Surface activation of Concorde by Be-7

Activation analysis of two airframe components from the Concorde aircraft has identified the presence of Be-7, a nuclide found by other investigators that was deposited on the forward edge of the Long Duration Exposure Facility (LDEF) structure. The results of the Concorde analysis indicate that this phenomenon is very much a surface effect, and that the areal densities of the Be-7 are comparable to those found for LDEF. The collection of Be-7 by the aircraft must be greater than in the case of LDEF (since duration for which Concorde is accumulating the nuclide is shorter) and is of the order of 1.2 to 41 nuclei/sq cm(-)s(exp -1) depending upon assumptions made regarding the altitude at which collection becomes appreciable, and the efficiency of the process which removes the radionuclide

Enhancing Small Group Teaching in Plant Sciences: A Research and Development Project in Higher Education

The Department of Plant Sciences at the University of Cambridge uses a range of learning and teaching environments including lectures, practical laboratories and small group tutorials'. Under the auspices of the Cambridge-MIT Institute's Pedagogy Programme, a two-year research and development project concerned with the development of small-group teaching is being undertaken. The research element of this project endeavours to illuminate current practice and identify areas in which evidence-based development might take place. The development element will include professional development activities and the production of curriculum resources including appropriate online material. This is a multi-method study including a series of student questionnaires; focus groups of students; semi-structured interviews with staff members; and the collection of video of small group teaching. In this paper we report selected findings from the 'student data' of the first year of this project.The questionnaire, conducted with two cohorts of students (2nd and 3rd year Undergraduates), used a double-scale questionnaire in which students were asked to report both on the prevalence of a range of teaching and learning practices and on how valuable these were in supporting their learning. This type of questionnaire instrument is particularly appropriate because the data it generates is suggestive of areas for changes in practice. The gaps between 'practices' and 'values' (across both cohorts) suggested that students valued activities which improved their understanding of how elements of the course were interrelated; which related course content to 'authentic' examples; and those in which teachers made explicit the characteristics of 'high quality' student work. Small group teaching, in the view of most students, was best used to extend and explore concepts introduced in lectures rather than simply reinforcing them or assessing student understanding.Data gathered through focus group activities illuminated the questionnaire data, providing detailed accounts of how students managed their own learning, and the roles played in this by lectures, small group teaching and other resources. Students identified the processes of planning and writing essays as key learning activities during which they integrated diverse course content and reflected on problematic knowledge. Questionnaire and focus group data suggested that students had less clear views regarding the value of collaborative learning, peer-assessment or activities such as making presentations to other students. When students talked in positive terms about these activities, they often referred to the learning benefits of preparation for the tasks rather than of the collaborative activities themselves. These views may provide indications of potential barriers to changes in learning and teaching environments, and suggest that any such changes may have to be carefully justified to students in terms of benefits to their own learning. Many of our findings are broadly in accord with other work on teaching and learning in Higher Education settings (such as the 'Oxford Learning Context Project' and the 'Enhancing Teaching-Learning Environments in Undergraduate Courses' Project) in that 'deep learning' and 'authenticity' in learning activities are valued by students, and that the introduction of specific formative practices (such as sharing notions of 'quality') would be welcomed. At the same time, amongst the students in our sample, a view of learning as an individual process of 'learning-as-acquisition' predominates over a view that it is a social process of 'learning-as-participation', and this will inform the planning of the 'development' aspect of the project. We conclude with a discussion of how the approach we have used might be more widely applied both within and beyond the Cambridge-MIT partnership. We also identify potential affordances of, and barriers to, the development of research-informed teaching in Higher Education

