Nonlinear Dynamics of Aeolian Sand Ripples

We study the initial instability of flat sand surface and further nonlinear dynamics of wind ripples. The proposed continuous model of ripple formation allowed us to simulate the development of a typical asymmetric ripple shape and the evolution of sand ripple pattern. We suggest that this evolution occurs via ripple merger preceded by several soliton-like interaction of ripples.Comment: 6 pages, 3 figures, corrected 2 typo

Swimming Upstream: Identifying student anxieties and solutions

This study explores some of the sources of stress faced by students in higher education. Research identifies an association between stress levels and students’ academic performance. This study aims to determine the sources, level and impact of perceived stresses among students in terms of age, gender, ethnicity, years of study and degree major. Participatory action research was explored as a means of developing strategies and solutions for students experiencing stress-related problems. Eleven undergraduate students were recruited initially as co-researchers with four academic staff and one research assistant. One student continued throughout the cycle with two others having to withdraw because of academic work pressures. A collaborative process took place using narrative storytelling and discussions alongside extra-sessional research. A range of outcomes is anticipated related to the students’ experience and academic achievements. Academic staff responsiveness and concern for student wellbeing and successful achievement will contribute to increased student satisfaction. Identification and development of systematic and effective ways of managing anxieties and sharing this with other HEIs will contribute to student wellbeing. In terms of academic outputs, a paper based on the pilot will be developed and acknowledgement of co-authorship appropriately made. A wider research proposal - inclusive of other universities and programmes can be developed for the future

NGO Legitimacy: Four Models

The aim of this paper is to examine NGOs’ legitimacy in the context of global politics. In order to yield a better understanding of NGOs’ legitimacy at the international level it is important to examine how their legitimacy claims are evaluated. This paper proposes dividing the literature into four models based on the theoretical and analytical approaches to their legitimacy claims: the market model, social change model, new institutionalism model and the critical model. The legitimacy criteria generated by the models are significantly different in their analytical scope of how one is to assess the role of NGOs operating as political actors contributing to democracy. The paper argues that the models present incomplete, and sometimes conflicting, views of NGOs’ legitimacy and that this poses a legitimacy dilemma for those assessing the political agency of NGOs in world politics. The paper concludes that only by approaching their legitimacy holistically can the democratic role of NGOs be explored and analysed in the context of world politics

Diquat Derivatives: Highly Active, Two-Dimensional Nonlinear Optical Chromophores with Potential Redox Switchability

In this article, we present a detailed study of structure−activity relationships in diquaternized 2,2′-bipyridyl (diquat) derivatives. Sixteen new chromophores have been synthesized, with variations in the amino electron donor substituents, π-conjugated bridge, and alkyl diquaternizing unit. Our aim is to combine very large, two-dimensional (2D) quadratic nonlinear optical (NLO) responses with reversible redox chemistry. The chromophores have been characterized as their PF_6^− salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Their visible absorption spectra are dominated by intense π → π^* intramolecular charge-transfer (ICT) bands, and all show two reversible diquat-based reductions. First hyperpolarizabilities β have been measured by using hyper-Rayleigh scattering with an 800 nm laser, and Stark spectroscopy of the ICT bands affords estimated static first hyperpolarizabilities β_0. The directly and indirectly derived β values are large and increase with the extent of π-conjugation and electron donor strength. Extending the quaternizing alkyl linkage always increases the ICT energy and decreases the E_(1/2) values for diquat reduction, but a compensating increase in the ICT intensity prevents significant decreases in Stark-based β_0 responses. Nine single-crystal X-ray structures have also been obtained. Time-dependent density functional theory clarifies the molecular electronic/optical properties, and finite field calculations agree with polarized HRS data in that the NLO responses of the disubstituted species are dominated by ‘off-diagonal’ β_(zyy) components. The most significant findings of these studies are: (i) β_0 values as much as 6 times that of the chromophore in the technologically important material (E)-4′-(dimethylamino)-N-methyl-4-stilbazolium tosylate; (ii) reversible electrochemistry that offers potential for redox-switching of optical properties over multiple states; (iii) strongly 2D NLO responses that may be exploited for novel practical applications; (iv) a new polar material, suitable for bulk NLO behavior

A Continuum Saltation Model for Sand Dunes

We derive a phenomenological continuum saltation model for aeolian sand transport that can serve as an efficient tool for geomorphological applications. The coupled differential equations for the average density and velocity of sand in the saltation layer reproduce both known equilibrium relations for the sand flux and the time evolution of the sand flux as predicted by microscopic saltation models. The three phenomenological parameters of the model are a reference height for the grain-air interaction, an effective restitution coefficient for the grain-bed interaction, and a multiplication factor characterizing the chain reaction caused by the impacts leading to a typical time or length scale of the saturation transients. We determine the values of these parameters by comparing our model with wind tunnel measurements. Our main interest are out of equilibrium situations where saturation transients are important, for instance at phase boundaries (ground/sand) or under unsteady wind conditions. We point out that saturation transients are indispensable for a proper description of sand flux over structured terrain, by applying the model to the windward side of an isolated dune, thereby resolving recently reported discrepancies between field measurements and theoretical predictions.Comment: 11 pages, 7 figure

