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In this paper, a hybrid control system (HCS) endowing a base isolation system (BIS) with a Tuned Mass Damper Inerter (TMDI) is proposed for the protection of steel storage tanks from severe structural damages induced by seismic events. Among all the components of industrial plants, cylindrical steel storage tanks are widely spread and play a primary role when subjected to seismic hazard, since they suffer of many critical issues related to their dynamic response such as high convective wave height and base shear force. The adopted base isolation system is realized with spring and damper elements, whereas the TMDI is realized with a tuned mass damper connected to the ground by the inerter. The developed mechanical model consists of a MDOF system, which considers the impulsive and convective modes as well as the TMDI dynamics. An optimal design problem is tackled, making use of a multi-objective approach, with the scope to mitigate simultaneously the convective and impulsive response of the storage tank. A zero mean white noise excitation is assumed as input in the optimal design procedure. Once the HCS is optimally designed, a systematic investigation of its seismic effectiveness is reached through parametric analysis. Modal parameters and frequency response functions are discussed. A literature case study comparing the effectiveness of the proposed optimally designed HCS with traditional base isolation is illustrated and performances are assessed through stochastic excitation and natural earthquakes.

Earthquake is one of the natural events which is part of NaTech events (Natural Hazard Triggering Technological Disasters), due to interaction between natural and industrial risks. Industrial plants employ cylindrical liquid tanks with floating roof for storage of volatile and flammable products. Damages due to earthquakes affecting tanks with floating roof can cause major accidents involving dangerous substances, like hazardous releases, fires and explosions, especially due to the convective motion of the fluid caused by seismic excitation. The aim of this work is to inform about the most common damages in case of seismic event and to give some advice to seismic risk management through monitoring of critical elements of liquid storage tanks with floating roof. During an earthquake, damages to structural and non-structural elements can occur, and the non-structural elements are often the most involved in major accidents. In order to mitigate the consequences of a major accident, a monitoring system of the tank for management of the seismic risk can be installed, integrating new dedicated sensors into the existing monitoring network. The fiber optic sensors FBG (Fiber Bragg Grating) and FSI (Fiber Segment Interferometry) are a robust, multifunctional and removable alternative to the sensors already in use in the industrial field.

Transplanted patients are particularly exposed to a major risk of infectious diseases due to prolonged immunosuppressive treatment. Over the last decade, the growing migration flows and the transplant tourism have led to increasing infections caused by geographically restricted organisms. Malaria is an unusual event in organ transplant recipients than can be acquired primarily or reactivation following immunosuppression, by transfusion of blood products or through the transplanted organ. We report a rare case of Plasmodium falciparum infection in a liver transplanted two years-old African boy who presented to one Italian Asylum Seeker Center on May 2019. We outlined hereby diagnostic challenges, possible aetiologies of post-transplantation malaria and finally we summarized potential drug interactions between immunosuppressive agents and antimalarials. This report aims to increase the attention to newly arrived migrants, carefully evaluating patients coming from tropical areas and taking into consideration also rare tropical infections not endemic in final destination countries.

During strong earthquakes, structural pounding may occur between structures and the surrounding moat wall because of the limited separation distance and the deformations of the isolator. An arrangement that favours the solution of this problem is the interposition of bumpers. Thus, the influence of geometrical and mechanical characteristics of isolation and mitigation devices on nonlinear non-smooth response of vibro-impact systems is experimentally and numerically investigated in this paper on the basis of a laboratory campaign of experimental tests and a numerical model. Shaking table tests are carried out under a harmonic excitation in order to investigate two different configurations: the absence and the presence of bumpers. For different values of the table acceleration peak are applied, four different amplitude values of the total gap between mass and bumpers are considered, and also four different types of bumpers are employed. The experimental response of the system is analysed in terms of table acceleration, gap clearance, bumpers’ stiffness, and pseudo-resonance frequency; a suitable normalization is adopted in order to better interpret experimental results; in particular, mass acceleration is normalized with respect to table acceleration and excursion is normalized with respect to gap. The signals of the system’s response are appropriately elaborated to verify the possibility of modifying the system’s response and direct it towards the (conflicting) objectives desired to simultaneously reduce displacements and accelerations. A suitable model has been developed to numerically simulate the behaviour of the system by using a general-purpose computer code, achieving a good agreement with the experimental results.

