Influence of hydrocarbon contamination on clay soil microstructure

Microstructural (fabric, forces and composition) changes due to hydrocarbon contamination in a clay soil were studied using Scanning Electron Microscope (micro-fabric analysis), Atomic Force Microscope (forces measurement) and sedimentation bench test (particle size measurements). The non-polluted and polluted glacial till from north-eastern Poland (area of a fuel terminal) were used for the study. Electrostatic repelling forces for the polluted sample were much lower than for the non-polluted sample. In comparison to non-polluted sample, the polluted sample exhibited lower electric charge, attractive forces on approach and strong adhesion on retrieve. The results of the sedimentation tests indicate that clay particles form larger aggregates and settle out of the suspension rapidly in diesel oil. In non-polluted soil, the fabric is strongly aggregated – densely packed, dominate the face-to-face and edge-to-edge types of contacts, clay film tightly adheres to the surface of larger grains and interparticle pores are more common. In polluted soil, the clay matrix is less aggregated – loosely packed, dominate the edge-to-face types of contacts and inter-micro-aggregate pores are more frequent. Substantial differences were observed in the morphometric and geometrical parameters of pore space. The polluted soil micro-fabric proved to be more isotropic and less oriented than in non-polluted soil. The polluted soil, in which electrostatic forces were suppressed by hydrocarbon interaction, displays more open porosity and larger voids than non-polluted soil, which is characterized by occurrence of the strong electrostatic interaction between clay particles.

Engineering behavior of uplifted Smectite-rich Cochin and Mangalore marine clays

The present study aims to assess whether the smectite-rich Cochin and Mangalore clays, which were deposited in a marine medium and subsequently uplifted, exhibit consistency limits response typical of expanding lattice or nonexpanding (fixed) lattice-type clays on artificially changing the chemical environment. The chemical and engineering behaviors of Cochin and Mangalore marine clays are also compared with those of the smectite-rich Ariake Bay marine clay from Japan. Although Cochin, Mangalore, and Ariake clays contain comparable amounts of smectite (32-45%), Ariake clay exhibits lower consistency limits and much higher ranges of liquidity indices than the Indian marine clays. The lower consistency limits of the Ariake clay are attributed to the absence of well-developed, long-range, interparticle forces associated with the clay. Also, Ariake clay exhibits a significantly large (48-714 times) decrease in undrained strength on remolding in comparison to Cochin and Mangalore clays (sensitivity ranges between 1 and 4). A preponderance of long-range, interparticle forces reflected in the high consistency limits of Cochin and Mangalore clays (wL range from 75 to 180%) combined with low natural water contents yield low liquidity indices (typically <1) and high, remolded, undrained strengths and are considered to be responsible for the low sensitivity of the Indian marine clays.

Consistency limits behavior of bentonites exposed to sea water

This article examines the changes in interparticle forces brought about on prolonged contact (1 year period) of a bentonite clay with artificial seawater. The study is undertaken with the purpose of identifying the physico-chemical factors that impart a nonswelling character to smectite clays deposited in marine environments. Results show that equilibration of the bentonite clay with artificial seawater (total pore salinity approximately 42 gL-1) for a 1 year period does not lead to any mineralogical changes in the clay specimens; however, their exchangeable cation positions become prominently dominated by magnesium ions. The consistency limits of the seawater-equilibrated bentonite was determined on stepwise leaching to lower salinities. The predominance of diffuse double-layer repulsion forces in the pore salt concentration range of 42 gL-1 to 1.1 gL-1 caused an increase in the liquid limits of the seawater-equilibrated bentonite specimens on reducing the salinity in the corresponding range (42 gL-1 to 1.1 gL-1). The attraction forces, however, prevail over the repulsion forces at salt concentrations <1.1 gL-1 and cause a decrease in liquid limit of the clay specimens with reduction in pore salinity, which is typical of nonswelling clays. The attraction forces cause aggregation of the clay unit layers into domains that break down on sodium saturation of the clay specimens. It is inferred that the physico-chemical factors responsible for the nonswelling character of the seawater-equilibrated bentonite specimens at pore salt concentrations below 1.1 gL-1 are inadequate to explain the nonswelling character of smectite-rich Ariake marine clays. The lower consistency limits of the Ariake marine clays in comparison to the nonswelling character, seawater-equilibrated bentonite specimens is attributed to a relative deficiency of interparticle forces in the Ariake marine clay.

