University of Siena

About: University of Siena is a education organization based out in Siena, Italy. It is known for research contribution in the topics: Population & Cancer. The organization has 12179 authors who have published 33334 publications receiving 1008287 citations. The organization is also known as: Università degli studi di Siena & Universita degli studi di Siena.

Coordinated Punishment of Defectors Sustains Cooperation and Can Proliferate When Rare

Abstract: Because mutually beneficial cooperation may unravel unless most members of a group contribute, people often gang up on free-riders, punishing them when this is cost-effective in sustaining cooperation. In contrast, current models of the evolution of cooperation assume that punishment is uncoordinated and unconditional. These models have difficulty explaining the evolutionary emergence of punishment because rare unconditional punishers bear substantial costs and hence are eliminated. Moreover, in human behavioral experiments in which punishment is uncoordinated, the sum of costs to punishers and their targets often exceeds the benefits of the increased cooperation that results from the punishment of free-riders. As a result, cooperation sustained by punishment may actually reduce the average payoffs of group members in comparison with groups in which punishment of free-riders is not an option. Here, we present a model of coordinated punishment that is calibrated for ancestral human conditions and captures a further aspect of reality missing from both models and experiments: The total cost of punishing a free-rider declines as the number of punishers increases. We show that punishment can proliferate when rare, and when it does, it enhances group-average payoffs.

The adhesion between fiber posts and root canal walls: comparison between microtensile and push-out bond strength measurements.

Abstract: Aim of the study was to compare the trimming and non-trimming variants of the microtensile technique with the 'micro' push-out test in the ability to measure accurately the bond strength of fiber posts luted inside root canals. In 15 endodontically treated teeth (Group A), fiber posts were cemented with Excite DSC in combination with Variolink II (Ivoclar-Vivadent). In 15 roots RelyX Unicem (3M-ESPE) was used for fiber post luting (Group B). Within each group, the bond strength of cemented fiber posts was assessed with the trimming and non-trimming microtensile technique, as well as with the push-out test. The great number of premature failures (16.9% in Group A, 27.5% in Group B) and the finding of high standard deviation values make questionable the reliability of the trimming microtensile technique. With the non-trimming microtensile technique, only five sticks were obtained from a total of six roots. The remaining specimens failed prematurely during the cutting phase. With the push-out test no premature failure occurred, the variability of the data distribution was acceptable, and regional differences in bond strength among root levels could be assessed. Relatively low values of bond strength were, in general, recorded for luted fiber posts. In conclusion, when measuring the bond strength of luted fiber posts, the push-out test appears to be more dependable than the microtensile technique.

GW150914: The Advanced LIGO Detectors in the Era of First Discoveries

Abstract: Following a major upgrade, the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) held their first observation run between September 2015 and January 2016. With a strain sensitivity of $10^{-23}/\sqrt{\mathrm{Hz}}$ at 100 Hz, the product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation. On September 14th, 2015 the Advanced LIGO detectors observed a transient gravitational-wave signal determined to be the coalescence of two black holes [Phys. Rev. Lett. 116, 061102 (2016)], launching the era of gravitational-wave astronomy. The event, GW150914, was observed with a combined signal-to-noise ratio of 24 in coincidence by the two detectors. Here we present the main features of the detectors that enabled this observation. At full sensitivity, the Advanced LIGO detectors are designed to deliver another factor of three improvement in the signal-to-noise ratio for binary black hole systems similar in masses to GW150914.

The Cartography of Syntactic Structures

Abstract: 1. Introduction Syntactic structures are complex objects, whose subtle properties have been highlighted and elucidated by half a century of formal syntactic studies, building on a much older tradition. Structures are interesting objects of their own, both in their internal constitution and in their interactions with various grammatical principles and processes. The cartography of syntactic structures is the line of research which addresses this topic: it is the attempt to draw maps as precise and detailed as possible of syntactic configurations. Broadly construed in this way, cartography is not an approach or a hypothesis: it is a research topic asking the question: what are the right structural maps for natural language syntax? Answers may differ, and very different maps may be, and have been, proposed, but the question as such inevitably arises as a legitimate and central question for syntactic theory. If it is a virtual truism that cartography can be construed as a topic and not as a framework, it is also the case that cartographic studies have often adopted certain methodological and heuristic guidelines, and also certain substantive hypotheses on the nature of syntactic structures, which form a coherent body of assumptions and a rather well-defined research direction; we will try to illustrate some ideas and results of this direction in the present chapter. If structures have, in a sense, always been central in generative grammar, the idea of focusing on structural maps arose around the early nineties, following a track parallel to and interacting with the Minimalist Program. Perhaps the main triggering factor was the explosion of functional heads identified and implied in syntactic analyses in the first ten years of the Principles and Parameters framework. One critical step was the full-fledged extension of X-bar theory to the functional elements of the clause (Chomsky 1986) as a CP – IP – VP structure; and the observation that other configurations, e.g. nominal expressions, were amenable to a hierarchical structure with a lexical projection embedded within a functional structure (such as Abney's DP hypothesis, Abney 1987). These advances provided a natural format for the study of the structure of phrases and clauses as hierarchical sequences of the same building block, the fundamental X-bar schema (or, later, elementary applications of Merge); the lowest occurrence of the building block typically is the projection of a lexical category, e.g. a noun or a verb, and this element is typically completed by a …