Anomalous Excitation Spectra of Frustrated Quantum Antiferromagnets

We use series expansions to study the excitation spectra of spin-1/2 antiferromagnets on anisotropic triangular lattices. For the isotropic triangular lattice model (TLM) the high-energy spectra show several anomalous features that differ strongly from linear spin-wave theory (LSWT). Even in the Neel phase, the deviations from LSWT increase sharply with frustration, leading to roton-like minima at special wavevectors. We argue that these results can be interpreted naturally in a spinon language, and provide an explanation for the previously observed anomalous finite-temperature properties of the TLM. In the coupled-chains limit, quantum renormalizations strongly enhance the one-dimensionality of the spectra, in agreement with experiments on Cs_2CuCl_4.Comment: 4 pages, 5 figures. New Fig. 3 with higher-order series data, paper shortened, references updated, one added (Ref. 28), minor changes otherwise. Published versio

Excitation spectra and ground state properties of the layered spin-1/2 frustrated antiferromagnets Cs_2CuCl_4 and Cs_2CuBr_4

We use series expansion methods to study ground- and excited-state properties in the helically ordered phase of spin-1/2 frustrated antiferromagnets on an anisotropic triangular lattice. We calculate the ground state energy, ordering wavevector, sublattice magnetization and one-magnon excitation spectrum for parameters relevant to Cs_2CuCl_4 and Cs_2CuBr_4. Both materials are modeled in terms of a Heisenberg model with spatially anisotropic exchange constants; for Cs_2CuCl_4 we also take into account the additional Dzyaloshinskii-Moriya (DM) interaction. We compare our results for Cs_2CuCl_4 with unpolarized neutron scattering experiments and find good agreement. In particular, the large quantum renormalizations of the one-magnon dispersion are well accounted for in our analysis, and inclusion of the DM interaction brings the theoretical predictions for the ordering wavevector and the magnon dispersion closer to the experimental results.Comment: 10 pages, 8 figure

The success, satisfaction and experiences of international students in an immersive block model

Despite growing interest in immersive block models in higher education, very little is known about the experiences of international students in these non-traditional forms of learning. To enable an initial view of how international students perceive and perform in an immersive block model, we used an exploratory mixed methods approach to examine the academic success, satisfaction, and experiences of international students in a 6-week immersive block model at a regional public Australian university. Inferential statistical tests were used to explore the success rates and unit and teaching satisfaction of onshore and offshore international students in the immersive block model and in the traditional trimester model. Overall, the immersive block model made a significant positive difference to the academic success of international students, both onshore and offshore. However, a decline in satisfaction was observed among science and engineering students, contrasting with an increase in satisfaction among business and arts students. Data collected through semi-guided interviews with 10 students from this latter group indicate several key benefits and challenges associated with immersive block learning. Students reported heightened focus and motivation, supportive teaching, and a healthy study-work-life balance. Challenges included not knowing what to expect, forming social connections with classmates, and the fast turnover between assessments. These findings indicate that it is important for institutions to prepare international students well for the pace and time management demands of studying in an immersive block model and to encourage the formation of social connections. Assessment timing, volume, and scaffolding should also be key considerations in immersive block model curriculum design

Surfboard Paddling Technique and Neuromechanical Control: A Narrative Review

Surfboard paddling is an essential activity when surfing. Research investigating surfboard paddling, especially as it pertains to neuromechanical control and techniques used, is limited. Previous research made use of swim ergometers to examine surfboard paddling demands. The validity of using swim ergometers in surfboard paddling research and training deserves further analysis. To establish ecologically valid findings, researchers have begun to use swim flumes and still-water paddling environments to investigate paddling efficiency and technique. This emerging body of research has reported that muscle activation patterns, intensities, and timings differ as surfers move through different paddle stroke phases. A deeper understanding of paddling\u27s neuromechanical control may help enhance the understanding of how to improve paddle performance and perhaps reduce injury risk. Therefore, the purpose of this review was to identify the gaps in the existing literature to help identify future research directions in relation to surfboard paddling techniques and neuromechanical control

Cross sectional analysis of depression amongst Australian rural business owners following cyclone-related flooding

