Two-stage re-estimation adaptive design: a simulation study

  Background: adaptive clinical trial design has been proposed as a promising new approach to improve the drug discovery process. Among the many options available, adaptive sample size re-estimation is of great interest mainly because of its ability to avoid a large ‘up-front’ commitment of resources. In this simulation study, we investigate the statistical properties of two-stage sample size re-estimation designs in terms of type I error control, study power and sample size, in comparison with the fixed-sample study. Methods: we simulated a balanced two-arm trial aimed at comparing two means of normally distributed data, using the inverse normal method to combine the results of each stage, and considering scenarios jointly defined by the following factors: the sample size re-estimation method, the information fraction, the type of group sequential boundaries and the use of futility stopping. Calculations were performed using the statistical software SAS™ (version 9.2). Results: under the null hypothesis, any type of adaptive design considered maintained the prefixed type I error rate, but futility stopping was required to avoid the unwanted increase in sample size. When deviating from the null hypothesis, the gain in power usually achieved with the adaptive design and its performance in terms of sample size were influenced by the specific design options considered. Conclusions: we show that adaptive designs incorporating futility stopping, a sufficiently high information fraction (50-70%) and the conditional power method for sample size re-estimation have good statistical properties, which include a gain in power when trial results are less favourable than anticipated.&nbsp

Systemic risk governance in a dynamical model of a banking system

We consider the problem of governing systemic risk in a banking system model. The banking system model consists in an initial value problem for a system of stochastic differential equations whose dependent variables are the log-monetary reserves of the banks as functions of time. The banking system model considered generalizes previous models studied in [5], [4], [7] and describes an homogeneous population of banks. Two distinct mechanisms are used to model the cooperation among banks and the cooperation between banks and monetary authority. These mechanisms are regulated respectively by the parameters $\alpha$ and $\gamma$. A bank fails when its log-monetary reserves go below an assigned default level. We call systemic risk or systemic event in a bounded time interval the fact that in that time interval at least a given fraction of the banks fails. The probability of systemic risk in a bounded time interval is evaluated using statistical simulation. A method to govern the probability of systemic risk in a bounded time interval is presented. The goal of the governance is to keep the probability of systemic risk in a bounded time interval between two given thresholds. The governance is based on the choice of the log-monetary reserves of a kind of "ideal bank" as a function of time and on the solution of an optimal control problem for the mean field approximation of the banking system model. The solution of the optimal control problem determines the parameters $\alpha$ and $\gamma$ as functions of time, that is defines the rules of the borrowing and lending activity among banks and between banks and monetary authority. Some numerical examples are discussed. The systemic risk governance is tested in absence and in presence of positive and negative shocks acting on the banking system

Two-stage re-estimation adaptive design: a simulation study

Background: adaptive clinical trial design has been proposed as a promising new approach to improve the drug discovery process. Among the many options available, adaptive sample size re-estimation is of great interest mainly because of its ability to avoid a large ‘up-front’ commitment of resources. In this simulation study, we investigate the statistical properties of two-stage sample size re-estimation designs in terms of type I error control, study power and sample size, in comparison with the fixed-sample study. Methods: we simulated a balanced two-arm trial aimed at comparing two means of normally distributed data, using the inverse normal method to combine the results of each stage, and considering scenarios jointly defined by the following factors: the sample size re-estimation method, the information fraction, the type of group sequential boundaries and the use of futility stopping. Calculations were performed using the statistical software SAS™ (version 9.2). Results: under the null hypothesis, any type of adaptive design considered maintained the prefixed type I error rate, but futility stopping was required to avoid the unwanted increase in sample size. When deviating from the null hypothesis, the gain in power usually achieved with the adaptive design and its performance in terms of sample size were influenced by the specific design options considered. Conclusions: we show that adaptive designs incorporating futility stopping, a sufficiently high information fraction (50-70%) and the conditional power method for sample size re-estimation have good statistical properties, which include a gain in power when trial results are less favourable than anticipated.&nbsp

