A model for the quasi-static growth of brittle fractures based on local minimization

We study a variant of the variational model for the quasi-static growth of brittle fractures proposed by Francfort and Marigo. The main feature of our model is that, in the discrete-time formulation, in each step we do not consider absolute minimizers of the energy, but, in a sense, we look for local minimizers which are sufficiently close to the approximate solution obtained in the previous step. This is done by introducing in the variational problem an additional term which penalizes the $L^2$-distance between the approximate solutions at two consecutive times. We study the continuous-time version of this model, obtained by passing to the limit as the time step tends to zero, and show that it satisfies (for almost every time) some minimality conditions which are slightly different from those considered in Francfort and Marigo and in our previous paper, but are still enough to prove (under suitable regularity assumptions on the crack path) that the classical Griffith's criterion holds at the crack tips. We prove also that, if no initial crack is present and if the data of the problem are sufficiently smooth, no crack will develop in this model, provided the penalization term is large enough.Comment: 20 page

Family businesses in Eastern European countries: How informal payments affect exports

This article investigates the effect of corruption on the export share of family firms in Eastern European countries. Using the Business Environment and Enterprise Performance Survey and panel data methods, we find that, in contrast to non-family firms, family firms are rather sensitive to corruption. In particular, the export share of family firms is positively associated with informal payments that aim to facilitate business operations. There are at least three compelling explanations for these results. First, if family firms are more risk averse than non-family firms, informal payments may represent additional export risk insurance. Second, informal payments may help family firms compensate for the lack of managerial capabilities to export. Finally, when institutional inefficiencies obstruct business, corruption may be a tool for family firms to protect their socioemotional wealth

On weak convergence of locally periodic functions

We prove a generalization of the fact that periodic functions converge weakly to the mean value as the oscillation increases. Some convergence questions connected to locally periodic nonlinear boundary value problems are also considered.Comment: arxiv version is already officia

Why and when do family firms invest less in talent management? The suppressor effect of risk aversion

none4siThis article explores the complex relationship between family firms and talent management practices. We use an international sample of medium-sized manufacturing firms to show that the relationship between family-owned firms and investment in talent management practices is mediated by the firm’s level of risk aversion, which is, in turn, moderated by industry competition. Risk-averse family-owned firms tend to invest less in talent management practices when industry competition is weak. In contrast, when competition increases, family-owned firms tend to invest in talent as much as non-family-owned firms do.openBasco, Rodrigo; Bassetti, Thomas; Dal Maso, Lorenzo; Lattanzi, NicolaBasco, Rodrigo; Bassetti, Thomas; Dal Maso, Lorenzo; Lattanzi, Nicol

LEGAME TRA L\ubfIMMUNODEFICIENZA HIV-CORRELATA E L\ubfINSORGENZA DI TUMORI: ASPETTI DI METODOLOGIA STATISTICA

The aim of the present Ph.D. program was exploring methodological issues arising in studies of cancer incidence, relative risk, and survival in patients with HIV/AIDS (PHA). Aspects related to the first two objectives were explored in the first two years. This thesis described a record-linkage study conducted between the national Italian AIDS Registry and 24 Italian cancer registries to estimate survival after a cancer diagnosis in PHA. More than 2600 cancer cases diagnosed between 1986 and 2005 were included. Survival in PHA was compared with that reported in patients without AIDS using, as comparison group, patients matched for site (1:1 for Kaposi Sarcoma, 1:2 for non-Hodgkin lymphoma, 1:5 for other cancers), sex, age, period of diagnosis, and area of residence. Overall survival and death hazard ratios (HR) compared survival in PWA with cancer to that in cancer patients without AIDS have been calculated. Overall, the 3-year survival rate of PHA with cancer increased from 16% in 1986-1995 to 41% in 1996-2005 period, after the widespread use of antiretroviral therapy (cART). In this period, HR remained higher in PHA than in persons without AIDS (3.0, 95% confidence interval [CI]: 2.7\u20133.4), in particular for cancer with good prognosis, e.g., Hodgkin lymphomas (HR=8.6), non-melanoma skin cancer (H=5.0), and anal cancer (HR=4.0). A sensitivity analysis was performed to evaluate the impact on survival and on HR of different study designs and comparison groups

Is accounting enforcement related to risk-taking in the banking industry?

Using a sample of banks from 36 countries, we document that accounting enforcement is negatively related to bank risk-taking. We also provide evidence that accounting enforcement enhances bank stability during the crisis. In addition, we show that banks assume less risk through more conservative lending decisions and a reduction in complexity in jurisdictions with higher accounting enforcement. Our results show that formal institutions such as accounting enforcement are associated with bank financial decisions and risk-taking behavior

Power calculation for gravitational radiation: oversimplification and the importance of time scale

A simplified formula for gravitational-radiation power is examined. It is shown to give completely erroneous answers in three situations, making it useless even for rough estimates. It is emphasized that short timescales, as well as fast speeds, make classical approximations to relativistic calculations untenable.Comment: Three pages, no figures, accepted for publication in Astronomische Nachrichte

A global method for deterministic and stochastic homogenisation in BV

In this paper we study the deterministic and stochastic homogenisation of free-discontinuity functionals under linear growth and coercivity conditions. The main novelty of our deterministic result is that we work under very general assumptions on the integrands which, in particular, are not required to be periodic in the space variable. Combining this result with the pointwise Subadditive Ergodic Theorem by Akcoglu and Krengel, we prove a stochastic homogenisation result, in the case of stationary random integrands. In particular, we characterise the limit integrands in terms of asymptotic cell formulas, as in the classical case of periodic homogenisation

Leanness and squamous cell oesophageal cancer

Background: Squamous cell oesophageal cancer is one of the few neoplasms inversely related to body mass index (BMI). However, it is not clear whether this is due to cancer-related weight loss or to other correlates of leanness. Patients and methods: 395 incident, histologically confirmed cases of squamous cell oesophageal cancer and 1,066 controls, admitted for acute, non-neoplastic diseases, in Italy and Switzerland. Odds ratios (ORs) were derived from multiple logistic regression, including terms for education, tobacco, alcohol, non-alcohol energy, fruit and vegetable intake Results: The ORs for the lowest vs. the highest quartile of BMI in the year before diagnosis were 2.0 in men, 1.6 in women, and 1.9 (95% confidence interval: 1.3-2.9) in both sexes combined. The association with leanness was stronger in heavy smokers, but was not accounted for by smoking and drinking, nor by differences in diet. Weight change in the decade prior to diagnosis showed no linear association with risk. However, cases were not leaner than controls at age 30 (OR = 0.6 for the lowest BMI quartile) and 50 (OR = 1.1). Conclusions: Leanness appears to be an indicator of squamous cell oesophageal carcinogenesis. However, low BMI in the distant past was unrelated to oesophageal cancer ris