Fano 4-folds, flips, and blow-ups of points

In this paper we study smooth, complex Fano 4-folds X with large Picard number rho(X), with techniques from birational geometry. Our main result is that if X is isomorphic in codimension one to the blow-up of a smooth projective 4-fold Y at a point, then rho(X) is at most 12. We give examples of such X with Picard number up to 9. The main theme (and tool) is the study of fixed prime divisors in Fano 4-folds, especially in the case rho(X)>6, in which we give some general results of independent interest.Comment: 44 pages. Minor changes, to appear in the Journal of Algebr

On the birational geometry of Fano 4-folds

We study the birational geometry of a Fano 4-fold X from the point of view of Mori dream spaces; more precisely, we study rational contractions of X. Here a rational contraction is a rational map f: X-->Y, where Y is normal and projective, which factors as a finite sequence of flips, followed by a surjective morphism with connected fibers. Such f is called elementary if the difference of the Picard numbers of X and Y is 1. We first give a characterization of non-movable prime divisors in X, when X has Picard number at least 6; this is related to the study of birational and divisorial elementary rational contractions of X. Then we study the rational contractions of fiber type on X which are elementary or, more generally, quasi-elementary. The main result is that the Picard number of X is at most 11 if X has an elementary rational contraction of fiber type, and 18 if X has a quasi-elementary rational contraction of fiber type.Comment: 43 pages. Final version, minor changes, to appear in Mathematische Annale

Competencies for young European higher education graduates: labor market mismatches and their payoffs

Articolo su competenze acquisite vs richieste e loro relazione con remunerazione e soddisfazione nel mercato del lavoro: analisi comparativa a livello europe

Migrants in the UK Labour Market: An Overview

This briefing provides an overview of the employment levels and employment shares of migrants in the UK economy as a whole, and in specific sectors and occupations

Getting Help from Course Management Software to Teach a Large-enrollment Introductory Geology Class

This article deals with utilizing the Internet as a medium for empowering learning and course management of on-campus classes using the enterprise-wide software system WebCT, which has proven to be very useful in managing a large introductory geology class. The author presents the results of her students' learning experience with WebCT. The article also provides a simple tutorial on how to create an Internet-enhanced course in less than a day using WebCT and with no prior knowledge of HTML language or FTP procedures. Educational levels: Graduate or professional

Covariance pattern mixture models for the analysis of multivariate heterogeneous longitudinal data

We propose a novel approach for modeling multivariate longitudinal data in the presence of unobserved heterogeneity for the analysis of the Health and Retirement Study (HRS) data. Our proposal can be cast within the framework of linear mixed models with discrete individual random intercepts; however, differently from the standard formulation, the proposed Covariance Pattern Mixture Model (CPMM) does not require the usual local independence assumption. The model is thus able to simultaneously model the heterogeneity, the association among the responses and the temporal dependence structure. We focus on the investigation of temporal patterns related to the cognitive functioning in retired American respondents. In particular, we aim to understand whether it can be affected by some individual socio-economical characteristics and whether it is possible to identify some homogenous groups of respondents that share a similar cognitive profile. An accurate description of the detected groups allows government policy interventions to be opportunely addressed. Results identify three homogenous clusters of individuals with specific cognitive functioning, consistent with the class conditional distribution of the covariates. The flexibility of CPMM allows for a different contribution of each regressor on the responses according to group membership. In so doing, the identified groups receive a global and accurate phenomenological characterization.Comment: Published at http://dx.doi.org/10.1214/15-AOAS816 in the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Genetic stability of Campylobacter coli in patients with primary antibody deficiencies

In the Clinical Communication, Dion et al 1 reported that in patients with severe primary antibody deficiency (PAD), Campylobacter infection is a major cause (6.5%) of chronic or recurrent diarrhea. Moreover, by a molecular study performed in a subset of 18 strains from 5 patients with recurrent infections, they demonstrated that all strains were different, even when the episodes occurred closely over time. Thus, the authors hypothesized that reinfection would be more likely than persistent colonization, although colonization with multiple strains cannot be excluded. In a previous study, 2 our group showed that Campylobacter coli (C. coli) (6.7%) was the first cause of diarrhea in patients with symptomatic PAD with a positive stool culture, followed by Campylobacter jejuni (C. jejuni) (3.9%). Moreover, C. coli was also the most frequent isolate (5%) in patients with asymptomatic PAD, followed by C. jejuni (1.2%), whereas in immunocompetent individuals, C. jejuni is one of the most prevalent etiologic agents of gastroenteritis and C. coli has a low prevalence in diarrheal disease

Log-biharmonicity and a Jensen formula in the space of quaternions

Given a complex meromorphic function, it is well defined its Riesz measure in terms of the laplacian of the logarithm of its modulus. Moreover, related to this tool, it is possible to prove the celebrated Jensen formula. In the present paper, using among the other things the fundamental solution for the bilaplacian, we introduce a possible generalization of these two concepts in the space of quaternions, obtaining new interesting Riesz measures and global (i.e. four dimensional), Jensen formulas.Comment: Final Version. To appear on Annales Academiae Scientiarum Fennicae Mathematica, Volume 44 (2019