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Non-intrusive methods have been used since two decades to derive reduced-order models for geometrically nonlinear structures, with a particular emphasis on the so-called STiffness Evaluation Procedure (STEP), relying on the static application of prescribed displacements in a finite-element context. We show that a particularly slow convergence of the modal expansion is observed when applying the method with 3D elements, because of nonlinear couplings occurring with very high frequency modes involving 3D thickness deformations. Focusing on the case of flat structures, we first show by computing all the modes of the structure that a converged solution can be exhibited by using either static condensation or normal form theory. We then show that static modal derivatives provide the same solution with fewer calculations. Finally, we propose a modified STEP, where the prescribed displacements are imposed solely on specific degrees of freedom of the structure, and show that this adjustment also provides efficiently a converged solution., Comment: 6 tables, 14 figures, 27 pages

The direct computation of the third-order normal form for a geometrically nonlinear structure discretised with the finite element (FE) method, is detailed. The procedure allows to define a nonlinear mapping in order to derive accurate reduced-order models (ROM) relying on invariant manifold theory. The proposed reduction strategy is direct and simulation free, in the sense that it allows to pass from physical coordinates (FE nodes) to normal coordinates, describing the dynamics in an invariant-based span of the phase space. The number of master modes for the ROM is not a priori limited since a complete change of coordinate is proposed. The underlying theory ensures the quality of the predictions thanks to the invariance property of the reduced subspace, together with their curvatures in phase space that accounts for the nonresonant nonlinear couplings. The method is applied to a beam discretised with 3D elements and shows its ability in recovering internal resonance at high energy. Then a fan blade model is investigated and the correct prediction given by the ROMs are assessed and discussed. A method is proposed to approximate an aggregate value for the damping, that takes into account the damping coefficients of all the slave modes, and also using the Rayleigh damping model as input. Frequency-response curves for the beam and the blades are then exhibited, showing the accuracy of the proposed method., 34 pages, 10 figures, 2 tables, submitted to CMAME

The dynamic analysis of systems with nonlinearities has become an important topic in many engineering fields. Apart from the forced response analyses, nonlinear modal analysis has been successfully extended to such non-conservative systems thanks to the definition of damped nonlinear normal modes. The energy balance method is a tool that permits to directly predict resonances for a conservative system with nonlinearities from its nonlinear modes. In this work, the energy balance method is extended to systems with non-conservative nonlinearities using the concept of the damped nonlinear normal mode and its application in a full-scale engineering structure. This extended method consists of a balance between the energy loss from the internal damping, the energy transferred from the external excitation and the energy exchanged with the non-conservative nonlinear force. The method assumes that the solution of the forced response at resonance bears resemblance to that of the damped nonlinear normal mode. A simplistic model and full-scale structure with dissipative nonlinearities and a simplistic model showing self-excited vibration are tested using the method. In each test case, resonances are predicted efficiently and the computed force–amplitude curves show a great agreement with the forced responses. In addition, the self-excited solutions and isolas in forced responses can be effectively detected and identified. The accuracy and limitations of the method have been critically discussed in this work.

We report nonlinear vibration localisation in a system of two symmetric weakly coupled nonlinear oscillators. A two degree-of-freedom model with piecewise linear stiffness shows bifurcations to localised solutions. An experimental investigation employing two weakly coupled beams touching against stoppers for large vibration amplitudes confirms the nonlinear localisation., Comment: 14 pages, 11 figures

The objective of this contribution is to compare two methods proposed recently in order to build efficient reduced-order models for geometrically nonlinear structures. The first method relies on the normal form theory that allows one to obtain a nonlinear change of coordinates for expressing the reduced-order dynamics in an invariant-based span of the phase space. The second method is the modal derivative (MD) approach, and more specifically the quadratic manifold defined in order to derive a second-order nonlinear change of coordinates. Both methods share a common point of view, willing to introduce a nonlinear mapping to better define a reduced order model that could take more properly into account the nonlinear restoring forces. However the calculation methods are different and the quadratic manifold approach has not the invariance property embedded in its definition. Modal derivatives and static modal derivatives are investigated, and their distinctive features in the treatment of the quadratic nonlinearity is underlined. Assuming a slow/fast decomposition allows understanding how the three methods tend to share equivalent properties. While they give proper estimations for flat symmetric structures having a specific shape of nonlinearities and a clear slow/fast decomposition between flexural and in-plane modes, the treatment of the quadratic nonlinearity makes the predictions different in the case of curved structures such as arches and shells. In the more general case, normal form approach appears preferable since it allows correct predictions of a number of important nonlinear features, including for example the hardening/softening behaviour, whatever the relationships between slave and master coordinates are., 43 pages, 12 figures, published in Nonlinear Dynamics

