Reversible signal transmission in an active mechanical metamaterial

Mechanical metamaterials are designed to enable unique functionalities, but are typically limited by an initial energy state and require an independent energy input to function repeatedly. Our study introduces a theoretical active mechanical metamaterial that incorporates a biological reaction mechanism to overcome this key limitation of passive metamaterials. Our material allows for reversible mechanical signal transmission, where energy is reintroduced by the biologically motivated reaction mechanism. By analysing a coarse grained continuous analogue of the discrete model, we find that signals can be propagated through the material by a travelling wave. Analysis of the continuum model provides the region of the parameter space that allows signal transmission, and reveals similarities with the well-known FitzHugh-Nagumo system. We also find explicit formulae that approximate the effect of the timescale of the reaction mechanism on the signal transmission speed, which is essential for controlling the material.Comment: 20 pages, 7 figure

Extended diffeomorphism algebras in (quantum) gravitational physics

We construct an explicit representation of the algebra of local diffeomorphisms of a manifold with realistic dimensions. This is achieved in the setting of a general approach to the (quantum) dynamics of a physical system which is characterized by the fundamental role assigned to a basic underlying symmetry. The developed mathematical formalism makes contact with the relevant gravitational notions by means of the addition of some extra structure. The specific manners in which this is accomplished, together with their corresponding physical interpretation, lead to different gravitational models. Distinct strategies are in fact briefly outlined, showing the versatility of the present conceptual framework.Comment: 20 pages, LATEX, no figure

Hybrid Governance and the Attribution of Political Responsibility: Experimental Evidence from the United States

How does the mode of public service delivery affect the attribution of responsibility for public goods? Through a survey experiment on a sample of more than 1,000 Americans, we provide evidence of how the allocation of public goods shapes voters’ support for incumbent politicians. We find that voters prefer a mixture of public–private financing and management when it comes to the delivery of infrastructure. However, once performance information is available, the mode of infrastructure delivery no longer influences their voting intention. The successful delivery of these infrastructure projects is what ultimately matters to voters. Moreover, this preference for a mixture of public and private involvement in public service delivery is stronger among citizens with high political knowledge, who are more likely to punish the incumbent for a failed first phase of the public service delivery. These findings deepen our understanding of how hybrid forms of public service delivery are perceived by voters and how performance information affects evaluations of the performance of public services and politicians alike. // In che misura le modalità di erogazione dei servizi pubblici influenzano l’attribuzione di responsabilità per la gestione dei beni pubblici? Tramite un esperimento su un campione di più di 1000 americani, dimostriamo come l’allocazione di beni pubblici condizioni il sostegno elettorale dei politici in carica da parte degli elettori. In merito al finanziamento e alla gestione dei servizi pubblici, risulta che gli elettori preferiscono un mix tra pubblico e privato. Tuttavia, non appena sono disponibili informazioni sulla performance, non sono più le modalità di erogazione del servizio a influenzare le intenzioni di voto degli elettori, bensì la riuscita dei progetti stessi. Inoltre, questa preferenza per un mix tra pubblico e privato nell’erogazione dei servizi pubblici è più marcata tra gli elettori con livelli più elevati di conoscenza politica, che si mostrano più propensi a punire il politico in carica nel caso di fallimento nella prima fase di erogazione del servizio pubblico. Questi risultati ci aiutano a capire meglio come certe forme ibride di erogazione dei servizi pubblici siano percepite dagli elettori e come le informazioni sulla performance influiscano sia la valutazione dei servizi pubblici che quella dei politici

Fungal gold and firewood on the Tibetan plateau: Examining access to diverse ecosystem provisioning services within a rural community