This paper illustrates the dynamics of a novel structural configuration represented by two adjacent single-degree-of-freedom (2-ASDOF) systems coupled by a connection with spring-dashpot-inerter elements arranged in parallel. The connection is conservative if the link is realized only with spring and/or inerter, whereas becomes nonconservative when also the dashpot is added. The first part of the study concerns the system modal analysis: different linking schemes are considered in order to investigate the influence of each connection parameter on the coupled system modal properties. It is shown that, for conservative connection, modal properties are analytically derived because the eigenvalue problem admits closed-form solutions. For nonconservative connection, instead, the state-space description is adopted and the complex modal analysis is carried out (deriving pseudo-frequencies, pseudo-damping factors and complex modes). Admissible and not-admissible zones for the frequencies of the coupled system are individuated: frequencies are positioned on the left, on the right or within the uncoupled ones, depending on the values chosen for the connection parameters. Associated to each case, typical patterns for mode shapes are depicted. Peculiar behaviors of the system, advantageous for structural control purposes, emerge when the connection parameters assume specific values. The second part of the paper illustrates the system dynamics to very simple input conditions: the response to free vibration with initial conditions and to base harmonic motion is carried out. Based on the findings obtained from modal analysis, it is highlighted that it is possible to properly select the connection parameters in order to have: (i) the most rapid decay of the structural response in case of free vibrations and (ii) the minimum response amplification for both oscillators in case of harmonic motion.

The large displacements caused by strong earthquakes in base-isolated structures (buildings, bridges, strategic facilities, equipment, ⋯ ) can excessively deform or damage the isolation system or lead to pounding with surrounding moat walls or adjacent structures, if the available seismic gap is not sufficient. The acceleration spikes caused by the impact can damage the structure itself as well as sensitive equipment housed in it. A possible mitigation measure consists in the interposition of deformable shock absorbers (bumpers). In this paper, the influence of the gap amplitude on the experimental response of a single-degree-of-freedom oscillator, excited by a harmonic base acceleration and symmetrically constrained by two unilateral deformable and dissipative bumpers, is investigated. The parametric investigation considered both positive, null, and negative gaps. Particular attention is paid to the study of the effect, on the system response, of the transition from positive to small negative gaps and of excessive negative gaps. Secondary resonances in the low frequency range, associated with the occurrence of multiple impacts, were experimentally observed for small positive gaps. Finally, the experimental results were reproduced, in a sufficiently accurate manner, using a suitable numerical model, whose parameters were identified based on the experimental data.

In recent years, inerter vibration absorbers (IVAs), such as the tuned mass damper inerter (TMDI), attracted much attention in the literature for reducing seismic displacement demands of base isolated structures (BISs). Several theoretical studies reported reduced BIS seismic demands with increasing inertance endowed by a grounded inerter element but adopted mostly idealized linear dynamical models. Herein, the potential of TMDI-configured IVAs for seismic response reduction of BISs modelled as single-mass structures is assessed under the combined effects of nonlinear inerter and structural behaviour. To this aim, experimental data from a shaking table testing campaign are considered utilizing a custom-built flywheel rack-and-pinion grounded inerter prototype with variable inertance along with high damping rubber bearings in the isolation layer and in the BIS-to-absorber link. White noise excitation and an ensemble of six ground motions (GMs) with different frequency content are used in the tests for which bearings exhibit softening nonlinear behaviour. Experimental results demonstrate improvement of BIS nonlinear seismic response in terms of displacement and base shear with increasing inertance for nonlinear and non-optimally designed TMDIs. It is found though that non-optimally tuned IVAs may be detrimental to BIS acceleration response depending on the GMs time-varying frequency content signatures as captured by the continuous wavelet transform spectrogram. Lastly, it is concluded that representing the inerter device by a simplified linear dissipative model as opposed to a nonlinear model with friction and gear backlash suffices to trace the BIS response with acceptable accuracy and, thus, can be used for optimal seismic TMDI design.

