Optical Sensing of Combustion Instabilities in Gas Turbines

In a continuing program of research and development, a system has been demonstrated that makes high-speed measurements of thermal infrared radiance from gas-turbine engine exhaust streams. When a gas-turbine engine is operated under conditions that minimize the emission of pollutants, there is a risk of crossing the boundary from stable to unstable combustion. Combustion instability can lead to engine damage and even catastrophic failure. Sensor systems of the type under development could provide valuable data during the development testing of gas-turbine engines or of engine components. A system of the type under development makes high-speed measurements of thermal infrared radiance from the engine exhaust stream. The sensors of this system can be mounted outside the engine, which eliminates the need for engine case penetrations typical with other engine dynamics monitors. This is an important advantage in that turbine-engine manufacturers consider such penetrations to be very undesirable. A prototype infrared sensor system has been built and demonstrated on a turbine engine. This system includes rugged and inexpensive near-infrared sensors and filters that select wavelengths of infrared radiation for high sensitivity. In experiments, low-frequency signatures were consistently observed in the detector outputs. Under some conditions, the signatures also included frequency components having one or two radiance cycles per engine revolution. Although it has yet to be verified, it is thought that the low-frequency signatures may be associated with bulk-mode combustion instabilities or flow instabilities in the compressor section of the engine, while the engine- revolution-related signatures may be indicative of mechanical problems in the engine. The system also demonstrated the ability to detect transient high-radiance events. These events indicate hot spots in the exhaust stream and were found to increase in frequency during engine acceleration

Modelling of focused wave interaction with wave energy converter models using qaleFOAM

This paper presents a numerical investigation on the interaction between focused waves and wave energy converter (WEC) models using a hybrid solver, qaleFOAM, which couples a two-phase incompressible Navier–Stokes (NS) solver OpenFOAM/InterDyMFoam with the quasi Lagrangian–Eulerian finite element method (QALE-FEM) based on the fully non-linear potential theory (FNPT) using the domain-decomposition approach. In the qaleFOAM, the NS solver deals with a small region near the structures (NS domain), where the viscous effect may be significant; the QALE-FEM covers the remaining computational domain (FNPT domain); an overlap (transitional) zone is applied between two domains. The WEC models, mooring system and the wave conditions are given by the CCP-WSI (Collaborative Computational Project in Wave–Structure Interaction) Blind Test Series 2. In the numerical simulation, the incident wave is generated in the FNPT domain using a self-correction wavemaker and propagates into the NS domain through the coupling boundaries and attached transitional zones. An improved passive wave absorber is imposed at the outlet of the NS domain for wave absorption. The practical performance of the qaleFOAM is demonstrated by comparing its prediction with the experimental data, including the wave elevation, motion responses (surge, heave and pitch) and mooring load

Two waves of de novo methylation during mouse germ cell development

During development, mammalian germ cells reprogram their epigenomes via a genome-wide erasure and de novo rewriting of DNA methylation marks. We know little of how methylation patterns are specifically determined. The piRNA pathway is thought to target the bulk of retrotransposon methylation. Here we show that most retrotransposon sequences are modified by default de novo methylation. However, potentially active retrotransposon copies evade this initial wave, likely mimicking features of protein-coding genes. These elements remain transcriptionally active and become targets of piRNA-mediated methylation. Thus, we posit that these two waves play essential roles in resetting germ cell epigenomes at each generation

Study protocol for the online adaptation and evaluation of the ‘Reboot’ (Recovery-boosting) coaching programme, to prepare critical care nurses for, and aid recovery after, stressful clinical events

Background Critical care nurses (CCNs) are routinely exposed to highly stressful events, exacerbated during the COVID-19 pandemic. Supporting resilience and wellbeing of CCNs is therefore crucial to prevent burnout. One approach for delivering this support is by preparing critical care nurses for situations they may encounter, drawing on evidence-based techniques to strengthen relevant psychological coping strategies. As such, the current study seeks to tailor a Resilience-boosting psychological coaching programme [Reboot] for CCNs, based on cognitive behavioural therapy (CBT) principles and the Bi-Dimensional Resilience Framework (BDF), and (1) to assess the feasibility of delivering Reboot via online, remote delivery to CCNs, and (2) to provide a preliminary assessment of whether Reboot could increase resilience and confidence in coping with adverse events. Methods Eighty CCNs (n=80) will be recruited to the 8-week Reboot programme, comprised of two group workshops and two individual coaching calls. The study uses a single-arm before-after feasibility study design and will be evaluated with a mixed-methods approach, using online questionnaires (all participants) and telephone interviews (25% of participants). Primary outcomes will be confidence in coping with adverse events (the Confidence scale) and resilience (the Brief Resilience Scale) measured at four time points. Discussion Results will determine whether it is feasible to deliver and evaluate a remote version of the Reboot coaching programme to CCNs, and will indicate whether participating in the programme is associated with increases in confidence in coping with adverse events, resilience and wellbeing (as indicated by levels of depression)

