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Sample records for aldol condensation reactions

  1. Sequential aldol condensation-transition metal-catalyzed addition reactions of aldehydes, methyl ketones, and arylboronic acids.

    PubMed

    Liao, Yuan-Xi; Xing, Chun-Hui; Israel, Matthew; Hu, Qiao-Sheng

    2011-04-15

    Sequential aldol condensation of aldehydes with methyl ketones followed by transition metal-catalyzed addition reactions of arylboronic acids to form β-substituted ketones is described. By using the 1,1'-spirobiindane-7,7'-diol (SPINOL)-based phosphite, an asymmetric version of this type of sequential reaction, with up to 92% ee, was also realized. Our study provided an efficient method to access β-substituted ketones and might lead to the development of other sequential/tandem reactions with transition metal-catalyzed addition reactions as the key step.

  2. Synthesis of dibenzoxepine lactams via a Cu-catalyzed one-pot etherification/aldol condensation cascade reaction: application toward the total synthesis of aristoyagonine.

    PubMed

    Lim, Hye Sun; Choi, Young Lok; Heo, Jung-Nyoung

    2013-09-20

    A general synthesis of dibenzoxepine lactams has been developed using a one-pot Cu-catalyzed etherification/aldol condensation cascade reaction. The reaction of 4-hydroxyisoindolin-1-one with a wide range of 2-bromobenzaldehydes in the presence of a copper catalyst provided various aristoyagonine derivatives in good yields. PMID:24000941

  3. The Aldol Addition and Condensation: The Effect of Conditions on Reaction Pathway

    ERIC Educational Resources Information Center

    Crouch, R. David; Richardson, Amie; Howard, Jessica L.; Harker, Rebecca L.; Barker, Kathryn H.

    2007-01-01

    The reaction of a ketone and an aldehyde in aqueous Na[subscript 2]CO[subscript 2] is described. This experiment is performed in the absence of strong bases or organic solvents and offers the opportunity for students to observe the critical role that reaction temperature and base strength have in determining the product of the base-mediated…

  4. Mukaiyama Aldol Reactions in Aqueous Media

    PubMed Central

    Kitanosono, Taku; Kobayashi, Shū

    2013-01-01

    Mukaiyama aldol reactions in aqueous media have been surveyed. While the original Mukaiyama aldol reactions entailed stoichiometric use of Lewis acids in organic solvents under strictly anhydrous conditions, Mukaiyama aldol reactions in aqueous media are not only suitable for green sustainable chemistry but are found to produce singular phenomena. These findings led to the discovery of a series of water-compatible Lewis acids such as lanthanide triflates in 1991. Our understanding on these beneficial effects in the presence of water will be deepened through the brilliant examples collected in this review. 1 Introduction 2 Rate Enhancement by Water in the Mukaiyama Aldol Reaction 3 Lewis Acid Catalysis in Aqueous or Organic Solvents 3.1 Water-Compatible Lewis Acids 4 Lewis-Base Catalysis in Aqueous or Organic Solvents 5 The Mukaiyama Aldol Reactions in 100% Water 6 Asymmetric Catalysts in Aqueous Media and Water 7 Conclusions and Perspective PMID:24971045

  5. Enantioselective aldol reactions with masked fluoroacetates

    NASA Astrophysics Data System (ADS)

    Saadi, Jakub; Wennemers, Helma

    2016-03-01

    Despite the growing importance of organofluorines as pharmaceuticals and agrochemicals, the stereoselective introduction of fluorine into many prominent classes of natural products and chemotherapeutic agents is difficult. One long-standing unsolved challenge is the enantioselective aldol reaction of fluoroacetate to enable access to fluorinated analogues of medicinally relevant acetate-derived compounds, such as polyketides and statins. Herein we present fluoromalonic acid halfthioesters as biomimetic surrogates of fluoroacetate and demonstrate their use in highly stereoselective aldol reactions that proceed under mild organocatalytic conditions. We also show that the methodology can be extended to formal aldol reactions with fluoroacetaldehyde and consecutive aldol reactions. The synthetic utility of the fluorinated aldol products is illustrated by the synthesis of a fluorinated derivative of the top-selling drug atorvastatin. The results show the prospects of the method for the enantioselective introduction of fluoroacetate to access a wide variety of highly functionalized fluorinated compounds.

  6. The Direct Catalytic Asymmetric Aldol Reaction

    PubMed Central

    Brindle, Cheyenne S.

    2013-01-01

    Asymmetric aldol reactions are a powerful method for the construction of carbon-carbon bonds in an enantioselective fashion. Historically this reaction has been performed in a stoichiometric fashion to control the various aspects of chemo-, diastereo-, regio- and enantioselectivity, however, a more atom economical approach would unite high selectivity with the use of only a catalytic amount of a chiral promoter. This critical review documents the development of direct catalytic asymmetric aldol methodologies, including organocatalytic and metal-based strategies. New methods have improved the reactivity, selectivity and substrate scope of the direct aldol reaction and enabled the synthesis of complex molecular targets PMID:20419212

  7. A Green Enantioselective Aldol Condensation for the Undergraduate Organic Laboratory

    ERIC Educational Resources Information Center

    Bennett, George D.

    2006-01-01

    A number of laboratory exercises for the organic chemistry curriculum that emphasize enantioselective synthesis of the aldol condensation which involves the proline-catalyzed condensation between acetone and isobutyraldehyde are explored. The experiment illustrates some of the trade-offs involved in green chemistry like the use of acetone in large…

  8. Asymmetric, Three-Component, One-Pot Synthesis of Spiropyrazolones and 2,5-Chromenediones from Aldol Condensation/NHC-Catalyzed Annulation Reactions.

    PubMed

    Wang, Lei; Li, Sun; Chauhan, Pankaj; Hack, Daniel; Philipps, Arne R; Puttreddy, Rakesh; Rissanen, Kari; Raabe, Gerhard; Enders, Dieter

    2016-04-01

    A novel one-pot, three-component diastereo- and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β-unsaturated pyrazolones, which react with a second equivalent of enal through an N-heterocyclic carbene (NHC)-catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1,3-diketones, 2,5-chromenediones are available through [2+4] annulation.

  9. Asymmetric, Three-Component, One-Pot Synthesis of Spiropyrazolones and 2,5-Chromenediones from Aldol Condensation/NHC-Catalyzed Annulation Reactions.

    PubMed

    Wang, Lei; Li, Sun; Chauhan, Pankaj; Hack, Daniel; Philipps, Arne R; Puttreddy, Rakesh; Rissanen, Kari; Raabe, Gerhard; Enders, Dieter

    2016-04-01

    A novel one-pot, three-component diastereo- and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β-unsaturated pyrazolones, which react with a second equivalent of enal through an N-heterocyclic carbene (NHC)-catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1,3-diketones, 2,5-chromenediones are available through [2+4] annulation. PMID:26864437

  10. Asymmetric Aldol-Tishchenko Reaction of Sulfinimines.

    PubMed

    Foley, Vera M; McSweeney, Christina M; Eccles, Kevin S; Lawrence, Simon E; McGlacken, Gerard P

    2015-11-20

    Methods for the preparation of 1,3-amino alcohols and their derivatives containing two stereogenic centers usually involve a two-step installation of the chiral centers. An aldol-Tishchenko reaction of chiral sulfinimines which involves the first reported reduction of a C═N in this type of reaction is described. Two and even three chiral centers can be installed in one synthetic step, affording anti-1,3-amino alcohols in good diastereo- and enantioselectivity. PMID:26528888

  11. Iron-catalyzed vinylogous aldol condensation of Biginelli products and its application toward pyrido[4,3-d]pyrimidinones.

    PubMed

    Zhang, Lianqiang; Zhang, Zhiguo; Liu, Qingfeng; Liu, Tongxin; Zhang, Guisheng

    2014-03-01

    A novel iron-catalyzed vinylogous aldol condensation of Biginelli products with aryl aldehydes has been developed for the syntheses of potential bioactive (E)-6-arylvinyl-dihydropyrimidin-2(1H)-ones. These materials are valuable synthetic precursors to drug-like pyrido[4,3-d]pyrimidine derivatives. The amide group at the 5-position of the dihydropyrimidin-2(1H)-ones played an important role in the vinylogous aldol condensation reaction. PMID:24517724

  12. Organocatalytic enantioselective Michael-Michael-Michael-aldol condensation reactions: control of five stereocenters in a quadruple-cascade asymmetric synthesis of highly functionalized hexahydrophenanthrenes.

    PubMed

    Raja, Arun; Hong, Bor-Cherng; Lee, Gene-Hsiang

    2014-11-01

    A cascade organocatalysis has been developed for the enantioselective synthesis of a highly functionalized hexahydrophenanthrene-2-carbaldehyde containing five contiguous stereogenic centers with high diastereoselectivity and high enantioselectivity (>99% ee). The one-pot method comprises a cascade of organocatalytic Michael-Michael-Michael-aldol reactions of 2-methyl-1,5-dinitro-3-((E)-2-nitrovinyl)benzene and α,β-unsaturated aldehydes (e.g., cinnamaldehyde). The structure and absolute configuration of a product were confirmed by X-ray analysis of an appropriate derivative.

  13. Aldol Condensation Products and Polyacetals in Organic Films Formed from Reactions of Propanal in Sulfuric Acid at Upper Troposphere/Lower Stratosphere (UT/LS) Aerosol Acidities

    NASA Astrophysics Data System (ADS)

    Bui, J. V. H.; Perez-Montano, S.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.; Van Wyngarden, A. L.

    2015-12-01

    Aerosols in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt. %) which is highly reflective towards UV and visible radiation. However, airborne measurements have shown that these particles may also contain a significant amount of organic material. Experiments combining organics (propanal, glyoxal and/or methylglyoxal) with sulfuric acid at concentrations typical of UT/LS aerosols produced highly colored surface films (and solutions) that have the potential to impact chemical, optical and/or cloud-forming properties of aerosols. In order to assess the potential for such films to impact aerosol chemistry or climate properties, experiments were performed to identify the chemical processes responsible for film formation. Surface films were analyzed via Attenuated Total Reflectance-FTIR and Nuclear Magnetic Resonance spectroscopies and are shown to consist primarily of aldol condensation products and cyclic and linear polyacetals, the latter of which are likely responsible for separation from the aqueous phase.

