Is the even distribution of insecticide-treated cattle essential for tsetse control? Modelling the impact of baits in heterogeneous environments

Background: Eliminating Rhodesian sleeping sickness, the zoonotic form of Human African Trypanosomiasis, can be achieved only through interventions against the vectors, species of tsetse (Glossina). The use of insecticide-treated cattle is the most cost-effective method of controlling tsetse but its impact might be compromised by the patchy distribution of livestock. A deterministic simulation model was used to analyse the effects of spatial heterogeneities in habitat and baits (insecticide-treated cattle and targets) on the distribution and abundance of tsetse. Methodology/Principal Findings: The simulated area comprised an operational block extending 32 km from an area of good habitat from which tsetse might invade. Within the operational block, habitat comprised good areas mixed with poor ones where survival probabilities and population densities were lower. In good habitat, the natural daily mortalities of adults averaged 6.14% for males and 3.07% for females; the population grew 8.46in a year following a 90% reduction in densities of adults and pupae, but expired when the population density of males was reduced to <0.1/km2; daily movement of adults averaged 249 m for males and 367 m for females. Baits were placed throughout the operational area, or patchily to simulate uneven distributions of cattle and targets. Gaps of 2–3 km between baits were inconsequential provided the average imposed mortality per km2 across the entire operational area was maintained. Leaving gaps 5–7 km wide inside an area where baits killed 10% per day delayed effective control by 4–11 years. Corrective measures that put a few baits within the gaps were more effective than deploying extra baits on the edges. Conclusions/Significance: The uneven distribution of cattle within settled areas is unlikely to compromise the impact of insecticide-treated cattle on tsetse. However, where areas of >3 km wide are cattle-free then insecticide-treated targets should be deployed to compensate for the lack of cattle

Dynamics of myosin, microtubules, and Kinesin-6 at the cortex during cytokinesis in Drosophila S2 cells

© The Authors, 2009 . This article is distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. The definitive version was published in Journal of Cell Biology 186 (2009): 727-738, doi:10.1083/jcb.200902083.Signals from the mitotic spindle during anaphase specify the location of the actomyosin contractile ring during cytokinesis, but the detailed mechanism remains unresolved. Here, we have imaged the dynamics of green fluorescent protein–tagged myosin filaments, microtubules, and Kinesin-6 (which carries activators of Rho guanosine triphosphatase) at the cell cortex using total internal reflection fluorescence microscopy in flattened Drosophila S2 cells. At anaphase onset, Kinesin-6 relocalizes to microtubule plus ends that grow toward the cortex, but refines its localization over time so that it concentrates on a subset of stable microtubules and along a diffuse cortical band at the equator. The pattern of Kinesin-6 localization closely resembles where new myosin filaments appear at the cortex by de novo assembly. While accumulating at the equator, myosin filaments disappear from the poles of the cell, a process that also requires Kinesin-6 as well as possibly other signals that emanate from the elongating spindle. These results suggest models for how Kinesin-6 might define the position of cortical myosin during cytokinesis.This work was supported by a National Institutes of Health grant NIH 38499 to R.D. Vale

Beware of fake AGNs

In the BPT diagram, the distribution of the emission-line galaxies from the Sloan Digital Sky Survey (SDSS) evokes the wings of a seagull. Traditionally, galaxies in the right wing are considered to host AGNs. Our study of the stellar populations of SDSS galaxies showed that about1/4 of galaxies thought to host LINERS are in fact "retired galaxies", i.e. galaxies that stopped forming stars and are ionized by hot post-AGB stars and white dwarfs (Stasinska et al. 2008). When including the galaxies that lack some of the lines needed to place them in the BPT diagram the fraction of retired galaxies is even larger (Cid Fernandes et al., 2009, arXiv:0912.1376)Comment: to be published in "Co-evolution of central black holes and galaxies: feeding and feed-back" Proceedings IAU Symposium No. 267, Peterson, Rachel Somerville, & Thaisa Storchi-Bergmann ed

BOND: Bayesian Oxygen and Nitrogen abundance Determinations in giant H II regions using strong and semi-strong lines

We present BOND, a Bayesian code to simultaneously derive oxygen and nitrogen abundances in giant H II regions. It compares observed emission lines to a grid of photoionization models without assuming any relation between O/H and N/O. Our grid spans a wide range in O/H, N/O and ionization parameter U, and covers different starburst ages and nebular geometries. Varying starburst ages accounts for variations in the ionizing radiation field hardness, which arise due to the ageing of H II regions or the stochastic sampling of the initial mass function. All previous approaches assume a strict relation between the ionizing field and metallicity. The other novelty is extracting information on the nebular physics from semi-strong emission lines. While strong lines ratios alone ([O III]/Hbeta, [O II]/Hbeta and [N II]/Hbeta) lead to multiple O/H solutions, the simultaneous use of [Ar III]/[Ne III] allows one to decide whether an H II region is of high or low metallicity. Adding He I/Hbeta pins down the hardness of the radiation field. We apply our method to H II regions and blue compact dwarf galaxies, and find that the resulting N/O vs O/H relation is as scattered as the one obtained from the temperature-based method. As in previous strong-line methods calibrated on photoionization models, the BOND O/H values are generally higher than temperature-based ones, which might indicate the presence of temperature fluctuations or kappa distributions in real nebulae, or a too soft ionizing radiation field in the models.Comment: MNRAS in press; 21 pages, 22 figures, 2 tables; code, data and results available at http://bond.ufsc.b

A comprehensive classification of galaxies in the SDSS: How to tell true from fake AGN?

