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Reaction Zone (reaction + zone)
Selected AbstractsIn vitro characterization of Inocutis jamaicensis and experimental inoculation of Eucalyptus globulus standing treesFOREST PATHOLOGY, Issue 5 2009S. Lupo Summary Lesions of variable size, associated with the hymenomycete Inocutis jamaicensis, a white-rot fungus, have been observed on the stems of Eucalyptus globulus trees in Uruguay. The aim of this study was to evaluate some ecophysiological characteristics of I. jamaicensis and assess its ability to colonize E. globulus trees of two different seed origins (Geeveston and Jeeralang) and the clone, 334-1-AR, obtained by micropropagation (ENCE, Spain). The growth of an I. jamaicensis isolate (MVHC11379) was evaluated at 25°C in a medium with a water potential of 0 (, = 0). The growth rate did not vary significantly with a growth medium pH of between 4 and 7. I. jamaicensis showed no growth at either 5 or 37°C at any pH or , tested. Weight loss of heartwood and sapwood of different plant provenances inoculated with I. jamaicensis under laboratory conditions was evaluated, and significant differences observed. Lignin-modifying enzyme activity was evaluated in culture medium with or without E. globulus sawdust as substrate or inducer. Laccase activity was observed with sawdust and manganese peroxidase activity with and without sawdust. Only slight activity of aryl-alcohol oxidase and lignin peroxidase was detected without sawdust. Experimental inoculation with I. jamaicensis of 3-year-old Geeveston and Jeeralang, and of 4-year-old 334-1-AR stems, resulted in successful fungal colonization of 56% of the 334-1-AR, 50% of Geeveston and 25% of Jeeralang trees. Only the heartwood was decayed. In 334-1-AR, the rotted wood was delimited by a reaction zone. Wood characteristics and the ability of I. jamaicensis to overcome the chemical reactions in the tree could partially explain differences in susceptibility to the fungus among provenances observed under natural and laboratory conditions. [source] ,Defence lignin' and hydroxycinnamyl alcohol dehydrogenase activities in wounded Eucalyptus gunniiFOREST PATHOLOGY, Issue 2 2003S. Hawkins Summary To learn more about lignin formation in response to wounding in trees, we adopted two complementary approaches: (1) microscopic and histochemical studies of the wound response in 3.5-month-old Eucalyptus gunnii plantlets and (2) biochemical investigations of hydroxycinnamyl alcohol dehydrogenase activities in wounded 6-year-old, field-grown E. gunnii trees. The first approach revealed that a barrier zone was formed in response to wounding in both ground tissues (cortex barrier and pith reaction zone) and vascular tissues. The barrier zone was barely detectable after 24 h but well-developed 7 days after wounding. Microscopic analyses indicated that the barrier zone was formed by the reinforcement of cell walls with ,lignin-like material' in both ground tissues and vascular tissue, and that, in addition, the lumen of certain xylem cells (vessels and fibres) were blocked by the deposition of polymeric phenolic material. Histochemical characterization revealed that the lignin-like material (,defence lignin') deposited in ground tissue cell walls and xylem cell blockages was poor in syringyl (S-type) lignin units and therefore differed from the usual mixed guaiacyl,syringyl (G,S) lignin unit composition of E. gunnii developmental lignin. In contrast, S-type lignin appeared to be deposited in the cell walls of immature developing secondary xylem cells at a stage when the cell walls of comparable cells from unwounded control stems contained lignin poor in syringyl units. The second approach indicated that two different types of cinnamyl alcohol dehydrogenase activity are induced, and apparently regulated differentially, in response to wounding in E. gunnii trees. Coniferyl alcohol dehydrogenase activity was induced immediately and continued to increase throughout the first 15 days of the 17-day experimental period, while sinapyl alcohol dehydrogenase activity was first detected at 8 days after wounding and continued to increase throughout the experimental period. The biological roles of the two alcohol dehydrogenase activities are discussed in relation to the formation of defence lignin versus developmental lignin in trees. Résumé Afin d'approfondir nos connaissances concernant la formation de lignine en réponse aux blessures chez les arbres, nous avons utilisé deux approches complémentaires: (1) des études microscopiques et histochimiques de la réponse à la blessure chez les plantules d'Eucalyptus gunniiâgées de 3 mois et demi, et (2) des analyses biochimiques des activités alcools hydroxycinnamyliques déshydrogénases chez les arbres âgés de 6 ans blessés au champ. L'utilization de la première approche a révélé qu'une barrière physique se forme en réponse à la blessure aux niveaux des tissus vasculaires, de la moelle, et des tissus externes au phloème. A 24 h après la blessure, cette barrière est peu développée mais elle est bien formée après 7 jours. Les