  14. Thermodynamically driven, syn-selective vinylogous aldol reaction of tetronamides.

    PubMed

    Karak, Milandip; Barbosa, Luiz C A; Acosta, Jaime A M; Sarotti, Ariel M; Boukouvalas, John

    2016-06-01

    A stereoselective vinylogous aldol reaction of N-monosubstituted tetronamides with aldehydes is described. The procedure is simple and scalable, works well with both aromatic and aliphatic aldehydes, and affords mainly the corresponding syn-aldol adducts. In many cases, the latter are obtained essentially free of their anti-isomers (dr > 99 : 1) in high yields (70-90%). Experimental and computational studies suggest that the observed diastereoselectivity arises through anti-syn isomer interconversion, enabled by an iterative retro-aldol/aldol reaction.

  15. Mineral catalysis of a potentially prebiotic aldol condensation

    NASA Technical Reports Server (NTRS)

    De Graaf, R. M.; Visscher, J.; Xu, Y.; Arrhenius, G.; Schwartz, A. W.

    1998-01-01

    Minerals may have played a significant role in chemical evolution. In the course of investigating the chemistry of phosphonoacetaldehyde (PAL), an analogue of glycolaldehyde phosphate, we have observed a striking case of catalysis by the layered hydroxide mineral hydrotalcite ([Mg2Al(OH)6][Cl.nH2O]). In neutral or moderately basic aqueous solutions, PAL is unreactive even at a concentration of 0.1 M. In the presence of a large excess of NaOH (2 M), the compound undergoes aldol condensation to produce a dimer containing a C3-C4 double-bond. In dilute neutral solutions and in the presence of the mineral, however, condensation takes place rapidly, to produce a dimer which is almost exclusively the C2-C3 unsaturated product.

  16. Bifunctional Brønsted Base Catalyzes Direct Asymmetric Aldol Reaction of α-Keto Amides.

    PubMed

    Echave, Haizea; López, Rosa; Palomo, Claudio

    2016-03-01

    The first enantioselective direct cross-aldol reaction of α-keto amides with aldehydes, mediated by a bifunctional ureidopeptide-based Brønsted base catalyst, is described. The appropriate combination of a tertiary amine base and an aminal, and urea hydrogen-bond donor groups in the catalyst structure promoted the exclusive generation of the α-keto amide enolate which reacted with either non-enolizable or enolizable aldehydes to produce highly enantioenriched polyoxygenated aldol adducts without side-products resulting from dehydration, α-keto amide self-condensation, aldehyde enolization, and isotetronic acid formation.

  17. Bifunctional Brønsted Base Catalyzes Direct Asymmetric Aldol Reaction of α-Keto Amides.

    PubMed

    Echave, Haizea; López, Rosa; Palomo, Claudio

    2016-03-01

    The first enantioselective direct cross-aldol reaction of α-keto amides with aldehydes, mediated by a bifunctional ureidopeptide-based Brønsted base catalyst, is described. The appropriate combination of a tertiary amine base and an aminal, and urea hydrogen-bond donor groups in the catalyst structure promoted the exclusive generation of the α-keto amide enolate which reacted with either non-enolizable or enolizable aldehydes to produce highly enantioenriched polyoxygenated aldol adducts without side-products resulting from dehydration, α-keto amide self-condensation, aldehyde enolization, and isotetronic acid formation. PMID:26835655

  18. Direct Catalytic Enantio- and Diastereoselective Ketone Aldol Reactions of Isocyanoacetates**

    PubMed Central

    delaCampa, Raquel; Ortín, Irene; Dixon, Darren J

    2015-01-01

    A catalytic asymmetric aldol addition/cyclization reaction of unactivated ketones with isocyanoacetate pronucleophiles has been developed. A quinine-derived aminophosphine precatalyst and silver oxide were found to be an effective binary catalyst system and promoted the reaction to afford chiral oxazolines possessing a fully substituted stereocenter with good diastereoselectivities and excellent enantioselectivities. PMID:25735645

  19. Cu/MgAl(2)O(4) as bifunctional catalyst for aldol condensation of 5-hydroxymethylfurfural and selective transfer hydrogenation.

    PubMed

    Pupovac, Kristina; Palkovits, Regina

    2013-11-01

    Copper supported on mesoporous magnesium aluminate has been prepared as noble-metal-free solid catalyst for aldol condensation of 5-hydroxymethylfurfural with acetone, followed by hydrogenation of the aldol condensation products. The investigated mesoporous spinels possess high activity as solid-base catalysts. Magnesium aluminate exhibits superior activity compared to zinc and cobalt-based aluminates, reaching full conversion and up to 81 % yield of the 1:1 aldol product. The high activity can be correlated to a higher concentration of basic surface sites on magnesium aluminate. Applying continuous regeneration, the catalysts can be recycled without loss of activity. Focusing on the subsequent hydrogenation of aldol condensation products, Cu/MgAl2 O4 allows a selective hydrogenation and CO bond cleavage, delivering 3-hydroxybutyl-5-methylfuran as the main product with up to 84 % selectivity avoiding ring saturation. Analysis of the hydrogenation activity reveals that the reaction proceeds in the following order: CC>CO>CO cleavage>ring hydrogenation. Comparable activity and selectivity can be also achieved utilizing 2-propanol as solvent in the transfer hydrogenation, providing the possibility for partial recycling of acetone and optimization of the hydrogen management. PMID:24038987

  20. Acid-Base Pairs in Lewis Acidic Zeolites Promote Direct Aldol Reactions by Soft Enolization.

    PubMed

    Lewis, Jennifer D; Van de Vyver, Stijn; Román-Leshkov, Yuriy

    2015-08-17

    Hf-, Sn-, and Zr-Beta zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions.

  1. Investigating Ionic Effects Applied to Water Based Organocatalysed Aldol Reactions

    PubMed Central

    Delaney, Joshua P.; Henderson, Luke C.

    2011-01-01

    Saturated aqueous solutions of various common salts were examined for their effect on aqueous aldol reactions catalysted by a highly active C2-symmetric diprolinamide organocatalyst developed in our laboratory. With respect to the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, deionised water was always a superior medium to salt solutions though some correlation to increasing anion size and depression in enantiomeric excess could be observed. Additionally, the complete inhibition of catalyst activity observed when employing tap water could be alleviated by the inclusion of ethylenediaminetetraacetate (EDTA) into the aqueous media prior to reaction initiation. Extension of these reaction conditions demonstrated that these ionic effects vary on a case-to-case basis depending on the ketone/aldehyde combination. PMID:22272120

  2. Stereoselectivity in (Acyloxy)borane-Catalyzed Mukaiyama Aldol Reactions.

    PubMed

    Lee, Joshua M; Zhang, Xin; Norrby, Per-Ola; Helquist, Paul; Wiest, Olaf

    2016-07-01

    The origin of diastereo- and enantioselectivity in a Lewis acid-catalyzed Mukaiyama aldol reaction is investigated using a combination of dispersion corrected DFT calculations and transition state force fields (TSFF) developed using the quantum guided molecular mechanics (Q2MM) method. The reaction proceeds via a closed transition structure involving a nontraditional hydrogen bond that is 3.3 kJ/mol lower in energy than the corresponding open transition structure. The correct prediction of the diastereoselectivity of a Mukaiyama aldol reaction catalyzed by the conformationally flexible Yamamoto chiral (acyloxy) borane (CAB) requires extensive conformational sampling at the transition structure, which is achieved using a Q2MM-derived TSFF, followed by DFT calculations of the low energy conformational clusters. Finally, a conceptual model for the rationalization of the observed diastereo- and enantioselectivity of the reaction using a closed transition state model is proposed. PMID:27247023

  3. Molecular Dynamics Simulations of Aldol Condensation Catalyzed by Alkylamine-Functionalized Crystalline Silica Surfaces.

    PubMed

    Kim, Ki Chul; Moschetta, Eric G; Jones, Christopher W; Jang, Seung Soon

    2016-06-22

    Molecular dynamics simulations are performed to investigate the cooperatively catalyzed aldol condensation between acetone and 4-nitrobenzaldehyde on alkylamine (or alkylenamine)-grafted silica surfaces, focusing on the mechanism of the catalytic activation of the acetone and 4-nitrobenzaldehyde by the acidic surface silanols followed by the nucleophilic attack of the basic amine functional group toward the activated reactant. From the analysis of the correlations between the catalytically active acid-base sites and reactants, it is concluded that the catalytic cooperativity of the acid-base pair can be affected by two factors: (1) the competition between the silanol and the amine (or enamine) to form a hydrogen bond with a reactant and (2) the flexibility of the alkylamine (or alkylenamine) backbone. Increasing the flexibility of the alkylamine facilitates the nucleophilic attack of the amine on the reactants. From the molecular dynamics simulations, it is found that C3 propylamine and C4 butylamine linkers exhibit the highest probability of reaction, which is consistent with the experimental observation that the activity of the aldol reaction on mesoporous silica depends on the length of alkylamine grafted on the silica surface. This simulation work serves as a pioneering study demonstrating how the molecular simulation approach can be successfully employed to investigate the cooperative catalytic activity of such bifunctional acid-base catalysts.

  4. Functionalized multi-walled carbon nanotubes in an aldol reaction

    NASA Astrophysics Data System (ADS)

    Chronopoulos, D. D.; Kokotos, C. G.; Karousis, N.; Kokotos, G.; Tagmatarchis, N.

    2015-01-01

    The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction between acetone and 4-nitrobenzaldehyde was evaluated for the first time, showing to proceed almost quantitatively in aqueous media. Furthermore, several amino-modified MWCNTs were prepared and examined in the particular aldol reaction. These new hybrid materials exhibited an enhanced catalytic activity in water, contrasting with the pristine MWCNTs as well as the parent organic molecule, which failed to catalyze the reaction efficiently. Furthermore, the modified MWCNTs proved to catalyze the aldol reaction even after three repetitive cycles. Overall, a green approach for the aldol reaction is presented, where water can be employed as the solvent and modified MWCNTs can be used as catalysts, which can be successfully recovered and reused, while their catalytic activity is retained.The covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with a proline-based derivative is reported. Initially, MWCNTs were oxidized in order to introduce a large number of carboxylic units on their tips followed by N-tert-butoxycarbonyl-2,2'(ethylenedioxy)bis-(ethylamine) conjugation through an amide bond. Then, a proline derivative bearing a carboxylic terminal moiety at the 4-position was coupled furnishing proline-modified MWCNTs. This new hybrid material was fully characterized by spectroscopic and microscopy means and its catalytic activity in the asymmetric aldol reaction

  5. Illustrating the Utility of X-Ray Crystallography for Structure Elucidation through a Tandem Aldol Condensation/Diels-Alder Reaction Sequence

    ERIC Educational Resources Information Center

    Hoang, Giang T.; Kubo, Tomohiro; Young, Victor G., Jr.; Kautzky, Jacob A.; Wissinger, Jane E.

