Academic literature on the topic 'Bond exchange reaction'
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Journal articles on the topic "Bond exchange reaction"
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Zhao, Dongbing, Wen-Tao Zhao, and Fang Gao. "Recent Progress in σ-Bond Cross-Exchange Reactions to Access Diverse Silacycles." Synlett 29, no. 20 (August 30, 2018): 2595–600. http://dx.doi.org/10.1055/s-0037-1610266.
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The σ-bond cross-exchange reaction, which involves cleavage and subsequent exchange between different nonpolar σ-bonds, constitutes an attractive protocol for rapid access to organic skeletons with 100% atom economy. Herein, we give a brief summary of recent achievements in this approach for the synthesis of diverse silacycles, highlighting our recent advances in the first intermolecular σ-bond exchange between C–C bonds of cyclopropenones and C–Si bonds of (benzo)silacyclobutanes.1 Introduction2 σ-Bond Exchange-Reaction of Benzocyclobutanones to Silacycles3 σ-Bond Exchange-Reaction of Ethyl Cyclopropylideneacetates to Silacycles4 σ-Bond Exchange-Reaction of Cyclopropenones to Silacycles5 Conclusion
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Arisawa, Mieko, Tomoki Yamada, Saori Tanii, Yuta Kawada, Hisako Hashimoto, and Masahiko Yamaguchi. "Rhodium-catalyzed P–P bond exchange reaction of diphosphine disulfides." Chemical Communications 52, no. 93 (2016): 13580–83. http://dx.doi.org/10.1039/c6cc07302f.
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A rhodium-catalyzed exchange reaction of diphosphine disulfides, a diphosphine oxide, and a diphosphine is developed. Various symmetric diphosphine disulfides containing alkyl and phenyl groups are exchanged.
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Yang, Xichuan, Mikael Kritikos, Björn Åkermark, and Licheng Sun. "Axial ligand exchange reaction on ruthenium phthalocyanines." Journal of Porphyrins and Phthalocyanines 09, no. 04 (April 2005): 248–55. http://dx.doi.org/10.1142/s1088424605000319.
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Bis(4-methylpyridine)phthalocyaninato ruthenium(II) has been synthesized. It was proved by single-crystal X-ray diffraction that the central Ru(II) atom is bonded to six N atoms in an elongated octahedral configuration, and the axial ligands have a significantly longer Ru - N bond distance, 2.101(4) Å, than the independent pyrrol Ru - N bond, 1.99 Å. Therefore, the axial ligands can be exchanged by other ligands. The ligand exchange reactions with diethyl pyridyl-4-phosphonate and diethyl pyridylmethyl-4-phosphonate were studied in high boiling-point solvents at elevated temperatures, ca 160 °C. Mono-ligand as well as double-ligand replaced complexes were obtained. The complexes have been isolated by column chromatography. These complexes have potential applications, such as in dye sensitized solar cells.
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Sutrisno, Sutrisno, and Rahayu Ningtiyas. "DERERMINANTS OF ISLAMIC BOND MARKET REACTION Empirical Study of Islamic Bond in Indonesia." Jurnal Apresiasi Ekonomi 9, no. 2 (May 31, 2021): 152–58. http://dx.doi.org/10.31846/jae.v9i2.379.
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The main objective of this study is to examine several factors that cause islamic bonds market reaction as measured by cumulative abnormal return. The factors that are believed to be the determinants of islamic bond market reaction are the value of islamic bonds issuance, islamic bond rating, age of islamic bonds and size of the islamic bond issuing company. The population in this study are companies that issue Islamic bonds and are listed on the Indonesia Stock Exchange with a four-year observation period (2015-2018). The sample selection in this study uses purposive sampling based on certain criteria. In sample selection 36 Islamic bonds were obtained as samples. This study uses secondary data where the data is obtained from the annual report and the website of the issuing company. To test the hypothesis, using a multiple regression analysis tool with a significance level of 0.05. The results showed that the value of Islamic bonds issuance and rating of Islamic bonds issuance had a positive effect on market reaction. While the age of islamic bonds and the firm size have no effect on the reaction of the islamic bond market
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Ryabov, Alexander D. "The Exchange of Cyclometalated Ligands." Molecules 26, no. 1 (January 3, 2021): 210. http://dx.doi.org/10.3390/molecules26010210.
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Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a cyclometalated compound and an incoming ligand that replaces a previously cyclometalated ligand to form a new metalacycle: + H-C*~Z ⇄ + H-C~Y. Originally discovered for PdII complexes with Y/Z = N, P, S, the exchange appeared to be a mechanistically challenging, simple, and convenient routine for the synthesis of cyclopalladated complexes. Over four decades it was expanded to cyclometalated derivatives of platinum, ruthenium, manganese, rhodium, and iridium. The exchange, which is also questionably referred to as transcyclometalation, offers attractive synthetic possibilities and assists in disclosing key mechanistic pathways associated with the C–H bond activation by transition metal complexes and C–M bond cleavage. Both synthetic and mechanistic aspects of the exchange are reviewed and discussed.
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LI, PING, XIAOYAN XIE, YUXIANG BU, WEIHUA WANG, NANA WANG, JUNYOU SHI, and ZHAOXIA MOU. "THEORETICAL STUDIES ON THE COUPLING INTERACTIONS AND SELF-EXCHANGE REACTION MECHANISMS IN THE COMPLEXES OF NO WITH ONH AND NOH." Journal of Theoretical and Computational Chemistry 07, no. 03 (June 2008): 435–46. http://dx.doi.org/10.1142/s0219633608003848.
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The coupling interactions and self-exchange reaction mechanisms between NO and ONH (NOH) have been systematically investigated at the B3LYP/6-311++G** level of theory. All the equilibrium complexes are characterized by the intermolecular H-bonds and co-planar geometries. The cisoid NOH/ON species is the most stable one among all the complexes considered due to the formation of an N – N bond. Moreover, all the cisoid complexes are found to be more stable than the corresponding transoid ones. The origin of the blueshifts occurring in the selected complexes has been explored, employing the natural bond orbital (NBO) calculations. Additionally, the proton transfer mechanisms for the self-exchange reactions have been proposed, i.e. they can proceed via the three-center proton-coupled electron transfer or five-center cyclic proton-coupled electron transfer mechanism.
