A Graphical Tool for Interpreting Regression Coefficients of Trinomial Logit Models

Multinomial logit (also termed multi-logit) models permit the analysis of the statistical relation between a categorical response variable and a set of explicative variables (called covariates or regressors). Although multinomial logit is widely used in both the social and economic sciences, the interpretation of regression coefficients may be tricky, as the effect of covariates on the probability distribution of the response variable is nonconstant and difficult to quantify. The ternary plots illustrated in this article aim at facilitating the interpretation of regression coefficients and permit the effect of covariates (either singularly or jointly considered) on the probability distribution of the dependent variable to be quantified. Ternary plots can be drawn both for ordered and for unordered categorical dependent variables, when the number of possible outcomes equals three (trinomial response variable); these plots allow not only to represent the covariate effects over the whole parameter space of the dependent variable but also to compare the covariate effects of any given individual profile. The method is illustrated and discussed through analysis of a dataset concerning the transition of master’s graduates of the University of Trento (Italy) from university to employment.     

The Evolution of Knowledge and the Dynamics of an Industry Network

The paper moves a step forward in the direction of establishing a connection between the structure and evolution of knowledge bases and the structure and evolution of organizational forms in innovative activities in a science-intensive industry. The paper has an explicit focus on the dynamics of the network of collaborative agreements in R&D in the pharma/biotech industry after the “molecular biology revolution”. Using a comprehensive dataset, built by the authors integrating several sources in the industry, the dynamics of the network over time is extensively analyzed. With regards to network structure, it is found that, while the size of the network increases over time due to net flows of entry, its topological properties remain relatively unchanged. The evolution of the network has occurred without relevant deformations in the core-periphery profile. With regards to age-dependent propensity to collaborate, the paper finds that the extent of inter-generational collaboration is much more significant than intra-generational collaboration. In addition, the propensity of firms of a given generation to enter into collaboration with firms of a different generation increases with the distance between the two, while the total number of intra-generational collaborations decreases over time and, moreover, tends to decrease for most recent generations. In the paper a unitary and coherent explanation of the evidence is developed, coming to reveal the existence of a striking isomorphism between structural properties of the dynamics of knowledge and of the evolution of network structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

Security branding and digital narrations. Security issues representation on Twitter

In the contemporary multicentric world, sovereign states have to manage carefully the construction of their image, defining their role and aspirations. With the re-definition of the state centric politics, stories become relevant: communication is a form of power, and networked forms of communication are becoming progressively a way to conquer the transnational public spheres. Through strategic narratives of foreign politics, states try to set up the ‘tales’ of international affairs and foreign strategies, to suggest a world vision, a causal interpretation, determining frames that affect transnational actors’ position in the international environment. Sovereign states develop these kind of frame using tools and theories referred to the commercial branding tradition to promote and support their own policies and identity. We decided to investigate how that process is made through information diffusion on digital platforms.

In this work, it has been analyzed the content presented through Twitter posts by the Foreign Ministries accounts of four different States dissimilar for geopolitical positioning and security concerns (USA; Israel; France; Sweden), for a period of three months (9/1/2015-11/30/2015); leading to the identification of different models and characteristic patterns of self-representation.

The thematic content analysis, based on the identification of macrocategories and micro-issues, has led to the identification of different models and characteristic patterns of self-representation, determined by domestic vicissitudes, and has shown some regularities, caused by the branding vocation of autobiographical online contents.     

Bootstrap Testing of Hypotheses on Co‐Integration Relations in Vector Autoregressive Models

It is well known that the finite‐sample properties of tests of hypotheses on the co‐integrating vectors in vector autoregressive models can be quite poor, and that current solutions based on Bartlett‐type corrections or bootstrap based on unrestricted parameter estimators are unsatisfactory, in particular in those cases where also asymptotic χ² tests fail most severely. In this paper, we solve this inference problem by showing the novel result that a bootstrap test where the null hypothesis is imposed on the bootstrap sample is asymptotically valid. That is, not only does it have asymptotically correct size, but, in contrast to what is claimed in existing literature, it is consistent under the alternative. Compared to the theory for bootstrap tests on the co‐integration rank (Cavaliere, Rahbek, and Taylor, 2012), establishing the validity of the bootstrap in the framework of hypotheses on the co‐integrating vectors requires new theoretical developments, including the introduction of multivariate Ornstein–Uhlenbeck processes with random (reduced rank) drift parameters. Finally, as documented by Monte Carlo simulations, the bootstrap test outperforms existing methods.     