    2015-01-01

    Two introductory organic chemistry laboratory experiments are described based on the Diels-Alder reaction of 2,3,4,5-tetraphenylcyclopentadienone, which is synthesized prior to or in a one-pot reaction, with styrene. Students are presented with three possible products, the "endo" and "exo" diastereomers and the decarbonylated…

  6. Convergent fabrication of a nanoporous two-dimensional carbon network from an aldol condensation on metal surfaces

    NASA Astrophysics Data System (ADS)

    Landers, John; Chérioux, Frédéric; De Santis, Maurizio; Bendiab, Nedjma; Lamare, Simon; Magaud, Laurence; Coraux, Johann

    2014-12-01

    We report a convergent surface polymerization reaction scheme on Au(111), based on a triple aldol condensation, yielding a carbon-rich, covalent nanoporous two-dimensional network. The reaction is not self-poisoning and proceeds up to a full surface coverage. The deposited precursor molecules 1, 3, 5-tri(4’-acetylphenyl) first form supramolecular assemblies that are converted to the porous covalent network upon heating. The formation and structure of the network and of the intermediate steps are studied with scanning tunneling microscopy, Raman spectroscopy and density functional theory.

  7. Method of carbon chain extension using novel aldol reaction

    DOEpatents

    Silks, Louis A; Gordon, John C; Wu, Ruilan; Hanson, Susan Kloek

    2013-07-30

    Method of producing C.sub.8-C.sub.15 hydrocarbons. comprising providing a ketone starting material; providing an aldol starting material comprising chloromethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro).sub.2, Yb(Pro).sub.3, and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are: ##STR00001## where R.sub.1 is a C.sub.1-C.sub.6 alkyl moiety, X=(OH) and n=2. ##STR00002## In (III), X may be CH.sub.2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R.sub.1 and R.sub.2 each independently may be a methyl, ethyl, phenyl moiety.

  8. Method of carbon chain extension using novel aldol reaction

    DOEpatents

    Silks, Louis A; Gordon, John C; Wu, Ruilan; Hangson, Susan Kloek

    2013-08-13

    Method of producing C.sub.8-C.sub.15 hydrocarbons comprising providing a ketone starting material; providing an aldol starting material comprising hydroxymethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro).sub.2, Yb(Pro).sub.2, and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are: ##STR00001## where R.sub.1 is a C.sub.1-C.sub.6 alkyl moiety, X=(OH) and n=2. ##STR00002## In (III), X may be CH.sub.2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R.sub.1 and R.sub.2 each independently may be a methyl, ethyl, phenyl moiety.

  9. Origins of the double asymmetric induction on proline-catalyzed aldol reactions.

    PubMed

    Calderón, Félix; Doyagüez, Elisa G; Cheong, Paul Ha-Yeon; Fernández-Mayoralas, Alfonso; Houk, K N

    2008-10-17

    Computational studies to elucidate the origin of the double asymmetric induction on proline-catalyzed aldol reaction have been performed using HF/6-31G(d) calculations. The computed transition structures explain the experimental data obtained. PMID:18811197

  10. Tandem Catalysis of an Aldol-'Click' Reaction System within a Molecular Hydrogel.

    PubMed

    Araújo, Marco; Muñoz Capdevila, Iván; Díaz-Oltra, Santiago; Escuder, Beatriu

    2016-01-01

    A heterogeneous supramolecular catalytic system for multicomponent aldol-'click' reactions is reported. The copper(I) metallohydrogel functionalized with a phenyltriazole fragment was able to catalyze the multicomponent reaction between phenylacetylene, p-nitrobenzaldehyde, and an azide containing a ketone moiety, obtaining the corresponding aldol products in good yields. A possible mechanistic pathway responsible for this unexpected catalytic behavior has been proposed. PMID:27338313

  11. Copper-catalyzed retro-aldol reaction of β-hydroxy ketones or nitriles with aldehydes: chemo- and stereoselective access to (E)-enones and (E)-acrylonitriles.

    PubMed

    Zhang, Song-Lin; Deng, Zhu-Qin

    2016-07-26

    A copper-catalyzed transfer aldol type reaction of β-hydroxy ketones or nitriles with aldehydes is reported, which enables chemo- and stereoselective access to (E)-α,β-unsaturated ketones and (E)-acrylonitriles. A key step of the in situ copper(i)-promoted retro-aldol reaction of β-hydroxy ketones or nitriles is proposed to generate a reactive Cu(i) enolate or cyanomethyl intermediate, which undergoes ensuing aldol condensation with aldehydes to deliver the products. This reaction uses 1.2 mol% Cu(IPr)Cl (IPr denotes 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) as the catalyst in the presence of 6.0 mol% NaOtBu cocatalyst at room temperature or 70 °C. A range of aryl and heteroaryl aldehydes as well as acrylaldehydes are compatible with many useful functional groups being tolerated. Under the mild and weakly basic conditions, competitive Cannizzaro-type reaction of benzaldehydes and side reactions of base-sensitive functional groups can be effectively suppressed, which show synthetic advantages of this reaction compared to classic aldol reactions. The synthetic potential of this reaction is further demonstrated by the one-step synthesis of biologically active quinolines and 1,8-naphthyridine in excellent yields (up to 91%). Finally, a full catalytic cycle for this reaction has been constructed using DFT computational studies in the context of a retro-aldol/aldol two-stage mechanism. A rather flat reaction energy profile is found indicating that both stages are kinetically facile, which is consistent with the mild reaction conditions.

  12. Copper-catalyzed retro-aldol reaction of β-hydroxy ketones or nitriles with aldehydes: chemo- and stereoselective access to (E)-enones and (E)-acrylonitriles.

    PubMed

    Zhang, Song-Lin; Deng, Zhu-Qin

    2016-07-26

    A copper-catalyzed transfer aldol type reaction of β-hydroxy ketones or nitriles with aldehydes is reported, which enables chemo- and stereoselective access to (E)-α,β-unsaturated ketones and (E)-acrylonitriles. A key step of the in situ copper(i)-promoted retro-aldol reaction of β-hydroxy ketones or nitriles is proposed to generate a reactive Cu(i) enolate or cyanomethyl intermediate, which undergoes ensuing aldol condensation with aldehydes to deliver the products. This reaction uses 1.2 mol% Cu(IPr)Cl (IPr denotes 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) as the catalyst in the presence of 6.0 mol% NaOtBu cocatalyst at room temperature or 70 °C. A range of aryl and heteroaryl aldehydes as well as acrylaldehydes are compatible with many useful functional groups being tolerated. Under the mild and weakly basic conditions, competitive Cannizzaro-type reaction of benzaldehydes and side reactions of base-sensitive functional groups can be effectively suppressed, which show synthetic advantages of this reaction compared to classic aldol reactions. The synthetic potential of this reaction is further demonstrated by the one-step synthesis of biologically active quinolines and 1,8-naphthyridine in excellent yields (up to 91%). Finally, a full catalytic cycle for this reaction has been constructed using DFT computational studies in the context of a retro-aldol/aldol two-stage mechanism. A rather flat reaction energy profile is found indicating that both stages are kinetically facile, which is consistent with the mild reaction conditions. PMID:27397647

  13. Domino Michael-Michael and Aldol-Aldol Reactions: Diastereoselective Synthesis of Functionalized Cyclohexanone Derivatives Containing Quaternary Carbon Center.

    PubMed

    Ghorai, Manas K; Halder, Sandipan; Das, Subhomoy

    2015-10-01

    A simple strategy for the synthesis of highly functionalized cyclohexanone derivatives containing an all-carbon quaternary center from α-(aryl/alkyl)methylidene-β-keto esters or β-diketones via a K-enolate mediated domino Michael-Michael reaction sequence with moderate to good yield and excellent diastereoselectivity (de > 99%) is described. Interestingly, Li-base mediated reaction of α-arylmethylidene-β-diketones affords functionalized 3,5-dihydroxy cyclohexane derivatives as the kinetically controlled products via a domino aldol-aldol reaction sequence with excellent diastereoselectivity. Li-enolates of the β-keto esters or β-diketones undergo facile domino Michael-Michael reaction with nitro-olefins to afford the corresponding nitrocyclohexane derivatives in good yields and excellent diastereoselectivity (de > 99%). The formation of the products and the observed stereoselectivity were explained by plausible mechanisms and supported by extensive computational study. An asymmetric version of the protocol was explored with (L)-menthol derived nonracemic substrates, and the corresponding nonracemic cyclohexanone derivatives containing an all-carbon quaternary center were obtained with excellent stereoselectivity (de, ee > 99%).

  14. Developing novel organocatalyzed aldol reactions for the enantioselective synthesis of biologically active molecules

    PubMed Central

    Bhanushali, Mayur; Zhao, Cong-Gui

    2011-01-01

    Aldol reaction is one of the most important methods for the formation of carbon-carbon bonds. Because of its significance and usefulness, asymmetric versions of this reaction have been realized with different approaches in the past. Over the last decade, the area of organocatalysis has made significant progresses. As one of most studied reactions in organocatalyses, organocatalyzed aldol reaction has emerged as a powerful tool for the synthesis of a large number of useful products in optically enriched forms. In this review, we summarize our efforts on the development of novel organocatalyzed aldol reactions for the enantioselective synthesis of biological active molecules. Literatures closely related to our studies are also covered. PMID:21918584

  15. A self-assembled nanotube for the direct aldol reaction in water.

    PubMed

    Lee, Kwang Soo; Parquette, Jon R

    2015-11-01

    Nanotubes formed by the aqueous assembly of a proline-lysine dipeptide (1) were used to create the hydrophobic microenvironments required to catalyze the aldol reaction in water. The self-assembly process occurred most efficiently in the presence of the substrates, producing an array of homogeneous nanotubes under the reaction conditions. The nanotubes formed by dipeptide 1 served as an efficient catalyst for the aldol reaction that functioned at low loading levels and provided good to excellent conversions. The catalytic activity of 1 was minimal under conditions that dissociated the nanotube into soluble monomers.

