A ring-like accretion structure in M87 connecting its black hole and jet.

The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole3. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of [Formula: see text] Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.

Towards the definition of WEEE recycling targets in Ecuador. A case of study for mobile phones.

The rise of consumption patterns of electrical and electronic equipment (EEE) and the generation of waste EEE (WEEE) has been strongly increasing globally. Recycling rates (RRs) are one of the main indicators for monitoring the progress towards a circular economy and establishing recovery and treatment schemes. For this reason, this study discusses the setting of recycling targets for WEEE in Ecuador, using mobile phones as a case study. Firstly, the generation of mobile phone waste from 2012 to 2018 is estimated based on literature review. The most appropriate model for estimating WEEE generation is selected according to the applicable market conditions, input requirements and available data. Then, the composition of a mobile phone is determined through an extensive literature review. Based on these results, the materials' environmental impact and potential economic value are approximated using the ReCiPe Endpoint (H, A) method and the prices of virgin materials, respectively. The estimation shows that in Ecuador an average of 2 million devices are discarded every year, which represents an interesting source of resources but currently does not have appropriate management. Ecuador has implemented regulatory frameworks in favour of the integral management of these wastes. However, mass-based collection targets still appear to be the only available measure. Therefore, national results on electronics recycling do not allow adequate monitoring of progress towards a circular economy and largely neglect environmental aspects and economic potential.

Theoretical study of spodium bonding in the active site of three Zn-proteins and several model systems.

In this manuscript, three examples retrieved from the PDB are selected to demonstrate the existence and relevance of spodium bonding (SpB) in biological systems. SpB is defined as an attractive noncovalent interaction between elements of group 12 of the periodic table acting as a Lewis acid and any atom or group of atoms acting as an electron donor. The utilization of this term (SpB) is convenient to differentiate classical coordination bonds from noncovalent interactions. In the latter, the distance between the electron rich and the spodium atoms is longer than the sum of the covalent radii but shorter than the sum of the van der Waals radii. In most Zn-dependent metalloenzymes, the spodium atom is bonded to three imidazole moieties belonging to the side chains of histidine amino-acids. Herein, in addition to the investigation of the SpB in the active site of three exemplifying enzymes, theoretical models where the Zn(ii) atom is bonded either to three imidazole or triazole ligands are used in order to investigate the strength of the SpB and its competition with hydrogen bonding. A series of Lewis bases and anions have been used as SpB acceptors combined with six SpB donors (receptors) of general formula [ZnY3X]+ (Y = imidazole and triazole and X = Cl, N3 and SCH3). In addition to the investigation of the energetic and geometric features of the complexes, the SpB interactions have been further characterized using the natural bond orbital (NBO) method, quantum theory of "atoms-in-molecules" and the noncovalent interaction plot (NCI plot).

Cellular and Virtualization Technologies for UAVs: An Experimental Perspective.

The Unmanned Aircraft System (UAS) ecosystem is exponentially growing in both recreational and professional fields to provide novel services and applications to consumers from multiple engineering fields. However, this technology has only scraped the surface of its potential, especially in those cases that require fast reaction times. Accordingly, the UAS Traffic Management (UTM) project aims at efficiently managing the air traffic for Unmanned Aerial Vehicle (UAV) operations, including those cases where UAVs might be remotely managed from a completely different geographical location. With these considerations in mind, this article presents a cellular-assisted UAVs testbed used to complete a mission managed beyond the radio line-of-sight (BRLoS), as well as introducing a virtualization platform for deploying services using containerization technology. In addition, the article conducts a communication performance evaluation in order to determine if the testbed equipment meets the requirements to carry out this BRLoS management. Finally, indoor flight operations are carried out to demonstrate the feasibility and proper operation of the testbed.

Deploying an NFV-Based Experimentation Scenario for 5G Solutions in Underserved Areas.

