Experimental and numerical study on the effect of strain rate to ductile damage

Includes bibliographical references (p. 202-208).Ductile fracture modelling is extensively used in the automotive, aerospace, aluminium and steel industries. However, these models are often only validated in a limited region of stress states, for example tensile failure by void growth but not shear. In addition, the predictions generally do not include strain rate or temperature effects. Quasistatic tests are often used in calibration, even though many applications such as automotive accidents and ballistic impact operate in the dynamic range. Thus the aims of this thesis were to develop a system to test the damage properties of materials at both quasistatic (≈ 1 s-¹) and dynamic (> 1 x 10³s-¹) strain rates, and then to determine the innfuence of strain rate to ductile fracture

Experimental and numerical study on the effect of strain rate to ductile damage

Ductile fracture modelling is extensively used in the automotive, aerospace, aluminium and steel industries. However, these models are often only validated in a limited region of stress states, for example tensile failure by void growth but not shear. In addition, the predictions generally do not include strain rate or temperature effects. Quasistatic tests are often used in calibration, even though many applications such as automotive accidents and ballistic impact operate in the dynamic range. Thus the aims of this thesis were to develop a system to test the damage properties of materials at both quasistatic (≈ 1 s−1 ) and dynamic (> 1×103 s −1 ) strain rates, and then to determine the influence of strain rate to ductile fracture. From the literature the Bai-Wierzbicki damage model was identified as being applicable to the widest range of loading conditions. Thus tests to calibrate this failure locus were conducted on sheet specimens with notches cut into each to introduce non-axial stresses, resulting in a range of loading conditions. This testing procedure involved experimental testing combined with finite element analysis (FEA) to determine the stress and strain state at the position of fracture initiation. All specimens used material from the same sheet of mild steel. To break the dynamic specimens a tensile split Hopkinson pressure bar, or TSHB, was optimized and built. Hopkinson bars are the standard method of conducting high strain rate characterisation tests, however, there is no universal design to examine tensile deformation. The apparatus built used a tubular striker and produced a square input pulse with low noise as desired. Sheet specimens were glued into slotted sections of threaded bar, which in turn screwed into the split Hopkinson bars. This method was successful as in every case the specimens broke before the epoxy. FEA modelling techniques were optimized to minimize computation time. The most important was the use of infinite elements to simulate the bars which, when calibrated, were found to be the ideal method of modelling split Hopkinson bars. Ultimately it was found that strain rate does influence ductile damage. The dynamic specimens failed at a lower strain than the quasistatic equivalents. This indicates that, at high strain rates, fracture strain decreases with strain rate. In contrast, in the quasistatic range strain rate tends to decrease displacement to fracture and thus it is proposed that at quasistatic strain rates, fracture strain increases with strain rate. It is speculated that the degree that strain rate influences ductile fracture is related to the Lode angle, which is a measure of the third deviatoric stress invariant

Gene Expression Profiling in Familial Adenomatous Polyposis Adenomas and Desmoid Disease

Gene expression profiling is a powerful method by which alterations in gene expression can be interrogated in a single experiment. The disease familial adenomatous polyposis (FAP) is associated with germline mutations in the APC gene, which result in aberrant β-catenin control. The molecular mechanisms underlying colorectal cancer development in FAP are being characterised but limited information is available about other symptoms that occur in this disorder. Although extremely rare in the general population, desmoid tumours in approximately 10% of FAP patients. The aim of this study was to determine the similarities and differences in gene expression profiles in adenomas and compare them to those observed in desmoid tumours. Illumina whole genome gene expression BeadChips were used to measure gene expression in FAP adenomas and desmoid tumours. Similarities between gene expression profiles and mechanisms important in regulating formation of FAP adenomas and desmoid tumours were identified. This study furthers our understanding of the mechanisms underlying FAP and desmoid tumour formation

Altered gene expression in the superior temporal gyrus in schizophrenia

Background: The superior temporal gyrus (STG), which encompasses the primary auditory cortex, is believed to be a major anatomical substrate for speech, language and communication. The STG connects to the limbic system (hippocampus and amygdala), the thalamus and neocortical association areas in the prefrontal cortex, all of which have been implicated in schizophrenia. Results: To identify altered mRNA expression in the superior temporal gyrus (STG) in schizophrenia, oligonucleotide microarrays were used with RNA from postmortem STG tissue from 7 individuals with schizophrenia and 7 matched non-psychiatric controls. Overall, there was a trend towards down-regulation in gene expression, and altered expression of genes involved in neurotransmission, neurodevelopment, and presynaptic function was identified. To confirm altered expression identified by microarray analysis, the mRNA expression levels of four genes, IPLA2γ, PIK31R1, Lin-7b and ATBF1, were semi-quantitatively measured using relative real-time PCR. A number of genes with altered expression in the STG were also shown to have similar changes in expression as shown in our previous study of peripheral blood lymphocytes in schizophrenia. Conclusion: This study has identified altered expression of genes in the STG involved in neurotransmission and neurodevelopment, and to a lesser extent presynaptic function, which further support the notion of these functions playing an integral role in the development of schizophrenia

