819 research outputs found
A probabilistic approach to emission-line galaxy classification
We invoke a Gaussian mixture model (GMM) to jointly analyse two traditional
emission-line classification schemes of galaxy ionization sources: the
Baldwin-Phillips-Terlevich (BPT) and vs. [NII]/H
(WHAN) diagrams, using spectroscopic data from the Sloan Digital Sky Survey
Data Release 7 and SEAGal/STARLIGHT datasets. We apply a GMM to empirically
define classes of galaxies in a three-dimensional space spanned by the
[OIII]/H, [NII]/H, and EW(H), optical
parameters. The best-fit GMM based on several statistical criteria suggests a
solution around four Gaussian components (GCs), which are capable to explain up
to 97 per cent of the data variance. Using elements of information theory, we
compare each GC to their respective astronomical counterpart. GC1 and GC4 are
associated with star-forming galaxies, suggesting the need to define a new
starburst subgroup. GC2 is associated with BPT's Active Galaxy Nuclei (AGN)
class and WHAN's weak AGN class. GC3 is associated with BPT's composite class
and WHAN's strong AGN class. Conversely, there is no statistical evidence --
based on four GCs -- for the existence of a Seyfert/LINER dichotomy in our
sample. Notwithstanding, the inclusion of an additional GC5 unravels it. The
GC5 appears associated to the LINER and Passive galaxies on the BPT and WHAN
diagrams respectively. Subtleties aside, we demonstrate the potential of our
methodology to recover/unravel different objects inside the wilderness of
astronomical datasets, without lacking the ability to convey physically
interpretable results. The probabilistic classifications from the GMM analysis
are publicly available within the COINtoolbox
(https://cointoolbox.github.io/GMM\_Catalogue/).Comment: Accepted for publication in MNRA
DIAGNOSIS OF ENDOCRINE DISEASE: Steroid Hormone Analysis in Diagnosis and Treatment of DSD Position Paper of EU COST Action BM 1303 "DSDnet".
Disorders or differences in sex development (DSD) comprise a heterogeneous group of conditions with an atypical sex development. For optimal diagnosis highly specialized laboratory analyses are required across European countries. Working group 3 of EU COST (European Cooperation in Science and Technology) Action BM 1303 "DSDnet" "Harmonisation of Laboratory Assessment" has developed recommendations on laboratory assessment for DSD regarding the use of technologies and analytes to be investigated. This position paper on steroid hormone analysis in diagnosis and treatment of DSD was compiled by a group of specialists in DSD and/or hormonal analysis, either from participating European Countries or international partner countries. The topics discussed comprised analytical methods (immunoassay/mass spectrometry based methods), matrices (urine/serum/saliva) and harmonisation of laboratory tests. The following positions were agreed upon: Support of the appropriate use of immunoassay and mass spectrometry based methods for diagnosis and monitoring of DSD. Serum/plasma and urine are established matrices for analysis. Laboratories performing analyses for DSD need to operate within a quality framework and actively engage in harmonisation processes so that results and their interpretation are the same irrespective of the laboratory they are performed in. Participation in activities of peer comparison such as sample exchange or when available subscribing to a relevant external quality assurance program should be achieved. The ultimate aim of the guidelines is the implementation of clinical standards for diagnosis and appropriate treatment of DSD to achieve the best outcome for patients, no matter where patients are investigated or managed
Neutrino propagation in a random magnetic field
The active-sterile neutrino conversion probability is calculated for neutrino
propagating in a medium in the presence of random magnetic field fluctuations.
Necessary condition for the probability to be positive definite is obtained.
