Micropolar hyperelasticity: constitutive model, consistent linearization and simulation of 3D scale effects

This study describes a computational framework for three-dimensional finite strain and finite curvature micropolar hyperelasticity. The model is based on the non-linear kinematic setting and features an appropriate hyperelastic material law which is derived within the thermodynamically consistent framework. The material tangent operator is obtained by consistent linearization. An implicit finite element method with a Newton-Raphson procedure is employed for the computation of the nodal displacements and rotations. A number of numerical examples is presented. The results demonstrate (i) that the methodology is capable of capturing 3D length scale effects in finite deformation, (ii) that it is robust and computationally efficient and (iii) that the proposed micropolar element tangent renders asymptotically quadratic convergence of the Newton-Raphson procedure. It is shown that the classical Neo-Hooke type material behaviour is recovered as a special case within the proposed micropolar setting.     

Optimal log-polar image sampling

In order to achieve better image compression simultaneously maintaining the high signal quality, the image sampling has become very important. Also, since the human eye sensitivity has circularly symmetric distribution, in recent years it is usual to apply log-polar image sampling. In this paper, we perform optimization of log-polar image sampling and show the significant improvement in comparison with the product log-polar sampling. Namely, for equal numbers of sensors optimal model gives higher signal-to-noise ratio (SNR) up to 2.5 dB, i.e., it is possible to decrease the number of required sensors by 45% for the same SNR. Furthermore, research shows that in optimal log-polar image sampling, the middle region of image, which is not sampled, can be made to be smaller than in the case of product sampling.     

Modelling surface radioactive,chemical and oil spills in the Strait of Gibraltar

A model that simulates the dispersion of chemical/radioactive and oil spills in the Strait of Gibraltar has been developed. Water currents over the Strait have been obtained from a hydrodynamic model. Computed tides and residual currents have been compared with observations in the area. The dispersion model, based on a particle-tracking technique, is solved off-line. Standard tidal analysis, carried out over results provided by the hydrodynamic model, is applied to obtain currents at any time and position of the Strait. Specific processes for each contaminant (decay of radioactive material, oil evaporation and decomposition) are included and simulated by means of a stochastic method. A Monte Carlo method is applied for turbulent diffusion. The model can deal with instantaneous and continuous releases. MatLab graphic user interfaces have been developed to introduce input data and visualize simulation results. Some dispersion calculations have been carried out. In general, contaminants are flushed towards the east due to the residual currents. Nevertheless, dominant east winds tend to retain contamination in the Strait and to enhance mixing. This is also the case if the release occurs close to the coast, where currents are weaker than in the central part of the Strait.     

A Quorum-Based Group Mutual Exclusion Algorithm for a Distributed System with Dynamic Group Set

The group mutual exclusion problem extends the traditional mutual exclusion problem by associating a type (or a group) with each critical section. In this problem, processes requesting critical sections of the same type can execute their critical sections concurrently. However, processes requesting critical sections of different types must execute their critical sections in a mutually exclusive manner. We present a distributed algorithm for solving the group mutual exclusion problem based on the notion of surrogate-quorum. Intuitively, our algorithm uses the quorum that has been successfully locked by a request as a surrogate to service other compatible requests for the same type of critical section. Unlike the existing quorum-based algorithms for group mutual exclusion, our algorithm achieves a low message complexity of O(q) and a low (amortized) bit-message complexity of O(bqr), where q is the maximum size of a quorum, b is the maximum number of processes from which a node can receive critical section requests, and r is the maximum size of a request while maintaining both synchronization delay and waiting time at two message hops. As opposed to some existing quorum-based algorithms, our algorithm can adapt without performance penalties to dynamic changes in the set of groups. Our simulation results indicate that our algorithm outperforms the existing quorum-based algorithms for group mutual exclusion by as much as 45 percent in some cases. We also discuss how our algorithm can be extended to satisfy certain desirable properties such as concurrent entry and unnecessary blocking freedom.     