Presently, a significant part of the world population does not have Internet access. The fifth-generation cellular network technology evolution (5G) is focused on reducing latency, increasing the available bandwidth, and enhancing network performance. However, researchers and companies have not invested enough effort into the deployment of the Internet in remote/rural/undeveloped areas for different techno-economic reasons. This article presents the result of a collaboration between Brazil and the European Union, introducing the steps designed to create a fully operational experimentation scenario with the main purpose of integrating the different achievements of the H2020 5G-RANGE project so that they can be trialed together into a 5G networking use case. The scenario encompasses (i) a novel radio access network that targets a bandwidth of 100 Mb/s in a cell radius of 50 km, and (ii) a network of Small Unmanned Aerial Vehicles (SUAV). This set of SUAVs is NFV-enabled, on top of which Virtual Network Functions (VNF) can be automatically deployed to support occasional network communications beyond the boundaries of the 5G-RANGE radio cells. The whole deployment implies the use of a virtual private overlay network enabling the preliminary validation of the scenario components from their respective remote locations, and simplifying their subsequent integration into a single local demonstrator, the configuration of the required GRE/IPSec tunnels, the integration of the new 5G-RANGE physical, MAC and network layer components and the overall validation with voice and data services.

Using Aerial and Vehicular NFV Infrastructures to Agilely Create Vertical Services.

5G communications have become an enabler for the creation of new and more complex networking scenarios, bringing together different vertical ecosystems. Such behavior has been fostered by the network function virtualization (NFV) concept, where the orchestration and virtualization capabilities allow the possibility of dynamically supplying network resources according to its needs. Nevertheless, the integration and performance of heterogeneous network environments, each one supported by a different provider, and with specific characteristics and requirements, in a single NFV framework is not straightforward. In this work we propose an NFV-based framework capable of supporting the flexible, cost-effective deployment of vertical services, through the integration of two distinguished mobile environments and their networks: small sized unmanned aerial vehicles (SUAVs), supporting a flying ad hoc network (FANET) and vehicles, promoting a vehicular ad hoc network (VANET). In this context, a use case involving the public safety vertical will be used as an illustrative example to showcase the potential of this framework. This work also includes the technical implementation details of the framework proposed, allowing to analyse and discuss the delays on the network services deployment process. The results show that the deployment times can be significantly reduced through a distributed VNF configuration function based on the publish-subscribe model.

Integration of 5G Experimentation Infrastructures into a Multi-Site NFV Ecosystem.

Network Function Virtualization (NFV) has been regarded as one of the key enablers for the 5th Generation of mobile networks, or 5G. This paradigm allows to reduce the dependence on specialized hardware to deploy telecommunications and vertical services. To this purpose, it relies on virtualization techniques to softwarize network functions, simplifying their development and reducing deployment time and costs. In this context, Universidad Carlos III de Madrid, Telefónica, and IMDEA Networks Institute have developed an NFV ecosystem inside 5TONIC, an open network innovation center focused on 5G technologies, enabling the creation of complex, close to reality experimentation scenarios across a distributed set of NFV infrastructures, which can be made available by stakeholders at different geographic locations. This article presents the protocol that has been defined to incorporate new remote NFV sites into the multi-site NFV ecosystem based on 5TONIC, describing the requirements for both the existing and the newly incorporated infrastructures, their connectivity through an overlay network architecture, and the steps necessary for the inclusion of new sites. The protocol is exemplified through the incorporation of an external site to the 5TONIC NFV ecosystem. Afterwards, the protocol details the verification steps required to validate a successful site integration. These include the deployment of a multi-site vertical service using a remote NFV infrastructure with Small Unmanned Aerial Vehicles (SUAVs). This serves to showcase the potential of the protocol to enable distributed experimentation scenarios.

Energy-Aware Management in Multi-UAV Deployments: Modelling and Strategies.

