Multi-particle Correlations in Quaternionic Quantum Systems

We investigate the outcomes of measurements on correlated, few-body quantum systems described by a quaternionic quantum mechanics that allows for regions of quaternionic curvature. We find that a multi-particle interferometry experiment using a correlated system of four nonrelativistic, spin-half particles has the potential to detect the presence of quaternionic curvature. Two-body systems, however, are shown to give predictions identical to those of standard quantum mechanics when relative angles are used in the construction of the operators corresponding to measurements of particle spin components.Comment: REVTeX 3.0, 16 pages, no figures, UM-P-94/54, RCHEP-94/1

Finite element analysis applied to redesign of submerged entry nozzles for steelmaking

The production of steel by continuous casting is facilitated by the use of refractory hollow-ware components. A critical component in this process is the submerged entry nozzle (SEN). The normal operating conditions of the SEN are arduous, involving large temperature gradients and exposure to mechanical forces arising from the flow of molten steel; experimental development of the components is challenging in so hazardous an environment. The effects of the thermal stress conditions in relation to a well-tried design were therefore simulated using a finite element analysis approach. It was concluded from analyses that failures of the type being experienced are caused by the large temperature gradient within the nozzle. The analyses pointed towards a supported shoulder area of the nozzle being most vulnerable to failure and practical in-service experience confirmed this. As a direct consequence of the investigation, design modifications, incorporating changes to both the internal geometry and to the nature of the intermediate support material, were implemented, thereby substantially reducing the stresses within the Al2O3/graphite ceramic liner. Industrial trials of this modified design established that the component reliability would be significantly improved and the design has now been implemented in series production

Topological Phase Transitions and Holonomies in the Dimer Model

We demonstrate that the classical dimer model defined on a toroidal hexagonal lattice acquires holonomy phases in the thermodynamic limit. When all activities are equal the lattice sizes must be considered mod 6 in which case the finite size corrections to the bulk partition function correspond to a massless Dirac Fermion in the presence of a flat connection with nontrivial holonomy. For general bond activities we find that the phase transition in this model is a topological one, where the torus degenerates and its modular parameter becomes real at the critical temperature. We argue that these features are generic to bipartite dimer models and we present a more general lattice whose continuum partition function is that of a massive Dirac Fermion.Comment: 7 pages, 4 figures. Minor corrections with additional figure

Wiretapping a hidden network

We consider the problem of maximizing the probability of hitting a strategically chosen hidden virtual network by placing a wiretap on a single link of a communication network. This can be seen as a two-player win-lose (zero-sum) game that we call the wiretap game. The value of this game is the greatest probability that the wiretapper can secure for hitting the virtual network. The value is shown to equal the reciprocal of the strength of the underlying graph. We efficiently compute a unique partition of the edges of the graph, called the prime-partition, and find the set of pure strategies of the hider that are best responses against every maxmin strategy of the wiretapper. Using these special pure strategies of the hider, which we call omni-connected-spanning-subgraphs, we define a partial order on the elements of the prime-partition. From the partial order, we obtain a linear number of simple two-variable inequalities that define the maxmin-polytope, and a characterization of its extreme points. Our definition of the partial order allows us to find all equilibrium strategies of the wiretapper that minimize the number of pure best responses of the hider. Among these strategies, we efficiently compute the unique strategy that maximizes the least punishment that the hider incurs for playing a pure strategy that is not a best response. Finally, we show that this unique strategy is the nucleolus of the recently studied simple cooperative spanning connectivity game

Identifying a sufficient core group for trachoma transmission.

BackgroundIn many infectious diseases, a core group of individuals plays a disproportionate role in transmission. If these individuals were effectively prevented from transmitting infection, for example with a perfect vaccine, then the disease would disappear in the remainder of the community. No vaccine has yet proven effective against the ocular strains of chlamydia that cause trachoma. However, repeated treatment with oral azithromycin may be able to prevent individuals from effectively transmitting trachoma.Methodology/principal findingsHere we assess several methods for identifying a core group for trachoma, assuming varying degrees of knowledge about the transmission process. We determine the minimal core group from a completely specified model, fitted to results from a large Ethiopian trial. We compare this benchmark to a core group that could actually be identified from information available to trachoma programs. For example, determined from the rate of return of infection in a community after mass treatments, or from the equilibrium prevalence of infection.Conclusions/significanceSufficient groups are relatively easy for programs to identify, but will likely be larger than the theoretical minimum

Quaternionic Electroweak Theory and CKM Matrix

We find in our quaternionic version of the electroweak theory an apparently hopeless problem: In going from complex to quaternions, the calculation of the real-valued parameters of the CKM matrix drastically changes. We aim to explain this quaternionic puzzle.Comment: 8, Revtex, Int. J. Theor. Phys. (to be published

