An Estimate of the Vibrational Frequencies of Spherical Virus Particles

The possible normal modes of vibration of a nearly spherical virus particle are discussed. Two simple models for the particle are treated, a liquid drop model and an elastic sphere model. Some estimates for the lowest vibrational frequency are given for each model. It is concluded that this frequency is likely to be of the order of a few GHz for particles with a radius of the order of 50 nm.Comment: 6 pages, 1 figur

Human disturbances and predation on artificial ground nests across an urban gradient

Perturbaciones antropogénicas y depredación en nidos artificiales en el suelo en un gradiente urbano En nuestro estudio con nidos artificiales observamos que la ausencia de especies de aves que nidifican en el suelo en el centro urbano y en barrios residenciales se debía a las molestias causadas por personas y animales domésticos (perros y gatos) y no a la depredación. Además, la presión por depredación fue superior en la periferia de la ciudad debido al mayor número de depredadores naturales. Nuestros resultados sugieren que la planificación y creación de zonas protegidas podrían aumentar la posibilidad de que las aves que nidifican en el suelo se establecieran y se reprodujeran en paisajes dominados por los humanos.Perturbaciones antropogénicas y depredación en nidos artificiales en el suelo en un gradiente urbano En nuestro estudio con nidos artificiales observamos que la ausencia de especies de aves que nidifican en el suelo en el centro urbano y en barrios residenciales se debía a las molestias causadas por personas y animales domésticos (perros y gatos) y no a la depredación. Además, la presión por depredación fue superior en la periferia de la ciudad debido al mayor número de depredadores naturales. Nuestros resultados sugieren que la planificación y creación de zonas protegidas podrían aumentar la posibilidad de que las aves que nidifican en el suelo se establecieran y se reprodujeran en paisajes dominados por los humanos.In our study with artificial nests we observed that the absence of ground nesting bird species in the city centre and in residential districts was due to disturbance by humans and domestic animals (dogs and cats) rather than to predation. Furthermore, predation pressure was higher in the outskirts of the city due to the greater number of natural predators. Our results suggest that planning and creating undisturbed areas could increase the chances of ground nesting birds settling and breeding in human–dominated landscapes

Tourism policy and destination marketing in developing countries: the chain of influence

Tourism marketers including destination marketing organisations (DMOs) and international tour operators play a pivotal role in destination marketing, especially in creating destination images. These images, apparent in tourist brochures, are designed to influence tourist decision-making and behaviour. This paper proposes the concept of a “chain of influence” in destination marketing and image-making, suggesting that the content of marketing materials is influenced by the priorities of those who design these materials, e.g. tour operators and DMOs. A content analysis of 2,000 pictures from DMO and tour operator brochures revealed synergies and divergence between these marketers. The brochure content was then compared to the South African tourism policy, concluding that the dominant factor in the chain of influence in the South African context is in fact its organic image

Camp Lwandle: Rehabilitating a migrant labour hostel at the seaside

In southern African narratives of migrant labour, hostels and compounds are represented as typical examples of colonial and apartheid planning. Visual and spatial comparisons are consistently made between the regulatory power of hostels and those of concentration camps. Several of these sites of violence and repression are today being reconfigured as sites of conscience, their artefactual presence on the landscape being constructed as places of remembrance. In this trajectory, a space of seeming anonymity in Lwandle, some 40 km outside of Cape Town, was identified by the newly established museum, at the beginning of the twenty-first century, as a structure of significance. The migrant labour compound in Lwandle, of which Hostel 33 is the last remnant, was designed by planners and engineers and laid out as part of a labour camp for male migrant workers in the 1950s. This article explores the ambitious project initiated in 2008, by the Lwandle Migrant Labour Museum (and funded largely by the US Ambassadors Cultural Restoration Fund), to restore Hostel 33. Although Hostel 33 was not a very old structure, having been built in 1958/9, nor was it easily considered to have conventional architectural significance, its material presence in present-day Lwandle represents a reminder of the conditions of life in the labour camp. The article traces the work entailed in the restoration process through paying attention to both the built fabric and its materiality, and by giving an account of the explorations into finding ways to restore the hostel to the museum through making it into a site of significance. In place of the centrality of the building as the object of restoration, the work shifted to considering how the hostel could function most effectively as a stage and destination for the Museum’s narrations of the past. Retaining and maintaining Hostel 33 was less concerned with the fabric as an empirical fact of the past, than with its projection into an envisaged future for museum purposes.Department of HE and Training approved lis

Numerical study of linear and circular model DNA chains confined in a slit: metric and topological properties

Advanced Monte Carlo simulations are used to study the effect of nano-slit confinement on metric and topological properties of model DNA chains. We consider both linear and circularised chains with contour lengths in the 1.2--4.8 $\mu$m range and slits widths spanning continuously the 50--1250nm range. The metric scaling predicted by de Gennes' blob model is shown to hold for both linear and circularised DNA up to the strongest levels of confinement. More notably, the topological properties of the circularised DNA molecules have two major differences compared to three-dimensional confinement. First, the overall knotting probability is non-monotonic for increasing confinement and can be largely enhanced or suppressed compared to the bulk case by simply varying the slit width. Secondly, the knot population consists of knots that are far simpler than for three-dimensional confinement. The results suggest that nano-slits could be used in nano-fluidic setups to produce DNA rings having simple topologies (including the unknot) or to separate heterogeneous ensembles of DNA rings by knot type.Comment: 12 pages, 10 figure

