Damage initialization techniques for non-sequential FE propagation analysis of delaminations in composite aerospace structures

The experimental effort required to develop, damage tolerant, aerospace composite structures could be significantly reduced if reliable numerical simulations were used to perform engineering studies of complex damaged structures. Finite element (FE) simulations of impact damaged structures typically follow a sequential approach that require large computational resources to reproduce complex damage scenarios. A numerical tool capable to reconstruct such scenarios using data from previous impact simulations or NDI could noticeably improve the simulation workflow for damaged composite structures. The paper proposes a method to inizialize the damage variables in numerical analyses aimed at assessing damage propagation, and that are potentially able to evaluate the residual strength of damaged structures. The approach is developed within FE software ABAQUS, and uses SDVINI subroutine to initialize damage variables defined by a user-material-subroutine (UMAT), that provides the constitutive models of the lamina and of the interlaminar layers. Albeit the proposed technique might deal with both inter-laminar and intra-laminar damage, the paper is focused on delaminations. A user defined traction-separation law is coded in an UMAT that endows ABAQUS cohesive elements with damage initialization capabilities. Then, results of test cases, of increasing complexity, are presented in order to assess the damage initialization procedure and verify the performances of its different operating modes. Two test-cases are based on plate-like specimens for which literature data exist: the first is relevant to a circular artificial delamination while the second presents multiple delaminations caused by an impact and measured via NDI techniques. The last test-case is a stiffened panel which incorporates the typical complexities of aerospace structures, but is still tractable with the sequential simulation approach whose results are used as a term of comparison

Insight into phenotypic and genotypic differences between vaginal lactobacillus crispatus bc5 and lactobacillus gasseri bc12 to unravel nutritional and stress factors influencing their metabolic activity

The vaginal microbiota, normally characterized by lactobacilli presence, is crucial for vaginal health. Members belonging to L. crispatus and L. gasseri species exert crucial protective functions against pathogens, although a total comprehension of factors that influence their dominance in healthy women is still lacking. Here we investigated the complete genome sequence and comprehensive phenotypic profile of L. crispatus strain BC5 and L. gasseri strain BC12, two vaginal strains featured by anti-bacterial and anti-viral activities. Phenotype microarray (PM) results revealed an improved capacity of BC5 to utilize different carbon sources as compared to BC12, although some specific carbon sources that can be associated to the human diet were only metabolized by BC12, i.e. uridine, amygdalin, tagatose. Additionally, the two strains were mostly distinct in the capacity to utilize the nitrogen sources under analysis. On the other hand, BC12 showed tolerance/resistance towards twice the number of stressors (i.e. antibiotics, toxic metals etc.) with respect to BC5. The divergent phenotypes observed in PM were supported by the identification in either BC5 or BC12 of specific genetic determinants that were found to be part of the core genome of each species. The PM results in combination with comparative genome data provide insights into the possible environmental factors and genetic traits supporting the predominance of either L. crispatus BC5 or L. gasseri BC12 in the vaginal niche, giving also indications for metabolic predictions at the species level

Geomicrobiology of a seawater-influenced active sulfuric acid cave.

Fetida Cave is an active sulfuric acid cave influenced by seawater, showing abundant microbial communities that organize themselves under three main different morphologies: water filaments, vermiculations and moonmilk deposits. These biofilms/deposits have different cave distribution, pH, macro- and microelement and mineralogical composition, carbon and nitrogen content. In particular, water filaments and vermiculations had circumneutral and slightly acidic pH, respectively, both had abundant organic carbon and high microbial diversity. They were rich in macro- and microelements, deriving from mineral dissolution, and, in the case of water filaments, from seawater composition. Vermiculations had different color, partly associated with their mineralogy, and unusual minerals probably due to trapping capacities. Moonmilk was composed of gypsum, poor in organic matter, had an extremely low pH (0\u20131) and low microbial diversity. Based on 16S rRNA gene analysis, the microbial composition of the biofilms/deposits included autotrophic taxa associated with sulfur and nitrogen cycles and biomineralization processes. In particular, water filaments communities were characterized by bacterial taxa involved in sulfur oxidation and reduction in aquatic, aphotic, microaerophilic/anoxic environments (Campylobacterales, Thiotrichales, Arenicellales, Desulfobacterales, Desulforomonadales) and in chemolithotrophy in marine habitats (Oceanospirillales, Chromatiales). Their biodiversity was linked to the morphology of the water filaments and their collection site. Microbial communities within vermiculations were partly related to their color and showed high abundance of unclassified Betaproteobacteria and sulfur-oxidizing Hydrogenophilales (including Sulfuriferula), and Acidiferrobacterales (including Sulfurifustis), sulfur-reducing Desulfurellales, and ammonia-oxidizing Planctomycetes and Nitrospirae. The microbial community associated with gypsum moonmilk showed the strong dominance (>60%) of the archaeal genus Thermoplasma and lower abundance of chemolithotrophic Acidithiobacillus, metal-oxidizing Metallibacterium, Sulfobacillus, and Acidibacillus. This study describes the geomicrobiology of water filaments, vermiculations and gypsum moonmilk from Fetida Cave, providing insights into the microbial taxa that characterize each morphology and contribute to biogeochemical cycles and speleogenesis of this peculiar seawater-influenced sulfuric acid cave

