Second-gradient plane deformations of ideal fibre-reinforced materials: implications of hyper-elasticity theory

The influence that some new, second-gradient, effects introduced in a recent publication (Spencer and Soldatos, Int J Non-linear Mech 42:355-368, 2007) have on finite plane deformations of ideal fibre-reinforced hyper-elastic solids is investigated. The second-gradient effects are due to the ability of the fibres to resist bending but, in the present case, the constraints of material incompressibility and fibre inextensibility associated with this ideal class of materials offer considerable theoretical simplification. In agreement with its conventional counterpart, where inextensible fibres are perfectly flexible, the present new theoretical development is still associated with kinematics and reaction stresses that are largely independent of the specific type of material behaviour considered. Static equilibrium considerations reveal therefore a manner in which relevant, non-symmetric stress distributions can be determined by solving two simultaneous, first-order linear differential equations. However, the principal interest of this investigation remains within the class of hyper-elastic materials for which two sets of relatively simple constitutive equations are obtained. At this stage of early theoretical development, immediate interest is directed towards the simplest of those sets, namely the set associated with problems where only gradients relevant to the change of the deformed fibre direction are of principal importance. These developments are applied (i) to the classical problem of plane-strain bending of a rectangular block reinforced by a family of straight fibres running parallel to one of its sides; and (ii) to the problem of “area-preserving” azimuthal shear strain of a circular cylindrical tube having its cross-section reinforced by a family of strong fibres. In the particular case in which the fibres are initially straight and aligned with the radii of the tube cross-section, the solution of the latter problem, which is new in the literature, reveals that fibres resist local bending completely. Instead, they remain straight during deformation and force the tube cross-section to undergo area-preserving azimuthal shear by changing their direction.     

The Human In Vivo Biomolecule Corona onto PEGylated Liposomes: A Proof‐of‐Concept Clinical Study

The self‐assembled layered adsorption of proteins onto nanoparticle (NP) surfaces, once in contact with biological fluids, is termed the “protein corona” and it is gradually seen as a determinant factor for the overall biological behavior of NPs. Here, the previously unreported in vivo protein corona formed in human systemic circulation is described. The human‐derived protein corona formed onto PEGylated doxorubicin‐encapsulated liposomes (Caelyx) is thoroughly characterized following the recovery of liposomes from the blood circulation of ovarian carcinoma patients. In agreement with previous investigations in mice, the in vivo corona is found to be molecularly richer in comparison to its counterpart ex vivo corona. The intravenously infused liposomes are able to scavenge the blood pool and surface‐capture low‐molecular‐weight, low‐abundance plasma proteins that cannot be detected by conventional plasma proteomic analysis. This study describes the previously elusive or postulated formation of protein corona around nanoparticles in vivo in humans and illustrates that it can potentially be used as a novel tool to analyze the blood circulation proteome.     

Graphene in the Design and Engineering of Next‐Generation Neural Interfaces

Neural interfaces are becoming a powerful toolkit for clinical interventions requiring stimulation and/or recording of the electrical activity of the nervous system. Active implantable devices offer a promising approach for the treatment of various diseases affecting the central or peripheral nervous systems by electrically stimulating different neuronal structures. All currently used neural interface devices are designed to perform a single function: either record activity or electrically stimulate tissue. Because of their electrical and electrochemical performance and their suitability for integration into flexible devices, graphene‐based materials constitute a versatile platform that could help address many of the current challenges in neural interface design. Here, how graphene and other 2D materials possess an array of properties that can enable enhanced functional capabilities for neural interfaces is illustrated. It is emphasized that the technological challenges are similar for all alternative types of materials used in the engineering of neural interface devices, each offering a unique set of advantages and limitations. Graphene and 2D materials can indeed play a commanding role in the efforts toward wider clinical adoption of bioelectronics and electroceuticals.     

Flexible least squares for temporal data mining and statistical arbitrage

A number of recent emerging applications call for studying data streams, potentially infinite flows of information updated in real-time. When multiple co-evolving data streams are observed, an important task is to determine how these streams depend on each other, accounting for dynamic dependence patterns without imposing any restrictive probabilistic law governing this dependence. In this paper we argue that flexible least squares (FLS), a penalized version of ordinary least squares that accommodates for time-varying regression coefficients, can be deployed successfully in this context. Our motivating application is statistical arbitrage, an investment strategy that exploits patterns detected in financial data streams. We demonstrate that FLS is algebraically equivalent to the well-known Kalman filter equations, and take advantage of this equivalence to gain a better understanding of FLS and suggest a more efficient algorithm. Promising experimental results obtained from a FLS-based algorithmic trading system for the S&P 500 Futures Index are reported.     

A multi-agent platform for content-based image retrieval

Efficient and possibly intelligent image retrieval is an important task, often required in many fields of human activity. While traditional database indexing techniques exhibit a remarkable performance in textual information retrieval current research in content-based image retrieval is focused on developing novel techniques that are biologically motivated and efficient. It is well known that humans have a remarkable ability to process visual information and to handle the volume and complexity of such information quite efficiently. In this paper, we present a content-based image retrieval platform that is based on a multi-agent architecture. Each agent is responsible for assessing the similarity of the query image to each candidate image contained in a collection based on a specific primitive feature and a corresponding similarity criterion. The outputs of various agents are integrated using one of several voting schemes supported by the system. The system’s performance has been evaluated using various collections of images, as well as images obtained in specific application domains such as medical imaging. The initial evaluation has yielded very promising results.

