Tuning of tetrahedrality in a silicon potential yields a series of monatomic (metal-like) glassformers of very high fragility

We obtain monatomic glass formers in simulations by modifying the tetrahedral character in a silicon potential to explore a triple point zone between potentials favoring diamond (dc) and bcc crystals. dc crystallization is always preceded by a polyamorphic transformation of the liquid, and is frustrated when the Kauzmann temperature of the high temperature liquid intersects the liquid-liquid coexistence line. The glass forming liquids are extraordinarily fragile. Our results suggest that Si and Ge liquids may be vitrified at a pressure close to the diamond-beta-tin-liquid triple point.Comment: 12 pages, including 3 figures. This revised version covers the same as the original submission plus a discussion of the effect of the polyamorphic transformation on the glass formation ability of the tetrahedral liquids studie

The angular nature of road networks

Road networks are characterised by several structural and geometrical properties. The topological structure determines partially the hierarchical arrangement of roads, but since these are networks that are spatially constrained, geometrical properties play a fundamental role in determining the network’s behaviour, characterising the influence of each of the street segments on the system. In this work, we apply percolation theory to the UK’s road network using the relative angle between street segments as the occupation probability. The appearance of the spanning cluster is marked by a phase transition, indicating that the system behaves in a critical way. Computing Shannon’s entropy of the cluster sizes, different stages of the percolation process can be discerned, and these indicate that roads integrate to the giant cluster in a hierarchical manner. This is used to construct a hierarchical index that serves to classify roads in terms of their importance. The obtained classification is in very good correspondence with the official designations of roads. This methodology hence provides a framework to consistently extract the main skeleton of an urban system and to further classify each road in terms of its hierarchical importance within the system

Expansion of a one-dimensional Bose gas: the role of interactions and kinetic-energy driving

We study the expansion of a one-dimensional boson gas by suddenly increasing the length of the chain where it resides. We consider three initial ground-state configurations: the Mott insulator, the conventional superfluid clumped around zero momentum, and the cat-like state with peaks at momenta $\pm \pi/2$, resulting from rapid kinetic driving. In turn, we consider three types of expansion: spectroscopic (with interactions tuned to zero), dynamic (with standard short-range repulsive interactions) and under kinetic driving. The numerical calculations are exact. We compute the momentum- and real-space one-particle densities as well as the two-particle momentum correlations. The spectroscopic time-of-flight experiment faithfully reflects the initial momentum distribution. For the dynamic expansion starting from an insulator, we reproduce the non-equilibrium quasi-condensation into momenta $\pm \pi/2$ while noticing correlations in the momentum distribution, and provide an intuitive physical picture. A discussion of various measures of the momentum correlations is also presented.Comment: 19 pages, 8 figures. Slightly revised in response to referee report

La entrevista de trabajo: Expectativas pragmáticas del aprendiente de ELE árabe marroquí

Esta investigación analiza las expectativas pragmáticas en el ámbito de la entrevista de trabajo de los aprendientes de ELE con L1 árabe marroquí o dariya e investiga si en ese contexto existen diferencias significativas entre estos y los hablantes nativos de español peninsular. A través de cuestionarios con escala Likert, la categorización de las respuestas y su comparación a través de un análisis correlacional por medio del estadístico Pearson, comprobamos que hay un comportamiento diferencial entre ambos grupos explicable como un proceso de transferencia de la pragmática de la L1 a la L2. Los resultados obtenidos pueden ser muy interesantes para la creación de nuevos materiales en ELE y para la investigación sobre la comunicación intercultural. This research analyzes the pragmatic expectations in the field of the job interview of the learners of ELE with L1 Arabic Moroccan or dariya and it investigates if in that context there are significant differences between these and the native speakers of Peninsular Spanish. Through questionnaires with Likert scale, the categorization of responses and their comparison by a correlational analysis (Pearson statistic), we have checked that there is a differential behavior between the two groups explainable as a process of Pragmatic Transfer from L1 to L2. The results obtained can be very interesting for the creation of new ELE materials and for the research on intercultural communication

Biomechanics of fish swimming in a hydrokinetic turbine wake

In the present paper, the assessment of the hydrodynamics of the fish swimming in undisturbed and altered wake-flow is carried out identifying hydrodynamical forces and flow patterns of the fish swimming wake. URANS approach with k-omega/SST turbulence model are employed combining fish and turbine in the same simulation. Fish motion is realized using dynamically adaptive mesh. The actuator line method is employed to induce the wake of a hydrokinetic turbine, which is a simplified method that requires lower computational cost than full geometry simulations. This work brings a new numerical approach involving fish and turbine wake highlighting that fish swimming in the wake presents higher thrust forces than in the undisturbed flow, due to the x-component to velocity in the wake is lower than free flow velocity

