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Статті в журналах з теми "Relay catalysis":
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Lee, Sang-gi, Kyu Ree Lee, Yu Lim Lee, and Kyu In Choi. "Cooperative Rh(II)/Pd(0) Dual Catalysis for the Synthesis of Carbo- and Heterocyclic Compounds." Synthesis 54, no. 03 (September 29, 2021): 555–64. http://dx.doi.org/10.1055/a-1657-2068.
Анотація:
AbstractDual transition-metal catalysis has been introduced as a robust tool to synthesize a diverse range of organic compounds that cannot to be accessed by traditional single-metal catalysis. In this context, we have recently developed cooperative Rh(II)/Pd(0) dual catalytic systems that have been utilized for the preparation of heterocyclic compounds through the reaction between Rh(II)-carbenoid and π-allyl Pd(II)-complex intermediates in either synergistic or tandem relay catalysis. In synergistic Rh(II)/Pd(0) dual catalysis, the two reactive intermediates are generated simultaneously, which then undergo formal [6+3] dipolar cycloaddition to afford medium-sized heterocyclic compounds. On the other hand, tandem relay dual catalysis can be enabled through judicious choice of reaction parameters, which proceed through the insertion of Rh(II)-carbenoid into O–H or C–H bonds, followed by Pd(0)-catalyzed allylation to provide allylated benzo-fused cyclic compounds or chiral β-lactam derivatives.1 Introduction2 Synergistic Dual Rh(II)/Pd(0)-Catalyzed Dipolar [6+3]-Cycloaddition for the Synthesis of 1,4-Oxazonines3 Tandem Relay Dual Rh(II)/Pd(0) Catalysis for the Synthesis of 2-Aminoindanones4 Asymmetric Tandem Relay Dual Rh(II)/Pd(0) Catalysis for the Synthesis of α-Quaternary Chiral β-Lactams5 Tandem Relay Dual Rh(II)/Pd(0) Catalysis for the Synthesis of α-Quaternary Indolinones and Benzofuranones6 Conclusion
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Jeso, Valer, and Glenn C. Micalizio. "Relay catalysis at a boron centre." Nature 494, no. 7436 (February 2013): 179–81. http://dx.doi.org/10.1038/494179a.
3
Zhang, Yu, Xiao-Ling Feng, Jia-Ye Ni, Bo Fu, Hai-Min Shen, and Yuan-Bin She. "Efficient Inhibition of Deep Conversion of Partial Oxidation Products in C-H Bonds’ Functionalization Utilizing O2 via Relay Catalysis of Dual Metalloporphyrins on Surface of Hybrid Silica Possessing Capacity for Product Exclusion." Biomimetics 9, no. 5 (April 29, 2024): 272. http://dx.doi.org/10.3390/biomimetics9050272.
Анотація:
To inhibit the deep conversion of partial oxidation products (POX-products) in C-H bonds’ functionalization utilizing O2, 5-(4-(chloromethyl)phenyl)-10,15,20-tris(perfluorophenyl)porphyrin cobalt(II) and 5-(4-(chloromethyl)phenyl)-10,15,20-tris(perfluorophenyl)porphyrin copper(II) were immobilized on the surface of hybrid silica to conduct relay catalysis on the surface. Fluorocarbons with low polarity and heterogeneous catalysis were devised to decrease the convenient accessibility of polar POX-products to catalytic centers on the lower polar surface. Relay catalysis between Co and Cu was designed to utilize the oxidation intermediates alkyl hydroperoxides to transform more C-H bonds. Systematic characterizations were conducted to investigate the structure of catalytic materials and confirm their successful syntheses. Applied to C-H bond oxidation, not only deep conversion of POX-products was inhibited but also substrate conversion and POX-product selectivity were improved simultaneously. For cyclohexane oxidation, conversion was improved from 3.87% to 5.27% with selectivity from 84.8% to 92.3%, which was mainly attributed to the relay catalysis on the surface excluding products. The effects of the catalytic materials, product exclusion, relay catalysis, kinetic study, substrate scope, and reaction mechanism were also investigated. To our knowledge, a practical and novel strategy was presented to inhibit the deep conversion of POX-products and to achieve efficient and accurate oxidative functionalization of hydrocarbons. Also, a valuable protocol was provided to avoid over-reaction in other chemical transformations requiring high selectivity.
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He, Yan-Hong, Yang Xiang, Da-Cheng Yang, and Zhi Guan. "Combining enzyme and photoredox catalysis for aminoalkylation of indoles via a relay catalysis strategy in one pot." Green Chemistry 18, no. 19 (2016): 5325–30. http://dx.doi.org/10.1039/c6gc00550k.
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Zhou, Wei, Kang Cheng, Qinghong Zhang, and Ye Wang. "Relay catalysis in the conversion of syngas." Chinese Science Bulletin 66, no. 10 (November 25, 2020): 1157–69. http://dx.doi.org/10.1360/tb-2020-1309.
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Cheng, Xing, Yinghua Yu, Zhifeng Mao, Jianxin Chen, and Xueliang Huang. "Facile synthesis of substituted 3-aminofurans through a tandem reaction of N-sulfonyl-1,2,3-triazoles with propargyl alcohols." Organic & Biomolecular Chemistry 14, no. 16 (2016): 3878–82. http://dx.doi.org/10.1039/c6ob00377j.
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Viertl, Wolfgang, Johann Pann, Richard Pehn, Helena Roithmeyer, Marvin Bendig, Alba Rodríguez-Villalón, Raphael Bereiter, et al. "Performance of enhanced DuBois type water reduction catalysts (WRC) in artificial photosynthesis – effects of various proton relays during catalysis." Faraday Discussions 215 (2019): 141–61. http://dx.doi.org/10.1039/c8fd00162f.
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Song, Chuanling, Jianwu Wang, and Zhenghu Xu. "Tandem metal relay catalysis: from cyclopropene to polysubstituted furan." Org. Biomol. Chem. 12, no. 31 (2014): 5802–6. http://dx.doi.org/10.1039/c4ob00987h.
Анотація:
Transmetalation is a key step in traditional coupling reactions. An efficient synthetic methodology of tetrasubstituted furans from cyclopropenes with Cu–Pd transmetalation relay catalysis was presented.
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Tripathi, Ravi, Rachel Glaves, and Dominik Marx. "The GTPase hGBP1 converts GTP to GMP in two steps via proton shuttle mechanisms." Chemical Science 8, no. 1 (2017): 371–80. http://dx.doi.org/10.1039/c6sc02045c.
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Tang, Xinxin, Lan Gan, Xin Zhang, and Zheng Huang. "n-Alkanes to n-alcohols: Formal primary C─H bond hydroxymethylation via quadruple relay catalysis." Science Advances 6, no. 47 (November 2020): eabc6688. http://dx.doi.org/10.1126/sciadv.abc6688.
Анотація:
Nature is able to synergistically combine multiple enzymes to conduct well-ordered biosynthetic transformations. Mimicking nature’s multicatalysis in vitro may give rise to new chemical transformations via interplay of numerous molecular catalysts in one pot. The direct and selective conversion of abundant n-alkanes to valuable n-alcohols is a reaction with enormous potential applicability but has remained an unreached goal. Here, we show that a quadruple relay catalysis system involving three discrete transition metal catalysts enables selective synthesis of n-alcohols via n-alkane primary C─H bond hydroxymethylation. This one-pot multicatalysis system is composed of Ir-catalyzed alkane dehydrogenation, Rh-catalyzed olefin isomerization and hydroformylation, and Ru-catalyzed aldehyde hydrogenation. This system is further applied to synthesis of α,ω-diols from simple α-olefins through terminal-selective hydroxymethylation of silyl alkanes.