Mentalising remotely: The AFNCCF’s adaptations to the coronavirus crisis

An overview of the work the approach taken by the Anna Freud National Centre for Children and Families in the rapid transition to remote working in response to the coronavirus lockdown. We outline some of the challenges of remote working and how we are seeking to mitigate them, informed by the over‐riding principle that individual relationships and the experiences of the child, young person and family must remain the central concern. The importance of maintaining a mentalising stance in remote working is discussed. We argue that a mentalising relationship which generates epistemic trust is possible in remote working, but this will require particular thought and effort on the part of the therapist. In particular, it is suggested that mentalising processes can be supported in remote working through, in the absence of the more implicit communications that are possible in face‐to‐face work, more explicit communications about mental states

Automation of a flow injection system for the determination of dissolved silver at picomolar concentrations in seawater with inductively coupled plasma mass spectrometry

An automated flow injection system for the determination of dissolved silver at ultratrace concentrations in seawater, and controlled under LabVIEW™, is described. The flow injection system allows online processing of seawater samples before their analysis using a magnetic sector inductively coupled plasma mass spectrometry (MS-ICP-MS) instrument. Samples were analysed with a minimum amount of manipulation, thereby reducing the risk of contamination. In addition, the flow injection approach with incorporation of an anion exchange minicolumn allowed ready removal of analytical interferences caused by the saline matrix. The software allowed full control of all flow injection components (valves and pumps) and removed manual time control and, therefore, operator errors. The optimized system was capable of five sample injections per h, including preconcentration and wash steps. The limit of detection was 0.5 pM for a 240-s sample load time, which allowed the determination of dissolved silver in open ocean waters, where picomolar concentration levels are typically encountered

Temperature dependence of density profiles for a cloud of non-interacting fermions moving inside a harmonic trap in one dimension

We extend to finite temperature a Green's function method that was previously proposed to evaluate ground-state properties of mesoscopic clouds of non-interacting fermions moving under harmonic confinement in one dimension. By calculations of the particle and kinetic energy density profiles we illustrate the role of thermal excitations in smoothing out the quantum shell structure of the cloud and in spreading the particle spill-out from quantum tunnel at the edges. We also discuss the approach of the exact density profiles to the predictions of a semiclassical model often used in the theory of confined atomic gases at finite temperature.Comment: 7 pages, 4 figure

Spectroscopic Temperature Determination of Degenerate Fermi Gases

We suggest a simple method for measuring the temperature of ultra-cold gases made of fermions. We show that by using a two-photon Raman probe, it is possible to obtain lineshapes which reveal properties of the degenerate sample, notably its temperature $T$. The proposed method could be used with identical fermions in different hyperfine states interacting via s-wave scattering or identical fermions in the same hyperfine state via p-wave scattering. We illustrate the applicability of the method in realistic conditions for $^6$Li prepared in two different hyperfine states. We find that temperatures down to 0.05 $T_{F}$ can be determined by this {\it in-situ} method.Comment: 7 pages, 4 figures, Revtex

Superfluidity in the interior-gap states

We investigate superfluidity in the interior-gap states proposed by Liu and Wilczek. At weak coupling, we find the {\em gapless} interior-gap state unstable in physically accessible regimes of the parameter space, where the superfluid density is shown to be always negative. We therefore conclude that the spatially-uniform interior-gap phase is extremely unstable unless it is fully gapped; in this case, however, the state is rather similar to conventional BCS states.Comment: To appear in Physical Review

Instability Heating of Sympathetically-Cooled Ions in a Linear Paul Trap

Sympathetic laser cooling of ions stored within a linear-geometry, radio frequency, electric-quadrupole trap has been investigated using computational and theoretical techniques. The simulation, which allows 5 sample ions to interact with 35 laser-cooled atomic ions, revealed an instability heating mechanism, which can prevent ions below a certain critical mass from being sympathetically cooled. This critical mass can however be varied by changing the trapping field parameters thus allowing ions with a very large range of masses to be sympathetically cooled using a single ion species. A theoretical explanation of this instability heating mechanism is presented which predicts that the cooling-heating boundary in trapping parameter space is a line of constant $q_u$ (ion trap stability coefficient), a result supported by the computational results. The threshold value of $q_u$ depends on the masses of the interacting ions. A functional form of this dependence is given