Using this necessary condition we put constraint on the neutrino magnetic
moment from active-sterile electron neutrino conversion in the early universe
hot plasma and in supernova.Comment: 11 page
The three dimensions of online child pornography offending
The internet has opened up opportunities for non-contact sex offending, such as the viewing of child pornography. This paper proposes a model for the classification of child pornography offenders as an aid for their assessment and treatment, deducted from empirical studies and existing
typologies for child pornography offenders. Different subgroups of child pornography offenders may be described according to three dimensions: (1) type of offending, (2) the motivation behind child pornography offending and (3) the situational and social engagement in the offending behaviour. Distinct pathways of child pornography offending can be identified, related to differing criminogenic
needs, severity of offending, and appropriate assessment and treatment strategies for the offenders
Kinematic parameters and membership probabilities of open clusters in the Bordeaux PM2000 catalogue
We derive lists of proper-motions and kinematic membership probabilities for
49 open clusters and possible open clusters in the zone of the Bordeaux PM2000
proper motion catalogue (). We test
different parametrisations of the proper motion and position distribution
functions and select the most successful one. In the light of those results, we
analyse some objects individually. The segregation between cluster and field
member stars, and the assignment of membership probabilities, is accomplished
by applying a new and fully automated method based on both parametrisations of
the proper motion and position distribution functions, and genetic algorithm
optimization heuristics associated with a derivative-based hill climbing
algorithm for the likelihood optimization. We present a catalogue comprising
kinematic parameters and associated membership probability lists for 49 open
clusters and possible open clusters in the Bordeaux PM2000 catalogue region. We
note that this is the first determination of proper motions for five open
clusters. We confirm the non-existence of two kinematic populations in the
region of 15 previously suspected non-existent objects.Comment: 14 pages, 6 figures, 4 tables. Accepted for publication in Astronomy
& Astrophysic
Fluctuations of water near extended hydrophobic and hydrophilic surfaces
We use molecular dynamics simulations of the SPC-E model of liquid water to
derive probability distributions for water density fluctuations in probe
volumes of different shapes and sizes, both in the bulk as well as near
hydrophobic and hydrophilic surfaces. To obtain our results, we introduce a
biased sampling of coarse-grained densities, which in turn biases the actual
solvent density. The technique is easily combined with molecular dynamics
integration algorithms. Our principal result is that the probability for
density fluctuations of water near a hydrophobic surface, with or without
surface-water attractions, is akin to density fluctuations at the water-vapor
interface. Specifically, the probability of density depletion near the surface
is significantly larger than that in bulk. In contrast, we find that the
statistics of water density fluctuations near a model hydrophilic surface are
similar to that in the bulk
Birth weight in different etiologies of disorders of sex development
Context: It is well established that boys are heavier than girls at birth. Although the cause of birth weight (BW) difference is unknown, it has been proposed that it could be generated from prenatal androgen action. Objective: The aim of the current study was to determine the BW of children with disorders of sex development (DSD) of different etiologies and to evaluate the effects of androgen action on BW. Methods: Data regarding diagnosis, BW, gestational age, karyotype, and concomitant conditions were collected from the InternationalDisorders of SexDevelopment (I-DSD) Registry (www.i-dsd).BWstandard deviation score was calculated according to gestational age. Cases were evaluated according to disorder classification in I-DSD (i.e., disorders of gonadal development, androgen excess, androgen synthesis, androgen action, nonspecific disorder of undermasculinization groups, and Leydig cell defect). Results: A total of 533 cases were available; 400 (75%) cases were 46,XY, and 133 (25%) cases were 46,XX. Eighty cases (15%) were born small for gestational age (SGA). Frequency of SGA was higher in the 46,XY group (17.8%) than in the 46,XX (6.7%) group (P = 0.001). Mean BW standard deviation scores of cases with androgen excess and androgen deficiency [in disorders of gonadal development, androgen synthesis, and Leydig cell defect groups and androgen receptor gene (AR)mutation-positive cases in disorders of androgen action groups]were similar to normal childrenwith the same karyotype. SGA birth frequency was higher in the AR mutation-negative cases in disorders of androgen action group and in the nonspecific disorders of the undermasculinization group. Conclusions: BWdimorphism is unlikely to be explained by fetal androgen action per se. 46,XY DSDs due to nonspecific disorders of undermasculinizationare more frequently associatedwithfetal growth restriction, SGA, and concomitant conditions
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