Дисертації з теми "Relay catalysis":
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Shinde, V. S. "Gold catalysis: development of relay catalytic branching cascades and chemosensors for detection of gold ions." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2014. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/1978.
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Jung, Giman. "The Charge-Relay System in Enzyme Catalysis : Construction and Function of Active Site Residues in Carboxypeptidase Y." Kyoto University, 1999. http://hdl.handle.net/2433/181885.
Анотація:
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第7876号
農博第1034号
新制||農||776(附属図書館)
学位論文||H11||N3239(農学部図書室)
UT51-99-G470
京都大学大学院農学研究科農芸化学専攻
(主査)教授 林 力丸, 教授 佐藤 文彦, 教授 江崎 信芳
学位規則第4条第1項該当
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Lainer, Bruno. "A multicatalytic approach to enantio-, and diastereoselective arylation of alcohols." Electronic Thesis or Diss., Strasbourg, 2023. http://www.theses.fr/2023STRAF080.
Анотація:
Les groupements alcooliques sont présents dans une grande diversité de produits chimiques fins précieux issus de la nature et de la synthèse, c'est pourquoi les méthodes permettant leur diversification structurelle sont recherchées. Cependant, la modification de la structure des alcools à certaines positions non réactives, même avec l'aide de la catalyse, reste un défi ou nécessite des procédures multi-étapes fastidieuses et souvent coûteuses. Récemment, une attention accrue a été accordée à la multicatalyse, qui combine plusieurs catalyseurs au sein d'un même système, ce qui permet de découvrir des réactivités auparavant inaccessibles ou d'accroître l'efficacité globale des transformations en plusieurs étapes. Les méthodes décrites ici permettent l'α- et la β-arylation diastéréo- et énantiosélective d'alcools. En combinant des catalyseurs à base de Ru et de Pd, il est possible de réaliser une β-arylation énantiosélective (et diastéréodivergente dans le cas d'alcools portant déjà des stéréocentres) sans précédent d'alcools primaires. En outre, dans le cadre d'une catalyse relais séquentielle, il est possible d'obtenir des alcools benzyliques secondaires enrichis enantioénergie à partir de divers produits de départ disponibles, tels que des alcools primaires ou des alcools portant une double liaison. Dans l'ensemble, ces protocoles démontrent le potentiel de la multicatalyse en tant qu'outil synthétique pour diversifier les alcools. Dans un contexte plus large, cette thèse ouvre la voie à la conception de nouvelles stratégies et méthodes multicatalytiques pour une synthèse efficaceAlcohol moieties are present in a great diversity of valuable fine chemicals from nature and synthesis, therefore methods enabling their structural diversification are sought after. However, modifying the structure of alcohols at certain unreactive positions, even with the aid of catalysis, remains a challenge or requires tedious often wasteful multistep procedures. Recently, increased attention has been paid to multicatalysis, which combines multiple catalysts within one system, enabling the discovery of previously inaccessible reactivities or increasing the overall efficiency of multistep transformations. Described within are methods which enable the diastereo-, and enantioselective α-, and β-arylation of alcohols. By combining Ru- and Pd-based catalysts the unprecedented, enantioselective (and diastereodivergent in the case of alcohols already bearing stereocenters) β-arylation of primary alcohols can be carried out. Also, under sequential relay catalysis enantioenriched secondary benzylic alcohols can be obtained from a variety of available starting materials, such as primary alcohols, or alcohols bearing a double bond. Overall, these protocols demonstrate the potential of multicatalysis as a synthetic tool for diversifying alcohols. In a broader context, this thesis sets the stage for devising novel, multicatalytic strategies and methods for efficient synthesis
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Graham, Daniel John. "The Influence of Intramolecular Proton Relays on Catalysis." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17463970.
Анотація:
Global energy demand is predicted to increase at an alarming rate over the next century; in order to meet this demand while also limiting the effects of runaway climate change, society will need to shift toward renewable sources of energy. Many of the fundamental chemical transformations that store renewable energy as fuel require the addition or removal of protons. Optimization of catalysts that carry out these transformations can be achieved with proton management at the molecular level.
Deliberate construction of molecular catalysts with an intramolecular proton relay is one strategy for controlling the movement of protons during catalysis. These so-called “hangman” catalysts have been shown to increase the rate of catalysis in the cases of hydrogen evolution, oxygen reduction, hydrogen peroxide dismutation, and olefin epoxidation. A new class of hangman porphyrins is now available on the gram scale and can easily be further modified, allowing for unprecedented control the strength and character of pendant proton relays. Using iron complexes of these new hangman porphyrins, the level of control over proton management is demonstrated with the variation in the rates of hydrogen evolution electrocatalysis depending on the nature of the proton relay in the second coordination sphere.
Understanding the fundamental electron transfer reactions of reactive oxygen species (ROS) is important in the chemistry of renewable energy storage, but also in a biological context. Hydrogen bond donors are known to affect the electron transfer reactivity of ROS, with the strength of the hydrogen bond determining the nature of oxygen-oxygen bond activation. The catalytic performance of iron corroles towards peroxide dismutation is markedly enhanced by the presence of a pendant hydrogen bond donor which is also capable of transferring protons to bound substrates. Contrary to hangman corroles, the six hydrogen bond donors in hexacarboxamide cryptand do not readily transfer protons, allowing it to facilitate the chemically reversible two-electron reduction of dioxygen to “naked” peroxide dianion. Using electrochemical techniques and computational modeling, it is possible to use cryptand-encapsulated peroxide as a model for the electron transfer reactions within lithium-oxygen batteries.Chemistry and Chemical Biology
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Holtz-Mulholland, Michael. "Synthesis of transition metal N-heterocyclic carbene complexes and applications in catalysis." Thèse, 2014. http://hdl.handle.net/1866/11407.
Анотація:
Les ligands de carbènes N-hétérocycliques (NHC) qui possèdent une symétrie C1 attirent beaucoup l’attention dans la littérature. Le présent projet de recherche propose de synthétiser une nouvelle série de ligands NHC C1-symétriques avec deux groupements N-alkyles qui exploitent un relais chiral. Un protocole modulaire et efficace pour la synthèse des sels d’imidazolium chiraux qui servent comme préligands pour les NHC a été développé. Quelques-uns de ces nouveaux ligands ont été installés sur le cuivre et de l’or, créant de nouveaux complexes chiraux.
Les nouveaux complexes à base de cuivre ont été évalués comme catalyseurs pour le couplage oxydatif de 2-naphthols. Les ligands C1-symmétriques ont fourni des meilleurs rendements que les ligands C2-symmétriques. Au cours de l’optimisation, des additifs ont été évalués; les additifs à base de pyridine ont fourni des énantiosélectivités modérées tandis que les additifs à base de malonate ont donné des meilleurs rendements de la réaction de couplage oxydatif.
