Thermoplastic coating of carbon fibers

A continuous powder coating system was developed for coating carbon fiber with LaRC-TPI (Langley Research Center-Thermoplastic Polyimide), a high-temperature thermoplastic polymide invented by NASA-Langley. The coating line developed used a pneumatic fiber spreader to separate the individual fibers. The polymer was applied within a recirculating powder coating chamber then melted using a combination of direct electrical resistance and convective heating to make it adhere to the fiber tow. The tension and speed of the line were controlled with a dancer arm and an electrically driven fiber wind-up and wind-off. The effects of heating during the coating process on the flexibility of the prepreg produced were investigated. The uniformity with which the fiber tow could be coated with polymer also was examined. Composite specimens were fabricated from the prepreg and tested to determine optimum process conditions. The study showed that a very uniform and flexible prepeg with up to 50 percent by volume polymer could be produced with this powder coating system. The coating line minimized powder loss and produced prepeg in lengths of up to 300 m. The fiber spreading was found to have a major effect on the coating uniformity and flexibility. Though test results showed low composite tensile strengths, analysis of fracture surfaces under scanning electron microscope indicated that fiber/matrix adhesion was adequate

Leveling coatings for reducing the atomic oxygen defect density in protected graphite fiber epoxy composites

Pinholes or other defect sites in a protective oxide coating provide pathways for atomic oxygen in low Earth orbit to reach underlying material. One concept of enhancing the lifetime of materials in low Earth orbit is to apply a leveling coating to the material prior to applying any reflective and protective coatings. Using a surface tension leveling coating concept, a low viscosity epoxy was applied to the surface of several composite coupons. A protective layer of 1000 A of SiO2 was deposited on top of the leveling coating, and the coupons were exposed to an atomic oxygen environment in a plasma asher. Pinhole populations per unit area were estimated by counting the number of undercut sites observed by scanning electron microscopy. Defect density values of 180,000 defects/sq cm were reduced to about 1000 defects/sq cm as a result of the applied leveling coating. These improvements occur at a mass penalty of about 2.5 mg/sq cm

Consequences on ethylene metabolism of inactivating the ethylene receptor sites in diseased non-climacteric fruit

Abstract Penicillium digitatum-infected grapefruit synthesize large quantities of the stress hormone ethylene. The compound 1-methylcyclopropene (1-MCP) inhibits the binding of ethylene to the ethylene receptor site, the ethylene binding protein (EBP). Treating infected fruit with 1-MCP prevented infection-induced degreening, such that fumigated fruit retained their green immature color compared to yellow non-fumigated controls. However, 1-MCP treatment significantly increased whole fruit ethylene production. In flavedo tissue of infected non-1-MCP treated fruit, 1-aminocyclopropane-1-carboxylate (ACC) synthase transcript accumulation, ACC synthase (ACS) enzyme activity, ACC and ethylene synthesis were all significantly higher + 5 mm ahead of the lesion front than in uninfected non-1-MCP treated controls, but decreased significantly with increased sampling distance away from the lesion. 1-MCP treatment increased ethylene production in infected fruit at all three sampling distances compared to the non-fumigated samples. Even in the absence of infection, 1-MCP treatment resulted in increased ethylene synthesis. The results suggest that, in the presence of a pathogenic stress, blocking the EBPs prevented regulatory control of the ethylene biosynthetic pathway that resulted in an uninhibited expression of the ACS stress-associated genes, increased ACS activity and elevated ACC accumulation and ethylene production. Blocking of the EBPs with 1-MCP did not affect progression of the pathogen through the fruit. Published by Elsevier Science B.V

Thermoplastic coating of carbon fibers

Now that quantities of prepreg were made on the thermoplastic coating line, they are being formed into both textile preform structures and directly into composite samples. The textile preforms include both woven and knitted structures which will be thermoformed into a finished part. In order to determine if the matrix resin is properly adhering to the fibers or if voids are being formed in the coating process, the tensile strength and modulus of these samples will be tested. The matrix uniformity of matrix distribution in these samples is also being determined using an image analyzer

Renormalization Group Analysis of a Quivering String Model of Posture Control

Scaling concepts and renormalization group (RG) methods are applied to a simple linear model of human posture control consisting of a trembling or quivering string subject to damping and restoring forces. The string is driven by uncorrelated white Gaussian noise intended to model the corrections of the physiological control system. We find that adding a weak quadratic nonlinearity to the posture control model opens up a rich and complicated phase space (representing the dynamics) with various non-trivial fixed points and basins of attraction. The transition from diffusive to saturated regimes of the linear model is understood as a crossover phenomenon, and the robustness of the linear model with respect to weak non-linearities is confirmed. Correlations in posture fluctuations are obtained in both the time and space domain. There is an attractive fixed point identified with falling. The scaling of the correlations in the front-back displacement, which can be measured in the laboratory, is predicted for both the large-separation (along the string) and long-time regimes of posture control.Comment: 20 pages, 13 figures, RevTeX, accepted for publication in PR

