Microcracking in piezoelectric materials by the Boundary Element Method

A 3D boundary element model for piezoelectric polycrystalline micro-cracking is discussed in this contribution. The model is based on the boundary integral representation of the electro-mechanical behavior of individual grains and on the use of a generalized cohesive formulation for inter-granular micro-cracking. The boundary integral formulation allows to address the electro-mechanical boundary value problem in terms of generalized grain boundary and inter-granular displacements and tractions only, which implies the natural inclusion of the cohesive laws in the formulation, the simplification of the analysis pre-processing stage, and the reduction of the number of degrees of freedom of the overall analysis with respect to other popular numerical methods

Antibiotic susceptibility of bacterial isolates from probiotic products available in Italy

Objective: An emerging issue of probiotic products is the antibiotic resistance of the strains used. The aim of this study was to determine the susceptibility of the isolates of 10 probiotic products available in Italy. Materials and methods: The susceptibility of 15 strains of Lactobacillus spp., 5 Streptococcus salivarius ssp. thermophilus, 1 Enterococcus faecium and 8 Bifidobacterium spp. to several groups of antibacterial agents was determined by E-test using MRS agar for Lactobacillus spp. and E. faecium and MH agar+5% sheep blood for S. thermophilus, with different conditions of incubation. For Lactobacillus, S. thermophilus and E. faecium the MICs obtained by E-test were compared to the MICs by broth microdilution test obtained following CLSI M45-A (2006) and CLSI M100-S17 (2007) guidelines. Results: The broth microdilution test resulted in MICs identical to those obtained with the E-test or in MICs with differences of 1 or 2 log dilution steps. All the strains of Lactobacillus were susceptible to ampicillin. Species-dependent antibiotic susceptibility was detected for cephalosporins; gentamicin and ciprofloxacin had variable activity. Intrinsic resistance to vancomycin was confirmed for L. paracasei, L. salivarius and L. plantarum. Atypical resistance to erythromycin was detected in one strain of L. salivarius. The strains of Bifidobacterium were susceptible to ampicillin, cefotaxime and erythromycin. The strains of E. faecium were susceptible to the tested antibiotics; the strain of S. thermophilus was resistant only to ciprofloxacin. The observed resistance in the strains used in the Italian probiotic products tested seemed to be intrinsic except for erythromycin in one L. salivarius strain.Key words: antibiotic susceptibility, probiotic, lactic acid bacteria, bifidobacteri

A Preliminary Evaluation of Morphing Horizontal Tail Design for UAVs

Morphing structures are a relatively new aircraft technology currently being investigated for a variety of applications, from civil to military. Despite the lack of literature maturity and its complexity, morphing wings offer significant aerodynamic benefits over a wide range of flight conditions, enabling reduced aircraft fuel consumption and airframe noise, longer range and higher efficiency. The aim of this study is to investigate the impact of morphing horizontal tail design on aircraft performance and flight mechanics. This study is conducted on a 1:5 scale model of a Preceptor N-3 Pup at its trim condition, of which the longitudinal dynamics is implemented in MATLAB. Starting from the original horizontal tail airfoil NACA 0012 with the elevator deflected at the trim value, this is modified by using X-Foil tool to obtain a smooth morphing airfoil trailing edge shape with the same CLα. By comparing both configurations and their influence on the whole aircraft, the resulting improvements are evaluated in terms of stability of the short-period mode, reduction of parasitic drag coefficient CD0, and increased endurance at various altitude

On modelling damage in composite laminates using the Ritz method and continuum damage mechanics

In this work, a Ritz formulation for the analysis of damage initiation and evolution in composite plates under progressive loading is presented. The proposed model assumes a first order shear deformation theory and considers geometric non-linearities through the von Karman assumptions. The damage is modelled through Continuum Damage Mechanics. A set of results is presented to show the potential of the method and highlight some issues to be addressed by suitable developments of the method

Size and asymmetry of the reaction entrance channel: influence on the probability of neck production

The results of experiments performed to investigate the Ni+Al, Ni+Ni, Ni+Ag reactions at 30 MeV/nucleon are presented. From the study of dissipative midperipheral collisions, it has been possible to detect events in which Intermediate Mass Fragments (IMF) production takes place. The decay of a quasi-projectile has been identified; its excitation energy leads to a multifragmentation totally described in terms of a statistical disassembly of a thermalized system (T$\simeq$4 MeV, E$^*\simeq$4 MeV/nucleon). Moreover, for the systems Ni+Ni, Ni+Ag, in the same nuclear reaction, a source with velocity intermediate between that of the quasi-projectile and that of the quasi-target, emitting IMF, is observed. The fragments produced by this source are more neutron rich than the average matter of the overall system, and have a charge distribution different, with respect to those statistically emitted from the quasi-projectile. The above features can be considered as a signature of the dynamical origin of the midvelocity emission. The results of this analysis show that IMF can be produced via different mechanisms simultaneously present within the same collision. Moreover, once fixed the characteristics of the quasi-projectile in the three considered reactions (in size, excitation energy and temperature), one observes that the probability of a partner IMF production via dynamical mechanism has a threshold (not present in the Ni+Al case) and increases with the size of the target nucleus.Comment: 16 pages, 7 figures, accepted for publication on Nuclear Physics

Correction: Ocean acidification at a coastal CO2 vent induces expression of stress-related transcripts and transposable elements in the sea anemone Anemonia viridis.

[This corrects the article DOI: 10.1371/journal.pone.0210358.]