Profiling essential genes in human mammary cells by multiplex RNAi screening

By virtue of their accumulated genetic alterations, tumor cells may acquire vulnerabilities that create opportunities for therapeutic intervention. We have devised a massively parallel strategy for screening short hairpin RNA (shRNA) collections for stable loss-of-function phenotypes. We assayed from 6000 to 20,000 shRNAs simultaneously to identify genes important for the proliferation and survival of five cell lines derived from human mammary tissue. Lethal shRNAs common to these cell lines targeted many known cell-cycle regulatory networks. Cell line-specific sensitivities to suppression of protein complexes and biological pathways also emerged, and these could be validated by RNA interference (RNAi) and pharmacologically. These studies establish a practical platform for genome-scale screening of complex phenotypes in mammalian cells and demonstrate that RNAi can be used to expose genotype-specific sensitivities

Generation of transgenic drosophila expressing shRNAs in the miR-1 backbone

In Drosophila, long-term effects of RNA interference (RNAi) must be achieved by integrating into the genomea template fromwhich anRNAi trigger is transcribed by cellularRNApolymerases, generallyRNA polymerase II or III. With encoded triggers, not only can essentially permanent silencing be achieved, but control can also be exerted over the level of trigger expression, with a resulting variation in the degree to which the target is silenced. Knockdown can also be controlled in a temporal and cell-type-dependent fashionthroughtheuseofwell-establishedtransgenicmethodologiesandwell-testedpromoters.The forms of encoded triggers vary. Long double-stranded RNAs can be expressed as extended inverted repeats. The nearest equivalent of a small interfering RNA is an artificial microRNA (miRNA) or short hairpin RNA (shRNA),whereanaturalmiRNAbackbone(alsocalledascaffold) isremodeledtoproduceadifferent small RNA or a small inverted repeat (<30 nucleotides) is simply expressed. This protocol describes creation of transgenic Drosophila carrying shRNAinserts in a remodeled endogenousmiRNAbackbone.The protocol applies to the use of miRNA-based shRNAs, butmost of the vectors, principles of experimental design, and methods are also applicable to long inverted repeat transgenes

Packaging shRNA retroviruses

To silence a mammalian gene by RNAi using an encoded trigger, a short-hairpin RNA (shRNA) is integrated into the host cell genome as a stable transgene. Target cells are infected with viral plasmid containing shRNA inserted into the vector backbone. Before infection, the plasmid is transfected into a packaging cell line, which provides the trans-acting factors necessary for virus production. These include, minimally, capsid proteins and reverse transcriptase, but they can also include other regulatory factors (e.g., tat for some lentiviral vectors). It is critical to choose the correct packaging cell system for the viral backbone to be used. The packaging cell also defines the host range of the virus, depending on the envelope protein that it expresses. Ecotropic viruses are limited to rodent hosts, whereas amphotropic viruses have a broader host range that also includes humans. Often, investigators will express a nonretroviral envelope, such as vesicular stomatitus virus (VSV) glycoprotein, to enhance virus stability and host range and to enable viruses to be concentrated following production. Although viruses carrying shRNAs are packaged almost identically to viruses carrying protein-encoding genes, one twist is worth noting. shRNAs are efficiently cleaved by the host RNAi biogenesis machinery, which can reduce the level of viral genomic RNAs and consequently viral titers. Therefore, titers can be enhanced by cotransfecting the viral plasmid with a small interfering RNA (siRNA) that targets DGCR- 8/Pasha, which is a core microRNA (miRNA) biogenesis component. siRNAs against Drosha can also be used

Creating an miR30-based shRNA vector

Generating expression constructs for artificial microRNAs (miRNAs) is relatively straightforward. This protocol describes the creation of miR-30-based short hairpin RNA (shRNA) cassettes that are compatible with a number of standard vector systems. The principles outlined here can also be easily applied to other miRNA scaffolds or to simple snapback shRNAs. It is important to note that one must understand the processing of the artificial scaffold and be able to predict precisely the small RNAs that will be generated. Otherwise, no design principles can be effectively applied and the probability that any individual shRNA clone will work effectively will be greatly reduced

Infection of mammalian cells with retroviral shRNAs

Viral infection is a quite simple approach for stably introducing transgenes (e.g., those encoding shorthairpin RNAs [shRNAs]) into the genome. The critical aspects are that the virus and the target cell should be appropriately matched. For example, a virus bearing an ecotropic envelope protein will not infect a human cell line unless the appropriate receptor has been purposefully expressed. VSV-G (vesicular stomatitus virus glycoprotein) pseudotyped viruses have the greatest host range. Nondividing cells can only be infected with lentiviruses, but the additional safety precautions necessary for the use of these tools should dissuade their application to routinely cultured cell lines