Optimization of Reconfigurable Intelligent Surfaces with Electromagnetic Field Exposure Constraints

This work tackles the problem of maximizing the achievable rate in a reconfigurable intelligent surface (RIS)-assisted communication link, by enforcing conventional maximum power constraints and additional constraints on the maximum exposure to electromagnetic radiations of the end-users. The RIS phase shift matrix, the transmit beamforming filter, and the linear receive filter are jointly optimized, and two provably convergent and low-complexity algorithms are developed. One algorithm can be applied to general system setups, but does not guarantee global optimality. The other is shown to be provably optimal in the special case of isotropic electromagnetic exposure constraints. The numerical results show that RIS-assisted communications can ensure high data rate transmissions while guaranteeing users' exposure constraints to radio frequency emissions

Dynamic behaviour of HPFRCC: The influence of fibres dispersion

The promise of fibre-reinforced cementitious composites for dynamic loading application stems from their observed good response under static loading mainly due to fibre contribution. An experimental research aimed at contributing to the understanding of the behaviour of advanced fibre-reinforced cementitious composites subjected to low and high strain rates was carried out underlining the influence of fibres. The material behaviour was investigated at three strain rates (0.1, 1, and 150 s−1) and the tests results were compared with their static behaviour. Tests at intermediate strain rates (0.1–1 s −1) were carried out by means of a hydro-pneumatic machine (HPM), while high strain rates (150 s−1) were investigated by exploiting a modified Hopkinson bar (MHB). Particular attention has been placed on the influence of fibre and fibre dispersion on the dynamic behaviour of the materials: matrix, HPFRCC with random fibre distribution and aligned fibres were compared. The comparison between static and dynamic tests highlighted several relevant aspects regarding the influence of fibres on the peak strength and post-peak behaviour at high strain rate

MicroRNAs from saliva of anopheline mosquitoes mimic human endogenous miRNAs and may contribute to vector-host-pathogen interactions

During blood feeding haematophagous arthropods inject into their hosts a cocktail of salivary proteins whose main role is to counteract host haemostasis, inflammation and immunity. However, animal body fluids are known to also carry miRNAs. To get insights into saliva and salivary gland miRNA repertoires of the African malaria vector Anopheles coluzzii we used small RNA-Seq and identified 214 miRNAs, including tissue-enriched, sex-biased and putative novel anopheline miRNAs. Noteworthy, miRNAs were asymmetrically distributed between saliva and salivary glands, suggesting that selected miRNAs may be preferentially directed toward mosquito saliva. The evolutionary conservation of a subset of saliva miRNAs in Anopheles and Aedes mosquitoes, and in the tick Ixodes ricinus, supports the idea of a non-random occurrence pointing to their possible physiological role in blood feeding by arthropods. Strikingly, eleven of the most abundant An. coluzzi saliva miRNAs mimicked human miRNAs. Prediction analysis and search for experimentally validated targets indicated that miRNAs from An. coluzzii saliva may act on host mRNAs involved in immune and inflammatory responses. Overall, this study raises the intriguing hypothesis that miRNAs injected into vertebrates with vector saliva may contribute to host manipulation with possible implication for vector-host interaction and pathogen transmission

System-Level Modeling and Optimization of the Energy Efficiency in Cellular Networks -- A Stochastic Geometry Framework

In this paper, we analyze and optimize the energy efficiency of downlink cellular networks. With the aid of tools from stochastic geometry, we introduce a new closed-form analytical expression of the potential spectral efficiency (bit/sec/m$^2$). In the interference-limited regime for data transmission, unlike currently available mathematical frameworks, the proposed analytical formulation depends on the transmit power and deployment density of the base stations. This is obtained by generalizing the definition of coverage probability and by accounting for the sensitivity of the receiver not only during the decoding of information data, but during the cell association phase as well. Based on the new formulation of the potential spectral efficiency, the energy efficiency (bit/Joule) is given in a tractable closed-form formula. An optimization problem is formulated and is comprehensively studied. It is mathematically proved, in particular, that the energy efficiency is a unimodal and strictly pseudo-concave function in the transmit power, given the density of the base stations, and in the density of the base stations, given the transmit power. Under these assumptions, therefore, a unique transmit power and density of the base stations exist, which maximize the energy efficiency. Numerical results are illustrated in order to confirm the obtained findings and to prove the usefulness of the proposed framework for optimizing the network planning and deployment of cellular networks from the energy efficiency standpoint.Comment: To appear in IEEE Transactions on Wireless Communication

La grande scommessa. Turismo e pandemia a Firenze.

This paper is centred on the analysis of some recent developments of the touristic system in the italian city of Firenze. The COVID-19 pandemic hit hard the urban economic system of the city, which is increasingly dependent on tourism. We analyze how the pandemic has been exploited by some local actors to develop their own narrative of the touristic future of the city, in light of a rebranding attempt meant to position it as an «elite» touristic destination. We explore the contradictions between different ideas of how tourism should affect the urban fabric

The spread of multi drug resistant infections is leading to an increase in the empirical antibiotic treatment failure in cirrhosis: a prospective survey

Background The spread of multi-resistant infections represents a continuously growing problem in cirrhosis,particularly in patients in contact with the healthcare environment. Aim Our prospective study aimed to analyze epidemiology, prevalence and risk factors of multiresistant infections, as well as the rate of failure of empirical antibiotic therapy in cirrhotic patients. Methods All consecutive cirrhotic patients hospitalized between 2008 and 2013 with a microbiologically-documented infection (MDI) were enrolled. Infections were classified as Community- Acquired (CA), Hospital-Acquired (HA) and Healthcare-Associated (HCA). Bacteria were classified as Multidrug-Resistant (MDR) if resistant to at least three antimicrobial classes, Extensively-Drug-Resistant (XDR) if only sensitive to one/two classes and Pandrug-Resistant (PDR) if resistant to all classes. Results One-hundred-twenty-four infections (15% CA, 52% HA, 33% HCA) were observed in 111 patients. Urinary tract infections, pneumonia and spontaneous bacterial peritonitis were the more frequent. Forty-seven percent of infections were caused by Gram-negative bacteria. Fifty-one percent of the isolates were multi-resistant to antibiotic therapy (76% MDR, 21% XDR, 3% PDR): the use of antibiotic prophylaxis (OR = 8.4; 95%CI = 1.03-76; P = 0,05) and current/recent contact with the healthcare-system (OR = 3.7; 95%CI = 1.05-13; P = 0.04) were selected as independent predictors. The failure of the empirical antibiotic therapy was progressively more frequent according to the degree of resistance. The therapy was inappropriate in the majority of HA and HCA infections. Conclusions Multi-resistant infections are increasing in hospitalized cirrhotic patients. A better knowledge of the epidemiological characteristics is important to improve the efficacy of empirical antibiotic therapy. The use of preventive measures aimed at reducing the spread of multi-resistant bacteria is also essential

String Stability of a Vehicular Platoon with the use of Macroscopic Information

We investigate the possibility to use macroscopic information to improve control performance of a vehicular platoon composed of autonomous vehicles. A general mesoscopic traffic modeling is described, and a closed loop String Stability analysis is performed using Input-to-State Stability (ISS) results. Examples of mesoscopic control laws are provided and shown to ensure String Stability properties. Simulations are implementedin order to validate the control laws and to show the efficacy of the proposed approach.Comment: arXiv admin note: substantial text overlap with arXiv:2003.1252