Trees, forests and jungles: a botanical garden for cluster expansions

Combinatoric formulas for cluster expansions have been improved many times over the years. Here we develop some new combinatoric proofs and extensions of the tree formulas of Brydges and Kennedy, and test them on a series of pedagogical examples.Comment: 37 pages, Ecole Polytechnique A-325.099

Magnetic and thermodynamic properties of Sr_{2}LaFe_{3}O_{9}

Using a Dirac-Heisenberg Hamiltonian with biquadratic exchange interactions, we study the effect of iron disproportionation on the magnetic ordering, and describe the first-order magnetic transition occurring in the perovskite Sr_{2}LaFe_{3}O_{9}. Upon fitting the experimental data, we give an estimate of the exchange integrals for the antiferromagntic and ferromagnetic interactions, in agreement with previous works on kindered compounds. Spin-wave theory yields a magnon spectrum with a gapless antiferromagnetic mode together with two gapped ferromagnetic ones.Comment: 8 pages of RevTex, 5 figures (available upon request), submitted to J. Mag. Mag. Ma

It’s in the Backbone: Dance from Africa through the Diaspora, An Interview with DeAma Battle

Classically trained in dance, DeAma Battle became interested in Africa-rooted dance in the 1960s. She started performing the traditional dances from Africa that spread, via the Atlantic slave trade, to the United States, the Caribbean, and South America. She not only has performed those steps and movements, Battle has studied them, with master dancers from West Africa, Brazil, Haiti, Jamaica, and Cuba. One of her teachers and mentors was Chuck Davis, a leading African American teacher of traditional African dance. Her research has probed deeper, into the field abroad, on dance-study tours to Haiti, Jamaica, Ghana, Senegal, Morocco, and other countries with an African cultural heritage. Battle regards modern dance pioneer Katherine Dunham, who studied the cultural traditions of Haiti, as a role model. A dancer, artistic director, and choreographer, Battle also considers herself to be a dance archivist. In 1975, Battle founded the Art of Black Dance and Music in Somerville, Massachusetts, to perform and teach Africa-derived dances. One of the company’s goals has been to unify people of African descent “through the study of African-rooted dance, music, and folklore” to illustrate “cultural similarities within the African Diaspora.” In this interview with Trotter Review editor Kenneth J. Cooper, Battle discusses specific dances that Africa-descended people partake in in the Americas that incorporate traditional movements still performed in West Africa. Within the Diaspora, she identifies similarities between the traditional capoeira of Brazil and the break dancing popular in America in the 1970s. The African way of moving is so embedded, Battle notes, that it shows up even in the way black people who live on different continents walk. The interview was conducted in late 2013 at the Boston Conservatory of Music, where Battle teaches

Epitaxial Growth of La1/3_{1/3}Sr2/3_{2/3}FeO3_3 thin films by laser ablation

We report on the synthesis of high quality La$_{1/3}$Sr$_{2/3}$FeO$_3$ (LSFO) thin films using the pulsed laser deposition technique on both SrTiO$_3$ (STO) and LaAlO$_3$ (LAO) substrates (100)-oriented. From X-Ray diffraction (XRD) studies, we find that the films have an out-of-plane lattice parameter around 0.3865nm, almost independent of the substrate (i.e. the nature of the strains). The transport properties reveal that, while LSFO films deposited on STO exhibit an anomaly in the resistivity vs temperature at 180K (corresponding to the charge-ordered transition and associated with a transition from a paramagnetic to an antiferromagnetic state), the films grown on LAO display a very small magnetoresistance behavior and present an hysteresis around 270K under the application of a 4T magnetic field. The changes in transport properties between both substrates are discussed and compared with the corresponding single crystals.Comment: 9 pages, 4 figure

An interactive, generative Punch and Judy show using institutions, ASP and emotional agents

Using Punch and Judy as a story domain, we describe an interactive puppet show, where the flow and content of the story can be influenced by the actions of the audience. As the puppet show is acted out, the audience reacts to events by cheering or booing the characters. This affects the agents’ emotional state, potentially causing them to change their actions, altering the course of the narrative. An institutional normative model is used to constrain the narrative so that it remains consistent with the Punch and Judy canon. Through this vignette of a socio-technical system (STS), comprising human and software actors, an institutional model – derived from narrative theory – and (simplistic) technological interaction artifacts, we begin to be able to explore some of the issues that can arise in STS through the prism of the World-Institution-Technology (WIT) model

Spatial and Temporal Stability of Airglow Measured in the Meinel Band Window at 1191.3 nm

We report on the temporal and spatial fluctuations in the atmospheric brightness in the narrow band between Meinel emission lines at 1191.3 nm using an R=320 near-infrared instrument. We present the instrument design and implementation, followed by a detailed analysis of data taken over the course of a night from Table Mountain Observatory. The absolute sky brightness at this wavelength is found to be 5330 +/- 30 nW m^-2 sr^-1, consistent with previous measurements of the inter-band airglow at these wavelengths. This amplitude is larger than simple models of the continuum component of the airglow emission at these wavelengths, confirming that an extra emissive or scattering component is required to explain the observations. We perform a detailed investigation of the noise properties of the data and find no evidence for a noise component associated with temporal instability in the inter-line continuum. This result demonstrates that in several hours of ~100s integrations the noise performance of the instrument does not appear to significantly degrade from expectations, giving a proof of concept that near-IR line intensity mapping may be feasible from ground-based sites.Comment: 15 figures, submitted to PAS

Patients presenting to an acute general hospital with acute mental health needs. A retrospective observational cohort study

Objectives To examine the numbers and patterns of patients presenting to an urban acute general hospital with acute mental health presentations and to further investigate any variation related to the COVID-19 pandemic. Design Retrospective observational cohort study. Setting An urban acute general hospital in London, UK, comprising of five sites and two emergency departments. The hospital provides tertiary level general acute care but is not an acute mental health services provider. There is an inpatient liaison psychiatry service. Participants 358 131 patients attended the emergency departments of our acute general hospital during the study period. Of these, 14 871 patients attended with an acute mental health presentation. A further 14 947 patients attending with a physical illness were also noted to have a concurrent recorded mental health diagnosis. Results Large numbers of patients present to our acute general hospital with mental health illness even though the organisation does not provide mental health services other than inpatient liaison psychiatry. There was some variation in the numbers and patterns of presentations related to the COVID-19 pandemic. Patient numbers reduced to a mean of 9.13 (SD 3.38) patients presenting per day during the first ‘lockdown’ compared with 10.75 (SD 1.96) patients per day in an earlier matched time period (t=3.80, p<0.01). Acute mental health presentations following the third lockdown increased to a mean of 13.84 a day. Conclusions Large numbers of patients present to our acute general hospital with mental health illness. This suggests a need for appropriate resource, staffing and training to address the needs of these patients in a non-mental health provider organisation and subsequent appropriate transfer for timely treatment. The COVID-19 pandemic and the resulting lockdowns have resulted in variation in the numbers and patterns of patients presenting with acute mental health illness but these presentations are not new. Considerable work is still needed to provide integrated care which addresses the physical and mental healthcare needs of patients presenting to acute and general hospitals

Irreducible Hamiltonian approach to the Freedman-Townsend model

The irreducible BRST symmetry for the Freedman-Townsend model is derived. The comparison with the standard reducible approach is also addressed.Comment: 18 pages, LaTeX 2.0

Lagrangian gauge structure functions for systems with first-class constraints

The structure functions of the Lagrangian gauge algebra are given explicitly in terms of the hamiltonian constraints and the first order Hamiltonian structure functions and their derivatives