Ionic Bonding between Artificial Atoms

Conventional solids are prepared from building blocks that are conceptually no larger than a hundred atoms. While van der Waals and dipole-dipole interactions also influence the formation of these materials, stronger interactions, referred to as chemical bonds, play a more decisive role in determining the structures of most solids. Chemical bonds that hold such materials together are said to be ionic, covalent, metallic, dative, or otherwise a combination of these. Solids that utilize semiconductor nanocrystal quantum dots as building units have been demonstrated to exist; however, the interparticle forces in such materials are decidedly not chemical. Here we demonstrate the formation of charge transfer states in a binary quantum dot mixture. Charge is observed to reside in quantum confined states of one of the participating quantum dots. These interactions lead to materials that may be regarded as the nanoscale analog of an ionic solid. The process by which these materials form has interesting parallels to chemical reactions in conventional chemistry.

Effect of weak Brownian motion on gravitational coagulation

The effect of a small amount of Brownian diffusion on gravitational coagulation is numerically calculated by incorporating gravitational and interparticle forces (both attractive and repulsive), as well as hydrodynamic interactions. It is found that weak Brownian diffusion, the effect of which is nonlinearly coupled with gravity, can act to decrease the coagulation rate.

Sedimentologic and magnetic data of sediment cores on the western slope of the Mid-Atlantic Ridge

The relative paleointensity (RPI) method assumes that the intensity of post depositional remanent magnetization (PDRM) depends exclusively on the magnetic field strength and the concentration of the magnetic carriers. Sedimentary remanence is regarded as an equilibrium state between aligning geomagnetic and randomizing interparticle forces. Just how strong these mechanical and electrostatic forces are, depends on many petrophysical factors related to mineralogy, particle size and shape of the matrix constituents. We therefore test the hypothesis that variations in sediment lithology modulate RPI records. For 90 selected Late Quaternary sediment samples from the subtropical and subantarctic South Atlantic Ocean a combined paleomagnetic and sedimentological dataset was established. Misleading alterations of the magnetic mineral fraction were detected by a routine Fe/kappa test (Funk, J., von Dobeneck, T., Reitz, A., 2004. Integrated rock magnetic and geochemical quantification of redoxomorphic iron mineral diagenesis in Late Quaternary sediments from the Equatorial Atlantic. In: Wefer, G., Mulitza, S., Ratmeyer, V. (Eds.), The South Atlantic in the Late Quaternary: reconstruction of material budgets and current systems. Springer-Verlag, Berlin/Heidelberg/New York/Tokyo, pp. 239-262). Samples with any indication of suboxic magnetite dissolution were excluded from the dataset. The parameters under study include carbonate, opal and terrigenous content, grain size distribution and clay mineral composition. Their bi- and multivariate correlations with the RPI signal were statistically investigated using standard techniques and criteria. While several of the parameters did not yield significant results, clay grain size and chlorite correlate weakly and opal, illite and kaolinite correlate moderately to the NRM/ARM signal used here as a RPI measure. The most influential single sedimentological factor is the kaolinite/illite ratio with a Pearson's coefficient of 0.51 and 99.9% significance. A three-member regression model suggests that matrix effects can make up over 50% of the observed RPI dynamics.

Three-dimensional solitons in coupled atomic-molecular Bose-Einstein condensates

We present a theoretical analysis of three-dimensional (3D) matter-wave solitons and their stability properties in coupled atomic and molecular Bose-Einstein condensates (BECs). The soliton solutions to the mean-field equations are obtained in an approximate analytical form by means of a variational approach. We investigate soliton stability within the parameter space described by the atom-molecule conversion coupling, the atom-atom s-wave scattering, and the bare formation energy of the molecular species. In terms of ordinary optics, this is analogous to the process of sub- or second-harmonic generation in a quadratic nonlinear medium modified by a cubic nonlinearity, together with a phase mismatch term between the fields. While the possibility of formation of multidimensional spatiotemporal solitons in pure quadratic media has been theoretically demonstrated previously, here we extend this prediction to matter-wave interactions in BEC systems where higher-order nonlinear processes due to interparticle collisions are unavoidable and may not be neglected. The stability of the solitons predicted for repulsive atom-atom interactions is investigated by direct numerical simulations of the equations of motion in a full 3D lattice. Our analysis also leads to a possible technique for demonstrating the ground state of the Schrodinger-Newton and related equations that describe Bose-Einstein condensates with nonlocal interparticle forces.

