Estimating the grid of time-points for the piecewise exponential model

One of the greatest challenges related to the use of piecewise exponential models (PEMs) is to find an adequate grid of time-points needed in its construction. In general, the number of intervals in such a grid and the position of their endpoints are ad-hoc choices. We extend previous works by introducing a full Bayesian approach for the piecewise exponential model in which the grid of time-points (and, consequently, the endpoints and the number of intervals) is random. We estimate the failure rates using the proposed procedure and compare the results with the non-parametric piecewise exponential estimates. Estimates for the survival function using the most probable partition are compared with the Kaplan-Meier estimators (KMEs). A sensitivity analysis for the proposed model is provided considering different prior specifications for the failure rates and for the grid. We also evaluate the effect of different percentage of censoring observations in the estimates. An application to a real data set is also provided. We notice that the posteriors are strongly influenced by prior specifications, mainly for the failure rates parameters. Thus, the priors must be fairly built, say, really disclosing the expert prior opinion.     

A Quality Risk Management Model Approach for Cell Therapy Manufacturing

International regulatory authorities view risk management as an essential production need for the development of innovative, somatic cell‐based therapies in regenerative medicine. The available risk management guidelines, however, provide little guidance on specific risk analysis approaches and procedures applicable in clinical cell therapy manufacturing. This raises a number of problems. Cell manufacturing is a poorly automated process, prone to operator‐introduced variations, and affected by heterogeneity of the processed organs/tissues and lot‐dependent variability of reagent (e.g., collagenase) efficiency. In this study, the principal challenges faced in a cell‐based product manufacturing context (i.e., high dependence on human intervention and absence of reference standards for acceptable risk levels) are identified and addressed, and a risk management model approach applicable to manufacturing of cells for clinical use is described for the first time. The use of the heuristic and pseudo‐quantitative failure mode and effect analysis/failure mode and critical effect analysis risk analysis technique associated with direct estimation of severity, occurrence, and detection is, in this specific context, as effective as, but more efficient than, the analytic hierarchy process. Moreover, a severity/occurrence matrix and Pareto analysis can be successfully adopted to identify priority failure modes on which to act to mitigate risks. The application of this approach to clinical cell therapy manufacturing in regenerative medicine is also discussed.     

Explaining performing R&D through alliances: Implications for the business model of Italian dedicated biotech firms

In recent years management scholars and practitioners have been interested in Research and Development (R&D) partnering, especially in high-tech industries. While the motivations of research partnership formation have been widely explored in literature, little attempt has been undertaken to examine the effects of research partnerships on R&D productivity and the implications for business models of the new ventures. In this paper we try to shed some light on the business models of the young ventures involved in R&D partnerships and their effect on R&D productivity. Our hypotheses are that experience in previous alliances, repeated partnerships and tight relationships have positive effects on R&D productivity while rigid governance structures and public R&D subsidies have negative effects on such productivity. We discuss how these aspects affect the business models of biotech firms. We test our hypotheses on a sample of 55 Italian DBFs (Dedicated Biotech Firms). Results support our hypotheses. Managerial implications and further issues for future research are discussed.     

Race and the beauty premium: Mechanical Turk workers’ evaluations of Twitter accounts

ABSTRACT

Race, gender, and physical attractiveness strongly affect perceptions of trustworthiness and subsequent face-to-face interactions. This study examines how social media users’ perceived gender, race, and physical attractiveness can impact their standing online. We test these broad hypotheses by having Amazon Mechanical Turk (MTurk) workers evaluate a sample of 816 Twitter accounts. Our results show a ‘beauty premium,’ where MTurk workers say they are more likely to follow Twitter accounts with attractive pro?le photos, and attractive photos are positively associated with evaluations of trust. However, very attractive Black male and female Twitter accounts are associated with lower evaluations of trust compared to their White counterparts. These findings suggest that social media users’ social characteristics, perceived from their username or profile image, can replicate offline inequality online.     

Knowledge Creation within Industrial Systems

Intangible resources are the source of competitive advantage in theknowledge economy. Knowledge and intellectual capital within firms havegathered worldwide attention; theories and methods for knowledgecreation management have been developed for organizations and alliances.Economic reality shows the importance of industrial districts becausesocial systems in districts provide dynamic contexts of multifacetedrelationships. These dynamic contexts or district ba (Japanesefor place) enable firms to create and harness knowledge that resides innetwork relationships.The paper develops a theoretical frame of four kinds of district ba thatsupport four knowledge processes. Organizational networks within andbetween different district ba are conceptualized. The creationof knowledge within district ba is used to analyze differentlevels of interaction between firms in the same or different districtsand in the same or different industries. The case study of the JETROlocal-to-local program between Ishikawa prefecture in Japan and Como andVarese in Italy is used to illustrate the theoretical concepts. Districtba are used to analyze the knowledge creation dynamics withinand between districts and to identify possible strategies for districtgovernance.     

Sexual Prejudice in Sport Scale: A New Measure

ABSTRACT

This study describes the process of developing and validating the Sexual Prejudice in Sport Scale (SPSS), which is a multidimensional instrument developed to assess attitudes toward lesbians and gay men (LG) in sports. The authors conducted two studies: first, to establish the factor structure of the SPSS on 297 heterosexual athletes; and, second, to test the reliability and validity of the resulting 19-item scale on a sample of 311 heterosexual and 160 LG athletes. Exploratory factor analysis of an initial item pool yielded three factors: open rejection, which assesses the blatant prejudice expressed toward LG people; denial of visibility, which evaluates attitude toward the coming out of LG people; and gendering performance, which corresponds to gender stereotypes about performance/skills of LG people. A confirmatory factor analysis was conducted to assess the stability of the SPSS. The authors documented internal consistency, test-retest stability, and convergent/divergent validity. Implications and directions for future research are discussed.     

Optimal Treatment Schedule in Insect Pest Control in Viticulture

A model for the control of the European grapevine moth Lobesia botrana includes two control methods: insecticides and mating disruption. It yields the combination and schedule of application that minimize cost and losses due to the pest. A simulation is presented for an experimental situation.     

When an Event Makes a Difference

For (S, Σ) a measurable space, let and be convex, weak^* closed sets of probability measures on Σ. We show that if ∪ satisfies the Lyapunov property , then there exists a set A ∈ Σ such that min_μ1∈ μ₁(A) > max_μ2 ∈ (A). We give applications to Maxmin Expected Utility (MEU) and to the core of a lower probability.     

The Place of Framing: Multiple Audiences and Antiwar Protests near Fort Bragg

Social movement leaders regularly invoke geographic places—such as cities, parks, and monuments—as symbols in strategic efforts to frame social movement activity. This article examines how place affects framing processes inside a movement and counterprotester responses with an ethnography of anti-Iraq War protests in Fayetteville, North Carolina. We show how place attracts the attention of movement leaders, creates opportunities for local community members to assert their interests, suppresses some frames within the movement, and encourages opponents to co-opt the meaning of place for their own ends. The multiple meanings of place can broaden the scope of conflict and reduce a movement leader’s ability unilaterally to define a movement’s agenda and public image.