Ultrasound-induced Reactive Oxygen Species generation by Zinc Oxide Nanostructures: Mechanisms and Applications

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On the Structure of BV Entropy Solutions for Hyperbolic Systems of Balance Laws with General Flux Function

The paper describes the qualitative structure of BV entropy solutions of a general strictly hyperbolic system of balance laws with characteristic field either piecewise genuinely non- linear or linearly degenerate. In particular, we provide an accurate description of the local and global wave-front structure of a BV solution generated by a fractional step scheme combined with a wave-front tracking algorithm. This extends the corresponding results which were obtained in [Bianchini-Yu] for strictly hyperbolic system of conservation laws

Determining the dynamics of collaboration in EU Framework Programmes under a network perspective

Collaborative networks gained attention in the field of economics of innovation in the recent past. One of the main interests concerns the temporal analysis of such networks, both in a scientific and in a European policy context. At the European level indeed, the objective is to promote strong and durable partnerships among research institutions and with industry, going beyond the usual project-based cooperation. The purpose of this study is to investigate these long-lasting collaborative relationships between the organizations that received funds by all the first eight European Framework Programmes (EU FPs). EU FPs are multi-annual programmes providing funds mainly to EU member states, but also to associate countries, in order to promote long-term investments in several areas. Considering participations in European projects funded by all the first eight EU FPs gives us the possibility to analyze the dynamics of collaborations in the context of European research projects over a long-time span. In more detail, we adopt a novel approach to model the dynamics of participation in EU FPs by means of Social Network Analysis (SNA) and statistics tools. The main objective is to estimate the probabilities of moving from one position to another - in terms of centrality measures - across different FPs, and to understand if the position within subsequent collaborative research networks is affected by a certain path dependency. Our results confirm the existence of a path dependency, in the sense that participating in previous FPs provides a competitive advantage to organizations due to several network benefits, such as growing experience, competencies, and popularity. Phenomena of "preferential attachment" are also evident. Finally, we find that the estimated probability transition matrices are able to highlight relevant events that affected the European Union and its strategies in the field of research, which are the Treaty of Maastricht and the adoption of the European Research Area (ERA)

Existence of vanishing physical viscosity solutions of characteristic initial-boundary value problems for systems of conservation laws

We consider initial boundary-value problems for nonlinear systems of conservation laws in one space variable. It is known that in general different viscous mechanisms yield different solutions in the zero-viscosity limit. Here we focus on the most technically demanding case, known as boundary characteristic case, which occurs when one of the characteristic velocities of the system vanishes. We work in small total variation regimes and assume that every characteristic field is either genuinely nonlinear or linearly degenerate. We establish existence of admissible solutions satisfying a boundary condition consistent with the vanishing viscosity approximation given by a large class of physical (that is, mixed hyperbolic-parabolic) systems. In particular, our results apply to the zero-viscosity limit of the Navier-Stokes and viscous MHD equations, written in both Eulerian and Lagrangian coordinates. Our analysis relies on a fine boundary layers analysis and is based on the introduction of a new wave front-tracking algorithm. From the technical viewpoint, the most innovative elements are i) a new class of interaction estimates for boundary layers and boundary characteristic wave fronts hitting the boundary, which yields the introduction of a new Glimm-type functional; ii) a detailed analysis of the behavior of the wave front-tracking algorithm close to the boundary, which in turn yields relevant information on the limit.Comment: 78 pages, 5 figure

Network-based principles of entrepreneurial ecosystems: a case study of a start-up network.

Entrepreneurial ecosystems are wealthy environments in which entrepreneurs, firms, and governments can operate frictionless, contributing to innovation and economic growth. The investigation of the structure of such systems is an open issue. We provide insights on this aspect through the formulation of seven network-based principles associating specific network metrics to distinct structural features of entrepreneurial ecosystems. In this way, we aim to support the measurement of the structural characteristics of an entrepreneurial ecosystem and the design of policy interventions in case of unmet properties. The proposed methodology is applied to an original network built on the relationships occurring on Twitter among 612 noteworthy start-ups from seven different European countries. This is a novel way to conceptualize entrepreneurial ecosystems considering online interactions. Thus, this work represents a first attempt to analyze the structure of entrepreneurial ecosystems considering their network architecture to guide policy-making decisions. Our results suggest a partial ecosystem-like nature of the analyzed network, providing evidence about possible policy recommendations

Low temperature district heating networks for complete energy needs fulfillment

In order to reduce fossil fuels consumption and pollutant emissions, high contribution is given by district heating. In particular, the integration with renewable energy may lead to a significant increase in energy conversion efficiency and energy saving. Further benefits can be achieved with low temperature district heating, reducing the thermal dissipations through the network and promoting the exploitation of low enthalpy heat sources. The aim of the paper is the analysis of the potential related to the conversion of existing district heating networks, to increase the exploitation of renewable sources and eliminate pollutant emissions in the city areas. Further aim, in this context, is the optimization – from both energy production and operation management viewpoints – of a low temperature district heating network for the fulfillment of the connected users’ energy needs. To this respect, a traditional network with a fossil fuel driven thermal production plant has been considered and compared with a low temperature district heating scenario, including geothermal heat pumps, photovoltaic panels and absorption chillers. These scenarios have been analyzed and optimized with an in-house developed software, allowing to demonstrate the reduction of primary energy consumption and CO2 pollutant emissions achievable with low temperature networks. In addition, a preliminary economic evaluation has been carried out to compare the proposed solution with traditional district heating

Improving dispersal of therapeutic nanoparticles in the human body

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The Synergistic Effect of Nanocrystals Combined With Ultrasound in the Generation of Reactive Oxygen Species for Biomedical Applications

Reactive oxygen species (ROS) effects on living cells and tissues is multifaceted and their level or dose can considerably affect cell proliferation and viability. It is therefore necessary understand their role also designing ways able to regulate their amount inside cells, i.e., using engineered nanomaterials with either antioxidant properties or, for cancer therapy applications, capable to induce oxidative stress and cell death, through tunable ROS production. In this paper, we report on the use of single-crystalline zinc oxide (ZnO) round-shaped nanoparticles, yet ZnO nanocrystals (NCs) functionalized with amino-propyl groups (ZnO-NH2 NCs), combined with pulsed ultrasound (US). We show the synergistic effects produced by NC-assisted US which are able to produce different amount of ROS, as a result of inertial cavitation under the pulsed US exposure. Using Passive Cavitation Detection (PCD) and Electron Paramagnetic Resonance (EPR) spectroscopy, we systematically study which are the key parameters, monitoring, and influencing the amount of generated ROS measuring their concentration in water media and comparing all the results with pure water batches. We thus propose a ROS generation mechanism based on the selective application of US to the ZnO nanocrystals in water solutions. Ultrasound B-mode imaging is also applied, proving in respect to pure water, the enhanced ecographic signal generation of the aqueous solution containing ZnO-NH2 NCs when exposed to pulsed ultrasound. Furthermore, to evaluate the applicability of ZnO-NH2 NCs in the biomedical field, the ROS generation is studied by interposing different tissue mimicking materials, like phantoms and ex vivo tissues, between the US transducer and the sample well. As a whole, we clearly proof the enhanced capability to produce ROS and to control their amount when using ZnO-NH2 NCs in combination with pulsed ultrasound anticipating their applicability in the fields of biology and health care