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Impact and compression-after-impact (CAI) tests were carried out on [02/ ± 45]s carbon/epoxy samples to characterize the effect of z-pinning on the delamination resistance and damage tolerance properties of the laminate. Unpinned and z-pinned samples were subjected to impacts between 2 and 36 J to produce damage conditions that extend from barely visible impact damage (BVID) to complete penetration. The damage induced by impact and the damage modes leading to ultimate CAI failure were examined by X-radiography and by direct observations of the sample faces during CAI loading. The analyses indicate that the role of z-pins on the impact and CAI response of the laminate is dependent on the size and features of the damage. Z-pins do not modify the structural response to impact of the laminate, but they are effective in reducing the extent of damage for impact energies above a threshold value. Z-pinning is also effective in improving the CAI strength of the laminate for impact energies above this threshold value, even though it degrades the residual compressive strength for lower impact energies. Reductions in impact delamination size of up to 50% and improvements in CAI strength of about 20% were achieved by z-pinning for high-energy impacts. The mechanisms by which the z-pins affect the CAI response of the samples are illustrated and examined in detail for different impact damage severities.

In the past few decades, the need for efficient and reliable Structural Health Monitoring strategies has led to the development of several approaches for damage detection and characterization purposes. Among them, the Nonlinear Vibro-Acoustic Modulation (VAM) exploits the modulation arising from the interaction of two concurrently applied driving waves, namely the probe and the pump excitations, in the presence of nonlinear scatters such as cracks and defects. Therefore, the VAM provides information on the emergence of internal damage by extracting the nonlinear modulated components of the response of a damaged system. Originally proposed for granular media, the method has shown to be effective in detecting the presence of defects also in metals and composite materials. Nonetheless, its efficacy is highly affected by the excitation frequencies, which are usually chosen among the system resonances. The need for a preliminary modal analysis and, at once, the risk of selecting pump-probe frequency combinations with low sensitivity to damage may make the procedure time-consuming and not fully reliable, preventing the VAM technique from being widely accepted as a robust monitoring tool. To overcome these limitations, a broadband excitation may be used. This study assesses the effectiveness of the VAM technique when a combination of a frequency-swept pump excitation and a mono-harmonic probe wave is applied to drive the sample. Experimental tests were conducted on a composite laminated beam mounted on an electrodynamic shaker and tested in both pristine and damaged conditions. Low-profile surface-bonded piezoceramic transducers were used for both probe excitation and sensing. Barely visible impact damage (BVID) was introduced in the composite beam to examine the potential of the approach for the detection of very small, localized damage. The results show that the use of VAM with a broadband low-frequency excitation may be an effective option for identifying nonlinearities associated with typical damage occurring in composite structures.

Composite materials provide many advantages over more conventional materials. However, their susceptibility to impact damage can question their use in critical load-bearing structures, and efficient methods are needed for early damage detection. To this purpose, the nonlinear vibro-acoustic modulation (VAM) technique applies a low-frequency pump excitation and a high-frequency probe excitation to exploit the onset of harmonic components around the probe frequency of the damaged structural response. The VAM technique has been widely studied on structures instrumented with piezoceramic transducers used for both actuation and sensing, but few attempts have been made to use equipment typical of modal testing, such as shakers and accelerometers. In this study, the VAM technique is applied to a composite laminate beam by employing an electro-dynamic shaker to generate low-frequency flexural excitation, a low-profile piezoceramic transducer to introduce the probe wave, and a micro-accelerometer to sense the structural response. Three resonance low frequencies and two acoustic frequencies are considered in different testing scenarios, at increasing levels of excitation amplitude. The results show a general good performance of the technique with the adopted experimental setup, the choice of the probe frequency and the higher level of the pump excitation having a significant impact on its sensitivity.

Migration of natural reservoir fines mobilised by water production may cause significant well productivity decline. The aim of this work is long-term productivity forecast from the production history under fines migration. We derive an exact solution of the radial inflow problem for suspension with size-distributed particles. The exact solution allows for detailed analysis of the structure of the flow domain and for an implicit formulae for well impedance. Six model coefficients are determined from the history of well production and fines concentration in the produced fluid. 23 field cases have been matched by the analytical model. Close agreement between the field and modelling data and common variation intervals for the tuned model parameters validate the model proposed. The analytical model allows determining the size of the damaged zone during water production under fines migration, which is important for well stimulation planning and design.

In this study, the structural and fracture behavior of cementitious composite beams subjected to flexural loads is experimentally and numerically investigated. Six series of mortar specimens reinforced with steel mesh layer ware cast and tested in 4–point bending. Configurations with 2, 4 or 6 mesh layers were examined to characterize the flexural response of materials. A 3D FE model was developed in ABAQUS to predict the nonlinear behavior of the beams and to simulate the evolution of fracture patterns under an increasing load. The nonlinear cracking and crushing response of the mortar was implemented by using the Concrete Damage Plasticity model. For the steel reinforcement, an elasto-plastic model with isotropic hardening was adopted. The results of the numerical analysis are discussed. Comparisons between numerical and experimental results highlight a reasonably good agreement both in term of structural response and of damage growth.

