Underwater Explosion Damage of Ship Hull Panels

Underwater explosion is a major threat to ships and submarines in a war environment. The prediction of the mode and the extent of the failure is an essential step in designing for shock loading. The localised failure in a hull panel is severe compared to the global response of the ship. In this study, an attempt has been made to predict the response and failure modes of three types of hull panels (flat, concave, and convex). The shock loading on the hull panel has been estimated based on the Taylor's plate theory. The numerical analysis has been carried out using the CSAIGENSA (DYNA3D) code that employs nonlinear finite element model

Discordant inflammatory changes in the apophyseal and sacroiliac joints: serial observations in enthesitis-related arthritis

OBJECTIVE: To determine the extent to which inflammation of the sacroiliac joints (SIJs) and apophyseal joints (AJs) changes concordantly after treatment in enthesitis-related arthritis (ERA). METHODS: A retrospective study was performed with institutional review board approval. 31 young patients with ERA who had been scanned between March 2009 and November 2014 were included. All patients had post-contrast imaging of the SIJs and lumbar spine and short tau inversion-recovery (STIR) images of the SIJs. The severity of sacroiliitis was scored using a modification of an established technique, and inflammation of the AJs was evaluated using a recently described grading system. The changes in SIJ and AJ scores after treatment were classified as either concordant or discordant, and the proportion of scan pairs in these groups was recorded. In addition, the correlation between change in SIJ STIR score (Δnfla) and change in AJ score (ΔAJ) was assessed using Spearman's correlation coefficient. RESULTS: Of a total of 43 scan pairs, the changes in inflammation were concordant in 16 scan pairs and discordant in 27 scan pairs. There was no significant correlation between Δnfla and ΔAJ (R = 0.14, p = 0.37). CONCLUSION: Inflammatory changes in the SIJs and AJs are often discordant. This may be a reason why patients experience ongoing back pain despite apparent improvement in one or the other site. ADVANCES IN KNOWLEDGE: Inflammation may behave differently at different anatomical sites. The SIJs and AJs should both be imaged in patients with ERA with back pain

A diffusion-based quantification technique for assessment of sacroiliitis in adolescents with enthesitis-related arthritis

OBJECTIVE: To investigate the use of a quantitative diffusion-weighted imaging (DWI) tool for measuring inflammation of the sacroiliac joints (SIJs) in enthesitis-related arthritis (ERA). METHODS: A retrospective study was performed with institutional review board approval. Subjects were adolescents who had undergone MRI of the SIJs since January 2010. 10 patients with a clinical diagnosis of ERA and 10 controls with a clinical diagnosis of mechanical back pain were assessed. Axial T1 weighted, short tau inversion recovery (STIR) and DWI (b-values 0, 50, 100, 300 and 600 mm(2) s(-1)) images were acquired. Apparent diffusion coefficient (ADC) maps were generated using a monoexponential fit. On each of four slices, two to three linear regions-of-interest were placed on each joint. Normalized ADC (nADC) values were defined as joint ADC divided by a reference ADC derived from normal sacral bone. STIR images were scored using a modification of an established technique. The correlation between nADC values and STIR scores was evaluated using Spearman's rank correlation. RESULTS: Mean nADC values were significantly higher in cases than in controls (p = 0.0015). There was a strong correlation between STIR scores and nADC values (R = 0.85). CONCLUSION: ADC values are significantly increased in inflamed SIJs compared with controls. There is a good correlation between this diffusion-based method and STIR scores of inflammation. ADVANCES IN KNOWLEDGE: We have described and provisionally validated a method for quantifying the severity of inflammation in the SIJs in ERA using ADC measurements. This method is quick, is reproducible and could potentially be automated

Smokeless tobacco use: a meta-analysis of risk and attributable mortality estimates for India

Background: Use of smokeless tobacco (SLT) is widely prevalent in India and Indian subcontinent. Cohort and case-control studies in India and elsewhere report excess mortality due to its use. Objective: The aim was to estimate the SLT use-attributable deaths in males and females, aged 35 years and older, in India. Materials And Methods: Prevalence of SLT use in persons aged 35 years and older was obtained from the Global Adult Tobacco Survey in India and population size and deaths in the relevant age-sex groups were obtained from UN estimates (2010 revision) for 2008. A meta-relative risk (RR) based population attributable fraction was used to estimate attributable deaths in persons aged 35 years and older. A random effects model was used in the meta-analysis on all-cause mortality from SLT use in India including four cohort and one case-control study. The studies included in the meta-analysis were adjusted for smoking, age and education. Results: The prevalence of SLT use in India was 25.2% for men and 24.5% for women aged 35 years and older. RRs for females and males were 1.34 (1.27-1.42) and 1.17 (1.05-1.42), respectively. The number of deaths attributable to SLT use in India is estimated to be 368127 (217,076 women and 151,051 men), with nearly three-fifth (60%) of these deaths occurring among women. Conclusion: SLT use caused over 350,000 deaths in India in 2010, and nearly three-fifth of SLT use-attributable deaths were among women in India. This calls for targeted public health intervention focusing on SLT products especially among women