analyses microscopiques et histochimiques ont indiqué que les parois cellulaires au niveau de la barrière sont renforcées par un composé semblable à la lignine (,lignin-like material'). De plus, les lumens de plusieurs cellules xylémiennes (vaisseaux et fibres) sont bouchées par le dépôt d'un composé polymérique de nature phénolique. Les caractérizations histochimiques ont indiqué que le ,lignin-like material' (lignine de défense) déposé dans les parois cellulaires de la moelle et des tissus externes au phloème, et dans les lumens des cellules xylemiennes, contient peu d'unités syringyles (type-S). En conséquence, cette ,lignine de défense' se distingue de la ,lignine de développement' typique d'E. gunnii, qui est composée d'unités guaiacyles (type-G) et d'unités syringyles (type-S). En revanche chez les plantules blessées, des unités syringyles sont déposées dans les parois des cellules immatures du xylème à un stade où les cellules comparables des plantules témoins ne contiennent que très peu d'unités syringyles. La deuxième approche a indiqué que deux activités alcools cinnamyliques déshydrogénases différentes sont induites, et régulées d'une façon différencielle, en réponse à la blessure chez les arbres d'E. gunnii. L'activité alcool coniférylique déshydrogénase est induite rapidement et continue d'augmenter pendant les 15 premiers jours de la période expérimentale de 17 jours, tandis que l'activité alcool sinapylique déshydrogénase est seulement détectée à 8 jours après la blessure et continue d'augmenter le long de la période expérimentale. Les rôles biologiques potentiels de ces deux activités alcools déshydrogénases sont discutés en relation avec la formation de la lignine de défense et avec la lignine de développement chez les arbres. Zusammenfassung Zur Untersuchung der Ligninbildung nach Verletzungen bei Bäumen wurden zwei sich ergänzende Forschungsansätze gewählt: 1. Mikroskopische und histochemische Untersuchungen der Wundreaktion an Jungpflanzen (3,5 Monate alt) von Eucalyptus gunnii und 2. Biochemische Untersuchungen der Hydroxycinnamylalkohol-Dehydrogenase-Aktivität bei verletzten, sechs Jahre alten E. gunnii -Bäumen im Freiland. Der erste Ansatz zeigte, dass eine Barrierezone als Antwort auf die Verletzung sowohl in beiden Grundgeweben (Cortex-Barriere und Reaktionszone im Mark) als auch in den Leitgeweben gebildet wird. Die Barrierezone war 24 Stunden nach der Verletzung gerade erkennbar, nach sieben Tagen war sie gut entwickelt. Die mikroskopische Untersuchung zeigte, dass die Barrierezone durch Verstärkung der Zellwände mit ,,ligninartigem Material,, im Grund- und Leitgewebe gebildet wurde, und dass zusätzlich das Lumen gewisser Xylemzellen (Gefässe und Fasern) durch Ablagerung von polymerem phenolischem Material verschlossen wurde. Die histochemische Analyse ergab, dass das ligninartige Material (,,Abwehrlignin,,), das in den Zellwänden des Grundgewebes und in den Lumina der Xylemzellen abgelagert wurde, geringe Mengen an Syringyl-(S-Typ)-Lignineinheiten enthielt und sich somit von der normalen Guaiacyl-Syringyl(G-S)-Komposition des Lignins von E. gunnii unterschied. Das S-Typ-Lignin wurde offenbar in den Zellwänden sich entwickelnder sekundärer Xylemzellen abgelagert. Diese Einlagerung erfolgte in einem Stadium, in dem die Zellwände der vergleichbaren Zellen in unverletzten Kontrollstämmen Lignin mit geringem Syringylgehalt enthielten. Der zweite Versuchsansatz zeigte, dass als Reaktion auf die Verletzung zwei verschiedene Arten von Cinnamylalkohol-Dehydrogenase-Aktivitäten induziert und offensichtlich unterschiedlich reguliert werden. Die Aktivität der Coniferyl-Alkohol-Dehydrogenase wurde sofort induziert und sie nahm während 15 Tagen der 17tägigen Versuchsperiode stetig zu, während die Aktivität der Sinapyl-Dehydrogenase erstmals 8 Tage nach der Verletzung nachweisbar war und dann während der gesamten Versuchsperiode anstieg. Die biologische Bedeutung der beiden Alkoholdehydrogenase-Aktivitäten werden in Bezug auf die Bildung von Abwehr-Lignin im Vergleich zur normalen Ligninbildung in Bäumen diskutiert. [source] Prediction of the non-ideal detonation performance of commercial explosives using the DeNE and JWL++ codesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2005S. Esen Abstract The non-ideal detonation performance of two commercial explosives is determined using the DeNE and JWL++ codes. These two codes differ in that DeNE is based on a pseudo-one-dimensional theory which is valid on the central stream-tube and capable of predicting the non-ideal detonation characteristics of commercial explosives as a function of the explosive type, rock properties and blasthole diameter. On the other hand, JWL++ is a hydrocode running in a 2-D arbitrary Lagrangian,Eulerian code with CALE-like properties and can determine the flow properties in all stream lines within the reaction zone. The key flow properties (detonation velocity, pressure, specific volume, extent of reaction and reaction zone length) at the sonic locus on the charge axis have been compared. In general, it is shown that the flow