Direct Evidence for Fluid Pressure, Dilatancy, and Compaction Affecting Slip in Isolated Faults

Earthquake instability occurs as a result of strength loss during sliding on a fault. It has been known for over 50 years that fault compaction or dilatancy may cause significant weakening or strengthening by dramatically changing the fluid pressure trapped in faults. Despite this fundamental importance, we have no real understanding of the exact conditions that lead to compaction or dilation during nucleation or rupture. To date, no direct measurements of pore pressure changes during slip in hydraulically isolated faults have been reported. We show direct examples of fluid pressure variations during nucleation and rupture using a miniature pressure transducer embedded in an experimental fault. We demonstrate that fluids not only are significant in controlling fault behavior but can provide the dominant mechanism controlling fault stability. The effect of fluid pressure changes can exceed frictional variations predicted by rate‐ and state‐dependent friction laws, exerting fundamental controls on earthquake rupture initiation

“Structural Dissatisfaction”: academics on safari in the novels of Jennifer Egan

Jennifer Egan's acclaimed 2010 novel, A Visit from the Goon Squad, is a text populated by a disproportionately high number of, often unfulfilled, postgraduate researchers: “I'm in the PhD program at Berkeley”, proclaims Mindy; “Joe, who hailed from Kenya [...] was getting his PhD in robotics at Columbia”; “Bix, who's black, is spending his nights in the electrical-engineering lab where he's doing his PhD research”; while only Rebecca “was an academic star”. Indeed, in this text, academia seems a place of misery, of “harried academic slaving”, and, ultimately, of “immaturity and disastrous choices”. Over the course of this article I will demonstrate that, in fact, Egan's critique of the university is an immanent meta-critique. While the history of the campus novel is often premised on hermetically sealing the campus (the genre usually functions through an explicit focus on a delineated campus space or, at least, predominantly upon the social milieu of the academy), Egan's novels seem to play on bursting the very notions of inside and outside that facilitate this genre, blurring the boundaries between fiction and critique; the leeching of the university into everyday life. She also, simultaneously, however, critiques the structures of labour upon which much of the academy is founded. While I will move towards Egan's latest novel, A Visit From the Goon Squad, throughout this article I will make reference to her entire novelistic canon, demonstrating that the treatment of academics throughout cannot be viewed as merely incidental, even if the appearances of such characters are sporadic and diffuse

Standardising multi-agency safeguarding hubs (MASH): Building a framework to effectively identify and manage risk

MASH has been a feature of safeguarding practices in England and Wales since 2011, bringing safeguarding agencies together to effectively share information and prevent organizational silos. Core agencies include the police, social care, and health, with key features of co-location, joint decision-making and co-ordination. A standardised definition for MASH implementation does not exist, and this lack of a clear definition has meant various structures have emerged, impacting on safeguarding practices. This policy brief draws on workshops with a range of safeguarding practitioners between May and July 2022, about the challenges of collaborative working practices and how MASH can become more standardised. Whilst national standardisation is required, there needs to be flexibility when implementing guidelines, so that practices and processes reflect regional needs and resources

Dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates

To investigate differences in the frictional behavior between initially bare rock surfaces of serpentinite and powdered serpentinite (“gouge”) at subseismic to seismic slip rates, we conducted single-velocity step and multiple-velocity step friction experiments on an antigorite-rich and lizardite-rich serpentinite at slip rates (V) from 0.003 m/s to 6.5 m/s, sliding displacements up to 1.6 m, and normal stresses (σn) up to 22 MPa for gouge and 97 MPa for bare surfaces. Nominal steady state friction values (μnss) in gouge at V = 1 m/s are larger than in bare surfaces for all σn tested and demonstrate a strong σn dependence; μnss decreased from 0.51 at 4.0 MPa to 0.39 at 22.4 MPa. Conversely, μnss values for bare surfaces remained ∼0.1 with increasing σn and V. Additionally, the velocity at the onset of frictional weakening and the amount of slip prior to weakening were orders of magnitude larger in gouge than in bare surfaces. Extrapolation of the normal stress dependence for μnss suggests that the behavior of antigorite gouge approaches that of bare surfaces at σn ≥ 60 MPa. X-ray diffraction revealed dehydration reaction products in samples that frictionally weakened. Microstructural analysis revealed highly localized slip zones with melt-like textures in some cases gouge experiments and in all bare surfaces experiments for V ≥ 1 m/s. One-dimensional thermal modeling indicates that flash heating causes frictional weakening in both bare surfaces and gouge. Friction values for gouge decrease at higher velocities and after longer displacements than bare surfaces because strain is more distributed. Key Points Gouge friction approaches that of bare surfaces at high normal stress Dehydration reactions and bulk melting in serpentinite in < 1 m of slip Flash heating causes dynamic frictional weakening in gouge and bare surface