Ultérieurement, les additifs à base de malonate ont été appliqués envers l’hétérocouplage de 2-naphthols. Le partenaire de couplage qui est riche en électrons est normalement en grand excès à cause de sa tendance à dégrader. Avec le bénéfice de l’additif, les deux partenaires de couplage peuvent être utilisés dans des quantités équivalentes. La découverte de l’effet des additifs a permis le développement d’un protocole général pour l’hétérocouplage de 2-naphthols.A new class of C1-symmetric N-heterocyclic carbene (NHC) ligands has been developed. The new ligands exploit a biaryl methyne as a chiral relay, and an N-methyl group as a reactivity controlling element. The precursors for the new ligands were synthesized via a modular scheme that allows for facile diversification. Several of the new ligands were installed onto both copper and gold, generating mono N-heterocyclic carbene transition metal complexes. The new C1-symmetric copper complexes were tested as catalysts for the synthesis of binaphthols via the oxidative coupling of electron poor 2-naphthols. The new C1-symmetric ligands afforded higher yields than their C2-symmetric counterparts. During the course of the optimization, small molecule additives were found to modulate the reactivity of the copper catalyst. Pyridine additives, such as 2-picoline, were found to induce low to moderate enantioselectivity in the oxidative coupling reaction, while diethylmalonate was found to improve the reaction yield without affecting the selectivity. The malonate additive was employed in the catalytic oxidative heterocoupling of electronically dissimilar 2-naphthols. The electron-rich coupling partner is normally added in a large excess due to its tendency to degrade. When the malonate additive is used, the coupling partners can be used in equimolar quantities. The discovery resulted in the development of a general protocol for the additive assisted aerobic oxidative heterocoupling of electronically dissimilar 2-naphthols.
Книги з теми "Relay catalysis":
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Ziemann, Benjamin. Germany 1914–1918. Total War as a Catalyst of Change. Edited by Helmut Walser Smith. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780199237395.013.0017.
Анотація:
It is a commonplace to see the First World War as a major caesura in German and European history. This article records the war years from 1914–1918 in Germany. Not least, such an interpretation can rely on the perceptions of influential contemporary observers. In Germany, as in other belligerent countries, many artists, intellectuals, and academics experienced the outbreak of the war as a cathartic moment. While it is straightforward to see the mobilization for war and violence as a major caesura for any of the belligerent countries, it is much more complicated to account for causalities and for German peculiarities. Difficult methodological questions arise, which have not always been properly addressed. While Germany was facing a ‘world of enemies’, as a popular slogan suggested, the semantics of the political shifted to an articulation of emotions, excitements, and promises, contributing to a dramatized narrative centered around the notions of sacrifice and fate. The effect of World War I concludes the article.
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Ibarra, Enrique Ajuria. Cross-border Implications: Transnational Haunting, Gender and the Persistent Look of The Eye. Edinburgh University Press, 2018. http://dx.doi.org/10.3366/edinburgh/9781474424592.003.0010.
Анотація:
The Eye (Gin Gwai, 2002) and its two sequels (2004, 2005) deal with pan-Asian film production, gender, and identity. The films seem to embrace a transnational outlook that that fits a shared Southeast Asian cinematic and cultural agenda. Instead, they disclose tensions about Hong Kong’s identity, its relationship with other countries in the region, and its mixture of Western and Eastern traditions (Knee, 2009). As horror films, The Eye series feature transpositional hauntings framed by a visual preference for understanding reality and the supernatural that is complicated by the ghostly perceptions of their female protagonists. Thus, the issues explored in this film series rely on a haunting that presents textual manifestations of transposition, imposition, and alienation that further evidence its complicated pan-Asian look. This chapter examines the films’ privilege of vision as catalyst of a transnational, Asian Gothic horror aesthetic that addresses concepts of identity, gender, and subjectivity.
Частини книг з теми "Relay catalysis":
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Wang, Pu-Sheng, Dian-Feng Chen, and Liu-Zhu Gong. "Recent Progress in Asymmetric Relay Catalysis of Metal Complex with Chiral Phosphoric Acid." In Asymmetric Organocatalysis Combined with Metal Catalysis, 185–205. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-43851-7_8.
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Wan, H. L., J. W. Huang, F. Z. Zhang, Y. Wu, L. S. Xu, J. L. Li, and K. R. Tsai. "Molecular Recognition in Nitrogenase Catalysis and Two Proton-Relay Pathways from P-Cluster to M-Center." In Biological Nitrogen Fixation for the 21st Century, 78–79. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5159-7_28.
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Ueda, Yoshihiro, and Takeo Kawabata. "Sequential Site-Selective Functionalization: A Strategy for Total Synthesis of Natural Glycosides." In Modern Natural Product Synthesis, 439–60. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-1619-7_20.
Анотація:
AbstractTotal synthesis of several ellagitannins, strictinin (1), pterocarinin C (2), cercidinin A (3), and tellimagrandin II (19), is described. The key issues for the synthetic strategy rely on the catalyst-controlled site-selective acylation and stereoselective glycosylation with unprotected glucose. Total synthesis of punicafolin (5) with a glucose core in 1C4 (chair) conformation and macaranganin (30) with a glucose core in 5S1 (skew boat) conformation was also accomplished based on a similar unconventional retrosynthetic route. For success in the synthesis of 5 and 30, the flipping behavior of the pyranose ring from the stable 4C1 conformer to the unstable axial-rich 1C4 conformer is the key. Because no protective groups for glucose were employed throughout the synthesis of these natural glycosides, the total synthesis was achieved in extremely short overall steps.
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Tocco, Fabrice, and Laurent Lafaye. "Data Platform Solutions." In Designing Data Spaces, 383–93. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-93975-5_23.
Анотація:
AbstractPrivate and public organizations hoard troves of data yet remain unable to unlock its full business potential. Data exchange platforms powered by adapted technology and driven by data exchange strategies act as catalysts to develop data ecosystems and data spaces, accelerate data circulation, and liberate its value.Data spaces are powerful business, innovation, and societal enablers, whose growth and success rely on their ability to foster and develop trust.Data exchange platforms contribute a lot to building trust as they provide the required tools and automation to data acquirers, data providers, and data exchange services providers to operate at scale within secure and compliant environments.New and upcoming European regulatory frameworks also contribute to raising trust as they foster a harmonized data ecosystem across member states and define the rules of engagement between businesses, governments, and individuals engaged in data sharing and exchange.Additionally, data exchange environments must provide traceability at all levels of the data transactions, which is particularly needed in increasingly complex data ecosystems.Finally, in order to provide the flexibility required to answer the needs of complex, distributed, and heterogeneous environments, different models of data exchange governance are necessary.
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Wu, Chen-Fa, Chen Yang Lee, Chen-Chuan Huang, Hao-Yun Chuang, Chih-Cheng Weng, Ming Cheng Chen, Choa-Hung Chang, Szu-Hung Chen, Yi-Ting Zhang, and Kuan Chuan Lu. "Sustainable Rural Development and Water Resources Management on a Hilly Landscape: A Case Study of Gonglaoping Community, Taichung, ROC (Chinese Taipei)." In Fostering Transformative Change for Sustainability in the Context of Socio-Ecological Production Landscapes and Seascapes (SEPLS), 115–31. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-6761-6_7.
