Effects of surface chemistry on hot corrosion life

Hot corrosion life prediction methodology based on a combination of laboratory test data and field service turbine components, which show evidence of hot corrosion, were examined. Components were evaluated by optical metallography, scanning electron microscopy (SEM), and electron micropulse (EMP) examination

Effects of surface chemistry on hot corrosion life

Burner rig tests were conducted under the following conditions: 900 C, hourly thermal cycling, 0.5 ppm sodium as NaCl in the gas stream, and Mach 0.3 velocity. The alloys tested were Udimet 700 (U700) and Rene 80, uncoated and with RT21, Codep, or NiCoCrAlY coatings. The tests, up to 1000 hours, included specimens in the as-processed condition and after aging at 1100 C in oxidizing or inert environments for up to 600 hours. Coil-inductance changes were measured for periodic nondestructive inspection of speciments and found useful in the following course of corrosion. Typical sulfidation observed in all cases was similar to that observed in service-run turbine components. Aging at 1100 C caused severe decrease in the hot corrosion life of RT21 and Codep coatings and a significant but lesser decrease in the life of NiCoCrAlY coatings. The extent of these decreases was much greater for all three coatings on U700 than on Rene substrates. A coating hot corrosion life-predicitin model was proposed. The model requires time/temperature information for a turbine component at takeoff conditions as well as environmental contaminant information

Effects of surface chemistry on hot corrosion life

This program has its primary objective: the development of hot corrosion life prediction methodology based on a combination of laboratory test data and evaluation of field service turbine components which show evidence of hot corrosion. The laboratory program comprises burner rig testing by TRW. A summary of results is given for two series of burner rig tests. The life prediction methodology parameters to be appraised in a final campaign of burner rig tests are outlined

Studies on cultured Schwann cells: the induction of myelin synthesis, and the control of their proliferation by a new growth factor

We have recently described the use of immunological methods to identify and purify rat Schwann cells. In dissociated cultures of neonatal sciatic nerve, all of the cells can be identified by antigenic criteria as either Schwann cells or fibroblasts. The fibroblasts may be removed by treatment with antiserum to the Thy-1 antigen and complement. The purified Schwann cells have been used to study the regulation of the expression of myelin components, and the stimulation of Schwann cell division by a soluble growth factor. Among the components of myelin, we have concentrated on the peripheral myelin glycoprotein P_0, which constitutes 50–60% of the protein in peripheral myelin. We have studied the distribution of P_0 in vitro and in vivo by immunofluorescence, immuno-autoradiography on SDS gels, and solid-phase radioimmunoassay. Our results support the hypothesis that P_0 is induced specifically as a consequence of the interaction between the Schwann cell and the myelinated type of axon. The level of P_0 in the myelin membrane is at least 1000-fold higher than in the Schwann cell membrane. Purified Schwann cells divide very slowly in a conventional tissue culture medium. This has allowed us to purify a new growth factor from extracts of brain and pituitary, tentatively named Glial Growth Factor (GGF). The activity resides in a basic protein with a native molecular weight of 6 × 10^4 daltons and a subunit molecular weight of 3 × 10^4 daltons, which is active at levels comparable to those of epidermal growth factor. GGF is mitogenic for Schwann cells, astrocytes and muscle fibroblasts

The Story of John Fryxell

John Fryxell was an immigrant from Vättlösa Parish, near Götene in southern Sweden. He came to America and worked for the Moline Cabinet Pipe Organ Company of Moline, Illinois and was an advocate of education for his children, all of whom graduated from Augustana College in Rock Island, Illinois. His son Fritiof Fryxell wrote the manuscript of this biography of his father.https://digitalcommons.augustana.edu/ahsbooks/1006/thumbnail.jp

Tutankhamen, Egyptomania, and Temporal Enchantment in Interwar Britain.