  16. Highly active copper-network catalyst for the direct aldol reaction.

    PubMed

    Ohta, Hidetoshi; Uozumi, Yasuhiro; Yamada, Yoichi M A

    2011-09-01

    The development of a highly active solid-phase catechol-copper network catalyst for direct aldol reaction is described. The catalyst was prepared from an alkyl-chain-linked bis(catechol) and a copper(II) complex. The direct aldol reaction between carbonyl compounds (aldehydes and ketones) and methyl isocyanoacetate was carried out using 0.1-1 mol% [Cu] catalyst to give the corresponding oxazolines at yields of up to 99% and a trans/cis ratio of >99:1. The catalyst was reused with no loss of catalytic activity. A plausible reaction pathway is also described. PMID:21751405

  17. Binaphthyl-based chiral bifunctional organocatalysts for water mediated asymmetric List-Lerner-Barbas aldol reactions.

    PubMed

    Ashokkumar, Veeramanoharan; Chithiraikumar, Chinnadurai; Siva, Ayyanar

    2016-10-14

    Novel binaphthyl-based chiral bifunctional organocatalysts were designed, synthesized and successfully applied to the asymmetric List-Lerner-Barbas aldol reaction in the presence of water. These organocatalysts were found to be effective catalysts for the reactions of symmetrical, unsymmetrical and cyclic ketones with different aldehydes to give the corresponding aldol products with higher yields (up to 98%) and very good ee's up to 99%. The catalytic system leads to higher yields and selectivities than the previously reported well-known proline based organocatalysts. In addition to the effect of solvent, additives, catalyst concentration, temperature and the substrate scope of the reactions were also investigated. PMID:27604169

  18. α-Hydroxyallylsilanes as propionaldehyde enolate equivalents and their use toward iterative aldol reactions.

    PubMed

    Ruiz, Johal; Murthy, Akondi Srirama; Roisnel, Thierry; Chandrasekhar, Srivari; Grée, René

    2015-02-20

    Smooth and efficient reaction conditions have been found for the transformation of protected β-hydroxyacylsilanes into the corresponding aldehydes. This opens a new route to iterative aldol reactions, and it has been used for the synthesis of fragments of several bioactive natural products. PMID:25636066

  19. Total Synthesis of the Antimicrotubule Agent (+)-Discodermolide Using Boron-Mediated Aldol Reactions of Chiral Ketones.

    PubMed

    Paterson; Florence; Gerlach; Scott

    2000-01-01

    With a similar mechanism of action to taxol, the title compound 1 is a particularly promising candidate for development in cancer chemotherapy. This efficient synthesis, based on stereocontrolled aldol reactions, should help to overcome the scarce natural supply of 1 from the rare sponge source.

  20. ALDOL- AND MANNICH-TYPE REACTIONS VIA IN SITU OLEFIN MIGRATION IN IONIC LIQUID

    EPA Science Inventory


    An aldol-type and a Mannich-type reaction via the cross-coupling of aldehydes and imines with allylic alcohols catalyzed by RuCl2(PPh3)3 was developed with ionic liquid as the solvent. The solvent/catalyst system could be reused for at least five times with no loss of reactiv...

  1. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN IONIC LIQUID.

    EPA Science Inventory

    In the presence of a catalytic amount of RuCl2(PPh3)3, a cross-coupling of 3-buten-2-ol with aldehydes and imines was developed via a tandem olefin migration--aldol--Mannich reaction in bmim[PF6]. With In(OAc)3 as a co-catalyst, a-vinylbenzyl alcohol and aldehydes underwent sim...

  2. Parameterization of the ReaxFF reactive force field for a proline-catalyzed aldol reaction.

    PubMed

    Hubin, Pierre O; Jacquemin, Denis; Leherte, Laurence; Vercauteren, Daniel P

    2016-11-01

    A parameterization of the ReaxFF reactive FF is performed using a Monte Carlo Simulated Annealing procedure for the modeling of a proline-catalyzed aldol reaction. Emphasis is put on the accurate reproduction of the relative stabilities of several key intermediates of the reaction, as well as, on the description of the reaction path bridging these intermediates based on quantum mechanical calculations. Our training sets include new criteria based on geometry optimizations and short Molecular Dynamics simulations to ensure that the trained ReaxFF potentials adequately predict the structures of all key intermediates. The transferability of the sets of parameters obtained is assessed for various steps of the considered aldol reaction, as well as for different substrates, catalysts, and reagents. This works indeed highlights the challenge of reaching transferable parameters for several reaction steps. © 2016 Wiley Periodicals, Inc.

  3. The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation

    SciTech Connect

    Yu Xiaofang; Yu Xiaobo; Wu Shujie; Liu Bo; Liu Heng; Guan Jingqi; Kan Qiubin

    2011-02-15

    Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N{sub 2} adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization. -- Graphical abstract: Proximal-C-A-SBA-15 with a proximal acid-base distance and maximum-C-A-SBA-15 with a maximum acid-base distance were synthesized by immobilizing lysine onto carboxyl-SBA-15. Display Omitted Research highlights: {yields} Proximal-C-A-SBA-15 with a proximal acid-base distance. {yields} Maximum-C-A-SBA-15 with a maximum acid-base distance. {yields} Compared to maximum-C-A-SBA-15, proximal-C-A-SBA-15 was more active toward aldol condensation reaction between acetone and various aldehydes.

  4. Aldol reactions of the trans-o-hydroxybenzylidenepyruvate hydratase-aldolase (tHBP-HA) from Pseudomonas fluorescens N3.

    PubMed

    Sello, Guido; Di Gennaro, Patrizia

    2013-08-01

    In this paper, a recombinant trans-o-hydroxybenzylidenepyruvate hydratase-aldolase (tHBP-HA) of Pseudomonas fluorescens N3 was used as a new catalyst for aldol condensation reactions. The reaction of some aldehydes with a different electronic activation catalyzed by tHBP-HA is presented and discussed together with some hints on the product structure. The enzyme is strictly pyruvate-dependent but uses different aldehydes as acceptors. The structure of the products is highly dependent on the electronic characteristics of the aldehyde. The results are interesting for both their synthetic importance and the mechanism of the formation of the products. Not only the products obtained and the recognition power are reported, but also some characteristics of its mechanism are analyzed. The results clearly show that the enzyme is efficiently prepared, purified, and stored, that it recognizes many different substrates, and that the products depend on the substrate electronic nature.

  5. Enantioselective aldol reaction between isatins and cyclohexanone catalyzed by amino acid sulphonamides.

    PubMed

    Wang, Jun; Liu, Qi; Hao, Qing; Sun, Yanhua; Luo, Yiming; Yang, Hua

    2015-04-01

    Sulphonamides derived from primary α-amino acid were successfully applied to catalyze the aldol reaction between isatin and cyclohexanone under neat conditions. More interestingly, molecular sieves, as privileged additives, were found to play a vital role in achieving high enantioselectivity. Consequently, high yields (up to 99%) along with good enantioselectivities (up to 92% ee) and diastereoselectivities (up to 95:5 dr) were obtained. In addition, this reaction was also conveniently scaled up, demonstrating the applicability of this protocol.

  6. Development of chiral catalysts for Mukaiyama aldol reactions in aqueous media.

    PubMed

    Kitanosono, Taku; Kobayashi, Shū

    2014-02-01

    Since the discovery of the Mukaiyama aldol reaction in 1973, tremendous efforts have been made to develop a definitive catalyst that catalyzes asymmetric Mukaiyama aldol reactions under mild conditions with broad substrate tolerance. Forty years later, an exhaustive search for a water-compatible Lewis acid was able to uncover the hidden potential of iron(II) and bismuth(III), leading to the establishment of broadly applicable and versatile catalytic systems for asymmetric Mukaiyama aldol reactions in aqueous media. The ternary catalytic system was able to expand the substrate generality considerably as the most distinguished catalyst ever reported. The superiority of this methodology over conventional methods has also been demonstrated in terms of high catalytic activity, simplicity of experimental procedures, and a wide substrate range including aqueous aldehydes, for which the stereochemistry had been regarded as difficult to control. Furthermore, a facile synthesis of the chiral ligand underscores its versatility. The reaction did not proceed at all without use of water. In the postulated mechanism, water plays prominent roles in: (1) producing the active metal complexes with a high water-exchange rate constant (3.2 × 10(6)) to activate substrates effectively and to catalyze the reaction through a rapid proton transfer on the order of picoseconds; (2) facilitating the catalytic turnover with simultaneous desilylation as direct access to aldol adducts or facile recovery of active metal complexes; and (3) stabilizing rigid transition states composed of metal complexes and reactants through entropy-driven aggregation derived from the highest cohesive energy density. PMID:24449534

  7. A practical synthesis of (+)-discodermolide and analogues: fragment union by complex aldol reactions.

    PubMed

    Paterson, I; Florence, G J; Gerlach, K; Scott, J P; Sereinig, N

    2001-10-01

    A practical stereocontrolled synthesis of (+)-discodermolide (1) has been completed in 10.3% overall yield (23 steps longest linear sequence). The absolute stereochemistry of the C(1)-C(6) (7), C(9)-C(16) (8), and C(17)-C(24) (9) subunits was established via substrate-controlled, boron-mediated, aldol reactions of the chiral ethyl ketones 10, 11, and 12. Key fragment coupling reactions were a lithium-mediated, anti-selective, aldol reaction of aryl ester 8 (under Felkin-Anh induction from the aldehyde component 9), followed by in situ reduction to produce the 1,3-diol 40, and a (+)-diisopinocampheylboron chloride-mediated aldol reaction of methyl ketone 7 (overturning the inherent substrate induction from the aldehyde component 52) to give the (7S)-adduct 58. The flexibility of our overall strategy is illustrated by the synthesis of a number of diastereomers and structural analogues of discodermolide, which should serve as valuable probes for structure-activity studies.

  8. Exploring the aldol reaction using catalytic antibodies and "on water" organocatalysts from QM/MM calculations.

    PubMed

    Armacost, Kira; Acevedo, Orlando

    2014-01-01

    The aldol reaction between benzaldehyde and acetone has been investigated using QM/MM Monte Carlo calculations and free-energy perturbation theory to determine the origin of the enhanced rates and enantioselectivities (% ee) derived from an enamine-based catalytic antibody 33F12 and a chiral organocatalyst. Electrostatic stabilization of the general acid/base TyrL36 by TrpH103, SerH100, and AsnL34 enabled the 33F12 active site to exclusively adopt an si-face benzaldehyde orientation for C-C bond formation with the LysH93-enamine. Whereas preorganization was responsible for the exclusive (S)-aldol product in the antibody, the organocatalyst featuring a chiral diphenyl amino alcohol moiety instead derived its preferred (R)-aldol product from an interplay between sterics and electronic stabilization. The si-face benzaldehyde conformation had unfavorable interactions with the organocatalyst in contrast to the re-face. Gas-phase calculations predicted a 73% ee; however, solution boosted the % ee values despite similar reaction geometries. An "on water" environment, defined as a reaction that proceeds in an aqueous organic emulsion, yielded a computed 94% ee (exptl 93% ee) compared to a calculated 87% ee in "neat" acetone (exptl 85% ee). Specific hydrogen bonding between the interfacial waters and an amide oxygen on the catalyst was found to control the % ee. A more compact si-face transition structure reduced solvent accessibility to the amide oxygen with a "closed state" steric barrier compared to an "open state" for the re-face. New insight into the synthetically important aldol reaction and state-of-the-art methodology is presented herein.