Анотація:
AbstractThe Gonglaoping community is located in Central Western Taiwan, with approximately 700 residents. The hilly landscape contains farmlands and sloping areas with abundant natural resources. Locals rely on the Han River system and seasonal rainfall for water supply for domestic use and irrigation. Uneven rainfall patterns and high demand for water has led to the overuse of groundwater and conflicts among the people. The surrounding natural forests provide important ecosystem services, including wildlife habitats and water conservation, among others; however, overlap with human activities has brought threats to biodiversity conservation. Considering these challenges, locals were determined to transform their community towards sustainability. The Gonglaoping Industrial Development Association (GIDA) and the Soil and Water Conservation Bureau (SWCB) joined hands to initiate the promotion of the Satoyama Initiative, playing catalytic roles in several implementations, such as establishing water management strategies based on mutual trust, rebuilding the masonry landscape, and economic development, forming partnerships with other stakeholders. This multi-stakeholder and co-management platform allowed the community to achieve transformative change, particularly in resolving conflicts of water use, restoring the SEPL, enhancing biodiversity conservation, and developing a self-sustaining economy.Achieving sustainability in a SEPL requires the application of a holistic approach and a multi-sector collaborating (community-government-university) platform. This case demonstrates a practical, effective framework for government authorities, policymakers and other stakeholders in terms of maintaining the integrity of ecosystems. With the final outcome of promoting a vision of co-prosperity, it is a solid example showing a win-win strategy for both the human population and the farmland ecosystem in a hilly landscape.
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Shao, Z., and Y. H. Deng. "2.1.1 General Principles of Metal/Organocatalyst Dual Catalysis." In Dual Catalysis in Organic Synthesis 2. Stuttgart: Georg Thieme Verlag, 2020. http://dx.doi.org/10.1055/sos-sd-232-00002.
Анотація:
AbstractMetal/organocatalyst dual catalysis is a privileged catalytic strategy which involves both a metal-based catalyst and an organocatalyst to catalyze the organic transformation. Based on the type of activation of substrates with both catalysts, there are seven kinds of dual catalysis; namely cooperative catalysis, cascade catalysis, sequential catalysis, double activation catalysis, restorative catalysis, bifunctional catalysis, and multiple relay catalysis. The generic activation of the metal-based catalyst and the organocatalyst applied in the dual-catalytic system is summarized. In these dual-catalytic approaches, the advantages of both metal catalysis and organocatalysis are converged to achieve many transformations that were previously inaccessible or challenging by any single-catalyst paradigm, to develop new reactions, to discover unique reaction mechanisms, and even to allow for stereodivergent synthesis.
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Han, Z. Y., C. Wang, and L. Z. Gong. "Relay Catalysis of Brønsted Acids with Transition-Metal Complexes." In Brønsted Base and Acid Catalysts, and Additional Topics, 1. Georg Thieme Verlag KG, 2012. http://dx.doi.org/10.1055/sos-sd-205-00533.
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Roy, Arindam, and Dr Madhumita Mukhopadhyay. "A REVIEW ON ELECTRO CATALYSIS OF OXYGEN REDUCTION REACTION: ENABLING SUSTAINABLE FUTURE ENERGY." In Futuristic Trends in Chemical Material Sciences & Nano Technology Volume 3 Book 22, 29–61. Iterative International Publishers, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3becs22p1ch3.
Анотація:
The field of electro catalysis, particularly the area of oxygen reduction reaction (ORR), has witnessed significant progress with far-reaching impacts in a variety of fields, as highlighted in recent research (Li et al.). Through the ORR mechanism, electro catalysis plays an important part in natural processes such as respiration, where it improves the conversion of oxygen to water in living organisms (Lane et al.). Theoretical importance does not restrict our comprehension of ORR processes in these biological systems. This has far-reaching implications for biomedical technology, such as implanted biosensors and biofuel cells (Li et al.). To optimize their performance, these technologies rely on efficient and selective ORR catalysts. Because of their high catalytic activity, noble metal catalysts such as platinum traditionally, platinum (Pt) and palladium (Pd) have been used as standards (Gasteiger et al.). Because of their scarcity and expensive cost, researchers have been pushed to investigate alternatives, resulting in substantial development in the design and synthesis of non-precious metal catalysts. As feasible alternatives, transition metal compounds, metal-free carbon materials, and hybrid Nano materials with high ORR activity, selectivity, and stability have developed (Zhu et al. the). These alternatives offer long-term and cost- effective energy transition solutions, indicating a significant shift in the catalytic environment. ORR electro catalysts hold the key to designing a more sustainable future, alongside their relevance in life sciences, biomedical technology, and fuel cells. In the future, the development of these catalysts will be critical in addressing global concerns such as renewable energy generation and environmental sustainability. Non-precious metal catalyst advances, as well as continued research into ORR processes, are opening the path for more efficient and sustainable beneficial energy conversion technologies. The chapter investigates the critical function of ORR electro catalysis in fuel cells, which transform chemical energy into electrical energy successfully. The incorporation of non-precious metal catalysts into fuel cells not only improves their performance but also adds to the progress of clean energy solutions. This is of particular significance as the globe encourages sustainable energy generation and lower greenhouse gas emissions. This includes the opportunity for widespread implementation of fuel cells as a clean energy source, reducing our dependence on fossil fuels and reducing the harmful effects of climate change.
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Seibel, Zara M., and Tristan H. Lambert. "Construction of Alkylated Stereocenters." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0035.
Анотація:
Hirohisa Ohmiya and Masaya Sawamura at Hokkaido University reported (Angew. Chem. Int. Ed. 2013, 52, 5350) the copper-catalyzed, γ-selective allylation of terminal alkyne 1 to produce the chiral skipped enyne 3 with high ee. A method to synthesize asymmetric skipped diene 6 via copper-catalyzed allylic allylation of diene 4 was developed (Chem. Commun. 2013, 49, 3309) by Ben L. Feringa at the University of Groningen. Prof. Feringa also disclosed (J. Am. Chem. Soc. 2013, 135, 2140) the regioselective and enantioselective allyl–allyl coupling of bromide 7 with allyl Grignard under Cu catalysis in the presence of phosphoramidite 8. James P. Morken of Boston College reported (Org. Lett. 2013, 15, 1432) the cross-coupling of allylboronate 11 with a mixture of alkenes 10a,b under palladium catalysis to produce diene 13 with high ee. Jian Liao at the Chengdu Institute of Biology Chinese Academy of Sciences and the University of Chinese Academy of Sciences reported (Angew. Chem. Int. Ed. 2013, 52, 4207) the palladium-catalyzed allylic alkylation of indole using the chiral bis(sulfoxide) phosphine ligand 15. Yi-Xia Jia at the Zhejiang University of Technology reported (J. Am. Chem. Soc. 2013, 135, 2983) the enantioselective alkylation of indole to produce the trifluoromethyl adduct 19 using nickel catalysis in the presence of bisoxazoline ligand 18. Sarah E. Reisman at the California Institute of Technology disclosed (J. Am. Chem. Soc. 2013, 135, 7442) the reductive cross-coupling of acid chloride 20 and benzyl chloride 21 using a nickel complex with bisoxazoline ligand 22 and manganese(0) as reductant. Ilan Marek at the Technion-Israel Institute of Technology reported (Angew. Chem. Int. Ed. 2013, 52, 5333) a method for the construction of all-carbon quaternary stereocenters, such as the one present in aldehyde 25, using a diastereoselective carbometallation of cyclopropene 24 followed by oxidation and ring opening. Switching from methyl Grignard and copper iodide to MeCuCNLi reverses the diastereoselectivity of the carbometallation and allows access to the opposite enantiomer. Matthew S. Sigman at the University of Utah reported (J. Am. Chem. Soc. 2013, 135, 6830) the redox–relay oxidative Heck arylation of alkenyl alcohol 27 with boronic acid 26 using a palladium catalyst and pyridine oxazole ligand 28 to produce the γ-substituted aldehyde 29.
