Imaging structures and measuring forces at nanoscales with atomic force microscopy

Interaction between interfaces in solution of chemical reagents is scientifically and technologically significant. Atomic force microscopy has been used to visualise structures of adsorbed surfactant molecules and measure interaction forces between surfaces with adsorbed molecules. This paper presents the results obtained by the author and associates in three major research strands, including imaging structures of surfactants adsorbed at solid-liquid interfaces, measuring interfacial forces between water-repellent (hydrophobic) surfaces and microhydrodynamic forces between an AFM colloid probe and a soft interface. The research increases our understanding of the role of surfactants and interaction forces in particle technology and interface science

Intrinsic Domain Wall Resistance in Ferromagnetic Semiconductors

Transport through zincblende magnetic semiconductors with magnetic domain walls is studied theoretically. We show that these magnetic domain walls have an intrinsic resistance due to the spin-orbit interaction. The intrinsic resistance is independent of the domain wall shape and width when the latter is larger than the Fermi wavelength. For typical parameters, the intrinsic domain wall resistance is comparable to the Sharvin resistance and should be experimentally measurable.Comment: Final versio

Adaptive State Feedback Control of Lorenz Systems to Its Non-Trivial Equilibrium

The complex Lorenz system is a simplified nonlinear dynamical system, which is derived from the Navier-Stokes equations that govern a closed thermal convection loop. The Lorenz system is chaotic for large Rayleigh number. In this chaotic regime, we implement a linear state feedback controller to stabilize the state trajectory at its original nontrivial equilibrium. The state variable for feedback is easily measurable. The system is proved to be globally asymptotically stable with a optimal feedback gain. The stability bound is improved over the previous result. We also established globally stability of the adaptively control system, where the system parameters are unknown. We present numerical simulations to demonstrate the stability, transient and steady state responses, and the performance of the state feedback controller

Fractional Stokes-Boussinesq-Langevin equationand Mittag-Leffler correlation decay

his paper presents some stationary processes which are solutions of the fractional Stokes-Boussinesq-Langevin equation. These processes have reflection positivity and their correlation functions, which may exhibit the Alder-Wainwright effect or long-range dependence, are expressed in terms of the Mittag-Leffler functions. These properties are established rigorously via the theory of KMO-Langevin equation and a combination of Mittag-Leffler functions and fractional derivatives. A~relationship to fractional Riesz-Bessel motion is also investigated. This relationship permits to study the effects of long-range dependence and second-order intermittency simultaneously

A review of principles and applications of magnetic flocculation to separate ultrafine magnetic particles

Magnetic separation has been used in industries to concentrate or remove magnetic minerals/particles for many years. The separation of ultrafine magnetic particles is significantly influenced by aggregation between particles due to various external and interparticle forces, such as gravity, magnetic attraction, van der Waals, electrical double-layer, hydrodynamic, and Brownian diffusion forces. This review focuses on the principles of the magnetic flocculation and separation of micrometer-sized particles in solution. Potential energies between particles are linked to the particle aggregation (i.e. stability), sedimentation and dispersion in applied magnetic fields. Prediction and control of magnetic flocculation are achieved by simulating particle motions around the surface of the magnetic separators using various mathematical models, with some large-scale applications of magnetic flocculation are being demonstrated

Irreducible representations of Upq[gl(2/2)]

The two-parametric quantum superalgebra $U_{pq}[gl(2/2)]$ and its representations are considered. All finite-dimensional irreducible representations of this quantum superalgebra can be constructed and classified into typical and nontypical ones according to a proposition proved in the present paper. This proposition is a nontrivial deformation from the one for the classical superalgebra gl(2/2), unlike the case of one-parametric deformations.Comment: Latex, 8 pages. A reference added in v.

Temperature dependent graphene suspension due to thermal Casimir interaction

Thermal effects contributing to the Casimir interaction between objects are usually small at room temperature and they are difficult to separate from quantum mechanical contributions at higher temperatures. We propose that the thermal Casimir force effect can be observed for a graphene flake suspended in a fluid between substrates at the room temperature regime. The properly chosen materials for the substrates and fluid induce a Casimir repulsion. The balance with the other forces, such as gravity and buoyancy, results in a stable temperature dependent equilibrium separation. The suspended graphene is a promising system due to its potential for observing thermal Casimir effects at room temperature.Comment: 5 pages, 4 figures, in APL production 201

Potential Desalination of Coal Seam Gas Coproduced Water Using Zeolite

Natural clinoptilolite type zeolite was examined for its potential to treat coal seam gas (CSG) water and remove sodium ions to lower sodium adsorption ratio and reduce pH. The effectiveness of unmodified and modified natural zeolite is due to their regular composition and open porous structure, high exchange capacity, mechanical strength and stability, and consistency in particle size. The effects of acid modification in bringing about changes to the physicochemical properties of clinoptilolite underpin the effectiveness of this material for treatment of CSG saline water. The sodium adsorption capacity of acid-modified zeolite increases up to three times greater than that of the unmodified zeolite. The atomic percentage and binding energies of the chemical elements comprising zeolite are changed significantly following the acid modification. The Si/Al atomic ratio increases with increasing sulfuric acid concentration. Dealumination is the main reason for the increase in the surface charge and cation exchange capacity of clinoptilolite after acid modification. It is due to the increased defects in the crystal structure/lattice, which result in increasing numbers of charge vacancies. Sodium-rich synthetic zeolites 4A and Na─Y after acid modification are also examined by following the dissolution of the first-order fast kinetics and recrystallization processes which can be homogeneous or heterogeneous