An ecomimicry design approach for extensive green roofs

Extensive green roofs (EGRs) have been promoted as a multifunctional urban green infrastructure (UGI) solution that can ameliorate some of the negative environmental effects associated with urbanisation and provide habitat for wildlife. To date ecological EGR research remains limited, yet studying and understanding the ecology and ecological processes of these novel urban ecosystems could maximise their potential to conserve biodiversity and deliver multiple ecosystem services to urban areas. Here we present an overview of how a novel ‘ecomimicry’ approach can be used to ensure that locally important habitats are created and restored as part of urban green infrastructure strategies, and that biodiversity is embedded at the heart of EGR design. This can help urban developments meet sustainability targets and contribute to the goal of no-net-loss of biodiversity. Conserving urban biodiversity through ecomimicry will increase opportunities for urban communities to reconnect with nature and improve the quality of life for people in cities

A simple method for finite range decomposition of quadratic forms and Gaussian fields

We present a simple method to decompose the Green forms corresponding to a large class of interesting symmetric Dirichlet forms into integrals over symmetric positive semi-definite and finite range (properly supported) forms that are smoother than the original Green form. This result gives rise to multiscale decompositions of the associated Gaussian free fields into sums of independent smoother Gaussian fields with spatially localized correlations. Our method makes use of the finite propagation speed of the wave equation and Chebyshev polynomials. It improves several existing results and also gives simpler proofs.Comment: minor correction for t<

Flutuações diárias na associação de peixes da praia de areia de Porto Pim, ilha de Faial, Açores

Os peixes da praia de areia de Porto Pim, Açores foram amostrados através de arrastos de rede (chinchorro) a intervalos de três horas durante um período de 24 horas nos meses de Agosto, Setembro e Outubro de 1989. A associação de peixes era dominada, em cada um dos meses, por três a quatro espécies (90-97% dos indivíduos). A maioria das espécies estavam representadas por formas juvenis. A variação entre meses do padrão diário pode explicar-se primariamente pelas mudanças no padrão de abundância das espécies dominantes. Ao longo dos três meses as variações na estrutura da associação implicaram mudanças no padrão diário. Muitas das espécies tinham um padrão de abundância definido, primariamente por ser ou diurno ou nocturno. Encontrou-se também um padrão de maré na estrutura da associação de peixes caracterizado por uma maior diversidade na maré baixa.ABSTRACT: The shallow-water fish assemblage at Porto Pim, Azores was sampled with a beach seine at three hour intervals over 24 h periods in August, September and October 1989. The fish assemblage was dominated by three to four species in each month (90-97% of numbers). Most species were present as juveniles. The variation in diel patterns between months could primarily be explained by changes in the pattern of abundance of dominant species. Over the three months seasonal changes in the assemblage structure caused changes in the diel pattern. Many of the species present had a definite pattern to their abundance being either primarily diurnal or nocturnal. There was also a tidal pattern to the assemblage structure which had a higher diversity at low water

Associações de peixes das zonas entre-marés da ilha do Faial, Açores

No presente artigo descrevemos as associações de peixes das poças do intertidal rochoso e do intertidal arenoso dos Açores. São treze as espécies que ocorrem nas poças do intertidal rochoso. Os blenídeos, com Parablennius sanguinolentus parvicornis, Coryphoblennius galerita e Lipophrys trigloides, constituem a família dominante de peixes residentes das poças do intertidal rochoso. A riqueza é maior no 3º trimestre, com 12 espécies, e menor no 1º trimestre com apenas oito espécies a ocorrerem nas poças. A diversidade é também superior no 3º trimestre. O pequeno grau de variação pode ser fundamentalmente atribuído à presença de espécies transientes e de juvenis que utilizam a costa durante as primeiras fases de desenvolvimento. São quinze as espécies que ocorrem na zona intertidal da praia arenosa de Porto Pim. A comunidade de peixes é aqui dominada por juvenis de espécies transientes. Não encontrámos espécies intertidais residentes. A riqueza e abundância são superiores no 3º e 4º trimestre devido ao recrutamento de juvenis, e à ocorrência de espécies migradoras e transientes.ABSTRACT: In the present paper we describe fish assemblages of rocky intertidal pools and intertidal areas of sandy beaches of the Azores. Blennies (Parablennius sanguinolentus parvicornis, Coryphoblennius galerita and Lipophrys trigloides) constitute the dominant resident fish family in the intertidal pools. Thirteen species were encountered in intertidal pools. Richness is higher in the 3rd quarter of the year with 12 species and lower in the 1st and 2nd quarters with 8 species occurring in the samples . Diversity is also higher in the 3rd quarter The small variation can mostly be attributed to transient species and juveniles using the shore as a nursery ground. Fifteen species occurred in the intertidal region of the protected shallow sandy beach of Porto Pim. This fish assemblage was dominated by juveniles of transient species. No resident species were present here. Richness and abundance were higher in 3rd and 4th quarters due to recruitment of juveniles, and the occurrence of migrant and transient species