15 research outputs found
The failure of a tungsten carbide-cobalt cored projectile penetrating a hard target
No full textExperimental results are presented from an investigation of the parameters of a ceramic-faced armour system that are required to induce damage in a tungsten carbide - cobalt (WC-Co) penetrator. A WC-Co material model has been successfully developed and implemented within the numerical hydrocode AUTODYN 2D. The understanding of penetration mechanisms was used to guide a parametric investigation, validating the WC-Co material failure model with experimental results.
A series of experiments has been conducted firing the Russian 14.5 mm BS41 WC-Co cored projectile into various thicknesses and types of alumina (Al2O3) and silicon carbide (SiC), backed by aluminium alloy or mild steel semi-infinite witness blocks. Results demonstrated that SiC B out-performed standard monolithic armours and a selection of other armour ceramics including PS 5000 SiC and Sintox-CL. After comminution, the SiC B consisted of particles of closely interlocked grains. These appeared to provide considerable resistance to deviatoric stresses. Results suggest that it is not only increased hardness but also the nature of the fracture of the ceramic ahead of the penetrator that improves the armour’s ballistic performance at defeating WC-Co penetrators. If such superior ballistic response can be controlled and incorporated into practical armour systems, it will provide the basis for an advance in armour protective capability against WC-Co penetrators.
In addition, a numerical material model derived from experimental data was developed to provide a preliminary tool to study the WC-Co failure. It was demonstrated that the numerical estimation of WC-Co behaviour using a shock Equation Of State (EOS), a piecewise linear strength model and a principle stress failure model provides a good method to estimate spall behaviour under dynamic loading in AUTODYN 2D. Successful numerical simulation of the material model used demonstrated the future potential of the technique
Genetic studies, neuropsychological outcome and environmental influences in multiple sclerosis
No full textA study was performed to examine association between polymorphisms of the apolipoprotein E gene, and of the cannabinoid receptor 1 gene and neuropsychological impairment in multiple sclerosis. A relationship was seen between an exonic polymorphism of the cannabinoid receptor and neuropsychological impairment which withstood correction for multiple ssting. The strongest factor determining neuropsychological impairment was assessment of premorbid intellectual function.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Wigram, Sir John (Woolmore), (born 25 May 1957), Director, JW Consultancy Ltd, since 2013
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Disability, Depression and Suicide Ideation in People with Multiple Sclerosis
No full textIntroductionDepressive symptoms occur frequently in people with Multiple Sclerosis (MS) and rates of suicide ideation are higher than the general population. There is evidence for a direct association between disability and depression, disability and suicide ideation, and depression and suicide ideation in MS. However, the relationship between all three, i.e. the mediating role of depression between disability and suicidal ideation, has not been investigated. Exploring this relationship could highlight risk factors, alerting clinicians to the need for timely intervention.MethodSeventy five people with progressive MS attending two out-patient clinics took part in this cross-sectional study. Participants completed the Beck Suicide Scale, Beck Depression Inventory, Multiple Sclerosis Impact Scale and Guy's Neurological Disability Scale.ResultsDepressive symptoms mediated the relationship between perceived and actual disability and suicide ideation. Different types of disability were associated with suicidality, including: ‘tremors’ and ‘taking longer to do things’. A small sub-group were identified who reported suicide ideation in the presence of only mild levels of depression, supporting a concept termed ‘rational’ suicide.LimitationsThere may be a sample bias in this study as all participants were attending out-patient clinics and receiving support which may not be available to everyone with MS.ConclusionIt is important for clinicians to screen regularly for both depression and suicide ideation, to be alert to specific types of disability for which a higher level of suicide ideation might be present and to consider the possibility of suicidal thoughts being present in people who show minimal or no depressive symptoms
The four self-efficacy trajectories among people with multiple sclerosis:Clinical associations and implications
No full textCan comprehensive specialised end-of-life care be provided at home? Lessons from a study of an innovative consultant-led community service in the UK
No full textThe Midhurst Macmillan Specialist Palliative Care Service (MMSPCS) is a UK, medical consultant-led,
multidisciplinary team aiming to provide round-the-clock advice and care, including specialist interventions, in the home, community hospitals and care homes. Of 389 referrals in 2010/11, about 85% were for cancer, from a population of about 155 000. Using a mixed method approach, the evaluation comprised: a retrospective analysis of secondary-care use in the last year of life; financial evaluation of the MMSPCS using an Activity Based Costing approach; qualitative interviews with patients, carers, health and social care staff and MMSPCS staff and volunteers; a postal survey of General Practices; and a postal survey of bereaved caregivers using the MMSPCS. The mean cost is about 3000 GBP (3461 EUR) per patient with mean cost of interventions for cancer patients in the last year of life 1900 GBP (2192 EUR). Post-referral, overall costs to the system are similar for MMSPCS and hospice-led models; however, earlier referral avoided around 20% of total costs in the last year of life. Patients and carers reported positive experiences of support, linked to the flexible way the service
