An Exactly Solvable Phase-Field Theory of Dislocation Dynamics, Strain Hardening and Hysteresis in Ductile Single Crystals

An exactly solvable phase-field theory of dislocation dynamics, strain hardening and hysteresis in ductile single crystals is developed. The theory accounts for: an arbitrary number and arrangement of dislocation lines over a slip plane; the long-range elastic interactions between dislocation lines; the core structure of the dislocations resulting from a piecewise quadratic Peierls potential; the interaction between the dislocations and an applied resolved shear stress field; and the irreversible interactions with short-range obstacles and lattice friction, resulting in hardening, path dependency and hysteresis. A chief advantage of the present theory is that it is analytically tractable, in the sense that the complexity of the calculations may be reduced, with the aid of closed form analytical solutions, to the determination of the value of the phase field at point-obstacle sites. In particular, no numerical grid is required in calculations. The phase-field representation enables complex geometrical and topological transitions in the dislocation ensemble, including dislocation loop nucleation, bow-out, pinching, and the formation of Orowan loops. The theory also permits the consideration of obstacles of varying strengths and dislocation line-energy anisotropy. The theory predicts a range of behaviors which are in qualitative agreement with observation, including: hardening and dislocation multiplication in single slip under monotonic loading; the Bauschinger effect under reverse loading; the fading memory effect, whereby reverse yielding gradually eliminates the influence of previous loading; the evolution of the dislocation density under cycling loading, leading to characteristic `butterfly' curves; and others

Formal Study of a Novel Network Role-based Routing Intelligent Algorithm

AbstractNORIA (Network rOle-based Routing Intelligent Algorithm) is a novel routing algorithm for Wireless Sensor Networks (WSNs) which combines various effective techniques in order to reduce energy consumption and improve data routes. This paper presents a formal and rigorous study of NORIA. Prioritised-Timed Coloured Petri Nets (PTCPNs) have been used to describe complete and unambiguous specifications of system behaviour, whereas CPNTools is used to evaluate the correctness of the protocol using state space exploration

Other-regarding preferences and the decision behaviour of autistic people in the Ultimatum Game

When humans interact with one another, the decisions they make often appear to be irrational in a purely economic sense. People are willing to sacrifice resources in order to affect positive outcomes for others and they often forgo opportunities to maximise benefits for themselves in order to avoid disadvantaging others. Explanations for such phenomena remain contested. The current thesis seeks to shed light on some of the factors that contribute to social-decision making by comparing decision making in typically developing individuals and individuals diagnosed with autism spectrum disorder – a condition characterised by difficulties in many of the domains that are suspected to play a role in guiding social-decision behaviour. In four experiments, variants of a paradigm known as the Ultimatum Game were implemented, which requires individuals to decide whether or not to accept or reject fair or unfair monetary offers. In Experiment 1, a one-shot UG was implemented in which participants provided one response as proposer and one as responder. In experiment 2, as responders, participants were asked to decide over intentionally vs randomly made unfair offers while skin conductance response was measured. In experiment 3, a cognitive manipulation was implemented, and participants were asked to respond with and without time pressure to fair and unfair offers made by human proposers. Finally, in experiment 4 participants played as proposers and responders a multi trial Mini UG. Here, participants decide over an unfair offer which is presented four times along with an alternative offer that varies in levels of fairness each time. In addition, across all experiments a number of traits, that are thought to play a role in regulating decision behaviour in this scenario were assessed through self-report and performance measures, including theory of mind, inhibition, empathising and systemising. The results from the Ultimatum Game task showed that there are no substantial behavioural differences between ASD and control participants (TD). However, in two of the experiments, differences emerged which suggested that the two groups differed in the cognitive processes recruited to respond to levels of fairness. Specifically, in experiment 2 ASD participants were less influenced by whether or not unfair offers were proposed by a human or computer counterpart and in experiment 3 rejection rates were more strongly associated with a measure of theory of mind than in the TD group. These results are discussed in the framework of cognitive theories of ASD and models of economic exchange suggesting that inequity aversion, e.g. Cultural norms, and fairness reciprocity are not stable preferences but differently motivate decision behaviour depending on the context. Further research needs to be undertaken to identify how executive control and dual theories of moral judgements affect decision behaviour in repeated interactions

Identification and Functional Distribution of Intracellular Ca2+ Channels in Mouse Lacrimal Gland Acinar Cells

We have determined the presence and cellular distribution of intracellular calcium channels, inositol 1, 4, 5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) in adult and postnatal (P10) lacrimal gland acinar cells. Western blot analysis of both P10 cultures and adult tissue identified the presence of each IP3R and RyR isotypes. The immunocytochemistry analysis showed a differential cellular distribution of these calcium channels where the nuclear envelope, endoplasmic reticulum (ER) and Golgi apparatus membranes represent areas with highest levels of channel expression. This IP3R and RyR isotype distribution is confirmed by the immuno-EM results. The findings described in this study are in agreement with published pharmacological data that shows the participation of these channels in the secretion process of the lacrimal gland acinar cells. Furthermore, the differential subcellular distribution between the isoforms could indicate a potential role of these intracellular Ca2+ channels on the regulation of specific cellular functions