  9. Organocatalytic enantioselective tandem aldol-cyclization reaction of α-isothiocyanato imides and activated carbonyl compounds

    PubMed Central

    Guang, Jie; Zhao, Cong-Gui

    2011-01-01

    The organocatalytic enantioselective tandem aldol-cyclization reactions of α-isothiocyanato imides and activated carbonyl compounds, such as isatins, an α-ketolactone and a 1,2-dione, have been studied with cinchona alkaloid-derived thiourea-catalysts. This methodology provided an easy way to access enantiomerically enriched spirobicyclic thiocarbamates with high yields and good to excellent stereoselectivity, which have been demonstrated to be useful precursors for the synthesis of biologically active molecules. PMID:21921975

  10. A One-Pot Tandem Strategy in Catalytic Asymmetric Vinylogous Aldol Reaction of Homoallylic Alcohols.

    PubMed

    Hou, Xufeng; Jing, Zhenzhong; Bai, Xiangbin; Jiang, Zhiyong

    2016-01-01

    Reported is a rationally-designed one-pot sequential strategy that allows homoallylic alcohols to be employed in a catalytic, asymmetric, direct vinylogous aldol reaction with a series of activated acyclic ketones, including trifluoromethyl ketones, γ-ketoesters, and α-keto phosphonates, in high yields (up to 95%) with excellent regio- and enantio-selectivity (up to 99% ee). This modular combination, including Jones oxidation and asymmetric organocatalysis, has satisfactory compatibility and reliability even at a 20 mmol scale, albeit without intermediary purification. PMID:27355935

  11. Ligand-Promoted, Boron-Mediated Chemoselective Carboxylic Acid Aldol Reaction.

    PubMed

    Nagai, Hideoki; Morita, Yuya; Shimizu, Yohei; Kanai, Motomu

    2016-05-01

    The first carboxylic acid selective aldol reaction mediated by boron compounds and a mild organic base (DBU) was developed. Inclusion of electron-withdrawing groups in the amino acid derivative ligands reacted with BH3·SMe2 forms a boron promoter with increased Lewis acidity at the boron atom and facilitated the carboxylic acid selective enolate formation, even in the presence of other carbonyl groups such as amides, esters, ketones, or aliphatic aldehydes. The remarkable ligand effect led to the broad substrate scope including biologically relevant compounds. PMID:27104352

  12. One-Pot Domino Aldol Reaction of Indium Enolates Affording 6-Deoxy-α-D,L-altropyranose Derivatives: Synthesis, Mechanism, and Computational Results.

    PubMed

    Cinar, M Emin; Schmittel, Michael

    2015-08-21

    The domino-aldol-aldol-hemiacetal-reaction cascade of indium and other group 13 metal enolates furnished 6-deoxy-α-D,L-altropyranose derivatives in up to 99% yield under thermodynamic control. At lower temperature and thus under kinetic control, the reaction proceeded in a much less diastereoselective manner. The changeover from kinetic to thermodynamic control operating in this multistep domino-aldol-aldol-hemiacetal protocol was used for probing the efficiency of DFT computations. Calculations at the B3LYP/6-31G(d)/LANL2DZ level provided a mechanistic picture in full agreement with the experimental outcome. PMID:26258596

  13. One-Pot Domino Aldol Reaction of Indium Enolates Affording 6-Deoxy-α-D,L-altropyranose Derivatives: Synthesis, Mechanism, and Computational Results.

    PubMed

    Cinar, M Emin; Schmittel, Michael

    2015-08-21

    The domino-aldol-aldol-hemiacetal-reaction cascade of indium and other group 13 metal enolates furnished 6-deoxy-α-D,L-altropyranose derivatives in up to 99% yield under thermodynamic control. At lower temperature and thus under kinetic control, the reaction proceeded in a much less diastereoselective manner. The changeover from kinetic to thermodynamic control operating in this multistep domino-aldol-aldol-hemiacetal protocol was used for probing the efficiency of DFT computations. Calculations at the B3LYP/6-31G(d)/LANL2DZ level provided a mechanistic picture in full agreement with the experimental outcome.

  14. Lewis base activation of Lewis acids: catalytic, enantioselective vinylogous aldol addition reactions.

    PubMed

    Denmark, Scott E; Heemstra, John R

    2007-07-20

    The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of alpha,beta-unsaturated ketone-, 1,3-diketone-, and alpha,beta-unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of gamma-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although alpha,beta-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, alpha,beta-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.

  15. Synthesis and Characterization of Aldol Condensation Products from Unknown Aldehydes and Ketones: An Inquiry-Based Experiment in the Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Angelo, Nicholas G.; Henchey, Laura K.; Waxman, Adam J.; Canary, James W.; Arora, Paramjit S.; Wink, Donald

    2007-01-01

    An experiment for the undergraduate chemistry laboratory in which students perform the aldol condensation on an unknown aldehyde and an unknown ketone is described. The experiment involves the use of techniques such as TLC, column chromatography, and recrystallization, and compounds are characterized by [to the first power]H NMR, GC-MS, and FTIR.…

  16. Improvement on the catalytic performance of Mg-Zr mixed oxides for furfural-acetone aldol condensation by supporting on mesoporous carbons.

    PubMed

    Faba, Laura; Díaz, Eva; Ordóñez, Salvador

    2013-03-01

    A new procedure for improving the performance of the most common catalysts used in aqueous-phase aldol condensation (Mg-Zr mixed oxides) reactions is presented. This reaction is of interest for upgrading carbohydrate feedstocks. The procedure involves supporting Mg-Zr oxides on non-microporous carbonaceous materials, such as carbon nanofibers (CNFs) or high-surface-area graphites (HSAGs), using either incipient wetness or coprecipitation procedures. The use of HSAGs together with the coprecipitation method provides the best performance. Results obtained for the cross-condensation of acetone and furfural at 323 K reveal that the catalyst performance is greatly improved compared to the bulk oxides (96.5 % conversion vs. 81.4 % with the bulk oxide; 87.8 % selectivity for C13 and C8 adducts vs. 76.2 % with the bulk oxide). This difference is even more prominent in terms of rates per catalytically active basic site (four and seven times greater for C8 and C13 adducts, respectively). The improved performance is explained in terms of a more appropriate basic site distribution and by greater interaction of the reactants with the carbon surface. In addition, deactivation behavior of the catalyst is improved by tuning the morphology of the carbonaceous support. An important enhancement of the catalytic stability can be obtained selecting a HSAG with an appropriate pore diameter. With HSAG100 the activity decreased by less than 20 % between successive reaction cycles and the selectivity for the condensation products remained almost unaltered. The decrease is greater than 80 % for the bulk oxides tested at these conditions, with important increases in the selectivity for by-product formation. PMID:23362138

  17. Evidence for the formation of an enamine species during aldol and Michael-type addition reactions promiscuously catalyzed by 4-oxalocrotonate tautomerase.

    PubMed

    Poddar, Harshwardhan; Rahimi, Mehran; Geertsema, Edzard M; Thunnissen, Andy-Mark W H; Poelarends, Gerrit J

    2015-03-23

    The enzyme 4-oxalocrotonate tautomerase (4-OT), which has a catalytic N-terminal proline residue (Pro1), can promiscuously catalyze various carbon-carbon bond-forming reactions, including aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde, and Michael-type addition of acetaldehyde to a wide variety of nitroalkenes to yield valuable γ-nitroaldehydes. To gain insight into how 4-OT catalyzes these unnatural reactions, we carried out exchange studies in D2 O, and X-ray crystallography studies. The former established that H-D exchange within acetaldehyde is catalyzed by 4-OT and that the Pro1 residue is crucial for this activity. The latter showed that Pro1 of 4-OT had reacted with acetaldehyde to give an enamine species. These results provide evidence of the mechanism of the 4-OT-catalyzed aldol and Michael-type addition reactions in which acetaldehyde is activated for nucleophilic addition by Pro1-dependent formation of an enamine intermediate.

  18. Expedient synthesis of C-aryl carbohydrates by consecutive biocatalytic benzoin and aldol reactions.

    PubMed

    Hernández, Karel; Parella, Teodor; Joglar, Jesús; Bujons, Jordi; Pohl, Martina; Clapés, Pere

    2015-02-16

    The introduction of aromatic residues connected by a C-C bond into the non-reducing end of carbohydrates is highly significant for the development of innovative structures with improved binding affinity and selectivity (e.g., C-aril-sLex). In this work, an expedient asymmetric "de novo" synthetic route to new aryl carbohydrate derivatives based on two sequential stereoselectively biocatalytic carboligation reactions is presented. First, the benzoin reaction of aromatic aldehydes to dimethoxyacetaldehyde is conducted, catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I. Then, the α-hydroxyketones formed are reduced by using NaBH4 yielding the anti diol. After acetal hydrolysis, the aldol addition of dihydroxyacetone, hydroxyacetone, or glycolaldehyde catalyzed by the stereocomplementary D-fructose-6-phosphate aldolase and L-rhamnulose-1-phosphate aldolase is performed. Both aldolases accept unphosphorylated donor substrates, avoiding the need of handling the phosphate group that the dihydroxyacetone phosphate-dependent aldolases require. In this way, 6-C-aryl-L-sorbose, 6-C-aryl-L-fructose, 6-C-aryl-L-tagatose, and 5-C-aryl-L-xylose derivatives are prepared by using this methodology.

  19. 1,6-asymmetric induction in boron-mediated aldol reactions: application to a practical total synthesis of (+)-discodermolide.

