Entrainment, motion and deposition of coarse particles transported by water over a sloping mobile bed

In gravel-bed rivers, bedload transport exhibits considerable variability in time and space. Recently, stochastic bedload transport theories have been developed to address the mechanisms and effects of bedload transport fluctuations. Stochastic models involve parameters such as particle diffusivity, entrainment and deposition rates. The lack of hard information on how these parameters vary with flow conditions is a clear impediment to their application to real-world scenarios. In this paper, we determined the closure equations for the above parameters from laboratory experiments. We focused on shallow supercritical flow on a sloping mobile bed in straight channels, a setting that was representative of flow conditions in mountain rivers. Experiments were run at low sediment transport rates under steady nonuniform flow conditions (i.e., the water discharge was kept constant, but bedforms developed and migrated upstream, making flow nonuniform). Using image processing, we reconstructed particle paths to deduce the particle velocity and its probability distribution, particle diffusivity, and rates of deposition and entrainment. We found that on average, particle acceleration, velocity and deposition rate were responsive to local flow conditions, whereas entrainment rate depended strongly on local bed activity. Particle diffusivity varied linearly with the depth-averaged flow velocity. The empirical probability distribution of particle velocity was well approximated by a Gaussian distribution when all particle positions were considered together. In contrast, the particles located in close vicinity to the bed had exponentially distributed velocities. Our experimental results provide closure equations for stochastic or deterministic bedload transport models.Comment: Submitted to Journal of Geophysical Researc

Assessing the probability of patients reoffending after discharge from low to medium secure forensic mental health services: An inductive prevention paradox

Citizens of developed societies are troubled by those who commit ‘irrational' crimes against the person. Reoffending by ex-patients following their release from secure mental health services triggers particularly intense angst when amplified by media and political scrutiny. Forensic mental health service providers are expected to minimise the occurrence of such transgressions by releasing only those patients who are judged acceptably unlikely to reoffend. However, reoffending probabilities can only be estimated by observing behaviour in secure institutional settings designed specifically to prevent patients from transgressing. The article explores this ‘inductive prevention paradox' which arises when the implementation of measures designed to avoid an adverse event obscures direct observation of what might have happened if prophylaxis had not been attempted. The analysis presented draws on data obtained in 1999–2003 from two qualitative studies in medium to low secure UK institutions, one providing forensic mental health services and the other forensic learning disability services. We explored the views of 56 staff members and 21 patients about risk management in forensic services and undertook additional 25 staff interviews for case studies of the 21 patients. The wider applicability of the inductive prevention paradox will be considered in the Discussion. We argue that the prognostic limitations arising from prevention have been underestimated by policy makers and in official inquiries; and that the prevailing personal risk assessment framework needs to be complemented by greater attention to the environments which patients will be discharged into

Screening for health risks: A social science perspective

Health screening promises to reduce risks to individuals via probabilistic sifting of populations for medical conditions. The categorisation and selection of 'conditions' such as cardiovascular events, dementia and depression for screening itself requires prior interpretive labour which usually remains unexamined. Screening systems can take diverse organisational forms and varying relationships to health status, as when purported disease precursors, for example 'pre-cancerous' polyps, or supposed risk factors, such as high cholesterol themselves, become targets for screening. Screening at best yields small, although not necessarily unworthwhile, net population health gains. It also creates new risks, leaving some individuals worse-off than if they had been left alone. The difficulties associated with attempting to measure small net gains through randomised controlled trials are sometimes underestimated. Despite endemic doubts about its clinical utility, bibliometric analysis of published papers shows that responses to health risks are coming to be increasingly thought about in terms of screening. This shift is superimposed on a strengthening tendency to view health through the lens of risk. It merits further scrutiny as a societal phenomenon

Method of remotely characterizing thermal properties of a sample

A sample in a wind tunnel is radiated from a thermal energy source outside of the wind tunnel. A thermal imager system, also located outside of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample

Detection of bondline delaminations in multilayer structures with lossy components

The detection of bondline delaminations in multilayer structures using ultrasonic reflection techniques is a generic problem in adhesively bonded composite structures such as the Space Shuttles's Solid Rocket Motors (SRM). Standard pulse echo ultrasonic techniques do not perform well for a composite resonator composed of a resonant layer combined with attenuating layers. Excessive ringing in the resonant layer tends to mask internal echoes emanating from the attenuating layers. The SRM is made up of a resonant steel layer backed by layers of adhesive, rubber, liner and fuel, which are ultrasonically attenuating. The structure's response is modeled as a lossy ultrasonic transmission line. The model predicts that the acoustic response of the system is sensitive to delaminations at the interior bondlines in a few narrow frequency bands. These predictions are verified by measurements on a fabricated system. Successful imaging of internal delaminations is sensitive to proper selection of the interrogating frequency. Images of fabricated bondline delaminations are presented based on these studies

The problems of offenders with mental disorders: A plurality of perspectives within a single mental health care organisation

Managers, doctors, nurses, occupational therapists, social workers, psychologists, unqualified staff and service users were interviewed for a qualitative study of risk management and rehabilitation in an inner city medium secure forensic mental health care unit. Different professional orientations to service user problems were identified. Doctors focused primarily on the diagnosis of mental disorder, which they managed mainly through pharmaceutical interventions. Psychologists were principally concerned with personal factors, for example service user insight into their biographical history. Occupational therapists concentrated mainly on daily living skills, and social workers on post-discharge living arrangements. Some front line nurses, held accountable for security lapses, adopted a criminogenic approach. Service users were more likely than professionals to understand their needs in terms of their wider life circumstances. These differences are explored qualitatively in relation to four models of crossdisciplinary relationships: monoprofessional self-organisation combined with restricted communication; hermeneutic reaching out to other perspectives; the establishment of interdisciplinary sub-systems; and transdisciplinary merger. Relationships between professions working in this unit, as portrayed in qualitative interviews, corresponded mainly to the first model of monoprofessional self-organisation. Reasons for restricted crossdisciplinary understanding, particularly the wide power/status differences between the medical and other professions, and between staff and patients, are discussed

A systematic review of the scientifically demonstrated effects of densification

One of the current dominant strategies proposed for sustainable urban development is densification. UN Habitat prescribes a density of over 150 inhabitants per hectare to realize the UN Sustainable Development Goals. While some authors advocate the very reasonable benefits of density, others emphasize the potential drawbacks. The main goal of this paper is to provide a systematic review of international research on urban density and its potential benefits and drawbacks for sustainable urban development. 1208 articles were selected from Web of Science and after the screening of abstracts, 330 papers were found eligible to be included in the quantitative synthesis. Results show that the effects of densification that dominate literature are transport related studies (41%), followed by studies focusing on economics (14%), social effects (12%) and human health (11%). Least studied effects are resource efficiency (1%), service (3%) and urban environment (4%). Positive correlations with higher density are reported for transport and economics, while ecology, social impact and health show mainly negative correlations with higher density. The findings reported are generic as similar trends are found in North America, Asia and Europe and only minor differences in outcome are found in studies using different measures of density, unit or scale of analysis