Bed-load Transport of Mixed-size Sediment: Fractional Transport Rates, Bed Forms, and the Development of a Coarse Bed-surface Layer

Fractional transport rates, bed surface texture, and bed configuration were measured after a mixed size sediment had reached an equilibrium transport state for seven different flow strengths in a recirculating laboratory flume. Fractional transport rates were also measured at the beginning of each run when the bed was well mixed and planar. The start-up observations allow us to describe the variation of fractional transport rates with bed shear stress for a constant bed surface texture and bed configuration. The start-up and equilibrium observations together allow, for the first time, an unambiguous description of the mutual adjustment among the transport, the bed configuration, and the bed surface, as the transport system moves toward equilibrium. We find that a substantial interaction exists among the transport, bed surface, and bed configuration. Bed forms and a coarse surface layer coexist over a range of bed shear stress. Under some flow conditions the size and shape of the bed forms are controlled by the presence of the coarse surface layer. At higher flows the coarse surface layer is eliminated by scour in the lee of the bed forms. If the bed surface is defined as that over which the bed forms move, a coherent relation between the bed surface texture and the transport grain size distribution may be defined. At equilibrium the transport rates of all fractions were not equally mobile, defined as identical transport and bed grain size distributions, although equal mobility was approached for runs in which the bed shear stress was more than twice that for initial motion of the mixture. Under some flow conditions the transport was observed to adjust away from equal mobility as the bed adjusted from a well-mixed start-up condition to an equilibrium state. Development of a partial static armor, wherein some individual grains become essentially immobile even though other grains in the same fraction remain in transport, is suggested to explain these adjustments between the transport and bed surface grain size distributions. Constraints on equilibrium mixed size sediment transport are defined. The special conditions for which equal mobility must hold and the relevance to natural conditions of flume results and the equal mobility concept are discussed

Persistence of Armor Layers in Gravel-Bed Streams

Streambed surfaces are typically coarsened, or armored, at low flows, but there is little evidence of their condition during floods, when significant hydraulic and ecologic disturbance occurs. Some flume experiments have been used to conclude that armor layers wash out during floods, although other experiments have produced a persistent armor layer. In the absence of clear field or flume evidence, we use a surface-based transport model in an inverse prediction of surface grain size as a function of transport rates observed in the field. The predicted surface grain size matches that observed at low flow and indicates that low-flow armor layers persist at large flows. In the field, transport grain size increases with transport rate, reducing or eliminating adjustments in bed surface grain size as flow and transport increase. A persistent armor layer considerably simplifies the prediction of sediment transport, hydraulic roughness, and habitat disturbance during floods

Using participatory and creative methods to facilitate emancipatory research with people facing multiple disadvantage: a role for health and care professionals

Participatory and creative research methods are a powerful tool for enabling active engagement in the research process of marginalised people. It can be particularly hard for people living with multiple disadvantage, such as disabled people from ethnic minority backgrounds, to access research projects that are relevant to their lived experience. This article argues that creative and participatory methods facilitate the co-researchers’ engagement in the research process, which thus becomes more empowering. Exploring the congruence of these methods with their professional ethos, health and care professionals can use their skills to develop them further. Both theory and practice examples are presented

Surface-enhanced Raman scattering from surface and subsurface oxygen species at microscopically well-defined Ag surfaces

Ag(111) and Ag(110) surfaces exposed to oxygen at elevated temperatures (∼800 K) exhibit strongly enhanced Raman bands at 803 and 627 cm−1 which are attributed to O atoms strongly chemisorbed on the surface (Oγ) or held in subsurface sites (Oβ), respectively. In contrast to usual experience, surface-enhanced Raman scattering is occurring here under well-defined conditions up to temperatures of 900 K which is attributed to the joint operation of delocalized electromagnetic enhancement (caused by surface roughness provided by oxygen-induced faceting) and local resonance due to the particular electronic properties of the surface sites

Partial Transport of a Sand-Gravel Sediment

Grains of a single size within a mixed-size bed are entrained over a range of flows. Within this range some grains exposed on the bed surface are active (entrained at least once over the duration of a transport event), while the remaining surface grains are immobile, a condition we define as partial transport. We demonstrate the existence and domain of partial transport using observations of grain entrainment on time series of bed photographs of flume experiments with a widely sorted sand/gravel mixture. The active proportion of the bed surface increases with bed shear stress τ0. At a given τ0, 90% of the active grains are entrained when the cumulative mass transported exceeds approximately 4 times the active mass on the bed. Mobilization of grains in a size fraction increases from 10% to 90% over a range of τ0 of a factor of 2. The bounds of this range increase with grain size Di so that at a given τ0, sizes over a range of a factor of 4 are in a state of partial transport. Fractional transport rates are independent of Di for fully mobilized fractions and decrease rapidly with Di for partially mobile fractions. Partial transport is associated with substantial transport rates of finer, fully mobile sizes, limits both the rate and size distribution of grain exchange with the bed subsurface, and may be the dominant transport condition in many gravel-bed rivers