    PubMed

    Paterson, Ian; Delgado, Oscar; Florence, Gordon J; Lyothier, Isabelle; Scott, Jeremy P; Sereinig, Natascha

    2003-01-01

    By relying solely on substrate-based stereocontrol, a practical total synthesis of the microtubule-stabilizing anticancer agent (+)-discodermolide has been realized. This exploits a novel aldol bond construction with 1,6-stereoinduction from the boron enolate of (Z)-enone 3 in addition to aldehyde 2. The 1,3-diol 7 is employed as a common building block for the C(1)-C(5), C(9)-C(16), and C(17)-C(24) subunits. [reaction--see text

  20. Direct Access to 6/5/7/5- and 6/7/5/5-Fused Tetracyclic Triterpenoids via Divergent Transannular Aldol Reaction of Lanosterol-Derived Diketone

    PubMed Central

    Ignatenko, Vasily A.; Han, Yong

    2013-01-01

    In an effort to access biologically relevant chemical space, a complex natural product-derived non-symmetrical diketone was prepared as a substrate for divergent transannular aldol reactions. The use of common aldol conditions resulted in predominant syn-addition via pathway a, while the use of alumina provided access to the anti-adduct. Screening of a range of Lewis acids of varying strength unexpectedly resulted in the formation of aldol products with 6/7/5/5-fused molecular skeleton via pathway b. PMID:24161022

  1. Highly Stereoselective and Scalable anti-Aldol Reactions using N-(p-dodecylphenylsulfonyl)-2-Pyrrolidinecarboxamide: Scope and Origins of Stereoselectivities

    PubMed Central

    Yang, Hua; Mahapatra, Subham; Cheong, Paul Ha-Yeon; Carter, Rich G.

    2010-01-01

    A highly enantio- and diastereoselective anti-aldol process (up to >99% ee, >99:1 dr) catalyzed by a proline mimetic – N-(p-dodecylphenylsulfonyl)-2-pyrrolidinecarboxamide – has been developed. Catalyst loading as low as 2 mol% can be employed. Use of industry-friendly solvents for this transformation as well as neat reaction conditions have been demonstrated. The scope of this transformation on a range of aldehydes and ketones is explored. Density Functional Theory computations reveal that the origins of enhanced diastereoselectivity is due to the presence of non-classical hydrogen bonds between the sulfonamide, the electrophile and the catalyst enamine that favor the major Anti-Re aldol TS in the Houk-List model. PMID:20932013

  2. Characterization and mechanism insight of accelerated catalytic promiscuity of Sulfolobus tokodaii (ST0779) peptidase for aldol addition reaction.

    PubMed

    Li, Rong; Perez, Bianca; Jian, Hui; Jensen, Mads Mørk; Gao, Renjun; Dong, Mingdong; Glasius, Marianne; Guo, Zheng

    2015-11-01

    A novel peptidase from thermophilic archaea Sulfolobus tokodaii (ST0779) is examined for its catalytic promiscuity of aldol addition, which shows comparable activity as porcine pancreatic lipase (PPL, one of the best enzymes identified for biocatalytic aldol addition) at 30 °C but much accelerated activity at elevated temperature. The molecular catalytic efficiency kcat/Km (M(-1) s(-1)) of this thermostable enzyme at 55 °C adds up to 140 times higher than that of PPL at its optimum temperature 37 °C. The fluorescence quenching analysis depicts that the binding constants of PPL are significantly higher than those of ST0779, and their numbers of binding sites show opposite temperature dependency. Thermodynamic parameters estimated by fluorescence quenching analysis unveil distinctly different substrate-binding modes between PPL and ST0779: the governing binding interaction between PPL and substrates is hydrophobic force, while the dominating substrate-binding forces for ST0779 are van der Waals and H-bonds interactions. A reasonable mechanism for ST0779-catalyzed aldol reaction is proposed based on kinetic study, spectroscopic analysis, and molecular stereostructure simulation. This work represents a successful example to identify a new enzyme for catalytic promiscuity, which demonstrates a huge potential to discover and exploit novel biocatalyst from thermophile microorganism sources. PMID:26169629

  3. Prebiotic condensation reactions using cyanamide

    NASA Technical Reports Server (NTRS)

    Sherwood, E.; Nooner, D. W.; Eichberg, J.; Epps, D. E.; Oro, J.

    1978-01-01

    Condensation reactions in cyanamide, 4-amino-5-imidazole-carboxamide and cyanamide, imidazole systems under dehydrating conditions at moderate temperatures (60 to 100 deg C) were investigated. The cyanamide, imidazole system was used for synthesis of palmitoylglycerols from ammonium palmitate and glycerol. With the addition of deoxythymidine to the former system, P1, P2-dideoxythymidine 5 prime-phosphate was obtained; the same cyanamide, 4-amino-5-imidazole-carboxamide system was used to synthesize deoxythymidine oligonucleotides using deoxythymidine 5 prime-phosphate and deoxythymidine 5 prime-triphosphate, and peptides using glycine, phenylalanine or isoleucine with adenosine 5 prime-triphosphate. The pH requirements for these reactions make their prebiotic significance questionable; however, it is conceivable that they could occur in stable pockets of low interlayer acidity in a clay such as montmorillonite.

  4. Studies on self-assembly phenomena of hydrophilization of microporous polypropylene membrane by acetone aldol condensation products: New separator for high-power alkaline batteries

    NASA Astrophysics Data System (ADS)

    Ciszewski, Aleksander; Rydzyńska, Bożena

    Commercial hydrophobic polypropylene (PP) membranes were modified by a novel chemical method. This procedure consists of two steps. In the first step, the virgin hydrophobic PP membrane is saturated with acetone; in the second step, the filled membrane is dipped in aqueous KOH solution (d = 1.28 g cm -3), i.e. in the electrolyte typical for the nickel-cadmium cell. This two-step procedure starts the aldol condensation process of acetone and its products accumulated and adsorbed onto walls of micropores make the membrane hydrophilic. The presented method provided the hydrophilic PP membrane, persistent and soaked with KOH solution with electrolytic resistance of 23-29 mΩ cm 2. This result was compared with the data obtained with commercial hydrophilic membranes: Celgard 3501 and Cellophane. The aldol condensation process of acetone was monitored using the HPLC-ES-MS technique, and modified PP membranes were evaluated by FT-IR and SEM measurements. With the above-mentioned membrane as a separator, nickel-cadmium cells showed good high-rate performance.

  5. Tandem carbon-carbon bond insertion and intramolecular aldol reaction of benzyne with aroylacetones: novel formation of 4,4'-disubstituted 1,1'-binaphthols.

    PubMed

    Okuma, Kentaro; Itoyama, Ryoichi; Sou, Ayumi; Nagahora, Noriyoshi; Shioj, Kosei

    2012-11-21

    An efficient route to 4-aryl-2-naphthols from arynes and aroylacetones was developed by carbon-carbon bond insertion followed by an intramolecular aldol reaction and dehydration. Benzyne derived from 2-(trimethylsilyl)phenyl triflate reacted with benzoylacetones in refluxing acetonitrile to give 4-aryl-2-naphthols and 3-aryl-1-naphthols.

  6. CALIX[6]ARENE DERIVATIVES BEARING SULFONATE AND ALKYL GROUPS AS SURFACTANTS IN SC(OTF)3-CATALYZED MUKAIYAMA ALDOL REACTIONS IN WATER. (R822668)

    EPA Science Inventory

    Abstract

    Amphiphilic calix[6]arene derivatives 1a¯b were found to be efficient surfactants for Sc(OTf)3-catalyzed Mukaiyama aldol reaction of silyl enol ethers with aldehydes in water. The results indicated t...

  7. THE EFFECTS OF AROMATIC AND ALIPHATIC ANIONIC SURFACTANTS ON SC(OTF)3-CATALYZED MUKAIYAMA ALDOL REACTION IN WATER. (R822668)

    EPA Science Inventory

    Abstract

    Aromatic (2c and 2d) and aliphatic (2a and 2b) anionic surfactants were employed in Sc(OTf)3-catalyzed aldol reactions of some labile silyl enol ethers (3a and

  8. Asymmetric assembly of aldose carbohydrates from formaldehyde and glycolaldehyde by tandem biocatalytic aldol reactions

    NASA Astrophysics Data System (ADS)

    Szekrenyi, Anna; Garrabou, Xavier; Parella, Teodor; Joglar, Jesús; Bujons, Jordi; Clapés, Pere

    2015-09-01

    The preparation of multifunctional chiral molecules can be greatly simplified by adopting a route via the sequential catalytic assembly of achiral building blocks. The catalytic aldol assembly of prebiotic compounds into stereodefined pentoses and hexoses is an as yet unmet challenge. Such a process would be of remarkable synthetic utility and highly significant with regard to the origin of life. Pursuing an expedient enzymatic approach, here we use engineered D-fructose-6-phosphate aldolase from Escherichia coli to prepare a series of three- to six-carbon aldoses by sequential one-pot additions of glycolaldehyde. Notably, the pertinent selection of the aldolase variant provides control of the sugar size. The stereochemical outcome of the addition was also altered to allow the synthesis of L-glucose and related derivatives. Such engineered biocatalysts may offer new routes for the straightforward synthesis of natural molecules and their analogues that circumvent the intricate enzymatic pathways forged by evolution.

  9. l-Isoleucine in a Choline Chloride/Ethylene Glycol Deep Eutectic Solvent: A Reusable Reaction Kit for the Asymmetric Cross-Aldol Carboligation.

    PubMed

    Fanjul-Mosteirín, Noé; Concellón, Carmen; Del Amo, Vicente

    2016-09-01

    l-Isoleucine is able to catalyze the cross-aldol reaction between cyclohexanone and aromatic aldehydes in a deep eutectic solvent consisting in choline chloride and ethylene glycol, rendering products with high diatereo- and enantioselectivity. This protocol is straightforward and green: the organocatalyst and the reaction medium can be recycled up to five times, allowing the preparation of different substrates with a single load of solvent and catalyst.

  10. l-Isoleucine in a Choline Chloride/Ethylene Glycol Deep Eutectic Solvent: A Reusable Reaction Kit for the Asymmetric Cross-Aldol Carboligation.

    PubMed

    Fanjul-Mosteirín, Noé; Concellón, Carmen; Del Amo, Vicente

    2016-09-01

    l-Isoleucine is able to catalyze the cross-aldol reaction between cyclohexanone and aromatic aldehydes in a deep eutectic solvent consisting in choline chloride and ethylene glycol, rendering products with high diatereo- and enantioselectivity. This protocol is straightforward and green: the organocatalyst and the reaction medium can be recycled up to five times, allowing the preparation of different substrates with a single load of solvent and catalyst. PMID:27526718

  11. Concise Enantioselective Synthesis of Oxygenated Steroids via Sequential Copper(II)-Catalyzed Michael Addition/Intramolecular Aldol Cyclization Reactions.