This paper presents preliminary experimental results from a novel shaking table testing campaign investigating the dynamic response of a two-degree-of-freedom (2DOF) physical specimen with a grounded inerter under harmonic base excitation and contributes a nonlinear dynamic model capturing the behavior of the test specimen. The latter consists of a primary mass connected to the ground through a high damping rubber isolator (HDRI) and a secondary mass connected to the primary mass through a second HDRI. Further, a flywheel-based rack-and-pinion inerter prototype device is used to connect the secondary mass to the ground. The resulting specimen resembles the tuned mass damper inerter (TMDI) configuration with grounded inerter analytically defined and numerically assessed by the authors in a number of previous publications. Physical specimens with three different inerter coefficients are tested on the shake table under sine-sweep excitation with three different amplitudes. Experimental frequency response functions (FRFs) are derived manifesting a softening nonlinear behavior of the specimens and enhanced vibration suppression with increased inerter coefficient. Further, a 2DOF parametric nonlinear model of the specimen is established accounting for non-ideal inerter device behavior and its potential to characterize experimental response time-histories, FRFs, and force-displacement relationships of the HDRIs and of the inerter is verified.

During strong earthquakes, base isolated systems (buildings, bridges, strategic facilities, equipment, etc.) can impact against the surrounding moat wall because of the deformation of the isolator if the available separation distance is limited. A possible mitigation measure is the interposition of shock absorbers. The aim of this work is to illustrate some of the results of an experimental laboratory campaign concerning the study of the dynamic response of a single-degree-of-freedom (SDOF) oscillator excited by a harmonic base acceleration and symmetrically constrained by two unilateral deformable and dissipative constraints (bumpers). Three different peak values of table acceleration, four amplitudes of the total gap between mass and bumpers, and four types of bumpers were considered. Among the various aspects investigated, particular attention was paid to the study of pseudo-resonance curves of maximum absolute acceleration and excursion of the SDOF oscillator and to the characterization of the hysteresis zone.

Nowadays, long-term monitoring systems rely on the efficient implementation of automated methodologies to extract the modal parameters of buildings and bridges to assess their structural integrity. However, modal parameter estimation, usually, requires a certain level of user interaction, mainly when parametric system identification methods are used. Such procedures generally depend on the selection of a set of parameters, defined according to heuristic criteria, and kept constant during long monitoring campaigns. The main objective of this paper is to prove the necessity of abandoning identification approaches based on a single set of parameters for long-term monitoring campaigns and to propose a semi-automated modal identification tool, where the user-defined parameters vary within an established range of values, that can be set independently of the user’s expertise. The proposed method is validated with an application in the operational modal analysis of a historic civic tower, and its excellent results demonstrate the importance of considering multiple sets of parameters, mainly when dealing with complex structures and challenging monitoring conditions.

Background Loiasis is a vector-borne parasitic infection endemic across many areas of Central and West Africa. Its treatment is tricky due to the risk of serious neurologic adverse events occurring after the administration of microfilaricidal drugs, like diethylcarbamazine or ivermectin, in subjects with high pre-treatment microfilarial load. Albendazole is currently recommended to slowly reduce microfilaremia before curative regimen is prescribed. Case presentation We report the case of a 25-year-old man from Guinea-Conakry who was incidentally diagnosed with highly microfilaremic Loa loa infection. A three weeks regimen of albendazole was prescribed. Minor neurologic side effects occurred after two weeks of administration, while serious encephalopathy developed one week later. Clinical and electroencephalographic features of the patient resembled those of an immune-mediated encephalitis. After exclusion of other causes of encephalopathy, treatment-related Loa loa encephalopathy induced by albendazole was suspected. Corticosteroid treatment was administered and the patient recovered. Discussion Our case confirms that Loa loa treatment-related encephalopathy may occur even during albendazole treatment. The clinical and electroencephalographic similarities between Loa loa albendazole-related encephalopathy and immune-mediated encephalitis suggest the possibility of an underlying inflammation-based pathogenesis. Although corticosteroid administration is not recommended in Loa loa ivermectin-induced encephalopathy, in this case of Loa loa albendazole-induced encephalopathy it may have played a therapeutic role.

