Oscillatory squeezing flow of a biological material

Rheologica Acta394409-41

Constitutive modelling of brain tissue for prediction of traumatic brain injury

To develop protective measures for crash situations, an accurate assessment of injury risk is required. By using a Finite Element (FE) model of the head, the mechanical behaviour of the brain can be predicted for any acceleration and improved injury criteria can be developed and implemented into safety standards. Many head models are based on a detailed geometrical description of the anatomical components. However, for reliable predictions of injury, also an accurate constitutive model for brain tissue is required that is applicable for large deformations and complex loading conditions that occur during an impact to the head. This chapter deals with constitutive modelling of brain tissue. Different approaches towards modelling of the mechanical response of biological tissues are discussed. A short overview of the large strain behaviour of brain tissue and constitutive models that have been developed for this material is given. A non-linear viscoelastic model for brain tissue is then discussed in more detail. The model is based on a multi-mode Maxwell model and consists of a non-linear elastic mode in combination with a number of viscoelastic modes. For this model, also a numerical implementation scheme is given. The influences of constitutive non-linearities of brain tissue in numerical head model simulations are shown by comparing the performance of the model of Hrapko et al. with a simplified version, based on neo-Hookean elastic behaviour, and a third non-linear constitutive model from literature

Has increasing the age for child passengers to wear child restraints improved the extent to which they are used? Results from an Australian focus group and survey study

Acknowledgement that many children in Australia travel in restraints that do not offer them the best protection has led to recent changes in legislation such that the type of restraint for children under 7 years is now specified. This paper reports the results of two studies (observational; focus group/ survey) carried out in the state of Queensland to evaluate the effectiveness of these changes to the legislation. Observations suggested that almost all of the children estimated as aged 0-12 years were restrained (95%). Analysis of the type of restraint used for target-aged children (0-6 year olds) suggests that the proportion using an age-appropriate restraint has increased by an estimated 7% since enactment of the legislation. However, around 1 in 4 children estimated as aged under 7 years were using restraints too large for good fit. Results from the survey and focus group suggested parents were supportive of the changes in legislation. Non-Indigenous parents agreed that the changes had been necessary, were effective at getting children into the right restraints, were easy to understand as well as making it clear what restraint to use with children. Moreover, they did not see the legislation as too complicated or too hard to comply with. Indigenous parents who participated in a focus group also regarded the legislation as improving children’s safety. However, they identified the cost of restraints as an important barrier to compliance. In summary, the legislation appears to have had a positive effect on compliance levels and on raising parental awareness of the need to restrain children child-specific restraints for longer. However, it would seem that an important minority of parents transition their children into larger restraints too early for optimal protection. Intervention efforts should aim to better inform these parents about appropriate ages for transition, especially from forward facing childseats. This could potentially be through use of other important transitions that occur at the same age, such as starting school. The small proportion of parents who do not restrain their children at all are also an important community sector to target. Finally, obtaining restraints presents a significant barrier to compliance for parents on limited incomes and interventions are needed to address this

The Effect of Cerebrospinal Fluid Thickness on Traumatic Spinal Cord Deformation

A spinal cord injury may lead to loss of motor and sensory function and even death. The biomechanics of the injury process have been found to be important to the neurological damage pattern, and some studies have found a protective effect of the cerebrospinal fluid (CSF). However, the effect of the CSF thickness on the cord deformation and, hence, the resulting injury has not been previously investigated. In this study, the effects of natural variability (in bovine) as well as the difference between bovine and human spinal canal dimensions on spinal cord deformation were studied using a previously validated computational model. Owing to the pronounced effect that the CSF thickness was found to have on the biomechanics of the cord deformation, it can be concluded that results from animal models may be affected by the disparities in the CSF layer thickness as well as by any difference in the biological responses they may have compared with those of humans.</p