Cities and regions in Britain through hierarchical percolation

Urban systems present hierarchical structures at many different scales. These are observed as administrative regional delimitations which are the outcome of complex geographical, political and historical processes which leave almost indelible footprints on infrastructure such as the street network. In this work, we uncover a set of hierarchies in Britain at different scales using percolation theory on the street network and on its intersections which are the primary points of interaction and urban agglomeration. At the larger scales, the observed hierarchical structures can be interpreted as regional fractures of Britain, observed in various forms, from natural boundaries, such as National Parks, to regional divisions based on social class and wealth such as the well-known North–South divide. At smaller scales, cities are generated through recursive percolations on each of the emerging regional clusters. We examine the evolution of the morphology of the system as a whole, by measuring the fractal dimension of the clusters at each distance threshold in the percolation. We observe that this reaches a maximum plateau at a specific distance. The clusters defined at this distance threshold are in excellent correspondence with the boundaries of cities recovered from satellite images, and from previous methods using population density

Tourism gender research: A critical accounting

This paper seeks to rouse debate about the workings of tourism enquiry as a knowledge-generating system through its critical accounting of the sub-field of tourism gender research. This accounting includes a gender-aware bibliometric analysis of 466 journal papers published during 1985–2012, which categorises the sub-field’s prevailing themes and methodologies and identifies its most prolific authors and popular journals. It contends that, despite three decades of study and a recent increase in papers, tourism gender research remains marginal to tourism enquiry, disarticulated from wider feminist and gender-aware initiatives and lacks the critical mass of research leaders, publications, citations and multi-institutional networks, which characterise other tourism sub-fields. The paper identifies two possible futures for gender-aware tourism research: stagnation or ignition

Dominance of the planktonic diatom Thalassiosira minima in recent summers in the Bahia Blanca Estuary, Argentina

The diatom Thalassiosira minima was first recorded in the Baha Blanca Estuary in 1992. In 19921993 it exhibited a broad seasonal occurrence. A recent survey (20062007) showed a seasonal appearance restricted mainly to summer together with a greater relative abundance within the phytoplankton. A close connection was found with warmer, more saline and highly turbid conditions experienced in recent summers in the estuary. Whether these changes will impact the estuary trophic dynamics remains an open question

Clashing institutional interests in skills between government and industry: An analysis of demand for technical and soft skills of graduates in the UK

Technological knowledge and skills provide a basis for developing national competitiveness. However, there is an emerging clash of interests in the UK labour market between employers and policy makers. The former requests highly skilled workers who often jealously train in house for their specific operations while the latter aims to reduce unemployment through the expansion of vocational training to lower skilled workers. Universities need to find their strategic position in the knowledge economy characterised by radical technological change and shifting occupational structure by meeting the future skills demand while balancing between the clashing institutional interests. This study analyses 510 job advertisements in the supply chain management area, using a combination of OMDS and HCA techniques. The advertisements are categorised by means of six dimensions according to the skills, duties and job type. This study analyses not only employers' needs in skill types according to job roles but also emerging institutional clashes in the job market and their implications for skills training policy and curriculum development

Seasonal and interannual variability of cladoceran communities in two peri-alpine lakes: uncoupled response to the 2003 heat wave

Seasonal and interannual dynamics of cladoceran species were analyzed during the period 1995–2003 in two deep peri-alpine lakes morphologically different but subjected to similar regional climatic forcing. The seasonal succession of cladoceran species was characterized and the impact of extreme climatic events on the annual pattern of species succession was assessed. Using a multivariate method, we show that the cladoceran species display marked seasonality patterns that differed in the two lakes. The differences observed between the lakes were driven by their trophic state, the plankton species composition and the abundance of predators. We show that the sensitivity of the annual pattern of species succession to extreme weather changes, illustrated by the 2003 heat wave, differs markedly in these two lakes. In Lake Annecy, the annual pattern of cladoceran succession observed in 2003 is not different from the one usually observed. In contrast, in Lake Geneva, the annual pattern recorded in 2003 is unusual and characterized by the maintenance of herbivorous cladocera during summer. These findings underline the need to consider the morphology of lakes and trophic state in the assessment of ecological responses to global warming. Our results contribute to the debate about the predictability of the impacts of climate change on aquatic ecosystems, and their extrapolation from one site to another