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DENG, XIN, LIN GE, and XUAN WU. "SPILLOVER EFFECT OF THE FEDERAL RESERVE’S FORWARD GUIDANCE ON CHINA’S FINANCIAL MARKETS: FROM MECHANISM ANALYSIS TO EMPIRICAL TEST." Singapore Economic Review 67, no. 02 (October 7, 2021): 603–34. http://dx.doi.org/10.1142/s0217590821500612.
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This study analyzed the channels responsible for the spillover effect of the US Federal Reserve’s (Fed’s) forward guidance on China’s financial markets with an event study and EGARCH model with data collected over the past decade. The Fed’s forward guidance affects China’s foreign exchange, bond, stock and money markets. In the three trading days before and after the event, China’s foreign exchange market had an instantaneous reaction, the bond and stock market had lagged reactions, and the money market reaction lasted for the full event window. The Fed’s forward guidance on China’s financial market differs based on the Fed’s monetary policy, guidance type and whether the guidance content is adjusted or not.
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Harcourt, Richard D., and Rickie Ng. "Valence bond representation for the hydrogen atom exchange reaction." Journal of Physical Chemistry 97, no. 47 (November 1993): 12210–14. http://dx.doi.org/10.1021/j100149a019.
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Casey, W. H. "A view of reactions at mineral surfaces from the aqueous phase." Mineralogical Magazine 65, no. 3 (June 2001): 323–37. http://dx.doi.org/10.1180/002646101300119439.
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AbstractThe processes by which a metal–oxygen bond dissociates in aqueous complexes are discussed and the reactions related to more complicated pathways of mineral dissolution. The dissolution of oxide minerals, and in fact many other classes of surface reactions, can be viewed as a ligand-exchange reaction because the bridging oxygens that link the metal to the mineral are progressively replaced by non-bridging functional groups. These ligand-exchange reactions are accelerated by protonations, hydroxylations and ligand substitutions that modify the lability of surface oxygens, but always at specific sites. Molecular information is important because reactions at some sites retard rates while reaction at other sites enhance them. Virtually all of the important variables that affect these reaction rates are local.
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Lutfiyah, Lailatul, and Mu’minatus Sholichah. "Pengaruh Nilai Sukuk Dan Risiko Sukuk Terhadap Reaksi Pasar Modal." Journal of Culture Accounting and Auditing 1, no. 1 (July 14, 2022): 107. http://dx.doi.org/10.30587/jcaa.v1i1.4233.
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This study aims to analyze the effect of Sharia Bond Issuance Value (sukuk), Shariah Bond Risk (sukuk) on Capital Market Reaction. This study uses a sample of companies that issue sukuk listed on the Indonesia Stock Exchange for the period 2017 – 2020. This research is a quantitative type that uses secondary data types with data collection methods carried out by accessing reports conducted by the Indonesia Stock Exchange Website, Yahoo Finance and Investing.com. The data analysis technique used in this research is multiple linear regression analysis. The test results show that only the sukuk value variable has a positive and significant effect on capital market reactions. Meanwhile, the risk of sukuk is stated to have a negative and insignificant effect on the reaction of the capital market.
Dissertations / Theses on the topic "Bond exchange reaction"
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Lippert, Joe Mark. "An examination of the price reaction to the announcement of bond issues by Johannesburg Stock Exchange listed companies on the Bond Exchange of South Africa." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/11318.
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Includes abstract.Includes bibliographical references (leaves 80-84).
This paper examines the effect of straight debt announcements on the daily stock returns of Johannesburg Stock Exchange (JSE) listed companies, on The Bond Exchange of South Africa (BESA), during the period 2000 to 2008. The study is an event study that uses the market model to generate expected returns. The average abnormal returns are standardised by their time series standard errors of regression and tested for significance by the t-test. The evidence indicates that the null hypothesis should not be rejected. Furthermore, the study is examined within the context of contemporary capital structure theory.
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Lik, Artur [Verfasser], Holger [Akademischer Betreuer] Helten, and Markus [Akademischer Betreuer] Albrecht. "Thienyl- and furylborane oligomers, polymers, and macrocycles - dvelopment of a catalytic Si/B exchange reaction as a novel B-C bond formation method / Artur Lik ; Holger Helten, Markus Albrecht." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/117181867X/34.
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Chen, Szu-Lin. "An empirical potential for hydrogen bond energies determination of the orientation of anthracene molecules in the unit cell by means of a refractivity method: some ab initio calculations involving acetonitrile exchange reaction." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/76509.
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Topic I
An empirical potential for calculating hydrogen bonding energies is developed for systems of the type A-H--B, where A and/or B is oxygen or nitrogen. Point charge and van der Waals interaction are included in the potential. The parameters of the potential were optimized by means of a simplex algorithm within a range of A-B distances from 2.8 A through 5.0 A. The root mean square deviation between the empirical potential and the ab initio results of 216 configurations of (H₂O)₂, (NH₃)₂ and NH₃•H₂O is 0.9 kcal/mol and 0.5 kcal/mol for 61 configurations of methanol dimers. Applications of the potential to water dimers, ammonia dimers, their mixed dimers, water oligomers and ice-h as well as the β form of the methanol crystal show that the potential yields reasonable results compared to those computed by "ab initio" methods using 6-31G* basis sets. The potential is compatible with MM2 program. It is simpler than earlier potentials in that neither dipoles nor Morse potentials are involved. It should be superior to the empirical potentials developed by Jorgensen that used STO-3G ab initio calculated results as the standards. The potential might be useful for estimation of hydrogen bond energies in a local part of a large molecule to avoid the prohibitive expense of ab initio calculation.
Topic II
The monoclinic anthracene crystal is used as an example to demonstrate the feasibility of optimizing the orientation of molecules in the unit cell by matching calculated and experimental refractivity ellipsoids using a simplex algorithm. The calculated refractivity ellipsoid is determined by use of an empirical formula using bond directional polarizabilities. Optimization of the molecular orientations to provide the best fit to the experimental ellipsoid starting from several assumed orientations results in fits for which the maximum deviation from the experimental molecular orientation was no more than 10 degrees. The method can be applied to other monoclinic molecular crystals directly and could be extended to other crystal systems with anisotropic optical properties.
Topic III
Three mechanisms (Walden inversion, addition-rearrangement-elimination and proton 1,3 shift mechanisms) of the following reaction were suggested by Jay et al. and Andrade et al. respectively.
