Recent trends towards simulation of the cyclic slip behavior of polycrystalline and polyphase microstructures of advanced engineering alloys subjected to cyclic loading are facilitating understanding ...of the relative roles of intrinsic and extrinsic attributes of microstructure in fatigue crack formation, comprised of nucleation and growth of cracks at the scale of individual grains or phases. Modeling of processes of early stages of fatigue crack nucleation and growth at these microstructure scales is an important emerging frontier in several respects. First, it facilitates analysis of the influence of local microstructure attributes on the distribution of driving forces for fatigue crack formation as a function of the applied stress state. This can support microstructure-sensitive estimates of minimum life, as well as characterization of competing failure modes. Second, it can inform modification of process route and its manifestations (e.g., residual stress, texture) to alter microstructure in ways that promote enhanced resistance to formation of fatigue cracks. Third, microstructure-sensitive modeling, even conducted at the mesocopic scale of individual grains/phases, can facilitate parametric design exploration in searching for microstructure morphologies and/or compositions that modify fatigue resistance. Fourth, such technologies offer promise for integration with advanced nondestructive evaluation methods for prognosis and structural health monitoring. Finally, as a longer term prospect in view of uncertainties in modeling mechanisms of cyclic slip, crack nucleation and growth, such modeling can serve to support more quantitative predictions of fatigue lifetime as a function of microstructure. We first discuss computationally based microstructure-sensitive fatigue modeling in the context of recent initiatives in accelerated insertion of materials and integration of computational mechanics, materials science, and systems engineering in design of materials and structures. We then highlight recent application of such strategies to Ni-base superalloys, gear steels, and α–β Ti alloys, with focus on the individual grain scale as the minimum length scale of heterogeneity. Finally, we close by outlining opportunities to advance microstructure-sensitive fatigue modeling in the next decade.
The goal of this review is to identify studies of self-regulated learning of students taking introductory physical science (chemistry, physics, and engineering) courses in college. This study ...analysed research in self-regulated learning published between the years of 2008-2018 with a focus on undergraduate learners in chemistry, physics, and engineering classrooms. It was found that there is a high degree of agreement in defining self-regulated learning, yet differences are present in the proposed factors that are most influential in creating a self-regulated learner. A majority of the studies report correlations between variables of motivation and metacognition. Additionally, less than half of the research studies included a measure of achievement and even less had an experimental design. This review proposes a need for more studies which include teaching of self-regulated skills for undergraduates in the physical sciences and investigating the relationship of the development of self-regulated learners as an integral facet of education in physical science classrooms.
The distributions of the extreme-value driving force(s) for surface vs. subsurface fatigue crack formation (nucleation and early growth) in high-cycle fatigue are evaluated for a microstructure ...variant of duplex Ti–6Al–4V. In polycrystalline metals, previous work has explored estimation of the driving force(s) for fatigue crack formation at the scale of the grains by computing non-local fatigue indicator parameters (FIPs) based on the cyclic plastic strain averaged over domains on the length scale of the grains. Instantiated statistical volume elements (SVEs), which sample the distributed microstructure attributes of interest for a given material system, can be simulated via the finite element method with embedded polycrystalline plasticity models to estimate the distributed plasticity and resulting FIPs. This strategy of simulating multiple SVEs is in contrast to the simulation of a single representative volume element which is typically untenably large for extreme-value distributions of microstructure attributes or response variables. In this work, multiple SVEs are instantiated with both traction-free (i.e. surface) boundary conditions and fully periodic (i.e. subsurface) boundary conditions. In addition to estimating the extreme-value distributions of the FIPs, newly introduced extreme-value marked correlation functions are applied to characterize the coupled crystallographic microstructure attributes (e.g. grain size, grain orientation, grain misorientation) that most influence the extreme-value distributions of the FIPs. It is shown that there is overlap in the distributions of the driving forces for surface vs. subsurface crack formation in the low to moderate range of failure probability based on FIPs; however, at higher failure probability levels, the driving forces are highest for surface crack formation. The overlap in the distributions of the driving forces for fatigue crack formation in the low to moderate probability range may assist in describing the competing surface vs. subsurface failure modes that are observed experimentally.
