Surveillance Technology in Dementia Care: Implicit Assumptions and Unresolved Tensions

This paper examines the concept of “Surveillance Technology [ST]” as it is used in ageing and dementia research but which suffers from poor definition. We attempt to clarify this imprecision by contextualizing a brief history of the development of ST and provide a summary of the research in this area. We contrast this with the responses provided by a public and patient involvement group of people living with a dementia diagnosis, or experience of supporting people with dementia. ST operates in multiple interacting ways, all of which need to be taken into account in research, public and policy debate. As a technology it is often seen as a way of assisting individuals and therefore classified as an Assistive Technology [AT]. However, the meaning of ST used in dementia care has pragmatic implications beyond the meeting of the needs for “safety and independence”; ideas which is often used to justify its use. We argue that there is need to interrogate the terms “Surveillance” and “Technology” more carefully if ST is to be considered as empowering for people with dementia. This tension is brought out in the accounts present in a group discussion on ST and its use. This paper argues that there needs to be an acknowledgement that the purposes of such technologies need to be regularly reviewed in order for society to keep up with the rapidly changing pace of technology and the changing needs of users

Large-displacement, hydrothermal frictional properties of DFDP-1 fault rocks, Alpine Fault, New Zealand: Implications for deep rupture propagation

©2016. The Authors. The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65-75% of the total relative motion between the Australian and Pacific plates. Here we present data on the hydrothermal frictional properties of Alpine Fault rocks that surround the principal slip zones (PSZ) of the Alpine Fault and those comprising the PSZ itself. The samples were retrieved from relatively shallow depths during phase 1 of the Deep Fault Drilling Project (DFDP-1) at Gaunt Creek. Simulated fault gouges were sheared at temperatures of 25, 150, 300, 450, and 600°C in order to determine the friction coefficient as well as the velocity dependence of friction. Friction remains more or less constant with changes in temperature, but a transition from velocity-strengthening behavior to velocity-weakening behavior occurs at a temperature of T = 150°C. The transition depends on the absolute value of sliding velocity as well as temperature, with the velocity-weakening region restricted to higher velocity for higher temperatures. Friction was substantially lower for low-velocity shearing (V < 0.3 μm/s) at 600°C, but no transition to normal stress independence was observed. In the framework of rate-and-state friction, earthquake nucleation is most likely at an intermediate temperature of T = 300°C. The velocity-strengthening nature of the Alpine Fault rocks at higher temperatures may pose a barrier for rupture propagation to deeper levels, limiting the possible depth extent of large earthquakes. Our results highlight the importance of strain rate in controlling frictional behavior under conditions spanning the classical brittle-plastic transition for quartzofeldspathic compositions

Temperature-dependent frictional properties of heterogeneous Hikurangi Subduction Zone input sediments, ODP Site 1124

The Hikurangi Subduction Zone (HSZ), New Zealand, accommodates westward subduction of the Pacific Plate. Where imaged seismically, the shallow HSZ décollement (<10–15 km depth) occurs within or along the upper contact of Late Cretaceous-Paleogene (70–32 million-year-old) sediments. The frictional properties of Paleogene sediments recovered from Ocean Drilling Program Leg 181, Site 1124 were measured at 60 MPa effective normal stress and varying sliding velocities (V = 0.3–30 µm/s) and temperatures (T = 25–225 °C). Velocity-stepping experiments were conducted at temperatures of 25 °C, 75 °C, 150 °C, and 225 °C to determine the friction rate parameter (a–b). Paleocene and Oligocene clay-bearing nannofossil chalks (μ = 0.45–0.61) and a middle Eocene clayey nannofossil chalk (μ = 0.35–0.51) are frictionally stronger than smectite-bearing Eocene clays (μ = 0.16–0.31). With increasing temperature, chalks show rate-strengthening to rate-weakening frictional stability trends; clays show rate-weakening and rate-neutral to rate-strengthening frictional stability trends. The results obtained from Site 1124 sediments indicate that: (1) fault-zone weakness may not require pore-fluid overpressures; (2) clays and chalks can host frictional instabilities; and (3) heterogeneous frictional properties can promote variable slip behaviour

Fault zone fabric and fault weakness

Geological and geophysical evidence suggests that some crustal faults are weak1–6 compared to laboratory measurements of frictional strength7. Explanations for fault weakness include the presence of weak minerals4, high fluid pressures within the fault core8,9 and dynamic processes such as normal stress reduction10, acoustic fluidization11 or extreme weakening at high slip velocity12–14. Dynamic weakening mechanisms can explain some observations; however, creep and aseismic slip are thought to occur on weak faults, and quasi-static weakening mechanisms are required to initiate frictional slip on mis-oriented faults, at high angles to the tectonic stress field. Moreover, the maintenance of high fluid pressures requires specialized conditions15 and weak mineral phases are not present in sufficient abundance to satisfy weak fault models16, so weak faults remain largely unexplained. Here we provide laboratory evidence for a brittle, frictional weakening mechanism based on common fault zone fabrics. We report on the frictional strength of intact fault rocks sheared in their in situ geometry. Samples with well-developed foliation are extremely weak compared to their powdered equivalents. Micro- and nanostructural studies show that frictional sliding occurs along very fine-grained foliations composed of phyllosilicates (talc and smectite). When the same rocks are powdered, frictional strength is high, consistent with cataclastic processes. Our data show that fault weakness can occur in cases where weak mineral phases constitute only a small percentage of the total fault rock and that low friction results from slip on a network of weak phyllosilicate-rich surfaces that define the rock fabric. The widespread documentation of foliated fault rocks along mature faults in different tectonic settings and from many different protoliths4,17–19 suggests that this mechanism could be a viable explanation for fault weakening in the brittle crust