An existing process model for hardness prediction in age hardenable aluminium alloy welds is presented and analysed. One of the key criticisms of this model is that its derivation assumes softening ...is due to precipitate dissolution alone. The influence of precipitate coarsening has been determined by developing an equivalent model for softening owing to coarsening. It is shown that the experimentally derived master curves that form the basis of the model are capable of representing softening by a mixture of precipitate coarsening and dissolution. Methods to predict post-weld natural aging are discussed, and a new method is presented based on direct prediction of the Guinier-Preston zone fraction. The model has been applied to friction stir welding. Model predictions agree well with measured hardness profiles, and the sensitivity of the predictions to temperature is discussed.
High spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge Er. We observe fine-scale spatial structures in the edge Er well with a ...wave number krρi≈0.4-0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelength both decrease with local collisionality, such that the zonal flow E×B shear increases. Above the minimum of the L-H transition power threshold dependence on density, the zonal flows are present during L mode and disappear following the H-mode transition, while below the minimum they are reduced below measurable amplitude during L mode, before the L-H transition.
The microstructure, hardness, lap shear strength and fracture energy of AA2139–TiAl6V4 spot joints produced by ultrasonic welding were investigated and related to the weld thermal cycle. No obvious ...intermetallic reaction layer was observed in the AA2139–TiAl6V4 welds, even using transmission electron microscopy. The hardness profile of AA2139 side after welding was studied, demonstrating that the heat introduced by the welding process leads to some softening with partial hardness recovery after natural aging. The effects of welding time on peak load and fracture energy were investigated. The peak load and fracture energy of welds increased with an increase in welding time and then reached a plateau, i.e., maximum peak load 5.3kN and maximum fracture energy 3.7kNmm. In all cases, failure occurred by fracture at the weld interface.
The regulated splicing of fibroblast growth factor receptor-2 (FGFR2) transcripts leads to tissue-specific expression of distinct receptor isoforms. These isoforms contain two different versions of ...the ligand binding Ig-like domain III, which are encoded by exon IIIb or exon IIIc. The mutually exclusive use of exon IIIb and exon IIIc can be recapitulated in tissue culture using DT3 and AT3 rat prostate carcinoma cells. We used this well-characterized system to evaluate the precision and accuracy of the RNA invasive cleavage assay to specifically measure FGFR2 alternative splicing outcomes. Experiments presented here demonstrated that the RNA invasive cleavage assay could specifically detect isoforms with discrimination levels that ranged from 1 in 5 x 10(3) to 1 in 10(5). Moreover the assay could detect close to 0.01 amole of FGFR2 RNAs. The assay detected the expected levels of transcripts containing either exon IIIb or IIIc, but, surprisingly, it detected high levels of IIIb-IIIc double inclusion transcripts. This finding, which has important implications for the role of exon silencing and of mRNA surveillance mechanisms, had been missed by RT-PCR. Additionally, we used the RNA invasive cleavage assay to demonstrate a novel function for the regulatory element IAS2 in repressing exon IIIc inclusion. We also show here that purification of RNA is not necessary for the invasive cleavage assay, because crude cell lysates could be used to accurately measure alternative transcripts. The data presented here indicate that the RNA invasive cleavage assay is an important addition to the repertoire of techniques available for the study of alternative splicing.
This article describes an approach to imaging of fetal head and neck anomalies. Topics include cleft lip and palate, facial clefts, amniotic band sequence, micrognathia and retrognathia, ocular and ...orbital abnormalities, craniosynostosis, posterior nuchal translucency, cephaloceles, vascular anomalies, and tumors. Some of the more common syndromes are also described.
Summary Background Skin infections with ulceration are a major health problem in countries of the south Pacific region. Yaws, caused by Treponema pallidum subspecies pertenue and diagnosed by the ...presence of skin ulcers and a reactive syphilis serology, is one major cause, but this infection can be confused clinically with ulcers due to other causative agents. We investigated T pallidum pertenue and another bacterium known to cause skin infections in the Pacific islands— Haemophilus ducreyi —as causes of skin ulceration in a yaws-endemic region. Additionally, we identified specific signs and symptoms associated with these causative agents of cutaneous ulcers and compared these findings with laboratory-based diagnoses. Methods We did a prospective cohort study of five yaws-endemic villages (total population 3117 people) during a yaws elimination campaign in Papua New Guinea in April, 2013. We enrolled all consenting patients with chronic moist or exudative skin ulcers. We undertook a detailed dermatological assessment, syphilis serology, and PCR on lesional swabs to detect the presence of T pallidum pertenue and H ducreyi . Patients with PCR-confirmed bacterial infections were included in a comparative analysis of demographics and clinical features. Findings Full outcome data were available for 90 people with skin ulcers. Of these patients, 17 (19%) had negative results in all molecular tests and were therefore excluded from the comparative analyses. A bacterial cause was identified in 73 (81%) participants—either H ducreyi (n=42), T pallidum pertenue (yaws; n=19), or coinfection with both organisms (dual infection; n=12). The demographic characteristics of the patients infected with yaws and with H ducreyi were similar. Skin lesions in patients with yaws and in those with dual infection were larger than those in patients infected with H ducreyi (p=0·071). The lesions in patients with yaws and dual infection were more circular in shape (79% and 67%) than in those infected with H ducreyi (21%; p<0·0001); more likely to have central granulating tissue (90% and 67% vs 14%; p<0·0001); and more likely to have indurated edges (74% and 83% vs 31%; p=0·0003). The prevalence of reactive combined serology (positive T pallidum haemagglutination test and rapid plasmin reagin titre of ≥1:8) was higher in cases of yaws (63%) and dual infections (92%) than in H ducreyi infections (29%; p<0·0001). Interpretation In this yaws-endemic community, H ducreyi is an important and previously unrecognised cause of chronic skin ulceration. Reactive syphilis serology caused by latent yaws can occur in ulcers with the presence of H ducreyi alone. The introduction of PCR for ulcer surveillance could improve the accuracy of diagnosis in countries with yaws eradication campaigns. Funding Newcrest Mining Company.
High strength Al-Zn-Mg-Cu alloys rely for their properties on nano-scaled precipitates formed during artificial ageing. Deformation profoundly affects the evolution of these precipitates. This study ...investigates the effect of warm deformation on precipitation in a pre-aged AA7075 aluminium alloy. Warm deformation was performed using an electro-thermomechanical testing machine for rapid resistance heating. Transmission electron microscopy showed slightly larger, yet evenly distributed, precipitates in the warm deformed sample compared to the thermally treated condition without deformation. Synchrotron small angle X-ray scattering revealed accelerated growth rates of precipitates due to deformation. At low plastic strains, the growth rate increased linearly with applied strain, while at high plastic strains, a slight deviation from linear behaviour was observed. Temperature and strain rate effects were also examined, with a stronger enhancement effect at low temperature and fast strain rate for a given strain. The deformation enhancement effect disappeared rapidly upon finishing plastic deformation (within 400 s for the studied condition). The enhanced growth rate during and after deformation can be reasonably explained by the excess vacancy concentration, indicating the influence of strain-induced excess vacancies. However, the simple excess vacancy model used fails to explain the observed strain rate effect, and possible explanations for this discrepancy are discussed.
•Deformation accelerates precipitation, influenced by strain, strain rate, and temperature.•Warm deformation yields larger, evenly distributed precipitates.•The enhancement effect of deformation diminishes quickly upon stress removal.
PDF