In this paper, possible scenarios within the experimental dynamic response of a vibro-impact single-degree-of-freedom system, symmetrically constrained by deformable and dissipative bumpers, were identified and described. The different scenarios were obtained varying selected parameters, namely peak table acceleration $$\hbox {A}$$ , amplitude of the total gap between mass and bumpers $$\hbox {G}$$ and bumper’s stiffness $$\hbox {B}$$ . Subsequently, using a Simplified Nonlinear Model results in good agreement with the experimental outcomes were obtained, although the model includes only the nonlinearities due to clearance existence and impact occurrence. Further numerical analysis highlighted other scenarios that can be obtained for values of the parameters not considered in the experimental laboratory campaign. Finally, to attempt a generalization of the results, suitable dimensionless parameters were introduced.

During strong earthquakes, structural pounding may occur between the equipment and the surrounding moat wall because of the limited separation distance and the deformations of the isolator. A potential mitigation measure for this problem is the incorporation of collision bumpers. The aim of the paper is to study the experimental dynamic response and to formulate numerical model of a base-isolated SDOF oscillator excited by a harmonic base acceleration and symmetrically bounded by two unilateral deformable and dissipative constraints. Static tests have been first performed to determine the static characteristics and the support conditions of the bumpers, and successively, shaking table tests have been carried out to investigate two different configurations: the absence and the presence of bumpers. In both configurations, tests were carried out with the same type of excitation to the base. Different values of the table acceleration peak were applied, different amplitude values of the total gap between mass and bumpers were considered, and also two different types of bumpers were employed. The experimental dynamic responses in the absence and in the presence of bumpers have been compared, and the results obtained in the presence of bumpers have also been used to identify some characteristics of the dynamics with impact (force and time of contact between mass and bumpers, energy dissipated by the bumpers during the impact, and coefficient of restitution). A suitable model has been developed to numerically simulate the behavior of the system by using a general-purpose computer code, achieving a good agreement with the experimental results.

The study investigates the dynamic response of a viscously damped two adjacent single degree-of-freedom (2-ASDOF) system coupled by a connection that includes an inerter element. The dynamical model of a pair of simple oscillators coupled with various connection elements is synthetic but also representative to describe different classes of structures (i.e. contiguous buildings, adjacent walls and frames and so on). The specific kind of connection fundamentally alters the dynamic behavior of the entire system. Coupling elements typically studied are springs, dampers, linear or non-linear, passive, semi-active or active, e.g. [1,2]. The inerter is a novel device able to generate a resisting force, proportional to the relative acceleration of its terminals, equivalent to a force produced with an apparent (inertial) mass two orders of magnitude greater than its own physical (gravitational) mass [3]. In this study, a non-conservative connection, realized with a spring-inerter-viscous damper elements, adjusted in parallel, is considered as linking scheme for the 2-ASDOF system. In order to perform modal analysis, the first order state-space representation is adopted and the modal equations for the viscously damped system are derived. By solving the eigenvalue problem, the attention is focused on how modal parameters, i.e. the natural frequencies, the modal damping ratios and modes are affected by the connection. The system is then subject to harmonic base excitation and frequency response functions are depicted showing the influence of the link (through spring stiffness, inertance and damping coefficient) on the dynamic response. From the analysis with the different linking schemes, it emerges that the specific kind of connection influences the system dynamic characteristics.

Community-acquired pneumonia (CAP) is complicated by cardiovascular events as myocardial infarction and stroke but the underlying mechanism is still unclear. We hypothesized that endothelial dysfunction may be implicated and that endotoxemia may have a role.Fifty patients with CAP and 50 controls were enrolled. At admission and at discharge, flow-mediated dilation (FMD), serum levels of endotoxins and oxidative stress, as assessed by serum levels of nitrite/nitrate (NOx) and isoprostanes, were studied.At admission, a significant difference between patients with CAP and controls was observed for FMD (2.1±0.3 vs 4.0±0.3%, p0.001), serum endotoxins (157.8±7.6 vs 33.1±4.8pg/ml), serum isoprostanes (341±14 vs 286±10 pM, p=0.009) and NOx (24.3±1.1 vs 29.7±2.2μM). Simple linear correlation analysis showed that serum endotoxins significantly correlated with Pneumonia Severity Index score (Rs=0.386, p=0.006). Compared to baseline, at discharge CAP patients showed a significant increase of FMD and NOx (from 2.1±0.3 to 4.6±0.4%, p0.001 and from 24.3±1.1 to 31.1±1.5μM, p0.001, respectively) and a significant decrease of serum endotoxins and isoprostanes (from 157.8±7.6 to 55.5±2.3pg/ml, p0.001, and from 341±14 to 312±14 pM, p0.001, respectively). Conversely, no changes for FMD, NOx, serum endotoxins and isoprostanes were observed in controls between baseline and discharge. Changes of FMD significantly correlated with changes of serum endotoxins (Rs=-0.315; p=0.001).The study provides the first evidence that CAP is characterized by impaired FMD with a mechanism potentially involving endotoxin production and oxidative stress.

