Relevant bibliographies by topics / Catalytic cycles

Academic literature on the topic 'Catalytic cycles'

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Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Catalytic cycles"

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Zeravcic, Zorana, and Michael P. Brenner. "Spontaneous emergence of catalytic cycles with colloidal spheres." Proceedings of the National Academy of Sciences 114, no. 17 (April 10, 2017): 4342–47. http://dx.doi.org/10.1073/pnas.1611959114.

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Colloidal particles endowed with specific time-dependent interactions are a promising route for realizing artificial materials that have the properties of living ones. Previous work has demonstrated how this system can give rise to self-replication. Here, we introduce the process of colloidal catalysis, in which clusters of particles catalyze the creation of other clusters through templating reactions. Surprisingly, we find that simple templating rules generically lead to the production of huge numbers of clusters. The templating reactions among this sea of clusters give rise to an exponentially growing catalytic cycle, a specific realization of Dyson’s notion of an exponentially growing metabolism. We demonstrate this behavior with a fixed set of interactions between particles chosen to allow a catalysis of a specific six-particle cluster from a specific seven-particle cluster, yet giving rise to the catalytic production of a sea of clusters of sizes between 2 and 11 particles. The fact that an exponentially growing cycle emerges naturally from such a simple scheme demonstrates that the emergence of exponentially growing metabolisms could be simpler than previously imagined.
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Varfolomeev, Sergei D., Igor A. Gariev, and Igor' V. Uporov. "Catalytic sites of hydrolases: structures and catalytic cycles." Russian Chemical Reviews 74, no. 1 (January 31, 2005): 61–76. http://dx.doi.org/10.1070/rc2005v074n01abeh001159.

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Boudart, M. "Adsorption assisted desorption in catalytic cycles." Journal of Molecular Catalysis A: Chemical 141, no. 1-3 (May 6, 1999): 1–7. http://dx.doi.org/10.1016/s1381-1169(98)00244-1.

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Kozuch, Sebastian, and Jan M. L. Martin. "“Turning Over” Definitions in Catalytic Cycles." ACS Catalysis 2, no. 12 (November 20, 2012): 2787–94. http://dx.doi.org/10.1021/cs3005264.

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Uhe, Andreas, Sebastian Kozuch, and Sason Shaik. "Automatic analysis of computed catalytic cycles." Journal of Computational Chemistry 32, no. 5 (November 12, 2010): 978–85. http://dx.doi.org/10.1002/jcc.21669.

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Sinibaldi, Arianna, Valeria Nori, Andrea Baschieri, Francesco Fini, Antonio Arcadi, and Armando Carlone. "Organocatalysis and Beyond: Activating Reactions with Two Catalytic Species." Catalysts 9, no. 11 (November 6, 2019): 928. http://dx.doi.org/10.3390/catal9110928.

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Since the beginning of the millennium, organocatalysis has been gaining a predominant role in asymmetric synthesis and it is, nowadays, a foundation of catalysis. Synergistic catalysis, combining two or more different catalytic cycles acting in concert, exploits the vast knowledge acquired in organocatalysis and other fields to perform reactions that would be otherwise impossible. Merging organocatalysis with photo-, metallo- and organocatalysis itself, researchers have ingeniously devised a range of activations. This feature review, focusing on selected synergistic catalytic approaches, aims to provide a flavor of the creativity and innovation in the area, showing ground-breaking examples of organocatalysts, such as proline derivatives, hydrogen bond-mediated, Cinchona alkaloids or phosphoric acids catalysts, which work cooperatively with different catalytic partners.
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Grishchenko, Liudmyla, Natalia S. Novychenko, Igor Matushko, Alexander N. Zaderko, Galyna G. Tsapyuk, Oleksandr V. Mischanchuk, Vitaliy E. Diyuk, and Vladyslav V. Lisnyak. "Catalytic efficiency of activated carbon functionalized with phosphorus-containing groups in 2-propanol dehydration." French-Ukrainian Journal of Chemistry 7, no. 1 (2019): 46–56. http://dx.doi.org/10.17721/fujcv7i1p46-56.

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The functionalization of activated carbon (AC) by P-containing groups was conducted, and their thermal desorption was studied. Depending on the used method, the functionalized AC contains 0.5–1.45 mmol/g of acidic groups acting in catalytic 2-propanol dehydration. All catalysts showed 100% conversion of 2-propanol to propylene. The catalytic activity does not change with time under isothermal conditions and during their repeated use in catalysis, for 3 cycles of heating-cooling. In fact, the yield of propylene remains stable; it does not decrease with each cycle. Preliminary oxidation with nitric acid causes a small increase in the catalytic activity.
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Kim, Byungjun, Yongjae Kim, and Sarah Yunmi Lee. "Stereoselective Michael Additions of Arylacetic Acid Derivatives by Asymmetric Organocatalysis." Synlett 33, no. 07 (January 5, 2022): 609–16. http://dx.doi.org/10.1055/s-0041-1737323.

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AbstractBecause of the versatility of chiral 1,5-dicarbonyl structural motifs, the development of stereoselective Michael additions of arylacetic acid derivatives to electron-deficient alkenes is an important challenge. Over recent decades, an array of enantio- and diastereoselective methods of this type have been developed through the use of chiral organocatalysts. In this article, three distinct strategies in this research area are highlighted. Catalytic generation of either a chiral iminium electrophile (iminium catalysis) or a chiral enolate nucleophile (Lewis­ base catalysis) has allowed the efficient construction of stereogenic C–C bonds. We also introduce a synergistic catalytic approach involving the merger of these two catalytic cycles that provides selective access to all four stereoisomers of products with vicinal stereocenters.1 Introduction2 Iminium Catalysis3 Lewis Base Catalysis4 Synergistic Organocatalysis5 Summary
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Hunt, Patricia A. "Organolanthanide mediated catalytic cycles: a computational perspective." Dalton Transactions, no. 18 (2007): 1743. http://dx.doi.org/10.1039/b700876g.

