Engineering criterion for rupture of brittle particles in a ductile matrix including particle size and stress triaxiality effects

AbstractCatastrophic failure due to cleavage fracture is caused by the rapid propagation of a micro-crack in the vicinity of a macroscopic flaw. Micro-cracks are initiated at second-phase brittle particles, present in the steel in different sizes and distributed randomly in the volume. The current understanding is that such particles rupture when overloaded by the plastically deforming matrix. To predict the experimentally observed statistical nature of cleavage fracture under different constraint conditions, it is pertinent to develop a particle size and constraint dependent criterion for the failure of a brittle particle in a ductile matrix.In this work the failure energy of an elastic-brittle spherical particle in a ductile matrix is analysed. Several loading conditions were examined, from constrained-uniaxial through to plane strain with varying levels of constraint. To develop a size dependent condition, results for multiple particle radii were investigated within a fixed matrix volume. The particle and matrix were deformed initially; subsequently nodes along the particle mid-plane were released progressively imitating crack opening. The energy associated with particle rupture was determined from the change in reaction force before and after release and corresponding opening displacements.The results for each loading case show clear linear relation between rupture energy and particle size. Further the results show the dependence of rupture energy on constraint, with a distinct increase of failure probability with increasing constraint. Finally, an expression for particle rupture dependence on size, stress triaxiality, and plastic strain level is derived. It is intended that this model will then be used to advance continuum-based local approach models to cleavage and meso-scale models for distributed interacting micro-cracks

Recently published papers: Renal support in acute kidney injury - is low dose the new high dose?

Despite 21st century definitions, the management of acute kidney injury remains steadfastly rooted in the 20th century with treatment being principally supportive. Protection from potential causative agents is an essential part of management and to that end protection against contrast-induced nephropathy has received yet more attention. When optimization of volume status, haemodynamic parameters, electrolyte and acid-base disturbances have failed we turn to renal replacement therapy. The time 'bought' on renal support gives a period for renal recovery but although renal replacement therapy is widely employed, many management issues remain unanswered, including the timing, duration and the dose of treatment. In contrast to respiratory support for acute lung injury, for example, there is a paucity of large randomized studies addressing these fundamental issues. We describe some recent studies focusing on these issues with the hope that they may lead to better treatment for our patients

N-player quantum games in an EPR setting

The $N$-player quantum game is analyzed in the context of an Einstein-Podolsky-Rosen (EPR) experiment. In this setting, a player's strategies are not unitary transformations as in alternate quantum game-theoretic frameworks, but a classical choice between two directions along which spin or polarization measurements are made. The players' strategies thus remain identical to their strategies in the mixed-strategy version of the classical game. In the EPR setting the quantum game reduces itself to the corresponding classical game when the shared quantum state reaches zero entanglement. We find the relations for the probability distribution for $N$-qubit GHZ and W-type states, subject to general measurement directions, from which the expressions for the mixed Nash equilibrium and the payoffs are determined. Players' payoffs are then defined with linear functions so that common two-player games can be easily extended to the $N$-player case and permit analytic expressions for the Nash equilibrium. As a specific example, we solve the Prisoners' Dilemma game for general $N \ge 2$. We find a new property for the game that for an even number of players the payoffs at the Nash equilibrium are equal, whereas for an odd number of players the cooperating players receive higher payoffs.Comment: 26 pages, 2 figure

Resource use data by patient report or hospital records: Do they agree?

Background: Economic evaluations alongside clinical trials are becoming increasingly common. Cost data are often collected through the use of postal questionnaires; however, the accuracy of this method is uncertain. We compared postal questionnaires with hospital records for collecting data on physiotherapy service use. Methods: As part of a randomised trial of orthopaedic medicine compared with orthopaedic surgery we collected physiotherapy use data on a group of patients from retrospective postal questionnaires and from hospital records. Results: 315 patients were referred for physiotherapy. Hospital data on attendances was available for 30% (n = 96), compared with 48% (n = 150) of patients completing questionnaire data (95% Cl for difference = 10% to 24%); 19% (n = 59) had data available from both sources. The two methods produced an intraclass correlation coefficient of 0.54 (95% Cl 0.31 to 0.70). However, the two methods produced significantly different estimates of resource use with patient self report recalling a mean of 1.3 extra visits (95% Cl 0.4 to 2.2) compared with hospital records. Conclusions: Using questionnaires in this study produced data on a greater number of patients compared with examination of hospital records. However, the two data sources did differ in the quantity of physiotherapy used and this should be taken into account in any analysi

The effects of developmental trauma on theory of mind and its relationship to psychotic experiences: A behavioural study

