Differences in genetic structuring of populations of the Argentine hemorrhagic fever reservoir, the rodent Calomys musculinus, from endemic and non endemic zones

Chiappero, M.B., Piacenza, M.F., Gardenal, C.N., Calderón, G., Provensal, C., Polop, J.J

Is keV ion induced pattern formation on Si(001) caused by metal impurities?

We present ion beam erosion experiments performed in ultra high vacuum using a differentially pumped ion source and taking care that the ion beam hits the Si(001) sample only. Under these conditions no ion beam patterns form on Si for angles below 45 degrees with respect to the global surface normal using 2 keV Kr ions and fluences of 2 x 10^22 ions/m^2. In fact, the ion beam induces a smoothening of preformed patterns. Simultaneous sputter deposition of stainless steel in this angular range creates a variety of patterns, similar to those previously ascribed to clean ion beam induced destabilization of the surface profile. Only for grazing incidence with incident angles between 60 degrees and 83 degrees pronounced ion beam patterns form. It appears that the angular dependent stability of Si(001) against pattern formation under clean ion beam erosion conditions is related to the angular dependence of the sputtering yield, and not primarily to a curvature dependent yield as invoked frequently in continuum theory models.Comment: 15 pages, 7 figures. This is an author-created, un-copyedited version of an article published in Nanotechnology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

A community pattern of small rodents as a function of plant diveristy of field edges

Un agroecosistema, entendido como un verdadero paisaje, presenta componentes expuestos a diferentes tipos y niveles de disturbio, siendo los bordes de cultivo parches longitudinales con niveles medios de perturbación. Esta relativa estabilidad los constituye en hábitat de numerosas especies de pequeños roedores. En este estudio se examinó el principal patrón de ordenación de las especies del ensamble de roedores explicado por variables de la vegetación. Se realizaron ordenaciones RDA con el software R para tres estaciones del año con variables derivadas de la cobertura vegetal del borde y del tipo y estado fenológico de los cultivos vecinos. Las tres especies más abundantes: Calomys musculinus, C. venustus y Akodon azarae se diferenciaron de las demás en el espacio de ordenación de manera significativa en función de la vegetación del borde, en tanto que A. azarae y C. musculinus también se separaron con respecto a los cultivos. Las demás especies capturadas parecen no mostrar una afinidad evidente por las variables consideradas. En términos de selección y uso de hábitat en agroecosistemas los roedores reconocerían diferentes escalas: los tipos de cultivos y los componentes florísticos del borde

Environmental determinants of the small mammal assemblage in an agroecosystem of central Argentina: the role of Calomys musculinus

Agricultural intensification in the central region of Argentina has been accompanied by rodent assemblage changes, involving an increase in Calomys species densities. In particular, Calomys musculinus, the main reservoir of Junín virus (etiological agent of the Argentine Haemorrhagic Fever, AHF) selects field borders over crop-fields. Borders represent relatively-stable habitats within agroecosystems, otherwise highly human modified landscapes. In this article, we assessed the effect of environmental variables on rodent species occurrence and assemblage in the field borders of a pampean agroecosystem. Small rodent occurrence was examined for variation according to vegetation species composition, structure and productivity, using canonical ordination techniques. In a total of 72 crop-field borders of Córdoba province, in spring, summer and autumn (2005-2006), we captured 1041 rodents of 8 different species. Akodon azarae, Calomys venustus and C. musculinus were the dominant species of the assemblage, with the first two associated one another, while C. musculinus tended to be related to different environmental variables. We showed that rodent species associations were mediated by resources that changed seasonally, such as vegetation cover. Also, the strength and “sign” of the association between species seemed to be a consequence of different habitat preferences and activity patterns. Finally, the intra-annual population cycle seemed to influence the relation between species and habitat structure and, possibly, inter-specific competition for resources. Therefore, we suggest that less generalist species of the rodent assemblage, well adapted to linear habitats, may limit C. musculinus occurrence throughout the agroecosystem by habitat and spatial competition. Any action aimed to control AHF, and therefore C. musculinus population density, should exclude negative effects on coexisting species

Spatial difference in the incidence of Argentine Hemorrhagic Fever and composition and abundance of rodents in the assemblage

Fil: Piacenza, María F. Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba; Argentina.Fil: Calderón, Gladys E. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Enría, Delia. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Provensal, María C. Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba; Argentina.Fil: Polop, Jaime J. Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba; Argentina.The Argentine Hemorrhagic Fever (AHF) is a zoonotic disease endemic in a wide area of the humid pampa of Argentina. The etiologic agent is the Junin virus that is maintained in the wild by the rodent Calomys musculinus and transmitted to humans, mainly, through aerosols generated from secretions and excretions

Providing management options to control corn mouse (Calomys musculinus) reservoir populations using a cohort structured model

Fil: Piacenza, M. F. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires; Argentina.Fil: Gomez, M. D. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, ArgentinaFil: Simone, I. Grupo de Investigación en Ecología de Poblaciones, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Córdoba; Argentina.Fil: Lamfri, Mario. Instituto Gulich, Comisión Nacional de Actividades Espaciales, Centro Espacial Teófilo Tabanera, Falda del Cañete, Córdoba; Argentina.Fil: Scavuzzo, C. M. Instituto Gulich, Comisión Nacional de Actividades Espaciales, Centro Espacial Teófilo Tabanera, Falda del Cañete, Córdoba; Argentina.Fil: Calderón, Gladys. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Polop, Jaime J. Grupo de Investigación en Ecología de Poblaciones, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Córdoba; Argentina.We evaluate several management options for Calomys musculinus populations through the formulation and validation of a cohort structured model. Initially, a basic model was constructed and validated using field population data. Next, the model was altered to allow us to evaluate different management options. In general, basic model results were in agreement with field data, demonstrating that this model would be useful in describing aspects of corn mouse population dynamics. Restricting control measures to when mouse numbers reach high levels would be inadequate, because population numbers tend to increase in size after some years. In contrast, reducing vegetation cover in spring was more effective in reducing field population abundances. Despite some limitations, the model could be useful for evaluating the relationships between population dynamics and some biotic or physical environmental variables, and thus ensure more efficient use of resources in integrated pest management

Energy loss in medium-energy ion scattering: a combined theoretical and experimental study of the model system Y on Si(111)

The energy-loss spectrum associated with scattering of 100 keV H+ ions from Y atoms on Si(111) has been investigated both experimentally and theoretically. Measurements were made from Y overlayers, and from the Si(111)(1x1) two-dimensional silicide phase formed by Y on this surface, in various scattering geometries and with different surface preparations. Theoretical simulations were conducted based on calculations of the energy loss experienced in specific ion trajectories through the surface, using coupled-channel calculations to describe inner-shell ionization and excitation as a function of impact parameter. The experimental results indicate that additional broadening contributions arise from surface inhomogeneity and roughness, but for near-normal incident and outgoing trajectories the theory and experiment agree quite well. The calculations show that, even for the ideal two-dimensional silicide phase in which the Y atoms lie just below the surface, significant energy loss arises from interaction of the ions with surrounding Si atoms, leading to a complete loss of intensity at zero energy loss