10
Dunn, Ben M. "Determination Of Protease Mechanism." In Proteolytic Enzymes, 77–104. Oxford University PressOxford, 2001. http://dx.doi.org/10.1093/oso/9780199636631.003.0004.
Анотація:
Abstract The opening chapter of this volume has outlined the four mechanistic classes: serine and cysteine proteases (those that form covalent enzyme complexes) and aspartic and metalloproteases (those that do not form covalent enzyme complexes). This distinction into two major mechanistic groups is of profound con sequence since the strategy for inhibition is totally different for these two classes. Those enzymes of the first general class have strongly nucleophilic amino acids at their catalytic site. These are usually aligned with hydrogen bond acceptors to promote the dissociation of the nucleophile in the approach to the transition state and, thus, increase the fraction in the hyperreactive state, Design and synthesis of inhibitors of this broad class will therefore be concentrated on introduction of electrophilic groups (-C=C-, -C-C(=O)-Cl, etc,) that will chemically modify the nucleophile or general base. This will render the catalytic apparatus inactive and prevent the action of that protease. The second category of proteolytic enzymes includes two classes that catalyse the hydrolysis of peptide bonds without nucleophilic attack by a functional group of the enzyme. These enzymes rely more upon general acid/general base catalysis of the attack of a water molecule and therefore the catalytic residues lack the aggressive nucleophilicity of the serine or cysteine proteases. Inhibitor design for this second broad group relies on more subtle means of complexation, including a greater necessity for secondary binding interactions along the active-site cleft and transition state analogues. The metalloproteinases offer an additional handle for inhibitors, since functional groups such as -SH can be introduced at precise points to lead to nearly irreversible metal ion chelation.
Тези доповідей конференцій з теми "Relay catalysis":
1
Zhu, Shengrong, Jeffrey Hollowell, Kyoung-Pyo Ha, Nicholas Fantin, and Mark Shirley. "A Method to Reduce Cold Start Emissions while Shortening Fast Idle Catalyst Light-off Time." In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2023. http://dx.doi.org/10.4271/2023-01-0247.
Анотація:
<div class="section abstract"><div class="htmlview paragraph">For vehicles with internal combustion engines, tailpipe emissions heavily rely on the aftertreatment system, typically a catalytic converter. Modern three-way catalysts (TWC) can very effectively convert the unburnt hydrocarbons (HC), CO, and NO<sub>x</sub> into non-harmful gases such as H<sub>2</sub>O, CO<sub>2</sub>, and N<sub>2</sub> when the catalyst brick reaches a relatively high temperature. However, before that catalyst light-off temperature is reached, the emissions conversion efficiency is low, leading to high tailpipe emissions. Due to this light-off temperature requirement of the catalytic converter, the emissions from the engine cold-start period contributes a significant portion of vehicle overall emissions. One of the major reasons for high emissions during cold start is low combustion chamber wall temperatures, lower than the initial boiling temperature of gasoline fuel. This results in fuel film formation, and significantly incomplete evaporation prior to combustion. In this study, an approach to increase the fuel evaporation rate and fuel-air mixing for reduced cold start emissions while attaining fast catalyst light-off time is explored by using CVVD (continuously variable valve duration) & CVVT (continuously variable valve timing) mechanisms for both the intake and exhaust valvetrains. Early exhaust valve closing (EVC) and late intake valve opening (IVO) can be used to create negative valve overlap (NVO) for trapping hot exhaust gas residuals to facilitate fuel vaporization and reduce engine-out emissions during the engine cold-start and warm-up periods. In addition, early exhaust valve opening (EVO) timing can be employed to ensure fast catalyst light-off time. In this paper, a spark-ignited combustion engine is considered, and the engine-out emissions during the cold fast-idle period are studied. Both numerical simulations and engine testing are conducted to analyze the potential improvement of fuel vaporization and cold start emissions reductions with the proposed NVO approach.</div></div>
2
Ragaller, Paul, Josh Mandelbaum, Luc Lapenta, Alexander Sappok, Josh Pihl, Vitaly Prikhodko, and James Parks. "Direct Measurement of Ammonia Storage on Passive SCR Systems for Lean Gasoline NOx Reduction Using Radio Frequency Sensing." In ASME 2019 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/icef2019-7224.
Анотація:
Abstract Lean gasoline engine operation provides clear efficiency benefits relative to conventional stoichiometric combustion approaches. One of the key hurdles to the widespread, practical implementation of lean gasoline combustion remains the challenge of lean NOx control. One of the potential approaches for controlling NOx emission from lean gasoline engines is the so-called passive selective catalytic reduction (SCR) system. In such systems, periods of rich operation generate ammonia over a three-way catalyst (TWC), which is then adsorbed on the downstream SCR and consumed during lean operation. Brief periods of rich operation must occur in response to the depletion of stored ammonia on the SCR, which requires reliable measurements of the SCR ammonia inventory. Presently, lean exhaust system controls rely on a variety of gas sensors mounted up- and downstream of the catalysts, and which only provide an indirect inference of the operation state. In this study, a radio frequency (RF) sensor was used to provide a direction measurement of the amount of ammonia adsorbed on the SCR in real-time. The RF sensor was calibrated and deployed on a BMW N43B20 4-cylinder lean gasoline engine equipped with a passive SCR system. Brief periods of rich operation performed at lambda values between 0.98 and 0.99 generated the ammonia, subsequently stored on the SCR for consumption during periods of lean operation. The experiments compared real-time measurements of SCR ammonia inventory from the RF sensor with estimates of ammonia coverage derived from exhaust gas composition measurements upstream and downstream of the catalyst. The results showed a high degree of correlation between the RF measurements and SCR ammonia storage inventory, and demonstrated NOx conversion efficiencies above 98%, confirming the feasibility of the concept. Relative to stoichiometric operation, lean-gasoline operation resulted in fuel efficiency gains of up to 10%, which may be further improved through direct feedback control from the RF sensor to optimize lean–rich cycling based on actual, measured SCR ammonia levels.
3
Willsey, Aliza M., Thomas S. Welles, and Jeongmin Ahn. "Advancements in Nitric Oxide Emission Control With a Perovskite Based Membrane via High Frequency Electric Potential Oscillations." In ASME 2022 Power Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/power2022-85154.
