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DW Cancri in X-rays
No full textWe report on the XMM-Newton observation of DW Cnc, a candidate intermediate polar candidate whose historical optical light curve shows the existence of periods at ≃38, ≃86, and ≃69 min, which were interpreted as the white dwarf spin, the orbital and the spin-orbit beat periodicities. By studying the 0.3-10 keV light curves, we confirm the existence of a period at ≃ 38 min and find in the OM light curve a signature for a period at 75 ± 21 min, which is consistent with both the orbital and spin-orbit beat. These findings allow us to unveil without any doubt, the nature of DW Cnc as an accreting intermediate polar. The EPIC and RGS source spectra were analysed and a best-fitting model, consisting of a multitemperature plasma, was found. The maximum temperature found when fitting the data is kTmax ≃ 31 keV, which can be interpreted as an upper limit to the temperature of the shock
Infrared spectroscopy of carbonate samples of biotic origin relevant to Mars exobiological studies
No full textBecause it is possible that Mars experienced an ancient climate warmer and wetter than the present one, it is reasonable to suppose that simple
forms of life developed there, in the underground or at the surface, as in the terrestrial primitive biosphere. In this work we have performed
infrared (IR) transmission spectroscopic analyses directed to examine the reaction to heat treatments of biotic (fresh and fossil materials) and
abiotic particulate samples composed of calcium carbonate (aragonite or calcite). The aim is to check if IR spectroscopy can be a useful tool for
discriminating between abiotic and biotic (fossil) carbonate samples collected on the martian surface, during in situ or sample-return missions.
An important result we found is that, after thermal processing, it is possible to distinguish, by means of IR spectroscopy, abiotic aragonite from
aragonite of recent biological origin. In addition we have found that the spectral behaviour of all the analysed fossil samples after heat treatment
is the same as that of fresh biotic material irrespective of the original structure (whether aragonite or calcite)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A comparative study of biotic and abiotic minerals in the context of the research of life on Mars
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