Fuzzy neural network methodology applied to medical diagnosis

This paper presents a technique for building expert systems that combines the fuzzy-set approach with artificial neural network structures. This technique can effectively deal with two types of medical knowledge: a nonfuzzy one and a fuzzy one which usually contributes to the process of medical diagnosis. Nonfuzzy numerical data is obtained from medical tests. Fuzzy linguistic rules describing the diagnosis process are provided by a human expert. The proposed method has been successfully applied in veterinary medicine as a support system in the diagnosis of canine liver diseases

Speed control with low armature loss for very small sensorless brushed DC motors

A method for speed control of brushed dc motors is presented. It is particularly applicable to motors with armatures of less than 1 cm3. Motors with very small armatures are difficult to control using the usual pulsewidth-modulation (PWM) approach and are apt to overheat if so driven. The technique regulates speed via the back electromotive force but does not require current-discontinuous drives. Armature heating in small motors under PWM drive is explained and quantified. The method is verified through simulation and measurement. Control is improved, and armature losses are minimized. The method can expect to find application in miniature mechatronic equipment

Entropy and Barrier-Hopping Determine Conformational Viscoelasticity in Single Biomolecules

Biological macromolecules have complex and non-trivial energy landscapes, endowing them a unique conformational adaptability and diversity in function. Hence, understanding the processes of elasticity and dissipation at the nanoscale is important to molecular biology and also emerging fields such as nanotechnology. Here we analyse single molecule fluctuations in an atomic force microscope (AFM) experiment using a generic model of biopolymer viscoelasticity that importantly includes sources of local `internal' conformational dissipation. Comparing two biopolymers, dextran and cellulose, polysaccharides with and without the well-known `chair-to-boat' transition, reveals a signature of this simple conformational change as minima in both the elasticity and internal friction around a characteristic force. A calculation of two-state populations dynamics offers a simple explanation in terms of an elasticity driven by the entropy, and friction by barrier-controlled hopping, of populations on a landscape. The microscopic model, allows quantitative mapping of features of the energy landscape, revealing unexpectedly slow dynamics, suggestive of an underlying roughness to the free energy.Comment: 25 pages, 7 figures, naturemag.bst, modified nature.cls (naturemodified.cls

How proteins' negative cooperativity emerges from entropic optimisation of versatile collective fluctuations

The fact that allostery, a nonlocal signaling between distant binding sites, can arise mainly from the entropy balance of collective thermal modes, without conformational changes, is by now well known. However, the propensity to generate negative cooperativity is still unclear. Starting from an elastic-network picture of small protein complexes, in which effector binding is modeled by locally altering interaction strengths in lieu of adding a node-spring pair, we elucidate mechanisms particularly for such negative cooperativity. The approach via a few coupled harmonic oscillators with internal elastic strengths allows us to trace individual eigenmodes, their frequencies, and their statistical weights through successive bindings. We find that the alteration of the oscillators' couplings is paramount to covering both signs of allostery. Binding-modified couplings create a rich set of eigenmodes individually for each binding state, modes inaccessible to an ensemble of noninteracting units. The associated shifts of collective-mode frequencies, nonuniform with respect to modes and binding states, result in an enhanced optimizability, reflected by a subtle phase map of allosteric behaviors

Shear flow effects on phase separation of entangled polymer blends

We introduce an entanglement model mixing rule for stress relaxation in a polymer blend to a modified Cahn-Hilliard equation of motion for concentration fluctuations in the presence of shear flow. Such an approach predicts both shear-induced mixing and demixing, depending on the relative relaxation times and plateau moduli of the two components

Phase Separation in Binary Fluid Mixtures with Continuously Ramped Temperature

We consider the demixing of a binary fluid mixture, under gravity, which is steadily driven into a two phase region by slowly ramping the temperature. We assume, as a first approximation, that the system remains spatially isothermal, and examine the interplay of two competing nonlinearities. One of these arises because the supersaturation is greatest far from the meniscus, creating inversion of the density which can lead to fluid motion; although isothermal, this is somewhat like the Benard problem (a single-phase fluid heated from below). The other is the intrinsic diffusive instability which results either in nucleation or in spinodal decomposition at large supersaturations. Experimental results on a simple binary mixture show interesting oscillations in heat capacity and optical properties for a wide range of ramp parameters. We argue that these oscillations arise under conditions where both nonlinearities are important

Molecular Dynamics Simulation of Dextran Extension by Constant Force in Single Molecule AFM

AbstractThe extension of 1–6 polysaccharides has been studied in a series of recent single molecule AFM experiments. For dextran, a key finding was the existence of a plateau in the force-extension curve at forces between 700 and 1000pN. We studied the extension of the dextran 10-mer under constant force using atomistic simulation with various force fields. All the force fields reproduce the experimental plateau on the force-extension curve. With AMBER94 and AMBER-GLYCAM04 force fields the plateau can be explained by a transition of the glucopyranose rings in the dextran monomers from the chair (4C1) to the inverted chair (1C4) conformation while other processes occur at smaller (rotation around C5-C6 bond) or higher (chairs to boat transitions) forces. The CHARMM force field provides a different picture which associates the occurrence of the plateau to chair-boat transitions of the glucopyranose rings