parameters determined using both codes agree well. The pressure contours determined using the JWL++ are analysed in detail for two explosives at 165 mm blastholes confined in limestone and kimberlite with a view to further investigate the explosive/rock interface. The DeNE and JWL++ codes have been validated using the measured in-hole detonation velocity data. Copyright © 2005 John Wiley & Sons, Ltd. [source] Numerical studies on the reaction of carbon particles in a vacuum residue,air flameINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2006Ho Young Park Abstract A computational work was carried out for the study of one-dimensional, laminar, premixed, flat, atomized vacuum residue (VR) particle,air flames. The mathematical model includes the specified pyrolysis scheme, soot and char oxidation scheme. With some experimental works, the product composition and kinetic parameters of VR pyrolysis were determined and used for the present computational work. The computed results show that the oxidation of VR carbon char and soot occurs mainly in the reaction zone and the oxidation rate of soot is much higher than that of VR carbon char. The oxidation rates of carbon char and soot can be increased with the decrease in particle diameter, and it might be accomplished by the more effective atomization and mixing of solid particles with combustion air. Copyright © 2005 John Wiley & Sons, Ltd. [source] NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/ArINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2002Jeong Park Abstract Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. [source] Pressureless Sintering of 3Y-TZP/Stainless-Steel Composite LayersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008Mahdi Dourandish A pressureless sintering method was utilized to fabricate metal/ceramic joints out of yttria-stabilized zirconia (3Y-TZP) and stainless steels (SS). Ultrafine (150 nm) and nanoscale (75 nm) 3Y-TZP particles and micrometric 17-4PH, 316L, and 420 SS (<31 ,m) powders were tested. Isothermal and nonisothermal sintering behaviors of the powders and composite layers in hydrogen, argon, and vacuum atmospheres were examined. It was found that the mismatch strain between the zirconia ceramic and SS during cosintering is significant, which leads to bond cracking and joint failure. Nevertheless, interlayer diffusion of Zr, Fe, and Cr and the formation of a reaction zone, particularly during vacuum sintering, enables an accommodation of the residual stresses caused by the mismatch shrinkage upon cooling. The formation of a porous region close to the metal layer was observed. Sinter joining of zirconia to 420 SS is more successful compared with austenitic steel because of a lower difference in the coefficient of thermal expansion. [source] The effect of mixing on the generation of alkaline peroxymonosulfateTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2001Mohammad Shaharuzzaman Abstract Alkaline peroxymonosulfate (PMS) has been successfully used in the laboratory for bleaching kraft pulp. Used in conjunction with oxygen, the addition of 1.0% PMS to an oxygen delignification system can increase delignification from 49% to 73% without reducing pulp strength. One promising method of achieving this is the catalytic oxidation of sodium sulfite with oxygen. Laboratory generation of PMS is readily achieved, but typically at low yields and low concentrations. Here we investigate the mixing-sensitivity of its generation under semi-batch reaction conditions using a number of laboratory mixers. Our primary focus was on the energy dissipation in the reaction zone and its effect on PMS yield and concentration. By managing the chemical contacting strategy and increasing energy dissipation in the reaction zone we were able to generate PMS at higher yields and concentrations than previously reported. On a utilisé avec succès le péroxymonosulfate alcalin (PMS) au laboratoire pour effectuer le blanchiment d'une p,te kraft. En association avec de l'oxygène, l'ajout de 1,0% de PMS à un système de délignification à l'oxygène peut accro,tre la délignification de 49% à 73% sans réquire la résistance de la p,te. Une méthode prometteuse pour y parvenir réside dans l'oxydation catalytique du sulfite de sodium avec l'oxygène. La production de PMS en laboratoire est facile à réaliser, mais typiquement avec un rendement faible et à basse concentration. On étudie ici la sensibilité au mélange de sa production dans des conditions de réaction semi-continues à l'aide de plusieurs mélangeurs de laboratoire. On s'intéresse principalement à la dissipation d'énergie dans la zone de réaction et à ses effets sur le rendement et la concentration du PMS. En gérant la stratégie de fonctionnement par contact chimique et en augmentant la dissipation d'énergie dans la zone de réaction, on a pu produire du PMS à des rendements et concentrations supérieurs à ceux présentés antérieurement. [source] Solar membrane natural gas steam-reforming process: evaluation of reactor performanceASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010M. De Falco