Development of a wireless structural health monitoring system for aerospace application

Structural health monitoring has a number of benefits to the aircraft industry, including improvements to safety, reduction in maintenance costs and potential weight savings. One reason why the aircraft industry is reluctant to apply such systems is the additional weight and integration issues caused by wiring them into the structures. The solution to this is the application of wireless technology, unfortunately this has its own problems and restrictions primarily due to the lack of available power, which would need to be sourced through energy harvesting. One structural health monitoring technique which has been investigated for aircraft use is Acoustic Emission, which enables the detection and localisation of damage within a structure. A major problem with the application of this technology using a wireless system is that adequate time synchronisation of each node would require significantly more power than is available through energy harvesting methods. This work presents the development of a technique to locate damage in complex aircraft structures, which was previously only applicable within simple plates. This method is used to successfully locate damage within fatigue testing on an aircraft wing panel. Furthermore, it can be applied within a wireless system without the need for highly accurate time synchronisation. The work includes the development of a prototype wireless system which applies a simplified version of the developed localisation technique. This hardware is tested on a range of composite and metal structures, including two aircraft wings. The accuracy of the results and the low power requirements of the system support further development in order to apply the system to an aircraft structure

Aerospace Requirements

This chapter covers the overview of requirements arising in the aerospace industry for operating a structural health monitoring (SHM) system. The requirements are based on existing standards and guidelines and include both requirements on the physical components of the system (such as sensors, data acquisition systems and connectors) and their functional requirements (such as reliability, confidence measure and probability of detection). Emphasis has been given to on-board and ground-based components because they have different functionality requirements. An important factor in the reliability of the system is the effect of the environment and operational loads on the reliability of the diagnosis and, consequently, prognosis. The recommended guidelines for testing the reliability of the system under varying operational conditions are presented. This chapter is then finalized by reporting on methodologies for optimal sensor number and placement, based on different sensor technologies and different optimization algorithms

Whole genome sequencing of experimental hybrids supports meiosis-like sexual recombination in Leishmania

Hybrid genotypes have been repeatedly described among natural isolates of Leishmania, and the recovery of experimental hybrids from sand flies co-infected with different strains or species of Leishmania has formally demonstrated that members of the genus possess the machinery for genetic exchange. As neither gamete stages nor cell fusion events have been directly observed during parasite development in the vector, we have relied on a classical genetic analysis to determine if Leishmania has a true sexual cycle. Here, we used whole genome sequencing to follow the chromosomal inheritance patterns of experimental hybrids generated within and between different strains of L. major and L. infantum. We also generated and sequenced the first experimental hybrids in L. tropica. We found that in each case the parental somy and allele contributions matched the inheritance patterns expected under meiosis 97–99% of the time. The hybrids were equivalent to F1 progeny, heterozygous throughout most of the genome for the markers that were homozygous and different between the parents. Rare, non-Mendelian patterns of chromosomal inheritance were observed, including a gain or loss of somy, and loss of heterozygosity, that likely arose during meiosis or during mitotic divisions of the progeny clones in the fly or culture. While the interspecies hybrids appeared to be sterile, the intraspecies hybrids were able to produce backcross and outcross progeny. Analysis of 5 backcross and outcross progeny clones generated from an L. major F1 hybrid, as well as 17 progeny clones generated from backcrosses involving a natural hybrid of L. tropica, revealed genome wide patterns of recombination, demonstrating that classical crossing over occurs at meiosis, and allowed us to construct the first physical and genetic maps in Leishmania. Altogether, the findings provide strong evidence for meiosis-like sexual recombination in Leishmania, presenting clear opportunities for forward genetic analysis and positional cloning of important genes.</div

