Switching model with two habitats and a predator involving group defence

Switching model with one predator and two prey species is considered. The prey species have the ability of group defence. Therefore, the predator will be attracted towards that habitat where prey are less in number. The stability analysis is carried out for two equilibrium values. The theoretical results are compared with the numerical results for a set of values. The Hopf bifuracation analysis is done to support the stability results

Polarization transfer in the 4^{4}He(e⃗,e′p⃗3(\vec{e},e' \vec{p}^{3}H reaction

Polarization transfer in the 4He(e,e'p)3H reaction at a Q^2 of 0.4 (GeV/c)^2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark-meson coupling model.Comment: 5 pages, Latex, 2 postscript figures, submitted to Physics Letters

The influence of below-ground herbivory and defoliation of a legume on nitrogen transfer to neighbouring plants

1. Both foliar and root herbivory can alter the exudation of carbon from plant roots, which in turn can affect nitrogen availability in the soil. However, few studies have investigated the effects of herbivory on N fluxes from roots, which can directly increase N availability in the soil and uptake by neighbouring plants. Moreover, the combined effects of foliar and root herbivory on N fluxes remains unexplored. 2. We subjected the legume white clover (Trifolium repens L.) to defoliation (through clipping) and root herbivory (by an obligate root-feeding nematode, Heterodera trifolii Goggart) to examine how these stresses individually, and simultaneously, affected the transfer of T. repens-derived N to neighbouring perennial ryegrass (Lolium perenne L.) plants using 15N stable-isotope techniques. We also examined the effects of defoliation and root herbivory on the size of the soil microbial community and the growth response of L. perenne. 3. Neither defoliation nor root herbivory negatively affected T. repens biomass. On the contrary, defoliation increased root biomass (34%) and total shoot production by T. repens (100%). Furthermore, defoliation resulted in a fivefold increase in T. repens-derived 15N recovered in L. perenne roots, and increased the size of the soil microbial biomass (77%). In contrast, root herbivory by H. trifolii slightly reduced 15N transfer from T. repens to L. perenne when T. repens root 15N concentration was included as a covariate, and root herbivory did not affect microbial biomass. Growth of L. perenne was not affected by any of the treatments. 4. Our findings demonstrate that defoliation of a common grassland legume can substantially increase the transfer of its N to neighbouring plants by directly affecting below-ground N fluxes. These finding require further examination under field conditions but, given the prevalence of N-limitation of plant productivity in terrestrial ecosystems, increased transfer of N from legumes to non-N-fixing species could alter competitive interactions, with implications for plant community structure

1.76 Ga Volcano-plutonism In The Southwestern Amazonian Craton, Aripuanã-mt, Brazil: Tectono-stratigraphic Implications From Shrimp U-pb Zircon Data And Rock Geochemistry