Next-generation seismic experiments – II: wide-angle, multi-azimuth, 3-D, full-waveform inversion of sparse field data

3-D full-waveform inversion (FWI) is an advanced seismic imaging technique that has been widely adopted by the oil and gas industry to obtain high-fidelity models of P-wave velocity that lead to improvements in migrated images of the reservoir. Most industrial applications of 3-D FWI model the acoustic wavefield, often account for the kinematic effect of anisotropy, and focus on matching the low-frequency component of the early arriving refractions that are most sensitive to P-wave velocity structure. Here, we have adopted the same approach in an application of 3-D acoustic, anisotropic FWI to an ocean-bottom-seismometer (OBS) field data set acquired across the Endeavour oceanic spreading centre in the northeastern Pacific. Starting models for P-wave velocity and anisotropy were obtained from traveltime tomography; during FWI, velocity is updated whereas anisotropy is kept fixed. We demonstrate that, for the Endeavour field data set, 3-D FWI is able to recover fine-scale velocity structure with a resolution that is 2–4 times better than conventional traveltime tomography. Quality assurance procedures have been employed to monitor each step of the workflow; these are time consuming but critical to the development of a successful inversion strategy. Finally, a suite of checkerboard tests has been performed which shows that the full potential resolution of FWI can be obtained if we acquire a 3-D survey with a slightly denser shot and receiver spacing than is usual for an academic experiment. We anticipate that this exciting development will encourage future seismic investigations of earth science targets that would benefit from the superior resolution offered by 3-D FWI

UK psychiatrists' experience of withdrawal of antipsychotics prescribed for challenging behaviours in adults with intellectual disabilities and/or autism.

BACKGROUND: A high proportion of adults with intellectual disabilities are prescribed off-licence antipsychotics in the absence of a psychiatric illness. The National Health Service in England launched an initiative in 2016, 'Stopping over-medication of people with a learning disability [intellectual disability], autism or both' (STOMP), to address this major public health concern. AIMS: To gain understanding from UK psychiatrists working with adults with intellectual disabilities on the successes and challenges of withdrawing antipsychotics for challenging behaviours. METHOD: An online questionnaire was sent to all UK psychiatrists working in the field of intellectual disability (estimated 225). RESULTS: Half of the 88 respondents stated that they started withdrawing antipsychotics over 5 years ago and 52.3% stated that they are less likely to initiate an antipsychotic since the launch of STOMP. However, since then, 46.6% are prescribing other classes of psychotropic medication instead of antipsychotics for challenging behaviours, most frequently the antidepressants. Complete antipsychotic discontinuation in over 50% of patients treated with antipsychotics was achieved by only 4.5% of respondents (n = 4); 11.4% reported deterioration in challenging behaviours in over 50% of patients on withdrawal and the same proportion (11.4%) reported no deterioration. Only 32% of respondents made the diagnosis of psychiatric illness in all their patients themselves. Family and paid carers' concern, lack of multi-agency and multidisciplinary input and unavailability of non-medical psychosocial intervention are key reported factors hampering the withdrawal attempt. CONCLUSIONS: There is an urgent need to develop national guidelines to provide a framework for systematic psychotropic drug reviews and withdrawal where possible

Decolonising occupational science education through learning activities based on a study from the Global South

If occupational science education is to become more globally relevant, it must highlight more voices and practices from diverse communities. Learning about occupational justice from the perspectives of Global South communities addresses cognitive injustice and the need to decolonise occupational science education. This paper offers some critical reflections concerning the author’s pedagogic approach, and the ways his research about olive growing in Palestine (Simaan, 2018) informed students’ learning about occupational justice. It focuses on the processes in which students and lecturers engaged within a decolonising approach to occupational science education. A learning activity based on pedagogical processes of ‘conscientization’ (Freire, 1996), critical reflexivity (Whiteford & Townsend, 2011) and intercultural translation (Santos, 2014) is discussed, and lessons learnt by lecturer and students about themselves, their communities, and occupational science are reflected upon. Selected students’ reflections, which illustrate how they positioned themselves in relation to the community studied, and how they interrogated their own reactions to learning about daily lives in Palestine, are discussed. These processes demonstrate the benefits of highlighting local knowledge on occupational justice produced by Global South groups, and how this knowledge might begin to address cognitive injustice and the need to decolonise occupational science pedagogy. More empirical and theoretical work is needed in occupational science education regarding intercultural translations concerning occupational justice, and means of doing and knowing from diverse Global South perspectives