Biofilm formation and Biocide resistance in Listeria

La presente attività di ricerca ha avuto come oggetto di studio la formazione di biofilm in condizioni dinamiche: per raggiungere tale obiettivo, è stato costruito un idoneo apparato che permettesse di ottenere una valutazione quantitativa sia delle cellule presenti nella soluzione di crescita sia di quelle adese su tre materiali di prova(acciaio inossidabile, PET e rame). Oltre ad esprimere una valutazione dell’adesione batterica alle superfici, si è proceduto ad indagare sui possibili parametri sperimentali che potessero influenzare la formazione di biofilmdi Listeria su superfici abiotiche. Allo stesso tempo l’efficacia battericida di alcuni biocidi è stata valutata sulle cellule planctoniche così come su biofilm batterici sviluppati su superfici abiotiche. Il ruolo del sistema di quorum sensing basato su luxS nella formazione di biofilm batterici: un ceppo di L. innocua con buone capacità adesive è stato confrontato con il suo ceppo deficiente di luxS per la sua suscettibilità ad agenti biocidi così come per la sua capacità di adesione superficiale L’effetto della precendentemente menzionata inattivazione genetica sulla cinetica di crescita batterica e, quindi, sull’efficienza metabolica complessiva è stata esaminate mediante lo strumento BioscreenC. L’effetto inibitorio di due composti polifenolici è stato valutato sul ceppo deficiente di luxS così come sul ceppo originale.The current research activity was focused on biofilm formation in dynamic conditions. A suitable device was thus constructed, in order to have a quantitative evaluation of the cells freely suspended in the flowing nutrient solution used as well as the sessile cells which adhered on the three tested surfaces (stainless steel, polyethylene therephthalate and copper). During this project, other than of a quantitative assessment of bacterial adhesion, we investigated also on the parameters which could affect significantly the biofilm formation of Listeria on abiotic surfaces. At the same time antimicrobial efficiency of selected biocides was investigated on planktonic cells as well as on bacterial biofilms grown on abiotic surfaces. The role of luxS-based quorum sensing system in the biofilm development process was evaluated: a luxS-null mutant of an adhesive strain of L. innocua was obtained through Campbell-like genetic inactivation and then evaluated for its sensitivity to biocidal agents and adhesion to surfaces, in comparison with its parental strains. Furthermore the effect of genetic inactivation on bacterial growth kinetic and thus on overall bacterial metabolic efficiency was assessed through the apparatus of BioscreenC. Finally two polyphenolic compounds were investigated for their inhibitory effect on Listeria

Generalized Analysis and Unified Design of EM Skins

A generalized formulation is derived for the analysis of the field manipulation properties of electromagnetic skins (EMSs) in the working regimes of interest for wireless communications. Based on such a theoretical framework, a unified method for the design of anomalous-reflecting and focusing EMSs is presented. Representative results, from a wide set of numerical experiments, are reported and validated with full-wave HFSS simulations to give the interested readers some insights on the accuracy, the effectiveness, and the computational efficiency of the proposed analysis/synthesis tools

Seismic amplification in presence of topography and their consequences for ground motion predictions and seismic code for building: the case of Italy

This work talks about the relevance of topographic effects in local site response evaluations. In this way some Italian test sites, characterized by the presence of a seismic station installed at the top of a steep topography, were investigated. The influence of the morphology was evaluated, at first, by performing rotational spectral ratio analyses, both in term of single station measurements (i.e. horizontal to vertical spectral ratio, HVSR) and, if possible, also considering reference sites (i.e.standard spectral ratio, SSR) and, at second, evaluating the residuals (logarithmic difference between observed and predicted data) estimated in term of acceleration response spectra for period up to 2.0 s. In this way, the ground motion prediction equations calibrated for Italy by Bindi et al., 2010 were considered. Finally, in correspondence of two selected topographies with seismic stations installed both at the top and at the base, the design elastic acceleration response spectra as proposed by the Italian seismic regulations (NTC, 2008) were evaluated in terms of shape and amplitude