Paleoproterozoic felsic and mafic volcanic rocks, extrusive and hypabyssal quartz porphyry, and high-K, A-type epizonal granites dominate the Aripuanã region in the southwestern Amazonian craton in the Mato Grosso state of Brazil. The extrusive and intrusive felsic rocks display similar major and trace elements abundance's and equivalent SHRIMP U-Pb ages of 1762-1755 Ma; contacts between them in the field occur gradually. The felsic volcanic activity occurred predominantly as explosive subaqueous volcanism. Various features such as absence of plate collision evidences, lack of any sign of oceanic crust, lack of complete trends of magmatic differentiation, and bimodal characteristics suggest that the magmatism was intracratonic. The characteristically undeformed felsic igneous rocks were formed by extensional events, probably triggered by mantle activation in an intracratonic 'anorogenic' or post-collisional environment. Throughout the Amazonian craton there are wide areas displaying similar magmatism responsible for the generation of distinctive A-type granites. These A-type granites and associated volcanic rocks yield ages of ∼ 1.76 Ga, suggesting that they are genetically linked and that there was a unique tectonic mechanism of widespread action in this craton. © 2002 Elsevier Science B.V. All rights reserved.1191-4171187Almeida, F.F.M., Evolução tectônica do cráton do guaporé comparada com o escudo báltico (1974) Rev. Brasil Geoci., 4, pp. 191-204Compston, W., Williams, I.S., Meyer, C., U-Pb geochronology of zircons from lunar breccia 73217 using a sensitive high mass-resolution ion microprobe (1984) J. Geophys. Res., 89, pp. 525-534Costa, J.B.S., Hasui, Y., Evolução geológica da Amazônia (1997) Sociedade Brasileira de Geologia, pp. 15-90. , Costa, M.L., Angélica, R.S. (Eds.), Contribuiçõs à Geologia da Amazônia (in Portuguese)Dall'Agnol, R., Lafon, J.M., Macambira, M.J.B., Proterozoic anorogenic magmatism in the Central Amazonian Province, Amazonian Craton: Geochronological, petrological and geochemical aspects (1994) Mineral. Petrol., 50, pp. 113-138De Laeter, J.R., Kennedy, A.K., A double focusing mass spectometer for geochronology (1998) Int. J. Mass Spect., 178, pp. 43-50Eby, G.N., The A-type granitoids: A review of their occurrence and chemical characteristics and speculations on their petrogenesis (1990) Lithos, 26, pp. 115-134Geraldes, M.C., Teixeira, W., Van Schmus, W.R., Isotopic and chemical evidence for three accretionary magmatic arcs ( 1.79-1.42 Ga) in the SW Amazon Craton, Mato Grosso State (2000) Brazil. Rev. Brasil. Geoci., 30 (1), pp. 99-101Irvine, T.R., Baragar, W.R.A., A guide to the chemical classification of the common volcanic rocks (1971) Can. J. Earth Sci., 8, pp. 523-548Karlstrom, K.E., Harlan, S.H., Williams, M.L., McLelland, J., Geissman, J.W., Ahäll, K.I., Refining rodinia: Geologic evidence for the Australia - Western US connection in the proterozoic (1999) GSA Today, 9 (10), pp. 4-7Keavey, P., Vine, F.J., (1994) Global Tectonics, , Blackwell, OxfordLe Maitre, R.W., Bateman, P., Dudek, A., Keller, J., Lamiere, J., Le Bas, M.J., Sabine, P.A., Zanettin, B., (1989) A Classification of Igneous Rocks and Glossary of Terms, , Blackwell, OxfordManiar, P.D., Picolli, P.M., Tectonic discrimination granitoids (1989) Geol. Soc. Am. Bull., 101, pp. 635-643Miyashiro, A., Volcanic rock series in volcanic arcs and active continental margins (1974) Am. J. Sci., 274, pp. 321-355Montalvão, R.M.G., Bezerra, P.E.L., Drago, V.A., Cunha, B.C.C., Cobertura de plataforma da amazônia sua sedimentação e evolução tectônica (1984) Anais do XXXIII Congresso Brasileiro de Geologia, pp. 2101-2123. , Rio de Janeiro, in PortugueseNeder, R.D.N., Figueiredo, B.R., Beaudry, C., Collins, C., Leite, J.A.D., The expedito massive sulfide deposit (2000) Mato Grosso. Rev. Brasil. Geoci., 30 (2), pp. 222-225Nuttmann, A., Kinny, P.D., Compston, W., Williams, I.S., Shrimp U-Pb zircon geochronology of the Narrier Gneiss