1,189 research outputs found

    Inventory of ponds in the Norfolk Coast AONB - recommendations for pond survey and conservation

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    The banning of tributyltin (TBT) from boat antifouling paints in the late 1980s led to its replacement by alternative biocide additives (Voulvoulis et al., 2000; Marcheselli et al., 2010), including Cu (Dahl & Blanck, 1996) and Zn as active ingredients. It has been reported that Cu and Zn compounds associated with these biocides have caused substantial contamination of harbour and marina sediments (Eklund et al., 2010; Parks et al., 2010), with negative toxic consequences for aquatic organisms (Ytreberg et al., 2010). Indeed, it is evident that Cu and Zn compounds present in paint fragments are readily leached into the water column allowing entry into aquatic food webs (Jessop & Turner, 2011). Nevertheless, relatively little is known regarding antifoulant-derived metals contamination in freshwater lakes. The Norfolk and Suffolk Broads (Eastern England, UK) have been contaminated by antifoulant-derived heavy metals, particularly Cu and Zn which have increased since the banning of TBT (post-1987) in parts of the boated system (Boyle et al., in prep.). Further, recent studies suggest that current levels of sediment contamination by Cu may have negative ecological effects for aquatic ecosystems including inhibition of aquatic macrophyte germination and performance (Boyle et al., submitted; S. Lambert, unpublished data). In Hickling Broad (Thurne Broads system), post-TBT increases in Cu and Zn are also evident, with an interesting peak in Cu for the late 1990s in core HICK1 (Figure 1). This coincides with the large-scale loss of aquatic macrophytes (especially Characeae) from the lake in 1999 (Barker et al., 2008). HICK1 was collected in 2003. In the proposed study we sought to gain a fuller understanding of recent metal contamination in Hickling Broad up to the present day, whilst looking to verify and better contextualise the late 1990s Cu peak. Further, we aimed to determine whether the peak in Cu for Hickling Broad was also recorded at Horsey Mere which is used as a control site in this study i.e. is it just a Hickling phenomenon? Or is it a Thurne Broads system-wide effect

    Analysis of sediment, fish and phytoplankton samples from Indawgyi Lake, Myanmar

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    Fauna and Flora International are coordinating a management plan for Indawgyi Lake (under consideration as a Ramsar and UNESCO World Heritage Site) in Myanmar. Part of this process will be to set-up monitoring protocols for the inflow/outflow streams and the lake. Potential impacts on the lake include artisanal gold mining in the in-flow streams, farming around the lake (mostly rice) and some waste inputs from villages. There are further concerns related to the introduction of invasive fish (Oreochromis niloticus – Nile tilapia) and plant (Eichhornia sp. ‘water hyacinth’) species. In 2015 the following samples were collected following advice from ENSIS: i) water samples to measure phosphate, nitrates and sulphates (and other N, P, and S species that may be appropriate)*; ii) river and lake sediments and biological material (fish biopsy from whole small fish or tissue from larger fish) to measure heavy metal concentrations (with key elements being mercury, arsenic, lead and copper). Fish samples were preserved in 100% ethanol. Samples were taken of sediment (in triplicate) from about 15 locations from tributary rivers and from the lake periphery (45 samples in total); iii) water column samples from Indawgyi Lake (10 cm below the surface) to measure algae abundance and algal species composition. Samples were preserved in Lugol's iodine, initially from 1 l of water but siphoned to about 150 ml final volume

    Taking Cooperative Decisions in Group-Based Wireless Sensor Networks

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    Several studies have demonstrated that communications are more efficient when cooperative group-based architectures are used in wireless sensor networks (WSN). This type of architecture allows increasing sensor nodes' lifetime by decreasing the number of messages in network. But, the main gap is to know how to take cooperative decisions in order to make the right communication. In this paper, we analyze the main aspects related to collaborative decisions in WSNs. A mathematical analysis will be presented in order to take the correct decision. Finally, the simulations will show the efficiency of the method used to make cooperative decisions in WSNs. © 2011 Springer-Verlag.García Pineda, M.; Lloret, J.; Sendra Compte, S.; Rodrigues, JJPC. (2011). Taking Cooperative Decisions in Group-Based Wireless Sensor Networks. En Lecture Notes in Computer Science. Springer Verlag (Germany). 61-65. doi:10.1007/978-3-642-23734-8_9S6165Garcia, M., Bri, D., Sendra, S., Lloret, J.: Practical Deployments of Wireless Sensor Networks: a Survey. Int. Journal on Advances in Networks and Services 3(3-4), 170–185 (2010)Lloret, J., Garcia, M., Tomas, J.: Improving Mobile and Ad-hoc Networks performance using Group-Based Topologies. In: Wireless Sensor and Actor Networks II. IFIP, vol. 264, pp. 209–220 (2008)Garcia, M., Lloret, J.: A Cooperative Group-Based Sensor Network for Environmental Monitoring. In: Luo, Y. (ed.) CDVE 2009. LNCS, vol. 5738, pp. 276–279. Springer, Heidelberg (2009)Garcia, M., Sendra, S., Lloret, J., Lacuesta, R.: Saving Energy with Cooperative Group-Based Wireless Sensor Networks. In: Luo, Y. (ed.) CDVE 2010. LNCS, vol. 6240, pp. 73–76. Springer, Heidelberg (2010)Parsa, S., Parand, F.-A.: Cooperative decision making in a knowledge grid environment. Future Generation Computer Systems 23, 932–938 (2007)Soubie, J.-L., Zaraté, P.: Distributed Decision Making: A Proposal of Support Through Cooperative Systems. J. Group Decisions and Negotiation 14(2), 147–158 (2005)Kraemer, K.L., King, J.L.: Computer-based systems for cooperative work and group decision making. ACM Computer Survey 20(2), 115–146 (1988)Kernan, J.B.: Choice Criteria, Decision Behavior, and Personality. Journal of Marketing Research 5(2), 155–164 (1968