Nutritional, inflammatory and functional biomarkers in lung cancer : identifying patients at risk of adverse outcomes through two retrospective cohort studies

Background Lung cancer is the commonest cause of cancer death worldwide. A range of biomarkers are associated with adverse outcomes in lung cancer, but these have not been assimilated into routine clinical practice. The aim of the two studies was to identify predictive variables within existing healthcare data for adverse outcomes following lung cancer treatment, with a view to informing optimal treatment selection for future patients. Methods Two retrospective cohort studies of lung cancer patients in South East Scotland were undertaken using demographic and clinical data from healthcare records. A range of explanatory variables were explored using descriptive statistics, logistic regression and survival analysis for treatment-related outcomes. These included overall survival (OS), early mortality and treatment completion. Results 194 patients were included the chemoradiotherapy study, median OS 19 months. Low skeletal muscle attenuation (MA), (odds ratio [OR] 1.61 [95% CI 1.16, 2.23, p=0.004) independently predicted reduced OS. Independent predictors of death within 90 days of treatment completion were Eastern Cooperative Oncology Group Performance Status ≥2 (OR 3.97 [1.20, 13.08], p=0.024) and body mass index (BMI) ≤20 (OR 3.91 [1.24, 12.38], p=0.020). 397 patients were included in the palliative chemotherapy study, median OS 6.9 months. Independent predictors of reduced OS were: neutrophil-to-lymphocyte ratio ≥4, albumin <35, MA and low skeletal muscle mass. Patients who did not receive guideline-recommended treatment (GRT) had a median OS of 3.3 months. Independent predictors of non-GRT receipt were: non-small cell lung cancer, BMI ≤20, neutrophil count ≥7, lymphocyte count <1 and MA <31.55. Discussion A range of routinely available biomarkers can identify patients with lung cancer at increased risk of adverse outcomes. Optimal treatment selection for each patient could be improved by routine utilising these biomarkers. Biomarkers may also be useful to identify patients for integrated supportive care during their cancer treatment. Further research is needed

A case control study reveals that polyomaviruria is significantly associated with interstitial cystitis and vesical ulceration

Objectives: To investigate whether polyomaviruses contribute to interstitial cystitis pathogenesis. Subjects and Methods: A prospective study was performed with 50 interstitial cystitis cases compared with 50 age-matched, disease-free controls for the frequency of polyomaviruria. Associations between polyomaviruria and disease characteristics were analysed in cases. Polyomavirus in urine and bladder tissue was detected with species (JC virus vs. BK virus) specific, real-time PCR. Results: Case patients were reflective of interstitial cystitis epidemiology with age range from 26–88 years (median 58) and female predominance (41/50 F). There was a significant increase in the frequency of polyomavirus shedding between cases and controls (p<0.02). Polyomavirus shedding, in particular BK viruria, was associated with vesical ulceration, a marker of disease severity, among interstitial cystitis cases after adjustment for age and sex (OR 6.8, 95% CI 1.89–24.4). There was a significant association among cases between the presence of BK viruria and response to intravesical Clorpactin therapy (OR 4.50, 95% CI 1.17–17.4). Conclusion: The presence of polyomaviruria was found to be associated with the ulcerative form of interstitial cystitis. Clorpactin, which has anti-DNA virus activity, was more likely to improve symptoms in the presence of BK viruria. These data from this pilot study suggest associations between polyomaviruria and interstitial cystitis warranting further investigation

The inaugural australian centre for hepatitis virology public panel discussion on viral hepatitis research—lessons in scientific community outreach

Viral hepatitis remains one of the most significant health issues globally, directly responsible for over 1 million deaths each year and affecting almost 300 million people around the world. Scientific research in recent decades has brought about improvements in the lives of people living with chronic viral hepatitis. On the 29 July 2021, the Australian Centre for Hepatitis Virology (ACHV) for the first time held a public educational forum for the general public. The main aim of this event was to inform the affected community about the importance of scientific research and give an overview of upcoming developments in the field. Here, we provide a detailed report of the panel discussion (including its organisation, execution, and lessons learned to incorporate into future events) and provide strategies that can be used by other scientific societies to hold similar events in their own communities

Whole genome amplification and its impact on CGH array profiles

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