CH₃CN + C⃰N- = CH₃C⃰N + CN-.
The mechanism of Walden inversion was determined to be the least likely one based on Andrade's MNDO results. Our calculations, based on 3-21G and 4-31G results, show the contrary result that the Walden inversion is the most likely mechanism among the three considered. However, solvation effects were neglected in the calculations and these effects could play a major role in the choice of mechanisms. Simple calculations based on Boltzmann distribution of precursor concentrations and the Arrhenius law show that Walden inversion predominates over Jay's addition-elimination-rearrangement mechanism even when MNDO energy levels were used. Estimated orders of magnitude for the rate ratios were determined.Ph. D.
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Castro, Cabrera Isis. "Epoxy vitrimer materials based on disulfide exchange chemistry : experimental study and modeling of the stress relaxation - application to composites reinforced by nanofibrillated cellulose." Electronic Thesis or Diss., Toulon, 2021. http://www.theses.fr/2021TOUL0010.
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Les résines époxy thermodurcissables ont attiré l'attention de nombreuses industries en raison de leur polyvalence, des adhésifs aux matériaux composites. Malgré leur versatilité, le recyclage, la durabilité et développement durable de ces thermodurs majoritairement pétrosourcés limitent leur utilisation. Des réseaux adaptables covalents (CAN) comme les vitrimères peuvent offrir une solution pour faire face à ces problèmes. Le système époxy DGEBA‒4-APDS, basé sur la chimie d'échange de disulfures, a montré des propriétés de recyclabilité, mais son comportement vitrimère n'a pas été encore complètement vérifié. Dans le présent travail, toutes les propriétés propres aux vitrimères sont étudiées afin de s’assurer du caractère vitrimère de ce matériau. De façon intéressante, la température d’échange des liaisons réversibles propre aux vitrimères (Tv) est proche de la transition vitreuse du matériau (Tg). Il en découle que sa relaxation, qui s’opère légèrement au-dessus de sa Tg, est influencée à la fois par les réactions d'échange des liaisons réversibles et par la relaxation du polymère en lui-même. De ce fait, il est proposé un modèle adapté de relaxation des contraintes qui prend en compte ces deux phénomènes. Ce modèle rhéologique a permis également d'évaluer la relaxation de cette matrice époxy-vitrimère renforcée par des nanofibrilles de cellulose (NFC). Ce composite vitrimère à base de NFC est un matériau léger durable et présentant des propriétés mécaniques similaires à celles des réseaux covalents non-adaptables. Une étude initiale pour augmenter la durabilité de ce vitrimère époxy a consisté à modifier la surface de la NFC par un agent de couplage glycidoxy silane. Une méthode simple de greffage des NFC est proposée, et la caractérisation du réseau silane entourant les NFC a été réaliséeEpoxy thermoset resins have drawn the attention of many industries due to their versatility, from adhesives to polymer composites. Yet, the re-processability, sustainability, and durability of resins limit their use. The covalent adaptable networks (CANs) like vitrimers can afford a solution to overcome these issues. The epoxy resin, DGEBA‒4-APDS, based on the disulfide exchange chemistry, has shown re-processability properties, but its vitrimer properties have not been fully verified. In the present work, all the vitrimer properties are reviewed to classify it as a vitrimer material. Interestingly, the vitrimer exchange operating temperature (Tv) is close to its glass transition (Tg). So, its relaxation behavior, slightly above Tg, is influenced by the bond exchange reactions and the segmental relaxations of the network. Thus, an adapted stress relaxation model that considers both relaxation phenomena is proposed. This developed rheological model leads to evaluate the epoxy vitrimer matrix reinforced by nano fibrillated cellulose (NFC). The vitrimer composite made with NFC performs a sustainable lightweight material and exhibits mechanical properties similar to non-covalent adaptable networks. A preliminary study to increase material durability has consisted in the NFC surface modification by glycidoxy silane coupling agent. A simple NFC grafting method is proposed, and the surface characterization of the silane network surrounding the NFC is well-explored
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Roettger, Max. "Associative exchange reactions of boron or nitrogen containing bonds and design of vitrimers." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066608/document.
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Dans l'optique de préparer des vitrimères à partir des thermoplastiques communément utilisés, tels le PMMA et le PS, des réactions d'échange dynamiques reposant les liens imine et esters boroniques ont été étudiées. Des paramètres importants comme la constante de dissociation de certaines molécules, la constante de vitesse et l'énergie d'activation ont été mesurées. Des monomères porteurs de liaisons échangeables ont été synthétisés et polymérisés. Des vitrimères, avec des liaisons C-C dans la chaine principale, ont été créés par différentes stratégies (PMMA et PS). Ces matériaux sont réticulés et insolubles avec un plateau caoutchouteux mais également façonnables et recyclables par moulage par compression ou par injection. Ces vitrimères peuvent relaxer les contraintes et couler à une température supérieure à celle de leur transition vitreuse. Des viscosités de 105-107 Pa.s ont été estimées pour les vitrimères PMMA reposant sur la chimie des esters boroniques. Des tests de traction montrent que leurs propriétés mécaniques de ces matériaux ne subissent pas de baisse significative après plusieurs cycles de recyclage par moulage par injection. Même après plusieurs cycles de moulage, les vitrimères basés sur la chimie des esters boroniques peuvent être complètement dé-réticulés, signe de leur stabilité à haute température lors du moulage. Ces vitrimères ont une résistance supérieure dans les conditions "d'environmental stress cracking" comme des réseaux polymères conventionnelsWith the aim to generate vitrimers from commonly used thermoplastics with carbon-carbon based backbones, such as PMMA and PS, dynamic covalent exchange reactions relying on Schiff’s bases and boronic esters were investigated. Two different approaches, i.e. crosslinking in solution or in extrusion, were used. These materials are processable via extrusion, compression and injection molding like their thermoplastic counterparts. The crosslinked nature of these systems was confirmed by solubility tests and DMA. Rheological measurements revealed the vitrimers ability to flow and viscosities between 105-107 Pa.s for boronic ester based PMMA vitrimers were measured. Consecutive tensile testing/reprocessing sequences proved the full recyclability of these vitrimers, and selective cleavage of the vitrimer networks followed by precise chemical analyses showed the thermal and chemical stabilities of vitrimers relying on boronic ester bonds. The stress cracking resistance of these vitrimers was significantly higher than that of parent thermoplastics, as can be expected for crosslinked systems
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Elam, Latansa Izzata Dien <1995>. "Stock market reaction to green bond issuances: an empirical study on firms listed on Asian stock exchanges." Master's Degree Thesis, Università Ca' Foscari Venezia, 2020. http://hdl.handle.net/10579/17625.
