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Metal additive manufacturing techniques typically operate using powders with limited particle size ranges, but atomisation processes produce significant amounts of particles outside these ranges, resulting in an accumulation of out-of-size specification metal powders without a clear use case. Field-assisted sintering technology (FAST) can provide an alternative, solid-state processing route to consolidate these powders into billets for subsequent processing, or directly into near-net shape components. In this study, surplus powders of A20X, an aerospace approved aluminium alloy developed by Aluminium Materials Technologies (ECKART GmbH), were processed using FAST and subsequently hot rolled to produce sheet material. Tensile properties were similar to hot rolled conventional cast material and comparable to additively manufactured product. This indicates that FAST is an effective option for converting surplus metal powders into useful products, while improving sustainability in the additive supply chain. [ABSTRACT FROM AUTHOR]

The small punch (SP) test is a widely accepted methodology for obtaining mechanical property information from limited material quantities. Much research has presented the creep, tensile and fracture responses of numerous materials gathered from small-scale testing approaches. This is of particular interest for alloy down selection of next-generation materials and in situ mechanical assessments. However, to truly understand the evolution of deformation of the miniature disc specimen, an accurate and detailed understanding of the progressive damage is necessary. This paper will utilise the SP test to assess the tensile properties of several Ti-6Al-4V materials across different temperature regimes. Fractographic investigations will establish the contrasting damage mechanisms and finite element modelling through DEFORM software is employed to characterise specimen deformation. [ABSTRACT FROM AUTHOR]

We reveal the nature of the avalanche collapse of the giant viable component in multiplex networks under perturbations such as random damage. Specifically, we identify latent critical clusters associated with the avalanches of random damage. Divergence of their mean size signals the approach to the hybrid phase transition from one side, while there are no critical precursors on the other side. We find that this discontinuous transition occurs in scale-free multiplex networks whenever the mean degree of at least one of the interdependent networks does not diverge. [ABSTRACT FROM AUTHOR]

We introduce the heterogeneous k-core, which generalizes the k-core, and contrast it with bootstrap percolation. Vertices have a threshold ri that may be different at each vertex. If a vertex has fewer than ri neighbors it is pruned from the network. The heterogeneous k-core is the subgraph remaining after no further vertices can be pruned. If the thresholds ri are 1 with probability ƒ, or k ⩾ 3 with probability 1 - ƒ, the process can be thought of as a pruning process counterpart to ordinary bootstrap percolation, which is an activation process. We show that there are two types of transitions in this heterogeneous k-core process: the giant heterogeneous k-core may appear with a continuous transition and there may be a second discontinuous hybrid transition. We compare critical phenomena, critical clusters, and avalanches at the heterogeneous k-core and bootstrap percolation transitions. We also show that the network structure has a crucial effect on these processes, with the giant heterogeneous k-core appearing immediately at a finite value for any ƒ > 0 when the degree distribution tends to a power law P(q) ∼ q-γ with γ < 3. [ABSTRACT FROM AUTHOR]

Predictions of residual stresses in inertia friction welded Ni-base superalloys have been carried out using a commercial finite element code (DEFORM) combined with an energy balance approach and a 2D axisymmetric formulation. A coupled thermal and mechanical finite element model has been created. During inertia welding trials of RR1000, a high Υ ' Ni-base superalloy, the rotational velocity and upset history curves were recorded. From these data the heat flux (the rate of energy input) through the weld interface was inferred and together with the upsetting rate input into the model as evolving boundary conditions. The coupled thermal and mechanical analysis leads to the prediction of the thermal history and the residual stresses generated during cooling. The validation of the model has been undertaken by comparing the predicted residual stresses with those measured using neutron diffraction. The comparison between predicted and measured stresses is in good agreement. [ABSTRACT FROM AUTHOR]

Background Salicylic acid (SA) is present in the serum of people who have not taken salicylate drugs. Now we have examined the urine of these subjects and found that it contains SA and salicyluric acid (SU). We have established the identities of these phenolic acids and determined their concentrations. Methods and Results The acidic hydrophobic compounds of urine were separated using high-performance liquid chromatography (HPLC) and were detected and quantified electrochemically. Two approaches were used to establish the identity of SA and SU. First, the retention times (Rt) of the substances extracted and those of SA and SU were compared under two sets of chromatographic conditions; the Rt of the compounds suspected to be SA and SU and those of the authentic substances were very similar under both sets of conditions. Second, the unknown substances, isolated by HPLC, were treated with acetyl chloride in methanol and compared with the methyl esters of SA and SU by using gas chromatography-mass spectrometry; the unknown compounds after esterification had very similar mass spectra and gas chromatographic Rt to those of methyl salicylate and methyl salicylurate. The median (n = 10) urinary concentration of SA was 0·56 μmol/L (range 0·07-0·89 μmol/L) and that of SU was 3·20 μmol/L (range 1·32-6·54 μmol/L). SA and its major urinary metabolite, SU, were found in the urine of all of the 10 people examined. [ABSTRACT FROM AUTHOR]