Abstract In this work, the performance of an innovative plant for efficient hydrogen production using solar energy for the process heat duty requirements has been evaluated via a detailed 2D model. The steam-reforming reactor consists of a bundle of coaxial double tubes assembled in a shell. The annular section of each tube is the reaction zone in which Ni-based catalyst pellets are packed, whereas the inner tube is a dense Pd-based selective membrane that is able to remove hydrogen from the reaction zone. By coupling reaction and hydrogen separation, equilibrium constrains inside the reactor are circumvented and high methane conversions at relatively low temperatures are achieved. The heat needed for the steam-reforming reaction at this low operating temperature can be supplied by using a molten salt stream, heated up to 550 °C by a parabolic mirror solar plant, as heating fluid. The effects on membrane reactor performance of some operating conditions, as gas mixture residence time, reaction pressure and steam-to-carbon ratio, are assessed together with the enhancement of methane conversion with respect to the traditional process, evaluated in the range 40.5,130.9% at the same operating conditions. Moreover, owing to the use of a solar source for chemical process heat duty requirements, the greenhouse gases (GHG) reduction is estimated to be in the range 33,67%. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Cretaceous high- P granulites at Milford Sound, New Zealand: metamorphic history and emplacement in a convergent margin settingJOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2000G. L. Clarke Granulite facies orthogneiss of the Arthur River Complex (ARC) at Milford Sound, western Fiordland records a complex Early Cretaceous magmatic and orogenic history for the Pacific Gondwana margin that culminated in the emplacement and burial of a dioritic batholith, the Western Fiordland Orthogneiss (WFO). Enstatite-bearing mafic to intermediate protoliths of the ARC and WFO intruded the middle to upper crust. The early deformation history of the ARC is preserved in the Pembroke Granulite, where two-pyroxene S1 assemblages that reflect P<8 kbar and T >750 °C were only patchily recrystallized during later deformation. S1 is cut by garnet-bearing, leucogabbroic to dioritic veins, which are cut by distinctive D2 fractures involving anorthositic veins and garnet,diopside,plagioclase-bearing reaction zones. These zones are widespread in the ARC and WFO and record conditions of P,14 kbar and T >750 °C. Garnet,clinopyroxene-bearing corona reaction textures that mantle enstatite in both the ARC and WFO reflect Early Cretaceous burial by approximately 25 km of continental crust. Most of the ARC is formed from the Milford and Harrison Gneisses, which contain steeply dipping S4 assemblages that envelop the Pembroke Granulite and involve garnet, hornblende, diopside, clinozoisite, rutile and plagioclase, with or without kyanite. The P,T history of rocks in western Fiordland reflects pronounced Early Cretaceous convergence-related tectonism and burial, possibly related to the collision and accretion of island arc material onto the Pacific Gondwana margin. [source] Methane steam reforming at microscales: Operation strategies for variable power output at millisecond contact timesAICHE JOURNAL, Issue 1 2009Georgios D. Stefanidis Abstract The potential of methane steam reforming at microscale is theoretically explored. To this end, a multifunctional catalytic plate microreactor, comprising of a propane combustion channel and a methane steam reforming channel, separated by a solid wall, is simulated with a pseudo 2-D (two-dimensional) reactor model. Newly developed lumped kinetic rate expressions for both processes, obtained from a posteriori reduction of detailed microkinetic models, are used. It is shown that the steam reforming at millisecond contact times is feasible at microscale, and in agreement with a recent experimental report. Furthermore, the attainable operating regions delimited from the materials stability limit, the breakthrough limit, and the maximum power output limit are mapped out. A simple operation strategy is presented for obtaining variable power output along the breakthrough line (a nearly iso-flow rate ratio line), while ensuring good overlap of reaction zones, and provide guidelines for reactor sizing. Finally, it is shown that the choice of the wall material depends on the targeted operating regime. Low-conductivity materials increase the methane conversion and power output at the expense of higher wall temperatures and steeper temperature gradients along the wall. For operation close to the breakthrough limit, intermediate conductivity materials, such as stainless steel, offer a good compromise between methane conversion and wall temperature. Even without recuperative heat exchange, the thermal efficiency of the multifunctional device and the reformer approaches ,65% and ,85%, respectively. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Shortcut method for kinetically controlled reactive distillation systemsAICHE JOURNAL, Issue 6 2003J. W. Lee A geometric-based shortcut method for reactive distillation is addressed. The rectification body method for nonreactive distillation, the concept of critical Damköhler numbers, and the geometric design method for reactive distillation are combined with a new eigenvector analysis of pinch points. This shortcut method provides a minimum or reasonable Damköhler number for a given heat duty, as well as the design implication of how to effectively distribute reaction zones inside a column. This method can be used for a fast screening of process design alternatives and for an initialization of rigorous optimization. [source] Graphical design applied to MTBE and methyl acetate reactive distillation processesAICHE JOURNAL, Issue 6 2001Jae W. Lee Graphical tray-by-tray methods for reactive distillation columns we developed previously are extended to study two industrial processes: MTBE production and methyl acetate production. As both processes involve four components, projection was used to obtain ternary diagrams by ignoring the inert (n-butane) for MTBE production and by projecting onto planes of constant acetic acid concentrations for methyl acetate production. These projected methods clearly explain the placing that industry uses for the reaction zones in these processes. Further, it can be visualized why there is an optimum reflux ratio for the methyl acetate process and a value can be quantitatively predicted for it that lies within the range the literature reports. [source] Persistence of the gelatinous layer within altered tension-wood fibres of beech degraded by Ustulina deustaNEW PHYTOLOGIST, Issue 2 2000S. BAUM The gelatinous layer (G-layer) of tension-wood fibres in reaction wood of beech showed alterations as a result of the physiological processes involved in the conversion of sapwood into false heartwood or reaction-zone tissue. Using transmitted-light, fluorescence and UV microscopy, polyphenolic compounds were found to infiltrate and encrust the cellulose microfibrils within the G-layer. Experiments with naturally infected and artificially inoculated wood showed that these processes affect the rate and mode of degradation by wood-decaying fungi. Thus, although the ascomycete Ustulina deusta was able to degrade the G-layer from within the lumina of tension-wood fibres in unaltered sapwood, it failed to do so for a prolonged period within false heartwood and reaction zones. In both situations, however, there was some degradation of the underlying secondary wall in the form of erosion troughs which can be attributed to soft rot ,type II', and internal cavity formation typical for ,type I' attack. The present study indicates that not only cell type, but also alterations in the cell wall structure, affect the activity and degradation mode of decay fungi in beech. [source] Painting and Printing Living Bacteria: Engineering Nanoporous Biocatalytic Coatings to Preserve Microbial Viability and Intensify ReactivityBIOTECHNOLOGY PROGRESS, Issue 1 2007Michael C. Flickinger Latex biocatalytic coatings containing ,50% by volume of microorganisms stabilize, concentrate and preserve cell viability on surfaces at ambient temperature. Coatings can be formed on a variety of surfaces, delaminated to generate stand-alone membranes or formulated as reactive inks for piezoelectric deposition of viable microbes. As the latex emulsion dries, cell preservation by partial desiccation occurs simultaneously with the formation of pores and adhesion to the substrate. The result is living cells permanently entrapped, surrounded by nanopores generated by partially coalesced polymer particles. Nanoporosity is essential for preserving microbial viability and coating reactivity. Cryo-SEM methods have been developed to visualize hydrated coating microstructure, confocal microscopy and dispersible coating methods have been developed to quantify the activity of the entrapped cells, and FTIR methods are being developed to determine the structure of vitrified biomolecules within and surrounding the cells in dry coatings. Coating microstructure, stability and reactivity are investigated using small patch or strip coatings where bacteria are concentrated 102 - to 103 -fold in 5,75 ,m thick layers with pores formed by carbohydrate porogens. The carbohydrate porogens also function as osmoprotectants and are postulated to preserve microbial viability by formation of glasses inside the microbes during coat drying; however, the molecular mechanism of cell preservation by latex coatings is not known. Emerging applications include coatings for multistep oxidations, photoreactive coatings, stabilization of hyperthermophiles, environmental biosensors, microbial fuel cells, as reaction zones in microfluidic devices, or as very high intensity (>100 g·L -1 coating volume·h -1) industrial or environmental biocatalysts. We anticipate expanded use of nanoporous adhesive coatings for prokaryotic and eukaryotic cell preservation at ambient temperature and the design of highly reactive "living" paints and inks. [source] | ||||||||||||||||