Diffusion-weighted imaging is a sensitive biomarker of response to biologic therapy in enthesitis-related arthritis

OBJECTIVE: The aim was to evaluate diffusion-weighted imaging (DWI) as a tool for measuring treatment response in adolescents with enthesitis-related arthropathy (ERA). METHODS: Twenty-two adolescents with ERA underwent routine MRI and DWI before and after TNF inhibitor therapy. Each patient’s images were visually scored by two radiologists using the Spondyloarthritis Research Consortium of Canada system, and sacroiliac joint apparent diffusion coefficient (ADC) and normalized ADC (nADC) were measured for each patient. Therapeutic clinical response was defined as an improvement of 5 30% physician global assessment and radiological response defined as 52.5-point reduction in Spondyloarthritis Research Consortium of Canada score. We compared ADC and nADC changes in responders and non-responders using the MannWhitneyWilcoxon test. RESULTS: For both radiological and clinical definitions of response, reductions in ADC and nADC after treatment were greater in responders than in non-responders (for radiological response: ADC: P < 0.01; nADC: P = 0.055; for clinical response: ADC: P = 0.33; nADC: P = 0.089). ADC and nADC could predict radiological response with a high level of sensitivity and specificity and were moderately sensitive and specific predictors of clinical response (the area under the receiver operating characteristic curves were as follows: ADC: 0.97, nADC: 0.82 for radiological response; and ADC: 0.67, nADC: 0.78 for clinical response). CONCLUSION: DWI measurements reflect the response to TNF inhibitor treatment in ERA patients with sacroiliitis as defined using radiological criteria and may also reflect clinical response. DWI is more objective than visual scoring and has the potential to be automated. ADC/nADC could be used as biomarkers of sacroiliitis in the clinic and in clinical trials

Inflammatory changes of the lumbar spine and sacroiliac joints in patients with enthesitis-related arthritis; MRI findings and quantification of inflammation using DWI

Enthesitis-related arthritis (ERA) is a paediatric/adolescent inflammatory arthritis characterised by peripheral arthritis, spinal involvement, sacroiliitis and enthesitis. The natural history and aetiology of the disease are poorly understood. A quantitative method of measuring disease activity would be helpful for the detection of early disease, disease monitoring and assessment of treatment. Currently there is no available gold standard for quantifying disease activity nor is there a validated radiological method for quantifying inflammation in children. Three areas are addressed in this thesis: 1. The first part of this thesis focuses on the development and validation of a methodology to quantify inflammation of the sacroiliac joints (SIJs) in ERA patients, using diffusion weighted MRI. Diffusion in inflamed bone is less restricted than in normal bone, increasing numerical values of diffusion. A custom written Matlab program was used to obtain profiles of apparent diffusion coefficient (ADC) values in regions of inflammation in the SIJs in ERA patients and these were compared with normal SIJs in controls. A highly significant difference was seen in ADC values between ERA cases and controls. This novel technique shows promise as a method of simply and quickly assessing SIJ inflammation. 2. A further study was performed to investigate the effects of skeletal maturity on ADC values in subchondral bone of sacroiliac joints. The results showed that normalised ADC values of immature SIJs were significantly higher than that of mature SIJs. This has implications when assessing young adolescents for axial inflammation. 3. The spinal features of inflammation in ERA have been studied and described in this thesis. Statistically significant inflammation of the facet joints and the interspinous ligaments were seen in a cohort of ERA patients. This is a previously undescribed finding and it is possible that spinal inflammatory changes could be contributing to back pain in these patients

Robust Estimators of Scale and Location Parameter Using Matlab

Abstract. In this paper an attempt has been made to analyze the data for the specific distributions and estimated the values of robust estimators under scale, shape and location parameter using MATLAB software. The concept of outliers and their effect on these estimators have also discussed in the scale and location parameter which are used in the Normal, Exponential and Poisson distribution