Light bullets in quadratic media with normal dispersion at the second harmonic

Stable two- and three-dimensional spatiotemporal solitons (STSs) in second-harmonic-generating media are found in the case of normal dispersion at the second harmonic (SH). This result, surprising from the theoretical viewpoint, opens a way for experimental realization of STSs. An analytical estimate for the existence of STSs is derived, and full results, including a complete stability diagram, are obtained in a numerical form. STSs withstand not only the normal SH dispersion, but also finite walk-off between the harmonics, and readily self-trap from a Gaussian pulse launched at the fundamental frequency.Comment: 4 pages, 5 figures, accepted to Phys. Rev. Let

A novel video-tracking system to quantify the behaviour of nocturnal mosquitoes attacking human hosts in the field

Many vectors of malaria and other infections spend most of their adult life within human homes, the environment where they bloodfeed and rest, and where control has been most successful. Yet, knowledge of peri-domestic mosquito behaviour is limited, particularly how mosquitoes find and attack human hosts or how insecticides impact on behaviour. This is partly because technology for tracking mosquitoes in their natural habitats, traditional dwellings in disease-endemic countries, has never been available. We describe a sensing device that enables observation and recording of nocturnal mosquitoes attacking humans with or without a bed net, in the laboratory and in rural Africa. The device addresses requirements for sub-millimetre resolution over a 2.0 x 1.2 x 2.0 m volume while using minimum irradiance. Data processing strategies to extract individual mosquito trajectories and algorithms to describe behaviour during host/net interactions are introduced. Results from UK laboratory and Tanzanian field tests showed that Culex quinquefasciatus activity was higher and focused on the bed net roof when a human host was present, in colonized and wild populations. Both C. quinquefasciatus and Anopheles gambiae exhibited similar behavioural modes, with average flight velocities varying by less than 10%. The system offers considerable potential for investigations in vector biology and many other fields

A two-species predator-prey model in an environment enriched by a biotic resource