Advanced acoustic emission source location in aircraft structural testing

Acoustic emission (AE) is an in situ Structural Health Monitoring (SHM) technique, where a structure is monitored for the ultrasonic waves produced due to crack growth. A major challenge with AE when applied to aircraft, and other complex structures, is that wave propagation is significantly affected by stiffeners, holes, thickness changes and other complexity. This reduces the accuracy of traditional source location techniques, that are based on a singular propagating wave speed. The Delta-T method enables higher levels of accuracy by mapping the structure and accounting for these changes. In this work AE monitoring equipment was installed on a section of an aluminium Airbus A320 wing. Location trials showed the Delta-T technique improved the average error from 85mm to 23mm, for artificial Hsu-Nielson sources, compared to the commercial standard technique. Testing under fatigue however demonstrated the challenges encountered when inspecting 3D structures (due to multiple signal paths) with significant levels of background noise. Of two cracks identified in the structure, the first of these was successfully detected and located, whilst the other was missed due to high machine noise and unrepresentative loading

Gene expression in Leishmania is regulated predominantly by gene dosage

ABSTRACT Leishmania tropica, a unicellular eukaryotic parasite present in North and East Africa, the Middle East, and the Indian subcontinent, has been linked to large outbreaks of cutaneous leishmaniasis in displaced populations in Iraq, Jordan, and Syria. Here, we report the genome sequence of this pathogen and 7,863 identified protein-coding genes, and we show that the majority of clinical isolates possess high levels of allelic diversity, genetic admixture, heterozygosity, and extensive aneuploidy. By utilizing paired genome-wide high-throughput DNA sequencing (DNA-seq) with RNA-seq, we found that gene dosage, at the level of individual genes or chromosomal “somy” (a general term covering disomy, trisomy, tetrasomy, etc.), accounted for greater than 85% of total gene expression variation in genes with a 2-fold or greater change in expression. High gene copy number variation (CNV) among membrane-bound transporters, a class of proteins previously implicated in drug resistance, was found for the most highly differentially expressed genes. Our results suggest that gene dosage is an adaptive trait that confers phenotypic plasticity among natural Leishmania populations by rapid down- or upregulation of transporter proteins to limit the effects of environmental stresses, such as drug selection. IMPORTANCE Leishmania is a genus of unicellular eukaryotic parasites that is responsible for a spectrum of human diseases that range from cutaneous leishmaniasis (CL) and mucocutaneous leishmaniasis (MCL) to life-threatening visceral leishmaniasis (VL). Developmental and strain-specific gene expression is largely thought to be due to mRNA message stability or posttranscriptional regulatory networks for this species, whose genome is organized into polycistronic gene clusters in the absence of promoter-mediated regulation of transcription initiation of nuclear genes. Genetic hybridization has been demonstrated to yield dramatic structural genomic variation, but whether such changes in gene dosage impact gene expression has not been formally investigated. Here we show that the predominant mechanism determining transcript abundance differences (>85%) in Leishmania tropica is that of gene dosage at the level of individual genes or chromosomal somy

A PHABULOSA/cytokinin feedback loop controls root growth in arabidopsis

The hormone cytokinin (CK) controls root length in Arabidopsis thaliana by defining where dividing cells, derived from stem cells of the root meristem, start to differentiate [ [1], [2], [3], [4], [5] and [6]]. However, the regulatory inputs directing CK to promote differentiation remain poorly understood. Here, we show that the HD-ZIPIII transcription factor PHABULOSA (PHB) directly activates the CK biosynthesis gene ISOPENTENYL TRANSFERASE 7 (IPT7), thus promoting cell differentiation and regulating root length. We further demonstrate that CK feeds back to repress both PHB and microRNA165, a negative regulator of PHB. These interactions comprise an incoherent regulatory loop in which CK represses both its activator and a repressor of its activator. We propose that this regulatory circuit determines the balance of cell division and differentiation during root development and may provide robustness against CK fluctuations

Acute exposure of mice to high-dose ultrafine carbon black decreases susceptibility to pneumococcal pneumonia