We use the W_Ha versus [NII]/Ha (WHAN) diagram to provide a comprehensive emission-line classification of SDSS galaxies. This classification is able to cope with the large population of weak line galaxies that do not appear in traditional diagrams due to a lack of some of the diagnostic lines. A further advantage of the WHAN diagram is to allow the differentiation between two very distinct classes that overlap in the LINER region of traditional diagnostic diagrams. These are galaxies hosting a weakly active nucleus (wAGN) and "retired galaxies" (RGs), i.e. galaxies that have stopped forming stars and are ionized by their hot evolved low-mass stars. A useful criterion to distinguish true from fake AGN (i.e. the RGs) is the ratio (\xi) of the extinction-corrected L_Ha with respect to the Ha luminosity expected from photoionization by stellar populations older than 100 Myr. This ratio follows a markedly bimodal distribution, with a \xi >> 1 population composed by systems undergoing star-formation and/or nuclear activity, and a peak at \xi ~ 1 corresponding to the prediction of the RG model. We base our classification scheme on the equivalent width of Ha, an excellent observational proxy for \xi. Based on the bimodal distribution of W_Ha, we set the division between wAGN and RGs at W_Ha = 3 A. Five classes of galaxies are identified within the WHAN diagram: (a) Pure star forming galaxies: log [NII]/Ha 3 A. (b) Strong AGN (i.e., Seyferts): log [NII]/Ha > -0.4 and W_Ha > 6 A. (c) Weak AGN: log [NII]/Ha > -0.4 and W_Ha between 3 and 6 A. (d) RGs: W_Ha < 3 A. (e) Passive galaxies (actually, line-less galaxies): W_Ha and W_[NII] < 0.5 A. A comparative analysis of star formation histories and of other properties in these different classes of galaxies corroborates our proposed differentiation between RGs and weak AGN in the LINER-like family. (Abridged)Comment: Accepted for publication in MNRA

The many faces of LINER-like galaxies: a WISE view

We use the SDSS and WISE surveys to investigate the real nature of galaxies defined as LINERs in the BPT diagram. After establishing a mid-infrared colour W2-W3 = 2.5 as the optimal separator between galaxies with and without star formation, we investigate the loci of different galaxy classes in the W_{Ha} versus W2-W3 space. We find that: (1) A large fraction of LINER-like galaxies are emission-line retired galaxies, i.e galaxies which have stopped forming stars and are powered by hot low-mass evolved stars (HOLMES). Their W2-W3 colours show no sign of star formation and their Ha equivalent widths, W_{Ha}, are consistent with ionization by their old stellar populations. (2) Another important fraction have W2-W3 indicative of star formation. This includes objects located in the supposedly `pure AGN' zone of the BPT diagram. (3) A smaller fraction of LINER-like galaxies have no trace of star formation from W2-W3 and a high W_{Ha}, pointing to the presence of an AGN. (4) Finally, a few LINERs tagged as retired by their W_{Ha} but with W2-W3 values indicative of star formation are late-type galaxies whose SDSS spectra cover only the old `retired' bulge. This reinforces the view that LINER-like galaxies are a mixed bag of objects involving different physical phenomena and observational effects thrusted into the same locus of the BPT diagram.Comment: Accepted for publication in MNRAS; 9 pages, 6 figure

Control of lice on poultry

DURING February and March of 1965 some particularly heavy body lice infestations were found on fowls in both deep litter and cage units in Western Australia. In some instances comparatively new laying cage units were involved. The most seriously affected flocks showed marked unthriftiness and depressed egg production

Is policy leading to improved sustainability at the local urban scale?

In New Zealand, urban growth strategies and environmental policies at national and regional levels are influencing urban transformations at the local scale. Intensified residential and mixed use developments are emerging at growth nodes as outcomes of the Auckland Regional Growth Strategy 2050. The New Zealand Urban Design Protocol identified significant influences from government legislation, strategies and policies on urban design and the built forms at local level. The national walking and cycling strategy indicates that supportive local-scale layout and design in both existing and new developments could significantly influence travel behaviour. One of the six goals of the National Energy Efficiency and Conservation Strategy is to reduce local environmental effects of energy production and use. The Urban Form Design and Development (UFDD) work, part of the 'Auckland Sustainable Cities Programme' under the NZ Sustainable Development Programme of Action (NZSDPOA), focussed on policy mechanisms to drive sustainable urban form at the local scale in the Auckland Region. Using a case study-based approach, this paper investigates how national and regional policies influence the environmental sustainability of emerging local residential forms at this scale, especially in the Auckland Region. Three selected case studies are examined in terms of: applied urban design principles; design characteristics including street patterns, subdivision layouts and open space provisions; density of development; potential and actual renewable energy use and available transport options. A comparison of the New Zealand approach to sustainable urban forms with an international zero energy residential development is made. Results indicate the policies could influence emerging local-scale urban forms in varied manners generating significantly different contributions to environmental sustainability

Equilibrium Chemical Engines

An equilibrium reversible cycle with a certain engine to transduce the energy of any chemical reaction into mechanical energy is proposed. The efficiency for chemical energy transduction is also defined so as to be compared with Carnot efficiency. Relevance to the study of protein motors is discussed. KEYWORDS: Chemical thermodynamics, Engine, Efficiency, Molecular machine.Comment: 5 pages, late