QED calculation of the nuclear magnetic shielding for hydrogen-like ions

We report an ab initio calculation of the shielding of the nuclear magnetic moment by the bound electron in hydrogen-like ions. This investigation takes into account several effects that have not been calculated before (electron self-energy, vacuum polarization, nuclear magnetization distribution), thus bringing the theory to the point where further progress is impeded by the uncertainty due to nuclear-structure effects. The QED corrections are calculated to all orders in the nuclear binding strength parameter and, independently, to the leading order in the expansion in this parameter. The results obtained lay the ground for the high-precision determination of nuclear magnetic dipole moments from measurements of the g-factor of hydrogen-like ions

QED theory of the nuclear magnetic shielding in hydrogen-like ions

The shielding of the nuclear magnetic moment by the bound electron in hydrogen-like ions is calculated ab initio with inclusion of relativistic, nuclear, and quantum electrodynamics (QED) effects. The QED correction is evaluated to all orders in the nuclear binding strength parameter and, independently, to the first order in the expansion in this parameter. The results obtained lay the basis for the high-precision determination of nuclear magnetic dipole moments from measurements of the g-factor of hydrogen-like ions.Comment: 4 pages, 2 tables, 2 figure

Electron-correlation effects in the gg-factor of light Li-like ions

We investigate electron-correlation effects in the $g$-factor of the ground state of Li-like ions. Our calculations are performed within the nonrelativistic quantum electrodynamics (NRQED) expansion up to two leading orders in the fine-structure constant $\alpha$, $\alpha^2$ and $\alpha^3$. The dependence of the NRQED results on the nuclear charge number $Z$ is studied and the individual $1/Z$-expansion contributions are identified. Combining the obtained data with the results of the all-order (in $Z\alpha$) calculations performed within the $1/Z$ expansion, we derive the unified theoretical predictions for the $g$-factor of light Li-like ions.Comment: 9 pages, 4 table

Learning to assess in higher education: exploring the interplay of ‘formal’ and ‘informal’ learning in the academic workplace.

While there has been considerable research into HE teachers’ development and their conceptions of teaching more generally (see, for instance, Trigwell et al., 1994, Trigwell et al., 1999, Kane et al., 2002, Eley, 2006), the way in which HE staff become assessors and learn about assessment has not been widely researched. Researchers such as Knight et al. (2006) have highlighted the importance of non-/informal learning in the academic workplace, and there is conflicting evidence for the impact of more formal academic development. Research on workplace learning stresses that formal and informal dimensions of learning are intertwined, but also that formal learning opportunities have a role to play in the development of expertise (Tynjälä, 2008). This paper explores the ways in which academics learn to assess in HE. It draws on empirical data from two research projects undertaken at one UK university. The ‘assessment cultures’ project explores interrelationships between socio-cultural context and academic assessment practices. 37 interviews were conducted; 24 initial and 13 follow-up interviews. In the initial interviews lecturers described how they assess in specific modules they teach. In the follow-up interviews themes such as disciplinary and occupational background and the ways lecturers learned to assess were explored. The ‘staff learning’ project examines learning about assessment through different types of academic development: a compulsory course on assessment for new academics, a module on assessment for learning for experienced staff and a university assessment for learning network providing support and activities to its members. 31 semi-structured interviews were conducted: 17 with network members, 8 with participants of the course for new academics and 6 with participants of the course on assessment for learning. Interviewees were asked about the benefits or otherwise of the type of academic development experienced, changes in their understanding of assessment and changes in their assessment practices. Taken together, the data generated by the two projects provide insight into the complex process whereby formal and informal interact. Using data from the two projects has enabled us to extend the scope of each individual project in order to address questions which could otherwise not have been answered. It has also provided an opportunity to examine the data through the lenses of different theoretical frameworks, thus heightening our awareness for the ‘the theoretical frames of reference and methodological approaches which shape (…) [our] knowledge claims’ (Shay, p.1). The collaboration has increased our awareness for our own approaches and backgrounds and has required us to engage with each others’ theoretical and professional perspectives: that of Foucauldian post-structuralism and a focus on the discursive construction of identity with that of academic development and a focus on scholarship of teaching and learning and evaluation of academic development initiatives. It has also meant drawing on each others’ respective research backgrounds in student and teacher learning in higher education research on the one hand and workplace learning research on the other. In the critical review of student learning research which Shay refers to in her ‘think piece’, Haggis (2009) explicitly highlights the potential of the workplace learning literatures and debates for ‘thinking differently’ about higher education research. By challenging ways of knowing through collaboration, the paper intends to make a contribution to the ‘region’ (Shay, p.2). Our focus in the analysis is on the interrelationships between theoretical concepts and assessment practices. In some interviews encounters with a concept such as ‘assessment for learning’ were described as a lens which sheds light onto existing assessment practices as well as a tool which enables the development of practice. This draws attention to the importance of the discursive resources that are available to academics for talking about their practice. In addition, certain ways of learning appear to be significant both in everyday workplace practice and in academic development activities, for instance learning from and through others. Interaction with other members of staff, particularly from other disciplines, enables staff to question the taken for granted and re-think their assessment practices. The data suggest that the simple distinction between formal and informal learning in the academic workplace may be too crude and that it may therefore be difficult to evaluate or ‘prove’ the impact of formal learning opportunities. However, the findings have implications for academic development since they draws attention to the potential of specific types of ideas and learning activities to transform understandings of assessment and assessment practices. The paper will discuss the main findings as well as the benefits and challenges of working with data across two research projects with different theoretical underpinnings