Atomistic simulations were employed to investigate the structure and energy of asymmetric tilt grain boundaries in Cu and Al. In this work, we examine the Σ5 and Σ13 systems with a boundary plane ...rotated about the ⟨ 100 ⟩ misorientation axis, and the Σ9 and Σ11 systems rotated about the ⟨ 110 ⟩ misorientation axis. Asymmetric tilt grain boundary energies are calculated as a function of inclination angle and compared with an energy relationship based on faceting into the two symmetric tilt grain boundaries in each system. We find that asymmetric tilt boundaries with low index normals do not necessarily have lower energies than boundaries with similar inclination angles, contrary to previous studies. Further analysis of grain boundary structures provides insight into the asymmetric tilt grain boundary energy. The Σ5 and Σ13 systems in the ⟨ 100 ⟩ system agree with the aforementioned energy relationship; structures confirm that these asymmetric boundaries facet into the symmetric tilt boundaries. The Σ9 and Σ11 systems in the ⟨ 110 ⟩ system deviate from the idealized energy relationship. As the boundary inclination angle increases towards the Σ9 (221) and Σ11 (332) symmetric tilt boundaries, the minimum energy asymmetric boundary structures contain low index {111} and {110} planes bounding the interface region.
Studies systematically screening medications have successfully identified prescription medicines associated with cancer risk. However, adjustment for confounding factors in these studies has been ...limited. We therefore investigated the association between frequently prescribed medicines and the risk of common cancers adjusting for a range of confounders.
A series of nested case-control studies were undertaken using the Primary Care Clinical Informatics Unit Research (PCCIUR) database containing general practice (GP) records from Scotland. Cancer cases at 22 cancer sites, diagnosed between 1999 and 2011, were identified from GP records and matched with up to five controls (based on age, gender, GP practice and date of registration). Odds ratios (OR) and 95% confidence intervals (CI) comparing any versus no prescriptions for each of the most commonly prescribed medicines, identified from prescription records, were calculated using conditional logistic regression, adjusting for comorbidities. Additional analyses adjusted for smoking use. An association was considered a signal based upon the magnitude of its adjusted OR, p-value and evidence of an exposure-response relationship. Supplementary analyses were undertaken comparing 6 or more prescriptions versus less than 6 for each medicine.
Overall, 62,109 cases and 276,580 controls were included in the analyses and a total of 5622 medication-cancer associations were studied across the 22 cancer sites. After adjusting for comorbidities 2060 medicine-cancer associations for any prescription had adjusted ORs greater than 1.25 (or less than 0.8), 214 had a corresponding p-value less than or equal to 0.01 and 118 had evidence of an exposure-dose relationship hence meeting the criteria for a signal. Seventy-seven signals were identified after additionally adjusting for smoking. Based upon an exposure of 6 or more prescriptions, there were 118 signals after adjusting for comorbidities and 82 after additionally adjusting for smoking.
In this study a number of novel associations between medicine and cancer were identified which require further clinical and epidemiological investigation. The majority of medicines were not associated with an altered cancer risk and many identified signals reflected known associations between medicine and cancer.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
How do newspapers frame female politicians, and does this framing change after a female politician's death during an election campaign? Benazir Bhutto, who served two terms as prime minister of ...Pakistan, was assassinated in 2007 by a terrorist group. South Asian newspapers framed her as corrupt, inefficient, and a threat to national security before her death; however, the elite press characterized her as a martyr and sage posthumously. Using qualitative content analysis, this study examines the editorial coverage of two newspapers (The Hindu and The Times of India) in India and two newspapers (The News and The Dawn) in Pakistan to examine how these elite newspapers framed Benazir Bhutto before and after her tragic death. We found that the framing of the slain leader changed from negative to positive after her assassination. The study concludes that her assassination influenced the media coverage and produced a eulogy effect that helped her party stay in power after her assassination.
ABSTRACT
A computational study is conducted to determine the influence of microstructure attributes and properties on driving forces for fatigue crack formation and microstructurally small crack ...growth in a polycrystalline Ni‐base superalloy, IN100, a turbine disk alloy. A principal objective is to obtain quantitative estimates of the effect of variability of microstructure features on scatter in fatigue life or fatigue strength for a given life. Understanding is sought regarding sensitivity of driving forces to various microstructure attributes that may guide selection of the process route to tailor microstructure to achieve fatigue resistance. A microstructure‐sensitive crystal plasticity model is used to explicitly model individual grains and polycrystals, which is then used to explore effects of: (a) grain size distribution and (b) secondary and tertiary coherent γ′ precipitate size distributions and volume fractions on the cyclic inelastic strain distribution. Multiple statistical volume elements (SVEs) are subjected to random periodic boundary conditions to build up statistically significant measures of distributions of cyclic microplasticity. Multiaxial fatigue criteria with critical plane approaches are used to estimate the crack initiation life. Methods are developed for assessing crack formation and microstructurally small crack growth as a function of microstructure attributes.