Background Blastocystis is one of the most common intestinal protozoa in human faecal samples with uncertain impact on public health. Studies on the prevalence of Blastocystis in HIV-positive patients are limited and dated. Methods A cross-sectional study was carried out involving 156 HIV-positive patients to evaluate the prevalence of Blastocystis-subtypes by molecular amplification and sequencing the small subunit rRNA gene (SSU rDNA), to identify the risk factors for its transmission, to examine the relationship between the presence of the protist and gastrointestinal disorders. Furthermore, the evaluation of the faecal calprotectin by immunoassay from a sample of subjects was performed to evaluate the gut inflammation in Blastocystis-carriers. Results Blastocystis-subtypes ST1, ST2, ST3, ST4 were identified in 39 HIV-positive patients (25%). No correlation was found between the presence of the protist and virological or epidemiological risk factors. Blastocystis was more frequently detected in homosexual subjects (p = 0.037) infected by other enteric protozoa (p = 0.0001) and with flatulence (p = 0.024). No significant differences in calprotectin level was found between Blastocystis-carriers and free ones. Conclusions Blastocystis is quite common in HIV-positive patients on ART showing in examined patients 25% prevalence. Homosexual behaviour may represent a risk factor for its transmission, while CD4 count and viremia didn’t correlate with the presence of the protist. The pathogenetic role of Blastocystis remains unclear and no gut inflammation status was detected in Blastocystis-carriers. The only symptom associated with Blastocystis was the flatulence, evidencing a link between the presence of the protist and the composition and stability of gut microbiota.

Adults hospitalized for community-acquired pneumonia (CAP) have an increased risk of myocardial infarction. Corticosteroid treatment lowers CAP morbidity and mortality, but it is not known whether it influences in-hospital myocardial infarction.The aim of the present study was to investigate the potential interplay between corticosteroid treatment and in-hospital myocardial infarction in adults with CAP.We retrospectively analyzed adults with CAP referred to the University Hospital Policlinico Umberto I (Rome, Italy), consecutively recruited, and prospectively followed until discharge. The primary outcome was the occurrence of myocardial infarction during hospitalization. We used propensity score-adjusted Cox models to examine the association between corticosteroid use and myocardial infarction.Seven hundred fifty-eight patients (493 males, 265 females; mean ± standard deviation age, 71.7 ± 14.4 yr) were included in the study. Of these, 241 (32%) were treated with systemic corticosteroids (methylprednisolone, betamethasone, or prednisone). During follow-up, 62 (8.2%) had a myocardial infarction during their hospitalization (incidence, 0.72 per 100 person-days; 95% confidence interval [CI], 0.55 to 0.92). Those treated with corticosteroids had a lower incidence of myocardial infarction (0.42 per 100 person-days) than those not treated with corticosteroids (0.89 per 100 person-days; absolute rate difference, -0.48 per 100 person-days; 95% CI, -0.85 to -0.10). In a propensity score-adjusted Cox model, corticosteroid use was associated with a lower incidence of myocardial infarction (hazard ratio, 0.46; 95% CI, 0.24 to 0.88; P = 0.02).We found that in-hospital corticosteroid treatment was associated with a lower incidence of myocardial infarction in adults hospitalized with CAP.