Анотація:
Abstract Increased concerns over climate change, limited fossil fuel resources, emissions, and poor air quality has created a greater need for sustainable energy systems. The need for increased sustainable energy systems has created largely two cooperative movements: 1) technologies that are considered renewable or more environmentally friendly and 2) higher efficiency. The automotive industry has long been a target for increasing efficiency and decreasing environmentally harmful emissions. The combustion of hydrocarbon fuels results in harmful and reactive incomplete combustion byproducts. Fully electric and hybrid powertrains are increasing in commonality but have not yet fully penetrated the market. Many automobile manufacturers are still producing vehicles which rely solely on the internal combustion engine and hydrocarbon-based fuels. Currently, manufacturers utilize a combination of three-way catalytic converters and nitrogen oxide traps to rid the exhaust flow of harmful combustion emissions. Catalytic converters use expensive precious platinum group metals (PGM) to simultaneously react unwanted hydrocarbon, carbon monoxide, and nitrogen oxides into less harmful, complete products of combustion, such as nitrogen, carbon dioxide, and water vapor. However, the performance of these devices is highly dependent upon the equivalence ratio of the exhaust. Three-way catalysts require that the exhaust remain at stoichiometric conditions for optimal performance. Prolonged fuel lean engine operation renders the PGM catalyst incapable of reacting nitrogen oxide emissions. Nitrogen oxide, and more specifically nitric oxide (NO), emissions are of significant concern, as such emissions directly contribute to increased smog, acid rain, climate change, and respiratory inflammation within the population. Lean nitrogen oxide traps (LNTs) are incorporated into the exhaust system to temporarily capture excess nitrogen oxide emissions. However, the zeolite-based materials used in LNTs have a finite limit on nitrogen oxide storage capacity. Once nitrogen oxide capacity is reached, the engine must enter a fuel rich combustion condition or additional reactants must be injected directly into the exhaust system to regenerate the LNT’s function. Therefore, current exhaust treatment measures introduce significant complexity into the exhaust system and significant constraints on engine operation. As such, this work investigates the potential for new exhaust treatment materials, capable of maintaining performance across all conditions. Specifically, this work investigates the NO reduction potential of a multilayered ceramic electrochemical catalytic membrane. Prior work has demonstrated that the natural electric potential oscillation, which develops across such a membrane, significantly reduces NO emissions. The ceramic membrane, consisting of two dissimilar metal electrodes, sandwiching a dielectric layer, is able to achieve an NO reduction in excess of 2X that of a traditional PGM three-way catalytic converter [1]. Here, the possibility for externally inducing a low magnitude (< 500 mVpp), high frequency (> 1kHz) electric potential oscillation across the reacting membrane and increasing the conversion of NO into diatomic nitrogen and oxygen is investigated. Electric potential oscillation at the surface generates an altered electrochemical reaction pathway. During the breakdown of NO, N2O is recorded as an intermediate species without the introduction of NH3. This result diverges from traditional theory, which predicts the formation of NO2. This work further explores the relation between externally applied electric potential oscillation, N2O formation, and reduction of NO.
4
Zhan, Guodong David, Nicholas Lyons, Msalli Al Otaibi, Duanwei He, and Andrew Robertson. "A First Look at 100% Thermally Stable Polycrystalline Diamond (PCD) for Oil & Gas Drilling." In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210352-ms.
Анотація:
Abstract Since the late 1970's, research on the efficiency and cutting life of polycrystalline diamond compact (PDC) cutters identified elevated temperature due to frictional heating as one of the primary accelerants of wear to the diamond cutting edge. Temperatures as low as 700 °C activate the back-conversion process, whereby diamond transforms into graphite, due to the presence of catalytic metal in the diamond structure. The Oil and Gas industry responded by investing years developing technologies to reduce the temperatures that PDC's experience in application via improved hydraulics for cooling, higher quality surface finishes to reduce friction, and improved thermal stability via material structure and chemical treatments. PDC cutter technology has progressed substantially in the last 30+ years, but the challenge of synthesizing a perfectly thermally stable PDC still remains unmet until now. Recently, Zhan (2018, 2020, 2021a and 2021b) first developed a new strategy to synthesize ultrastrong and catalyst-free polycrystalline diamond (CFPCD) or binderless PDC cutters with a new world record as the hardest and tough diamond material and the highest thermal stability up to 1,400°C via his invented ultra-high pressure and ultra-high temperature (UHPHT) technology, which is three to seven times higher than conventional PDC cutters used in the industry. An initial laboratory study of a new catalyst-free extreme high pressure, high temperature CFPCD material provides the first instance of a catalyst metal free polycrystalline diamond structure that actually boosts rock cutting performance above and beyond that of the current state-of-the-art PDCs. Proof of concept CFPCD specimens were evaluated against commercial, state-of-the-art non-leached (NL) and deep leached (DL) PDC cutters in the lab. Two CFPCD grades, A & B, were run through a series of tests to evaluate their potential for rock cutting and, ultimately, for use in oil & gas drilling applications. Laboratory testing was conducted on vertical borer wear tests, KIC fracture toughness tests, and thermal degradation monitoring tests. Lab results reveal a threshold that must be exceeded in the synthesis of catalyst-free CFPCDs to achieve sufficient diamond intergrowth and structural integrity to surpass the current state-of-the-art DL PDCs. CFPCD grade A wore equivalently to a commercially available NL cutter and exhibited a toughness comparable to that of commercially available DL PDC material. Grade B, synthesized at a significantly higher pressure than grade A, cut 5.7 times the distance of a commercial NL PDC for an equivalent wearscar volume, and exhibited a 160 % reduction in wear volume comparing volume of diamond worn to volume of rock cut (or G ratios) to DL PDC after cutting the equivalent of roughly 50 miles of rock. The wearscar surface of Grade B also exhibited excellent integrity with no cracking or chipping damage compared to Grade A and commercial PDC grades. This is the first documented instance of a catalyst-free PDC achieving the best wear performance and integrity (fracture toughness) than the current PDC cutters offering on the market. Thermal stability limits of PDC cutters has greatly improved in the past 20 years, but the best commercial PDC's still rely on extending leach depths with certain performance limits. For the first time in the industry, there is a PDC material than shifts this boundary without the use of catalysts and leaching technology, producing a truly differentiable PDC cutter.
5
Xia, Yang, and Chai Kiat Yeo. "Using mobile relays as connectivity catalyst for highly mobile networks." In 2014 IEEE Wireless Communications and Networking Conference (WCNC). IEEE, 2014. http://dx.doi.org/10.1109/wcnc.2014.6952958.
6
Ragaller, Paul A., Alexander Sappok, Jie Qiao, Xiaojin Liu, and Jonathan Aguilar. "Direct Simultaneous Measurement of Particulate Matter and Ammonia Storage on Combined Selective Catalytic Reduction Filter Systems Using Radio Frequency Sensors." In ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9528.
Анотація:
Tightening global emissions regulations are motivating interest in the development and implementation of Selective Catalytic Reduction + Filtration (SCRF) systems, which are designed to reduce the concentration of tailpipe particulate matter (PM) and NOx emissions. These systems allow designers to combine the NOx reduction capability of an SCR with the filtration capability of a particulate filter on a single unit. Practical implementation of these systems requires reliable measurement and diagnosis of their state — both with respect to trapped particulate matter as well as adsorbed ammonia. Currently, these systems rely on a variety of gas sensors, mounted upstream or downstream of the system, that only provide an indirect inference of the operation state. In this study, a single radio frequency (RF) sensor was used to perform simultaneous measurements of soot loading and ammonia inventory on an SCRF. Several SCRF core samples were tested at varying soot and ash loads in a catalyst reactor bench. Soot levels were measured by monitoring changes in the bulk dielectric properties within the catalyst using the sensor, while ammonia levels were determined by feeding selected regions of the RF spectrum into a pretrained generalized regression neural network model. Results show the RF sensor is able to directly measure the instantaneous ammonia inventory, while simultaneously providing soot loading measurements within 0.5 g/L. These results confirm that simultaneous measurements of both the PM and ammonia loading state of an SCRF are possible using a single RF sensor via analysis of specific features in the full RF spectrum. The results indicate significant potential to remove the control barriers typically associated with the implementation of advanced SCRF systems.