Nowadays, Unmanned Aerial Vehicles (UAV) are frequently present in the civilian environment. However, proper implementations of different solutions based on these aircraft still face important challenges. This article deals with multi-UAV systems, forming aerial networks, mainly employed to provide Internet connectivity and different network services to ground users. However, the mission duration (hours) is longer than the limited UAVs' battery life-time (minutes). This paper introduces the UAV replacement procedure as a way to guarantee ground users' connectivity over time. This article also formulates the practical UAV replacements problem in moderately large multi-UAV swarms and proves it to be an NP-hard problem in which an optimal solution has exponential complexity. In this regard, the main objective of this article is to evaluate the suitability of heuristic approaches for different scenarios. This paper proposes betweenness centrality heuristic algorithm (BETA), a graph theory-based heuristic algorithm. BETA not only generates solutions close to the optimal (even with 99% similarity to the exact result) but also improves two ground-truth solutions, especially in low-resource scenarios.

Automated Deployment of an Internet Protocol Telephony Service on Unmanned Aerial Vehicles Using Network Functions Virtualization.

The Network Function Virtualization (NFV) paradigm is one of the key enabling technologies in the development of the 5th generation of mobile networks. This technology aims to lessen the dependence on hardware in the provision of network functions and services by using virtualization techniques that allow the softwarization of those functionalities over an abstraction layer. In this context, there is increasing interest in exploring the potential of unmanned aerial vehicles (UAVs) to offer a flexible platform capable of enabling cost-effective NFV operations over delimited geographic areas. To demonstrate the practical feasibility of utilizing NFV technologies in UAV platforms, a protocol is presented to set up a functional NFV environment based on open source technologies, in which a set of small UAVs supply the computational resources that support the deployment of moderately complex network services. Then, the protocol details the different steps needed to support the automated deployment of an internet protocol (IP) telephony service over a network of interconnected UAVs, leveraging the capacities of the configured NFV environment. Experimentation results demonstrate the proper operation of the service after its deployment. Although the protocol focuses on a specific type of network service (i.e., IP telephony), the described steps may serve as a general guide to deploy other type of network services. On the other hand, the protocol description considers concrete equipment and software to set up the NFV environment (e.g., specific single board computers and open source software). The utilization of other hardware and software platforms may be feasible, although the specific configuration aspect of the NFV environment and the service deployment may present variations with respect to those described in the protocol.

Transport-Layer Limitations for NFV Orchestration in Resource-Constrained Aerial Networks.

In this paper, we identify the main challenges and problems related with the management and orchestration of Virtualized Network Functions (VNFs) over aerial networks built with Small Unmanned Aerial Vehicles (SUAVs). Our analysis starts from a reference scenario, where several SUAVs are deployed over a delimited geographic area, and provide a mobile cloud environment that supports the deployment of functions and services using Network Functions Virtualization (NFV) technologies. After analyzing the main challenges to NFV orchestration in this reference scenario from a theoretical perspective, we undertake the study of one specific but relevant aspect following a practical perspective, i.e., the limitations of existing transport-layer solutions to support the dissemination of NFV management and orchestration information in the considered scenario. While in traditional cloud computing environments this traffic is delivered using TCP, our simulation results suggest that using this protocol over an aerial network of SUAVs presents certain limitations. Finally, based on the lessons learned from our practical analysis, the paper outlines different alternatives that could be followed to address these challenges.

Enabling the Orchestration of IoT Slices through Edge and Cloud Microservice Platforms.

