Collective deformation modes promote fibrous self-assembly in protein-like particles

The self-assembly of particles into organized structures is a key feature of living organisms and a major engineering challenge. While it may proceed through the binding of perfectly matched, puzzle-pieces-like particles, many other instances involve ill-fitting particles that must deform to fit together. These include some pathological proteins, which have a known propensity to form fibrous aggregates. Despite this observation, the general relationship between the individual characteristics of the particles and the overall structure of the aggregate is not understood. To elucidate it, we analytically and numerically study the self-assembly of two-dimensional, deformable ill-fitting particles. We find that moderately sticky particles tend to form equilibrium self-limited aggregates whose size is set by an elastic boundary layer associated with collective deformations that may extend over many particles. Particles with a soft internal deformation mode thus give rise to large aggregates. Besides, when the particles are incompressible, their aggregates tend to be anisotropic and fiber-like. Our results are preserved in a more complex particle model with randomly chosen elastic properties. This indicates that generic protein characteristics such as allostery and incompressibility could favor the formation of fibers in protein aggregation, and suggests design principles for artificial self-assembling structures.Comment: 21 pages, 12 figure

PARTICLE SIZE DISTRIBUTION ANALYSIS IN AGGREGATE PROCESSING PLANTS USING DIGITAL IMAGE PROCESSING METHODS

Sensitive determination of the particle size distribution is an important procedure in terms of efficiency as wells affordability in mining operations which includes many stages such as blasting and mineral processing. Digital image processing methods used in mineral processing discipline found different application areas due to providing accurate data in relatively short time. In this study, the particle size distribution analysis of the samples taken from privately owned aggregate processing plants using sieve analysis and digital image processing methods were conducted and accordingly a comparison of these methods in terms of the applicability on industrial scale were realized. In this context, a pilot setup was assembled for the laboratory and plant scale image processing analysis purposes. Particle size distribution measurements of the samples were conducted by digital image processing method using this pilot setup and conventional sieve analysis methods. As a result, d(20,) d(50)( )and d(80)( )sizes of a crushed stone plant product were determined with confidence levels of 94.75%, 88.45% and 80.00%, respectively. The obtained results showed that a system based on digital image processing method can be applied in particle size analysis with high success has alternatives to conventional methods

Gold Extraction from an Oxide Ore by Thiourea Leaching with Hydrogen Peroxide as an Oxidant

In this study, the effects of thiourea (CH4N2S) on the efficiency of gold dissolution were investigated for the extraction of gold from an oxide gold ore of the eastern Anatolia region, Turkey. In the thiourea leaching experiments; several parameters such as particle size (-75, -53, and -38 mu m), leaching time (30, 60, 120, 180, and 240 min), thiourea concentration (0.1, 0.25, 0.5, 1, and 1.5 mol/dm(3)), pH (1, 2, 3, 4, and 5), and pulp temperature (20, 40, 60, and 80 degrees C) were examined using hydrogen peroxide (H2O2) as an oxidant. The results from these experiments showed that the highest efficiency for Au dissolution was obtained as 91.94% at -38 mu m particle size, 120 min of leaching time, 1 mol/dm(3) thiourea concentration, pH 1, and 80 degrees C pulp temperature. The results obtained from this study indicated that the thiourea leaching could be evaluated as an alternative method for the dissolution of gold from oxide gold ores

Curvature-Tilt Theories of Lipid Membranes

On mesoscopic scales lipid membranes are well described by continuum theories whose main ingredients are the curvature of a membrane’s reference surface and the tilt of its lipid constituents. In particular, Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)] showed how to systematicallyderive such a tilt-curvature Hamiltonian, based on the elementary assumption of a thin fluid elastic sheet experiencing internal lateral pre-stress. Performing a dimensional reduction, they not only derived the basic form of the effective surface Hamiltonian, but also made connections between the trans-membrane moments of lower-level material parameters and the emergent elasticcouplings of surface energy. In the present thesis we argue, though, that their derivation unfortunately missed a coupling term between curvature and tilt. The origin of this term is the change of transverse distances due to the variation in the curvature along the membranes. This change gives rise to a contribution to the energy which was believed to be small, but nevertheless ends up contributing at the same (quadratic) order as other terms in their Hamiltonian. We show the immediate consequences of this novel coupling term by by deriving the monolayer and bilayerEuler-Lagrange equations for the tilt, as well as the power spectra of shape, tilt, and director fluctuations.We also obtain a novel set of terms, quadratic in both curvature and tilt, of which only two were part of the quadratic theory. These biquadratics manifest as geometry-dependent corrections to the tilt modulus, converting it into a position-dependent tilt modulus tensor. For typicalmaterial parameters, the resulting effective tilt modulus softens compared to the bare one, except within a small off-center domain of curvatures near the flat state. For sufficiently large curvatures, set by the characteristic length of tilt decay, the effective modulus even becomes negative.We show that biquadratics matter for strongly curved geometries, such as open edges, triple line junctions, fusion stalks, and even bicontinuous phases, and as an illustration we calculate the line tension of edges and junctions

Investigation of recovery possibilities of rutile minerals from the feldspar tailings with gravity separation methods

In feldspar processing, flotation beneficiation tailings that containing high ratio of titanium minerals emerge at a considerable amount as a result of beneficiation of feldspar reserves with high TiO2 content due to required specifications by global feldspar market. Recovery of titanium minerals from these tailings which can be evaluated as alternative TiO2 resources is an important research topic as they have an important economic potential in terms of unexploited values. Within the scope of this study tailing samples have been taken from a privately owned flotation facility which is operating in Mugla Turkey in order to characterization and investigation of recovery possibilities of titanium minerals from feldspar tailings. Physical, chemical and mineralogical characterization studies and laboratory scaled beneficiation tests with gravity methods have been conducted on these samples. Effects of some parameters on efficiency of beneficiation have been investigated within the scope of beneficiation tests carried out with shaking table and multi gravity separator. As a result of characterization studies, it was determined that feed sample contains TiO2 at the rate of 1.90% and TiO2 content is associated to rutile mineral to a large extent. As a result of beneficiation tests; a concentrate that containing 11.26% TiO2 with a 50.43% rate of recovery were obtained in the shaking table tests and a concentrate that containing 17.11% TiO2 with a 89.33% rate of recovery were obtained in the MGS tests by using optimum conditions. In consideration of results obtained it is presented that gravity methods are able to be used as method of a pre-beneficiation in the recovery of titanium minerals from feldspar tailings