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Among institutional, wealth, and retail investors, Environmental, Social, and Governance (ESG) investments are growing significantly. One example of ESG investments are green bonds. Green bonds can be defined as fixed income securities that finance investments with environmental or climate-related benefits. In recent years, the demand for green bonds has grown rapidly. The green bond issuances occurred across all continents, with a growing number of emerging market issuances. This substantial growth of the market and its increased importance in terms of decarbonisation, combined with the limited existing research on green bonds, makes it an appealing subject for an event study. Furthermore, studies on the Asian market exclusively is limited. With the Asian market being the fastgrowth market for green bonds, it would be interesting to analyse how the market reacts to such issuances. For this reason, this thesis wants to analyse stock market reaction to green bond issuances by an empirical study on firms listed on Asian stock exchanges for the year 2014-2019.
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Gates, Richard J. "Dynamics of the Solvent Exchange Reaction of Weakly Bound Organic Solvents to Group 6 Transition Metal Carbonyls and the Molybdenum Hexacarbonyl Mediated Pauson-Khand Reaction." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/2936.
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Many organometallic reactions are solvent-dependent, suggesting solvent molecules interact with reaction intermediates. Studies of the solvent exchange reaction of group 6 transition metal carbonyls with moderately binding ligands have provided insight into these interactions, however, studies of the mechanism for this reaction with weakly binding ligands have not been performed. Experiments were conducted on the nanosecond time scale in methylcyclohexane over the temperature range of 4 to 44 °C using Step Scan FTIR (SS FTIR) spectroscopy with weakly binding ligands benzene and mesitylene. Upon photolysis of the metal hexacarbonyls, the kinetically favored product (M(CO)5(solv)), decays following pseudo-first-order kinetics to the thermodynamical favored product, M(CO)5(L). The decay is fit using a single exponential decay with a single exponential instrument response function, time zero and an offset. An Arrhenius plot yielded activation energies of 23.7 kJ/mol (M = Mo, L = benzene), 35.1 kJ/mol (M = W, L = benzene) and 29.8 kJ/mol (M = Mo, L = mesitylene). DFT calculations using NWCHEM gave binding energies of 45.8 and 54.3 kJ mol-1 for Mo(CO)5C6H12 and W(CO)5C6H12. The experimental and computational results suggest the exchange mechanism proceeds through an associative pathway, were slightly negative values of the entropy of reaction denote that the transition state has greater metal solvent bond breaking character then the more moderately binding ligands in the literature. Density Functional theory was used to calculate C-O vibrational frequencies of metal carbonyl complexes measured in our work and other complexes from the literature, with density functionals B3LYP, M06 and M06-L. Measured and computational frequencies were compared to obtain both an overall vibrational shift and a scaling factor. Scaling factors were found to be 0.9519±0.0095 for B3LYP, 0.9429 ± 0.0087 for M06 and 0.9565 ± 0.0095 for M06-L with overall shifts of 102 ± 16, 121 ± 15, 93 ± 17 cm-1, respectively. The molybdenum mediated Pauson-Khand reaction, a [2+2+1] cyclo-addition begins very similarly to the solvent exchange reaction on molybdenum. The initial product, the solvated complex, decays away with pseudo-first-order kinetics as the solvent is replaced by the C-C triple bond in 2-(2-propen-1-yl)-2-(2-propyn-1-yl)-,1,3-diethyl ester. An Arrhenius plot over the temperature range of -8 to 20° C yielded an energy of activation of 15.6 kJ/mol.
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Mohan, J. K. "Synthetic studies towards taxoids and reaction of diazoester with carbon-carbon /heteroatom bonds catalyzed by transition metal exchanged clay." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1998. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3408.
Full textBooks on the topic "Bond exchange reaction"
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Bonn, Moritz J. Atomic energy, fast breeder reactor: Agreements between the United States of America and the Federal Republic of Germany, extending the agreement of June 8, 1976, effected by exchange of letters signed at Bonn and Washington August 26 and October 7, 1986 and exchange of letters, signed at Bonnand Washington, December 15 and 31, 1987. Washington, D.C: Dept. of State, 1996.
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Boero, Mauro, and Masaru Tateno. Quantum-theoretical approaches to proteins and nucleic acids. Edited by A. V. Narlikar and Y. Y. Fu. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199533046.013.17.
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This article describes quantum methods used to study proteins and nucleic acids: Hartree–Fock all-electron approaches, density-functional theory approaches, and hybrid quantum-mechanics/molecular-mechanics approaches. In addition to an analysis of the electronic structure, quantum-mechanical approaches for simulating proteins and nucleic acids can elucidate the cleavage and formation of chemical bonds in biochemical reactions. This presents a computational challenge, and a number of methods have been proposed to overcome this difficulty, including enhanced temperature methods such as high-temperature molecular dynamics, parallel tempering and replica exchange. Alternative methods not relying on the knowledge a priori of the final products make use of biasing potentials to push the initial system away from its local minimum and to enhance the sampling of the free-energy landscape. This article considers two of these biasing techniques, namely Blue Moon and metadynamics.
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Pollock, Rob. Total hip replacement: modes of failure. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199550647.003.007010.
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♦ Total hip replacements (THRs) may fail in various ways. They may become infected, they may be subject to aseptic loosening, they may dislocate, or a periprosthetic fracture may occur. The patient with a failed THR must be thoroughly assessed before treatment is contemplated♦ Infection may be acute or chronic. Assessment involves clinical assessment, plain radiographs, blood tests (C-reactive protein and erythrocyte sedimentation rate), hip aspiration, and, sometimes, nuclear medicine. The acutely infected hip may be treated with one-stage revision. This involves thorough lavage, debridement, and exchange of all modular components as well as long-term antibiotic therapy. The gold standard of treatment for a chronically infected THR is a two-stage revision. Success rates of 80–90% can be expected♦ Aseptic loosening typically occurs at the cement bone interface in hips where a metal-on-polyethylene bearing couple has been used. Bone resorption takes place as a result of an inflammatory response to small wear particles. After infection has been excluded the treatment of choice is a single-stage revision♦ Dislocation may be the result of patient factors, implant factors, or poor surgical technique. It is imperative for the clinician to minimize the risk by selecting patients carefully, using the correct combination of implants and performing surgery accurately♦ The management of periprosthetic fractures depends on how well the implants are fixed and quality of bone stock. Treatment ranges from simple fixation of the fracture through to revision augmented with strut allograft.