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Al-Shawi, Marwan K. "Catalytic and transport cycles of ABC exporters." Essays in Biochemistry 50 (September 7, 2011): 63–83. http://dx.doi.org/10.1042/bse0500063.

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ABC (ATP-binding cassette) transporters are arguably the most important family of ATP-driven transporters in biology. Despite considerable effort and advances in determining the structures and physiology of these transporters, their fundamental molecular mechanisms remain elusive and highly controversial. How does ATP hydrolysis by ABC transporters drive their transport function? Part of the problem in answering this question appears to be a perceived need to formulate a universal mechanism. Although it has been generally hoped and assumed that the whole superfamily of ABC transporters would exhibit similar conserved mechanisms, this is proving not to be the case. Structural considerations alone suggest that there are three overall types of coupling mechanisms related to ABC exporters, small ABC importers and large ABC importers. Biochemical and biophysical characterization leads us to the conclusion that, even within these three classes, the catalytic and transport mechanisms are not fully conserved, but continue to evolve. ABC transporters also exhibit unusual characteristics not observed in other primary transporters, such as uncoupled basal ATPase activity, that severely complicate mechanistic studies by established methods. In this chapter, I review these issues as related to ABC exporters in particular. A consensus view has emerged that ABC exporters follow alternating-access switch transport mechanisms. However, some biochemical data suggest that alternating catalytic site transport mechanisms are more appropriate for fully symmetrical ABC exporters. Heterodimeric and asymmetrical ABC exporters appear to conform to simple alternating-access-type mechanisms.
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Dissertations / Theses on the topic "Catalytic cycles"

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Ceylan, Yavuz Selim. "Exploration of Transition Metal-Containing Catalytic Cycles via Computational Methods." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505287/.

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Styrene production by a (FlDAB)PdII(TFA)(η2-C2H4) complex was modeled using density functional theory (DFT). Benzene C-H activation by this complex was studied via five mechanisms: oxidative addition/reductive elimination, sigma-bond metathesis, concerted metalation deprotonation (CMD), CMD activation of ethylene, and benzene substitution of ethylene followed by CMD of the ligated benzene. Calculations provided evidence that conversion of benzene and ethylene to styrene was initiated by the fifth pathway, arylation via CMD of coordinated benzene, followed by ethylene insertion into the Ru-Ph bond, and then β-hydrogen elimination. Also, monomer (active species)/dimer equilibrium concentrations were analyzed. The results obtained from present study were compared with that of a recently reported RhI complex to help identify more suitable catalysts for the direct production of styrene from ethylene and benzene. Second, theoretical studies of heterobimetallic {Ag–Fe(CO)5}+ fragments were performed in conjunction with experiments. The computational models suggested that for this first example of a heterodinuclear, metal-only FeAg Lewis pair (MOLP) that Fe(CO)5 acts as a Lewis base and AgI as a Lewis acid. The ῡCO bands of the studied molecules showed a blue shift relative to those measured for free Fe(CO)5, which indicated a reduction in Fe→CO backbonding upon coordination to silver(I). Electrostatic interaction is predicted via DFT as the dominant mode of Fe—Ag bonding augmented by a modest amount of charge transfer between Ag+ and Fe(CO)5. Third, computational analyses of hypothetical transition metal-terminal boride [MB(PNPR)] complexes were reported. DFT, natural orbital analysis (NBO), and multiconfiguration self-consistent field (MCSCF) calculations were employed to investigate the structure and bonding of terminal boride complexes, in particular the extent of metal dπ - boron pπ bonding. Comparison of metal-boride, -borylene and –boryl bond lengths confirms the presence of metal-boron π bonds, albeit the modest shortening (~ 3%) of the metal-boron bond suggests that the π-bonding is weak. Their instabilities, as measured by free energies of H2 addition to make the corresponding boryl complexes, indicate terminal boride complexes to be thermodynamically weak. It is concluded that for the boride complexes studied, covering a range of 4d and 5d metals, that the metal-boride bond consisted of a reasonably covalent σ and two very polarized π metal-boron bonds. High polarization of the boron to metal π-bonds indicated that a terminal boride is an acceptor or Z type ligand. Finally, anti-Markovnikov addition of water to olefins has been a long-standing goal in catalysis. The [Rh(COD)(DPEphos)]+ complex was found as a general and regioselective group 9 catalyst for intermolecular hydroamination of alkenes. The reaction mechanism was adapted for intermolecular hydration of alkenes catalyzed by a [Rh(DPEphos)]+ catalyst and studied by DFT calculations. Olefin hydration pathways were analyzed for anti-Markovnikov and Markovnikov regioselectivity. On the basis of the DFT results, the operating mechanism can be summarized as follows: styrene activation through nucleophilic attack by OHδ− of water to alkene with simultaneous Hδ+ transfer to the Rh; this is then followed by formation of primary alcohol via reductive elimination. The competitive formation of phenylethane was studied via a β-elimination pathway followed by hydrogenation. The origin of the regioselectivity (Markovnikov vs anti-Markovnikov) was analyzed by means of studying the molecular orbitals, plus natural atomic charges, and shown to be primarily orbital-driven rather than charge-driven.
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Bhawal, Benjamin Niladri. "Discovery and development of catalytic syntheses of aza-cycles." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708586.

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Shammas, Camille N. Y. A. "An investigation of the catalytic cycles of two dehydrogenases by X ray crystallography." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274756.