Compression, filtering, and cryptography, as well as the sampling of complex systems, can be seen as processing information. A large initial configuration or input space is nontrivially mapped to a smaller set of output or final states. We explored the statistics of filtering of simple patterns on a number of deterministic and random graphs as a tractable example of such information processing in complex systems. In this problem, multiple inputs map to the same output, and the statistics of filtering is represented by the distribution of this degeneracy. For a few simple filter patterns on a ring, we obtained an exact solution of the problem and numerically described more difficult filter setups. For each of the filter patterns and networks, we found three key numbers that essentially describe the statistics of filtering and compared them for different networks. Our results for networks with diverse architectures are essentially determined by two factors: whether the graphs structure is deterministic or random and the vertex degree. We find that filtering in random graphs produces much richer statistics than in deterministic graphs, reflecting the greater complexity of such graphs. Increasing the graph's degree reduces this statistical richness, while being at its maximum at the smallest degree not equal to two. A filter pattern with a strong dependence on the neighbourhood of a node is much more sensitive to these effects. [ABSTRACT FROM AUTHOR]

Complex systems consisting of interdependent subsystems may be represented by multilayer networks with interdependency links between layers. The giant mutually connected component (GMCC) of such an interdependent (or multiplex) network collapses with a discontinuous hybrid transition under random damage to the network. If the nodes to be damaged are selected in a targeted way, the collapse of the GMCC may occur significantly sooner. Understanding the limits of the resilience of such systems to targeted attacks is therefore an essential problem. Finding the minimal damage set which destroys the largest mutually connected component of a given interdependent network is a computationally prohibitive simultaneous optimization problem. We introduce a simple heuristic strategy--effective multiplex degree--for targeted attack on interdependent networks that leverages the indirect damage inherent in multiplex networks to achieve a damage set smaller than that found by any existing noncomputationally intensive algorithm. We show that the intuition from single-layer networks that decycling (damage of the 2-core) is the most effective way to destroy the giant component does not carry over to interdependent networks and in fact such approaches are worse than simply removing the highest degree nodes. [ABSTRACT FROM AUTHOR]

We consider the effect of a nonvanishing fraction of initially infected nodes (seeds) on the susceptible-infected-recovered epidemic model on random networks. This is relevant when the number of arriving infected individuals is large, or to the spread of ideas with publicity campaigns. This model is frequently studied by mapping to a bond percolation problem, in which edges are occupied with the probability p of eventual infection along an edge. This gives accurate measures of the final size of the infection and epidemic threshold in the limit of a vanishingly small seed fraction. We show, however, that when the initial infection occupies a nonvanishing fraction, f, of the network, this method yields ambiguous results, as the correspondence between edge occupation and contagion transmission no longer holds. We propose instead to measure the giant component of recovered individuals within the original contact network. We derive exact equations for the size of the epidemic and the epidemic threshold in the infinite size limit in heterogeneous sparse random networks, and we confirm them with numerical results. We observe that the epidemic threshold correctly depends on f, decreasing as f increases. When the seed fraction tends to zero, we recover the standard results.

We describe the critical behavior of weak multiplex percolation, a generalization of percolation to multiplex or interdependent networks. A node can determine its active or inactive status simply by referencing neighboring nodes. This is not the case for the more commonly studied generalization of percolation to multiplex networks, the mutually connected clusters, which requires an interconnecting path within each layer between any two vertices in the giant mutually connected component. We study the emergence of a giant connected component of active nodes under the weak percolation rule, finding several nontypical phenomena. In two layers, the giant component emerges with a continuous phase transition, but with quadratic growth above the critical threshold. In three or more layers, a discontinuous hybrid transition occurs, similar to that found in the giant mutually connected component. In networks with asymptotically powerlaw degree distributions, defined by the decay exponent γ, the discontinuity vanishes but at γ=1.5 in three layers, more generally at γ=1+1/(M-1) in M layers.

We consider bootstrap percolation on uncorrelated complex networks. We obtain the phase diagram for this process with respect to two parameters: f, the fraction of vertices initially activated, and p, the fraction of undamaged vertices in the graph. We observe two transitions: the giant active component appears continuously at a first threshold. There may also be a second, discontinuous, hybrid transition at a higher threshold. Avalanches of activations increase in size as this second critical point is approached, finally diverging at this threshold. We describe the existence of a special critical point at which this second transition first appears. In networks with degree distributions whose second moment diverges (but whose first moment does not), we find a qualitatively different behavior. In this case the giant active component appears for any f>0 and p>0, and the discontinuous transition is absent. This means that the giant active component is robust to damage, and also is very easily activated. We also formulate a generalized bootstrap process in which each vertex can have an arbitrary threshold.