Provisioning ecosystem services include wild products that form an integral part of rural economies. Using quantitative and qualitative data from semi-structured interviews with 50 households in a Tibetan community in Western Sichuan, China, we explored the relationships of households with three diverse provisioning services on the Eastern Tibetan plateau: firewood, medicinal caterpillar fungus Ophiocordyceps sinensis and matsutake mushrooms Tricholoma matsutake. We examined (1) how they contribute to wealth and livelihoods, (2) what determines household access, and (3) how local use has changed over time. All households were reliant on firewood, and levels extracted were explained only by household size. A more complex set of factors explained access to caterpillar fungus: younger, larger, pastoralist households with lower dependency ratios tended to collect more, and education and household size explained variation in price gained for the product. Caterpillar fungus extraction has dramatically increased over the last 20 years, providing up to 72% of household income, but poorer households have received significantly less of their income from the fungus. Matsutake contributed much less to livelihoods because of its relatively low price. The results show a contrast between subsistence and market-driven products: access to the latter is affected by competition and power relationships. Overall access to provisioning services was related to facets of wealth, especially human capital. The study contributes a household level analysis of the diverse provisioning value of an under-researched part of the world, highlighting the heterogeneity and dynamism of the relationships of households with ecosystem services

The relationship between adult attachment style and post-traumatic stress symptoms: A meta-analysis

There is increasing evidence that adult attachment plays a role in the development and perseverance of symptoms of posttraumatic stress disorder (PTSD). This meta-analysis aims to synthesise this evidence and investigate the relationship between adult attachment styles and PTSD symptoms. A random-effects model was used to analyse 46 studies (N = 9268) across a wide range of traumas. Results revealed a medium association between secure attachment and lower PTSD symptoms (ρ =-.27), and a medium association, in the opposite direction, between insecure attachment and higher PTSD symptoms (ρ =.26). Attachment categories comprised of high levels of anxiety most strongly related to PTSD symptoms, with fearful attachment displaying the largest association (ρ =.44). Dismissing attachment was not significantly associated with PTSD symptoms. The relationship between insecure attachment and PTSD was moderated by type of PTSD measure (interview or questionnaire) and specific attachment category (e.g. secure, fearful). Results have theoretical and clinical significance

Numerical Study of the Impact of Vibration Localization on the Motional Resistance of Weakly Coupled MEMS Resonators

This paper presents a numerical study of the impact of process-induced variations on the achievable motional resistance Rx of one-dimensional, two-dimensional, cyclic and cross-coupled architectures of weakly coupled, electrostatically transduced MEMS resonators operating in the 250 kHz range. We use modal analysis to find the Rx of such coupled arrays and express it as a function of the eigenvectors of the specific mode of vibration. Monte Carlo numerical simulations, which accounted for up to 0.75% variation in critical resonator feature sizes, were initiated for different array sizes and coupling strengths, for the four distinct coupling architectures. Improvements in the mean and standard deviation of the generated Rx distributions are reported when the resonators are implemented in a cross-coupled scheme, as opposed to the traditional one-dimensional chain. The two-dimensional coupling scheme proves to be a practical and scalable alternative to weakly coupled one-dimensional chains to improve the immunity to process variations. It is shown that a 75% reduction in both the mean and standard deviation of the Rx is achieved as compared to the traditional one-dimensional chain for a normalized internal coupling k > 10-2.The authors would like to gratefully acknowledge the Qualcomm European Research Studentships in Technology and the UK Engineering and Physical Sciences Research Council.This is the accepted manuscript. The final version is available from IEEE at http://dx.doi.org/10.1109/JMEMS.2014.2371072

Partnership Communities

We undertake the first quantitative and broadly comparative study of the structure and performance of partnership communities to our knowledge. Our study addresses several important research questions. How connected are the members of partnership communities? How can we understand the quality of the projects a community undertakes? How do political institutions shape their structure and performance? After defining partnership communities as networked communities of private firms which form the consortia that enter into long-term contractual arrangements with governments, we show how they are affected by government demand for partners. We then provide an overview of those factors predicting success in financing projects. Finally, we focus on the political economy of partnership communities. We develop and test theoretical predictions about how national institutions shape partnership communities and the quality of projects. We also investigate voters' preferences over alternative arrangements of infrastructure delivery before drawing out implications for research and practice

Abelian BF theory and Turaev-Viro invariant

The U(1) BF Quantum Field Theory is revisited in the light of Deligne-Beilinson Cohomology. We show how the U(1) Chern-Simons partition function is related to the BF one and how the latter on its turn coincides with an abelian Turaev-Viro invariant. Significant differences compared to the non-abelian case are highlighted.Comment: 47 pages and 6 figure