Reaction zones in Ti/W composites

1973 ◽  
Vol 8 (2) ◽  
pp. 291-294 ◽  
Author(s):  
J. Kennedy
Keyword(s):  
Reaction Zones

scholarly journals Compatible and Incompatible Interactions in Wheat Involving the Bt-10 Gene for Resistance to Tilletia tritici, the Common Bunt Pathogen

2007 ◽  
Vol 97 (11) ◽  
pp. 1397-1405 ◽  
Author(s):  
Denis A. Gaudet ◽  
Zhen-Xiang Lu ◽  
Frances Leggett ◽  
Bryan Puchalski ◽  
André Laroche
Keyword(s):  
Compatible Interaction ◽  
Incompatible Interaction ◽  
Common Bunt ◽  
Tilletia Tritici ◽  
Pathogen Invasion ◽  
Reaction Zones ◽  
The Common ◽  
Wheat Lines ◽  
Compatible Interactions ◽  
Incompatible Interactions

The infection of wheat lines Neepawa (susceptible), and its sib BW553 that is nearly isogenic for the Bt-10 resistance gene by differentially virulent races T1 and T27 of common bunt (Tilletia tritici), was followed for 21 days following seeding (dfs) using fluorescence and confocal microscopy. Spore germination was nonsynchronous and all spore stages including germination were observed 5 to 21 dfs. Initial host perception of pathogen invasion, based on autofluorescence in epidermal cells adjacent to the appressoria, was similar in both compatible and incompatible interactions, and occurred as early as 5 to 6 dfs. The total number of sites on a 1-cm segment of coleoptile adjacent to the seed that exhibited autofluorescence was similar in both the compatible and incompatible interactions and rose to a maximum of 35 to 40 per 1 cm length of coleoptile following 17 dfs, although new infection events were observed as late as 21 dfs. In the compatible interaction, the autofluorescence became more diffuse 10 to 12 dfs, emanating in all directions in association with fungal spread. In the incompatible interaction, autofluorescence remained restricted to a small area surrounding the penetration site. Two different reaction zones that extended further in tissues surrounding the penetration point in the incompatible interaction compared with the compatible interaction were identified. The accumulation of callose around invading fungal hyphae was observed during both the compatible and incompatible interactions from 8 to 21 dfs. While callose accumulation was more extensive and widespread in the incompatible interaction, it was clearly present in compatible interactions, particularly in treatments involving BW553. These results were confirmed by expression of callose synthase transcripts that were more abundant in BW553 than in Neepawa and were upregulated during pathogen infection in both compatible and incompatible interactions.

Mineralogical controls on the distribution of trace elements in metasomatized peridotite enclaves from Planany, Czech Republic

2007 ◽  
Vol 71 (1) ◽  
pp. 81-91 ◽  
Author(s):  
J. V. Owen ◽  
J. Dostal ◽  
M. Fisera
Keyword(s):  
Trace Elements ◽  
Czech Republic ◽  
Reference Frame ◽  
Outer Layer ◽  
Reaction Zones ◽  
Host Rocks ◽  
Distribution Of Trace Elements

AbstractSmall (m-scale) peridotite enclaves at Planany (central Czech Republic) are separated from their gneissic host rocks by a narrow (cm-scale) reaction rim comprising an inner, tremolite + phlogopite zone and an outer, essentially monomineralic phlogopite zone. Both retain an Mg# very similar to that of the peridotite (Mg# = 81), but relative to this reference frame, show large increases in LILE (K, Rb, Ba) and radionuclides (U, Th). On a smaller scale, however, there has been a mineralogically-controlled decoupling of various components, particularly among the HFSE and REE, the former favouring the phlogopite-rich outer layer of the reaction rim, the latter the amphibole-rich inner zone. Taken together, however, the reaction zones preserve key compositional features of their inferred protolith.

Chemical Reactor Network Application to Emissions Prediction for Industial DLE Gas Turbine

2006 ◽  
Author(s):  
I. V. Novosselov ◽  
P. C. Malte ◽  
S. Yuan ◽  
R. Srinivasan ◽  
J. C. Y. Lee
Keyword(s):  
Gas Turbine ◽  
Chemical Reactor ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Ongoing Research ◽  
Chemical Reactor Network ◽  
Reaction Zones ◽  
Reactor Network

A chemical reactor network (CRN) is developed and applied to a dry low emissions (DLE) industrial gas turbine combustor with the purpose of predicting exhaust emissions. The development of the CRN model is guided by reacting flow computational fluid dynamics (CFD) using the University of Washington (UW) eight-step global mechanism. The network consists of 31 chemical reactor elements representing the different flow and reaction zones of the combustor. The CRN is exercised for full load operating conditions with variable pilot flows ranging from 35% to 200% of the neutral pilot. The NOpilot. The NOx and the CO emissions are predicted using the full GRI 3.0 chemical kinetic mechanism in the CRN. The CRN results closely match the actual engine test rig emissions output. Additional work is ongoing and the results from this ongoing research will be presented in future publications.

scholarly journals Effects of Turbulent Reynolds Number on the Performance of Algebraic Flame Surface Density Models for Large Eddy Simulation in the Thin Reaction Zones Regime: A Direct Numerical Simulation Analysis