In 1923 or thereabouts, Britain fell under the ‘Tut-ankh-amen spell’. Howard Carter and Lord Carnarvon’s discovery of Tutankhamen’s tomb in 1922 prompted a new wave of popular interest in ancient Egypt that suffused British culture, casting Tutankhamen’s ‘spell’ over movies, music, mummies, and more.2 Reinvigorated ‘Egyptian’ styles in architecture, interior design, and commodities capitalized upon the visual motifs of eighteenth- and nineteenth-century ‘Egyptomanias’. Though distinct for its mass commodification, interwar Egyptomania further developed Victorian Britain’s fascination with ancient curses, Egyptian mummies, the fourth dimension, and the Book of the Dead.3 It also catalysed a widespread interest in Egyptology that fuelled disputes over the continued ‘exploitation’ of Egyptian heritage by Western archaeologists, contributing to Egyptian nationalism, pharaonism (national pride in Egypt’s history), and Egypt’s domestic film industry.4 Yet reading the phenomenon through the framework of modernism produces a compellingly different narrative of Tutankhamen’s significance. Rather than speaking to imperialism, nationalism, or the politics of Egyptology, this interpretation offers new insight into the relationship between modernity, temporality, and modern enchantment

Revision of the Genus Anoda (Malvaceae)

A revision of the genus Anoda is presented that recognizes 23 species, of which ten are described as new. The genus includes annual herbs, subshrubs, and occasionally shrubs and occurs from the southern United States to Bolivia, Argentina, and Chile. Most of this distributional range, however, is accounted for by a single species, A. cristata, which also occurs as an adventive in a few other parts of the world. The genus is principally Mexican, all of the species occurring within that country. Anoda is closely allied to the genus Periptera, also a Mexican genus, and the two genera share features of fruit structure. The two genera together seem to occupy a relatively isolated position within the family. Anoda is subdivided into six sections, and keys to the sections and to the species are presented

Mixing in Supersonic Turbulence

In many astrophysical environments, mixing of heavy elements occurs in the presence of a supersonic turbulent velocity field. Here we carry out the first systematic numerical study of such passive scalar mixing in isothermal supersonic turbulence. Our simulations show that the ratio of the scalar mixing timescale, $\tau_{\rm c}$, to the flow dynamical time, $\tau_{\rm dyn}$ (defined as the flow driving scale divided by the rms velocity), increases with the Mach number, $M$, for M \lsim3, and becomes essentially constant for M \gsim3. This trend suggests that compressible modes are less efficient in enhancing mixing than solenoidal modes. However, since the majority of kinetic energy is contained in solenoidal modes at all Mach numbers, the overall change in $\tau_{\rm c}/\tau_{\rm dyn}$ is less than 20\% over the range 1 \lsim M \lsim 6. At all Mach numbers, if pollutants are injected at around the flow driving scale, $\tau_{\rm c}$ is close to $\tau_{\rm dyn}.$ This suggests that scalar mixing is driven by a cascade process similar to that of the velocity field. The dependence of $\tau_{\rm c}$ on the length scale at which pollutants are injected into flow is also consistent with this cascade picture. Similar behavior is found for the variance decay timescales for scalars without continuing sources. Extension of the scalar cascade picture to the supersonic regime predicts a relation between the scaling exponents of the velocity and the scalar structure functions, with the scalar structure function becoming flatter as the velocity scaling steepens with Mach number. Our measurements of the volume-weighted velocity and scalar structure functions confirm this relation for M\lsim 2, but show discrepancies at M \gsim 3.Comment: Accepted by Ap

La posición de la especie africana Wissadula rostrata en el género predominantemente neotropical Wissadula

The African species Wissadula rostrata (Schumach. & Thonn.) Pl. ex Hook. has sometimes been recognized in specific rank and sometimes in varietal rank within either W. amplissima (L.) R.E. Fr. or W. hernandioides (L’Hér.) Garcke, both from the Americas. It is here noted that W. rostrata has greater affinity with the South American W. parviflora (A.St.-Hil.) R.E.Fr., and it is concluded that it merits recognition in specific rank.La especie africana Wissadula rostrata (Schumach. & Thonn.) Pl. ex Hook. a veces se recono­ce en rango específico y a veces en rango de variedad adentro de W. amplissima (L.) R.E. Fr. o de W. hernandioides (L’Hér.) Garcke, ambas especies americanas. Aquí se señala que W. rostrata tiene más afinidad con W. parviflora (A.St.-Hil.) R.E.Fr. de Sudamérica, y se concluye que merece reconocimiento en rango específic