Community-Based Learning and critical community psychology practice: conducive and corrosive aspects

YesCommunity-Based Learning (CBL) has been more recently introduced into some psychology programmes in the UK than in the USA, where it has existed for a number of decades in the form of ‘service learning’. CBL holds promise as a means of promoting and developing critical community psychology practice, but there are risks involved in its acritical adoption in the psychology curriculum. If associated power dynamics are not considered, CBL has the capacity to serve neoliberal interests and perpetuate, rather than challenge, oppressive social relations. This article examines ways in which CBL can be both conducive and corrosive to critical community psychology practice. Drawing on interdisciplinary literature, it explores ways in which students participating in CBL can be vulnerable to exploitation – both as victims and perpetrators – through collusion and cultural voyeurism. Consideration is given to ways of resisting institutional and other pressures to comply uncritically with the demands of the ‘employability agenda’. These include the importance of facilitated reflective processes in associated modules, to consider aspects of the interactions of people and systems. The article concludes that whilst CBL is inherently risky and involves discomfort for students, this enables development of a more informed consciousness where truly participatory work evolves towards greater social justice

Stellar Structure Modeling using a Parallel Genetic Algorithm for Objective Global Optimization

Genetic algorithms are a class of heuristic search techniques that apply basic evolutionary operators in a computational setting. We have designed a fully parallel and distributed hardware/software implementation of the generalized optimization subroutine PIKAIA, which utilizes a genetic algorithm to provide an objective determination of the globally optimal parameters for a given model against an observational data set. We have used this modeling tool in the context of white dwarf asteroseismology, i.e., the art and science of extracting physical and structural information about these stars from observations of their oscillation frequencies. The efficient, parallel exploration of parameter-space made possible by genetic-algorithm-based numerical optimization led us to a number of interesting physical results: (1) resolution of a hitherto puzzling discrepancy between stellar evolution models and prior asteroseismic inferences of the surface helium layer mass for a DBV white dwarf; (2) precise determination of the central oxygen mass fraction in a white dwarf star; and (3) a preliminary estimate of the astrophysically important but experimentally uncertain rate for the ^12C(alpha,gamma)^16O nuclear reaction. These successes suggest that a broad class of computationally-intensive modeling applications could also benefit from this approach.Comment: 22 pages, minor changes, to appear in Journal of Computational Physics (JCPH2002-0129), software available at http://whitedwarf.org/parallel

Bio-optical anomalies in the world’s oceans: An investigation on the diffuse attenuation coefficients for downward irradiance derived from Biogeochemical Argo float measurements

Identification of oceanic regions characterized by particular optical properties is extremely important for ocean color applications. The departure from globally established bio-optical models (i.e., anomaly) introduces uncertainties in the retrieval of biogeochemical quantities from satellite observations. Thanks to an array of 105 Biogeochemical Argo floats acquiring almost daily downward irradiance measurements at selected wavelengths in the UV and blue region of the spectrum, we reexamined the natural variability of the spectral diffuse attenuation coefficients, Kd(λ), among the world’s oceans and compared them to previously established bio-optical models. The analysis of 2847 measurements of Kd(λ) at 380 and 490 nm, within the first optical depth, provided a classification of the examined regions into three groups. The first one included the Black Sea, a water body characterized by a very high content of coloured dissolved organic matter (CDOM). The second group was essentially composed by the subtropical gyres (Atlantic and Pacific Oceans), with optical properties consistent with previous models (i.e., no anomalies). High latitude (North Atlantic and Southern oceans) and temperate (Mediterranean Sea) seas formed the third group, in which optical properties departed from existing bio-optical models. Annual climatologies of the Kd(380)/Kd(490) ratio evidenced a persistent anomaly in the Mediterranean Sea, that we attributed to a higher-than-average CDOM contribution to total light absorption. In the North Atlantic subpolar gyre, anomalies were observed only in wintertime and were also attributed to high CDOM concentrations. In the Southern Ocean, the anomaly was likely related to high phytoplankton pigment packaging rather than to CDOM