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Stirling, Matthew John. "Coupled catalytic cycles : development of a procedure for the dynamic kinetic resolution of amines." Thesis, University of Huddersfield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438067.

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Enantiomerically pure chiral amines are particularly important to the pharmaceutical and agrochemical industries. Due to the procedural operational simplicity the most common method for their synthesis on an industrial scale is kinetic resolution. However, this methodology has the inherent disadvantage of limiting the yield to a maximum of 50%. To overcome this drawback it is possible to combine the kinetic resolution with a simultaneous racemisation to give a theoretical yield of 100% in a procedure known as dynamic kinetic resolution. The most suitable method for amine resolution is via enzymatic acylation, however most known methods for amine racemisation require harsh conditions under which enzymes would be denatured. To date only three methods for amine dynamic kinetic resolution have been reported, all of which are not industrially viable. Herein we report the development of an amine dynamic kinetic resolution system using a novel iridium-based amine racemisation catalyst. Our initial attempts to utilise CATHyTM catalysts for amine racemisation proved unsuccessful, it did however reveal an unexpected property of the iridiumcatalysed CATHyTM of 6,7-dimethoxy- I -methyl-3,4-dihydroisoquinoline. During the asymmetric reduction of this substrate the enantiomeric excess of the product was observed to decrease with time. Initially this was suspected to be due to an in-situ racemisation, however our investigation disproved this and lead to the proposed system in which two catalytic species are present, one of which is (S)-selective and the other (R)-selective. During this investigation it was discovered that the iridium catalyst, pentamethylcyclopentadienyliridium (III) chloride dimer could be used as an amine racemisation catalyst. Further work found that the in-situ generation of the analogous iodo catalyst, pentamethylcyclopentadienyliridium (III) iodide dimer, led to a racemisation catalyst that was several orders of magnitude more active than the chloride species and more active than any previously reported amine racemisation catalyst. This iridium iodide catalyst was then synthesised and isolated and a standard amine racemisation protocol developed, which was utilised in the racemisation of a range of secondary amines and a tertiary amine. The catalyst also exhibited some activity towards the racemisation of amino acid esters. The attempted racemisation of primary amines led to the formation of dimeric impurities due to the reaction of the imine intermediate with the amine starting material. The catalyst was also shown to be able to racemise alcohols in the presence of a base, although the rate of hydrogen loss from the catalyst exceeded the rate of ketone hydrogenation and the reaction led to a quantitative conversion to ketone. The amine racemisation system using the pentamethylcyclopentadienyliridium (III) iodide dimer catalyst was then combined with an enzymatic resolution resulting in the dynamic kinetic resolution of 6,7-dimethoxy-l-methyl-1,2,3,4- tetrahydroisoquinoline in which the (R)-carbamate was isolated in 82% yield with 96% ee. This result constitutes the first example of a chemo-enzymatic dynamic kinetic resolution on a secondary amine using an organometallic amine racemisation catalyst.
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Parker, Mariah L. "The Investigation of Oxidative Addition Reactions of Metal Complexes in Cross-Coupling Catalytic Cycles Based on a Unique Methodology of Coupled Ion/Ion-Ion/Molecule Reactions." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5651.

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Popular catalytic cycles, such as the Heck, Suzuki, and Negishi, utilize metal centers that oscillate between two oxidation states (II/0) during the three main steps of catalysis: reductive elimination, oxidative addition, and transmetallation. There has been a push to use less toxic, cheaper metal centers in catalytic cycles, leading to interest in first-row transition metals, such as nickel and cobalt. With these metals, the cycles can potentially pass through the +1 oxidation state, which acts as reactive intermediates, undergoing oxidative additions to form products, potentially with radical characteristics. The oxidative addition steps of catalytic cycles are critical to determining overall rates and products, however in many cases, these steps have not been amenable to study, in either condensed phase or gas phase, in the past. Through the use of electron transfer dissociation (ETD) technology on a modified Thermo Electron LTQ XLTM mass spectrometer, it is possible to generate intermediates in these catalytic cycles, including those in unusual oxidation states. Using sequentially coupled ion/ion-ion/molecule reactions, the reduced, reactive intermediate can be readily generated, isolated, and studied.As a model set of reactions, the mono- and bis-phenanthroline complexes of Fe(I), Co(I), Ni(I), Cu(I), and Zn(I) were formed by reduction of the corresponding M(II) species in an ion/ion reaction with the fluoranthenyl radical anion. The chemistry of the M(I) species was probed in ion/molecule reactions with allyl iodide. In order to explore ligand effects and the scope of oxidative addition reagents further, bipyridine and terpyridine were studied with these five first-row transition metal complexes while using an acetate series and other substrates for oxidative additions. Through these studies, the roles of the metal and ligand in dictating the product distributions and reaction rates were assessed. Metal electron count, ligand flexibility, and coordination number are critical factors. The overall reactivity is in accord with density functional theory calculations and mirrors that of proposed intermediates in condensed-phase catalytic cycles. In addition, second- and third-row transition metals (Ru(I), Pd(I), and Pt(I)) were explored with bipyridine, mono- and bis-triphenylphosphine, and 1,2-bis(diphenylphosphino)benzene ligation schemes. A variety of oxidative addition reagents were surveyed to determine the scope of reactivity and preference toward metal-carbon bond formation or carbon radical formation.
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Sullivan, Ryan. "Improving Efficiency by Using Continuous Flow to Enable Cycles: Pseudo-Catalysis, Catalysis and Kinetics." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40387.