worked. Seventy-one per cent of patients died at home. This model may have application elsewhere
Association of protein kinase C alpha (PRKCA) gene with multiple sclerosis in a UK population
No full textTwin, family and adoption studies suggest that susceptibility to multiple sclerosis is substantially mediated by genetic factors. Linkage to human chromosome 17q, homologous to a locus linked to experimental animal models of multiple sclerosis, has been widely replicated and the region likely to harbour a multiple sclerosis susceptibility gene has recently been refined to a 2.5 Mb region of 17q22-24. The candidate multiple sclerosis susceptibility gene, protein kinase C alpha (PRKCA), maps within this interval and association with 35 single-nucleotide polymorphism (SNP) markers, spanning the gene with a median spacing of 7.8 kb, was tested using a case-control approach. Single-marker genotype and estimated haplotype frequencies were compared in UK unrelated cases with multiple sclerosis (n = 184) and healthy controls (n = 340) in order to investigate association with susceptibility to disease. A haplotype of two SNPs mapping to the proximal region of the gene showed evidence for association with susceptibility (Bonferroni-corrected P value = 1.1 × 10-5). These findings suggest that further investigation of the PRKCA gene is warranted, particularly in cohorts with evidence of linkage to 17q22. Most of the SNPs investigated in this study were intronic and screening to identify disease-associated functional mutations is now required. Our results suggest that the promoter and proximal gene region should be not only included but prioritized in any screening strategy
Prevalence, treatment and correlates of depression in multiple sclerosis
No full textBackgroundThe prevalence of depression in Multiple Sclerosis (MS) is often assessed by administering patient reported outcome measures (PROMs) examining depressive symptomatology to population cohorts; a recent review summarised 12 such studies, eight of which used the Hospital Anxiety and Depression Scale-Depression (HADS-D). In clinical practice, depression is diagnosed by an individual structured clinical interview; diagnosis often leads to treatment options including antidepressant medication. It follows that an MS population will include those whose current depressive symptoms meet threshold for depression diagnosis, plus those who previously met diagnostic criteria for depression and have been treated such that depressive symptoms have improved below that threshold. We examined a large MS population to establish a multi-attribute estimate of depression, taking into account probable depression on HADS-D, as well as anti-depressant medication use and co-morbidity data reporting current treatment for depression. We then studied associations with demographic and health status measures and the trajectories of depressive symptoms over time.MethodsParticipants were recruited into the UK-wide Trajectories of Outcome in Neurological Conditions-MS (TONiC-MS) study, with demographic and disease data from clinical records, PROMs collected at intervals of at least 9 months, as well as co-morbidities and medication. Interval level conversions of PROM data followed Rasch analysis. Logistic regression examined associations of demographic characteristics and symptoms with depression. Finally, a group-based trajectory model was applied to those with depression.ResultsBaseline data in 5633 participants showed the prevalence of depression to be 25.3% (CI: 24.2-26.5). There were significant differences in prevalence by MS subtype: relapsing 23.2% (CI: 21.8- 24.5), primary progressive 25.8% (CI: 22.5-29.3), secondary progressive 31.5% (CI: 29.0-34.0); disability: EDSS 0-4 19.2% (CI: 17.8-20.6), EDSS ≥4.5 31.9% (CI: 30.2-33.6); and age: 42-57 years 27.7% (CI: 26.0-29.3), above or below this range 23.1% (CI: 21.6-24.7). Fatigue, disability, self-efficacy and self esteem correlated with depression with a large effect size (>.8) whereas sleep, spasticity pain, vision and bladder had an effect size >.5. The logistic regression model (N=4938) correctly classified 80% with 93% specificity: risk of depression was increased with disability, fatigue, anxiety, more comorbidities or current smoking. Higher self-efficacy or self esteem and marriage reduced depression. Trajectory analysis of depressive symptoms over 40 months in those with depression (N=1096) showed three groups: 19.1% with low symptoms, 49.2% with greater symptoms between the threshold of possible and probable depression, and 31.7% with high depressive symptoms. 29.9% (CI: 27.6-32.3) of depressed subjects were untreated, conversely of those treated, 26.1% still had a symptom level consistent with a probable case (CI: 23.5-28.9).ConclusionA multi-attribute estimate of depression in MS is essential because using only screening questionnaires, diagnoses or antidepressant medication all under-estimate the true prevalence. Depression affects 25.3% of those with MS, almost half of those with depression were either untreated or still had symptoms indicating probable depression despite treatment. Services for depression in MS must be pro-active and flexible, recognising the heterogeneity of outcomes and reaching out to those with ongoing symptoms
