CORRELATION OF SHORT-TERM TO LONG-TERM OXIDATION TESTING FOR ALUMINA FORMING ALLOYS AND COATINGS

Engineering long cyclic oxidation life of high temperature materials requires success on two fronts. First a slow growing protective oxide scale must form during the elevated temperature exposure. To satisfy this aspect, alumina-forming alloys and coatings are widely accepted as leading materials for use in this environment and are the focus of this discussion. The second aspect is the formation of an adherent oxide that resists spallation during thermal cycling. The driving force for spallation is the stored elastic strain energy that develops from stresses in the oxide scale. Once this stored elastic strain energy exceeds the oxide-substrate interfacial toughness, cracking and subsequent spallation occurs followed by rapid oxidation of the substrate. With advances in alloy and coating development resulting in higher operating temperatures and increased service lives, researchers are faced with excessive laboratory time and cost required to perform a long-term cyclic oxidation test.The challenge is to predict long-term oxidation behavior from short-term experiments. Since the rate limiting step to high temperature oxidation is a thermally activated process, previous investigations were performed at increased exposure temperatures for rapid degradation of the alloys and coatings to rank material performance. Others have mechanically induced oxide spallation to give insight on the adherence of oxide scales prior to spontaneous failure. In this investigation, short-term testing is employed to gain insight on long-term performance and to determine inputs into a cyclic oxidation model for life-time prediction. This model operates in an iterative process where one iteration is a thermal cycle. The amount of oxide formed during the high temperature segment is calculated followed by the amount that is lost due to scale spallation during cooling. Retained oxide at the end of this cycle is used as the starting point for the following iteration. The two inputs into this model are the oxide scale growth and spallation behavior. Scale growth behavior corresponds to the isothermal growth kinetics that are experimentally determined by thermogravimetric analysis. Oxide scale spallation behavior is quantified by two short-term experiments of a novel acoustic emission experiment during a 24 hour exposure and the stress measurement of the scale after an exposure to the temperature of interest. Results from these short-term tests and modeled cyclic oxidation are compared to life-times from long-term cyclic oxidation tests

Anasazi Diet: The Corpolite Evidence

Prehistoric coprolites (dessicated human fecal material) from the Anasazi region of the American Southwest are examined for the purpose of dietary reconstruction. Using published reports and unpublished data on 179 coprolites from Basketmaker (A.D. 600) to late Pueblo III (A.D. 1250) proveniences, a widespread cultural-ecological adaptation to the plateau area of the Four-corners area is illustrated through diet. iii A few major trends through time are noted for the Anasazi populations. Changes in the use of cultivated plants are increasing use of seed crops (i.e. corn and cotton), and decrease of squash in the diet. In addition, later populations utilized a wide variety of weed plants that would be found around disturbed areas and concentrated less on pinon nut consumption. These trends are seen as a shift in subsistence strategies due to population pressure and widespread ecological disturbance, attributed to temperate latitude swidden farming methods and cultural effects on the ecosystem. The Anasazi, due to these ecological imbalances were forced to eventually abandon the area

Potentiality of Using Spreading Sargassum Species From Indonesia as an Interesting Source of Antibacterial and Radical Scavenging Compounds: a Preliminary Study

As an archipelagic country with 95,181 km long coastline, Indonesia has great potential as the producer of seaweeds. The diverse phyla of marine macroalgae (red, brown and green seaweeds) are known to produce molecules which are attractive for diverse industries. Applications of algal products range from simple biomass production for food, feed and fuels to valuable products such as sugar polymers, cosmetics, pharmaceuticals, pigments, and food supplements. Seaweeds also have the potential to be used as a source of new bioactive for human, animal or plant health, as well as a source of new synthons and biocatalysts in sustainable chemistry (Bourgougnon and Stiger-Pouvreau, 2011). In this paper, among species of economic value we focus on brown seaweeds belonging to family Sargassaceae and genus Sargassum spreading along Indonesian coasts. Members of this genus are especially abundant in tropical and subtropical regions (Zemke-White and Ohno, 1999). The purpose of this study is to analyze the antibacterial and antioxidant activity of three species of Sargassum, i.e. S. echinocarpum, S. duplicatum and S. polycystum. Both polar and non-polar extracts have been prepared from those three species. In vitro antibacterial activities of extracts were evaluated against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli. Results indicated all the three species tested showed an antibacterial activity. The most effective antibacterial activity against S. aerous was from S. echinocarpum with ethil asetat, inhibition zone 1.13 ± 0.25 mm; S. duplicatum with N-Hexane was most effective against E. coli, 1.20 ± 0.28 mm