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This thesis is centered around the use of flow chemistry to enable cycles in order to increase reaction or process efficiency. Chapter two describes the development of a pseudo-catalytic cycle in space; a strategy to achieve formal sub-stoichiometric loading of a chiral auxiliary. By telescoping auxiliary attachment, asymmetric transformation and auxiliary cleavage into one continuous flow process, coupled with separation of product and recovery of auxiliary, the reuse of the auxiliary can be automated by returning the recovered auxiliary back to the start of the process to achieve ‘turn-over.’ An asymmetric hydrogenation mediated by Oppolzer’s sultam is used to demonstrate this concept. In order to achieve cycles such as the one discussed in Chapter two, the ability to telescope reactions in flow is paramount. However, solid handling challenges are frequent when transitioning to flow, leading to limitations in potential solvents or conditions in order to achieve homogeneity. This complicates the ability to telescope reactions, and to address this challenge the work in Chapter three focuses on the development of a general and simple solution to negate precipitation problems arising from precipitation of base·HX salts, a frequent reaction by-product of common reactions. By using bases that form low- to moderate-melting salts upon protonation, precipitation is precluded while reactions are performed above the melting point of the base·HX salt. This is shown to be applicable for a wide variety of substitution reactions and allow facile reaction telescoping. Chapter four focus on overcoming severe scope limitations in palladium catalyzed transformations that result when rapid background reactions deplete the nucleophilic coupling partner faster than catalyst turnover. This work starts with real-time MS investigations to investigate why slow addition of Grignard or organolithium nucleophiles facilitates substantial scope expansion in Kumada-Corriu or Murahashi cross-couplings, and then uses the information gleaned from these studies to significantly expand the accessible scope of palladium catalyzed aryl halide–diazo cross-coupling, through controlled addition of the diazo reagent at a rate that approximates aryl halide oxidative addition, in combination with on-demand flow synthesis of non-stabilized diazo reagents. Chapter five focuses on improving efficiency in the collection of kinetic data in flow, by developing a reaction cycling reactor. Conversion over time data is obtained by passing a discrete reaction slug back-and-forth between two residence coils, with analysis performed each time the solution passes from one coil to the other. In contrast to a traditional steady state flow system, which requires >5 X the total reaction time to collect data, this reactor design collects all the data during a single reaction. Multiple reactions can also be monitored at the same time by performing multiple reactions as sequential slugs in the reactor. The reactor is demonstrated by application to a wide variety of transformations and different methods of kinetic analysis.
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鄧文偉 and Man-wai Simon Tang. "Novel cyclic ketones for catalytic epoxidation of olefins." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31214654.

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Tang, Man-wai Simon. "Novel cyclic ketones for catalytic epoxidation of olefins /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1853871X.

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Rothnie, Alice. "TM6 of Pgp : changes in topography during the catalytic cycle." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401107.

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Belcastro, Elizabeth Lynn. "Life Cycle Analysis of a Ceramic Three-Way Catalytic Converter." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32342.

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The life cycle analysis compares the environmental impacts of catalytic converters and the effects of not using these devices. To environmentally evaluate the catalytic converter, the emissions during extraction, processing, use of the product are considered. All relevant materials and energy supplies are evaluated for the catalytic converter. The goal of this life cycle is to compare the pollutants of a car with and without a catalytic converter. Pollutants examined are carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (HC), and nitrogen oxides (NOx). The main finding is that even considering materials and processing, a catalytic converter decreases the CO, HC and NOx pollutant emissions. The CO2 emissions are increased with a catalytic converter, but this increase is small relative to the overall CO2 emissions. The majority of catalytic converter pollutants are caused by the use phase, not extraction or processing. The life cycle analysis indicates that a catalytic converter decreases damage to human health by almost half, and the ecosystem quality damage is decreased by more than half. There is no damage to resources without a converter, as there are no materials or energy required; the damages with a converter are so small that they are not a significant factor. Overall, catalytic converters can be seen as worthwhile environmental products when considering short term effects like human health effects of smog, which are their design intent. If broader environmental perspectives that include climate change are considered, then the benefits depend on the weighting of these different environmental impacts.
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Books on the topic "Catalytic cycles"

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Malleron, Jean-Luc. Handbook of palladium-catalyzed organic reactions: Synthetic aspects and catalytic cycles. London: Academic, 1997.

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Malleron, Jean-Luc. Handbook of palladium-catalyzed organic reactions: Synthetic aspects and catalytic cycles. San Diego: Academic Press, 1997.

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Britain, Great. Motor Cycles etc. (Replacement of Catalytic Converters) Regulations 2009. Stationery Office, The, 2009.

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Britain, Great. Motor Cycles etc. (Replacement of Catalytic Converters) and Motor Vehicles (Replacement of Catalytic Converters and Pollution Control Devices) (Amendment) Regulations 2011. Stationery Office, The, 2011.

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(Editor), Alain Juin, and Jean-Luc Malleron (Editor), eds. Database of Palladium Chemistry: Reactions, Catalytic Cycles and Chemical Parameters Cd-Rom Version 1.0. Academic Pr, 1996.

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1851-1941, Miller Isaiah M., and Langley Research Center, eds. Optimization of the catalytic oxidation of CO for closed-cycle CO laser applications. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1985.

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United States. National Aeronautics and Space Administration., ed. Design of catalytic monoliths for closed-cycle carbon dioxide lasers: Final project report. [Washington, DC: National Aeronautics and Space Administration, 1989.

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United States. National Aeronautics and Space Administration., ed. Design of catalytic monoliths for closed-cycle carbon dioxide lasers: Mid-project progress report. La Jolla, CA: Dept. of Applied Mechanics and Engineering Sciences, University of California at San Diego, 1988.