Book chapters on the topic "Bond exchange reaction"
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Hendry, Robin Findlay. "Mechanisms in Chemistry." In History, Philosophy and Theory of the Life Sciences, 139–60. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-46917-6_7.
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AbstractMechanisms are the how of chemical reactions. Substances are individuated by their structures at the molecular scale, so a chemical reaction is just the transformation of reagent structures into product structures. Explaining a chemical reaction must therefore involve different hypotheses about how this might happen: proposing, investigating and sometimes eliminating different possible pathways from reagents to products. One distinctive aspect of mechanisms in chemistry is that they are broken down into a few basic kinds of step involving the breaking and making of bonds between atoms. This is necessary for chemical kinetics, the study of how fast reactions happen, and what affects it. It draws on G.N. Lewis’ identification of the chemical bond as involving shared electrons, which from the 1920s achieved the commensuration of chemistry and physics. The breaking or making of a bond just is the transfer of electrons, so a chemical bond on one side of an equation might be balanced on the other side by the appearance of a corresponding quantity of excess charge. A bond is understood to have been exchanged for a pair of electrons. Since reaction mechanisms rely on identities, doesn’t the establishment of a reaction mechanism explain away the chemical phenomena, showing that they are no more than the movement of charges and masses? In one sense yes: these mechanisms seem to involve a conserved-quantity conception of causation. But in another sense no: the ‘lower-level’ entities can do what they do only when embedded in higher-level organisation or structure. There need be no threat of reduction.
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Klei, Steven R., Kian L. Tan, Jeffrey T. Golden, Cathleen M. Yung, Reema K. Thalji, Kateri A. Ahrendt, Jonathan A. Ellman, T. Don Tilley, and Robert G. Bergman. "C—H Bond Activation by Iridium and Rhodium Complexes: Catalytic Hydrogen—Deuterium Exchange and C—C Bond-Forming Reactions." In ACS Symposium Series, 46–55. Washington, DC: American Chemical Society, 2004. http://dx.doi.org/10.1021/bk-2004-0885.ch002.
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Noorbatcha, I., B. Arifin, and S. M. Zain. "Ab Initio Quantum Chemical Studies of Six-Center Bond Exchange Reactions Among Halogen and Halogen Halide Molecules." In Computational Science – ICCS 2007, 335–38. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-72586-2_48.
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Mega, Tony L., and Robert L. Van Etten. "Oxygen Exchange and Bond Cleavage Reactions of Carbohydrates Studied Using the 180 Isotope Shift in 13C NMR Spectroscopy." In NMR Applications in Biopolymers, 85–93. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4684-5868-8_7.
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Dickson, Ronald S. "The Activation of C—H and C—C Bonds: Dehydrogenation, H/D Exchange and Isomerization Reactions." In Catalysis by Metal Complexes, 8–39. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5267-6_2.
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Hussein Mekni, Nejib Ben, and Noureddine Raouafi. "Organocalcium (Ca-C) σ-bond Containing Compounds." In The Synthetic Methods, Structures, and Properties of the Ca-Cσ Bond Organocalcium Containing Compounds, 20–55. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/9789815040647122010005.
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Compared to other organometallics, the number of organocalcium compounds and their related publications are limited. In this chapter, we grouped different Ca-Cσ-bond containing organocalcium compounds described in the literature, (Alkyl, silyl, cycloalkyl, benzyl, alkenyl, alkynyl, diene, diyne, phenyl, biphenyl, anthracene, halo thiophene and picoline derivatives) with the specificity for each kind of compounds. We discuss the stabilizing factors of structures including: conjugation, hyperconjugation, complexing heteroatom lone pairs and π-bonding electron pairs. The different synthetic processes used to avoid synthetic problems of substrate and calcium source reactivity, intermediate and product stability and solubility, reaction temperature, yields and decomposition reactions of both intermediates and products, as well as the orientation of the reaction sides in some reactions, are also grouped (thiophene and picoline derivatives). The halo aromatic organocalcium compounds are described to be the most stable intermediates, giving the best yields. Some calculations that correlate with experimental results are mentioned. Particular calcium reagents, such as Ca*, CaI2 and particular reactions as well as exchange (transmetalation) reactions are also examined. Some examples of the geometrical structures, which give C-Ca-C bent angles, and bond lengths obtained from X-ray are gathered.
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Kumagai, T., and H. Okuyama. "Direct Observation of Hydrogen-Bond Exchange Reaction in a Water Dimer Using Low-Temperature Scanning Tunneling Microscopy." In Encyclopedia of Interfacial Chemistry, 74–80. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-12-409547-2.14231-3.
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Badwan, Nemer. "Perspective Chapter International Financial Markets and Financial Capital Flows: Forms, Factors and Assessment Tools." In Macroeconomics [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.102572.
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This paper/chapter empirically examines the reaction of international financial markets and financial capital flows across many developing and emerging market economies, with a particular focus on the dynamics of capital flows across emerging market economies. Using daily data from (2000 to 2020) and controlling for a range of local and global macroeconomic and financial factors and global financial crisis, we use a fixed-effects panel approach quantitative and descriptive approach combined to show that emerging markets have been affected more than advanced economies. In particular, emerging economies in Asia and Europe have experienced the strongest impact on stocks, bonds and exchange rates in recent times, as well as sudden and large capital inflows. Our findings suggest that very large fiscal stimulus packages, as well as quantitative easing by central banks, helped restore overall investor confidence by lowering bond yields and boosting stock prices. Our findings also highlight the role that global factors and developments in the world’s leading financial centers play in financial conditions in emerging markets and developing countries. More importantly, the impact of quantitative easing measures related to the global financial crisis by central banks in developed countries.
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Schmickler, Wolfgang. "Phenomenological treatment of electron-transfer reactions." In Interfacial Electrochemistry. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195089325.003.0010.