Domain filtering consistencies for non-binary constraints

In non-binary constraint satisfaction problems, the study of local consistencies that only prune values from domains has so far been largely limited to generalized arc consistency or weaker local consistency properties. This is in contrast with binary constraints where numerous such domain filtering consistencies have been proposed. In this paper we present a detailed theoretical, algorithmic and empirical study of domain filtering consistencies for non-binary problems. We study three domain filtering consistencies that are inspired by corresponding variable based domain filtering consistencies for binary problems. These consistencies are stronger than generalized arc consistency, but weaker than pairwise consistency, which is a strong consistency that removes tuples from constraint relations. Among other theoretical results, and contrary to expectations, we prove that these new consistencies do not reduce to the variable based definitions of their counterparts on binary constraints. We propose a number of algorithms to achieve the three consistencies. One of these algorithms has a time complexity comparable to that for generalized arc consistency despite performing more pruning. Experiments demonstrate that our new consistencies are promising as they can be more efficient than generalized arc consistency on certain non-binary problems.     

A connection between formation infeasibility and velocity alignment in kinematic multi-agent systems

In this paper, a feedback control strategy that achieves convergence of a multi-agent system to a desired formation configuration is proposed for both the cases of agents with single integrator and nonholonomic unicycle-type kinematics. When inter-agent objectives that specify the desired formation cannot occur simultaneously in the state space the desired formation is infeasible. It is shown that under certain assumptions, formation infeasibility forces the agents’ velocity vectors to a common value at steady state. This provides a connection between formation infeasibility and flocking behavior for the multi-agent system. We finally also obtain an analytic expression of the common velocity vector in the case of formation infeasibility.     

Two efficient solutions for visual odometry using directional correspondence

This paper presents two new, efficient solutions to the two-view, relative pose problem from three image point correspondences and one common reference direction. This three-plus-one problem can be used either as a substitute for the classic five-point algorithm, using a vanishing point for the reference direction, or to make use of an inertial measurement unit commonly available on robots and mobile devices where the gravity vector becomes the reference direction. We provide a simple, closed-form solution and a solution based on algebraic geometry which offers numerical advantages. In addition, we introduce a new method for computing visual odometry with RANSAC and four point correspondences per hypothesis. In a set of real experiments, we demonstrate the power of our approach by comparing it to the five-point method in a hypothesize-and-test visual odometry setting.     

Effects of varying levels of dietary free gossypol in whole cotton seed on physiological responses of growing–fattening lambs

Effects of increasing concentrations of free gossypol in diets containing up to 30% whole cottonseed on blood metabolites were studied using 32 Karagouniko male lambs in a 4 × 3 factorial arrangement with treatments of four whole cottonseed levels and three times of sampling. The diets used were isocaloric (12.5–13.1 MJ metabolisable energy kg⁻¹ dry matter) with 163–186 g crude protein kg⁻¹ dry matter containing 0%, 5–10%, 10–20% and 15–30% whole cottonseed and were fed ad libitum for 54 days. Blood samples were taken at the beginning, middle and end of the experiment. The blood parameters examined were: haematocrit, haemoglobin, mean corpuscular haemoglobin concentration, erythrocyte sedimentation rate, plasma glucose, urea, total protein, albumin and globulin concentrations and serum total and free cholesterol, cholesterol esters and inorganic K concentrations. In addition, the serum enzyme activities of glutamate pyruvate transaminase, γ-glutamyl transpeptidase and lactate dehydrogenase, as indicative of liver and heart muscle damage, and the concentrations of the major elements Ca, Mg and K and also of the trace elements Fe, Cu and Zn in liver, kidneys and heart of slaughtered lambs were estimated. This study was also made to determine the effect of whole cottonseed diets on the accumulation of free gossypol in some organs of growing lambs. Most of the blood components evaluated were affected by the diet fed. Blood haematocrit and erythrocyte sedimentation rate were higher at the beginning of the experiment, but haemoglobin and mean corpuscular haemoglobin concentrations were higher at day 28 of the experimental period; plasma total protein, urea, albumin and globulin concentrations and also serum total and free cholesterol and inorganic K concentrations were higher at day 54 of the experiment. The serum enzyme activities of glutamate pyruvate transaminase, γ-glutamyl transpeptidase and lactate dehydrogenase were all higher at day 54 of the experimental period. However, there were significant differences between treatments and between times of sampling in the three enzyme activities measured. Liver, kidneys and heart examination showed significant differences for all organs in NPN, fat, fat/protein ratio and the major elements Ca, Mg and K among the four treatments. However, of the trace elements examined, differences were significant for Fe in liver, Cu in heart and Zn in liver and heart. The greatest free gossypol accumulation was observed, as expected, in liver, followed by kidneys and lastly by heart. There was an indication of possible gossypol toxicity in these growing lambs as a result of the marked elevations of the activity of lactate dehydrogenase and possibly of the increase in plasma urea concentration. © 1999 Society of Chemical Industry