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Book chapters on the topic "Catalytic cycles"

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Vaz, Alfin D. N., Elizabeth S. Roberts, and Minor J. Coon. "Radical Intermediates in the Catalytic Cycles of Cytochrome P-450." In Oxygen Radicals in Biology and Medicine, 501–7. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4684-5568-7_77.

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Kozuch, Sebastian. "Is There Something New Under the Sun?Myths and Facts in the Analysis of Catalytic Cycles." In Understanding Organometallic Reaction Mechanisms and Catalysis, 217–48. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527678211.ch9.

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Nur, Alam S. M., A. Yamashita, T. Matsukawa, T. Kawada, and M. Machida. "Catalytic SO3 Decomposition Activity and Stability of Supported Molten Vanadate Catalysts for Solar Thermochemical Water Splitting Cycles." In Ceramic Transactions Series, 235–43. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2018. http://dx.doi.org/10.1002/9781119494096.ch24.

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Amsterdam, A., F. Pitzer, U. Santarius, A. Dantes, and W. Baumeister. "Possible Role of the Multi Catalytic Proteinase (Proteasome) in Regulating of the Cell Cycle." In The Cell Cycle, 203–9. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4615-2421-2_24.

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Cenini, Sergio, and Fabio Ragaini. "Synthesis of Other Non-Cyclic Compounds." In Catalytic Reductive Carbonylation of Organic Nitro Compounds, 132–76. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-017-0986-6_4.

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Ting, Allen Wei-Lun, Michael P. Harold, and Vemuri Balakotaiah. "Chapter 8. NOx Storage and Reduction: Effects of Pt Dispersion, Reductant Type, and Cycle Timing." In Catalysis Series, 213–44. Cambridge: Royal Society of Chemistry, 2018. http://dx.doi.org/10.1039/9781788013239-00213.

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Gu, Lichuan, and Qing He. "A Unified Catalytic Mechanism for Cyclic di-NMP Hydrolysis by DHH–DHHA1 Phosphodiesterases." In Microbial Cyclic Di-Nucleotide Signaling, 79–92. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-33308-9_5.

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Ho, Raymond, and Joan Selverstone Valentine. "Iron Complexes of Cyclam and Cyclam-Like Ligands as Models for Non-Heme Iron Enzymes." In The Activation of Dioxygen and Homogeneous Catalytic Oxidation, 460. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-3000-8_51.

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Bhatt, Jay M., and Ricardo A. Bernal. "Single-Ring Intermediates in the Catalytic Cycle of the Human Mitochondrial Hsp60." In Heat Shock Protein 60 in Human Diseases and Disorders, 15–25. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-23154-5_2.

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Weiss, Alvin H., John Cook, Richard Holmes, Natka Davidova, Pavlina Kovacheva, and Maria Traikova. "Redox Cycle During Oxidative Coupling of Methane over PbO—MgO—Al2O3Catalyst." In Novel Materials in Heterogeneous Catalysis, 243–53. Washington, DC: American Chemical Society, 1990. http://dx.doi.org/10.1021/bk-1990-0437.ch022.

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Conference papers on the topic "Catalytic cycles"

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Massardo, A. F., and B. Bosio. "Assessment of Molten Carbonate Fuel Cell Models and Integration With Gas and Steam Cycles." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0174.

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The aim of this work is to investigate the performance of Molten Carbonate Fuel Cells (MCFCs), with external reforming and Gas Turbine/Steam Turbine (GT/ST) combined cycles. The analysis of these MCFC-GT/ST combined cycles has been carried out using the Thermo Economic Modular Program TEMP (Agazzani and Massardo, 1997) modified to allow MCFC, external sensible heat reformer, and catalytic burner performance to be carefully taken into account. The code has been verified through the use of a detailed MCFC model (Bosio et al., 1999) and of the data available for an existing MCFC unit. The thermodynamic and exergy analysis of a number of MCFC combined cycles is presented and discussed, taking into account the influence of technological constraints, also evaluated with the sophisticated model, and the influence of the post-combustion of the fuel directly in the external catalytic burner. The results are presented and discussed in depth.
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Klaeyle, M. M. S., R. Laurent, and F. Nandjee. "New Cycles for Methanol-Fuelled Gas Turbines." In ASME 1987 International Gas Turbine Conference and Exhibition. American Society of Mechanical Engineers, 1987. http://dx.doi.org/10.1115/87-gt-175.

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Assuming that methanol is employed as fuel, the heat released from the gas turbine discharges can be used to cause an endothermic catalytic reaction: CH3 OH + H2 O + heat → 0,5 CO + 0,5 CO2 + 2,5 H2 + 0,5 H2 O; this produces a gaseous fuel, the lower heaving value of which exceeds that of methanol by 18%. Combining both steam reforming of methanol and steam injection in the combustor by using the maximum heat available in the exhaust gases, very interesting cycle characteristics can be achieved (more than 50% efficiency (LHV basis), same capital cost per kW as simple cycle gas turbine (9000E engine), low emissions of NOx and SO2). Reheating the gas during the expansion will improve the efficiency by 2–3 points allowing an increase in power output without increasing the capital cost per kW. At the end of the century, these types of cycles could be applied to all the new, non-nuclear power plants in the French energy system. The annual cumulative duration of such generators will not be greater than 2000 hours.
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Carcasci, Carlo, Bruno Facchini, and Simon Harvey. "Design and Off-Design Analysis of a CRGT Cycle Based on the LM2500-STIG Gas Turbine." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-036.