Pseudoangiomatous stromal hyperplasia (PASH) is an uncommon benign mesenchymal breast lesion. There are extremely rare reports of PASH arising in accessory breast tissue. To date, in literature, fewer than 10 cases of PASH occurring in axillary region have been described. We report a case presenting as axillary lump in a young woman. A 20-year-old female presented to our surgical unit for a progressively growing and painful palpable mass of the right axilla for about a year. Before surgery an ultrasound was performed. The patient underwent local excision of the lesion under local anaesthesia. Through histological and immunohistochemical examination a pseudoangiomatous stromal hyperplasia (PASH) was diagnosed. At 6 months of followup the patient is free of disease. It is important to include PASH also in the differential diagnosis of axillary lumps. Histological examination of the surgical specimen and surgery represent, respectively, the mainstay for diagnosis and therapy.

The Investigations of this article focus on the response of an Al2O3:C radioluminescence (RL) prototype for medical dosimetry in a 6 MV photon beam. The prototype can be configured using two types of detectors coupled to fiber-optic cables - single crystal (1 x 1 x 2 mm(3)) and droplets (in two grain sizes, 38 and 4 mu m, molded in r =0.5 mm,1= 200 mu m). By using the appropriate filters in addition to time gating it is possible to remove disturbance present during irradiation: the stem effect. Pre -irradiation of the dosimeters to a dose of 300 Gy made the memory effects in Al2O3:C negligible, so as to not impair the dosimetric properties of the system. The key findings are that the system is suitable for small field beam dosimetry, while giving overall good dose response in other features (i.e., beam profile, dose rate - FF and FFF modes). The results show that our prototype can be used for real time dose rate assessment in medical photon dosimetry without many correction factors. The 41 mu m RL measurement results are in excellent agreement (i.e. below 1%) with the dose delivered according to standard beam data. (C) 2018 Elsevier B.V. All rights reserved.

The spread of infections from multi-resistant bacteria in hospitals around the world is raising at an alarming rate. With the increasing capacity of bacteria to develop resistance to traditional antibiotics that target a particular metabolic pathway inside the cell, the use of nanoparticles as therapeutic agents is gaining importance because of their ability to attack bacterial membranes without evoking resistance. We have synthesized the catanionic surfactants Coum12–Coum18, based on fluorescent lactose-derivative organic salts using low-cost starting materials. In water, they self-assemble spontaneously to form stable aggregates at a physiological pH. The antibacterial properties of Coum12–Coum18 were investigated towards multi-drug-resistant Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Compound Coum18 was found to have both a bacteriostatic and a bactericidal activity towards Gram-positive bacteria, although the values of both the MIC and MBC (32 μg mL−1) suggest only a topical use of the molecule. The valuable results that were found provide a challenging task for further investigation aimed at the development of this class of antibacterial drugs. In vitro fluorescence microscopy gave insight into the interaction between the aggregates and the cellular membranes on HeLa and CHO cells.

Differenti studi hanno riscontrato nei pazienti con diagnosi di disturbo psicotico una diffusa compromissione delle funzioni esecutive, in particolare della Working Memory, e una tendenza a prendere decisioni rapidamente dovuta ad errori nel processamento di raccolta delle informazioni presenti nel contesto (Jumping To Conclusion, JTC). Obiettivo del presente studio é quello indagare la presenza di una possibile correlazione tra Working Memory e Jumping To Conclusions in un campione di pazienti al primo episodio psicotico. Per il presente studio sono stati valutati 41 pazienti all’esordio psicotico (58,5% M), di età media 29,63 (DS=10,285) e 89 controlli sani (47,2% M), di età media 33,31 (DS=12,817). I dati hanno mostrato che il Jumping To Conclusions è presente in 45 degli 89 soggetti del gruppo di controllo (51,1%) e in 31 dei 38 individui del gruppo dei casi (81,6%). Dalle percentuali ricavate, si nota come il gruppo dei casi fosse più propenso a “saltare alle conclusioni” rispetto ai controlli (χ2=10,28; p=0,001). Per quanto riguarda i compiti di Working Memory, i pazienti psicotici hanno ottenuto punteggi peggiori rispetto ai controlli. Infine, le analisi di correlazione svolte all’interno del gruppo dei casi rilevano la presenza di una correlazione significativamente positiva tra il punteggio ottenuto al Beads Task e tutti i compiti di Working Memory: Digit Span (rho=0,28; p=0,003), Digit Symbol (rho=0,27; p=0,002), Arithmetic (rho=0,26; p=0,003) e Block Design (rho=0,29; p=0,001). I risultati esposti sembrano inoltre supportare, in accordo con la letteratura, l’ipotesi di una possibile correlazione tra alterazioni a carico della Working Memory e deficit di raccolta dati Jumping To Conclusions.