Influence of Polarity and Activation Energy in Microwave-Assisted Organic Synthesis (MAOS)

The aim of this work was to determine the parameters that have decisive roles in microwave-assisted reactions and to develop a model, using computational chemistry, to predict a priori the type of reactions that can be improved under microwaves. For this purpose, a computational study was carried out on a variety of reactions, which have been reported to be improved under microwave irradiation. This comprises six types of reactions. The outcomes obtained in this study indicate that the most influential parameters are activation energy, enthalpy, and the polarity of all the species that participate. In addition to this, in most cases, slower reacting systems observe a much greater improvement under microwave irradiation. Furthermore, for these reactions, the presence of a polar component in the reaction (solvent, reagent, susceptor, etc.) is necessary for strong coupling with the electromagnetic radiation. We also quantified that an activation energy of 20-30 kcal mol-1 and a polarity (µ) between 7-20 D of the species involved in the process is required to obtain significant improvements under microwave irradiation

Dynamics of fluctuations in a fluid below the onset of Rayleigh-B\'enard convection

We present experimental data and their theoretical interpretation for the decay rates of temperature fluctuations in a thin layer of a fluid heated from below and confined between parallel horizontal plates. The measurements were made with the mean temperature of the layer corresponding to the critical isochore of sulfur hexafluoride above but near the critical point where fluctuations are exceptionally strong. They cover a wide range of temperature gradients below the onset of Rayleigh-B\'enard convection, and span wave numbers on both sides of the critical value for this onset. The decay rates were determined from experimental shadowgraph images of the fluctuations at several camera exposure times. We present a theoretical expression for an exposure-time-dependent structure factor which is needed for the data analysis. As the onset of convection is approached, the data reveal the critical slowing-down associated with the bifurcation. Theoretical predictions for the decay rates as a function of the wave number and temperature gradient are presented and compared with the experimental data. Quantitative agreement is obtained if allowance is made for some uncertainty in the small spacing between the plates, and when an empirical estimate is employed for the influence of symmetric deviations from the Oberbeck-Boussinesq approximation which are to be expected in a fluid with its density at the mean temperature located on the critical isochore.Comment: 13 pages, 10 figures, 52 reference

Confinement Effects in Antiferromagnets

Phase equilibrium in confined Ising antiferromagnets was studied as a function of the coupling (v) and a magnetic field (h) at the surfaces, in the presence of an external field H. The ground state properties were calculated exactly for symmetric boundary conditions and nearest-neighbor interactions, and a full zero-temperature phase diagram in the plane v-h was obtained for films with symmetry-preserving surface orientations. The ground-state analysis was extended to the H-T plane using a cluster-variation free energy. The study of the finite-T properties (as a function of v and h) reveals the close interdependence between the surface and finite-size effects and, together with the ground-state phase diagram, provides an integral picture of the confinement in anisotropic antiferromagnets with surfaces that preserve the symmetry of the order parameter.Comment: 10 pages, 8 figures, Accepted in Phys. Rev.

The Bond-Algebraic Approach to Dualities

An algebraic theory of dualities is developed based on the notion of bond algebras. It deals with classical and quantum dualities in a unified fashion explaining the precise connection between quantum dualities and the low temperature (strong-coupling)/high temperature (weak-coupling) dualities of classical statistical mechanics (or (Euclidean) path integrals). Its range of applications includes discrete lattice, continuum field, and gauge theories. Dualities are revealed to be local, structure-preserving mappings between model-specific bond algebras that can be implemented as unitary transformations, or partial isometries if gauge symmetries are involved. This characterization permits to search systematically for dualities and self-dualities in quantum models of arbitrary system size, dimensionality and complexity, and any classical model admitting a transfer matrix representation. Dualities like exact dimensional reduction, emergent, and gauge-reducing dualities that solve gauge constraints can be easily understood in terms of mappings of bond algebras. As a new example, we show that the (\mathbb{Z}_2) Higgs model is dual to the extended toric code model {\it in any number of dimensions}. Non-local dual variables and Jordan-Wigner dictionaries are derived from the local mappings of bond algebras. Our bond-algebraic approach goes beyond the standard approach to classical dualities, and could help resolve the long standing problem of obtaining duality transformations for lattice non-Abelian models. As an illustration, we present new dualities in any spatial dimension for the quantum Heisenberg model. Finally, we discuss various applications including location of phase boundaries, spectral behavior and, notably, we show how bond-algebraic dualities help constrain and realize fermionization in an arbitrary number of spatial dimensions.Comment: 131 pages, 22 figures. Submitted to Advances in Physics. Second version including a new section on the eight-vertex model and the correction of several typo