BACKGROUND: Developmental psychological trauma induces vulnerability to psychosis. However, the mechanisms underlying this association are poorly understood. Impairments in Theory of Mind (ToM) have been observed in adult survivors of developmental trauma and individuals with psychosis. ToM is therefore a candidate mechanism underlying the association between developmental trauma and psychosis. METHODS: We used a computerised version of the Director task - where a participant is instructed by a confederate to move an object around a 4 × 4 grid, whilst taking account of whether these objects are visible to a confederate who instructs the participant - to investigate impairments in ToM in 209 participants (age: M = 37.8, SD=13.6; 56% female). Participants were divided into a) developmental trauma-positive (DT+) and control groups (DT-) based on their history of developmental trauma and b) then further into subclinical (S) and healthy groups (H) as based on psychotic experiences indexed by the CAPE-P15. After exclusion, the numbers in each group were: DT+H (47), DT+S (84), DT-H (54), DT-S (12). (Total: 197). RESULTS: Developmental trauma exposure was associated with psychotic experiences (OR: 7.89, p < .001), which remained significant after controlling for demographic and clinical confounds (adjusted R2 = 0.452, R2 change = 0.0184, p = .009). Participants with developmental trauma (F1, 194) = 5.46, p = .020, ηp2 = 0.027) and participants more prone to psychotic experiences (F1, 194) = 4.71, p = .031, ηp2 = 0.024) demonstrated significantly lower accuracy on the Director task relative to their respective control, after controlling for the effects of age. CONCLUSIONS: ToM deficits are associated with self-reported developmental trauma and psychotic experiences. Further work is needed to explore these relationships further and whether they represent generalised or specific effect effects on developmental trauma and psychopathological domains

Rapid Global Expansion of the Fungal Disease Chytridiomycosis into Declining and Healthy Amphibian Populations

Published versio

Internal and external cooling methods and their effect on body temperature, thermal perception and dexterity

© 2018 The Authors. Published by PLOS. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1371/journal.pone.0191416© 2018 Maley et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Objective The present study aimed to compare a range of cooling methods possibly utilised by occupational workers, focusing on their effect on body temperature, perception and manual dexterity. Methods Ten male participants completed eight trials involving 30 min of seated rest followed by 30 min of cooling or control of no cooling (CON) (34C, 58% relative humidity). The cooling methods utilised were: ice cooling vest (CV0), phase change cooling vest melting at 14C (CV14), evaporative cooling vest (CVEV), arm immersion in 10C water (AI), portable water-perfused suit (WPS), heliox inhalation (HE) and ice slushy ingestion (SL). Immediately before and after cooling, participants were assessed for fine (Purdue pegboard task) and gross (grip and pinch strength) manual dexterity. Rectal and skin temperature, as well as thermal sensation and comfort, were monitored throughout. Results Compared with CON, SL was the only method to reduce rectal temperature (P = 0.012). All externally applied cooling methods reduced skin temperature (P0.05). Conclusion The present study observed that ice ingestion or ice applied to the skin produced the greatest effect on rectal and skin temperature, respectively. AI should not be utilised if workers require subsequent fine manual dexterity. These results will help inform future studies investigating appropriate pre-cooling methods for the occupational worker.This project is financially supported by the US Government through the Technical Support Working Group within the Combating Terrorism Technical Support Office.Published versio

Extracting the rho meson wavefunction from HERA data

We extract the light-cone wavefunctions of the rho meson using the HERA data on diffractive rho photoproduction. We find good agreement with predictions for the distribution amplitude based on QCD sum rules and from the lattice. We also find that the data prefer a transverse wavefunction with enhanced end-point contributions.Comment: 13 pages, 7 figures, significant improvements over the original version with a new section on distribution amplitudes adde

Handheld computers for data entry: high tech has its problems too

BACKGROUND: The use of handheld computers in medicine has increased in the last decade, they are now used in a variety of clinical settings. There is an underlying assumption that electronic data capture is more accurate that paper-based data methods have been rarely tested. This report documents a study to compare the accuracy of hand held computer data capture versus more traditional paper-based methods. METHODS: Clinical nurses involved in a randomised controlled trial collected patient information on a hand held computer in parallel with a paper-based data form. Both sets of data were entered into an access database and the hand held computer data compared to the paper-based data for discrepancies. RESULTS: Error rates from the handheld computers were 67.5 error per 1000 fields, compared to the accepted error rate of 10 per 10,000 field for paper-based double data entry. Error rates were highest in field containing a default value. CONCLUSION: While popular with staff, unacceptable high error rates occurred with hand held computers. Training and ongoing monitoring are needed if hand held computers are to be used for clinical data collection