Dirichlet process mixtures under affine transformations of the data

Location-scale Dirichlet process mixtures of Gaussians (DPM-G) have proved extremely useful in dealing with density estimation and clustering problems in a wide range of domains. Motivated by an astronomical application, in this work we address the robustness of DPM-G models to affine transformations of the data, a natural requirement for any sensible statistical method for density estimation and clustering. First, we devise a coherent prior specification of the model which makes posterior inference invariant with respect to affine transformations of the data. Second, we formalise the notion of asymptotic robustness under data transformation and show that mild assumptions on the true data generating process are sufficient to ensure that DPM-G models feature such a property. Our investigation is supported by an extensive simulation study and illustrated by the analysis of an astronomical dataset consisting of physical measurements of stars in the field of the globular cluster NGC 2419.Comment: 36 pages, 7 Figure

Focal Myositis in paediatric age.

BACKGROUND: Focal Myositis is a rare pseudotumor of unknown aetiology that is often difficult to diagnose and treat. Typically afflicting people in adulthood, it has occasionally been reported also among children. PURPOSE: the aim of this study is to review the literature of Focal Myositis in paediatric age in order to compare the clinical manifestation and the various treatment suggested by different authors. METHODS: this article describes a 6-year-old boy with focal myositis in gracilis muscle successfully treated by conservative methods, including nocturnal leg traction, intensive physiokinesi therapy and articulated knee orthosis guided to progressive extension. Furthermore a systematic review of literature concerning focal myositis in paediatric age is reported. CONCLUSION: our case and the review of literature suggests that conservative methods should be the first-choice treatment for FM in paediatric age and that surgery should be strictly reserved for selected cases where non-invasive methods have previously faile

Who invests in home equity to exempt wealth from bankruptcy? : [This draft: May 2013]

Homestead exemptions to personal bankruptcy allow households to retain their home equity up to a limit determined at the state level. Households that may experience bankruptcy thus have an incentive to bias their portfolios towards home equity. Using US household data for the period 1996 to 2006, we find that household demand for real estate is relatively high if the marginal investment in home equity is covered by the exemption. The home equity bias is more pronounced for younger households that face more financial uncertainty and therefore have a higher ex ante probability of bankruptcy

Who Invests in Home Equity to Exempt Wealth from Bankruptcy?

Homestead exemptions to personal bankruptcy allow households to retain their home equity up to a limit determined at the state level. Households that may experience bankruptcy thus have an incentive to bias their portfolios towards home equity. Using US household data from the Survey of Income and Program Participation for the period 1996-2006, we find that especially households with low net worth maintain a larger share of their wealth as home equity if a larger homestead exemption applies. This home equity bias is also more pronounced if the household head is in poor health, increasing the chance of bankruptcy on account of unpaid medical bills. The bias is further stronger for households with mortgage finance, shorter house tenures, and younger household heads, which taken together reflect households that face more financial uncertainty.Homestead exemptions;Personal bankruptcy;Portfolio allocation;Home ownership

Who invests in home equity to exempt wealth from bankruptcy?

Homestead exemptions to personal bankruptcy allow households to retain their home equity up to a limit determined at the state level. Households that may experience bankruptcy thus have an incentive to bias their portfolios towards home equity. Using US household data from the Survey of Income and Program Participation for the period 1996-2006, we find that especially households with low net worth maintain a larger share of their wealth as home equity if a larger homestead exemption applies. This home equity bias is also more pronounced if the household head is in poor health, increasing the chance of bankruptcy on account of unpaid medical bills. The bias is further stronger for households with mortgage finance, shorter house tenures, and younger household heads, which taken together reflect households that face more financial uncertainty. JEL Classification: G11, K35, R21Home ownership, Homestead exemptions, Personal bankruptcy, portfolio allocation

Priming of CD8 + T Cell Responses to Liver Stage Malaria Parasite Antigens

While the role of malaria parasite-specific memory CD8(+) T cells in the control of exo-erythrocytic stages of malaria infection is well documented and generally accepted, a debate is still ongoing regarding both the identity of the anatomic site where the activation of naive pathogen-specific T cells is taking place and contribution of different antigen-presenting cells (APCs) into this process. Whereas some studies infer a role of professional APCs present in the lymph nodes draining the site of parasite injection by the mosquito, others argue in favor of the liver as a primary organ and hepatocytes as stimulators of naïve parasite-specific T cell responses. This review aims to critically analyze the current knowledge and outline new lines of research necessary to understand the induction of protective cellular immunity against the malaria parasite

BNPmix: An R Package for Bayesian Nonparametric Modeling via Pitman-Yor Mixtures

BNPmix is an R package for Bayesian nonparametric multivariate density estimation, clustering, and regression, using Pitman-Yor mixture models, a flexible and robust generalization of the popular class of Dirichlet process mixture models. A variety of model specifications and state-of-the-art posterior samplers are implemented. In order to achieve computational efficiency, all sampling methods are written in C++ and seamless integrated into R by means of the Rcpp and RcppArmadillo packages. BNPmix exploits the ggplot2 capabilities and implements a series of generic functions to plot and print summaries of posterior densities and induced clustering of the data

Medium-Long-Term Clinical and Radiographic Outcomes of Minimally Invasive Distal Metatarsal Metaphyseal Osteotomy (DMMO) for Central Primary Metatarsalgia: Do Maestro Criteria Have a Predictive Value in the Preoperative Planning for This Percutaneous Technique?

The purpose of this prospective study was first to evaluate the safety and effectiveness of Minimally Invasive Distal Metatarsal Metaphyseal Osteotomy (DMMO) in treating central metatarsalgia, identifying possible contraindications. The second objective was to verify the potential of DMMO to restore a harmonious forefoot morphotype according to Maestro criteria. Methods. A consecutive series of patients with metatarsalgia was consecutively enrolled and treated by DMMO. According to Maestro criteria, preoperative planning was carried out by both clinical and radiological assessment. Patient demographic data, AOFAS scores, 17-FFI, MOXFQ, SF-36, VAS, and complications were recorded. Maestro parameters, relative morphotypes, and bone callus formation were assessed. Statistical analysis was carried out (p<0.05). Results. Ninety-three patients (93 feet) with a mean age of 62.4 (31-87) years were evaluated. At mean follow-up of 58.7 (36-96) months, all of the clinical scores improved significantly (p<0.0001). Most of the osteotomies (76.3%) had healed by 3-month follow-up, while ideal harmonious morphotype was restored only in a few feet (3.2%). Clinical and radiological outcomes were not different based on principal demographic parameters. Long-term complications were recorded in 12 cases (12.9%). Conclusion. DMMO is a safe and effective method for the treatment of metatarsalgia. Although Maestro criteria were useful to calculate the metatarsal bones to be shortened and a significant clinical improvement of all scores was achieved, the ideal harmonious morphotype was restored only in a few feet. Hence, our data show that Maestro criteria did not have a predictive value in clinical outcomes of DMM