Mechanics of raceway hysteresis in a packed bed

When a gas is introduced at high velocity through a nozzle into a packed bed, it creates a raceway in the packed bed. It has been found that the raceway size is larger when it is formed by decreasing the gas velocity from its highest value than when it is formed by increasing the gas velocity. This phenomenon is known as raceway hysteresis. A hypothesis has been oroposed to explain the hysteresis phenomenon based on a force-balance approach which includes frictional, bed-weight, and pressure forces. According to this hypothesis, the frictional force acts in different directions when the raceway is expanding and contracting. In this article, the entire packed bed has been divided into radial and Cartesian co-ordinate systems, and the forces acting on the raceway have been solved analytically for a simplified one-dimensional case. Based on the force-balance approach, a general equation has been obtained to predict the diameter of the raceway for increasing And decreasing velocities. A reasonable agreement has been found between the theoretical predictions and experimental observations. The model has also been compared with published experimental and plant data. The hysteresis mechanism in the packed beds can be described reasonably by taking into consideration the direction of frictional forces for the increasing- and decreasin-velocity cases. The effects of the particleshape factor and void fraction on the raceway hysteresis are examined.

Comparative analysis of experimental and modelling of gas-solid flow hydrodynamics:effect of friction and interparticle cohesion forces

The effect of friction and interparticle cohesion forces on the gas-solid flow hydrodynamics was discussed. A proposed interparticle cohesion and frictional force terms have been tested in a continuum fully developed flow model to investigate their effect on the general hydrodynamic features of vertical duct flow. It was observed that both terms have direct effect on lowering the material carryover, which implies a reduced bed expansion in freely bubbling column. The parametric analysis shows that cohesion and frictional forces are high when compared to kinetic stress and hence it can play a major role in describing the hydrodynamics features of the flow.

Development of a system measuring adhesion forces in powder collectives

Fine powders commonly have poor flowability and dispersibility due to interparticle adhesion that leads to formation of agglomerates. Knowing about adhesion in particle collectives is indispensable to gain a deeper fundamental understanding of particle behavior in powders. Especially in pharmaceutical industry a control of adhesion forces in powders is mandatory to improve the performance of inhalation products. Typically the size of inhalable particles is in the range of 1 - 5 µm. In this thesis, a new method was developed to measure adhesion forces of particles as an alternative to the established colloidal probe and centrifuge technique, which are both experimentally demanding, time consuming and of limited practical applicability. The new method is based on detachment of individual particles from a surface due to their inertia. The required acceleration in the order of 500 000 g is provided by a Hopkinson bar shock excitation system and measured via laser vibrometry. Particle detachment events are detected on-line by optical video microscopy. Subsequent automated data evaluation allows obtaining a statistical distribution of particle adhesion forces. To validate the new method, adhesion forces for ensembles of single polystyrene and silica microspheres on a polystyrene coated steel surface were measured under ambient conditions. It was possible to investigate more than 150 individual particles in one experiment and obtain adhesion values of particles in a diameter range of 3 - 13 µm. This enables a statistical evaluation while measuring effort and time are considerably lower compared to the established techniques. Measured adhesion forces of smaller particles agreed well with values from colloidal probe measurements and theoretical predictions. However, for the larger particles a stronger increase of adhesion with diameter was observed. This discrepancy might be induced by surface roughness and heterogeneity that influence small and large particles differently. By measuring adhesion forces of corrugated dextran particles with sizes down to 2 µm it was demonstrated that the Hopkinson bar method can be used to characterize more complex sample systems as well. Thus, the new device will be applicable to study a broad variety of different particle-surface combinations on a routine basis, including strongly cohesive powders like pharmaceutical drugs for inhalation.

Marketplace forces and the history of retailing : The cycle of control

This paper traces the history of store (retailer-controlled) and national (manufacture controlled)brands; identifies the key historical characteristics of the past 200 years of marketing history;describes the four main time periods of U.S. retail marketing (1800 - 2000); and comments on the most likely developments within the current phases of brand marketing. Will the future focus on technology and new forms of communications? The Internet exemplifies an unconventional retailing environment, with etailer numbers growing rapidly. The central proposition of this paper is that a "cycle of control" - a pattern of marketing developments within the history of retailing and national marketing communications - Can indicate the success of marketing strategies in the future.

Project diagnostics : assessing the condition of projects and identifying poor health combing forces

In many cases, construction projects do not achieve the objectives that the project participants set for them. If participants could better understand how their project is performing overall, at various stages of its delivery, then the opportunities to achieve project success would almost certainly be greater. This paper documents a method of assessing the status of a project, at a point in its design or construction phase, or after completion. The status is assessed in terms of up to seven (7) key success factors. Any evidence of less than adequate performance in these performance areas is scrutinised to seek out the root causes of why this situation is happening. Using these identified root causes of under performance, general suggestions can then be made as to how to return the project to good health. A software package that assists in assessing the status of the project has been developed. The package is currently being calibrated before commercial release.