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Electron-transfer reactions are the simplest class of electrochemical reactions. They play a special role in that every electrochemical reaction involves at least one electron-transfer step. This is even true if the current across the electrochemical interface is carried by ions since, depending on the direction of the current, the ions must either be generated or discharged by an exchange of electrons with the surroundings. In general electron-transfer reactions can be quite complicated, involving breaking or forming of chemical bonds, adsorption of at least one of the redox partners, or the presence of certain catalysts. So far our understanding is limited to the simplest possible case, so-called outersphere electron-transfer reactions, in which from a chemist's point of view nothing happens but the exchange of one electron - as we shall see later, the simultaneous transfer of two or more electrons is highly unlikely. In the course of such a reaction, no bonds are broken or formed, the reactants are not specifically adsorbed, and catalysts play no role. If one of these conditions is not fulfilled, the reaction is said to proceed via an inner-sphere pathway.
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Hinck, A. P., and W. F. Walkenhorst. "NMR and Mutagenesis Investigations of a Model Cis: Trans Peptide tsomerization Reaction: Xaa116-Pro117of Staphylococcal Nuclease and its Role in Protein Stability and Folding." In Biological NMR Spectroscopy. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094688.003.0016.
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The slow rates of peptide bond isomerization in imino acids and the substantial population of the cis peptide bond isomer in Xaa-Pro linkages in peptides were first recognized in NMR studies of proline-containing model compounds (Maia et al., 1971). The important role of this isomerization in protein stability and folding (reviewed by Kim and Baldwin, 1982, 1990; Schmid, 1993) were recognized several years later (Brandts et al., 1975) and the biological relevance of this process was substantiated by the discovery of a ubiquitous enzyme that catalyzes Xaa-Pro peptide bond isomerization (Fischer et al., 1984, 1989; Takahashi et al., 1989). The strict evolutionary conservation of some prolyl residues and the observation that the kinetics of interconversion between alternative functional forms of some systems is consistent with the time scale of proline isomerization suggest that proline isomerization may play a wide role in protein structure and function. Suggestive examples include the sodium pump of Escherichia coli, the disulfide isomerase/thioredoxin class of enzymes, concanavalin A, and bovine prothrornbin fragment I (Brown et al., 1977; Marsh et al, 1979; Dunker, 1982; Brandland Deber, 1986; Langsetmo et al, 1989). NMR spectroscopy is one of the most suitable tools for studying this isomerization reaction. The rates generally are slow on the time scale of NMR chemical shifts but, in favorable cases, are comparable to longitudinal relaxation rates so that the isomerization process can be investigated by chemical exchange spectroscopy. NMR data obtained on calbindin D9k (Chazin et al., 1989), insulin (Higgins et al., 1988), and staphylococcal nuclease (nuclease) as discussed below have shown that each exists in solution under native conditions as a mixture of slowly exchanging conformers. The fact that dynamic molecular heterogeneity in nuclease was first observed in the laboratory of Oleg Jardetzky, as manifested by splitting of the histidyl 1H ε1 resonance from His46 in one-dimensional 1H NMR spectra recorded at 100 MHz (Markley et al., 1970), makes this topic particularly appropriate to a volume celebrating his scientific contributions.
Conference papers on the topic "Bond exchange reaction"
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Cui, Fangda, I. Joga Rao, and Swapnil Moon. "Modeling and Simulation of Structurally Dynamic Crystallizable Shape Memory Polymers With Light-Induced Bond Exchange Reaction." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50247.
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Shape Memory polymers (SMPs) is a novel class of smart polymeric materials that have been attracted tremendous scientific interest within the last decades. SMPs have the ability to “remember” their original shape even after undergoing significant deformation into a temporary shape. For most first generation of SMPs, the shape memory effect was accomplished by a thermally induced process, triggered in many different ways, such as heating/cooling, electromagnetic field and infrared light. The transient shape in thermally induced SMPs is due to a glassy phase or a semi-crystalline phase. The thermally induced SMPs which temporary shape is fixed through crystallization is called crystallizable shape memory polymers (CSMPs). For traditional CSMPs, their original shape is predefined and is not able to be reprogrammed. This limits the applications of the CSMPs. Recently, a new class of CSMPs has been developed. These materials can perform a typical thermally induced shape memory cycle, but their original shape can be reprogrammed through exposing to UV light. The shape reprogramming effect is governed by light induced covalent bonds exchange reaction, while the shape memory effect-as typical CSMPs-is due to solid-phase crystallization. In this work, we focus on modeling the mechanical behavior of this new class of structurally dynamic CSMPs. The framework used in developing the model is built upon the theory of multiple natural configurations[1]. The model has been applied to solve a specific boundary condition problem, namely uni-axial tension. Furthermore, we implement our model through Abaqus (commercial finite element package) subroutine UMAT to simulate 3D behavior of this attractive material.
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Tufaner, Mustafa Batuhan, Sıtkı Sönmezer, and Ahmet Alkan Çelik. "Impact of Sovereign Credit Ratings on Capital Markets." In International Conference on Eurasian Economies. Eurasian Economists Association, 2017. http://dx.doi.org/10.36880/c08.01914.
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Sovereign credit ratings are of great importance in terms of country's economy in recent years. Sovereign credit ratings can greatly affect both financial markets and macroeconomic balances. On the other hand, these credit ratings are closely related to the political situation of the countries. Therefore, all factors behind the credit rating announcements operating in global markets needs to be put forward. The content of this paper is to identify policy interest reaction towards sovereign credit ratings and examine of countries that experienced severe rating changes. In this bulletin, big three credit rating agencies are compared and critically assessed various credit rating of Turkey. The analyzed dataset covers sovereign rating announcements released by reputable rating agencies, stock price, Dollar / TL exchange rate, Dollar / Euro exchange rate and benchmark bond.
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Nguyen, Khe C., Sinh T. Do, and Thong V. De. "Novel Proton Exchange Membrane Utilizing Nano Composite for Fuel Cell Application." In ASME 2006 Multifunctional Nanocomposites International Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/mn2006-17013.
