431 research outputs found
Mononchid nematodes from Spain : Iotonchus parageminus sp. n. and its relationships with I. geminus Heyns and Lagerwey, 1965 and I. rinae Coetzee, 1967
#Iotonchus parageminus et le #ductus ejaculatorius ayant l'aspect d'une large bande circulaire, la région ventrale du mâle non constrictée au niveau du commencement de la ligne des suppléments, des glandes éjaculatrices disposées en tandem, des spicules longs de 53-67 um, des pièces-guides à extrémités fourchues, 9 à 13 suppléments ventro-médians, une queue conique à extrémité arrondie et filières à ouverture subterminale. Des analyses univariées et en composantes principales basées sur les données morphométriques des femelles et des mâles ont été utilisées pour tester les différences expliquant la séparation de #I. parageminus sp. n. d'avec les espèces les plus proches. (Résumé d'auteur
Relationships between algal food and gut and gonad conditions in the Mediterranean sea urchin Paracentrotus lividus (Lam.)
A study was conducted on the population of Paracentrotus lividus (Lamarck, 1816) in a Mediterranean infralittoral bottomof southern of Spain to characterize the relationships between the macroalgal food ingested and the gut and gonad conditions of individuals. Over a full annual cycle (November 2008 to October 2009) composition of the gut content was analyzed monthly and seasonally, the gastrointestinal (GII), repletion (RI) and gonadosomatic (gonad) (GI) indices were calculated, and the stage of gonad maturity of the population was assessed. The GII and RI were found to be strongly correlated, so only the RI was considered in the subsequent analysis. The prevalence of Phaeophyceae and local species of this macroalgal group in the gut content of the sea urchins throughout the year suggests that in conditions of abundant resources, with high levels of algal diversity and no effective limits on supply, brown algae are the main component of the natural diet of P. lividus. Comparison of the physiologicalindices and the algal fractions of gut content identified relationships throughout the year between RI, the stage of gonad maturity and GI. Specifically, these indices were found to be associated with the abundance of Rhodophyta ingested, although in different ways: GI was related to the consumption of fleshy (non-calcified) red algae and the RI, though less statistically significantly, to the consumption of calcified (articulate and encrusting)
Mononchid nematodes from Spain : six known species and Miconchus baeticus sp. n. occurring in southern fir forests
Cet article traite de nématodes Mononchides présents dans les forêts de sapins (#Abies pinsapo Boiss.) d'Espagne méridionale et donne la description et l'illustration d'une nouvelle espèces, #Miconchus baeticus sp. n., collectée dans une zone naturelle protégée (Sierra de las Nieves). #M. baeticus, #Coomansus parvus, #Prionchulus muscorum, #Mylonchulus brachyuris, #Anatonchus ginglymodontus et #Miconchus studeri$ sont également signalés. (Résumé d'auteur
A Method to Determine the In-Air Spatial Spread of Clinical Electron Beams
We propose and analyze in detail a method to measure the in-air spatial
spread parameter of clinical electron beams. Measurements are performed at the
center of the beam and below the adjustable collimators sited in asymmetrical
configuration in order to avoid the distortions due to the presence of the
applicator. The main advantage of our procedure lies in the fact that the dose
profiles are fitted by means of a function which includes, additionally to the
Gaussian step usually considered, a background which takes care of the dose
produced by different mechanisms that the Gaussian model does not account for.
As a result, the spatial spread is obtained directly from the fitting procedure
and the accuracy permits a good determination of the angular spread. The way
the analysis is done is alternative to that followed by the usual methods based
on the evaluation of the penumbra width. Besides, the spatial spread found
shows the quadratic-cubic dependence with the distance to the source predicted
by the Fermi-Eyges theory. However, the corresponding values obtained for the
scattering power are differing from those quoted by ICRU nr. 35 by a factor ~2
or larger, what requires of a more detailed investigation.Comment: 11 pages, 5 Postscript figures, to be published in Medical Physic
Searching for low mass objects around nearby dMe radio stars
Nearby M-dwarfs are best suited for searches of low mass companions. VLBI
phase-referencing observations with sensitive telescopes are able to detect
radio star flux-densities of tenths of mJy as well as to position the star on
the sky with submilliarcsecond precision. We have initiated a long-term
observational program, using EVN telescopes in combination with NASA DSN
dishes, to revisit the kinematics of nearby, single M dwarfs. The precision of
the astrometry allows us to search for possible companions with masses down to
1 Jupiter mass. In this contribution we report preliminary results of the first
observation epochs, in which we could detect some of the radio stars included
in our program.Comment: Proceedings of the 6th European VLBI Network Symposium, Ros E.,
Porcas R.W., Lobanov A.P., & Zensus J.A. (eds.), MPIfR, Bonn, Germany, p.
255-258 (2002). 4 pages, 3 figures, needs evn2002.cl
Experimental phase functions of mm-sized cosmic dust grains
We present experimental phase functions of three types of millimeter-sized
dust grains consisting of enstatite, quartz and volcanic material from Mount
Etna, respectively. The three grains present similar sizes but different
absorbing properties. The measurements are performed at 527 nm covering the
scattering angle range from 3 to 170 degrees. The measured phase functions show
two well defined regions i) soft forward peaks and ii) a continuous increase
with the scattering angle at side- and back-scattering regions. This behavior
at side- and back-scattering regions are in agreement with the observed phase
functions for the Fomalhaut and HR 4796A dust rings. Further computations and
measurements (including polarization) for millimeter sized-grains are needed to
draw some conclusions about the fluffy or compact structure of the dust grains
The occurrence and distribution of Xiphinema species (Nematoda : Dorylaimida) in spanish fir woodlands
Une étude comparative a été réalisée en vue de définir l'influence des facteurs édaphiques sur la présence et l'abondance relative de quatre espèces de #Xiphinema observées dans le sol de cinq forêts de sapin (#Abies pinsapo Boiss) du sud de l'Espagne. Les prélèvements ont été effectués de façon saisonnière pendant une année. Afin de relier la présence des espèces avec les caractéristiques de l'habitat et mettre en évidence leur mode de répartition dans les aires étudiées, les méthodes d'analyses univariées (analyse linéaire de la variance) et multivariées (analyses en grappe et de correspondance) ont été utilisées. La répartition de trois des espèces s'est révélée correspondre aux gradients de texture du sol. #X. sphaerocephalum montre ses plus grandes fréquence et abondance relative dans les sols à roche-mère calcaire, mais n'a pas été trouvé sur les péridotites, c'est-à-dire dans des sols plus sableux, préférant les textures plutôt limoneuses. #X. pachtaicum est rencontré dans les sols à texture argileuse plus nettement soumis aux conditions climatiques méditerranéennes. La répartition de #X. diversicaudatum est très nettement liée aux sols acides de texture plus sableuse avec un taux élevé d'argile fine. #X. turcicum, enfin, n'est rencontré que très rarement et en faible nombre, aussi sa répartition dans ces sols demeure-t-elle obscure. (Résumé d'auteur
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