    PubMed

    Cichowicz, Nathan R; Kaplan, Will; Khomutnyk, Yaroslav; Bhattarai, Bijay; Sun, Zhankui; Nagorny, Pavel

    2015-11-18

    A new scalable enantioselective approach to functionalized oxygenated steroids is described. This strategy is based on chiral bis(oxazoline) copper(II) complex-catalyzed enantioselective and diastereoselective Michael reactions of cyclic ketoesters and enones to install vicinal quaternary and tertiary stereocenters. In addition, the utility of copper(II) salts as highly active catalysts for the Michael reactions of traditionally unreactive β,β'-enones and substituted β,β'-ketoesters that results in unprecedented Michael adducts containing vicinal all-carbon quaternary centers is also demonstrated. The Michael adducts subsequently undergo base-promoted diastereoselective aldol cascade reactions resulting in the natural or unnatural steroid skeletons. The experimental and computational studies suggest that the torsional strain effects arising from the presence of the Δ(5)-unsaturation are key controlling elements for the formation of the natural cardenolide scaffold. The described method enables expedient generation of polycyclic molecules including modified steroidal scaffolds as well as challenging-to-synthesize Hajos-Parrish and Wieland-Miescher ketones.

  12. Concise Enantioselective Synthesis of Oxygenated Steroids via Sequential Copper(II)-Catalyzed Michael Addition/Intramolecular Aldol Cyclization Reactions

    PubMed Central

    Cichowicz, Nathan R.; Kaplan, Will; Khomutnyk, Yaroslav; Bhattarai, Bijay; Sun, Zhankui; Nagorny, Pavel

    2015-01-01

    A new scalable enantioselective approach to functionalized oxygenated steroids is described. This strategy is based on chiral bis(oxazoline) copper(II) complex-catalyzed enantioselective and diastereoselective Michael reactions of cyclic ketoesters and enones to install vicinal quaternary and tertiary stereocenters. In addition, the utility of copper(II) salts as highly active catalysts for the Michael reactions of traditionally unreactive ββ′-enones and substituted ββ′-ketoesters that results in unprecedented Michael adducts containing vicinal all-carbon quaternary centers is also demonstrated. The Michael adducts subsequently undergo base-promoted diastereoselective aldol cascade reactions resulting in the natural or unnatural steroid skeletons. The experimental and computational studies suggest that the torsional strain effects arising from the presence of the Δ5-unsaturation are key controling elements for the formation of the natural cardenolide scaffold. The described method enables expedient generation of polycyclic molecules including modified steroidal scaffolds as well as challenging-to-synthesize Hajos-Parrish and Wieland-Miescher ketones. PMID:26491886

  13. Origins of opposite syn-anti diastereoselectivities in primary and secondary amino acid-catalyzed intermolecular aldol reactions involving unmodified alpha-hydroxyketones.

    PubMed

    Fu, Aiping; Li, Hongliang; Yuan, Shuping; Si, Hongzong; Duan, Yunbo

    2008-07-18

    The effects of different amino acid catalysts on the stereoselectivity of the direct intermolecular aldol reactions between alpha-hydroxyketones and isobutyraldehyde or 4-nitrobenzaldehyde have been studied with the aid of density functional theory methods. The transition states of the crucial C-C bond-forming step with the enamine intermediate addition to the aldehyde for the proline and threonine-catalyzed asymmetric aldol reactions are reported. B3LYP/6-31+G** calculations provide a good explanation for the opposite syn vs anti diastereoselectivity of these two kinds of amino acid catalysts (anti-selectivity for the secondary cyclic amino acids proline, syn-selectivity for the acyclic primary amino acids like threonine). Calculated and observed diastereomeric ratio and enantiomeric excess values are in good agreement. PMID:18549281

  14. The role of synergic interaction in transition state formation for the aldol reaction on a metal oxide catalyst: a DFT investigation.

    PubMed

    An, Wei

    2015-09-21

    This contribution highlights an eight-membered ring transition state for the aldol reaction of propanal on O-terminated ZrO2(111) and CeO2(111) surfaces. The relative heights of activation barriers for α-H abstraction and nucleophilic addition are controlled by surface acid-base pair strength. We report the first theoretical evidence of an alternative to the Zimmerman-Traxler model.

  15. Regulated-stereoselective construction of thirteen stereogenic centers necessary for the frame of (+)-discodermolide, based on iterative Lewis acid-promoted aldol reactions.

    PubMed

    Kiyooka, Syun-ichi; Shahid, Kazi Abdus; Goto, Fumitaka; Okazaki, Momotoshi; Shuto, Yoshihiro

    2003-10-17

    The segments C(1)-C(13) and C(15)-C(21) containing the 13 stereogenic centers required for the frame of (+)-discodermolide were synthesized in good to excellent enantio- and diastereoselectivities from a common racemic aldehyde, derived from 2-methyl-1,3-propanediol. The enantioselective aldol reactions of the racemic aldehyde with a silylketene acetal, derived from ethyl 2-bromopropionate, in the presence of chiral oxazaborolidinones, prepared in situ with N-p-toluenesulfonyl-(R)- and -(S)-valine and BH(3).THF, proceeded under kinetic control to give the stereotriads with a high degree of enantioselectivity. Enantioselective (chiral borane) and diastereoselective (BF(3).OEt(2) and TiCl(4)) aldol reactions with the silylketene acetal, coupled with diastereoselective radical debrominations (Bu(3)SnH, Et(3)B, with or without MgBr(2)), were used iteratively. This aldol reaction strategy for the construction of the polypropionate frame dramatically shortened the steps needed for the construction of the final segments.

  16. Experimental evidence for chair-like transition states in aldol reactions of methyl ketone lithium enolates: stereoselective synthesis and utilization of a deuterium-labeled enolate as a probe of reaction stereochemistry.

    PubMed

    Liu, Christopher M; Smith, William J; Gustin, Darin J; Roush, William R

    2005-04-27

    Aldol reactions of methyl ketone lithium enolates proceed via chairlike Zimmerman-Traxler transition states with 7:1 to 50:1 preference over alternative, boatlike transition structures, as determined by studies involving the configurationally stable deuterium-labeled enol silane 18 as the lithium enolate precursor.

  17. Aldol reactions catalyzed by L-proline functionalized polymeric nanoreactors in water.

    PubMed

    Lu, Annhelen; Cotanda, Pepa; Patterson, Joseph P; Longbottom, Deborah A; O'Reilly, Rachel K

    2012-10-01

    The use of functional core-shell micelles as asymmetric catalytic nanoreactors for organic reactions in water is presented. An unprecedented increase in rate of reaction was achieved, which is proposed to be associated with the ability of the nanostructures to effectively concentrate the reagents in the catalytically active micelle core.

  18. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 2: aldol, Mannich addition reactions, deracemization and (S) to (R) interconversion of α-amino acids.

    PubMed

    Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim

    2013-11-01

    This review provides a comprehensive treatment of literature data dealing with asymmetric synthesis of α-amino-β-hydroxy and α,β-diamino acids via homologation of chiral Ni(II) complexes of glycine Schiff bases using aldol and Mannich-type reactions. These reactions proceed with synthetically useful chemical yields and thermodynamically controlled stereoselectivity and allow direct introduction of two stereogenic centers in a single operation with predictable stereochemical outcome. Furthermore, new application of Ni(II) complexes of α-amino acids Schiff bases for deracemization of racemic α-amino acids and (S) to (R) interconversion providing additional synthetic opportunities for preparation of enantiomerically pure α-amino acids, is also reviewed. Origin of observed diastereo-/enantioselectivity in the aldol, Mannich-type and deracemization reactions, generality and limitations of these methodologies are critically discussed.

  19. Enantio- and Diastereoselective Synthesis of syn-β-Hydroxy-α-Vinyl Carboxylic Esters via Reductive Aldol Reactions of Ethyl Allenecarboxylate with 10-TMS-9-Borabicyclo[3.3.2]decane and DFT Analysis of the Hydroboration Pathway

    PubMed Central

    Kister, Jeremy; Ess, Daniel H.

    2013-01-01

    An enantio- and diastereoselective synthesis of syn-β-hydroxy-α-vinyl carboxylate esters 3 via the reductive aldol reaction of ethyl allenecarboxylate (2) with 10-trimethylsilyl-9-borabicyclo[3.3.2]decane (1R, Soderquist’s borane) has been developed. Density functional theory calculations suggest that the allene hydroboration involves the 1,4-reduction of 2 with the chiral borane 1R, leading directly to dienolborinate Z-(O)-8a. PMID:24138187

  20. Detonation Reaction Zones in Condensed Explosives

    NASA Astrophysics Data System (ADS)

    Tarver, Craig M.

    2006-07-01

    Experimental measurements using nanosecond time resolved embedded gauges and laser interferometric techniques, combined with Non-Equilibrium Zeldovich - von Neumann - Doling (NEZND) theory and Ignition and Growth reactive flow hydrodynamic modeling, have revealed the average pressure/particle velocity states attained in reaction zones of self-sustaining detonation waves in several solid and liquid explosives. The time durations of these reaction zone processes are discussed for explosives based on pentaerythritol tetranitrate (PETN), nitromethane, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), triaminitrinitrobenzene(TATB) and trinitrotoluene (TNT).

  1. Detonation Reaction Zones in Condensed Explosives

    SciTech Connect

    Tarver, C M

    2005-07-14

    Experimental measurements using nanosecond time resolved embedded gauges and laser interferometric techniques, combined with Non-Equilibrium Zeldovich--von Neumann--Doring (NEZND) theory and Ignition and Growth reactive flow hydrodynamic modeling, have revealed the average pressure/particle velocity states attained in reaction zones of self-sustaining detonation waves in several solid and liquid explosives. The time durations of these reaction zone processes is discussed for explosives based on pentaerythritol tetranitrate (PETN), nitromethane, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), triaminitrinitrobenzene(TATB) and trinitrotoluene (TNT).