Engaging stakeholder communities as body image intervention partners: The Body Project as a case example

© 2015 Elsevier Ltd Despite recent advances in developing evidence-based psychological interventions, substantial changes are needed in the current system of intervention delivery to impact mental health on a global scale (Kazdin & Blase, 2011). Prevention offers one avenue for reaching large populations because prevention interventions often are amenable to scaling-up strategies, such as task-shifting to lay providers, which further facilitate community stakeholder partnerships. This paper discusses the dissemination and implementation of the Body Project, an evidence-based body image prevention program, across 6 diverse stakeholder partnerships that span academic, non-profit and business sectors at national and international levels. The paper details key elements of the Body Project that facilitated partnership development, dissemination and implementation, including use of community-based participatory research methods and a blended train-the-trainer and task-shifting approach. We observed consistent themes across partnerships, including: sharing decision making with community partners, engaging of community leaders as gatekeepers, emphasizing strengths of community partners, working within the community's structure, optimizing non-traditional and/or private financial resources, placing value on cost-effectiveness and sustainability, marketing the program, and supporting flexibility and creativity in developing strategies for evolution within the community and in research. Ideally, lessons learned with the Body Project can be generalized to implementation of other body image and eating disorder prevention programs

Testate amoeba response to acid deposition in a Scottish peatland

Peatlands around the world are exposed to anthropogenic or volcanogenic sulphur pollution. Impacts on peatland microbial communities have been inferred from changes in gas flux but have rarely been directly studied. In this study, the impacts of sulphuric acid deposition on peatland testate amoebae were investigated by analysis of experimental plots on a Scottish peatland almost 7 years after acid treatment. Results showed reduced concentration of live amoebae and changes in community structure which remained significant even when differences in pH were accounted for. Several possible explanations for the impacts can be proposed including taphonomic processes and changes in plant communities. Previous studies have inferred a shift from methanogenic archaea to sulphate-reducing bacteria in sulphate-treated peats; it is possible that the impacts detected here might relate to this change, perhaps through testate amoeba predation on methanotrophs

Measurements of hydrogen, oxygen and carbon isotope variability in Sphagnum moss along a micro-topographical gradient in a southern Patagonian peatland

Peat archives offer a diverse range of physical and chemical proxies from which it is possible to study past environmental and ecological changes. Direct numerical calibration and verification is difficult so process-based and mechanistic studies are therefore required to establish and quantify links between environmental changes and their associated proxy-responses. Traditional ‘space-for-time’ calibrations provide a solution to this calibration problem, but are often unable to isolate a single environmental variable from other potentially confounding variables. In this study, we explored the potential of a site-specific ‘space-for-time’ approach applied to a hummock-hollow transect on an ombrotrophic raised bog in Patagonia, southern Chile. Coupled stable carbon, oxygen and hydrogen isotopic measurements were made on individual samples of Sphagnum moss cellulose and compared with plant-associated waters, local hydrology, temperature and relative humidity, sampled at the same points along the study transect. Results reveal a range of environmental responses, which were supported by plant-physiological models in the case of carbon and oxygen isotopes. For hydrogen isotopes, the results obtained from cellulose indicated a need for further research into hydrogen isotope fractionation in Sphagnum. We recommend conducting site-specific characterization of plant response to support the development of peat-based isotope records for palaeoenvironmental research, and where logistically possible, that monitoring is conducted over timescales appropriate to the time-integrative nature of the Sphagnum record