Risk Prediction for Prostate Cancer Recurrence Through Regularized Estimation with Simultaneous Adjustment for Nonlinear Clinical Effects

In biomedical studies, it is of substantial interest to develop risk prediction scores using high-dimensional data such as gene expression data for clinical endpoints that are subject to censoring. In the presence of well-established clinical risk factors, investigators often prefer a procedure that also adjusts for these clinical variables. While accelerated failure time (AFT) models are a useful tool for the analysis of censored outcome data, it assumes that covariate effects on the logarithm of time-to-event are linear, which is often unrealistic in practice. We propose to build risk prediction scores through regularized rank estimation in partly linear AFT models, where high-dimensional data such as gene expression data are modeled linearly and important clinical variables are modeled nonlinearly using penalized regression splines. We show through simulation studies that our model has better operating characteristics compared to several existing models. In particular, we show that there is a non-negligible effect on prediction as well as feature selection when nonlinear clinical effects are misspecified as linear. This work is motivated by a recent prostate cancer study, where investigators collected gene expression data along with established prognostic clinical variables and the primary endpoint is time to prostate cancer recurrence. We analyzed the prostate cancer data and evaluated prediction performance of several models based on the extended c statistic for censored data, showing that 1) the relationship between the clinical variable, prostate specific antigen, and the prostate cancer recurrence is likely nonlinear, i.e., the time to recurrence decreases as PSA increases and it starts to level off when PSA becomes greater than 11; 2) correct specification of this nonlinear effect improves performance in prediction and feature selection; and 3) addition of gene expression data does not seem to further improve the performance of the resultant risk prediction scores.     

The Influence of Unemployment Benefits on Unemployment Duration: Evidence from Spain

ABSTRACT: This paper analyses the duration of unemployment spells and the possible incidence of unemployment insurance on job search behaviour and voluntary duration of unemployment in Spain. To do so, a longitudinal data set containing information on unemployment recipients during the period 1987-93 is used. Hazard rates and survival profiles are constructed for the cohorts of unemployed workers entering the benefit system at different points in time, and a logit model of the probability of leaving the system before exhausting entitlement period is presented. The results do not support the view that the unemployed tend to intensify their job search when benefits are near exhaustion.     

Multicriteria decision making applied to waste recycling in Brazil

Waste management, like other environmental issues, tends to be a suitable topic for problem solving using multicriteria decision-making techniques when uncertainty is involved. This paper presents two cases where the decision makers had different preferences. In the first case, social agents required an evaluation of different disposal alternatives for plastic waste. In the second case, existing construction and demolition waste recycling facilities required a performance evaluation.     

Prioritization of bridges and tunnels in earthquake risk mitigation using multicriteria decision analysis: Application to Lisbon

This paper presents the development of a multicriteria value model enabling the prioritization of bridges and tunnels according to their structural vulnerability and strategic importance for the formulation and implementation of civil protection policies, both for retrofitting and emergency management, in face of seismic events. An interactive structuring process was developed with a group of key-players to carefully define the evaluation criteria and the MACBETH approach was extensively used (i) to facilitate the assessment from the group of the judgmental information necessary to build value functions and (ii) to establish relative weights for the criteria. The model was subsequently explored to prioritize the bridges and tunnels of a zone in Lisbon with high seismic hazard.     

Estimation of Long Memory in Integrated Variance

A stylized fact is that realized variance has long memory. We show that, when the instantaneous volatility is a long memory process of order d, the integrated variance is characterized by the same long-range dependence. We prove that the spectral density of realized variance is given by the sum of the spectral density of the integrated variance plus that of a measurement error, due to the sparse sampling and market microstructure noise. Hence, the realized volatility has the same degree of long memory as the integrated variance. The additional term in the spectral density induces a finite-sample bias in the semiparametric estimates of the long memory. A Monte Carlo simulation provides evidence that the corrected local Whittle estimator of Hurvich et al. (2005 Hurvich , C. M. , Moulines , E. , Soulier , P. ( 2005 ). Estimating long memory in volatility . Econometrica 73 ( 4 ): 1283 – 1328 .[Crossref], [Web of Science ®] , [Google Scholar]) is much less biased than the standard local Whittle estimator and the empirical application shows that it is robust to the choice of the sampling frequency used to compute the realized variance. Finally, the empirical results suggest that the volatility series are more likely to be generated by a nonstationary fractional process.     

When small is not enough: How to save entrepreneurs from themselves

This article goes beyond the traditional celebration of Entrepreneurship to focus on why Entrepreneurship is not enough. First, entrepreneurial companies that have overcome the start-up difficulties, must become “professionalized” in order to consolidate their gains and face a period of stable growth. This, as is well-known, is not easy. But there is another, even harder problem: in becoming “professional”, most companies lose the entrepreneurial spirit that made them successful in the first place. In an ever-changing world, with more and more international competition in the face of Europe's unification in 1992, a company that loses its entrepreneurial sparkle is just waiting for dismissal. This article analyzes the main causes of that “hardening of the arteries” and their proven remedies.     

Well-Being Among Spanish Lesbian,Gay, Bisexual and Heterosexual Adults: Disclosure of Sexual Orientation to Family and Friends

Relevance of disclosure of minority sexual orientation on subjective (SWB) and psychological well-being (PWB) was analyzed. Participants were 236 men and 238 women self-identified as lesbian, gay, and bisexual (LGB) or heterosexual. No differences in SWB were found between heterosexuals and LGBs. Heterosexual women showed greater environmental mastery than bisexual men and greater purpose in life than lesbian and bisexual women. Outcomes showed greater well-being among LGBs who disclosed their minority sexual orientation to parents later in life. Disclosing minority sexual orientation to parents was related with greater PWB. Further research that takes a differential approach to improve well-being for LGBs is needed.     

The educational (im)mobilities and status (il)legalities of Cape Verdean youth in Portugal

Education has played a fundamental role shaping Cape Verdean mobilities and recent increases in educational opportunities for poorer sections of the youth population have raised expectations for a better life. Through a discussion of how modern-day education has become a project of self-realisation, the article provides a detailed analysis of a regime of mobility that encouraged Cape Verdeans to study in vocational colleges in Portugal. It illustrates how the protocols signed between local councils in Cape Verde and the colleges created a responsibility vacuum that caused students to slip into illegality, perpetuating the inequalities which the pursuit of education is intended to redress. The ways in which Cape Verdean youth responded – navigating constraints to create the image of a successful life in Portugal against all odds – elucidate how the power of the moral expectation to succeed led them to work the system and to turn secondary education into a stepping stone for their mobility.