Corrigendum: An In vitro Study of Bio-Control and Plant Growth Promotion Potential of Salicaceae Endophytes

[This corrects the article DOI: 10.3389/fmicb.2017.00386.]

The Complete Genome Sequence and Structure of the Oleaginous Rhodococcus opacus Strain PD630 Through Nanopore Technology

Rhodococcus opacus PD630 is a model bacterial strain for the production of neutral lipids (mostly triacylglycerols,TAGs) from low-cost substrates and lignin biomass feedstocks. Presently, only a contig-level assembly of PD630 genome is available, after the exclusion from NCBI RefSeq of a ’complete’ version that was marked as ’anomalous assembly’. In this work, we achieved the R. opacus PD630 high-quality genome assembly by combining Oxford Nanopore sequencing with Illumina accurate short reads. Our work demonstrates that R. opacus PD630 has a 9.17 Mbp-long genome composed by one chromosome of 8.4 Mbp and three plasmids, i.e. one linear plasmid of 538 Kbp (pRoPD630 1) and two circular plasmids of 167.9 and 85 Kbp (pRoPD630 2 and pRoPD630 3). The comparison between this genome and the previous ”complete” version was performed to identify genetic and structural differences and to detect syntenic regions. The functional analysis of several R. opacus species plasmids showed that genes involved in lipid metabolism and xenobiotics’ degradation are generally clustered within specific plasmids. In the case of PD630, these genes are carried by the linear plasmid pRoPD630 1 whose structure has been assessed in this study. Our work defines the whole genome architecture and sequence of PD630, providing the groundwork to correctly interpret ’omics’ data and to design genetic engineering approaches for this model strain

On the Application of MPE-FEC to Mobile DVB-S2: Performance Evaluation in Deep Fading Conditions

Digital Video Broadcasting through Satellite transmission will provide new services to aeronautical, railway and maritime mobile terminals. However, mobile channel impairments request effective countermeasures to improve the C/N performance and counteract Doppler spread. The paper investigates the application of MPE-FEC (Multi Protocol Encapsulation - Forward Error Correction) to DVB-S2 standard chain for railway applications. In this scenario, trellis power arches may introduce deep fading events which cause bursts of data losses. An analytical model describing MPE-FEC decoder performance has been derived and validated through numerical simulation considering different train speed values, MOD-COD (modulation order and physical layer coding rate) configurations and number of rows in the MPE-FEC frame. Results show that, depending on the train speed, enlarging the number of rows or adopting a sliding encoding mechanism are effective in counteracting power arches impairments

Physiology and genetics of Rhodococcus aetherivorans BCP1 response to Arsenic

Arsenic ranks among the priority metals that are of public health significance. In the environment, the metalloid arsenic mainly exists under two forms: the arsenite [As(III)] and arsenate [As(V)]; the former being more toxic due to its high mobility and stability. Bacteria have developed multiple strategies for arsenic detoxification. Rhodococcus aetherivorans BCP1 is able to cometabolize chlorinated compounds, mineralize a wide range of hydrocarbons1, resist different stress conditions2 and convert tellurite and selenite into less toxic forms3, making this strain an ideal candidate for microbial biotechnology applications. In this study, we assessed the ability of BCP1 to tolerate high concentrations of As(V) during its growth under aerobic conditions. Furthermore, different aspects regarding the arsenic homeostasis and the response of BCP1 to As(V) were investigated: (i) the different capability to convert As(V) into As(III) depending on the initial concentration of arsenate; (ii) the arsenic biosorption; (iii) the effect of arsenic on polyphosphate granule formation and (iv) the genetic/genomic aspects involved in arsenic detoxification. Finally, the detection of electrondense nanoparticles after the incubation with As(V) suggested the ability of BCP1 strain to generate As-based nanostructures