Network Reconstruction from Intrinsic Noise

This paper considers the problem of inferring an unknown network of dynamical systems driven by unknown, intrinsic, noise inputs. Equivalently we seek to identify direct causal dependencies among manifest variables only from observations of these variables. For linear, time-invariant systems of minimal order, we characterise under what conditions this problem is well posed. We first show that if the transfer matrix from the inputs to manifest states is minimum phase, this problem has a unique solution irrespective of the network topology. This is equivalent to there being only one valid spectral factor (up to a choice of signs of the inputs) of the output spectral density. If the assumption of phase-minimality is relaxed, we show that the problem is characterised by a single Algebraic Riccati Equation (ARE), of dimension determined by the number of latent states. The number of solutions to this ARE is an upper bound on the number of solutions for the network. We give necessary and sufficient conditions for any two dynamical networks to have equal output spectral density, which can be used to construct all equivalent networks. Extensive simulations quantify the number of solutions for a range of problem sizes. For a slightly simpler case, we also provide an algorithm to construct all equivalent networks from the output spectral density.Comment: 11 pages, submitted to IEEE Transactions on Automatic Contro

Quenching or Bursting: Star Formation Acceleration--A New Methodology for Tracing Galaxy Evolution

We introduce a new methodology for the direct extraction of galaxy physical parameters from multi-wavelength photometry and spectroscopy. We use semi-analytic models that describe galaxy evolution in the context of large scale cosmological simulation to provide a catalog of galaxies, star formation histories, and physical parameters. We then apply stellar population synthesis models and a simple extinction model to calculate the observable broad-band fluxes and spectral indices for these galaxies. We use a linear regression analysis to relate physical parameters to observed colors and spectral indices. The result is a set of coefficients that can be used to translate observed colors and indices into stellar mass, star formation rate, and many other parameters, including the instantaneous time derivative of the star formation rate which we denote the {\it Star Formation Acceleration (SFA)}, We apply the method to a test sample of galaxies with GALEX photometry and SDSS spectroscopy, deriving relationships between stellar mass, specific star formation rate, and star formation acceleration. We find evidence for a mass-dependent SFA in the green valley, with low mass galaxies showing greater quenching and higher mass galaxies greater bursting. We also find evidence for an increase in average quenching in galaxies hosting AGN. A simple scenario in which lower mass galaxies accrete and become satellite galaxies, having their star forming gas tidally and/or ram-pressure stripped, while higher mass galaxies receive this gas and react with new star formation can qualitatively explain our results.Comment: 33 pages, 31 figures, ApJ accepte

Marcas comerciais como indicador de inovação de produto e de evolução sectorial : uma aplicação ao negócio da imprensa escrita em Portugal

Mestrado em Economia e Gestão de Ciência, Tecnologia e InovaçãoO sector dos serviços representa actualmente cerca de dois terços do PIB das economias mais avançadas. Todavia, de acordo com a OCDE, o impacto deste sector numa economia moderna vai muito para além desta percentagem. Conhecer e quantificar o processo de inovação associado a este sector tornou-se, pois, relevante para tomadas de decisão em políticas de C&T. Na literatura económica existe um consenso crescente na utilização da ?marca? como indicador de inovação não-tecnológica, sobretudo apropriada à medição das inovações de marketing e com especial relevância para os serviços. A nossa pesquisa focou-se na imprensa escrita portuguesa que explorámos numa óptica Schumpeteriana, a partir de uma nova base de dados construída sistematicamente a partir de fontes primárias. Recolhemos a partir das plataformas electrónicas do INPI, da IHMI e da OMPI, 2471 pedidos de marca concedidos às 551 unidades de negócio que foram verificadas como sendo parte desta indústria (via APCT) para o período compreendido entre 1986 e 2014. Concentrámos a nossa enfoque nos vinte anos entre 1994 e 2013, incluindo na nossa análise todas as marcas com origem em títulos publicados pela população de editoras activas no período. Os resultados reflectem a competitividade e o dinamismo da indústria da imprensa escrita, mas também viragens dramáticas que caracterizam uma realidade em recomposição acelerada. A evidência mostra uma transformação estrutural ao nível das suas tecnologias de suporte e modelos de negócio, com implicações para a estratégia e política pública, que justifica mais pesquisa no futuro.The service sector represents more than two thirds of the GDP of developed economies. Nevertheless, according the OECD, the economic impact of services in the modern economies goes beyond that threshold. The quantification and understanding of the innovation process in the service sector has, indeed, become relevant for science and technology policy-making purposes. In the economic literature there is an increasing consensus about the use of trademakrs as an indicator of non-technological innovation, namely, about their use as a metrics of marketing innovations that characterise services. Our research foccuses in the Portuguese printed news industry. By analyzing the primary data and in accordance with Schumpeter?s theory we describe the evolution of this industry. The data was assembled from INPI, OHIM and WIPO databases, using the TM View platform. We collected data for 2471 trademarks applied for by the 551 business units that formed this industry during the period 1986 to 2014 (accordingly to the Portuguese organization that monitors newspaper and magazine circulation). Our analysis concentrates on the last two decades, from 1994 to 2013, and includes all trademarks from the entire population of publishers active during that period. The results reflect the competitiveness and dynamism of the print media industry, but also the dramatic turns that characterize a reality in accelerated change. The evidence shows a phenomenon of structural transformation in the supporting technologies and business models, with implications for strategy and public policy, which justifies more research in the future

Extending the 5S Framework of Digital Libraries to support Complex Objects, Superimposed Information, and Content-Based Image Retrieval Services

Advanced services in digital libraries (DLs) have been developed and widely used to address the required capabilities of an assortment of systems as DLs expand into diverse application domains. These systems may require support for images (e.g., Content-Based Image Retrieval), Complex (information) Objects, and use of content at fine grain (e.g., Superimposed Information). Due to the lack of consensus on precise theoretical definitions for those services, implementation efforts often involve ad hoc development, leading to duplication and interoperability problems. This article presents a methodology to address those problems by extending a precisely specified minimal digital library (in the 5S framework) with formal definitions of aforementioned services. The theoretical extensions of digital library functionality presented here are reinforced with practical case studies as well as scenarios for the individual and integrative use of services to balance theory and practice. This methodology has implications that other advanced services can be continuously integrated into our current extended framework whenever they are identified. The theoretical definitions and case study we present may impact future development efforts and a wide range of digital library researchers, designers, and developers

The Inflammatory Process in Response to Nanoparticles

products are already available on the market [1, 2]. The use of nanoparticles (NPs) has increased in the past few years in various fields including defence, aerospace, electronics, biology, and medicine. Therefore as human exposure to NPs increases, so do investigations on their toxicity. In one hand, nanotoxicology can be seen as an important subdiscipline of toxicology, and, on the other hand, it also represents a subdiscipline of nanotechnology [3]. Studies show that many parameters such as the diameter, surface area, surface composition, and solubility, to name a few, can all have an effect on cell responses, cellular interactions, and reactive oxygen species (ROS) production. They can also have an effect on NP capacity to bind to certain proteins or receptors. More importantly these parameters and others have also the potential to influence an inflammatory response following NP exposure as it has been shown in many in vitro and in vivo studies [4–7]. It has often been demonstrated that smaller particles tend to induce greater inflammatory responses than their bigger counterparts of same chemical composition [5]. Although some NPs may possess proinflammatory activities, the use of others and NP techniques can be very useful in medicine; for example, they can be used for drug-delivery therapies and may also represent excellent biomarkers for the diagnosis of diverse diseases, including inflammatory diseases. In an effort to increase our general knowledge regarding the inflammatory properties of NPs, thi