersed dry into water. The extent of dispersion with time was estimated visually and also deduced from the O.D. of the suspensions derived from the dispersed clay. The dispersion of wet calcium and magnesium soil illites sheared at a given water content and then immersed in water was also assessed visually. The dispersion of all three illites was enhanced when magnesium was the dominant cation rather than calcium. For the soil clays a lower ESP was required to initiate dispersion of the dry clay when immersed in water. Both calcium and magnesium forms of the shale illite dispersed partially over a period of several days when immersed dry into water, the magnesium to a greater extent than calcium. The magnesium form of the coarser of the two soil illites also dispersed slowly. By comparing the calcium-magnesium and calcium-sodium forms of the last clay, it was deduced that about 10 times the equivalent concentration of exchangeable magnesium as sodium was needed to cause the same degree of dispersion. For the other soil illite the water content for dispersion of the wet, sheared magnesium clay was found to be less than for the calcium clay. The O.D. of suspensions of the clays was found to decrease with increasing ESP and when magnesium was the dominant cation rather than calcium. This is explained in terms of particle aggregation. The ease of dispersion of the illites was correlated with particle size. Possible reasons for this, and the effect of magnesium, as opposed to calcium, on the forces between the clay particles are discussed.

scholarly journals SPACE-TIME SYMMETRIES AND SEMICLASSICAL AMPLITUDES

1994 ◽  
Vol 09 (17) ◽  
pp. 1589-1601 ◽  
Author(s):  
THOMAS M. GOULD ◽  
STEPHEN D.H. HSU
Keyword(s):  
Path Integral ◽  
Semiclassical Approximation ◽  
Space Time ◽  
Reflection Symmetry ◽  
Relative Importance ◽  
Initial State ◽  
Integral Action ◽  
The Stability

We examine the space-time symmetries of forward 2→2 scattering. These symmetries have non-trivial consequences for any class of configurations which might dominate the amplitude in the semiclassical approximation. We derive some dynamical results regarding the stability of configurations which arise solely from reflection symmetry and positivity of the (Euclidean) path-integral action. We consider the relative importance of initial state effects on non-O(3) symmetric configurations.

Controlled Synthesis of Iron Oxide Nanoparticles over a Wide Size Range

Langmuir ◽  
2010 ◽  
Vol 26 (8) ◽  
pp. 5843-5847 ◽  
Author(s):  
Pablo Guardia ◽  
Nicolás Pérez ◽  
Amilcar Labarta ◽  
Xavier Batlle
Keyword(s):  
Iron Oxide ◽  
Iron Oxide Nanoparticles ◽  
Size Range ◽  
Oxide Nanoparticles ◽  
Controlled Synthesis ◽  
Wide Size Range

scholarly journals Dynamic Properties of an Aggregate Econometric Model of Pakistan's Economy

1993 ◽  
Vol 32 (4II) ◽  
pp. 1031-1041 ◽  
Author(s):  
Ather Maqsood Ahmed ◽  
Muhammad Rafiq ◽  
M. Shahid Iqbal
Keyword(s):  
Econometric Model ◽  
Dynamic Properties ◽  
Structural Equations ◽  
Recent Experience ◽  
Relative Importance ◽  
Monetary Policies ◽  
Endogenous Variables ◽  
Price Hike ◽  
The Stability ◽  
The Impact

The use of econometric models for policy planning and decision-making is wide-spread in many developed as well as developing countries. One of the most vexing problems of such an exercise is to construct a model that could adequately reproduce the dynamic behaviour of an economy. The recent experience in modelling has shown that policy objectives could be achieved only by recognising the complex relationship between real and monetary variables. Such an integrated framework .could be used not only to compute impact and dynamic multipliers and to determine the stability of the model, but also to evaluate the relative importance offiscal and monetary policies. In the present paper, this objective is achieved by constructing a linear yet dynamic macro-econometric model of Pakistan's economy.' This model although has a Keynesian structure, but it could easily and meaningfully be solved to determine the values of endogenous variables especially income in terms of pure exogenous variables. In order to establish the dynamic stability of the model, we seek to present the "necessary conditions" that will depend not only on the structure of the model, but also on the estimated paramters of structural equations. After establishing the stability of the model, the next step is policy evaluation. In this regard the impact and the dynamic multipliers will be computed. These multipliers will then be used to assess the relative importance of fiscal and monetary policy variables on income and other dependent variables such as consumption and investment. The time period under consideration ranges between 1959-60 and 1987-88 which includes dramatic events like two wars with India, nationalisation, the oil price hike, recession and floods.

Sign in / Sign up

Export Citation Format

Share Document