Corridors of barchan dunes: stability and size selection

Barchans are crescentic dunes propagating on a solid ground. They form dune fields in the shape of elongated corridors in which the size and spacing between dunes are rather well selected. We show that even very realistic models for solitary dunes do not reproduce these corridors. Instead, two instabilities take place. First, barchans receive a sand flux at their back proportional to their width while the sand escapes only from their horns. Large dunes proportionally capture more than they loose sand, while the situation is reversed for small ones: therefore, solitary dunes cannot remain in a steady state. Second, the propagation speed of dunes decreases with the size of the dune: this leads -- through the collision process -- to a coarsening of barchan fields. We show that these phenomena are not specific to the model, but result from general and robust mechanisms. The length scales needed for these instabilities to develop are derived and discussed. They turn out to be much smaller than the dune field length. As a conclusion, there should exist further - yet unknown - mechanisms regulating and selecting the size of dunes.Comment: 13 pages, 13 figures. New version resubmitted to Phys. Rev. E. Pictures of better quality available on reques

Unfinished Business: Water, Sanitation and Hygiene in Remote Indigenous Communities in Australia's Northern Territory

Improving water, sanitation and hygiene (WASH) outcomes for the ~60,000 Indigenous people living in remote communities in Australia's Northern Territory (NT) remains an important but unresolved policy challenge. Despite major national reforms aimed at bolstering Australia's water security over the last decade, the WASH situation in remote Indigenous communities (RICs) has attracted little attention. This study sheds new light on this issue by assessing the status of WASH indicators (access, behaviours, health outcomes) and identifying obstacles that constrain progress. Up-to-date information on access to WASH services in RICs in NT is scant. We piece together historical data to deduce that there is now almost universal access to improved water sources and sanitation facilities. At least 90% of dwellings currently have a piped water supply and a private sanitation facility. In the 72 largest communities, the quantity of water used by households is far greater than the Australian average, and regular testing reveals the water supplied is of good microbiological quality. The main infrastructure shortfalls - in terms of access, reliability and safety - can be found in the more than 400 small homeland communities, most of which have a population of less than 50. Notwithstanding nearly universal access to services, the burden of WASH-related diseases remains substantial. Indigenous children in remote communities are twice as likely to be hospitalised for intestinal infection as non-Indigenous children. Environmental enteropathy and prevalence of intestinal parasitic infestation (e.g. Strongyloides) provide further markers of excreta-related disease transmission. Trachoma remains endemic in many RICs despite repeated mass drug administrations. Skin infections are also prevalent, and these are thought to underlie disproportionately high rates of acute glomerulonephritis and acute rheumatic fever, both of which lead to chronic and life-threatening kidney and heart diseases. The WASH landscape in RICs therefore presents a paradox: widespread access to WASH infrastructure but a continued high burden of WASHrelated diseases. The underlying reasons for the situation are complex and inseparable from the entrenched socio-economic disadvantage that characterise many households in RICs. However, evidence points to several proximate causes that contribute to the high burden of WASH-related diseases: (i) problematic hygiene practices; (ii) non-functional health hardware within the home (taps, toilets); and (iii) high household occupancy rates. We conclude that past and current service delivery investments have helped to reduce WASH access disparities between Indigenous and non-Indigenous Australians, but they have failed to close the WASH-related disease gap. If future WASH investments in RICs are to yield optimal health dividends, the broader ecosystem must also be tackled, namely hygiene practices, maintenance of household-level hardware, and overcrowding

What explains the uneven take-up of ISO 14001 at the global level?: a panel-data analysis

Since its release in the mid-1990s, close to 37 000 facilities have been certified to ISO 14001, the international voluntary standard for environmental management systems. Yet, despite claims that the standard can be readily adapted to very different corporate and geographic settings, its take-up has been highly geographically variable. This paper contributes to a growing body of work concerned with explaining the uneven diffusion of ISO 14001 at the global level. Drawing from the existing theoretical and empirical literature we develop a series of hypotheses about how various economic, market, and regulatory factors influence the national count of ISO 14001 certifications. These hypotheses are then tested using econometric estimation techniques with data for a panel of 142 developed and developing countries. We find that per capita ISO 14001 counts are positively correlated with income per capita, stock of foreign direct investment, exports of goods and services to Europe and Japan, and pressure from civil society. Conversely, productivity and levels of state intervention are negatively correlated. The paper finishes by offering a number of recommendations to policymakers concerned with accelerating the diffusion of voluntary environmental standards