Reflection groups and polytopes over finite fields, II

When the standard representation of a crystallographic Coxeter group $\Gamma$ is reduced modulo an odd prime $p$, a finite representation in some orthogonal space over $\mathbb{Z}_p$ is obtained. If $\Gamma$ has a string diagram, the latter group will often be the automorphism group of a finite regular polytope. In Part I we described the basics of this construction and enumerated the polytopes associated with the groups of rank 3 and the groups of spherical or Euclidean type. In this paper, we investigate such families of polytopes for more general choices of $\Gamma$, including all groups of rank 4. In particular, we study in depth the interplay between their geometric properties and the algebraic structure of the corresponding finite orthogonal group.Comment: 30 pages (Advances in Applied Mathematics, to appear

Watering the garden of family wellbeing

This report contains the recommendations and outcomes of the national roundtable Empowering Aboriginal and Torres Strait Islander people through the Family Wellbeing program, Adelaide, March 2014. There is an accompanying policy brief. Family Wellbeing (FWB) is an effective social and emotional wellbeing program originally developed and delivered by and for Aboriginal and Torres Strait Islander people. The central objective of FWB is to develop people’s skills and capacity to move from a position of disempowerment to empowerment; to empower people with a way to control and change their lives. In March 2014, the Lowitja Institute convened a national roundtable in Adelaide to consider the impact of FWB and opportunities for future development. Roundtable participants from across community, training and delivery, research and policy sectors, shared their experiences of FWB and focused on finding strategies to support the delivery, research and uptake of the FWB program. Roundtable discussions underlined how the program’s empowerment model builds the evidence base that social and emotional wellbeing programs effectively improve people’s lives and provide a promising and practical way to help bridge the gap between Australia’s First Peoples and the non-Indigenous population

Dynamic Factor Demands for Aggregate Southeastern United States Agriculture

A four equation input demand system for aggregate Southeastern United States agriculture consistent with dynamic optimizing behavior is specified and estimated. Labor and materials are considered as variable inputs while land and capital are treated as quasi-fixed inputs. It is found that the adjustment rates for capital and land differ considerably and are interdependent. Further, the data appear consistent with the existence of an aggregate production technology and the hypothesized optimizing behavior.Farm Management,

Energy Minimization of Discrete Protein Titration State Models Using Graph Theory

There are several applications in computational biophysics which require the optimization of discrete interacting states; e.g., amino acid titration states, ligand oxidation states, or discrete rotamer angles. Such optimization can be very time-consuming as it scales exponentially in the number of sites to be optimized. In this paper, we describe a new polynomial-time algorithm for optimization of discrete states in macromolecular systems. This algorithm was adapted from image processing and uses techniques from discrete mathematics and graph theory to restate the optimization problem in terms of "maximum flow-minimum cut" graph analysis. The interaction energy graph, a graph in which vertices (amino acids) and edges (interactions) are weighted with their respective energies, is transformed into a flow network in which the value of the minimum cut in the network equals the minimum free energy of the protein, and the cut itself encodes the state that achieves the minimum free energy. Because of its deterministic nature and polynomial-time performance, this algorithm has the potential to allow for the ionization state of larger proteins to be discovered

Collective mobilization and the struggle for squatter citizenship: rereading “xenophobic” violence in a South African settlement

Given the association between informal residence and the occurrence of “xenophobic” violence in South Africa, this article examines “xenophobic violence” through a political account of two squatter settlements across the transition to democracy: Jeffsville and Brazzaville on the informal periphery of Atteridgeville, Gauteng. Using the concepts of political identity, living politics and insurgent citizenship, the paper mines past and present to explore identities, collective practices and expertise whose legacy can be traced in contemporary mobilization against foreigners, particularly at times of popular protest. I suggest that the category of the “surplus person”, which originated in the apartheid era, lives on in the unfinished transition of squatter citizens to formal urban inclusion in contemporary South Africa. The political salience of this legacy of superfluity is magnified at times of protest, not only through the claims made on the state, but also through the techniques for protest mobilization, which both activate and manufacture identities based on common suffering and civic labour. In the informal settlements of Jeffsville and Brazzaville, these identities polarised insurgent citizens from non-citizen newcomers, particularly those traders whose business-as-usual practices during times of protest appeared as evidence of their indifference and lack of reciprocity precisely at times when shared suffering and commitment were produced as defining qualities of the squatter community

A Candidate Transit Event around Proxima Centauri

We present a single candidate transit event around Proxima Centauri, found during a blind transit search using a robotic 30\,cm telescope at Las Campanas Observatory. The event lasted 1 hour, with an estimated depth of 5\,mmag, and is inconsistent with the transit window predicted for the recently discovered planet b. We modeled the lightcurve under the assumption that the event was caused by a transiting exoplanet, and our model predicts the planet has a radius $R \sim 1 R_{\oplus}$. We encourage continued monitoring of Proxima to elucidate the origin of this event.Comment: 3 pages, 1 figure. Accepted for publication in Research Notes of the AA

Freezing line of the Lennard-Jones fluid: a Phase Switch Monte Carlo study

We report a Phase Switch Monte Carlo (PSMC) method study of the freezing line of the Lennard-Jones (LJ) fluid. Our work generalizes to soft potentials the original application of the method to hard sphere freezing, and builds on a previous PSMC study of the LJ system by Errington (J. Chem. Phys. {\bf 120}, 3130 (2004)). The latter work is extended by tracing a large section of the Lennard-Jones freezing curve, the results for which we compare to a previous Gibbs-Duhem integration study. Additionally we provide new background regarding the statistical mechanical basis of the PSMC method and extensive implementation details.Comment: 18 pages, 6 figure