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Mohit Katragadda ◽  
Nilanjan Chakraborty ◽  
R. S. Cant
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Fractal Dimension ◽  
Direct Numerical Simulation ◽  
Surface Density ◽  
Flame Surface ◽  
Algebraic Models ◽  
Flame Surface Density ◽  
Turbulent Reynolds Number ◽  
Reaction Zones

A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different turbulent Reynolds numbers has been used to assess the performance of algebraic flame surface density (FSD) models based on a fractal representation of the flame wrinkling factor. The turbulent Reynolds number Rethas been varied by modifying the Karlovitz number Ka and the Damköhler number Da independently of each other in such a way that the flames remain within the thin reaction zones regime. It has been found that the turbulent Reynolds number and the Karlovitz number both have a significant influence on the fractal dimension, which is found to increase with increasing Retand Ka before reaching an asymptotic value for large values of Retand Ka. A parameterisation of the fractal dimension is presented in which the effects of the Reynolds and the Karlovitz numbers are explicitly taken into account. By contrast, the inner cut-off scale normalised by the Zel’dovich flame thicknessηi/δzdoes not exhibit any significant dependence on Retfor the cases considered here. The performance of several algebraic FSD models has been assessed based on various criteria. Most of the algebraic models show a deterioration in performance with increasing the LES filter width.

Solid state reactions between Ni3Al and SiC

1990 ◽  
Vol 5 (9) ◽  
pp. 1985-1994 ◽  
Author(s):  
T. C. Chou ◽  
T. G. Nieh
Keyword(s):  
Growth Rate ◽  
Solid State ◽  
Solid State Reactions ◽  
Growth Rate Constant ◽  
Cross Sectional ◽  
Rate Limiting Step ◽  
Nial Phase ◽  
Reaction Zones ◽  
Carbon Precipitation ◽  
Terminal Component

Solid state reactions between SiC and Ni3Al were studied at 1000°C for different times. Multi-reaction-layers were generated in the interdiffusion zone. Cross-sectional views of the reaction zones show the presence of three distinguishable layers. The Ni3Al terminal component is followed by NiAl, Ni5.4Al1Si2, Ni(5.4−x)Al1Si2 + C layers, and the SiC terminal component. The Ni5.4Al1Si2 layer shows carbon precipitation free, while modulated carbon bands were formed in the Ni(5.4−x)Al1Si2 + C layer. The NiAl layer shows dramatic contrast difference with respect to the Ni3Al and Ni5.4Al1Si2 layers, and is bounded by the Ni3Al/NiAl and Ni5.4Al1Si2/NiAl phase boundaries. The kinetics of the NiAl formation is limited by diffusion, and the growth rate constant is measured to be 2 ⊠ 10−10 cm2/s. The thickness of the reaction zone on the SiC side is always thinner than that on the Ni3Al side and no parabolic growth rate is obeyed, suggesting that the decomposition of the SiC may be a rate limiting step for the SiC/Ni3Al reactions. The carbon precipitates were found to exist in either a disordered or partially ordered (graphitic) state, depending upon their locations from the SiC interface. The formation of NiAl phase is discussed based on an Al-rejection model, as a result of a prior formation of Ni–Al–Si ternary phase. A thermodynamic driving force for the SiC/Ni3Al reactions is suggested.

The effects of high dose rates of ionizing radiations on solutions of iron and cerium salts

1960 ◽  
Vol 255 (1283) ◽  
pp. 490-508 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Dose Rate ◽  
Ferrous Sulphate ◽  
High Dose ◽  
Oh Radicals ◽  
Dose Rates ◽  
Reaction Zones ◽  
Constant Dose ◽  
Ceric Sulphate ◽  
Ionizing Radiations

The electron beam generated by a 15 MeV linear accelerator has been employed to induce reactions in aerated aqueous solutions of 1 to 25 mM ferrous sulphate, and of 0⋅1 to 1 mM ceric sulphate. The radiation was delivered in pulses of 1⋅3 μ s duration and over a range of dose rates from 0⋅5 to 20000 rads/pulse. Radiation yields at constant dose rate were compared with the aid of a chemical dose monitor. A system of two thin, widely spaced, irradiation vessels was employed to determine the variation of yield of any one system over successive known ranges of dose rate. The yield of ferric sulphate in the iron system was found to decrease with increasing dose rate in the range 0⋅01 to 10 krads/pulse by an overall factor of 0⋅85, and was appreciably dependent on the initial concentrations of dissolved oxygen and of ferrous sulphate at high dose rates. Yields of hydrogen and of hydrogen peroxide were practically independent of dose rate. The observations have been interpreted on the basis of inter-radical reactions which occur when the reaction zones of neighbouring clusters overlap. The following reactions can account for all the data: OH + Fe 2+ → Fe 3+ + OH ¯ , (1) H + O 2 → HO 2 , (2) H + OH → H 2 O. (7) The values k 1 / k 7 = 0⋅0062, and k 2 / k 7 = 0⋅22 are reasonably consistent with the observations. In the ceric sulphate system the yield of cerous sulphate increases progressively over the range 0⋅01 to 10 krads/pulse by an overall factor of 1⋅4. The data accord with the view that at high dose rates OH radicals react with them selves ultimately to form hydrogen peroxide, in competition with their normal reaction with cerous sulphate.

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