    Reconciling Present Neutrino Puzzles: Sterile Neutrinos as Mirror Neutrinos

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    We suggest that recent neutrino puzzles that are the solar and atmospheric neutrino deficits as well as the possible neutrino oscillations reported by the LSND experiment and the possibility of massive neutrinos providing the hot component of the cosmological dark matter, can all be naturally explained by assuming existence of a mirror world described by an ``electroweak'' gauge symmetry [SU(2)×U(1)]′[SU(2)\times U(1)]', with the breaking scale larger by about factor of 30 than the scale of the standard SU(2)×U(1)SU(2)\times U(1) model. An interesting aspect of this model is that the sterile neutrinos arise from the hidden mirror sector of the theory and thus their lightness is more natural than in the usual neutrino mass scenarios. The needed pattern of the neutrino mass matrix in this model is obtained by assuming a conserved ZKM-type global lepton number Lˉ=Le+Lμ−Lτ\bar L=L_e+L_\mu-L_\tau, which is violated by Planck scale effects. One implication of our proposal is that bulk of the dark matter in the universe is a warm dark matter consisting of few KeV mass particles rather than the 100 GeV range particles of the currently popular cold dark matter scenarios.Comment: 10 pages, Latex, no figure

    The Age Of Globular Clusters In Light Of Hipparcos: Resolving the Age Problem?

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    We review five independent techniques which are used to set the distance scale to globular clusters, including subdwarf main sequence fitting utilizing the recent Hipparcos parallax catalogue. These data together all indicate that globular clusters are farther away than previously believed, implying a reduction in age estimates. This new distance scale estimate is combined with a detailed numerical Monte Carlo study designed to assess the uncertainty associated with the theoretical age-turnoff luminosity relationship in order to estimate both the absolute age and uncertainty in age of the oldest globular clusters. Our best estimate for the mean age of the oldest globular clusters is now 11.5±1.311.5\pm 1.3 Gyr, with a one-sided, 95% confidence level lower limit of 9.5 Gyr. This represents a systematic shift of over 2 σ\sigma compared to our earlier estimate, due completely to the new distance scale---which we emphasize is not just due to the Hipparcos data. This now provides a lower limit on the age of the universe which is consistent with either an open universe, or a flat, matter dominated universe (the latter requiring H_0 \le 67 \kmsmpc). Our new study also explicitly quantifies how remaining uncertainties in the distance scale and stellar evolution models translate into uncertainties in the derived globular cluster ages. Simple formulae are provided which can be used to update our age estimate as improved determinations for various quantities become available.Comment: 41 pages, including 10 eps figs, uses aaspp4.sty and flushrt.sty, submitted to Ap.J., revised to incorporate FULL Hipparcos catalogue dat

    Spin-Flavour Oscillations and Neutrinos from SN1987A

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    The neutrino signal from SN1987A is analysed with respect to spin-flavour oscillations between electron antineutrinos, νˉe\bar{\nu}_{e}, and muon neutrinos, νμ\nu_{\mu}, by means of a maximum likelihood analysis. Following Jegerlehner et al. best fit values for the total energy released in neutrinos, EtE_t, and the temperature of the electron antineutrino, TνˉeT_{\bar{\nu}_{e}}, for a range of mixing parameters and progenitor models are calculated. In particular the dependence of the inferred quantities on the metallicity of the supernova is investigated and the uncertainties involved in using the neutrino signal to determine the neutrino magnetic moment are pointed out.Comment: 14 pages, RevTeX, 4 figures, to appear in Physical Review
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