Classical population growth models assume that the environmental carrying capacity is a fixed parameter, which is not often realistic. We propose a modified predator-prey model where the carrying capacity of the environment is dependent on the availability of a biotic resource. In this model both populations are able to consume the resource, thus altering the environment. Stability, bifurcation and numerical analyses are presented to illustrate the system's dynamical behaviour. Bistability occurs in certain parameter regions. This could describe the transition from a beneficial environment to a detrimental one. We examine special cases of the system and show that both permanence and extinction are possible. References J. Vandermeer. Seasonal isochronic forcing of Lotka Volterra equations. Prog. Theor. Phys., 96:13–28, 1996. doi:10.1143/PTP.96.13 S. Ikeda and T. Yokoi. Fish population dynamics under nutrient enrichment–-A case of the East Seto Inland Sea. Ecol. Model., 10:141–165, 1980. doi:10.1016/0304-3800(80)90057-5 S. P. Rogovchenko and Y. V. Rogovchenko. Effect of periodic environmental fluctuations on the Pearl–Verhulst model. Chaos, Solitons, Fractals, 39:1169–1181, 2009. doi:10.1016/j.chaos.2007.11.002 H. Safuan, I. N. Towers, Z. Jovanoski and H. S. Sidhu. A simple model for the total microbial biomass under occlusion of healthy human skin. In Chan, F., Marinova, D. and Anderssen, R.S. (eds) MODSIM2011, 19th International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand., 733–739, 2011. http://www.mssanz.org.au/modsim2011/AA/safuan.pdf P. Meyer and J. H. Ausubel. Carrying capacity: A model with logistically varying limits. Technol. Forecast. Soc., 61:209–214, 1999. doi:10.1016/S0040-1625(99)00022-0 R. Huzimura and T. Matsuyama. A mathematical model with a modified logistic approach for singly peaked population processes. Theor. Popul. Biol., 56:301–306, 1999. doi:10.1006/tpbi.1999.1426 J. H. M. Thornley and J. France. An open-ended logistic-based growth function. Ecol. Model., 184:257–261, 2005. doi:10.1016/j.ecolmodel.2004.10.007 J. H. M. Thornley, J. J. Shepherd and J. France. An open-ended logistic-based growth function: Analytical solutions and the power-law logistic model. Ecol. Model., 204:531–534, 2007. doi:10.1016/j.ecolmodel.2006.12.026 H. M. Safuan, I. N. Towers, Z. Jovanoski and H. S. Sidhu. Coupled logistic carrying capacity model. ANZIAM J, 53:C172–C184, 2012. http://journal.austms.org.au/ojs/index.php/ANZIAMJ/article/view/4972 P. H. Leslie and J. C. Gower. The properties of a stochastic model for the predator-prey type of interaction between two species. Biometrika, 47:219–234, 1960. doi:10.1093/biomet/47.3-4.219 B. Basener and D. S. Ross. Booming and crashing populations and Easter Island. SIAM J. Appl. Math., 65:684–701, 2005. doi:10.1137/S0036139903426952 D. Lacitignola and C. Tebaldi. Symmetry breaking effects on equilibria and time dependent regimes in adaptive Lotka–Volterra systems. Int. J. Bifurcat. Chaos, 13:375–392, 2003. doi:10.1142/S0218127403006595 F. Wang and G. Pang. Chaos and Hopf bifurcation of a hybrid ratio-dependent three species food chain. Chaos, Solitons, Fractals, 36:1366–1376, 2008. doi:10.1016/j.chaos.2006.09.005 R. Ball. Understanding critical behaviour through visualization: A walk around the pitchfork. Comput. Phys. Commun., 142:71–75, 2001. doi:10.1016/S0010-4655(01)00322-8 B. Ermentrout. XPP-Aut v. 6.00, 2011. http://www.math.pitt.edu/ bard/xpp/xpp.html R. Malka, E. Shochat and V. R. Kedar. Bistability and bacterial infections. PLOS ONE, 5:1–10, 2010. doi:10.1371/journal.pone.0010010 J. Elf, K. Nilsson, T. Tenson and M. Ehrenberg. Bistable bacterial growth rate in response to antibiotics with low membrane permeability. Phys. Rev. Lett., 97:258104, 2006. doi:10.1103/PhysRevLett.97.258104 D. Dubnau and R. Losick. Bistability in bacteria. Mol. Microbiol., 61:564–572, 2006. doi:10.1111/j.1365-2958.2006.05249.x M. Santillan. Bistable behavior in a model of the lac Operon in Escherichia coli with variable growth rate. Biophys. J., 94:2065–2081, 2008. doi:10.1529/biophysj.107.118026 M. Rosenzweig. Paradox of enrichment: destabilization of exploitation ecosystem in ecological time. Science, 171:385–387, 1971. doi:10.1126/science.171.3969.38

Mentoring for Faculty from Working-Class Backgrounds

Faculty mentoring across gender, race, and culture is facilitated by formal mentoring programs. Mentoring across the cultural differences associated with social class, however, represents a largely unaddressed gap in the provision of formal faculty mentoring. Based on a pre-program needs survey, we designed and delivered a pilot program that served working-class faculty with mentoring on career self-efficacy. Assessment showed that working-class faculty mentees made gains in this important construct. Our concluding discussion reflects upon the role of mentoring in the experience of working-class faculty

Polychromatic solitons in a quadratic medium

We introduce the simplest model to describe parametric interactions in a quadratically nonlinear optical medium with the fundamental harmonic containing two components with (slightly) different carrier frequencies [which is a direct analog of wavelength-division multiplexed (WDM) models, well known in media with cubic nonlinearity]. The model takes a closed form with three different second-harmonic components, and it is formulated in the spatial domain. We demonstrate that the model supports both polychromatic solitons (PCSs), with all the components present in them, and two types of mutually orthogonal simple solitons, both types being stable in a broad parametric region. An essential peculiarity of PCS is that its power is much smaller than that of a simple (usual) soliton (taken at the same values of control parameters), which may be an advantage for experimental generation of PCSs. Collisions between the orthogonal simple solitons are simulated in detail, leading to the conclusion that the collisions are strongly inelastic, converting the simple solitons into polychromatic ones, and generating one or two additional PCSs. A collision velocity at which the inelastic effects are strongest is identified, and it is demonstrated that the collision may be used as a basis to design a simple all-optical XOR logic gate.Comment: 9 pages, 8 figures, accepted to Phys. Rev.

Using ASCOT in care planning conversations

Report on a joint UK-Australian project which trialled a new and innovative use of the ASCOT tool in residential aged care planning to help staff initiate and hold conversations with residents, including those with dementia, about their emotional and social wellbeing