Deformation and failure of rock samples probed by T1 and T2 relaxation.
The objective of the study was to pinpoint the effect of stress induced rock matrix alterations on NMR-wireline-log measurements by means of laboratory T1 and T2 relaxation time measurements. The research activities were subdivided into two major parts: NMR relaxation measurements on a brine saturated outcrop sandstone (Red Wildmoor Sandstone) during uniaxial compressional tests and NMR relaxation measurements on artificial sandstone samples prepared with defined crack patterns. T1-measurements performed on Red Wildmoor samples during compaction showed a decrease in the mean relaxation rate 1/exp<ln (T1) up to a point assumed to characterize the yield strength of the rock. The rate decreased most probably as a result of the compaction of micropores. This trend was reversed when the rock failed. The relaxation rate increased again, most probably through the generation of fresh mineral surfaces at broken cementations or grain contacts. T2-relaxation was measured on artificial sandstone samples using CPMG pulse sequences with echo times between 175 micros and 1400 micros. Samples with larger crack volumes and crack orientation orthogonal to the B0-field showed consistently smaller exp<ln (T2) than the samples without any cracks. Further calculations indicate that internal magnetic field gradients were largest for samples having a larger number of cracks and crack orientations orthogonal to the B0-field.
The dependence on magnetic field strength of correlated internal gradient relaxation time distributions in heterogeneous materials.
Magnetic susceptibility differences in porous media produce local gradients within the pore space. At high magnetic fields, these inhomogeneities have the potential to greatly affect nuclear magnetic resonance measurements. We undertake a study using a new NMR technique to measure the internal gradients present in highly heterogeneous samples over a wide range of magnetic field strengths. Our results show that even at ultra-high fields there can exist signal at internal gradient strengths sufficiently small that techniques for suppressing unwanted side effects have the possibility to be used. Our findings encourage the use of these high and ultra-high field strengths for a broader range of samples. Our results also give experimental evidence to support the theory of internal gradient scaling as a function of field strength within pores.
Realist Review of Programs, Policies, and Interventions to Enhance the Social, Emotional, and Spiritual Well-Being of Aboriginal and Torres Strait Islander Young People Living in Out-of-Home Care
The child protection system in Australia includes out-of-home care (OoHC) for children and young people at risk of harm and neglect. In Australia, Aboriginal and Torres Strait Islander children and young people are 9 times more likely to be placed in care than non-Aboriginal young people (Australian Institute of Health and Welfare, 2015). Australia’s history of colonization and subsequent policies have caused trauma to individuals, families, and communities and resulted in poor physical and mental health and mistrust of services. This review was undertaken to identify programs and policies currently in place that aim to improve the mental health and well-being of this vulnerable population. It provides an analysis of both the strengths of the current system as well as what has been inadequately addressed based on literature in the area.By incorporating an Aboriginal perspective, this review focuses on social, emotional, and spiritual well-being (SESWB) and the aspects of a child’s life and community that promote this. A realist review of the academic and grey literature was conducted in 2014. It included an extensive search of government and non-government (NGO) publications. The review identified nine programs or policies that are designed to improve the SESWB of Aboriginal young people in OoHC in local and international settings. These are the Aboriginal and Torres Strait Islander Child Placement Principle, cultural support plans, Aboriginal Community Controlled Organisations (ACCOs), family group decision-making, therapeutic care, and Panyappi Mentoring Program. Given that culturally competent service provision is important to SESWB, the review concludes that an increase in monitoring and evaluation is necessary to determine the effectiveness of programs and ensure their implementation and sustainability when warranted. Policy and research work is needed to adapt and devise programs promoting the SESWB of Aboriginal young people (at both the individual and system levels), determine their effectiveness, and ensure they are sustained when warranted.