This article addresses one of the main challenges related to the practical deployment of Internet of Things (IoT) solutions: the coordinated operation of entities at different infrastructures to support the automated orchestration of end-to-end Internet of Things services. This idea is referred to as "Internet of Things slicing" and is based on the network slicing concept already defined for the Fifth Generation (5G) of mobile networks. In this context, we present the architectural design of a slice orchestrator addressing the aforementioned challenge, based on well-known standard technologies and protocols. The proposed solution is able to integrate existing technologies, like cloud computing, with other more recent technologies like edge computing and network slicing. In addition, a functional prototype of the proposed orchestrator has been implemented, using open-source software and microservice platforms. As a first step to prove the practical feasibility of our solution, the implementation of the orchestrator considers cloud and edge domains. The validation results obtained from the prototype prove the feasibility of the solution from a functional perspective, verifying its capacity to deploy Internet of Things related functions even on resource constrained platforms. This approach enables new application models where these Internet of Things related functions can be onboarded on small unmanned aerial vehicles, offering a flexible and cost-effective solution to deploy these functions at the network edge. In addition, this proposal can also be used on commercial cloud platforms, like the Google Compute Engine, showing that it can take advantage of the benefits of edge and cloud computing respectively.

Adaptable and Automated Small UAV Deployments via Virtualization.

In this paper, we present a practical solution to support the adaptable and automated deployment of applications of Small Unmanned Aerial Vehicles (SUAVs). Our solution is based on virtualization technologies, and considers SUAVs as programmable network platforms capable of executing virtual functions and services, which may be dynamically selected according to the requirements specified by the operator of the aerial vehicles. This way, SUAVs can be flexibly and rapidly adapted to different missions with heterogeneous objectives. The design of our solution is based on Network Function Virtualization (NFV) technologies, developed under the umbrella of the fifth generation of mobile networks (5G), as well as on existing Internet protocol standards, including flying ad hoc network routing protocols. We implemented a functional prototype of our solution using well-known open source technologies, and we demonstrated its practical feasibility with the execution of an IP telephony service. This service was implemented as a set of virtualized network functions, which were automatically deployed and interconnected over an infrastructure of SUAVs, being the telephony service tested with real voice-over-IP terminals.

Enabling Multi-Mission Interoperable UAS Using Data-Centric Communications.

We claim the strong potential of data-centric communications in Unmanned Aircraft Systems (UAS), as a suitable paradigm to enhance collaborative operations via efficient information sharing, as well as to build systems supporting flexible mission objectives. In particular, this paper analyzes the primary contributions to data dissemination in UAS that can be given by the Data Distribution Service (DDS) open standard, as a solid and industry-mature data-centric technology. Our study is not restricted to traditional UAS where a set of Unmanned Aerial Vehicles (UAVs) transmit data to the ground station that controls them. Instead, we contemplate flexible UAS deployments with multiple UAV units of different sizes and capacities, which are interconnected to form an aerial communication network, enabling the provision of value-added services over a delimited geographical area. In addition, the paper outlines an approach to address the issues inherent to the utilization of network-level multicast, a baseline technology in DDS, in the considered UAS deployments. We complete our analysis with a practical experience aiming at validating the feasibility and the advantages of using DDS in a multi-UAV deployment scenario. For this purpose, we use a UAS testbed built up by heterogeneous hardware equipment, including a number of interconnected micro aerial vehicles, carrying single board computers as payload, as well as real equipment from a tactical UAS from the Spanish Ministry of Defense.

Active galaxies. A strong magnetic field in the jet base of a supermassive black hole.

Active galactic nuclei (AGN) host some of the most energetic phenomena in the universe. AGN are thought to be powered by accretion of matter onto a rotating disk that surrounds a supermassive black hole. Jet streams can be boosted in energy near the event horizon of the black hole and then flow outward along the rotation axis of the disk. The mechanism that forms such a jet and guides it over scales from a few light-days up to millions of light-years remains uncertain, but magnetic fields are thought to play a critical role. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have detected a polarization signal (Faraday rotation) related to the strong magnetic field at the jet base of a distant AGN, PKS 1830-211. The amount of Faraday rotation (rotation measure) is proportional to the integral of the magnetic field strength along the line of sight times the density of electrons. The high rotation measures derived suggest magnetic fields of at least tens of Gauss (and possibly considerably higher) on scales of the order of light-days (0.01 parsec) from the black hole.