7
Berry, David A., Robert James, Todd H. Gardner, and Dushyant Shekhawat. "Systems Analysis of Diesel Based Fuel Cells for Auxiliary Power Units." In ASME 2003 1st International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2003. http://dx.doi.org/10.1115/fuelcell2003-1749.
Анотація:
The near-term commercial success for many fuel cell technologies will rely on their ability to utilize current infrastructure fuels. Several large ready-markets exist for fuel cell systems that utilize middle distillate petroleum fractions like diesel fuel. One particular application is diesel-based auxiliary power units (APU). Unfortunately, very little research and development has been devoted to this application. Ongoing research at the National Energy Technology Laboratory (NETL) and other organizations is trying to address this need. In order for a fuel cell to utilize diesel fuel, it must be reformed into a synthesis gas containing primarily hydrogen, carbon monoxide, carbon dioxide, steam and possibly methane. Because catalytic reforming of hydrocarbon fuels is conducted at the same relative operating temperatures of technologies like solid oxide fuel cells (800–1000°C) a high degree of thermal integration is possible. Unfortunately, carbon deposition and sulfur poisoning of catalysts in the reformer and fuel cell make system operation potentially complicated and costly. To help understand and quantify the impact of these issues on technology development and component, a number of systems analysis was conducted for a diesel-based fuel cell system. One particular system based on a hybrid combustor/reformer concept allowed for excellent utilization of available heat from the fuel cell and yielded an overall fuel to electric conversion efficiency of nearly 50%. This paper discusses its salient features and compares its characteristics to other possible system configurations.
8
Hofmann, Klaus P. "Visual process in retinal photoreceptors: analysis by intrinsic light scattering signals." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.wd1.
Анотація:
The rod photoreceptor of the retina is a quantum detector whose physiological function in physically unfavorable conditions (body temperature, salt solution) is made possible by specific protein interactions. Photon energy is stored by the receptor protein rhodopsin (R) in a structurally transformed state. Activated R interacts with transducin (a G-protein or guanine nucleotide binding protein). This catalyses binding to G of energy-rich nucleotide which in turn releases G in an activated form. Absorption of one photon leads to the activation of 1000 G in 1 s. Analogous relay systems are found from bacteria to man. Intrinsic physical properties of the rhodopsin G-protein system allow photometric studies in situ and in real time. Activation of R and interaction with G are measurable by absorption spectrophotometry. Activation of G is measurable by light scattering (LS) changes (signals) arising from the shift of the G-protein mass during activation. A continuous transretinal, near infrared LS probing beam affords direct monitoring of G-activation induced by visual stimuli. These optical techniques, combined with biochemical and physiological approaches, have been used to study the sites of R-G interaction and the thermodynamics of the G-relay in situ. G-activation is not modulated by previous illumination, indicating a remarkable constancy of the R-G amplification step in the visual transduction pathway.
9
Meierjurgen, Kenneth, Brian Harries, Marc Compere, and Yan Tang. "Sensorless Selective Catalytic Reduction Using Artificial Neural Networks for Emissions Prediction With Fuzzy Logic Control." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65301.
Анотація:
The transportation industry is a major contributor to the increase of greenhouse gasses present in the atmosphere. With the number of automobiles increasing every year, the U.S. government has implemented several regulations to reduce the environmental impact of the transportation industry. The most recent regulations increase the Corporate Average Fuel Economy (CAFÉ) to over 50mpg by 2025. These increased fuel economy standards will save consumers money, reduce dependence on foreign oil and cut GHG emissions in half (1). In order to comply with these regulations and reduce GHG emissions, automakers are improving powertrain efficiency and diversifying their fuel sources. One way automakers are improving fleet fuel economy is by offering more efficient Compression Iginition (CI) engines. Compression ignition engines can have a 10% improvement in peak efficiency over a Spark Ignition (SI) Engine. Although CI engines have higher efficiencies, they also have higher Nitrous Oxide (NOx) emissions. One of the most effective methods for reducing NOx emissions is a Selective Catalytic Reduction (SCR) system. Current methods for reducing NOx emissions using SCR rely on two NOx sensors for close loop control. These sensors add substantial costs to the production exhaust after treatment systems. This paper presents an intelligent control technique to achieve accurate prediction of NOx emissions and closed loop control without the use of expensive on board sensors. Simulation models were created to validate two artificial neural networks that aim to replace the upstream and downstream NOx sensors. The upstream neural network was trained using dynamometer data from a General Motors 1.3l turbo diesel engine. This neural network represented NOx emissions as a function of engine speed and throttle position. The downstream ANN was created using a nonlinear statespace plant model that simulates the catalyst NOx and nh3 reaction. To control the nh3 injection into the catalyst, a Fuzzy Logic Controller (FLC) was implemented. The FLC controller had two inputs: the error function calculated from the output NOx and a predetermined NOx target as well as the predicted surface coverage from the nh3 reaction. The results from steady state and drive cycle simulations are shown. The work presented in this paper serves as a proof of concept for the sensorless SCR system that was developed as part of ERAU’s entry in EcoCAR2: Plugging Into the Future. The simulations were conducted as part of year 1 of the EcoCAR2 competition and will be further developed during years 2 and 3 on ERAU’s Series Plug-in Hybrid Electric Vehicle.
10
Azeredo, Bruno, Keng Hsu, and Placid Ferreira. "Direct Electrochemical Imprinting of Sinusoidal Linear Gratings Into Silicon." In ASME 2016 11th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/msec2016-8835.