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Significant research effort is currently centered on developing advanced gas turbine systems for electric power generation applications. A number of innovative gas turbine cycles have been proposed lately, including the Humid Air Turbine (HAT), and the Chemically Recuperated Gas Turbine (CRGT). The potential of the CRGT cycle lies in the ability to generate power with a high efficiency while achieving ultra-low NO emissions without the need for selective catalytic reduction of the exhaust gases. Much of the research work published on the CRGT cycle is restricted to an analysis of the thermodynamic potential of the cycle. However, a detailed performance analysis of such cycles requires the development of a suitable cycle simulation code, capable of simulating cycle operation at the design point and in part load conditions. In this paper, the authors present a modular code for complex gas turbine cycle simulations. The code includes a module for design and off-design simulation of the methane-steam reformer chemical heat recovery device of a CRGT cycle. The code is then used to perform a detailed design and off-design performance analysis of a CRGT cycle based on the LM2500-STIG cycle adapted for chemical recuperation.
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4

Rubeli, Brent, Mahe Gangal, Stephen Hardcastle, and Gianni Caravaggio. "Evaluation of Selective Catalytic Reduction Technology Retrofit for NOx Reduction in Diesel Mining Vehicles." In ASME 2012 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icef2012-92034.

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Two heavy-duty diesel vehicles operating in an underground salt mine were retrofitted with emission control systems based on selective catalytic reduction technology. The vehicles were then released for production in the mine and the emissions were measured periodically over 18 months. The systems were very effective in reducing oxides of nitrogen (NOx) emissions from the diesel vehicle engines. The systems were able to provide NOx reductions of 60% to 65% over typical vehicle duty cycles. This paper will describe the SCR systems, emissions reductions, operability issues and secondary emissions for both vehicles.
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Carr, Nick A., Kraig S. Shipley, and David J. Dewees. "Case History Fitness-for-Service Assessment of Cyclic Catalytic Reformer Motor Operated Valves in the Petrochemical Industry." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57660.

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Reactors of cyclic catalytic reformers require catalyst regeneration about every 7 days (∼50 cycles per year). To facilitate the in situ regeneration, large diameter motor operated valves (MOV) are used (typically Class 600 NPS 8 to NPS 16 API 600 gate block valves). Double block-n-bleed arrangements of the MOVs are used to assure isolation of the 350 psig 960°F process and regeneration media. The regeneration MOVs will be closed and in isolation for up to 4 days and can reach temperatures close to ambient depending on their distance from the process flow. Once the MOVs are swung open, the valve body quickly transitions from ambient temperature to 960°F over a matter of minutes. Such an extreme thermal shock has historically led to a number of cracks in the MOV valve bodies. With each unit having over 50 MOVs, it becomes expensive and time consuming to open every MOV at a scheduled turnaround, inspect, and repair any cracking noticed.
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Alexander, Chris, and Richard Boswell. "Techniques for Modeling Thermal and Mechanical Stresses Generated in Catalytic Cracker and Coke Drum Hot Boxes." In ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71728.

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Consideration of heat transfer loading between surfaces during transient and steady state conditions is required when analyzing vessels that involve secondary stresses and low cycle fatigue. Some of the higher stresses occur in enclosed, non-insulated air space regions, referred to as a hot box, between a supporting skirt (or shell) and a vessel. Hot boxes are critical parts of vessel designs in catalytic crackers and delayed coke drums. In coke drum cycles, the sudden heating of the vessel generates significant bending stresses in the skirt, and radiation heat transfer causes a greater area of skirt to be heated when compared to conduction alone. This heat must be removed during the cooling transient or the hot expanded skirt will be pulled by the contracting vessel, resulting in large bending stresses. It is the experiences of the authors that failures to calculate the transient temperatures in the components often underestimate fatigue stresses. Some of the important elements associated with modeling thermal stresses in hot boxes include using appropriate boundary conditions, radiation and convection conditions, pressure end loads, and conductivities for the insulation materials. This paper emphasizes the importance of performing detailed sensitivity analyses when unknown thermal or mechanical loading conditions exist. Examples include the effects of convection properties within the hotbox and conditions associated with transient loads. Discussions are also provided on the potential geometric issues associated with the use of axisymmetric finite element models. Additionally, this paper discusses the importance of making field measurements to enhance modeling assumptions. Discussions will be provided on the best methods for acquiring field data and the techniques employed.
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Kuchi, Gayatri, Valery Ponyavin, Yitung Chen, Steven Sherman, and Anthony E. Hechanova. "Flow Distribution on the Tube Side of a High Temperature Heat Exchanger and Chemical Decomposer." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42652.

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Numerical simulations of a high temperature shell and tube heat exchanger and chemical decomposer (thereafter — heat exchanger) with straight tube configuration have been performed using Fluent 6.2.16 code to examine flow distribution on the tube side. The heat exchanger can be a part of sulfur iodine thermochemical water splitting cycle which is one of the most studied cycles for hydrogen production. Uniformity of the flow distribution in the heat exchanger is very critical because the flow maldistribution among the tube or shell sides can result in decreasing of chemical decomposition and increasing of pumping power. In the current study the flow rate uniformity in the heat exchanger tubes has been investigated. Simulations of the straight tube configuration, tube configuration with baffle plate arrangement and with pebble bed region inside the tubes were performed to examine flow distribution on the tube side. It was found the flow maldistribution along the tube direction is very serious with the simple tube configuration. An improvement of the header configuration has been done by introducing a baffle plate in to the header section. With the introduction of the baffle plate, there was a noticeable decrease in the flow maldistribution in the tubes. Uniformity of flow was also investigated with catalytic bed inside the tubes. A significant decrease in flow maldistribution was observed with this arrangement. But if the catalytic bed zone is created on the shell side, then the improved header configuration with a baffle plate is best suitable to avoid flow maldistribution.
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Yang, Kuo, and Pingen Chen. "Model Predictive Air-Fuel Ratio Control for an Integrated Gasoline Engine and Three-Way Catalytic Converter System." In ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-9072.