Lack of influence of the phase of estrus cycle or treatment with steroid contraceptive drugs on cholinergic parameters in mouse and rat brain

Acetylcholine and choline levels were found not to fluctuate with the phase of the estrus cycle in the cerebral hemispheres, deincephalon and mesencephalon in the rat and mouse. Choline acetyltransferase activity was not altered in these brain areas in the mouse while in the rat there was a small but significant decrease in the cerebral hemispheres during proestrus (p less than 0.01), and in the mesencephalon during estrus (p less than 0.05), both with respect to diestrus. Chronic 30-day treatment with steroid contraceptive drug combinations (lynestrenol, 5 mg/kg+ mestranol, 0.3 mg/kg; lynestrenol, 2.5 mg/kg+ mestranol, 0.15 mg/kg; norethindrone, 4 mg/kg+ mestranol, 0.2 mg/kg; norethynodrel, 4 mg/kg+ mestranol, 0.06 mg/kg) did not alter cholinergic parameters in the brain areas of these two species except for minor changes in rare instances.     

De novo conditioning in trauma-exposed individuals with and without posttraumatic stress disorder.

Differential conditioning was assessed in 15 medication-free individuals meeting Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) criteria for chronic posttraumatic stress disorder (PTSD) and 18 trauma-exposed individuals who never developed PTSD (non-PTSD). Conditioned stimuli (CSs) were colored circles, and the unconditioned stimulus was a "highly annoying" electrical stimulus. Individuals with PTSD had higher resting heart rate (HR) and skin conductance (SC) levels and produced larger SC orienting responses. During conditioning, the PTSD group showed larger differential SC, HR, and electromyogrant responses to the reinforced vs. nonreinforced stimuli (CS+ vs. CS-) compared with the non-PTSD group. Only PTSD participants continued to show differential SC responses to CS+ vs. CS- during extinction trials. Results suggest that individuals with PTSD have higher sympathetic nervous system arousal at the time of conditioning and are more conditionable than trauma-exposed individuals without PTSD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An Improved/Optimized Practical Non-Blocking PageRank Algorithm for Massive Graphs*

International Journal of Parallel Programming - PageRank kernel is a standard benchmark addressing various graph processing and analytical problems. The PageRank algorithm serves as a standard for...     

Characterisation of black cumin,pomegranate and flaxseed meals as sources of phenolic acids

The article focuses on the extraction of ten phenolic acids from black cumin (Nigella sativa L.), pomegranate (Punica granatum L.) and flax (Linum usitatissimum L.) seed meals. The extracts have been fractionated as free, esterified and insoluble‐bound phenolic compounds and quantitatively determined by HPLC–PDA. The analysed meals can be utilised for obtaining valuable phenolic acids. However, the distribution of phenolic compounds varies depending on the meal source. The insoluble‐bound fraction has been the richest for the black cumin meal, both qualitatively and quantitatively, containing all ten analysed phenolics. In the pomegranate meal, the main phenolic has been gallic acid, accounting for nearly 48% in free form. The esterified form of the flaxseed meal has been abundant with ferulic (1025.44 ± 3.99 mg kg^?1 dry weight), caffeic and p‐coumaric acids. The total amount of phenolic acids would be underestimated if only free fractions would be taken into account, while neglecting esterified (for the pomegranate and flax meals) and insoluble‐bound fractions (for the black cumin and pomegranate meals).     

Interaction of heavy metal ions with an ion exchange resin obtained from a natural polyelectrolyte

An ion exchange resin was synthesized by using a natural polyelectrolyte, sodium alginate, and barium ion as a cross-linker reagent. Resin was characterized by TGA and SEM. Equilibrium and kinetic experiments of Pb²⁺, Hg²⁺, Ni²⁺, Co²⁺, Fe²⁺, and Fe³⁺ ions uptake by barium alginate beads were carried out in batch-type experiments under different values of pH. The removal efficiency increases with increasing pH. The uptake of metal ions occurs rapidly in the first hour. Maximum retention capacity was also determined being Fe(II) > Fe(III) > Co(II) > Ni(II) > Pb(II) > Hg(II) in mmol/g dry beads basis. Elution from the loaded resins at maximum capacity was studied by using HCl and HNO₃ as eluents at different concentrations.