Multicenter study of hypoxemia prevalence and quality of oxygen treatment for hospitalized Malawian children

Although hypoxemic children have high mortality, little is known about hypoxemia prevalence and oxygen administration in African hospitals. We aimed to determine the hypoxemia prevalence and quality of oxygen treatment by local clinicians for hospitalized Malawian children

Maternal mental well-being and recent child illnesses–A cross-sectional survey analysis from Jigawa State, Nigeria

Child health indicators in Northern Nigeria remain low. The bidirectional association between child health and maternal well-being is also poorly understood. We aim to describe the association between recent child illness, socio-demographic factors and maternal mental well-being in Jigawa State, Nigeria. We analysed a cross-sectional household survey conducted in Kiyawa local government area, Jigawa State, from January 2020 to March 2020 amongst women aged 16–49 with at least one child under-5 years. We used two-stage random sampling. First, we used systematic random sampling of compounds, with the number of compounds based on the size of the community. The second stage used simple random sampling to select one eligible woman per compound. Mental well-being was assessed using the Short Warwick-Edinburgh Mental Wellbeing Score (SWEMWBS). We used linear regression to estimate associations between recent child illness, care-seeking and socio-demographic factors, and mental well-being. Overall 1,661 eligible women were surveyed, and 8.5% had high mental well-being (metric score of 25.0–35.0) and 29.5% had low mental well-being (metric score of 7.0–17.9). Increasing wealth quintile (adj coeff: 1.53; 95% CI: 0.91–2.15) not being a subsistence farmer (highest adj coeff: 3.23; 95% CI: 2.31–4.15) and having a sick child in the last 2-weeks (adj coeff: 1.25; 95% CI: 0.73–1.77) were significantly associated with higher mental well-being. Higher levels of education and increasing woman’s age were significantly associated with lower mental well-being. Findings contradicted our working hypothesis that a recently sick child would be associated with lower mental well-being. We were surprised that education and late marriage, which are commonly attributed to women’s empowerment and autonomy, were not linked to better well-being here. Future work could focus on locally defined tools to measure well-being reflecting the norms and values of communities, ensuring solutions that are culturally acceptable and desirable to women with low mental well-being are initiated

Community perceptions matter: a mixed-methods study using local knowledge to define features of success for a community intervention to improve quality of care for children under-5 in Jigawa, Nigeria

Objectives In this study, we used the information generated by community members during an intervention design process to understand the features needed for a successful community participatory intervention to improve child health. Design We conducted a concurrent mixed-methods study (November 2019–March 2020) to inform the design and evaluation of a community–facility linkage participatory intervention. Setting Kiyawa Local Government Area (Jigawa State, Nigeria)—population of 230 000 (n=425 villages). Participants Qualitative data included 12 community conversations with caregivers of children under-5 (men, older and younger women; n=9 per group), 3 focus group discussions (n=10) with ward development committee members and interviews with facility heads (n=3). Quantitative data comprised household surveys (n=3464) with compound heads (n=1803) and women (n=1661). Results We analysed qualitative data with thematic network analysis and the surveys with linear regression—results were triangulated in the interpretation phase. Participants identified the following areas of focus: community health education; facility infrastructure, equipment and staff improvements; raising funds to make these changes. Community involvement, cooperation and empowerment were recognised as a strategy to improve child health, and the presence of intermediate bodies (development committees) was deemed important to improve communication and solve problems between community and facility members. The survey showed functional community relations’ dynamics, with high levels of internal cohesion (78%), efficacy in solving problems together (79%) and fairness of the local leaders (82%). Conclusions Combining the results from this study and critical theories on successful participation identified community-informed features for a contextually tailored community–facility link intervention. The need to promote a more inclusive approach to future child health interventions was highlighted. In addition to health education campaigns, the relationship between community and healthcare providers needs strengthening, and development committees were identified as an essential feature for successfully linking communities and facilities for child health. Trial registration number ISRCTN39213655

Marginalization of end-use technologies in energy innovation for climate protection

Mitigating climate change requires directed innovation efforts to develop and deploy energy technologies. Innovation activities are directed towards the outcome of climate protection by public institutions, policies and resources that in turn shape market behaviour. We analyse diverse indicators of activity throughout the innovation system to assess these efforts. We find efficient end-use technologies contribute large potential emission reductions and provide higher social returns on investment than energy-supply technologies. Yet public institutions, policies and financial resources pervasively privilege energy-supply technologies. Directed innovation efforts are strikingly misaligned with the needs of an emissions-constrained world. Significantly greater effort is needed to develop the full potential of efficient end-use technologies