Evaluation of chloride stress corrosion susceptibility of stainless steels

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Research to understand and predict geopressured reservoir characteristics with confidence

The Department of Energy's Geopressured Geothermal Program has sponsored a series of geoscience studies to resolve key uncertainties in the performance of geopressured reservoirs. The priority areas for research include improving the ability to predict reservoir size and flow capabilities, understanding the role of oil and gas in reservoir depletion and evaluating mechanisms for reservoir pressure maintenance. Long-term production from the Gladys McCall well has provided the basis for most of the current research efforts. The well was shut-in on October 29, 1987, for pressure recovery after producing over 27 million barrels of brine with associated gas. Geologic investigations are evaluating various mechanisms for pressure maintenance in this reservoir, including recharge from adjacent reservoirs or along growth faults, shale dewatering, and laterally overlapping and connected sandstone layers. Compaction studies using shale and sandstone core samples have provided data on the relationship between rock compression and reservoir pressure decline and the correlation to changes in porosity and permeability. The studies support the use of a porosity-coupled reservoir simulation model which has provided an excellent match to the well's production history. 10 refs., 3 figs

Characteristic length of random knotting for cylindrical self-avoiding polygons

We discuss the probability of random knotting for a model of self-avoiding polygons whose segments are given by cylinders of unit length with radius $r$. We show numerically that the characteristic length of random knotting is roughly approximated by an exponential function of the chain thickness $r$.Comment: 5 pages, 4 figure

The effects of inspiratory muscle training on inspiratory muscle strength, lung function and quality of life in adults with spinal cord injuries: A systematic review and Meta-analysis

Purpose: This systematic review and meta-analysis aimed to evaluate the effectiveness of inspiratory muscle training (IMT) on respiratory muscle strength, lung function and quality of life (QOL) in adults with spinal cord injuries (SCI). Methods: Databases were searched up to June 2022; CENTRAL, CINAHL, MEDLINE, PEDRo, and PubMed. Following PRISMA reporting guidelines, two independent reviewers selected studies and extracted data. Study quality and levels of evidence were assessed. Results: Following selection from 624 initial search results, six randomised controlled trials were identified, comprising 124 participants. Quality of Evidence was very low to moderate. Meta-analysis showed that post intervention, IMT significantly improved maximal inspiratory pressure (MD 15.72 cmH2O, 95% CI 5.02, 26.41, p ¼ 0.004) when compared with a control intervention. There was no significant benefit for physical QOL (SMD 0.12, 95% CI 1.01, 1.25, p ¼ 0.84), mental QOL (SMD 0.2, 95% CI 1.72, 1.33, p ¼ 0.80), maximal expiratory pressure (MD 5.19 cmH2O, 95% CI 4.16, 14.55, p ¼ 0.80), or FEV1 (MD 0.26 L, 95% CI 0.19, 0.7, p ¼ 0.26). Sensitivity analyses found larger effects for studies with 8 week interventions (MD 17.5 cmH2O (95% CI 3.36 to 31.66)) and spring loaded devices alone (MD 21.18 cmH2O, 95% CI 9.65 to 32.72). Conclusion: Moderate quality evidence suggests IMT improves respiratory strength in adults with an SCI. The mental and physical QOL outcomes provided very low quality of evidence, with considerable heterogeneity between study results, leading to inconsistency. Further research is warranted to investigate medium and long-term impact of robust IMT protocols, accounting for patient motivation and adherence t