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

Fractal Dimension and Localization of DNA Knots

The scaling properties of DNA knots of different complexities were studied by atomic force microscope. Following two different protocols DNA knots are adsorbed onto a mica surface in regimes of (i) strong binding, that induces a kinetic trapping of the three-dimensional (3D) configuration, and of (ii) weak binding, that permits (partial) relaxation on the surface. In (i) the gyration radius of the adsorbed DNA knot scales with the 3D Flory exponent $\nu\approx 0.58$ within error. In (ii), we find $\nu\approx 0.66$, a value between the 3D and 2D ($\nu=3/4$) exponents, indicating an incomplete 2D relaxation or a different polymer universality class. Compelling evidence is also presented for the localization of the knot crossings in 2D.Comment: 4 pages, 3 figure

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

Mathematical stories: Why do more boys than girls choose to study mathematics at AS-level in England?

Copyright @ 2005 Taylor & FrancisIn this paper I address the question: How is it that people come to choose mathematics and in what ways is this process gendered? I draw on the findings of a qualitative research study involving interviews with 43 young people all studying mathematics in post-compulsory education in England. Working within a post-structuralist framework, I argue that gender is a project and one that is achieved in interaction with others. Through a detailed reading of Toni and Claudia’s stories I explore the tensions for young women who are engaging in mathematics, something that is discursively inscribed as masculine, while (understandably) being invested in producing themselves as female. I conclude by arguing that seeing ‘doing mathematics’ as ‘doing masculinity’ is a productive way of understanding why mathematics is so male dominated and by looking at the implications of this understanding for gender and mathematics reform work.This work is funded by the ESR

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

Prognóstico de cães com tumor de mastócitos tratados cirurgicamente: análise de 18 casos

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