Velocity profile report at the seismic station IV.MODE - MODENA

In this report, we present the geophysical measurements and the results obtained in the framework of the 2018 agreement between INGV and DPC, called Allegato B2: Obiettivo 1 - TASK B: Caratterizzazione siti accelerometrici (Coord. G. Cultrera, F. Pacor). In this report, the results for station IV.MODE, belonging to the Italian National Seismic Network (RSN-INGV), are presented. Geophysical measurements consist in a 2D array in passive configuration that provide results in terms of dispersion curves of surface waves. These curves are inverted to obtain a shear-wave velocity (Vs) profile that is suitable for assigning the soil class according to the current Italian seismic code (NTC 2018) and the current Eurocode (EC8)

Learned Global Optimization for Inverse Scattering Problems -- Matching Global Search with Computational Efficiency

The computationally-efficient solution of fully non-linear microwave inverse scattering problems (ISPs) is addressed. An innovative System-by-Design (SbD) based method is proposed to enable, for the first time to the best of the authors knowledge, an effective, robust, and time-efficient exploitation of an evolutionary algorithm (EA) to perform the global minimization of the data-mismatch cost function. According to the SbD paradigm as suitably applied to ISPs, the proposed approach founds on (i) a smart re-formulation of the ISP based on the definition of a minimum-dimensionality and representative set of degrees-of-freedom (DoFs) and on (ii) the artificial-intelligence (AI)-driven integration of a customized global search technique with a digital twin (DT) predictor based on the Gaussian Process (GP) theory. Representative numerical and experimental results are provided to assess the effectiveness and the efficiency of the proposed approach also in comparison with competitive state-of-the-art inversion techniques

Towards Real-World Indoor Smart Electromagnetic Environments -- A Large-Scale Experimental Demonstration

To the best of the authors' knowledge, this work presents the first large-scale indoor experimental assessment of an implementation of the emerging Smart ElectroMagnetic Environment (SEME) paradigm, which is based on the deployment of static-passive EM skins (SP-EMSs) to enhance the coverage in a 5 [GHz] Wi-Fi network. Unlike standard (laboratory-based) validations reported in the state-of-the-art (SoA) literature, the scenario at hand mimics a realistic indoor environment to replicate as close as possible the user experience when using commodity devices. Representative results from the experimental field trials are re-ported to confirm the performance predictions arising from the numerical studies and the tolerance analyses carried out with a commercial ray-tracing (RT) tool. Besides experimentally validating the SEME idea, this study is also aimed at (roughly) quantifying the economic advantage of a SEME implementation, relying on simple-manufacturing/low-cost field manipulating devices without any additional biasing circuitry, with respect to standard approaches that imply the densification of the active radiating sources

Multi-Resolution Subspace-Based Optimization Method for the Retrieval of 2D Perfect Electric Conductors

Perfect Electric Conductors (PECs) are imaged integrating the subspace-based optimizationmethod (SOM) within the iterative multi-scaling scheme (IMSA). Without a-priori information on the number or/and the locations of the scatterers and modelling their EM scattering interactions with a (known) probing source in terms of surface electric field integral equations, a segment-based representation of PECs is retrieved from the scattered field samples. The proposed IMSA-SOM inversion method is validated against both synthetic and experimental data by assessing the reconstruction accuracy, the robustness to the noise, and the computational efficiency with some comparisons, as well

Topographic Effects in Probabilistic Seismic Hazard Analysis: The Case of Narni, Central Italy

This study presents a probabilistic method for estimating the ground motion hazard at sites presenting topographic irregularities. This method is applicable to topographic crests or ridges which may affect site response, producing 2D (or 3D) amplification effects. The method is based on a set of 2D numerical analyses that are carried out using multiple accelerograms from worldwide weak and strong earthquakes recorded on rock. Numerical analyses are performed to compute site-specific frequency-dependent amplification factors to be included into the ground motion prediction equation used in the seismic hazard computation. The hazard at the top of the ridge is then assessed by running a conventional probabilistic seismic hazard analysis (PSHA) with the attenuation relationship modified to include the site response. An application to the case study of Narni (Central Italy) is presented in this work