The objectives of this study were to examine domestic food safety knowledge levels of consumers, establish the levels and incidence of bacterial contamination and operational temperatures in domestic ...refrigerators, and identify areas in which consumer food safety education is necessary in Ireland. A food safety knowledge questionnaire applied to a representative sample of households (n = 1,020) throughout the island of Ireland found the gaps in consumer food safety knowledge. Analysis of swab samples (n = 900) recovered from the domestic refrigerators in these households showed average total viable counts of 7.1 log CFU/cm2 and average total coliform counts of 4.0 log CFU/cm2. Analysis of swab samples also detected the incidence of Staphylococcus aureus (41%), Escherichia coli (6%), Salmonella enterica (7%), Listeria monocytogenes (6%), and Yersinia enterocolitica (2%). Campylobacter jejuni and E. coli O157:H7 were not detected in domestic refrigerators. The temperature profiles of a subset of the sampled refrigerators (100) were monitored for 72 h, and 59% were found to operate, on average, at temperatures above the recommended 5 degrees C. Knowledge and temperature survey results varied considerably, but consumers who scored better in terms of basic food safety knowledge had reduced levels of bacterial contamination in their refrigerators and reported a reduced incidence of food-associated illnesses. This study confirms the effect of basic food hygiene knowledge on hygienic practice and identifies specific areas for emphasis in the development and delivery of effective food safety risk communication messages to consumers.
Atomistic simulations are used to investigate how the stress required for homogeneous nucleation of partial dislocations in single crystal copper under uniaxial loading changes as a function of ...crystallographic orientation. Molecular dynamics is employed based on an embedded-atom method potential for Cu at 10 and 300
K. Results indicate that non-Schmid parameters are important for describing the calculated dislocation nucleation behavior for single crystal orientations under tension and compression. A continuum relationship is presented that incorporates Schmid and non-Schmid terms to correlate the nucleation stress over all tensile axis orientations within the stereographic triangle. Simulations investigating the temperature dependence of homogeneous dislocation nucleation yield activation volumes of
≈
0.5
–
2
b
3
and activation energies of
≈
0.30
eV
. For uniaxial compression, full dislocation loop nucleation is observed, in contrast to uniaxial tension. One of the main differences between uniaxial tension and compression is how the applied stress is resolved normal to the slip plane on which dislocations nucleate—in tension, this normal stress is tensile, and in compression, it is compressive. Last, the tension–compression asymmetry is examined as a function of loading axis orientation. Orientations with a high resolved stress normal to the slip plane on which dislocations nucleate have a larger tension–compression asymmetry with respect to dislocation nucleation than those orientations with a low resolved normal stress. The significance of this research is that the resolved stress normal to the slip plane on which dislocations nucleate plays an important role in partial (and full) dislocation loop nucleation in FCC Cu single crystals.
Campylobacteriosis is the most common foodborne bacterial infection in developed countries and many cases are associated with poultry. This study investigated the immediate and storage effect of ...dipping inoculated poultry skin samples in trisodium phosphate (TSP, 10 & 14%, w/v), lactic acid (LA, 1 & 5%, v/v), citric acid (CA, 1 & 5%, w/v), peroxyacids (POA, 100 & 200ppm) and acidified sodium chlorite (ASC, 500 & 1200ppm). Spray application was also tested using the higher concentrations in the laboratory. In a broiler processing plant the efficacy of using TSP (14%) and CA (5%) applied by immersion and spray was investigated using naturally contaminated carcasses and the effect of these treatments on the sensory attributes of a skin-on (drumstick) and skin-off (fillet) raw and cooked product was assessed using descriptive sensory analysis. In the laboratory, immersion in TSP (14%), LA (5%), CA (5%) and ASC (1200ppm) significantly (P<0.05) reduced the Campylobacter counts and a 2.5 to 3log10 cfu/cm2 reduction was observed within the shelf-life (3–5days) of poultry meat. Spraying was ineffective even after storage. In the broiler processing plant, immersion in TSP (14%) or CA (5%) achieved Campylobacter reductions of 2.49 and 1.44log10 cfu/cm2, respectively. There were no significant differences between the treatments for any of the attributes measured in either raw or cooked drumsticks. The ‘colour’ of raw chicken fillets treated with both TSP (14%, w/v) and CA (5%, w/v) was significantly (P≤0.05) lighter than that of control samples. The ‘intensity of chicken odour’ and the perception of ‘salt’ in cooked chicken fillets treated with CA (5%, w/v) were also significantly (P≤0.05) higher than that of either control or TSP (14%, w/v) treated samples. It was concluded that TSP (14%) or CA (5%) could be applied to significantly reduce Campylobacter contamination of broilers without adversely affecting the sensory quality of the product.
•Immersion in 14% TSP or 5% CA significantly (P<0.05) reduced broiler Campylobacter.•Spraying was not an effective chemical application method.•TSP and CA treatments did not adversely affect poultry skin-on sensory attributes.
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