Coming in like a wrecking-ball: are native Eurasian red squirrels displacing invasive Siberian chipmunks? A study from an urban park

Alien squirrels may seriously threaten native species by means of interspecific competition. In our work, we analysed whether the distribution of alien Siberian chipmunks within the Sigurtà Garden urban park (north-eastern Italy) changed after the natural spread of native Eurasian red squirrels in a 20-year period. Distribution of both squirrels was estimated through a citizen-science approach, in the first 10-year after red squirrel arrival 1 (i.e. Decade 1: 1997–2006) and in the second 10-year interval (i.e. Decade 2: 2007–2017). We compared habitat use of both species and we assessed whether a vertical segregation occurred through a dissimilarity index. Woodlands were selected by both species in both decades. Red squirrels also selected tree lines in Decade 1. A vertical segregation was apparent in Decade 1, whereas in Decade 2 both squirrel species were observed on the lowest branches or on the ground, where they are fed by humans. This was also confirmed by the habitat niche-overlap index, which increased in Decade 2. The extent of occurrence of Sciurus vulgaris increased throughout the park, whereas those of Eutamias sibiricus decreased. Differently from what is usually observed with alien squirrels, the spread of the native species appears to be halting and reversing the expansion of the non-native one.     

Association between long-term erectile dysfunction and biochemical recurrence after permanent seed I125 implant brachytherapy for prostate cancer. A longitudinal study of a single-institution

We aimed to investigate the predictive factor of erectile dysfunction (ED) in prostate cancer (PCa) patients who underwent low-dose permanent I¹²⁵ seed implant brachytherapy and to investigate if ED could represent a patient’s reported outcome measures (PROMs) of efficacy of BT and indirectly associated with biochemical recurrence free survival (BRFS). From 2000 to 2012, 176 consecutive patients with low-risk PCa underwent BT. ED was evaluated with the International Index of Erectile Function (IIEF-5). Cox regression analysis was performed to assess significant predictors of mild-to-severe ED and BRFS after BT, including covariates. The 10-year actuarial rate of ED was 66%. Subjects with severe ED had higher values of D90 (183.0 versus 177.0; p?p?p?p?=?0.20), while D90?≤?180?Gy independently predicted BCR (HR: 4.65; [95%CI: 1.25–17.34]; p?125 implant, but it is not associated with better BRFS.     

Designing from activities. The "ability /difficulty table", a useful tool to detect the "limit users" in the Design for All Approach

In the Design for All Approach (DfA), an important phase of the design process consists in the individuation of the so-called "limit users", that are that particular group of people with the most "critical" features for the autonomous fruition of a system or a product. Generally, however, it is not easy to identify them in a complete and objective way. A clear and complete outline of design requirements with respect to the "normal" use of a service, product or environment, moreover, is of fundamental importance in inclusive design. In fact, we know how bad design, that doesn't take in account the true "strategies of use", may lead to situations of handicap, also serious, temporary or permanent, regardless if the user is a "disabled" person or not. In relation to this scenario, the paper shows the results of a research which has developed the "Ability/Difficulty Table" ("A/D Table"), a new tool useful to identify the so-called "limit users" and their needs with respect to different activities, linking the main "difficulties", expressed by people, with the "abilities" required to carry out in autonomy the investigated activity.     

Blood ties and strong ties: a two-way linkage? Some non-trivial implications of the care workers market in a Mediterranean region

Taking their cue from a seeming dissonance between the theory of commodification and exploitation of migrant care workers and the case study of the outsourced self proposed by Hochschild, the author speculates whether or not the family–caregiver relationship may be equal and inclusive. The argument is unraveled by posing another question en route: what specific ‘catalysts’ can trigger ‘high-intensity affective relationships’? Elster defines 'essentially byproduct' the result of a process lacking any direct and conscious link between outcome and intention, and requiring the relaxation of the control of reason in order to be fulfilled. The author mixes significant theoretical results coming both from the relational Palo Alto School and from history of families studies, concluding that an equal and inclusive relationship may be like an Elster’s ‘essentially byproduct’ of a market relationship , when a high-intensity affective relation acts as a ‘catalyst’. The frame suggested in this article seems consistent with recent constructionist reinterpretations of the idea of kinship, which take shape and evolve through ‘everyday experiences’. Kinship thus shifts towards a more complex undefined category, that of Karsten’s relatedness. Speaking of which, the author argues some logical reasons suggesting a generalized adoption of the term only with great care and caution.     

An immune algorithm with stochastic aging and kullback entropy for the chromatic number problem

We present a new Immune Algorithm, IMMALG, that incorporates a Stochastic Aging operator and a simple local search procedure to improve the overall performances in tackling the chromatic number problem (CNP) instances. We characterize the algorithm and set its parameters in terms of Kullback Entropy. Experiments will show that the IA we propose is very competitive with the state-of-art evolutionary algorithms.