Background: Flooding is an increasingly prevalent natural hazard worldwide and can have a profound impact on the mental health of those directly and indirectly affected. Little is known about the impact on business owners, who may be particularly vulnerable to the mental health complications of flooding given the additional economic stressors. Methods: A large cross-sectional survey was conducted six months after severe flooding in the rural Northern Rivers region of New South Wales, Australia in 2017. The survey assessed demographics, probable depression (using the Patient Health Questionnaire-2), flood exposure, flood-related financial factors, prior flood exposure and support from various organisations. Logistic regression was used to identify predictors of probable depression in 653 of the 745 participants who identified as business owners. Results: The prevalence of probable depression in our sample was 17.0%. A quarter (25.1%) of business owners whose business was flooded suffered from probable depression, compared to 12.4% of non-flooded business owners. The multivariable model for probable depression demonstrated elevated adjusted odds ratios (AOR) for business owners who had to evacuate their business (AOR = 2.11, 95% Confidence Interval (CI) 1.25–3.57) compared to those who did not evacuate. Insurance disputes/rejections were a strong predictor for probable depression (AOR = 3.76, CI 1.86–7.60). Those whose income was reduced due to the flood and had not returned to normal six months post-flood demonstrated an increased AOR for probable depression (AOR 2.53, CI 1.26–5.07) compared to those whose income had returned to normal. The univariable analysis found elevated crude odds ratios (OR) for the cumulative effect of multiple flood exposures and unmet support needs by the state government (OR = 2.74, CI 1.12–6.68). The majority of business owners felt their needs were not met by most organisations providing flood-related support. Conclusion: The impact of flood exposure and flood-related financial factors on probable depression was highly significant for the business owner population. Furthermore, business owners felt under-supported by flood-related services. These findings highlight the vulnerability of exposed business owners and the need for increased support. Disaster planning programs in conjunction with system level changes such as infrastructure and education are vital for disaster preparedness

The Ammount of Interstellar Carbon Locked in Solid Hydrogenated Amorphous Carbon

We review the literature and present new experimental data to determine the amount of carbon likely to be locked in form of solid hydrogenated amorphous carbon (HAC) grains. We conclude on the basis of a thorough analysis of the intrinsic strength of the C-H stretching band at 3.4 micron that between 10 and 80 ppM H of carbon is in the form of HAC grains. We show that it is necessary to know the level of hydrogenation (H/C) of the interstellar HAC to determine more precisely the amount of carbon it ties up. We present optical constants, photoluminescence spectroscopy, and IR absorption spectroscopy for a particular HAC sample that is shown to have a 3.4 micron absorption feature that is quantatively consistent with that observed in the diffuse interstellar medium.Comment: This paper is 14 pages long with 5 figures and will appear in the 1 December 1999 issue of Ap

Universal subgap optical conductivity in quasi-one-dimensional Peierls systems

Quasi-one-dimensional Peierls systems with quantum and thermal lattice fluctuations can be modeled by a Dirac-type equation with a Gaussian-correlated off-diagonal disorder. A powerful new method gives the exact disorder-averaged Green function used to compute the optical conductivity. The strong subgap tail of the conductivity has a universal scaling form. The frequency and temperature dependence of the calculated spectrum agrees with experiments on KCP(Br) and trans-polyacetylene.Comment: 11 pages (+ 3 figures), LATEX (REVTEX 3.0

Religion as practices of attachment and materiality: the making of Buddhism in contemporary London

This article aims to explore Buddhism’s often-overlooked presence on London’s urban landscape, showing how its quietness and subtlety of approach has allowed the faith to grow largely beneath the radar. It argues that Buddhism makes claims to urban space in much the same way as it produces its faith, being as much about the practices performed and the spaces where they are enacted as it is about faith or beliefs. The research across a number of Buddhist sites in London reveals that number of people declaring themselves as Buddhists has indeed risen in recent years, following the rise of other non-traditional religions in the UK; however, this research suggests that Buddhism differs from these in several ways. Drawing on Baumann’s (2002) distinction between traditionalist and modernist approaches to Buddhism, our research reveals a growth in each of these. Nevertheless, Buddhism remains largely invisible in the urban and suburban landscape of London, adapting buildings that are already in place, with little material impact on the built environment, and has thus been less subject to contestation than other religious movements and traditions. This research contributes to a growing literature which foregrounds the importance of religion in making contemporary urban and social worlds

Measurement in Economics and Social Science

The paper discusses measurement, primarily in economics, from both analytical and historical perspectives. The historical section traces the commitment to ordinalism on the part of economic theorists from the doctrinal disputes between classical economics and marginalism, through the struggle of orthodox economics against socialism down to the cold-war alliance between mathematical social science and anti-communist ideology. In economics the commitment to ordinalism led to the separation of theory from the quantitative measures that are computed in practice: price and quantity indexes, consumer surplus and real national product. The commitment to ordinality entered political science, via Arrow’s ‘impossibility theorem’, effectively merging it with economics, and ensuring its sterility. How can a field that has as its central result the impossibility of democracy contribute to the design of democratic institutions? The analytical part of the paper deals with the quantitative measures mentioned above. I begin with the conceptual clarification that what these measures try to achieve is a restoration of the money metric that is lost when prices are variable. I conclude that there is only one measure that can be embedded in a satisfactory economic theory, free from unreasonable restrictions. It is the Törnqvist index as an approximation to its theoretical counterpart the Divisia index. The statistical agencies have at various times produced different measures for real national product and its components, as well as related concepts. I argue that all of these are flawed and that a single deflator should be used for the aggregate and the components. Ideally this should be a chained Törnqvist price index defined on aggregate consumption. The social sciences are split. The economic approach is abstract, focused on the assumption of rational and informed behavior, and tends to the political right. The sociological approach is empirical, stresses the non-rational aspects of human behavior and tends to the political left. I argue that the split is due to the fact that the empirical and theoretical traditions were never joined in the social sciences as they were in the natural sciences. I also argue that measurement can potentially help in healing this split