4,381 research outputs found
Breaking the color-reddening degeneracy in type Ia supernovae
A new method to study the intrinsic color and luminosity of type Ia
supernovae (SNe Ia) is presented. A metric space built using principal
component analysis (PCA) on spectral series SNe Ia between -12.5 and +17.5 days
from B maximum is used as a set of predictors. This metric space is built to be
insensitive to reddening. Hence, it does not predict the part of color excess
due to dust-extinction. At the same time, the rich variability of SN Ia spectra
is a good predictor of a large fraction of the intrinsic color variability.
Such metric space is a good predictor of the epoch when the maximum in the B-V
color curve is reached. Multivariate Partial Least Square (PLS) regression
predicts the intrinsic B band light-curve and the intrinsic B-V color curve up
to a month after maximum. This allows to study the relation between the light
curves of SNe Ia and their spectra. The total-to-selective extinction ratio RV
in the host-galaxy of SNe Ia is found, on average, to be consistent with
typical Milky-Way values. This analysis shows the importance of collecting
spectra to study SNe Ia, even with large sample publicly available. Future
automated surveys as LSST will provide a large number of light curves. The
analysis shows that observing accompaning spectra for a significative number of
SNe will be important even in the case of "normal" SNe Ia.Comment: 11 pages, 11 figure
On the available evidence for the temperature dependence of soil organic carbon
International audienceTwo recent papers by Knorr et al. (2005) and Fang et al. (2005) provide variations of model fitting conducted in the former study. Knorr et al. (2005) suggested that more recalcitrant fractions of soil organic carbon (SOC) could be more sensitive to temperature. Fang et al. (2005) argue that this is an implication of the choice of model used. Further, Reichstein et al. (2005) point out that the evidence for a stronger temperature sensitivity of recalcitrant soil carbon mainly rests on an analysis of data provided by KĂ€tterer et al. (1998) and argue for a different selection criterion to exclude short-term incubations. Here, we explain why the model used by Knorr et al. (2005) is the simplest multi-pool model that can fit the available data and is at the same time fully consistent with the concept of "pools", as opposed to some of the model formulations proposed by Fang et al. (2005). It is also pointed out that the criterion proposed by Reichstein et al. (2005) uses posterior information to determine inclusion of experimental data, a practice that should be avoided. We conclude that the original analysis of Knorr et al. (2005) as well as the one added by Fang et al. (2005) indicate that there is a serious possibility that recalcitrant SOC reacts more to temperature changes than labile SOC
Children's understandings of obesity, a thematic analysis
Childhood obesity is a major concern in todayâs society. Research suggests the inclusion of the views and understandings of a target group facilitates strategies that have better efficacy. The objective of this study was to explore the concepts and themes that make up childrenâs understandings of the causes and consequences of obesity. Participants were selected from Reception (4-5 years old) and Year 6 (10-11 years old), and attended a school in an area of Sunderland, in North East England. Participants were separated according to age and gender, resulting in four focus groups, run across two sessions. A thematic analysis (Braun & Clarke, 2006) identified overarching themes evident across all groups, suggesting the key concepts that contribute to childrenâs understandings of obesity are ââKnowledge through Education,ââ ââRole Models,ââ ââFat is Bad,ââ and ââMixed Messages.ââ The implications of these findings and considerations of the methodology are discussed in full
Corrigendum to "The influence of vegetation, fire spread and fire behaviour on biomass burning and trace gas emissions: results from a process-based model" published in Biogeosciences, 7, 1991-2011, doi:10.5194/bg-7-1991-2010, 2010
No abstract available
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