We investigate a set of stochastic models of biodiversity, population genetics, language evolution, and opinion dynamics on a network within a common framework. Each node has a state 0

We give an exact solution to the Kolmogorov equation describing genetic drift for an arbitrary number of alleles at a given locus. This is achieved by finding a change of variable which makes the equation separable, and therefore reduces the problem with an arbitrary number of alleles to the solution of a set of equations that are essentially no more complicated than that found in the two-allele case. The same change of variable also renders the Kolmogorov equation with the effect of mutations added separable, as long as the mutation matrix has equal entries in each row. Thus, this case can also be solved exactly for an arbitrary number of alleles. The general solution, which is in the form of a probability distribution, is in agreement with the previously known results. Results are also given for a wide range of other quantities of interest, such as the probabilities of extinction of various numbers of alleles, mean times to these extinctions, and the means and variances of the allele frequencies. To aid dissemination, these results are presented in two stages: first of all they are given without derivations and too much mathematical detail, and then subsequently derivations and a more technical discussion are provided.

We present a mathematical formulation of a theory of language change. The theory is evolutionary in nature and has close analogies with theories of population genetics. The mathematical structure we construct similarly has correspondences with the Fisher-Wright model of population genetics, but there are significant differences. The continuous time formulation of the model is expressed in terms of a Fokker-Planck equation. This equation is exactly soluble in the case of a single speaker and can be investigated analytically in the case of multiple speakers who communicate equally with all other speakers and give their utterances equal weight. Whilst the stationary properties of this system have much in common with the single-speaker case, time-dependent properties are richer. In the particular case where linguistic forms can become extinct, we find that the presence of many speakers causes a two-stage relaxation, the first being a common marginal distribution that persists for a long time as a consequence of ultimate extinction being due to rare fluctuations.

Background: Salicylic acid is a chemical signal in plants infected by pathogens and it is responsible for the anti-inflammatory action of aspirin. Patients who take aspirin have a reduced risk of developing atherosclerosis and colorectal cancer, both of these pathologies having an inflammatory component. Dietary salicylic acid may help to prevent these conditions. We wondered if foods made from organically-reared plants might have a higher content of salicylic acid than those made from non-organic plants, since the latter are more likely to be protected from infection by the application of pesticides., Objective: To determine if organic vegetable soups have a higher salicylic acid content than non-organic vegetable soups., Methods: The contents of salicylic acid in organic and non-organic vegetable soups purchased from supermarkets were determined. Salicylic acid was identified by varying the chromatographic conditions and comparing the retention times of the unknown substance in the extracts with salicylic acid; by treating extracts of the soups with salicylate hydroxylase; and by using GCMS. Salicylic acid was determined by using HPLC with electrochemical detection., Results: Salicylic acid was present in all of the organic and most of the non-organic vegetable soups. The median contents of salicylic acid in the organic and non-organic vegetable soups were 117 (range, 8-1040) ng x g(-1) and 20 (range, 0-248) ng x g(-1) respectively. The organic soups had a significantly higher content of salicylic acid (p=0.0032 Mann Whitney U test), with a median difference of 59 ng g(-1) (95 % confidence interval, 18-117ng x g(-1))., Conclusions: Organic vegetable soups contained more salicylic acid than non-organic ones, suggesting that the vegetables and plants used to prepare them contained greater amounts of the phenolic acid than the corresponding non-organic ingredients. Consumption of organic foods may result in a greater intake of salicylic acid.

The purpose of this study was to determine what subunits of the glutamate (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)) receptor are expressed by sympathetic preganglionic neurons in the spinal cord of adult rats. Preganglionic neurons were retrogradely labelled with Fluorogold, double-labelled with choline acetyltransferase immunofluorescence, and examined with confocal microscopy for evidence of immunoreactivity for GluR1, GluR2, GluR2/3 and GluR4 subunits. Quantitative analysis revealed that 92, 63 and 85% of preganglionic cells in the T8 segment express GluR1, GluR2 and GluR2/3 subunits, respectively. Cells were not immunoreactive for the GluR4 subunit. This evidence is consistent with the idea that most sympathetic preganglionic neurons form heteromeric AMPA receptors. Cells with GluR2 subunits will assemble receptors which are impermeable to calcium ions and may be resistant to excitotoxic cell death.

Changes in the neuropeptide expression of sensory neurons, related to functional modulation, have been widely reported both following physical injury in vivo, and after toxic insult in vitro and in vivo. The current immunocytochemical study aimed to monitor the neuropeptide status of neuronal cultures prepared from adult mouse dorsal root ganglia (DRG), and to ascertain whether changes occurred following treatments with 0.1-1 microM methylmercury (MeHg). Proportions of both substance P (SP) and calcitonin gene related peptide (CGRP) containing neurons increased significantly, and were maintained throughout the 24 h exposure period. In contrast the numbers of somatostatin (SOM)-ir neurons decreased. Substance P- and CGRP-ir neuron increases may be related to nociceptive responses, whereas the decreases in SOM containing neurons could reflect a differential loss in this subset of sensory neurons.