Small scale energy release driven by supergranular flows on the quiet Sun

In this article we present data and modelling for the quiet Sun that strongly suggest a ubiquitous small-scale atmospheric heating mechanism that is driven solely by converging supergranular flows. A possible energy source for such events is the power transfer to the plasma via the work done on the magnetic field by photospheric convective flows, which exert drag of the footpoints of magnetic structures. In this paper we present evidence of small scale energy release events driven directly by the hydrodynamic forces that act on the magnetic elements in the photosphere, as a result of supergranular scale flows. We show strong spatial and temporal correlation between quiet Sun soft X-ray emission (from <i>Yohkoh</i> and <i>SOHO</i> MDI-derived flux removal events driven by deduced photospheric flows. We also present a simple model of heating generated by flux submergence, based on particle acceleration by converging magnetic mirrors. In the near future, high resolution soft X-ray images from XRT on the <i>Hinode</i> satellite will allow definitive, quantitative verification of our results

Dilemmas in doing insider research in professional education

This article explores the dilemmas I encountered when researching social work education in England as an insider researcher who was simultaneously employed as an educator in the host institution. This was an ethnographic project deploying multiple methods and generating rich case study material which informed the student textbook Becoming a Social Worker the four-year period of the project. First, ethical dilemmas emerged around informed consent and confidentiality when conducting surveys of students and reading their portfolios. Second, professional dilemmas stemmed from the ways in which my roles as a researcher, academic tutor, social worker and former practice educator converged and collided. Third, political dilemmas pertained to the potential for the project to crystallize and convey conflicts among stakeholders in the university and community. Since the majority of research in social work education is conducted by insiders, we have a vital interest in making sense of such complexity

Dynamic critical behavior of the Chayes-Machta-Swendsen-Wang algorithm

We study the dynamic critical behavior of the Chayes-Machta dynamics for the Fortuin-Kasteleyn random-cluster model, which generalizes the Swendsen-Wang dynamics for the q-state Potts model to noninteger q, in two and three spatial dimensions, by Monte Carlo simulation. We show that the Li-Sokal bound z \ge \alpha/\nu is close to but probably not sharp in d=2, and is far from sharp in d=3, for all q. The conjecture z \ge \beta/\nu is false (for some values of q) in both d=2 and d=3.Comment: Revtex4, 4 pages including 4 figure

Long‐term trends in fruit production in a tropical forest at Ngogo, Kibale National Park, Uganda

Fruit production in tropical forests varies considerably in space and time, with important implications for frugivorous consumers. Characterizing temporal variation in forest productivity is thus critical for understanding adaptations of tropical forest frugivores, yet long‐term phenology data from the tropics, in particular from African forests, are still scarce. Similarly, as the abiotic factors driving phenology in the tropics are predicted to change with a warming climate, studies documenting the relationship between climatic variables and fruit production are increasingly important. Here, we present data from 19 years of monitoring the phenology of 20 tree species at Ngogo in Kibale National Park, Uganda. Our aims were to characterize short‐ and long‐term trends in productivity and to understand the abiotic factors driving temporal variability in fruit production. Short‐term (month‐to‐month) variability in fruiting was relatively low at Ngogo, and overall fruit production increased significantly through the first half of the study. Among the abiotic variables, we expected to influence phenology patterns (including rainfall, solar irradiance, and average temperature), only average temperature was a significant predictor of monthly fruit production. We discuss these findings as they relate to the resource base of the frugivorous vertebrate community inhabiting Ngogo.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155479/1/btp12764.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155479/2/btp12764_am.pd

Monte Carlo Study of an Extended 3-State Potts Model on the Triangular Lattice

By introducing a chiral term into the Hamiltonian of the 3-state Potts model on a triangular lattice additional symmetries are achieved between the clockwise and anticlockwise states and the ferromagnetic state. This model is investigated using Monte Carlo methods. We investigate the full phase diagram and find evidence for a line tricritical points separating the ferromagnetic and antiferromagnetic phases.Comment: 6 pages, 10 figure

Three-dimensional antiferromagnetic q-state Potts models: application of the Wang-Landau algorithm

We apply a newly proposed Monte Carlo method, the Wang-Landau algorithm, to the study of the three-dimensional antiferromagnetic q-state Potts models on a simple cubic lattice. We systematically study the phase transition of the models with q=3, 4, 5 and 6. We obtain the finite-temperature phase transition for q= 3 and 4, whereas the transition temperature is down to zero for q=5. For q=6 there exists no order for all the temperatures. We also study the ground-state properties. The size-dependence of the ground-state entropy is investigated. We find that the ground-state entropy is larger than the contribution from the typical configurations of the broken-sublattice-symmetry state for q=3. The same situations are found for q = 4, 5 and 6.Comment: 9 pages including 9 eps figures, RevTeX, to appear in J. Phys.

