Primordial black hole constraints in cosmologies with early matter domination

Moduli fields, a natural prediction of any supergravity and superstring-inspired supersymmetry theory, may lead to a prolonged period of matter domination in the early Universe. This can be observationally viable provided the moduli decay early enough to avoid harming nucleosynthesis. If primordial black holes form, they would be expected to do so before or during this matter dominated era. We examine the extent to which the standard primordial black hole constraints are weakened in such a cosmology. Permitted mass fractions of black holes at formation are of order $10^{-8}$, rather than the usual $10^{-20}$ or so. If the black holes form from density perturbations with a power-law spectrum, its spectral index is limited to $n \lesssim 1.3$, rather than the $n \lesssim 1.25$ obtained in the standard cosmology.Comment: 7 pages RevTeX file with four figures incorporated (uses RevTeX and epsf). Also available by e-mailing ARL, or by WWW at http://star-www.maps.susx.ac.uk/papers/infcos_papers.htm

High-spin states with seniority v=4,4,6 in 119-126Sn

The 119-126Sn nuclei have been produced as fission fragments in two reactions induced by heavy ions: 12C+238U at 90 MeV bombarding energy, 18O+208Pb at 85 MeV. Their level schemes have been built from gamma rays detected using the Euroball array. High-spin states located above the long-lived isomeric states of the even- and odd-A 120-126Sn nuclei have been identified. Moreover isomeric states lying around 4.5 MeV have been established in 120,122,124,126Sn from the delayed coincidences between the fission fragment detector SAPhIR and the Euroball array. The states located above 3-MeV excitation energy are ascribed to several broken pairs of neutrons occupying the nu h11/2 orbit. The maximum value of angular momentum available in such a high-j shell, i.e. for mid-occupation and the breaking of the three neutron pairs, has been identified. This process is observed for the first time in spherical nuclei.Comment: 20 pages, 22 figures, 12 tables, accepted for publication in Physical Review

Uniform random generation of large acyclic digraphs

Directed acyclic graphs are the basic representation of the structure underlying Bayesian networks, which represent multivariate probability distributions. In many practical applications, such as the reverse engineering of gene regulatory networks, not only the estimation of model parameters but the reconstruction of the structure itself is of great interest. As well as for the assessment of different structure learning algorithms in simulation studies, a uniform sample from the space of directed acyclic graphs is required to evaluate the prevalence of certain structural features. Here we analyse how to sample acyclic digraphs uniformly at random through recursive enumeration, an approach previously thought too computationally involved. Based on complexity considerations, we discuss in particular how the enumeration directly provides an exact method, which avoids the convergence issues of the alternative Markov chain methods and is actually computationally much faster. The limiting behaviour of the distribution of acyclic digraphs then allows us to sample arbitrarily large graphs. Building on the ideas of recursive enumeration based sampling we also introduce a novel hybrid Markov chain with much faster convergence than current alternatives while still being easy to adapt to various restrictions. Finally we discuss how to include such restrictions in the combinatorial enumeration and the new hybrid Markov chain method for efficient uniform sampling of the corresponding graphs.Comment: 15 pages, 2 figures. To appear in Statistics and Computin

A climate of uncertainty: accounting for error in climate variables for species distribution models

1. Spatial climate variables are routinely used in species distribution models (SDMs) without accounting for the fact that they have been predicted with uncertainty, which can lead to biased estimates, erroneous inference and poor performances when predicting to new settings – for example under climate change scenarios. 2. We show how information on uncertainty associated with spatial climate variables can be obtained from climate data models. We then explain different types of uncertainty (i.e. classical and Berkson error) and use two statistical methods that incorporate uncertainty in climate variables into SDMs by means of (i) hierarchical modelling and (ii) simulation–extrapolation. 3. We used simulation to study the consequences of failure to account for measurement error. When uncertainty in explanatory variables was not accounted for, we found that coefficient estimates were biased and the SDM had a loss of statistical power. Further, this bias led to biased predictions when projecting change in distribution under climate change scenarios. The proposed errors-in-variables methods were less sensitive to these issues. 4. We also fit the proposed models to real data (presence/absence data on the Carolina wren, Thryothorus ludovicianus), as a function of temperature variables. 5. The proposed framework allows for many possible extensions and improvements to SDMs. If information on the uncertainty of spatial climate variables is available to researchers, we recommend the following: (i) first identify the type of uncertainty; (ii) consider whether any spatial autocorrelation or independence assumptions are required; and (iii) attempt to incorporate the uncertainty into the SDM through established statistical methods and their extensions.This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by John Wiley & Sons Ltd on behalf of the British Ecological Society. The published article can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%292041-210X.Keywords: Measurement error, Errors-in-variables, Hierarchical statistical models, Climate maps, SIMEX, Prediction error, PRIS

