Screening by Mode of Trade

This paper proposes a mechanism design approach, capable of endogenizing a monopolist’s choice between selling and renting in a non-anonymous durable goods setting with short-term commitment. Allowing for mechanisms that determine the good’s allocation not only at the beginning but also at the end of a given period, we show that the profit-maximizing mechanism features screening by mode of trade. By selling to high types while renting to low types, the monopolist overcomes the obstacles encountered by intertemporal price discrimination and induces immediate separation of types for arbitrary low priors

Stories of devoted university students: the mathematical experience as a form of ascesis

Drawing on autobiographical essays written by master's students in mathematics preparing to become teachers, we investigate what mathematical identity these students articulate and how. By means of a discursive thematic analysis centered on the notion of ascesis, we show that the participants' identity revolves around a characterization of mathematics as a challenging, useful, and comforting activity or knowledge, which is however regarded negatively by others. Indeed, mathematics is described as a uniquely challenging activity which requires an increasingly demanding self-discipline. Moreover, mathematics is depicted as a variously useful form of knowledge which is additionally capable to offer comfort to those who engage with it. However, the participants often remark that other people regard mathematics negatively, a fact explained by stressing others' inability or unwillingness to understand or appreciate mathematics' inherent positive features. This sets the boundary of an ideal club of math enthusiasts whose elitist membership is regulated in terms of acceptance or refusal of its constitutive values. Belonging to the club as well as proselytizing in order to recruit new members appears to be central to the participants' mathematical identity

La finitezza del mondo rispetto al tempo nella Critica della Ragion Pura

Esaminerò gli argomenti kantiani esposti nella dialettica trascendentale per la necessità di un cominciamento temporale del mondo (tesi della prima antinomia) e per la necessità dell’assenza di un cominciamento del mondo (antitesi della prima antinomia). Sosterrò, servendomi di argomenti già di Arthur Schopenhauer, Kemp Smith, Bertrand Russell e Milton Fried, che l’argomento kantiano per la tesi è interamente da rigettare. Viceversa lo stesso non può dirsi dell’argomento per l’antitesi, che risulta logicamente valido: ipotizzare un inizio del mondo è contraddittorio. Concluderò infine con alcune riflessioni a proposito del simmetrico problema della fine del mondo, la quale, se intesa come un passaggio dall’essere al nulla, è anch’essa contraddittoria. Alternativamente, essa potrebbe configurarsi, seguendo Schopenhauer (e una interpretazione olistica del secondo principio della termodinamica), come l’ingresso del mondo in una fase definitiva di stasi.Esaminerò gli argomenti kantiani esposti nella dialettica trascendentale per la necessità di un cominciamento temporale del mondo (tesi della prima antinomia) e per la necessità dell’assenza di un cominciamento del mondo (antitesi della prima antinomia). Sosterrò, servendomi di argomenti già di Arthur Schopenhauer, Kemp Smith, Bertrand Russell e Milton Fried, che l’argomento kantiano per la tesi è interamente da rigettare. Viceversa lo stesso non può dirsi dell’argomento per l’antitesi, che risulta logicamente valido: ipotizzare un inizio del mondo è contraddittorio. Concluderò infine con alcune riflessioni a proposito del simmetrico problema della fine del mondo, la quale, se intesa come un passaggio dall’essere al nulla, è anch’essa contraddittoria. Alternativamente, essa potrebbe configurarsi, seguendo Schopenhauer (e una interpretazione olistica del secondo principio della termodinamica), come l’ingresso del mondo in una fase definitiva di stasi

GRAPES-DD: exploiting decision diagrams for index-driven search in biological graph databases

BACKGROUND: Graphs are mathematical structures widely used for expressing relationships among elements when representing biomedical and biological information. On top of these representations, several analyses are performed. A common task is the search of one substructure within one graph, called target. The problem is referred to as one-to-one subgraph search, and it is known to be NP-complete. Heuristics and indexing techniques can be applied to facilitate the search. Indexing techniques are also exploited in the context of searching in a collection of target graphs, referred to as one-to-many subgraph problem. Filter-and-verification methods that use indexing approaches provide a fast pruning of target graphs or parts of them that do not contain the query. The expensive verification phase is then performed only on the subset of promising targets. Indexing strategies extract graph features at a sufficient granularity level for performing a powerful filtering step. Features are memorized in data structures allowing an efficient access. Indexing size, querying time and filtering power are key points for the development of efficient subgraph searching solutions.RESULTS: An existing approach, GRAPES, has been shown to have good performance in terms of speed-up for both one-to-one and one-to-many cases. However, it suffers in the size of the built index. For this reason, we propose GRAPES-DD, a modified version of GRAPES in which the indexing structure has been replaced with a Decision Diagram. Decision Diagrams are a broad class of data structures widely used to encode and manipulate functions efficiently. Experiments on biomedical structures and synthetic graphs have confirmed our expectation showing that GRAPES-DD has substantially reduced the memory utilization compared to GRAPES without worsening the searching time.CONCLUSION: The use of Decision Diagrams for searching in biochemical and biological graphs is completely new and potentially promising thanks to their ability to encode compactly sets by exploiting their structure and regularity, and to manipulate entire sets of elements at once, instead of exploring each single element explicitly. Search strategies based on Decision Diagram makes the indexing for biochemical graphs, and not only, more affordable allowing us to potentially deal with huge and ever growing collections of biochemical and biological structures