King's College, Aberdeen

About: King's College, Aberdeen is a based out in . It is known for research contribution in the topics: Poison control & Sedimentary depositional environment. The organization has 712 authors who have published 918 publications receiving 25421 citations. The organization is also known as: King's College, Aberdeen & The University and King's College of Aberdeen.

Experimental and numerical investigations on the use of polymer Hopkinson pressure bars

Abstract: Split Hopkinson pressure bar (SHPB) testing has traditionally been carried out using metal bars. For testing low stiffness materials such as rubbers or low strength materials such as low density cellular solids considered primarily herein, there are many advantages to replacing the metal bars with polymer bars. An investigation of a number of aspects associated with the accuracy of SHPB testing of these materials is reported. Test data are used to provide qualitative comparisons of accuracy using different bar materials and wave-separation techniques. Sample results from SHPB tests are provided for balsa, Rohacell foam and hydroxyl-terminated polybutadiene. The techniques used are verified by finite-element (FE) analysis. Experimentally, the material properties of the bars are determined from impact tests in the form of a complex elastic modulus without curve fitting to a rheological model. For the simulations, a rheological model is used to define the bar properties by curve fitting to the experimentally derived properties. Wave propagation in a polymer bar owing to axial impact of a steel bearing ball is simulated. The results indicate that the strain histories can be used to determine accurately the viscoelastic properties of polymer bars. An FE model of the full viscoelastic SHPB set-up is then used to simulate tests on hyperelastic materials.

Short-term longitudinal evaluation of cerebral blood flow in mild Alzheimer's disease.

Abstract: The aim of this study was to estabilish whether subtle changes in regional cerebral blood flow (rCBF) can be detected in patients with mild Alzheimer's disease (AD) over a period as short as three months. Aprospective evaluation of rCBF changes with HMPAO SPECT at baseline and after 3 and 6 months was carried out. Standard clinical dementia tests were performed in parallel. The study enrolled 13 patients with mild probable AD from an outpatient memory clinic. SPECT data collected at baseline and after three months were compared using Statistical Parametric Mapping (SPM). Significant clusters of rCBF decrement in the medial part of the temporal lobe in both hemispheres, in the orbital part of the right frontal lobe and in the inferior part of the right parietal lobe were observed. No significant differences were found using a region of interest (ROI) analysis. After six months SPM analysis showed larger clusters of significant decrement in the same areas. ROI analysis was now sensitive to the rCBF changes and significant differences were shown in all brain regions except the temporal lobes. SPM analysis of SPECT data can detect significant changes in rCBF in mild AD over a short time interval. This method might be of potential advantage for the early diagnosis of AD and for its differentiation from stable cognitive impairments.