Myastenia-Inflammatory Myopathy (MG-IM) association has been described in less than 50 cases, as isolated reports or in few case series. In most cases, MG and IM onset occur simultaneously even if the overlapping clinical manifestations could lead to delay the diagnosis in the early stage of disease. In these cases, thymic pathology is present in more than 50% of cases. Pathological findings can be consistent of polymyositis (63%), dermatomyositis (25%) or granulomatosis (12%). Accurate clinical manifestations and severity of IM in MG, including muscle specific antibodies (MSA) and muscle MRI, have not been systematically investigated and focal or mild subclinical myositis have not been reported. We observed that focal myositis or asymptomatic CK elevation can also occur in MG. In this review we have also retrospectively re-analyzed the clinical, serological, pathological and muscle imaging data from 13 patients with MG- IM from our cohort of 441 MG patients (2,9%). Clinical onset occurred simultaneously in 10/13 patients, whereas in 2 patients the IM appeared later in MG disease course (range 10–14 years) and conversely in 1 patient MG symptoms occurred later in IM disease course (4 years). Median age at disease onset was 51 year (range 24–73 years) regardless of clinical onset (MG or IM). Median clinical follow-up was 88 months (range 31–237 months). IM was suspected by CK elevation in all patients (ranging 800–3000 UI/L at first detection) and non-fatigable muscle weakness unresponsive to acetylcholinesterase inhibitors. All the patients presented mild to moderate MG symptoms. Three main categories of muscle involvement, sometimes overlapping, were recognizable: distal, proximal and subclinical myositits, leading to three main clinical groups (A,B,C) and two overlapping subgroups (A/B and B/C). Thymus pathology was present in 10/13 patients. Anti-AChR was detected in al all patients associated with anti-Titin and -RyR1 in those patients with thymoma. No MSA, nor MAA antibodies were detected. Muscle biopsy confirmed IM in all patients. In conclusion we redefined the clinical spectrum of muscle involvement in MG-IM association, which represent a continuum among 3 main clinical groups: distal, proximal and subclinical muscle involvement. Minimal muscle involvement and focal myositis could be underestimated among myasthenic patients and early aggressive immunotherapy could be required in focal group.

Introduction Aquaporins (AQPs) are a family of transmembrane proteins involved in the maintenance of osmotic gradients. AQP4 is abundant in skeletal muscle, where it seems to be associated with glycolytic metabolism. We investigated the pattern of expression of AQP4 in normal human myofibers relative to the main forms of myosin heavy chain (MHC). Methods Six normal human muscle biopsies were analyzed by double immunofluorescence for co-expression of AQP4 and slow or fast MHC. Results A high percentage (64-99%) of MHC-fast positive fibers showed immunoreaction for AQP4. Immunoreactivity for AQP4 was also present in MHC-slow positive fibers, but with a higher variability (5-72%) among biopsies. Discussion The expression pattern of AQP4 in human myofibers is highly variable among different patients and cannot be predicted for single fibers depending on MHC type expression. Other factors, possibly related to muscle activity, may modulate AQP4 expression. Muscle Nerve 57: 856-859, 2018.

La validazione dei protocolli di diagnosi secondo standard europei (ISO/IEC standard 16140:2003 e 17025:2005; EPPO standard PM7/76-4 e PM7/98-2), rappresenta un aspetto di fondamentale importanza nell’ambito della diagnosi fitopatologica. L’uso di protocolli validati è, infatti, alla base di un’efficiente applicazione delle misure fitosanitarie, garantendo una maggiore affidabilità dei risultati diagnostici ottenuti e la loro confrontabilità, quando prodotti in laboratori diversi ed in diverse condizioni operative. Negli ultimi anni, diversi progetti a livello europeo (Euphresco-FRUITPHYTOINTERLAB, -GRAFDEPI, -GRAFDEPI2) e nazionale (ARON-ARNADIA) hanno riguardato la validazione di protocolli per la diagnosi di patogeni vegetali. Il Progetto Finalizzato ASPROPI, recentemente finanziato dal MiPAAF, ha costituito la naturale prosecuzione dell’attività già svolta nell’ambito del progetto ARON-ARNADIA, avente come obiettivo quello di fornire linee guida per il rilevamento e l’identificazione di patogeni delle piante (funghi, batteri, fitoplasmi, virus e viroidi) ai laboratori preposti alla diagnosi degli organismi di qualità e/o quarantena, presenti sul territorio italiano. Con riferimento ai fitoplasmi, il progetto ha riguardato la validazione di protocolli per la diagnosi dei fitoplasmi agenti della flavescenza dorata (FD) della vite. La scelta delle metodologie diagnostiche da validare e la definizione dei parametri di validazione è scaturita dal lavoro congiunto di un Gruppo di lavoro di esperti costituito da varie istituzioni scientifiche di comprovata esperienza nello studio di tale patogeno. Complessivamente sono stati validati 3 protocolli molecolari, includenti: i) due protocolli TaqMan® real time PCR (qPCR) per la diagnosi multipla di FD, legno nero (LN) ed un controllo endogeno di cui, uno con kit commerciale sviluppato da IPADLAB (metodo 1) ed uno secondo la procedura descritta in Angelini et al. (2007) (metodo 2) e ii) un protocollo basato su tecnica LAMP con kit commerciale sviluppato da IPADLAB (metodo 3). Per ciascun protocollo, la validazione è stata effettuata attraverso la definizione dei seguenti parametri: sensibilità analitica (limite di rilevabilità), specificità analitica, sensibilità e specificità diagnostica, accuratezza, ripetibilità e riproducibilità. Per l’ottenimento del valore della riproducibilità, ogni protocollo è stato sottoposto ad un ring test a cui hanno preso parte 15 laboratori afferenti ai servizi fitosanitari regionali (11) e ad Enti/Istituzioni di ricerca (4). Le prove effettuate con campioni di riferimento target e non-target hanno evidenziato una maggiore sensibilità analitica dei due metodi qPCR rispetto al metodo LAMP. La valutazione della specificità analitica ha evidenziato per tutti i protocolli una reazione generica nei confronti di fitoplasmi del gruppo 16SrV ed in nessun caso specifica verso i soli fitoplasmi agenti di FD. Complessivamente, i parametri di performance del metodo 1 sono risultati superiori rispetto agli altri metodi valutati, con valori di sensibilità e specificità diagnostica, accuratezza, ripetibilità e riproducibilità sempre superiori al 90%. I metodi 2 e 3, invece, hanno evidenziato, rispettivamente, bassi valori di specificità diagnostica (73,3%) e sensibilità diagnostica (75%).