<p>Abstract</p> <p>Background</p> <p>Epidemiological studies suggest that inhalation of carbonaceous particulate matter from biomass combustion increases susceptibility to bacterial pneumonia. <it>In vitro </it>studies report that phagocytosis of carbon black by alveolar macrophages (AM) impairs killing of <it>Streptococcus pneumoniae</it>. We have previously reported high levels of black carbon in AM from biomass smoke-exposed children and adults. We therefore aimed to use a mouse model to test the hypothesis that high levels of carbon loading of AM <it>in vivo </it>increases susceptibility to pneumococcal pneumonia.</p> <p>Methods</p> <p>Female outbred mice were treated with either intranasal phosphate buffered saline (PBS) or ultrafine carbon black (UF-CB in PBS; 500 μg on day 1 and day 4), and then infected with <it>S. pneumoniae </it>strain D39 on day 5. Survival was assessed over 72 h. The effect of UF-CB on AM carbon loading, airway inflammation, and a urinary marker of pulmonary oxidative stress was assessed in uninfected animals.</p> <p>Results</p> <p>Instillation of UF-CB in mice resulted a pattern of AM carbon loading similar to that of biomass-smoke exposed humans. In uninfected animals, UF-CB treated animals had increased urinary 8-oxodG (P = 0.055), and an increased airway neutrophil differential count (P < 0.01). All PBS-treated mice died within 72 h after infection with S<it>. pneumoniae</it>, whereas morbidity and mortality after infection was reduced in UF-CB treated animals (median survival 48 h vs. 30 h, P < 0.001). At 24 hr post-infection, UF-CB treated mice had lower lung and the blood S<it>. pneumoniae </it>colony forming unit counts, and lower airway levels of keratinocyte-derived chemokine/growth-related oncogene (KC/GRO), and interferon gamma.</p> <p>Conclusion</p> <p>Acute high level loading of AM with ultrafine carbon black particles <it>per se </it>does not increase the susceptibility of mice to pneumococcal infection <it>in vivo</it>.</p

The influence of water absorption on the damage mechanism of unidirectional and 2D woven CFRP.

This study presents the influence of water exposure on unidirectional, plain weave, and twill weave CFRP particularly in the interfacial region. Specimens were exposed to 70°C water for 40 days and tested using the short-beam method to evaluate their interlaminar strength. This was conducted with the use of Acoustic Emission and Video Strain Gauge (an optical strain measurement). Scanning Electron Microscope was also used in this study. Results show weight increase of specimens due to water exposure by 1%, 0.94%, and 0.99% for unidirectional, plain and, twill, respectively. Furthermore, significant reductions in the short-beam strengths were observed for aged specimens. Acoustic emission showed promising initial results which can help to distinguish between the different damage mechanisms of aged and unaged specimens further enhancing the understanding of crack formation prior to final interlaminar failure. In addition, matrix cracking, fibre/fibre detachment, and fibre/matrix cracks were observed in the Scanning Electron Microscope results

Noise pollution: acute noise exposure increases susceptibility to disease and chronic exposure reduces host survival

Anthropogenic noise is a pervasive global pollutant that has been detected in every major habitat on the planet. Detrimental impacts of noise pollution on physiology, immunology and behaviour have been shown in terrestrial vertebrates and invertebrates. Equivalent research on aquatic organisms has until recently been stunted by the misnomer of a silent underwater world. In fish, however, noise pollution can lead to stress, hearing loss, behavioural changes and impacted immunity. But, the functional effects of this impacted immunity on disease resistance due to noise exposure have remained neglected. Parasites that cause transmissible disease are key drivers of ecosystem biodiversity and a significant factor limiting the sustainable expansion of the animal trade. Therefore, understanding how a pervasive stressor is impacting host–parasite interactions will have far-reaching implications for global animal health. Here, we investigated the impact of acute and chronic noise on vertebrate susceptibility to parasitic infections, using a model host–parasite system (guppy–Gyrodactylus turnbulli). Hosts experiencing acute noise suffered significantly increased parasite burden compared with those in no noise treatments. By contrast, fish experiencing chronic noise had the lowest parasite burden. However, these hosts died significantly earlier compared with those exposed to acute and no noise treatments. By revealing the detrimental impacts of acute and chronic noise on host–parasite interactions, we add to the growing body of evidence demonstrating a link between noise pollution and reduced animal health