In this paper, the concept of an ideal grounded linear inerter, endowing supplemental inertia to passive linear tuned mass-dampers (TMDs) through its inertance property without increasing the TMD mass, is considered to reduce lateral displacement demands in base isolated structural systems (BISs). Optimal tuned mass-damper-inerter (TMDI) design parameters are numerically determined to maximize energy dissipation by the TMDI under stationary white noise support excitation. Performance of these optimally designed TMDI-equipped BISs is assessed for stationary white and colored noise excitations as well as for four recorded earthquake acceleration ground motions (GMs) with different non-stationary frequency content. It is found that for fixed mass ratio the inclusion of the grounded inerter reduces significantly secondary mass displacement and stroke for all considered excitations while it improves appreciably BIS displacement demands except for the particular case of a near-fault accelerogram characterized by early arrival of a high-energy low-frequency pulse as captured in its wavelet spectrogram. More importantly, it leads further to reductions to BIS acceleration demands with the exception of colored noise excitation for which an insignificant increase is noted. The positive effects of the inerter saturate with increasing inertance and BIS damping ratio demonstrating that small inertance values are more effective in vibration suppression of BISs with low inherent damping. Overall, it is recommended to combine low damping isolation layers with large inertance and low secondary mass TMDIs.

The paper deals with the analytical formulation of two adjacent single degree of freedom systems coupled by spring-dashpot-inerter elements adequately tuned in order to build a defective system. From modal analysis analytical expressions of eigenvalues, damping factor and connection parameters in order to build defective systems are given. It is demonstrated that is always possible to realize a defective system when a connection with spring-dashpot-inerter elements is utilized, irrespectively of the assumed structural parameters. Given a couple of oscillators, it is possible to build infinite defective systems by conveniently varying one parameter of the connection, chosen as independent variable. Among the feasible choices of parameters, a design criterion for the connection is proposed maximizing the modal damping factor and closed-form expressions of the design parameters are carried out. Maps of the natural frequency, damping factor and the damped frequency of the defective system with maximum modal damping factor are furnished. A procedure to obtain the eigenvectors forming a complete base to compute the system response analytically is given. For these systems, the response to free vibration with initial conditions and to base harmonic motion is investigated. The main characteristics of the response are discussed and considerations about the dynamics and effectiveness of the connection for control purposes are outlined.

The paper illustrates a methodology to perform the optimal design of a Tuned Mass Damper Inerter (TMDI) equipped on a multi degree of freedom (MDOF) structure through a generalized model. The TMDI is considered in both configurations grounded and ungrounded. A generalized 2-DOF model is obtained: the primary oscillator, representing the original MDOF structure and the secondary oscillator, representing the control system. A Gaussian zero mean white noise random process is adopted for the excitation. The TMDI design is carried out adopting an energy objective function, maximized over the space of the design parameters which are: the mass and inertance ratios, the frequency ratio, the damping factor and a parameter that accounts for the TMDI location on the MDOF structure. Synthetic performance-based design maps of the TMDI parameters are carried out. It is shown that is possible to have different design configurations to achieve a target performance level. The maps furnish, as limit cases, the design of a Tuned Inerter Damper (TID) and a Tuned Mass Damper (TMD), when the mass or the inertance ratios are respectively assumed null. It is shown straightforwardly the regions of the design parameters where the inerter enhances the performances achievable by classical TMD. Furthermore, an analytical expression which links the optimal design variables necessary to obtain a desired target performance is proposed. Frequency response functions and modal parameters of certain 2-DOF models with optimally designed control system are reported and considerations on how the design parameters influence the system dynamics and the damping capabilities are highlighted. Comparisons of the TMDI optimally designed with cases of no control and same mass TMD are evidenced throughout the paper. Finally, the main responses of the primary structure and the TMDI are estimated in the space of variation of the design parameters in order to assess the effectiveness of the control system.