We present three members of an Italian family affected by tubular aggregate myopathy (TAM) and congenital miosis harboring a novel missense mutation in ORAI1. All patients had a mild, late onset TAM revealed by asymptomatic creatine kinase (CK) elevation and congenital miosis consistent with a Stormorken-like Syndrome, in the absence of thrombocytopathy. Muscle biopsies showed classical histological findings but ultrastructural analysis revealed atypical tubular aggregates (TAs). The whole body muscle magnetic resonance imaging (MRI) showed a similar pattern of muscle involvement that correlated with clinical severity. The lower limbs were more severely affected than the scapular girdle, and thighs were more affected than legs. Molecular analysis revealed a novel c.290C>G (p.S97C) mutation in ORAI1 in all affected patients. Functional assays in both human embryonic kidney (HEK) cells and myotubes showed an increased rate of Ca2+ entry due to a constitutive activation of the CRAC channel, consistent with a 'gain-of-function' mutation. In conclusion, we describe an Italian family harboring a novel heterozygous c.290C>G (p.S97C) mutation in ORAI1 causing a mild- and late-onset TAM and congenital miosis via constitutive activation of the CRAC channel. Our findings extend the clinical and genetic spectrum of the ORAI1-related TAM.

The ubiquitous diffusion of Power Electronic Converters (PECs) in many fields of application including traction and energy conversion is suggesting the possibility of new and better integration of advanced power conversion and ICT services. This work investigates the possible advancements in the use of optical fibers for control of PECs, using Plastic Optical Fiber. The optical communication link connects the switching control to the converter control, following the line of separation between the expertises of the power electronic engineer and the control engineer. Control wise, the PEC becomes a black box compatible with any off-board controller, now immune from the Electromagnetic Interference (EMI) produced by the power switches. The redundant optical link is ready for the high switching (and sampling) frequencies possible with the use of SiC power semiconductor devices (100 kHz+). Distributed control of multiple PEC units and advanced telemetry for diagnostics and prognostics are targeted. A proof-of-concept demonstrator is presented and tested. Moreover, the possible evolution towards a power electronic cloud with remote management and orchestration is described.

The Internet of Things paradigm and the ubiquitous diffusion of Power Electronic Converters in many fields of application are suggesting the possibility of new ICT services associated to advanced power conversion. This work investigates the feasibility of shared centralized control and communications units able to control and synchronize different power converters, enabling real-time control and telemetry with a cloud approach on the Internet. Our research is focused on defining a proper communication bus making communications between devices and their remote control and telemetry possible in such a challenging environment.

The ubiquitous diffusion of Power Electronic Converters (PECs) in many fields of application including traction and energy conversion suggests the possibility of new and better integration of advanced power conversion and Information and Communication Technology (ICT) services. This work investigates the possible advancements in the use of optical communication links made of plastic optical fibers for control of PECs. The optical communication link connects the switching control to the converter control, following the line of separation between the expertise of power electronic and control engineers. Control wise, a PEC is a black box compatible with any off-board controller, now immune from the Electromagnetic Interference (EMI) produced by the power switches. The redundant optical link is ready for the high switching and sampling frequencies, made possible by relying on SiC power semiconductor devices (100+ kHz). Distributed control of multiple PEC units and advanced telemetry for diagnostics and prognostics are targeted. A proof-of-concept demonstrator is presented and tested. Moreover, the possible evolution towards a power electronic cloud with remote management and orchestration is described.