On Cr−C^r-closing for flows on 2-manifolds

For some full measure subset B of the set of iet's (i.e. interval exchange transformations) the following is satisfied: Let X be a $C^r$, $1\le r\le \infty$, vector field, with finitely many singularities, on a compact orientable surface M. Given a nontrivial recurrent point $p\in M$ of X, the holonomy map around p is semi-conjugate to an iet $E :[0,1) \to [0,1).$ If $E\in B$ then there exists a $C^r$ vector field Y, arbitrarily close to X, in the $C^r-$topology, such that Y has a closed trajectory passing through p.Comment: 7 pages, 1 figur

Prediction and prevention of the next pandemic zoonosis.

Most pandemics--eg, HIV/AIDS, severe acute respiratory syndrome, pandemic influenza--originate in animals, are caused by viruses, and are driven to emerge by ecological, behavioural, or socioeconomic changes. Despite their substantial effects on global public health and growing understanding of the process by which they emerge, no pandemic has been predicted before infecting human beings. We review what is known about the pathogens that emerge, the hosts that they originate in, and the factors that drive their emergence. We discuss challenges to their control and new efforts to predict pandemics, target surveillance to the most crucial interfaces, and identify prevention strategies. New mathematical modelling, diagnostic, communications, and informatics technologies can identify and report hitherto unknown microbes in other species, and thus new risk assessment approaches are needed to identify microbes most likely to cause human disease. We lay out a series of research and surveillance opportunities and goals that could help to overcome these challenges and move the global pandemic strategy from response to pre-emption

Spatial modeling of carnivore distribution and viability

Viability analysis of well-selected focal species can complement other types of conservation planning by revealing thresholds in habitat area and landscape connectivity that may not be evident from ecosystem-level evaluations. I used focal species analysis of five carnivores to suggest conservation planning guidelines for the Rocky Mountains and adjacent areas in the Pacific states. I compared static and dynamic viability models for carnivores to assess whether the increased complexity of dynamic simulation models was appropriate given the level of demographic field data typical for carnivore species. I developed models of fisher, lynx, and wolverine distribution from a data set of trapping and sighting records and predicted grizzly bear habitat by adapting previously published regional-scale habitat models. Highquality habitats for wolverine and grizzly bear are strongly associated with low levels of human population and roads. High-quality habitats for fisher and lynx are naturally fragmented by topography and vegetation gradients and are poorly represented in existing protected areas. A comprehensive conservation strategy for carnivores in the region must therefore consider the needs of several species rather than a singie presumed umbrella species. Because many large carnivores are habitat generalists limited by human persecution, and easily-measured attributes such as road density provide robust surrogates for human impact, extrapolation of static habitat models to potential reintroduction areas provides useful guidance for prioritizing carnivore restoration efforts. I also incorporated the static modeling results into a dynamic model. For the wolf; incorporating pack structure into the simulation model increased resilience to human-associated landscape change. For the lynx, relatively low levels of population cycling were found to greatly increase extinction risk when the region was isolated from boreal lynx populations. For the fisher, mortality levels were found to interact strongly with habitat area and isolation to create tlaeshold effects on distribution. Further range contraction is predicted for all species unless coordinated regional planning for habitat restoration occurs. The results suggest that a hybrid approach that builds complex dynamic models on a foundation of data from empirical static models can provide complementary results with a range of perspectives on species' persistence

Atypical use of audience response system provides opportunity to formatively assess faculty teaching and improve learning outcomes

In response to curricular reform, a particularly effective new approach was developed for a course offered at all nine IUSM centers. Participants will learn about interdisciplinary planning, implementation of a "Grand Rounds" approach, novel use of audience response system for retrieval practice and formative assessment of teaching methods, and how Bloom scale ratings relate to student engagement and focus

Hierarchical Bayesian Spatial Models for Multispecies Conservation Planning and Monitoring

Biologists who develop and apply habitat models are often familiar with the statistical challenges posed by their data’s spatial structure but are unsure of whether the use of complex spatial models will increase the utility of model results in planning. We compared the relative performance of nonspatial and hierarchical Bayesian spatial models for three vertebrate and invertebrate taxa of conservation concern (Church’s sideband snails [Monadenia churchi], red tree voles [Arborimus longicaudus], and Pacific fishers [Martes pennanti pacifica]) that provide examples of a range of distributional extents and dispersal abilities. We used presence–absence data derived from regional monitoring programs to develop models with both landscape and site-level environmental covariates. We used Markov chain Monte Carlo algorithms and a conditional autoregressive or intrinsic conditional autoregressive model framework to fit spatial models. The fit of Bayesian spatial models was between 35 and 55% better than the fit of nonspatial analogue models. Bayesian spatialmodels outperformed analogousmodels developed with maximum entropy (Maxent) methods. Although the best spatial and nonspatial models included similar environmental variables, spatial models provided estimates of residual spatial effects that suggested how ecological processes might structure distribution patterns. Spatialmodels built from presence–absence data improved fit most for localized endemic species with ranges constrained by poorly known biogeographic factors and for widely distributed species suspected to be strongly affected by unmeasured environmental variables or population processes. By treating spatial effects as a variable of interest rather than a nuisance, hierarchical Bayesian spatial models, especially when they are based on a common broad-scale spatial lattice (here the national Forest Inventory and Analysis grid of 24 km2 hexagons), can increase the relevance of habitat models to multispecies conservation planning

EXPERIMENTAL INVESTIGATION OF INERTIAL MIXING IN DROPLETS

ABSTRACT Achieving the fast mixing requirements posed by the chemical, biological, and life science community for confined microchannel flows remains an engineering challenge. The viscous and surface tension forces that dominate conventional micro-flows undermine fast, efficient mixing. By increasing the collisional velocity of reagent droplets, inertia can be exploited to increase mixing rates. This paper experimentally investigates inertial droplet mixing in micro flows. A high speed, gaseous flow is used to detach, transport, and collide droplets of nanoliter-size volumes in standard T and Yjunction microchannel geometries. Mixing rates are quantified using differential fluorescent optical diagnostics. Measured droplet mixing times are compared to the characteristic time scales for mass and viscous diffusion and bulk convection. Results show that mixing times are decreased as the droplet inertia is increased, indicating the potential benefit of inertiadriven mixing

Equivalence of the Path Integral for Fermions in Cartesian and Spherical Coordinates

The path-integral calculation for the free energy of a spin-1/2 Dirac-fermion gas is performed in spherical polar coordinates for a flat spacetime geometry. Its equivalence with the Cartesian-coordinate representation is explicitly established. This evaluation involves a relevant limiting case of the fermionic path integral in a Schwarzschild background, whose near-horizon limit has been shown to be related to black hole thermodynamics.Comment: 16 page

Gravity on codimension 2 brane worlds

We compute the matching conditions for a general thick codimension 2 brane, a necessary previous step towards the investigation of gravitational phenomena in codimension 2 braneworlds. We show that, provided the brane is weakly curved, they are specified by the integral in the extra dimensions of the brane energy-momentum, independently of its detailed internal structure. These general matching conditions can then be used as boundary conditions for the bulk solution. By evaluating Einstein equations at the brane boundary we are able to write an evolution equation for the induced metric on the brane depending only on physical brane parameters and the bulk energy-momentum tensor. We particularise to a cosmological metric and show that a realistic cosmology can be obtained in the simplest case of having just a non-zero cosmological constant in the bulk. We point out several parallelisms between this case and the codimension 1 brane worlds in an AdS space.Comment: 24 page