The aim of this paper was to study the dynamic response of a single-degree-of-freedom (SDOF) oscillator exited by a base acceleration and constrained by two unilateral constraints (bumpers). The coupled equations of motion are formulated in dimensional and dimensionless form for the case in which both SDOF oscillator and bumpers exhibit a nonlinear behavior. Two possible states characterize the system’s response: flight, when the mass of the oscillator is not in contact with the bumper, and contact, when the mass touches the bumper. When the system is in the flight state, the independent time evolution of the bumpers’ response is also considered in equations of motion. In the numerical investigations, a viscoelastic SDOF oscillator and viscoelastic perfectly plastic bumpers subjected to a harmonic base excitation are considered. First, the transient versus steady-state dynamic response is considered, and afterward the only steady-state dynamic response is studied by means of pseudo-resonance curves of maximum absolute acceleration and relative displacement excursion of the SDOF oscillator. Furthermore, the continuation technique is applied in some cases in order to highlight in the system’s dynamic response hysteresis ranges, jumps between multi-periodic orbits, and super-harmonics. The dynamic analysis with and without bumpers is compared to observe how unilateral constraints modify the dynamic response of the SDOF oscillator with respect to the absence of bumpers and when their presence may be beneficial with respect to response mitigation.

This paper considers a novel shaking table testing campaign to assess the tuned mass-damper-inerter (TMDI) vibrations suppression attributes in harmonically excited structures under the combined effect of nonlinear structural response and nonlinear inerter device behavior deviating from the ideal linear inerter element developing acceleration-dependent force proportional to the inertance constant. Physical specimens of TMDI-equipped single-degree-of-freedom (SDOF) structure are considered featuring a custom-built rack-and-pinion flywheel inerter device with nonlinear behavior due to friction and backlash effects to connect the TMDI secondary mass to the ground. Damping and elastic properties are endowed to the SDOF structure and to the TMDI via high damping rubber bearings (HDRBs) exhibiting softening nonlinear elastic behaviour. Comprehensive experimental data in time and frequency domains are presented for 9 specimens with different sets of secondary mass and inertance subject to sine-sweep excitations for three different amplitudes. The data demonstrate that the main practical advantage of the TMDI established in the literature for linear structures and ideal inerter elements (i.e., improved vibration suppression through increasing inertance without increasing secondary mass leading to lightweight vibration absorbers) is maintained for nonlinear structures and inerter devices. Moreover, a comparison of experimental data with data derived from two different nonlinear parametric numerical models capturing faithfully the HDRBs response, one using a nonlinear mechanical model to represent the inerter device and the other using an ideal linear inerter element instead, demonstrate that displacement, acceleration and base shear response of the SDOF structure is insignificantly influenced by the nonlinear attributes of the inerter device. This outcome paves the way for developing simplified, thus practically meritorious, optimal TMDI tuning approaches adopting the ideal inerter element assumption to model physical inerter devices.

Since the publication of this article [1] we noticed the Greek characters are not properly properly converted due to a conversion error during the production process.

Hepatitis E virus (HEV) is an emerging cause of autochthonous-acute-hepatitis and acute-on-chronic-liver-failure in western countries. Treatment is not routinely used, despite ribavirin has a good antiviral effect. In vitro sofosbuvir inhibits HEV replication, but clinical data are lacking. We report a case of acute-on-chronic-liver-failure due to HEV treated with sofosbuvir and ribavirin. The treatment was capable of rapidly inducing both HCV and HEV viral suppression. In conclusion, although more data are required before firm conclusions could be drawn, the combination of sofosbuvir and ribavirin in not immunosuppressed patients with acute hepatitis E may be able to clear HEV infection.

Summary Inter-story isolation, an effective strategy for mitigating the seismic risk of both new and existing buildings, has gained more and more interest in recent years as alternative to base isolation, whenever the latter results to be impractical, technically difficult or uneconomic. As suggested by the name, the technique consists in inserting flexible isolators at floor levels other than the base along the height of a multi-story building, thus realizing a non-conventional Tuned Mass Damper (TMD). Consistent with this, an optimal design methodology is developed in the present paper with the objective of achieving the global protection of both the structural portions separated by the inter-story isolation system, that is, the lower portion (below the isolation system) and the isolated upper portion (above the isolation system). The optimization procedure is formulated on the basis of an energy performance criterion that consists in maximizing the ratio between the energy dissipated in the isolation system and the input energy globally transferred to the entire structure. Numerical simulations, performed under natural accelerograms with different frequency content and considering increasing isolation levels along the height of a reference frame structure, are used to investigate the seismic performance of the optimized inter-story isolation systems. Copyright © 2015 John Wiley & Sons, Ltd.