Complex, Western Australia (1991) Precambrian Res., 52, pp. 275-300Pearce, J.A., Trace element characteristics of lavas from destructive plate margins (1982) Andesites, Orogenic Andesites and Related Rocks, pp. 525-548. , Thorpe, R.S. (Ed.), Wiley, ChichesterPearce, J.A., Cann, J.R., Tectonic setting of mafic volcanic rocks determined using trace element analyses (1973) Earth Planet Sci. Lett., 19, pp. 290-300Pearce, J.A., Harris, N.B.W., Tindle, A.G., Trace element discrimination diagrams for the tectonic interpretation of granitic rocks (1984) J. Petrol., 25, pp. 956-983Pinho, M.A.S.B., Lima, E.F., Chemale F., Jr., (1999) Geologia da Região do Moriru-Dados Preliminares da Formação Iriri-Aripuanã-Mato Grosso. Boletim de Resumos, p. 14. , Programa VII Simpósio de Geologia do Centro-Oeste e X Simpósio de geologia de Minas Gerais, Brasília, in PortuguesePinho, M.S.A.B., Pinho, F.E.C., Quadros, A.P., Chemale F., Jr., (2001) Discussao do Termo Uatumã-Iriri, Região Norte do Estado de Mato Grosso-Brasil. Resumos Expandidos - VII Simpósio de Geologia da Amazônia, pp. 15-18. , Sociedade Brasileira de Geologia, Belém, in PortugueseSantos, J.O.S., (2000) Os Terrenos Paleoproterozóicos da Provincia Tapajós e as Mineralizações de Ouro Associadas, , Ph.D. thesis, Univ. Federal do Rio Grande do Sul, Brazil, in PortugueseSchobbenhaus, C., Hoppe, A., Lorke, A., Baumann, A., (1994) Idade U/Pb do Magmatismo Uatumã no Norte do Cráton Amazônico. Escudo das Guianas (Brasil): Primeiros Resultados, 2, pp. 395-397. , Sociedade Brasileira de Geologia, XXXVIII Congresso Brasileira de Geologia Ext. Abstr., in PortugueseSilva, H.A., Leal, J.W.L., Montalvão, R.M.G., Bezerra, P.E.L., Pimenta, O.N.S., Tassinari, C.C.G., Fernandes, C.A.C., Geologia (1980) Projecto RADAM-BRASIL, pp. 21-116. , Folha SC-21 Juruena, DNPM/MME, Rio de Janeiro, in PortugueseSmith, J.B., Barley, M.E., Groves, D.I., Krapez, B., McNaughton, N.J., Bickle, M.J., Chapman, H.J., The Scholl shear zone, West Pilbara: Evidence for a terrane boundary structure from integrated tectonic analyses, SHRIMP U/Pb dating and isotopic and geochemical data of granitoids (1998) Precambrian Res., 88, pp. 143-171Tassinari, C.C.G., (1981) Evolução Tectônica da Província Rio Negro-Juruena na Região Amazônica, , Dissertação de MSc. Univ. São Paulo, Brazil (in Portuguese)Tassinari, C.C.G., (1996) O Mapa Geocronológico do Cráton Amazônico no Brasil: Revisão dos dados Isotópicos, , Tese de livre Docência, Univ. São Paulo, Brazil, (in Portuguese)Tassinari, C.C.G., Macambira, M.J.B., Geochronological provinces of the Amazonian Craton (1999) Episodes, 22 (3), pp. 174-181Tassinari, C.C.G., Cordani, U.G., Nutman, P., Van Schmus, W.R., Bettencourt, J.S., Taylor, P.N., Geochronological systematics on basement rocks from the Rio Negro-Juruena Province (Amazonian Craton) and tectonic implications (1996) Int. Geol. Rev., 38, pp. 161-175Trompette, R., Carozi, A.C., (1994) Geology of Western Gondwana, , A.A. Balkema, RotterdamVavra, G., Systematics of internal zircon morphology in major Variscan granitoid types (1994) Contrib. Mineral. Petrol., 117, pp. 331-344Vasquez, M.L., Klein, E.L., Quadros, M.L.E., Bahia, R.B.C., Santos, A., Ricci, P., Sachett, C.R., Macambira, M.J.B., Magmatismo uatumã na província tapajós - Novos dados geocronológicos. VI Simpósio de Geologia da Amazônia (1999) Ext. Abstr. Bull., pp. 471-474. , in PortugueseVasquez, M.L., Klein, E.L., Ricci, P.S.F., Granitóides pós-colisionais da porção leste da província tapajós. VII Simpósio de Geologia da Amazônia (2001) Ext. Abstr. Bull., pp. 46-54. , in PortugueseWinchester, J.A., Floyd, P.A., Geochemical discrimination of different magma series and their differentiation products using imobile elements (1977) Chem. Geol., 20, pp. 325-34

Polarimeter for protons between 300 and 800 MeV

A polarimeter for protons between 300 and 800 MeV has been constructed. It uses a carbon block analyzer of variable thickness and 6 drift chambers for particle tracking