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With increasingly demanding regulations on engine emission and fuel efficiency, the optimization of the internal combustion engine and the after-treatment integrated system has become a critical research focus. To address such an issue, this paper aims to achieve a better trade-off between the fuel consumption of a spark-ignited (SI) engine and emission conversion efficiencies of a Three-Way Catalytic converter (TWC) system. A Model Predictive Control (MPC)-based integrated engine and TWC control methodology is presented, which is able to optimize Air/Fuel Ratio (AFR) to maintain oxygen storage of TWC at a desired level and thus meet the tailpipe NOx, CO and HC emission requirements. The effectiveness of the presented control methodology is validated in simulation. Compared with the existing dithering-based AFR control, the proposed MPC-based AFR control can improve CO emission conversion efficiencies by 8.42% and 4.85% in simplified US06 and UDDS driving cycles, respectively. At the same time, Nitrogen Oxides (NOx) conversion efficiency maintains above the required limit of 95% and the fuel efficiency remains at the same level as the existing control methodology in production as well. Such an integrated engine-aftertreatment system control can be instrumental in improving engine efficiency and emission reduction performance.
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9

Kappanna, Hemanth K., Marc C. Besch, Arvind Thiruvengadam, Pragalath Thiruvengadam, Peter Bonsack, Daniel K. Carder, Mridul Gautam, et al. "Evaluation of Drayage Truck Chassis Dynamometer Test Cycles and Emissions Measurement." In ASME 2012 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icef2012-92106.

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In 2006, the ports of Long Beach and Los Angeles adopted the final San Pedro Bay Ports Clean Air Action Plan (CAAP), initiating a broad range of programs intended to improve the air quality of the port and rail yard communities in the South Coast Air Basin. As a result, the Technology Advancement Program (TAP) was formed to identify, evaluate, verify and accelerate the commercial availability of new emissions reduction technologies for emissions sources associated with port operations, [1]. Container drayage truck fleets, an essential part of the port operations, were identified as the second largest source of NOx and the fourth largest source of diesel PM emissions in the ports’ respective 2010 emissions inventories [2, 3]. In response, TAP began to characterize drayage truck operations in order to provide drayage truck equipment manufacturers with a more complete understanding of typical drayage duty cycles, which is necessary to develop emissions reduction technologies targeted at the drayage market. As part of the broader TAP program, the Ports jointly commissioned TIAX LLC to develop a series of drayage truck chassis dynamometer test-cycles. These cycles were based on the cargo transport distance, using vehicle operational data collected on a second-by-second basis from numerous Class 8 truck trips over a period of two weeks, while performing various modes of typical drayage-related activities. Distinct modes of operation were identified; these modes include creep, low-speed transient, high-speed transient and high-speed cruise. After the modes were identified, they were assembled in order to represent typical drayage operation, namely, near-dock operation, local operation and regional operation, based on cargo transport distances [4]. The drayage duty-cycles, thus developed, were evaluated on a chassis dynamometer at West Virginia University (WVU) using a class 8 tractor powered by a Mack MP8-445C, 13 liter 445 hp, and Model Year (MY) 2011 engine. The test vehicle is equipped with a state-of-the-art emissions control system meeting 2010 emissions regulations for on-road applications. Although drayage trucks in the San Pedro Bay Ports do not have to comply with the 2010 heavy-duty emissions standards until 2023, more than 1,000 trucks already meet that standard and are equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) technology as used in the test vehicle. An overview of the cycle evaluation work, along with comparative results of emissions between integrated drayage operations, wherein drayage cycles are run as a series of shorter tests called drayage activities, and single continuous drayage operation cycles will be presented herein. Results show that emissions from integrated drayage operations are significantly higher than those measured over single continuous drayage operation, approximately 14% to 28% for distance-specific NOx emissions. Furthermore, a similar trend was also observed in PM emissions, but was difficult to draw a definite conclusion since PM emissions were highly variable and near detection limits in the presence of DPF. Therefore, unrepresentative grouping of cycle activity could lead to over-estimation of emissions inventory for a fleet of drayage vehicles powered by 2010 compliant on-road engines.
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10

Carcasci, Carlo, and Simon Harvey. "Design Issues for the Methane-Steam Reformer of a Chemically Recuperated Gas Turbine Cycle." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-035.

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Significant research effort is currently centered on developing advanced gas turbine systems for electric power generation applications. A number of innovative gas turbine cycles have been proposed lately, including the Humid Air Turbine (HAT), and the Chemically Recuperated Gas Turbine (CRGT). The potential of the CRGT cycle lies in the ability to generate power with a high efficiency while achieving ultra-low NO emissions without the need for selective catalytic reduction of the exhaust gases. However, much of the work that has been published on such cycles is restricted to a discussion of the thermodynamic potential of the cycle, and little work has focussed on discussion of some of the specific design issues associated with such a cycle. More specifically, design of the chemical recuperation heat recovery device involves a complex design trade-off in order to achieve a design with acceptable hot and cold-side pressure drops and acceptable overall dimensions. The design of such a heat recovery device is more complex than that of a traditional heat recovery steam generator (HRSG), since the methane steam reformer must not only allow sufficient heat transfer to occur, but also allow a sufficient cold side residence time, so that the methane steam reforming reactions can come close to equilibrium, ensuring maximal methane conversion. In this work, the authors present a code capable of performing the design of a methane steam reformer heat recovery device based on a heat exchanger geometry similar to that of a traditional HRSG. The purpose of the paper is to discuss the key parameters relevant to the design of a CRGT MSR reactor, and how these parameters interact with the rest of the cycle. Various design options are discussed, and the results of a parametric analysis are presented, leading to the identification of several suitable geometries.
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Reports on the topic "Catalytic cycles"

1

Rioux, Robert M. Dynamic Chemical and Structural Changes of Heterogeneous Catalysts Observed in Real Time: From Catalysis-Induced Fluxionality to Catalytic Cycles. Fort Belvoir, VA: Defense Technical Information Center, November 2014. http://dx.doi.org/10.21236/ada613847.

