Long-Term Testing and Properties of Acrylic for the Daya Bay Antineutrino Detectors

The Daya Bay reactor antineutrino experiment has recently measured the neutrino mixing parameter sin22{\theta}13 by observing electron antineutrino disappearance over kilometer-scale baselines using six antineutrino detectors at near and far distances from reactor cores at the Daya Bay nuclear power complex. Liquid scintillator contained in transparent target vessels is used to detect electron antineutrinos via the inverse beta-decay reaction. The Daya Bay experiment will operate for about five years yielding a precision measurement of sin22{\theta}13. We report on long-term studies of poly(methyl methacrylate) known as acrylic, which is the primary material used in the fabrication of the target vessels for the experiment's antineutrino detectors. In these studies, acrylic samples are subjected to gaseous and liquid environmental conditions similar to those experienced during construction, transport, and operation of the Daya Bay acrylic target vessels and detectors. Mechanical and optical stability of the acrylic as well as its interaction with detector liquids is reported.Comment: 17 pages, 13 figures Submitted to JINS

Professional Learning in healthcare settings in resource-limited environments: What are the tensions for professionals’ knowing and learning about antimicrobial resistance?

This article examines tensions that professionals in healthcare settings in low-to-middle income countries (LMICs) face in the evolving field around surveillance of antimicrobial resistance (AMR). Few public health problems are of greater global importance today than AMR, that poses a threat to our ability to treat infections. In this context, the microbiology laboratory occupies a prominent place and the knowledge field of microbiology is expanding. In this study, we interviewed twenty-three (n = 23) professionals with expertise on AMR and public health systems to synthesise knowledge on strengthening AMR surveillance in LMICs. By drawing on a practice approach [Schatzki, T. R. 2001. “Practice Ttheory.” In The Practice Turn in Contemporary Theory (1–14), edited by T. R. Schatzki, K. Knorr-Cetima, and E. von Savigny. New York: Routledge.] combined with socio-cultural and cultural-historical theories (CHAT) [Engeström, Y. 1987. Learning by Expanding: An Activity-Theoretical Approach to Developmental Research. Helsinki: Orienta-Konsultit] the analysis reveals seven tensions between elements of the systems and discusses how such tensions serve to frame implications for implementing a capacity strengthening programme. The analysis shows that the novelty of the AMR as well as being a multi-disease and multisectoral by nature challenges existing forms of professional practice in healthcare settings. It also suggests that AMR requires to be dealt with through inter-professional and inter-sectoral approaches, while maintaining a focus across the local, national, and global systems, which is essential for initiatives that are set to address challenges to global health

Framing Professional Learning Analytics as Reframing Oneself

Central to imagining the future of technology-enhanced professional learning is the question of how data are gathered, analyzed, and fed back to stakeholders. The field of learning analytics (LA) has emerged over the last decade at the intersection of data science, learning sciences, human-centered and instructional design, and organizational change, and so could in principle inform how data can be gathered and analyzed in ways that support professional learning. However, in contrast to formal education where most research in LA has been conducted, much work-integrated learning is experiential, social, situated, and practice-bound. Supporting such learning exposes a significant weakness in LA research, and to make sense of this gap, this article proposes an adaptation of the Knowledge-Agency Window framework. It draws attention to how different forms of professional learning locate on the dimensions of learner agency and knowledge creation. Specifically, we argue that the concept of “reframing oneself” holds particular relevance for informal, work-integrated learning. To illustrate how this insight translates into LA design for professionals, three examples are provided: first, analyzing personal and team skills profiles (skills analytics); second, making sense of challenging workplace experiences (reflective writing analytics); and third, reflecting on orientation to learning (dispositional analytics). We foreground professional agency as a key requirement for such techniques to be used effectively and ethically

Search for Sterile Neutrinos with a Radioactive Source at Daya Bay

The far site detector complex of the Daya Bay reactor experiment is proposed as a location to search for sterile neutrinos with > eV mass. Antineutrinos from a 500 kCi 144Ce-144Pr beta-decay source (DeltaQ=2.996 MeV) would be detected by four identical 20-ton antineutrino targets. The site layout allows flexible source placement; several specific source locations are discussed. In one year, the 3+1 sterile neutrino hypothesis can be tested at essentially the full suggested range of the parameters Delta m^2_{new} and sin^22theta_{new} (90% C.L.). The backgrounds from six nuclear reactors at >1.6 km distance are shown to be manageable. Advantages of performing the experiment at the Daya Bay far site are described

Gyrokinetic electron acceleration in the force-free corona with anomalous resistivity

We numerically explore electron acceleration and coronal heating by dissipative electric fields. Electrons are traced in linear force-free magnetic fields extrapolated from SOHO/MDI magnetograms, endowed with anomalous resistivity ($\eta$) in localized dissipation regions where the magnetic twist \nabla \times \bhat exceeds a given threshold. Associated with $\eta > 0$ is a parallel electric field ${\bf E} = \eta {\bf j}$ which can accelerate runaway electrons. In order to gain observational predictions we inject electrons inside the dissipation regions and follow them for several seconds in real time. Precipitating electrons which leave the simulation system at height $z$ = 0 are associated with hard X rays, and electrons which escape at height $z$ $\sim$ 3$\cdot 10^4$ km are associated with normal-drifting type IIIs at the local plasma frequency. A third, trapped, population is related to gyrosynchrotron emission. Time profiles and spectra of all three emissions are calculated, and their dependence on the geometric model parameters and on $\eta$ is explored. It is found that precipitation generally preceeds escape by fractions of a second, and that the electrons perform many visits to the dissipation regions before leaving the simulation system. The electrons impacting $z$ = 0 reach higher energies than the escaping ones, and non-Maxwellian tails are observed at energies above the largest potential drop across a single dissipation region. Impact maps at $z$ = 0 show a tendency of the electrons to arrive at the borders of sunspots of one polarity. Although the magnetograms used here belong to non-flaring times, so that the simulations refer to nanoflares and `quiescent' coronal heating, it is conjectured that the same process, on a larger scale, is responsible for solar flares