Shaking table tests have been carried out to investigate the pounding phenomenon between a mass and two-sided shock absorbers, subject to sinusoidal excitations. In an effort to investigate the effectiveness of such an impact mitigation measure, preliminary tests were carried out: first, the dynamic response was recorded without pounding, and second, the test structure was placed with gap separation and pounding was induced. Absolute acceleration, relative excursion, mean contact force, coefficient of restitution, and dissipated energy were recorded at steady state and the excitation frequency range for pounding occurrences was determined. Numerical predictions were made by using a contact model for the simulation of impacts, able to appropriately describe the behavior of rubber under impact loading. Good agreement between the experimental and the numerical results was achieved.

In the present paper, a linear model for multi-degree-of-freedom systems with rate-independent damping is proposed to the purposes of dynamic response prediction and identification. A viscoelastic model with memory, equivalent to the ideal hysteretic model as for the energy dissipation properties, but causal and physically consistent in both the time and the frequency domain, is developed by adopting the Maxwell–Wiechert kernel function and by requiring the loss modulus to be substantially independent of frequency in a specified range of interest. The finite element model of the equivalent viscoelastic system is constructed and its equations of motion are shown to be uncoupled, in terms of modal coordinates, by the real-valued eigenvectors of the conservative system. An augmented state-space formulation, which encompasses, besides the customary displacements and velocites, a number of internal variables devoted to represent the viscoelastic memory, is then provided for the sake of system identification. Mechanical and modal properties of the equivalent viscoelastic model are finally illustrated by means of numerical examples.

SUMMARY Vibration isolation is well recognized as an effective mitigation strategy for acceleration-sensitive equipment subjected to earthquake. In the present paper, an equipment isolation system with nonlinear hysteretic behaviour is proposed and a methodology for the optimal design is developed. An integrable constitutive model, derived from the mathematical Duhem hysteresis operator, is adopted for the isolation system. The optimization procedure is defined through a dual-criteria approach that involves a transmissibility criterion combined with an energy performance criterion: the former consists in limiting the absolute acceleration of the isolated equipment below an allowable threshold value; the latter, in maximizing the ratio between the energy dissipation due to hysteresis and the input energy to reduce the isolator displacements. The seismic effectiveness of the nonlinear hysteretic isolation system is numerically investigated under natural accelerograms with different frequency content and increasing levels of excitation. Both ground-mounted and floor-mounted equipment items are considered in the analyses; in the second case, the dynamic interaction between the equipment and its supporting structure is taken into account in the design of the isolation system, and its effects on the isolation performance and the structural response are discussed. Comparisons in terms of effectiveness and robustness with a linear isolation system with viscoelastic behaviour are eventually provided. Copyright © 2013 John Wiley & Sons, Ltd.

Platelet activation seems to be implicated in the cardiovascular events occurring in patients with community-acquired pneumonia (CAP) but the underlying mechanism is still unclear. Aim of the study was to assess the mechanism involved in platelet activation in CAP patients.Two-hundred-seventy-eight consecutive patients hospitalized for CAP were recruited and followed-up until discharge. Hospitalized patients matched for sex, age and comorbidities but without acute infectious diseases were used as controls.At hospital admission patients disclosed enhanced plasma levels of sP-selectin, a maker of in-vivo platelet activation, serum sNOX2-dp, a marker of NADPH-oxidase activation, serum Lipopolysaccharide (LPS) and serum zonulin, a marker of gut permeability, compared to controls (p 0.001). Baseline sP-selectin was independently associated to serum LPS, sNOX2-sp and Pneumonia Severity Index score (p 0.001). Plasma sP-selectin, serum sNOX2-dp, LPS and zonulin coincidentally decreased at hospital discharge (p 0.001). An in vitro study showed that LPS, at concentration similar to that found in CAP patients, induced sP-selectin release by agonist-activated platelets, a phenomenon that was counteract by treating cells with gp91ds-tat, a specific inhibitor of NOX2.CAP patients display enhanced platelet activation, which is related to LPS-mediated NOX2 activation. Enhanced gut permeability seems be implicated in enhancing circulating levels of LPS.