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In the present report, we conducted the study of chemical top down process which seems to provide better efficiency and better cost saving than the physical top down in the fabrication of nano scale, especially, when applying to carbon materials. It is found that the chemical top down performs effectively with multiple attachments of electrolytic groups onto the surface of the carbon powder by diazo coupling reaction. As a result, we are able to isolate the nano scale of carbon particles with strong polar solvents such as water and believe that it is due to electrostatic repulsive force between same sign charges existing in the polarized electrolytic groups... The cleavage of azo bond in a naked carbon product can occur above 110oC in ambient condition but can also escape by a nano composite structure using specific emulsion polymer as binder matrix. Electrolytic groups carry charge from ionization are proven to reduce electron transport but enhance proton transport capability of carbon material, have successfully demonstrated a proton exchange membrane (PEM) which exhibits better heat resistance and higher current density than the commercial Nafion product in the PEM fuel cell application. The diazo coupling product of carbon exhibits a core-shell structure composed of a nano scale hydrophobic core and electrolytic shell, showing apparent “solubility” and named as “liquid” nano carbon (LNC).
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Pua, Lee M., and S. O. Rumbold. "Industrial Microchannel Devices: Where Are We Today?" In ASME 2003 1st International Conference on Microchannels and Minichannels. ASMEDC, 2003. http://dx.doi.org/10.1115/icmm2003-1101.
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Heatric has been involved in the commercial design and manufacturing of “micro/milli” scale heat exchanger core matrices called Printed Circuit Heat Exchangers (PCHEs) since 1985. These core matrices are formed by diffusion bonding together plates into which fluid flow microchannels have (usually) been formed by photo-chemical machining. Complex fluid circuitry is readily implemented with this technique. Diffusion bonding is a ‘solid-state joining’ process creating a bond of parent metal strength and ductility. The complete microchannel heat exchangers are highly compact, typically comprising about one-fifth the size and weight of conventional heat exchangers for the same thermal duty and pressure drops. PCHEs can be constructed out of a range of materials, including austenitic stainless steels suitable for design temperatures up to 800°C, and nickel alloys such as Incoloy 800HT suitable for design temperatures more than 900°C. Single units ranging from a few grams up to 100 tonnes have been manufactured. Currently there are thousands of tons of such microchannel matrix in hundreds of services — many of them arduous duties on offshore oil and gas platforms where the size and weight advantages of microchannel heat exchangers are of obvious benefit. Whilst these matrices are predominantly involved in thermally simple two-fluid heat exchange, albeit at pressures up to 500 bar, PCHEs have also been used for many multi-stream counter-flow heat exchangers. However the field of applications is very varied, including specialised chemicals processing, and PCHEs are even to be found orbiting the Earth in the International Space Station! Due to the inherent flexibility of the etching process, the basic construction may readily be applied to both a wider range, and more complex integration of process unit operations. Chemical reaction, rectification, stripping, mixing, and absorption, as well as boiling and condensation, can be incorporated into compact integrated process modules. Crucially, the resulting degree of compactness has led printed circuit technology to be the enabling technology in certain duties. Techniques for chemical coating onto the surfaces of channels continue to evolve, with applicability both to protective coatings and catalytically active coatings. We will describe a selection of innovative printed circuit technology examples. Alongside the more esoteric, Heatric is actively extending printed circuit technology to adapt to new market opportunities such as nuclear power generation plant and fuel cell systems. These applications perhaps represent two extremes of the both size and process integration, and thus aptly serve to demonstrate the range of industrial use of microchannel devices.
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Meyer, J., and P. Lan. "Multi-Material Bonding Solid-State Bonding Via Bond Exchange Reactions." In CAMX 2019. NA SAMPE, 2019. http://dx.doi.org/10.33599/nasampe/c.19.0834.
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Puchta, Ralph, and Dušan Ćoćić. "IRM@Be2+ – quantum chemistry between Bavaria and Šumadija." In 2nd International Conference on Chemo and Bioinformatics. Institute for Information Technologies, University of Kragujevac, 2023. http://dx.doi.org/10.46793/iccbi23.053p.
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Quantum chemical (density functional theory) mechanistic investigations on ligand exchange reactions at a tetrahedrally-coordinated dicationic Beryllium center offer a harmless and alternative way to learn about the traversed reaction pathways compared to experimental studies. Calculations for solvent exchange at [Be(H2O)4]2+, [Be(NH3)]2+, and [Be(HCN)4]2+ showed interchange (I) type mechanisms. To learn about the potential influences of spectator ligands we calculated the water exchange at [Be(L)(H2O)3]n+ (L: neutral ligands, mono-anionic ligands or cationic ligands) and got again consequently I-type paths. The activation energies depend strongly on the starting complexes, e.g., if hydrogen bonds have to be broken. The influence of spectator ligands is limited to the charge of the ligand and therefore the overall charge of the beryllium complex. The small size of the beryllium solvent complexes allows to test tools like AIM to dissect between pure interchange mechanisms, associative mechanisms and dissociative interchange mechanisms based on electron density along the reaction pathway.
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Selby, Greg, Shaun Aakre, and Zhaoyan Fan. "Non-Destructive Examination of Diffusion-Bonded Compact Heat Exchangers." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21293.
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Abstract Compact heat exchangers (CHX) fabricated using the diffusion bonding process will be useful in the design and operation of Generation IV nuclear power plants. The NDE challenges posed by diffusion-bonded compact heat exchangers (DBHE) are quite different from those of their more familiar shell-and-tube cousins. The examination scope encompasses three parts: the welds joining the headers to the CHX body; the body’s solid perimeter, serving as the pressure boundary; and the channeled interior. Current investigations are in support of a Section III Code Case including CHX fabrication rules and post-fabrication nondestructive evaluation (NDE) requirements to ensure adequate initial quality. In-service examination methodologies are also considered to inform code developers, regulators, and vendors exploring use of CHX in advanced reactor designs. The welds joining the headers to the CHX body likely will be full-penetration set-on welds of conventional design. Standard fabrication examinations, namely visual, dye penetrant and hydrostatic examinations will likely suffice. Additional methods should be specified for the purpose of ensuring that the weld stresses have not caused degradation or separation of individual layers within the adjacent diffusion-bonded core. The channeled core of the CHX is geometrically complex and does not allow application of traditional NDE methods from the outside. Radiography permits imaging of small demonstration scale components. Meanwhile, identifying bond failures within larger components may require embedded strain sensors. A theory for employing strain sensors to detect failures within the core is introduced here along with early experimental results. The diffusion-bonded solid perimeter should be examined to ensure that any presence of bonding failures is allowable. Ultrasonic examination results are presented, obtained from test blocks containing simulated bond failures and from high-pressure CHX used during lab studies.
