Structural design for passenger safety

This thesis covers the design and analysis of a roll cage structure for use on a sports racing car. The method used to design and verify the roll structure was novel as small automotive companies tend to use evolution as a design tool. Evolutionary design works well for certain problems, however, is not well suited to major structural modifications. The method used in this report integrates the existing structure with the roll cage to improve the torsion stiffness and hence the handling of the vehicle. Careful integration of the roll cage with the rest of the chassis enabled the torsion stiffness to be increased by over 400 %. In addition the weight efficiency of the final chassis was increased over that of the original chassis by over 200 % . The investigation of the torsion stiffness was carried out using linear finite element analysis using the NASTRAN suite of programs. The second stage of the investigation was to develop this design into a crashworthy roll cage. The resulting model and design are presented in this report. The design of the crashworthy roll cage was carried out using non linear finite element analysis with N AS TRAN. The N AS TRAN results were then verified with a full structural test on the chassis. The results of the tests are presented and compared to the NASTRAN analysis results. Good correlation was achieved and the method showed promise for applications in the small automotive industries. The use of finite element analysis for the design of an integrated structure represented a novel application of a well established technique to an industry where experience is the main design tool. The results of the investigation were encouraging and a close correlation was achieved between the analysis and test results. Finite element analysis represents a relatively cheap and quick method of investigating the effect of structural changes. This method could be used for the design and development of new structures and would give a good indication of the effect of these changes. Small automotive companies, such as TVR, should find the technique particularly useful for both the design of new structures and for the modification of those already in use.MPhi

Attenuated Fatigue in Slow Twitch Skeletal Muscle during Isotonic Exercise in Rats with Chronic Heart Failure

During isometric contractions, slow twitch soleus muscles (SOL) from rats with chronic heart failure (chf) are more fatigable than those of sham animals. However, a muscle normally shortens during activity and fatigue development is highly task dependent. Therefore, we examined the development of skeletal muscle fatigue during shortening (isotonic) contractions in chf and sham-operated rats. Six weeks following coronary artery ligation, infarcted animals were classified as failing (chf) if left ventricle end diastolic pressure was >15mmHg. During isoflurane anaesthesia, SOL with intact blood supply was stimulated (1s on 1s off) at 30Hz for 15 min and allowed to shorten isotonically against a constant afterload. Muscle temperature was maintained at 37°C. In resting muscle, maximum isometric force (Fmax) and the concentrations of ATP and CrP were not different in the two groups. During stimulation, Fmax and the concentrations declined in parallel sham and chf. Fatigue, which was evident as reduced shortening during stimulation, was also not different in the two groups. The isometric force decline was fitted to a bi-exponential decay equation. Both time constants increased transiently and returned to initial values after approximately 200 s of the fatigue protocol. This resulted in a transient rise in baseline tension between stimulations, although this effect which was less prominent in chf than sham. Myosin light chain 2s phosphorylation declined in both groups after 100 s of isotonic contractions, and remained at this level throughout 15 min of stimulation. In spite of higher energy demand during isotonic than isometric contractions, both shortening capacity and rate of isometric force decline were as well or better preserved in fatigued SOL from chf rats than in sham. This observation is in striking contrast to previous reports which have employed isometric contractions to induce fatigue

Denisovan, modern human and mouse TNFAIP3 alleles tune A20 phosphorylation and immunity

Resisting and tolerating microbes are alternative strategies to survive infection, but little is known about the evolutionary mechanisms controlling this balance. Here genomic analyses of anatomically modern humans, extinct Denisovan hominins and mice revealed a TNFAIP3 allelic series with alterations in the encoded immune response inhibitor A20. Each TNFAIP3 allele encoded substitutions at non-catalytic residues of the ubiquitin protease OTU domain that diminished IκB kinase-dependent phosphorylation and activation of A20. Two TNFAIP3 alleles encoding A20 proteins with partial phosphorylation deficits seemed to be beneficial by increasing immunity without causing spontaneous inflammatory disease: A20 T108A;I207L, originating in Denisovans and introgressed in modern humans throughout Oceania, and A20 I325N, from an N-ethyl-N-nitrosourea (ENU)-mutagenized mouse strain. By contrast, a rare human TNFAIP3 allele encoding an A20 protein with 95% loss of phosphorylation, C243Y, caused spontaneous inflammatory disease in humans and mice. Analysis of the partial-phosphorylation A20 I325N allele in mice revealed diminished tolerance of bacterial lipopolysaccharide and poxvirus inoculation as tradeoffs for enhanced immunity.</p

Effect of earthworms on soil physico-hydraulic and chemical properties, herbage production, and wheat growth on arable land converted to ley

Effects of earthworms on soil physico-hydraulic properties, herbage production and wheat growth in long-term arable soils following conversion to ley were investigated. Seven intact soil monoliths were collected from each of four arable fields. One monolith per field served as a control. The other six were defaunated by deep-freezing; three were left defaunated (DeF) and three (DeF+E) were repopulated with earthworms to mimic pasture field density and diversity. The monoliths were planted with a grass-clover ley and inserted into pre-established ley strips in their original fields for 12 months. Hydraulic conductivity measurements at -0.5 cm tension (K0.5) were taken five times over the year. K0.5 significantly increased in summer 2017 and spring 2018 and decreased in winter 2017-18. K0.5 was significantly greater (47%) for DeF+E than DeF monoliths. By the end of the experiment, pores >1 mm diameter made a significantly greater contribution to water flow in DeF+E (98%) than DeF (95%) monoliths. After only a year of arable to ley conversion, soil bulk density significantly decreased (by 6%), and organic matter (OM) content increased (by 29%) in the DeF treatments relative to the arable soil. Earthworms improved soil quality further. Compared to DeF monoliths, DeF+E monoliths had significantly increased water-holding capacity (by 9%), plant-available water (by 21%), OM content (by 9%), grass-clover shoot dry biomass (by 58%), water-stable aggregates > 250 µm (by 15%) and total N (by 3.5%). In a wheat bioassay following the field experiment, significantly more biomass (20%) was produced on DeF+E than DeF monolith soil, likely due to the changed soil physico-hydraulic properties. Our results show that earthworms play a significant role in improvements to soil quality and functions brought about by arable to ley conversion, and that augmenting depleted earthworm populations can help the restoration of soil qualities adversely impacted by intensive agriculture