2,897 research outputs found
The XMM-Newton Slew Survey: towards the XMMSL1 catalogue
The XMM-Newton satellite is the most sensitive X-ray observatory flown to
date due to the great collecting area of its mirrors coupled with the high
quantum efficiency of the EPIC detectors. It performs slewing manoeuvers
between observation targets tracking almost circular orbits through the
ecliptic poles due to the Sun constraint. Slews are made with the EPIC cameras
open and the other instruments closed, operating with the observing mode set to
the one of the previous pointed observation and the medium filter in place.
Slew observations from the EPIC-pn camera in FF, eFF and LW modes provide
data, resulting in a maximum of 15 seconds of on-source time. These data can be
used to give a uniform survey of the X-ray sky, at great sensitivity in the
hard band compared with other X-ray all-sky surveys.Comment: 2 pages, 2 figures, to appear in the proceedings of "The X-ray
Universe 2005", San Lorenzo de El Escorial (Spain), 26-30 September 200
The XMM-Newton Slew Survey
XMM-Newton, with the huge collecting area of its mirrors and the high quantum
efficiency of its EPIC detectors, is the most sensitive X-ray observatory ever
flown. This is strikingly evident during slew exposures, which, while yielding
only at most 14 seconds of on-source exposure time, actually constitute a 2-10
keV survey ten times deeper than all other "all-sky" surveys. The current
(April 2005) XMM archive contains 374 slew exposures which give a uniform
coverage over around 10,000 square degrees (approx. 25% of the sky). Here we
describe the results of pilot studies, the current status of the XMM-Newton
Slew Survey, up-to-date results and our progress towards constructing a
catalogue of slew detections in the full 0.2-12 keV energy band.Comment: 3 pages, 4 figures, XMM-Newton EPIC Consortium Meeting, Schloss
Ringberg, Germany, April 2005, to appear in MPE Repor
Extended sources in the XMM-Newton slew survey
The low background, good spatial resolution and great sensitivity of the
EPIC-pn camera on XMM-Newton give useful limits for the detection of extended
sources even during the short exposures made during slewing maneouvers. In this
paper we attempt to illustrate the potential of the XMM-Newton slew survey as a
tool for analysing flux-limited samples of clusters of galaxies and other
sources of spatially extended X-ray emission.Comment: 2 pages, 4 figures, to appear in the proceedings of "The X-ray
Universe 2005", San Lorenzo de El Escorial (Spain), 26-30 September 200
Efeito de espĂ©cies vegetais em bordadura em cebola sobre a densidade populacional de tripes e sirfĂdeos predadores.
Analisou-se a relação entre o efeito do plantio de diferentes espĂ©cies vegetais, em bordadura, na cultura da cebola, Allium cepa L, na incidĂŞncia de Thrips tabaci Lind. e sirfĂdeos predadores, Toxomerus spp. O experimento foi conduzido na Epagri, EE de Ituporanga, de agosto a dezembro de 1998. Os tratamentos foram cebola em monocultivo; cebola + trigo mourisco (Fagopyrum esculentum Moench); cebola + nabo forrageiro (Raphanus sativus L. var. oleiferus Metzg.); cebola + cenoura (Daucus carota L., cv. Nantes e cv. BrasĂlia); cebola + milho (Zea mays L.); cebola + rĂşcula
(Eruca sativa L.) + vegetação espontânea. O plantio de diferentes espĂ©cies vegetais em bordadura nĂŁo provocou diferenças significativas na incidĂŞncia de tripes e sirfĂdeos predadores. A produtividade comercial de bulbos de cebola foi similar em sistema de monocultivo e diversificado, sugerindo ser possĂvel adotar tais sistemas sem perdas em rendimento
Magnetic versus crystal field linear dichroism in NiO thin films
We have detected strong dichroism in the Ni x-ray absorption
spectra of monolayer NiO films. The dichroic signal appears to be very similar
to the magnetic linear dichroism observed for thicker antiferromagnetic NiO
films. A detailed experimental and theoretical analysis reveals, however, that
the dichroism is caused by crystal field effects in the monolayer films, which
is a non trivial effect because the high spin Ni ground state is not
split by low symmetry crystal fields. We present a practical experimental
method for identifying the independent magnetic and crystal field contributions
to the linear dichroic signal in spectra of NiO films with arbitrary
thicknesses and lattice strains. Our findings are also directly relevant for
high spin and systems such as LaFeO, FeO,
VO, LaCrO, CrO, and Mn manganate thin films
Optimizing the sample size to estimate growth in I-214 poplar plantations at definitive tree density for bioenergetic production
ArticleIn Europe, over the last decades, the arboriculture for woody biomass production has
significantly expanded, often using poplar plantations. In order to maximize prod
uction, the
flexibility of the cultivation algorithms becomes necessary. For this reason, it is necessary to
apply monitoring tools for the evaluation and estimate of the wood productions, without
significantly affect the production costs. In particular, f
or the estimate of the productions, the
choice of the sample size is of particular importance. The aim of this study was to verify a
simplified sampling approaches in poplar plantations characterized by constant tree density. The
research was conducted in
a poplar plantation on the Tuscan hills (Italy). The surveys were carried
out each year for 13 years, from 4 to 16 years old. Through different statistical techniques, the
change in the social position of each tree over time was evaluated. The results show
ed that the
social position of each tree has been characterized by the first years after the plantation.
Consequently, the estimate of the productions can be carried out by analysing the diameter
increment of 10% of the trees, included in the diameter clas
ses around the medium
-
sized tree at
the time of the survey. This study provided a valid method for forest managers characterized by
a simplified approach useful to estimate the growth and yield of hybrid poplars. This method will
permit reliable biomass es
timates, but also a reduction of the costs in the sampling activities in
the field
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