Effect of a chromium-containing fuel additive on hot corrosion

Four cast superalloys (one cobalt-base and three nickel-base) were tested at 900°C for 100 h in Mach 0.3 combustion gases. 5 ppm of synthetic sea salt were added to the gases in the combustion chamber. Several types of thermal cycle and washing procedures were employed. Similar tests were made with the addition of 300 ppm of a chromium-containing fuel additive. In both sets of tests the extent of hot corrosion was evaluated by specific weight change and metal recession. In general, the chromium additive in the fuel reduced the extent of hot (salt) corrosion but did not eliminate it. The percentage reduction of hot corrosion attack was similar for all four alloys. As great a reduction of hot corrosion was achieved by reducing the number of thermal cycles during the test from 100 to 5 of 6. The effect of washing the alloys every ten cycles as opposed to the end of the test was erratic; some alloys were attacked slightly more, others somewhat less. A NiCrAlY coating was found to be more effective in reducing hot corrosion than either the fuel additive or the washing schedule.     

Thermal expansion in the Ni−Cr−Al and Co−Cr−Al systems to 1200°C determined by high-temperature X-ray diffraction

The effect of temperature on the lattice parameters of phases in twelve nickel-chromium-aluminum (Ni?Cr?Al) alloys and nine cobalt-chromium-aluminum (Co?Cr?Al) alloys was determined using high temperature diffraction (HTXRD). The temperature range was from 25 to 1200°C. The data for each phase of each alloy were computer fit to an empirical thermal expansion equation developed in this study: \(LP_T = LP_{25^\circ C} (1 + R)^{(1 + T/273)^{1.5} } \) and a value forR was derived for each. Excellent fits were obtained for nearly all cases. A comparison ofR values revealed that for a given phase (ψ/ψ′, β and α in Ni?Cr?Al and αCo and β in Co?Cr?Al),R was independent of alloy composition. In the Ni?Cr?Al systemR for γ/γ′ was 19.2×10^?4,R for β was 19.9×10^?4 andR for αCr was 13.4×10^?4. In the Co?Cr?Al system theR value for αCo was 20.9×10^?4 and theR for β was 17.8×10^?4. Of all of the phases only the αCr in the Ni?Cr?Al system had anR sufficiently low to reduce to an unimportant level the stress generated from thermal expansion mismatch between Al₂O₃ and substrate or coating and substrate with either Ni?Al or Co?Al coatings on a γ/γ′-δ substrate.     

Characterization of the skin orientation of thermotropic liquid‐crystalline copolyester moldings with near‐edge X‐ray absorption fine structure

The process of injection‐molding net‐shape parts from thermotropic liquid‐crystalline polymers results in a skin‐core macrostructure. The underlying orientation in the core and the skin may differ both in magnitude and direction. A combination of near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy and two‐dimensional wide‐angle X‐ray scattering (2D WAXS) in transmission was used to characterize the orientation in injection‐molded plaques fabricated from thermotropic liquid‐crystalline copolyesters based on either 4,4′‐dihydroxy‐α‐methylstilbene or 6‐hydroxy‐2‐naphthoic acid/6‐hydroxybenzoic acid. NEXAFS is presented as a noninvasive in situ means of determining surface layer orientation that samples to a depth of as little as 2 nm and does not require slicing or ultramicrotoming of the samples. The effects of various processing conditions on the surface orientation in the region of the centerline of square injection‐molded plaques are presented and discussed. Comparisons are made between orientation parameters obtained by 2D WAXS in transmission, which is dominated by the microstructure in the core, and the NEXAFS technique. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2473–2480, 2005     

Ageing and Care Giving in the United States: Policy Contexts and the Immigrant Workforce

The ageing population of the United States is generating an increasing demand for care and foreign-born workers will supply an important part of that demand. This article discusses the ways in which U.S. healthcare and immigration policies affect the supply of the foreign born to professional and lesser skilled, direct care jobs. The U.S. market for long term care is shifting away from hospitals and institutionalised facilities to the direct provision of private services and long term care in homes. A well designed immigration policy would complement the demand generated by the healthcare system. Yet, there are few dedicated avenues of legal admission that select for professional care workers and none at all that target direct care workers. There is concern over shortages of professional workers and a substantial number of unauthorized workers in direct care work that flag deficiencies in immigration policies. Our examination of data, nevertheless, finds that the foreign born play an important role in the supply of workers. In the provision of direct care they are roughly one-quarter of the workforce that provides 80% of all long term care. Among professional care workers they are highly concentrated in the home care industry. These national-level concentrations, however, do not fully reveal the remarkable concentration of immigrants in just a few metropolitan areas.     

Adhesion-dependent degranulation of neutrophils requires the Src family kinases Fgr and Hck

Polymorphonuclear neutrophils (PMN) adherent to integrin ligands respond to inflammatory mediators by reorganizing their cytoskeleton and releasing reactive oxygen intermediates. As Src family tyrosine kinases are implicated in these responses, we investigated their possible role in regulating degranulation. Human PMN incubated on fibrinogen released lactoferrin in response to TNF-alpha and this response was inhibited by PP1, a Src family tyrosine kinase inhibitor. This drug had no effect on lactoferrin secretion induced by PMA, an adhesion-independent agonist of PMN degranulation. However, PP1 blocked secretion in PMN plated on plain tissue culture plastic, a surface inducing PMN spreading in the absence of any stimulus. Double knockout hck-/- fgr-/- PMN adherent to collagen or fibrinogen failed to release lactoferrin in response to TNF-alpha but responded to PMA as wild-type PMN. Degranulation induced by spreading over tissue culture plastic was also defective in hck-/- fgr-/- PMN. Defective adhesion-dependent degranulation required the absence of both kinases, because single knockout fgr-/- or hck-/- PMN responded as wild-type cells. Analysis of lactoferrin secretion in hck-/- fgr-/- or PP1-treated, suspended PMN showed that Src kinases are not implicated in degranulation dependent on activation of protein kinase C or increase in intracellular free Ca2+ but may play a role in the response to FMLP of cytochalasin B-treated PMN. These findings identify a role for Src family kinases in a signaling pathway leading to granule-plasma membrane fusion and suggest that Fgr and Hck would be targets for pharmacological control of adhesion-dependent degranulation in the inflammatory site.     

A proof of the spherical homeomorphism conjecture for surfaces

The human cerebral cortex is topologically equivalent to a sphere when it is viewed as closed at the brain stem. Due to noise and/or resolution issues, magnetic resonance imaging may see "handles" that need to be eliminated to reflect the true spherical topology. Shattuck and Leahy present an algorithm to correct such an image. The basis for their correction strategy is a conjecture, which they call the spherical homeomorphism conjecture, stating that the boundary between the foreground region and the background region is topologically spherical if certain associated foreground and background multigraphs are both graph-theoretic trees. In this paper, we prove the conjecture, and its converse, under the assumption that the foreground/background boundary is a surface.     

Decreased discrimination as a function of increased drive.

In 2 samples of psychiatric patients, an increase in drive induced by gripping a hand dynamometer led to a decrease in discrimination characterized by a reduction in an appropriate response at its training stimulus. The drive also facilitated generalized dominant responses and did not increase anxiety. It was concluded that a decrease in appropriate behavior can result from an increase in a nonaversive drive. The results were in accord with a theoretical account utilizing constructs from Hull-Spence theory and including a lowered reaction potential ceiling. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)