The birthplace and age of the isolated neutron star RX J1856.5-3754

X-ray observations unveiled various types of radio-silent Isolated Neutron Stars (INSs), phenomenologically very diverse, e.g. the Myr old X-ray Dim INS (XDINSs) and the kyr old magnetars. Although their phenomenology is much diverse, the similar periods (P=2--10 s) and magnetic fields (~10^{14} G) suggest that XDINSs are evolved magnetars, possibly born from similar populations of supermassive stars. One way to test this hypothesis is to identify their parental star clusters by extrapolating backward the neutron star velocity vector in the Galactic potential. By using the information on the age and space velocity of the XDINS RX J1856.5-3754, we computed backwards its orbit in the Galactic potential and searched for its parental stellar cluster by means of a closest approach criterion. We found a very likely association with the Upper Scorpius OB association, for a neutron star age of 0.42+/-0.08 Myr, a radial velocity V_r^NS =67+/- 13$ km s^{-1}, and a present-time parallactic distance d_\pi^NS = 123^{+11}_{-15} pc. Our result confirms that the "true" neutron star age is much lower than the spin-down age (tau_{sd}=3.8 Myrs), and is in good agreement with the cooling age, as computed within standard cooling scenarios. The mismatch between the spin-down and the dynamical/cooling age would require either an anomalously large breaking index (n~20) or a decaying magnetic field with initial value B_0 ~ 10^{14} G. Unfortunately, owing to the uncertainty on the age of the Upper Scorpius OB association and the masses of its members we cannot yet draw firm conclusions on the estimated mass of the RX J1856.5-3754 progenitor.Comment: 6 pages, accepted for publication on Monthly Notices of the Royal Astronomical Societ

Matrix-state particle filters for Wishart stochastic volatility processes

Abstract: This work deals with multivariate stochastic volatility models, which account for a time-varying variance-covariance structure of the observable variables. We focus on a special class of models recently proposed in the literature and assume that the covariance matrix is a latent variable which follows an autoregressive Wishart process. We review two alternative stochastic representations of the Wishart process and propose Markov-Switching Wishart processes to capture different regimes in the volatility level. We apply a full Bayesian inference approach, which relies upon Sequential Monte Carlo (SMC) for matrix-valued distributions and allows us to sequentially estimate both the parameters and the latent variables

Bayesian inference in dynamic models with latent factors

In time series analysis, latent factors are often introduced to model the heterogeneous time evolution of the observed process. The presence of unobserved components makes the maximum likelihood estimation method more difficult to apply. Thus a Bayesian approach is sometimes preferable since it allows to treat general state space models and makes easier the simulation based approach to parameters estimation and latent factors filtering. The paper examines economic time series models in a Bayesian perspective focusing, through some examples, on the extraction of the Business Cycle components like cycle and trend. We briefly review some general univariate and multivariate Bayesian dynamic models and discuss the simulation based techniques, such as Gibbs sampling, adaptive importance sampling and particle filter, useful for parameter estimation and latent factor extraction

Identification of snps associated with somatic cell score in candidate genes in italian holstein friesian bulls

Mastitis is an infectious disease affecting the mammary gland, leading to inflammatory reactions and to heavy economic losses due to milk production decrease. One possible way to tackle the antimicrobial resistance issue stemming from antimicrobial therapy is to select animals with a genetic resistance to this disease. Therefore, aim of this study was to analyze the genetic variability of the SNPs found in candidate genes related to mastitis resistance in Holstein Friesian bulls. Target regions were amplified, sequenced by Next-Generation Sequencing technology on the Illumina® MiSeq, and then analyzed to find correlation with mastitis related phenotypes in 95 Italian Holstein bulls chosen with the aid of a selective genotyping approach. On a total of 557 detected mutations, 61 showed different genotype distribution in the tails of the deregressed EBVs for SCS and 15 were identified as significantly associated with the phenotype using two different approaches. The significant SNPs were identified in intergenic or intronic regions of six genes, known to be key components in the immune system (namely CXCR1, DCK, NOD2, MBL2, MBL1 and M-SAA3.2). These SNPs could be considered as candidates for a future genetic selection for mastitis resistance, although further studies are required to assess their presence in other dairy cattle breeds and their possible negative correlation with other traits

Diagnostic pitfalls in the assessment of congenital hypopituitarism.

BACKGROUND: The diagnosis of congenital hypopituitarism is difficult and oftendelayed because its symptoms are nonspecific.AIM: To describe the different clinical presentations of children with congenitalhypopituitarism to reduce the time for diagnosis and to begin a precocious andappropriate treatment.STUDY DESIGN: We analyzed a cohort of five children with congenitalhypopituitarism, describing their clinical, biochemical and radiologicalcharacteristics from the birth to diagnosis.RESULTS: As first sign of the disease, all of five patients presented a neonatal hypoglycemia, associated in four cases with jaundice. In all these four cases,the clinicians hypothesized a metabolic disease delaying the diagnosis, which wasperformed in only two cases within the neonatal period. In the other three cases,the diagnosis was formulated at 2, 5 and 8 years of life because there was severeand precocious growth impairment.CONCLUSIONS: It is important to suspect congenital hypopituitarism in thepresence of persistent neonatal hypoglycemia associated with jaundice and of aprecocious and severe reduction of the growth velocity in childhood. In all thesecases, it is necessary to undertake a hypothalamic-pituitary magnetic resonanceimaging scan as soon as possible, and to start appropriate treatment