Анотація:
Silicon is an excellent transparent material for building IR micro-optical elements such as holographic and blazed gratings, and curvilinear micro-lenses. Shaping this material in 3D with mirror quality finish and single-digit microscale resolution is challenging due to its brittleness and high-melting point. To achieve these patterning characteristics, electron-beam grayscale lithography is typically selected to pattern a 2.5D feature onto a resist thin-film. Subsequently, the film features are transferred into the underlying silicon substrate by deep-reactive ion etching (DRIE) [1]. Small variations in the resist thickness lead to large shape distortions and reduced patterning repeatability. Further, the direct-write nature of e-beam lithography provides for slow throughput. Developing an alternative, parallel and scalable method to nanopatterning silicon with 2.5D geometrical control may impact emerging areas such as the design of sub-wavelength photonic and micro-optic elements for silicon photonics applications. Micro and nanoscale patterning of inorganic semiconductors (e.g. Silicon) requires traditional micromachining processes such as plasma-assisted etching (e.g. DRIE) and wet-etching (e.g. KOH etching). Neither of the aforementioned processes offer the capability to control the geometry in 3D with resolution in the nanoscale range. Thus, it is desirable to develop a low-temperature, low-stress and ambient approach to nanostructuring silicon in 3D. Wet etching approaches are good candidates for achieving such goal because they bypass the need for high-temperature processing and stressing materials beyond the elastic limit. Yet, they still rely on lithographical steps and offer limited sidewall control, restricting the scope of features it can produce. In recent literature, catalyst-based wet etching processes such as metal-assisted chemical etching (MACE) have been shown to pattern high-aspect ratio structures in semiconductors [2–3]. Some researchers have achieved control over the etch profile and etching direction, generating a limited set of interesting 3D objects [4–6]. The degrees of freedom in MACE patterning are still highly constrained due to limited control of the catalyst motion. Additionally, thin-film based MACE relies on intermediate 2D masking steps to pattern the catalyst which are often lithographical. Thus, this indirect approach to patterning silicon increases lead time and processing costs. In this paper, Mac-imprint, a direct imprint configuration of MACE, is introduced to overcome these fundamental barriers. It relies on the use of a catalytic stamp immersed in the etchant and brought against a silicon chip to selectively dissolve it at contact points. Stamps can be reused multiple times to pattern substrates with lifetimes that are dependent solely on its chemical and mechanical degradation. This process is inherently non-lithographic and occurs at room temperature. As a demonstration of its high-resolution capabilities, silicon wafers were patterned with a sinusoidal wave whose pitch and amplitude were 1 μm and 250 nm, respectively. The patterned surface RMS error from the ideal surface was measured to be 13 nm. The key drawback of this approach is the generation of porous defects near the vicinity of the contact interface between stamp and substrate. Its spatial distribution is qualitatively discussed in the context of the diffusion model of MACE [7].
Звіти організацій з теми "Relay catalysis":
1
Drayton, Paul, Jeffrey Panek, Tom McGrath, and James McCarthy. PR-312-12206-R01 FTIR Formaldehyde Measurement at Turbine NESHAP and Ambient Levels. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 2016. http://dx.doi.org/10.55274/r0011014.
Анотація:
Since formaldehyde is ubiquitous (e.g., naturally formed through atmospheric chemistry even if not directly emitted), there is also the potential that atmospheric levels and atmospheric chemistry are not adequately understood.� That avenue of investigation may provide important information that could be important in assessing formaldehyde health risk, source contribution, and ultimately regulatory criteria for gas-fired combustion sources.� In 2002 and 2003, the pipeline industry conducted turbine formaldehyde testing using refined FTIR methods and a dedicated measurement system, which indicated exhaust formaldehyde below 100 ppb and near the method detection limit.� Anecdotal data from that test program showed ambient levels similar to turbine exhaust in some cases.� For example, during the industry test program, a serendipitous finding observed that ambient formaldehyde concentrations varied and were independent of turbine operation.� Instead, naturally occurring emissions from an adjacent corn field appeared to spike the ambient concentration to levels higher than formaldehyde exhaust levels, depending on whether there was direct sunlight or shading from a cloud (i.e., due to �naturally occurring� formaldehyde from vegetation and/or other organics and ambient photochemistry that forms formaldehyde).� Evidence of �high� ambient formaldehyde levels (relative to turbine exhaust) would be a powerful counterargument to restrictive formaldehyde regulations. If ambient levels are similar to (or higher than) in-stack formaldehyde for turbines, then a NESHAP requiring catalytic control of turbine formaldehyde results in a significant burden without� environmental benefit, while also negatively impacting turbine efficiency and environmental impacts associated with catalyst construction, installation, operation, cleaning, and disposal.� Similarly, if ambient formaldehyde is significantly higher (in at least some circumstances) than currently available ambient data suggests, there could be implications for perceived formaldehyde risk and the basis, need for, and stringency of formaldehyde reductions from turbines or other combustion sources.� In a more far-reaching impact, ambient FTIR data could provide additional insights on atmospheric reactions that not only impact formaldehyde issues, but also ozone (and NOx control issues) because of the importance of formaldehyde and hydrocarbon chemistry in ambient ozone formation. These determinations are challenged by the ability to accurately measure formaldehyde at levels less than 100 parts per billion (ppbv).� Ambient measurements rely on �batch methods� subject to error (due to the inherent instability and reactivity of formaldehyde), and those methods do not provide real-time continuous results.� Extractive Fourier Transform Infrared (FTIR) methods were developed for combustion exhaust formaldehyde measurement, but measuring the ultra-low levels from turbines, commensurate with the NESHAP standard of 90 ppb, is challenging.� This project was intended assess ambient formaldehyde levels as compared to the NESHAP standard and acquire additional ambient measurement data using FTIR testing.
2
Katzir, Nurit, James Giovannoni, and Joseph Burger. Genomic approach to the improvement of fruit quality in melon (Cucumis melo) and related cucurbit crops. United States Department of Agriculture, June 2006. http://dx.doi.org/10.32747/2006.7587224.bard.
Анотація:
Fruit quality is determined by numerous genetic traits that affect taste, aroma, texture, pigmentation, nutritional value and duration of shelf-life. The molecular basis of many of these important traits is poorly understood and it’s understanding offers an excellent opportunity for adding value to agricultural products. Improvement of melon fruit quality was the primary goal of the project. The original objectives of the project were: The isolation of a minimum of 1000 fruit specific ESTs. The development of a microarray of melon fruit ESTs. The analysis of gene expression in melon using melon and tomato fruit enriched microarrays. A comprehensive study of fruit gene expression of the major cucurbit crops. In our current project we have focused on the development of genomics tools for the enhancement of melon research with an emphasis on fruit, specifically the first public melon EST collection. We have also developed a database to relay this information to the research community and developed a publicly available microarray. The release of this information was one of the catalysts for the establishment of the International Cucurbit Genomic Initiative (ICuGI, Barcelona, Spain, July 2005) aimed at collecting and generating up to 100,000 melon EST sequences in 2006, leveraging a significant expansion of melon genomic resources. A total of 1000 ESTs were promised under the original proposal (Objective 1). Non-subtracted mature fruit and young fruit flesh of a climacteric variety in addition to a non-climacteric variety resulted in the majority of additional EST sequences for a total of 4800 attempted reads. 3731 high quality sequences from independent ESTs were assembled, representing 2,467 melon unigenes (1,873 singletons, 594 contigs). In comparison, as of June 2004, a total of 170 melon mRNA sequences had been deposited in GENBANK. The current project has thus resulted in nearly five- fold the number of ESTs promised and ca. 15-fold increase in the depth of publicly available melon gene sequences. All of these sequences have been deposited in GENBANK and are also available and searchable via multiple approaches in the public database (http://melon.bti.cornell.edu). Our database was selected as the central location for presentation of public melon EST data of the International Cucurbit Genomic Initiative. With the available unigenes we recently constructed a microarray, which was successfully applied in hybridizations (planned public release by August 2006). Current gene expression analyses focus on fruit development and on comparative studies between climacteric and non-climacteric melons. Earlier, expression profiling was conducted using macroarrays developed at the preliminary stage of the project. This analysis replaced the study of tomato microarray following the recommendations of the reviewers and the panel of the original project. Comparative study between melon and other cucurbit crops have begun, mainly with watermelon, in collaboration with Dr. Amnon Levi (USDA-ARS). In conclusion, all four objectives have been addressed and achieved. In the continuation project that have been approved we plan to apply the genomic tools developed here to achieve detailed functional analyses of genes associated with major metabolic pathway.