IN MIGRANTS’ SHOES. A GAME TO RAISE AWARENESS AND SUPPORT LONG-LASTING LEARNING

Questo contributo guarda al gioco come tecnologia per la comunicazione e l’apprendimento, analizzandolo in particolare come volto all’integrazione di migranti, tramite l’analisi del gioco urbano persuasivo A Hostile World e dei risultati di ricerca conseguiti in occasione della sua applicazione su due gruppi di adolescenti individuati per i loro comportamenti ostili nei confronti degli immigrati. Lo scopo del gioco è far immergere i partecipanti in situazioni inconsuete, per problematizzare e modi care attitudini mentali e preconcetti esistenti, promuovendo acquisizioni di saperi capaci di modi care comportamenti e aumentare l’empatia. Lo studio è una ricerca-azione condotta tramite questionari qualitativi somministrati pre- e post-esperienza, brevi interviste e focus group. L’analisi dei risultati rivela che i giocatori sono stati coinvolti in toccanti, scomodi processi di identi cazione che hanno ridotto pregiudizi esistenti, incrementando la comprensione delle fatiche e fragilità altrui, con risultati rilevanti in termini di apprendimento trasformativo, che ancora persiste.This contribution looks at the game as a technology for communicating, sharing and learning. It poses a specific focus on the play activity as a means to address cultural integration, presenting the analysis and research outcomes gleaned enquiring the persuasive urban game AHW (full name removed for blind peer review) and its application to a group of adolescents who manifested hostile feelings towards foreigners. The game intends to immerse players into awkward situations to problematise and modify their former mindset, prejudices and biases towards migrants, fostering effective learning outcomes able to affect behaviours and increase empathy. The enquiry is an action research conducted via pre- and post-experience qualitative questionnaires, short interviews and focus groups. The analysis reveals that players were involved in processes of moving, uncomfortable identification that lessened existing prejudices, increasing the comprehension of certain immigrants’ conditions and fragility, with relevant outcomes in terms of persisting transformative learning

Near-Extremal Limits of de Sitter Black Holes

We analyze the thermodynamic response near extremality of charged black holes in four-dimensional Einstein-Maxwell theory with a positive cosmological constant. The latter exhibit three different extremal limits, dubbed cold, Nariai and ultracold configurations, with near-horizon geometries AdS$_2 \times S^2$, dS$_2 \times S^2$, Mink$_2 \times S^2$, respectively. For each of these three cases we analyze small deformations away from extremality, and contrast their response. We also construct the effective two-dimensional theory, obtained by dimensional reduction, that captures these features and we provide a more detailed analysis of the perturbations around the near-horizon geometry for each case. Our results for the ultracold case in particular show an interesting interplay between the entropy variation and charge variation, realizing a different symmetry breaking with respect to the other two near-extremal limits.Comment: 32 pages, 2 figures; v3: typos fixed, clarifications on branches of 2D solutions added, comments on metric backreaction in sec. 4.2 removed. Section with outlook and conclusions adde

THE CORPORATE GOVERNANCE DRIVERS: WHAT RELATIONS WITH PERFORMANCE AND RISK? EMPIRICAL EVIDENCE FROM ITALIAN CONTEXT

Considering a sample of Italian firms and defining a good Governance index (gGI), we investigated if there is a relation between the gGI, the performance and the default risk and which governance determinants are most responsible of these effects. To deepen the analysis, the aforementioned relations are also observed by comparing family and non-family firms and the companies more or less active in M&A. We found that the Corporate Governance quality presents some correlations with performance and risk. The non-family companies are better structured, showing a positive correlation between some Corporate Governance drivers and performance and Z-score. Furthermore, the “well-advised” firms in external strategies are able to obtain a better correlation with performance and also a good relation with Z-scor

Strengthening e-Participation through Design Thinking. Relevance for Better Digital Public Services

In response to a lack of public participation, public administrations have been looking to e-participation as one strategy to overcome current barriers, such as lack of legitimacy and capacity, issues of representativeness, inclusiveness, equity and power balance, difficulties in effective implementation, and appropriate inclusion of citizens in decision-making processes. To tackle these challenges, literature has recognised the importance of including design thinking methodologies to reinforce public engagement and translate citizens’ suggestions for digital public service implementation. Acknowledging that research in this area is still limited, this paper proposes a rationale for the relevance of design thinking in implementing effective e-participation. Reviewing the relevant literature, the study proposes four different areas in which design thinking can support more effective citizen engagement in e-participation: (i) Meaning creation and sense-making, (ii) Publics formation, (iii) Co-production, and (iv) Experimentation and prototyping

THE CORPORATE GOVERNANCE DRIVERS, PERFORMANCE AND RISK: EMPIRICAL EVIDENCE FROM ITALIAN CONTEXT

In this work we carried out an empirical research on a sample of 98 Italian companies continuously listed during 2005-2011, with the objective of deepening the analysis : we tried to verify the role played by the Corporate on performance and default risk, with the definition of an index of good Governance (scG); we tried to verify the variables of Corporate Governance that produce effects on performance and risk of default (Z-score and leverage); we tried to verify the difference of effects of Corporate governance Index on performance and risk for family business and for companies active in M&A; we conducted an analysis on a sample of Italian companies to measure Corporate Governance quality and to evaluate the relationship with the accounting and market performance and the effect on risk level. We find that The Corporate Governance quality presents some correlation with performance and risk parameters. The non family companies are better structured. They show a positive correlation between some Corporate Governance drivers and performance and Z-score. We can observe that le “well-advised” firms in external strategies are able to obtain a better correlation with performance and also a good relation with Z-score