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2

Dickman, Martin B., and Oded Yarden. Phosphorylative Transduction of Developmental and Pathogenicity-Related Cues in Sclerotinia Sclerotiorum. United States Department of Agriculture, April 2004. http://dx.doi.org/10.32747/2004.7586472.bard.

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Sclerotinia sclerotiorum (Lib.) de Bary is among the world's most successful and omnivorous fungal plant pathogens. Included in the more than 400 species of plants reported as hosts to this fungus are canola, alfalfa, soybean, sunflower, dry bean, and potato. The general inability to develop resistant germplasm with these economically important crops to this pathogen has focused attention on the need for a more detailed examination of the pathogenic determinants involved in disease development. This proposal involved experiments that examined the involvement of protein phosphorylation during morphogenesis (hyphal elongation and sclerotia formation) and pathogenesis (oxalic acid). Data obtained from our laboratories during the course of this project substantiates the fact that kinases and phosphatases are involved and important for these processes. A mechanistic understanding of the successful strategy(ies) used by S . sclerotiorum in infecting and proliferating in host plants and this linkage to fungal development will provide targets and/or novel approaches with which to design resistant crop plants including interference with fungal pathogenic development. The original objectives of this grant included: I. Clone the cyclic AMP-dependent protein kinase A (PKA) catalytic subunit gene from S.sclerotiorum and determine its role in fungal pathogenicity, OA production (OA) and/or morphogenesis (sclerotia formation). II. Clone and characterize the catalytic and regulatory subunits of the protein phosphatase PP2A holoenzyme complex and determine their role in fungal pathogenicity and/or morphogenesis as well as linkage with PKA-regulation of OA production and sclerotia formation. III. Clone and characterize the adenylate cyclase-encoding gene from S . sclerotiorum and detennine its relationship to the PKA/PP2A-regulated pathway. IV. Analyze the expression patterns of the above-mentioned genes and their products during pathogenesis and determine their linkage with infection and fungal growth.
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Chamovitz, A. Daniel, and Georg Jander. Genetic and biochemical analysis of glucosinolate breakdown: The effects of indole-3-carbinol on plant physiology and development. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597917.bard.

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Genetic and biochemical analysis of glucosinolate breakdown: The effects of indole-3-carbinol on plant physiology and development Glucosinolates are a class of defense-related secondary metabolites found in all crucifers, including important oilseed and vegetable crops in the Brassica genus and the well-studied model plant Arabidopsis thaliana. Upon tissue damage, such as that provided by insect feeding, glucosinolates are subjected to catalysis and spontaneous degradation to form a variety of breakdown products. These breakdown products typically have a deterrent effect on generalist herbivores. Glucosinolate breakdown products also contribute to the anti-carcinogenic effects of eating cabbage, broccoli and related cruciferous vegetables. Indole-3-carbinol, a breakdown product of indol-3-ylmethylglucosinolate, forms conjugates with several other plant metabolites. Although some indole-3-carbinol conjugates have known functions in defense against herbivores and pathogens, most play as yet unidentified roles in plant metabolism, and possibly also plant development. At the outset, our proposal had three main hypotheses: (1) There is a specific detoxification pathway for indole-3-carbinol; (2) Metabolites derived from indole-3-carbinol are phloem-mobile and serve as signaling molecules; and (3) Indole-3-carbinol affects plant cell cycle and cell-differentiation pathways. The experiments were designed to enable us to elucidate how indole-3-carbinol and related metabolites affect plants and their interactions with herbivorous insects. We discovered that indole-3- carbinol rapidly and reversibly inhibits root elongation in a dose-dependent manner, and that this inhibition is accompanied by a loss of auxin activity in the root meristem. A direct interaction between indole-3-carbinol and the auxin perception machinery was suggested, as application of indole-3-carbinol rescued auxin-induced root phenotypes. In vitro and yeast-based protein interaction studies showed that indole-3-carbinol perturbs the auxin-dependent interaction of TIR1 with Aux/IAA proteins, supporting the notion that indole-3-carbinol acts as an auxin antagonist. Furthermore, transcript profiling experiments revealed the influence of indole-3-carbinol on auxin signaling in root tips, and indole-3-carbinol also affected auxin transporters. Brief treatment with indole-3-carbinol led to a reduction in the amount of PIN1 and to mislocalization of PIN2. The results indicate that chemicals induced by herbivory, such as indole-3-carbinol, function not only to repel herbivores, but also as signaling molecules that directly compete with auxin to fine tune plant growth and development, which implies transport of indole-3- carbinol that we are as yet unsuccessful in detecting. Our results indicate that plant defensive metabolites also have secondary functions in regulating aspects of plant metabolism, thereby providing diversity in defense-related plant signaling pathways. Such diversity of of signaling by defensive metabolites would be beneficial for the plant, as herbivores and pathogens would be less likely to mount effective countermeasures. We propose that growth arrest can be mediated directly by the herbivory-induced chemicals, in our case, indole-3-carbinol. Thus, glucosinolate breakdown to I3C following herbivory would have two outcomes: (1) Indole-3-carbinaol would inhibit the herbivore, while (2) at the same time inducing growth arrest within the plant. Thus, our results indicate that I3C is a defensive phytohormone that modulates auxin signaling, leading to growth arrest.
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