Structure and dynamics of ring polymers: entanglement effects because of solution density and ring topology

The effects of entanglement in solutions and melts of unknotted ring polymers have been addressed by several theoretical and numerical studies. The system properties have been typically profiled as a function of ring contour length at fixed solution density. Here, we use a different approach to investigate numerically the equilibrium and kinetic properties of solutions of model ring polymers. Specifically, the ring contour length is maintained fixed, while the interplay of inter- and intra-chain entanglement is modulated by varying both solution density (from infinite dilution up to \approx 40 % volume occupancy) and ring topology (by considering unknotted and trefoil-knotted chains). The equilibrium metric properties of rings with either topology are found to be only weakly affected by the increase of solution density. Even at the highest density, the average ring size, shape anisotropy and length of the knotted region differ at most by 40% from those of isolated rings. Conversely, kinetics are strongly affected by the degree of inter-chain entanglement: for both unknots and trefoils the characteristic times of ring size relaxation, reorientation and diffusion change by one order of magnitude across the considered range of concentrations. Yet, significant topology-dependent differences in kinetics are observed only for very dilute solutions (much below the ring overlap threshold). For knotted rings, the slowest kinetic process is found to correspond to the diffusion of the knotted region along the ring backbone.Comment: 17 pages, 11 figure

Sexual harassment in an east African agribusiness supply chain

This article discusses sexual harassment in the east African cut-flower and horticultural industry, based on research on 62 farms in Ethiopia, Kenya, Tanzania and Uganda. It argues that sexual harassment is fostered both by coercive labour conditions within global value chains and by existing hierarchical gender relations. The research finds that harassment is widespread, that many lack a vocabulary to describe or discuss this, and that female casual and temporary workers are most likely to be targeted. Action research coupled with organisation of workers, however, has been effective in giving ‘voice’ to those suffering harassment: this is a first step in a feminist labour mobilisation and policy formulation. Procedures against sexual harassment are beginning to be formulated: a key concern is implementation. Addressing sexual harassment is central in ensuring the security of working people, particularly the most marginalised

Microstructure and indentation mechanical properties of YSZ nanostructured coatings obtained by suspension plasma spraying

[EN] A commercial nanosuspension of yttria-stabilised zirconia (YSZ) was successfully deposited on austenitic stainless steel substrate by suspension plasma spraying technique (SPS). A SG-100 torch with internal radial injection was used for the spraying. The pneumatic system transported the feed suspension from the containers to the plasma torch. In order to study the effect of the spraying parameters, a factorial model was used to design the experiments, changing both spraying translation speed and suspension flow rate. The coating microstructure was characterised by FEG-SEM. All coatings displayed a two-zone microstructure formed by nanometre-sized particles surrounded by fully molten areas. Moreover, crystalline phases were determined by XRD and Raman spectroscopy. Mechanical properties were also determined using nanoindentation technique. Nanoindentation tests showed a bimodal distribution of the mechanical properties (hardness and Young's modulus) which is related to the two zones (molten and partially molten) present in the coatings. (C) 2012 Elsevier B.V. All rights reserved.This work has been supported by the Spanish Ministry of Science and Innovation (project MAT2009-14144-C03) and the Research Promotion Plan of the Universitat Jaume I, action 2.1 (ref. E-2011-05) and action 3.1 (ref. PREDOC/2009/10). The authors are grateful to Leszek Łatka for his help in plasma spray experiments.Carpio, P.; Rayón Encinas, E.; Pawlowski, L.; Cattini, A.; Benavente Martínez, R.; Bannier, E.; Salvador Moya, MD.... (2013). Microstructure and indentation mechanical properties of YSZ nanostructured coatings obtained by suspension plasma spraying. Surface and Coatings Technology. 220:237-243. https://doi.org/10.1016/j.surfcoat.2012.09.047S23724322

The Tumor Microenvironment: The Making of a Paradigm

What has been will be again, what has been done will be done again; there is nothing new under the su

Community engagement and professionalization: Emerging tensions

© 2019 by Emerald Publishing Limited. An increase in community engagement by governments across Australia’s three-tiered federal polity conforms to international trends. It represents a multidimensional institutionalization of participatory democracy designed to involve the public in decision-making. Increasingly, it is a practice which displays the markers of professionalization, including (self-described) professionals, professional associations and a code of ethics. The individuals who design, communicate, and facilitate community engagement are placed in a unique position, whereas most professions claim to serve both their client or employer and a greater public good, community engagement practitioners play these roles while also claiming to serve as “guardians” of democratic processes. Yet the claimed professionalization of community engagement is raising some questions: Is community engagement really a profession – and by what criteria ought this be assessed? What tensions do community engagement practitioners face by “serving multiple masters,” and how do they manage these? More pointedly, how can ethics inform our understanding of community engagement and its professionalization? This chapter examines the case for the practice of community engagement as a profession using Noordegraaf’s (2007) pillars of pure professionalism as a guide. It then explores some practical examples of the tensions practitioners may experience. The chapter concludes by reflecting on the future direction of community engagement given its positioning