Disorder Induced Diffusive Transport In Ratchets

The effects of quenched disorder on the overdamped motion of a driven particle on a periodic, asymmetric potential is studied. While for the unperturbed potential the transport is due to a regular drift, the quenched disorder induces a significant additional chaotic ``diffusive'' motion. The spatio-temporal evolution of the statistical ensemble is well described by a Gaussian distribution, implying a chaotic transport in the presence of quenched disorder.Comment: 10 pages, 4 EPS figures; submitted to Phys. Rev. Letter

The complex TIE between macrophages and angiogenesis

Macrophages are primarily known as phagocytic immune cells, but they also play a role in diverse processes, such as morphogenesis, homeostasis and regeneration. In this review, we discuss the influence of macrophages on angiogenesis, the process of new blood vessel formation from the pre-existing vasculature. Macrophages play crucial roles at each step of the angiogenic cascade, starting from new blood vessel sprouting to the remodelling of the vascular plexus and vessel maturation. Macrophages form promising targets for both pro- and anti-angiogenic treatments. However, to target macrophages, we will first need to understand the mechanisms that control the functional plasticity of macrophages during each of the steps of the angiogenic cascade. Here, we review recent insights in this topic. Special attention will be given to the TIE2-expressing macrophage (TEM), which is a subtype of highly angiogenic macrophages that is able to influence angiogenesis via the angiopoietin-TIE pathway

Lectures on Gaussian approximations with Malliavin calculus

In a seminal paper of 2005, Nualart and Peccati discovered a surprising central limit theorem (called the "Fourth Moment Theorem" in the sequel) for sequences of multiple stochastic integrals of a fixed order: in this context, convergence in distribution to the standard normal law is equivalent to convergence of just the fourth moment. Shortly afterwards, Peccati and Tudor gave a multidimensional version of this characterization. Since the publication of these two beautiful papers, many improvements and developments on this theme have been considered. Among them is the work by Nualart and Ortiz-Latorre, giving a new proof only based on Malliavin calculus and the use of integration by parts on Wiener space. A second step is my joint paper "Stein's method on Wiener chaos" (written in collaboration with Peccati) in which, by bringing together Stein's method with Malliavin calculus, we have been able (among other things) to associate quantitative bounds to the Fourth Moment Theorem. It turns out that Stein's method and Malliavin calculus fit together admirably well. Their interaction has led to some remarkable new results involving central and non-central limit theorems for functionals of infinite-dimensional Gaussian fields. The current survey aims to introduce the main features of this recent theory. It originates from a series of lectures I delivered at the Coll\`ege de France between January and March 2012, within the framework of the annual prize of the Fondation des Sciences Math\'ematiques de Paris. It may be seen as a teaser for the book "Normal Approximations Using Malliavin Calculus: from Stein's Method to Universality" (jointly written with Peccati), in which the interested reader will find much more than in this short survey.Comment: 72 pages. To be published in the S\'eminaire de Probabilit\'es. Mild update: typos, referee comment

Observational Constraints on Chaplygin Quartessence: Background Results

We derive the constraints set by several experiments on the quartessence Chaplygin model (QCM). In this scenario, a single fluid component drives the Universe from a nonrelativistic matter-dominated phase to an accelerated expansion phase behaving, first, like dark matter and in a more recent epoch like dark energy. We consider current data from SNIa experiments, statistics of gravitational lensing, FR IIb radio galaxies, and x-ray gas mass fraction in galaxy clusters. We investigate the constraints from this data set on flat Chaplygin quartessence cosmologies. The observables considered here are dependent essentially on the background geometry, and not on the specific form of the QCM fluctuations. We obtain the confidence region on the two parameters of the model from a combined analysis of all the above tests. We find that the best-fit occurs close to the $\Lambda$CDM limit ($\alpha=0$). The standard Chaplygin quartessence ($\alpha=1$) is also allowed by the data, but only at the $\sim2\sigma$ level.Comment: Replaced to match the published version, references update

“We now have a patient and not a criminal” : An exploratory study of judges and lawyers’ views on suicide attempters and the law in Ghana

This study explored the views of judges and lawyers of the superior courts of Ghana on the law criminalizing attempted suicide. Qualitative data were collected from 12 experienced legal practitioners of the superior courts (five judges and seven lawyers) using a semi-structured interview schedule. Thematic analysis of the data yielded three main perspectives: In defence of the Law, Advocating a Repeal, and Pro-Health Orientation. Although exploratory, the findings of this study offer cues for stepping up suicide literacy and advocacy programmes toward either a repeal of the law or a reform