Study of the Potts Model on the Honeycomb and Triangular Lattices: Low-Temperature Series and Partition Function Zeros

We present and analyze low-temperature series and complex-temperature partition function zeros for the $q$-state Potts model with $q=4$ on the honeycomb lattice and $q=3,4$ on the triangular lattice. A discussion is given as to how the locations of the singularities obtained from the series analysis correlate with the complex-temperature phase boundary. Extending our earlier work, we include a similar discussion for the Potts model with $q=3$ on the honeycomb lattice and with $q=3,4$ on the kagom\'e lattice.Comment: 33 pages, Latex, 9 encapsulated postscript figures, J. Phys. A, in pres

Large-qq expansion of the specific heat for the two-dimensional qq-state Potts model

We have calculated the large-$q$ expansion for the specific heat at the phase transition point in the two-dimensional $q$-state Potts model to the 23rd order in $1/\sqrt{q}$ using the finite lattice method. The obtained series allows us to give highly convergent estimates of the specific heat for $q>4$ on the first order transition point. The result confirm us the correctness of the conjecture by Bhattacharya et al. on the asymptotic behavior of the specific heat for $q \to 4_+$.Comment: 7 pages, LaTeX, 2 postscript figure

Does the process map influence the outcome of quality improvement work? A comparison of a sequential flow diagram and a hierarchical task analysis diagram

Background: Many quality and safety improvement methods in healthcare rely on a complete and accurate map of the process. Process mapping in healthcare is often achieved using a sequential flow diagram, but there is little guidance available in the literature about the most effective type of process map to use. Moreover there is evidence that the organisation of information in an external representation affects reasoning and decision making. This exploratory study examined whether the type of process map - sequential or hierarchical - affects healthcare practitioners' judgments.Methods: A sequential and a hierarchical process map of a community-based anti coagulation clinic were produced based on data obtained from interviews, talk-throughs, attendance at a training session and examination of protocols and policies. Clinic practitioners were asked to specify the parts of the process that they judged to contain quality and safety concerns. The process maps were then shown to them in counter-balanced order and they were asked to circle on the diagrams the parts of the process where they had the greatest quality and safety concerns. A structured interview was then conducted, in which they were asked about various aspects of the diagrams.Results: Quality and safety concerns cited by practitioners differed depending on whether they were or were not looking at a process map, and whether they were looking at a sequential diagram or a hierarchical diagram. More concerns were identified using the hierarchical diagram compared with the sequential diagram and more concerns were identified in relation to clinical work than administrative work. Participants' preference for the sequential or hierarchical diagram depended on the context in which they would be using it. The difficulties of determining the boundaries for the analysis and the granularity required were highlighted.Conclusions: The results indicated that the layout of a process map does influence perceptions of quality and safety problems in a process. In quality improvement work it is important to carefully consider the type of process map to be used and to consider using more than one map to ensure that different aspects of the process are captured

Stability of trions in strongly spin-polarized two-dimensional electron gases

Low-temperature magneto-photoluminescence studies of negatively charged excitons (X- trions) are reported for n-type modulation-doped ZnSe/Zn(Cd,Mn)Se quantum wells over a wide range of Fermi energy and spin-splitting. The magnetic composition is chosen such that these magnetic two-dimensional electron gases (2DEGs) are highly spin-polarized even at low magnetic fields, throughout the entire range of electron densities studied (5e10 to 6.5e11 cm^-2). This spin polarization has a pronounced effect on the formation and energy of X-, with the striking result that the trion ionization energy (the energy separating X- from the neutral exciton) follows the temperature- and magnetic field-tunable Fermi energy. The large Zeeman energy destabilizes X- at the nu=1 quantum limit, beyond which a new PL peak appears and persists to 60 Tesla, suggesting the formation of spin-triplet charged excitons.Comment: 5 pages (RevTex), 4 embedded EPS figs. Submitted to PRB-R