SapFix: Automated End-To-End Repair at Scale

We report our experience with SapFix: the first deployment of automated end-to-end fault fixing, from test case design through to deployed repairs in production code. We have used SapFix at Facebook to repair 6 production systems, each consisting of tens of millions of lines of code, and which are collectively used by hundreds of millions of people worldwide

A Review of Ten Years of the Symposium on Search-Based Software Engineering

The year 2018 marked the tenth anniversary of the Symposium on Search Based Software Engineering (SSBSE). In order to better understand the characteristics and evolution of papers published in SSBSE, this work reports results from a mapping study targeting the ten proceedings of SSBSE. Our goal is to identify and to analyze authorship collaborations, the impact and relevance of SSBSE in terms of citations, the software engineering areas commonly studied as well as the new problems recently solved, the computational intelligence techniques preferred by authors and the rigour of experiments conducted in the papers. Besides this analysis, we list some recommendations to new authors who envisage to publish their work in SSBSE. Despite of existing mapping studies on SBSE, our contribution in this work is to provide information to researchers and practitioners willing to enter the SBSE field, being a source of information to strengthen the symposium, guide new studies, and motivate new collaboration among research groups

Photon angular distribution and nuclear-state alignment in nuclear excitation by electron capture

The alignment of nuclear states resonantly formed in nuclear excitation by electron capture (NEEC) is studied by means of a density matrix technique. The vibrational excitations of the nucleus are described by a collective model and the electrons are treated in a relativistic framework. Formulas for the angular distribution of photons emitted in the nuclear relaxation are derived. We present numerical results for alignment parameters and photon angular distributions for a number of heavy elements in the case of E2 nuclear transitions. Our results are intended to help future experimental attempts to discern NEEC from radiative recombination, which is the dominant competing process

Inverse Classification for Comparison-based Interpretability in Machine Learning

In the context of post-hoc interpretability, this paper addresses the task of explaining the prediction of a classifier, considering the case where no information is available, neither on the classifier itself, nor on the processed data (neither the training nor the test data). It proposes an instance-based approach whose principle consists in determining the minimal changes needed to alter a prediction: given a data point whose classification must be explained, the proposed method consists in identifying a close neighbour classified differently, where the closeness definition integrates a sparsity constraint. This principle is implemented using observation generation in the Growing Spheres algorithm. Experimental results on two datasets illustrate the relevance of the proposed approach that can be used to gain knowledge about the classifier.Comment: preprin

Conditional citizens? welfare rights and responsibilities in the late 1990s

In Britain the relationship between welfare rights and responsibilities has undergone change. A new welfare 'consensus' that emphasizes a citizen ship centred on notions of duty rather than rights has been built. This has allowed the state to reduce its role as a provider of welfare and also defend a position in which the welfare rights of some citizens are increas ingly conditional on those individuals meeting compulsory responsibili ties or duties. This concentration on individual responsibility/duty has undermined the welfare rights of some of the poorest members of society. Three levels of debate are considered within the article: academic, pol itical and 'grassroots'. The latter is included in an attempt to allow some 'bottom up' views into what is largely a debate dominated by social sci entists and politicians