1,286 research outputs found
'But I thought we were friends?' Life cycles and research relationships
This chapter is concerned with a relatively under-explored aspect of ‘engaged research’ – the nature of friendship relations between researchers and practitioners, and the ethical dilemmas that arise in such relationships. Attention has been paid to the relational aspects of research in the methodology literature, but this chapter focuses more closely on friendship in particular. The chapter is framed around two guiding concerns: how do friendships, formed in and around research, change over time; and in view of friendship conceived in this dynamic fashion, what ethical questions and dilemmas arise for the ‘friends’
Photoionization of Co and electron-impact excitation of Co using the Dirac R-matrix method
Modelling of massive stars and supernovae (SNe) plays a crucial role in
understanding galaxies. From this modelling we can derive fundamental
constraints on stellar evolution, mass-loss processes, mixing, and the products
of nucleosynthesis. Proper account must be taken of all important processes
that populate and depopulate the levels (collisional excitation, de-excitation,
ionization, recombination, photoionization, bound-bound processes). For the
analysis of Type Ia SNe and core collapse SNe (Types Ib, Ic and II) Fe group
elements are particularly important. Unfortunately little data is currently
available and most noticeably absent are the photoionization cross-sections for
the Fe-peaks which have high abundances in SNe. Important interactions for both
photoionization and electron-impact excitation are calculated using the
relativistic Dirac Atomic -matrix Codes (DARC) for low ionization stages of
cobalt. All results are calculated up to photon energies of 45 eV and electron
energies up to 20 eV. The wavefunction representation of Co III has been
generated using GRASP0 by including the dominant 3d, 3d[4s, 4p],
3p3d and 3p3d configurations, resulting in 292 fine structure
levels. Electron-impact collision strengths and Maxwellian averaged effective
collision strengths across a wide range of astrophysically relevant
temperatures are computed for Co III. In addition, statistically weighted
level-resolved ground and metastable photoionization cross-sections are
presented for Co II and compared directly with existing work.Comment: 11 pages, 8 figures and 4 table
Is There Enhanced Depletion of Gas-Phase Nitrogen in Moderately Reddened Lines of Sight?
We report on the abundance of interstellar neutral nitrogen (NI) for 30
sightlines, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE)
and the Hubble Space Telescope (HST). NI column densities are derived by
measuring the equivalent widths of several ultraviolet absorption lines and
subsequently fitting those to a curve of growth. We find a mean interstellar
N/H of 51+/-4 ppm. This is below the mean found by Meyer et al. of 62(+4,-3)
ppm (adjusted for a difference in f-values). Our mean N/H is similar, however,
to the (f-value adjusted) mean of 51+/-3 ppm found by Knauth et al. for a
larger sample of sightlines with larger hydrogen column densities comparable to
those in this study. We discuss the question of whether or not nitrogen shows
increased gas-phase depletion in lines of sight with column densities
log(H_tot) >~ 21, as claimed by Knauth et al. The nitrogen abundance in the
line of sight toward HD 152236 is particularly interesting. We derive very
small N/H and N/O ratios for this line of sight that may support a previous
suggestion that members of the Sco OB1 association formed from an N-deficient
region.Comment: Accepted in The Astrophysical Journal, 9/2006 (expected pub. date:
1/2007) 38 pages, 5 figures (4 color
The FERRUM Project: experimental and theoretical transition rates of forbidden [Sc II] lines and radiative lifetimes of metastable Sc II levels
Context. In many plasmas, long-lived metastable atomic levels are depopulated
by collisions (quenched) before they decay radiatively. In low-density regions,
however, the low collision rate may allow depopulation by electric dipole (E1)
forbidden radiative transitions, so-called forbidden lines (mainly M1 and E2
transitions). If the atomic transition data are known, these lines are
indicators of physical plasma conditions and used for abundance determination.
Aims. Transition rates can be derived by combining relative intensities between
the decay channels, so-called branching fractions (BFs), and the radiative
lifetime of the common upper level. We use this approach for forbidden [Sc ii]
lines, along with new calculations. Methods. Neither BFs for forbidden lines,
nor lifetimes of metastable levels, are easily measured in a laboratory.
Therefore, astrophysical BFs measured in Space Telescope Imaging Spectrograph
(STIS) spectra of the strontium filament of Eta Carinae are combined with
lifetime measurements using a laser probing technique on a stored ion-beam
(CRYRING facility,MSL, Stockholm). These quantities are used to derive the
absolute transition rates (A-values). New theoretical transition rates and
lifetimes are calulated using the CIV3 code. Results. We report experimental
lifetimes of the Sc ii levels 3d2 a3P0,1,2 with lifetimes 1.28, 1.42, and 1.24
s, respectively, and transition rates for lines from these levels down to 3d4s
a3D in the region 8270-8390 A. These are the most important forbidden [Sc ii]
transitions. New calculations for lines and metastable lifetimes are also
presented, and are in good agreement with the experimental data.Comment: 5 pages. Accepted for A&
The structure of human CD23 and its interactions with IgE and CD21
The low-affinity immunoglobulin E (IgE) receptor, CD23 (FcɛRII), binds both IgE and CD21 and, through these interactions, regulates the synthesis of IgE, the antibody isotype that mediates the allergic response. We have determined the three-dimensional structure of the C-type lectin domain of CD23 in solution by nuclear magnetic resonance spectroscopy. An analysis of concentration-dependent chemical shift perturbations have allowed us to identify the residues engaged in self-association to the trimeric state, whereas ligand-induced changes have defined the binding sites for IgE and CD21. The results further reveal that CD23 can bind both ligands simultaneously. Despite the C-type lectin domain structure, none of the interactions require calcium. We also find that IgE and CD23 can interact to form high molecular mass multimeric complexes. The interactions that we have described provide a solution to the paradox that CD23 is involved in both up- and down-regulation of IgE and provide a structural basis for the development of inhibitors of allergic disease
Faculty development in teaching and learning : the UK framework and current debates
Following the publication of a recent report, commissioned by the Higher Education Academy (HEA) and conducted by Staff and Educational Developers Association, this short paper considers the HEA UK Professional Standards Framework in the UK Higher Education Sector, in the context of recent and continuing debates about how best to support faculty professional development in teaching (and supporting learning). The need for a framework is briefly articulated, followed by a description of its main elements and a summary of recent evidence on its impact. A discussion of issues and (international) debates about the role of formal qualifications in delivering the kind of faculty development envisaged in the framework and aligned programmes is then presented. The paper concludes with some suggestions for research that arise from this review.PostprintPeer reviewe
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