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Zhang, Xinchang, Ryann E. Rupp, Jorgen F. Rufner, and Michael D. McMurtrey. "Electric-Field-Assisted Diffusion Welding to Fabricate Alloy 617 Compact Heat Exchangers." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-83842.
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Abstract Compact heat exchangers are of interest for a number of applications including advanced reactors. Alloy 617 is one of the top candidate materials for the gas-cooled reactor intermediate heat exchanger. Previous endeavors to diffusion weld Alloy 617 utilized hot pressing (HP). It was reported that grain boundary migration across the interface was hindered by extensive precipitation. Bonds of this nature have been observed to reduce the elevated-temperature mechanical properties compared to the wrought-product form. It was hypothesized that the electric current applied during electric-field-assisted sintering (EFAS) can overcome these challenges, resulting in improved diffusion welding (DW). This study investigated DW of Alloy 617 via EFAS. Stacks composed of three sheets that were 20 mm in diameter were welded using EFAS. Specimens were welded with an applied electric current, a pressure of 30 MPa, hold time of 30 min, and temperatures of 1050°C, 1100°C, and 1150°C. DW using HP as the zero-current analog of EFAS was also performed at the most promising EFAS conditions. Results revealed that both the applied electric current and temperature played a key role in precipitation and grain boundary migration in diffusion-welded Alloy 617. Precipitates were observed at the interface of the hot-pressed samples which limited grain boundary migration. Electric current was found to prevent precipitate formation along the interface at 1150°C. The electric current coupled with a temperature of 1150°C during EFAS resulted in significant grain boundary migration across the interface.
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Jang, Jaesung, Yabin Zhao, Steven T. Wereley, and Lichuan Gui. "Mass Flow Measurements of Gases in Deep-RIE Microchannels." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33779.
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We present mass flow measurements and pressure distributions in near unity aspect ratio microchannels using Deep Reactive Ion Etching (RIE). Almost all of the previous papers have dealt with only wide channels for gas flow measurements. We also adopt Spin-On-Glass (SOG) to bond Pyrex glass to silicon. Using the first order slip flow formula and experimental data, we extracted the tangential momentum accommodation coefficient (TMAC) of 0.425 for the case of SOG and Si microchannels and air, and the effective diameter of 57.67μm. Increased mass flow from the incompressible flow case is mostly due to compressibility rather than rarefaction, which is expected from the fact that the Knudsen number is 0.00115, the borderline of slip flows. The deviations from the linear incompressible pressure distributions get larger with increasing inlet pressures, and the dimensionless streamwise locations of maximum deviations are between 0.5 and 0.6, which is slightly downstream from the middle of the channels. It is notable that these experimental data are much closer to simulation results than the previous experiments in microchannels. The inlet pressure drops are almost linear with respect to pressure ratio of inlet to outlet. This type of near unity aspect ratio microchannel is more effective for heat exchangers than previous thin, wide channels.
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Sancaktar, E., and J. Kuznicki. "Stress-Dependent Water Uptake Behavior of Clay Reinforced Nanocomposite Epoxy." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80549.
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Layered silicate nanolayers can be used as alternative inorganic components for the construction of nanostructured hybrid composites. The clay silicate nanolayers possess stable Si-O bonds and high particle aspect ratios comparable to conventional fibers. Their interlayer surface is easily modified by ion-exchange reaction, and the gallery can be intercalated by organic polymer precursors for the formation of organic-inorganic nanocomposites. Exfoliated clay composites contain single, 1 nm thick layers of clay dispersed in the polymer matrix. Owing to the platy morphology of the silicate layers, exfoliated clay nanocomposites can exhibit dramatically improved properties such as barrier and mechanical properties that are not available for conventional composite materials. Since the clay particles scavenge water, the nanocomposite samples initially absorb slightly higher amounts of water in comparison to the no-clay samples, with the water molecules congregating around the clay particles. On the other hand, the presence of these clay particles still hinders diffusion of water through the sample, thus protecting the structural interfaces. In this work, low viscosity liquid aromatic diglycidyl ether of bisphenol A (DGEBA) epoxy resin Epon 815C was mixed with nanoclay at 60°C for 6 hours. The epoxy-clay mixture was then mixed with curing agent DETA (Diethylenetriamine) at 80°C for 4 minutes and cured at 120°C for 3 hours to produce exfoliated clay — epoxy resin system. These samples were used to first optimize the percent clay level for lowest water uptake, and subsequently immersed in water in stressed condition (flexural stress) to assess the effect of stress on nanocomposite epoxy system for its water uptake behavior. The results revealed up to 33% reduction in water uptake for the stressed samples.
Reports on the topic "Bond exchange reaction"
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Wicker, Louise, Ilan Shomer, and Uzi Merin. Membrane Processing of Citrus Extracts: Effects on Pectinesterase Activity and Cloud Stability. United States Department of Agriculture, October 1993. http://dx.doi.org/10.32747/1993.7568754.bard.
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The U.S. team studied the role of cations and pH on thermolabile (TL-PE) and thermostable (TS-PE), permeation in ultrafiltration (UF) membranes, affinity to ion exchange membranes, mechanism of cation and pH activation, and effect on PE stability. An optimum pH and cation concentration exists for activity and UF permeation, which is specific for each cation type. Incomplete release of PE from a pectin complex resulted in low PE binding to cationic and anionic membranes. Incubation of PE at low pH increases the surface hydrophobicity, especially TL-PE, but the secondary structure of TL-PE is not greatly affected. The Israeli team showed that stable cloud colloidal constituents flocculate following the conversion of soluble to insoluble biopolymers. First, formation of pectic acid by pectinesterase activity is followed by the formation of calcium pectate gel. This process initiates a myriad of poorly defined reactions that result in juice clarification. Second, protein coagulation by heat resulted in flocculation of proteinacous bound cloud constituents, particularly after enzymatic pectin degradation. Pectinesterase activity is proposed to be an indirect cause for clarification; whereas binding of cloud constituents is the primary event in clarification by pectate gel and coagulated proteins. Understanding the mechanism of interaction of protein and pectic polymers is key to understanding cloud instability. Based on the above, it was hypothesized that the structure of pectin-protein coagulates plays a key role in cloud instability.