  2. Detonation Reaction Zones in Condensed Explosives

    NASA Astrophysics Data System (ADS)

    Tarver, Craig

    2005-07-01

    Experimental measurements using nanosecond time resolved embedded gauges and laser interferometric techniques, combined with Non-Equilibrium Zeldovich -- von Neumann -- Doring (NEZND) theory and reactive flow hydrodynamic modeling, have revealed the average pressure/particle velocity states attained in reaction zones of self-sustaining detonation waves in several solid and liquid explosives. The time durations of these reaction zone processes is discussed for nitromethane, HMX, TATB and PETN. Progress in measuring and modeling the complex three-dimensional structural of these detonation waves is also discussed. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  3. Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

    PubMed Central

    Engelen, Bernward; Panthöfer, Martin; Deiseroth, Hans-Jörg; Schlirf, Jens

    2016-01-01

    Summary A one-pot transformation, which involves the reaction of ketones with aldehydes in the presence of metal halides to furnish tetrahydro-2H-pyran-2,4-diols in a highly diastereoselective manner, is investigated thoroughly by experiments and computations. The reaction was also successfully implemented on a flow micro reactor system. PMID:27340472

  4. Synthesis of two subunits of the macrolide domain of the immunosuppressive agent sanglifehrin a and assembly of a macrolactone precursor. application of masamune anti-aldol condensation.

    PubMed

    Suttisintong, Khomson; White, James D

    2015-02-20

    Asymmetric anti-aldol coupling of a norephedrine-derived ester with an α-chiral aldehyde was used to synthesize a carboxylic acid representing the C13-C19 segment of the macrocyclic domain present in the immunosuppressive agent sanglifehrin A. Felkin addition set configuration at the C14-C17 stereotetrad in this unit in which hydroxyl functions at C15 and C17 were masked as an internal ketal. The carboxyl group of this segment was coupled to the N-terminus of the tripeptide portion (C1-N12) of sanglifehrin A macrolactone to assemble the C1-C19 domain. Synthesis of the C20-C25 subunit of sanglifehrin A containing a (23S) alcohol was completed via asymmetric allylation of (E)-3-iodo-2-methylprop-2-enal followed by oxidative cleavage of the terminal vinyl appendage and a Takai olefination with pinacol dichloromethylboronate. Esterification of this alcohol with a C1-C19 carboxylic acid furnished an open C1-C25 macrolactone precursor, but this substance failed to undergo macrocyclization via intramolecular Suzuki-Miyaura coupling. PMID:25584782

  5. The Mukaiyama aldol reaction of in situ generated nitrosocarbonyl compounds: selective C-N bond formation and N-O bond cleavage in one-pot for α-amination of ketones.

    PubMed

    Ramakrishna, Isai; Grandhi, Gowri Sankar; Sahoo, Harekrishna; Baidya, Mahiuddin

    2015-09-21

    A practical protocol for the α-amination of ketones (up to 99% yield) has been developed via the Mukaiyama aldol reaction of in situ generated nitrosocarbonyl compounds. The reaction with silyl enol ethers having a disilane (-SiMe2TMS) backbone proceeded not only with perfect N-selectivity but concomitant N-O bond cleavage was also accomplished. Such a cascade of C-N bond formation and N-O bond cleavage in a single step was heretofore unknown in the field of nitrosocarbonyl chemistry. A very high diastereoselectivity (dr = 19 : 1) was accomplished using (-)-menthol derived chiral nitrosocarbonyl compounds. PMID:26245149

  6. A Multistep Organocatalysis Experiment for the Undergraduate Organic Laboratory: An Enantioselective Aldol Reaction Catalyzed by Methyl Prolinamide

    ERIC Educational Resources Information Center

    Wade, Edmir O.; Walsh, Kenneth E.

    2011-01-01

    In recent years, there has been an explosion of research concerning the area of organocatalysis. A multistep capstone laboratory project that combines traditional reactions frequently found in organic laboratory curriculums with this new field of research is described. In this experiment, the students synthesize a prolinamide-based organocatalyst…

  7. Computational elucidation of the origins of reactivity and selectivity in non-aldol aldol rearrangements of cyclic epoxides.

    PubMed

    Wang, Hao; Houk, K N; Allen, Damian A; Jung, Michael E

    2011-06-17

    The non-aldol aldol reaction of the isomeric epoxy silyl ethers is controlled by the conformation of the transition states leading to an internal hydride shift. One isomer rearranges to the β-silyloxy ketone whereas the other isomer gives a β-elimination product. Theoretical calculations show that the substrates with substituents that favor the formation of the chairlike transition state rearrange normally while those that do not undergo elimination instead. PMID:21568276

  8. Modeling the Reactions of Energetic Materials in the Condensed Phase

    SciTech Connect

    Fried, L E; Manaa, M R; Lewis, J P

    2003-12-03

    High explosive (HE) materials are unique for having a strong exothermic reactivity, which has made them desirable for both military and commercial applications. Although the history of HE materials is long, condensed-phase properties are poorly understood. Understanding the condensed-phase properties of HE materials is important for determining stability and performance. Information regarding HE material properties (for example, the physical, chemical, and mechanical behaviors of the constituents in plastic-bonded explosive, or PBX, formulations) is necessary in efficiently building the next generation of explosives as the quest for more powerful energetic materials (in terms of energy per volume) moves forward. In addition, understanding the reaction mechanisms has important ramifications in disposing of such materials safely and cheaply, as there exist vast stockpiles of HE materials with corresponding contamination of earth and groundwater at these sites, as well as a military testing sites The ability to model chemical reaction processes in condensed phase energetic materials is rapidly progressing. Chemical equilibrium modeling is a mature technique with some limitations. Progress in this area continues, but is hampered by a lack of knowledge of condensed phase reaction mechanisms and rates. Atomistic modeling is much more computationally intensive, and is currently limited to very short time scales. Nonetheless, this methodology promises to yield the first reliable insights into the condensed phase processes responsible for high explosive detonation. Further work is necessary to extend the timescales involved in atomistic simulations. Recent work in implementing thermostat methods appropriate to shocks may promise to overcome some of these difficulties. Most current work on energetic material reactivity assumes that electronically adiabatic processes dominate. The role of excited states is becoming clearer, however. These states are not accessible in perfect

  9. Stereodefined Acyclic Polysubstituted Silyl Ketene Aminals: Asymmetric Formation of Aldol Products with Quaternary Carbon Stereocenters.

    PubMed

    Nairoukh, Zackaria; Marek, Ilan

    2015-11-23

    The regio- and stereoselective formation of stereodefined polysubstituted silyl ketene aminals is easily achieved through selective combined carbometalation-oxidation-silylation reactions. These substrates are ideal candidates for Mukaiyama aldol reactions with aliphatic aldehydes as they give the aldol products with a quaternary carbon stereocenter α to the carbonyl groups in outstanding diastereoselectivities. PMID:26448575

  10. Stereodefined Acyclic Polysubstituted Silyl Ketene Aminals: Asymmetric Formation of Aldol Products with Quaternary Carbon Stereocenters.

    PubMed

    Nairoukh, Zackaria; Marek, Ilan

    2015-11-23

    The regio- and stereoselective formation of stereodefined polysubstituted silyl ketene aminals is easily achieved through selective combined carbometalation-oxidation-silylation reactions. These substrates are ideal candidates for Mukaiyama aldol reactions with aliphatic aldehydes as they give the aldol products with a quaternary carbon stereocenter α to the carbonyl groups in outstanding diastereoselectivities.

  11. Low-energy electron-induced reactions in condensed matter

    NASA Astrophysics Data System (ADS)

    Arumainayagam, Christopher R.; Lee, Hsiao-Lu; Nelson, Rachel B.; Haines, David R.; Gunawardane, Richard P.

    2010-01-01

    The goal of this review is to discuss post-irradiation analysis of low-energy (≤50 eV) electron-induced processes in nanoscale thin films. Because electron-induced surface reactions in monolayer adsorbates have been extensively reviewed, we will instead focus on low-energy electron-induced reactions in multilayer adsorbates. The latter studies, involving nanoscale thin films, serve to elucidate the pivotal role that the low-energy electron-induced reactions play in high-energy radiation-induced chemical reactions in condensed matter. Although electron-stimulated desorption (ESD) experiments conducted during irradiation have yielded vital information relevant to primary or initial electron-induced processes, we wish to demonstrate in this review that analyzing the products following low-energy electron irradiation can provide new insights into radiation chemistry. This review presents studies of electron-induced reactions in nanoscale films of molecular species such as oxygen, nitrogen trifluoride, water, alkanes, alcohols, aldehydes, ketones, carboxylic acids, nitriles, halocarbons, alkane and phenyl thiols, thiophenes, ferrocene, amino acids, nucleotides, and DNA using post-irradiation techniques such as temperature-programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), gel electrophoresis, and microarray fluorescence. Post-irradiation temperature-programmed desorption, in particular, has been shown to be useful in identifying labile radiolysis products as demonstrated by the first identification of methoxymethanol as a reaction product of methanol radiolysis. Results of post-irradiation studies have been used not only to identify radiolysis products, but also to determine the dynamics of electron-induced reactions. For example, studies of the radiolysis yield as a function of incident electron energy have shown that dissociative

  12. Towards catalyst compartimentation in combined chemo- and biocatalytic processes: immobilization of alcohol dehydrogenases for the diastereoselective reduction of a β-hydroxy ketone obtained from an organocatalytic aldol reaction.

    PubMed

    Rulli, Giuseppe; Heidlindemann, Marcel; Berkessel, Albrecht; Hummel, Werner; Gröger, Harald

    2013-11-01

    The alcohol dehydrogenases (ADHs) from Lactobacillus kefir and Rhodococcus sp., which earlier turned out to be suitable for a chemoenzymatic one-pot synthesis with organocatalysts, were immobilized with their cofactors on a commercially available superabsorber based on a literature known protocol. The use of the immobilized ADH from L. kefir in the reduction of acetophenone as a model substrate led to high conversion (>95%) in the first reaction cycle, followed by a slight decrease of conversion in the second reaction cycle. A comparable result was obtained when no cofactor was added although a water rich reaction media was used. The immobilized ADHs also turned out to be suitable catalysts for the diastereoselective reduction of an organocatalytically prepared enantiomerically enriched aldol adduct, leading to high conversion, diastereomeric ratio and enantioselectivity for the resulting 1,3-diols. However, at a lower catalyst and cofactor amount being still sufficient for biotransformations with "free" enzymes the immobilized ADH only showed high conversion and >99% ee for the first reaction cycle whereas a strong decrease of conversion was observed already in the second reaction cycle, thus indicating a significant leaching effect of catalyst and/or cofactor.

  13. Tandem ring-closing metathesis/isomerization reactions for the total synthesis of violacein.

    PubMed

    Petersen, Mette T; Nielsen, Thomas E

    2013-04-19

    A series of 5-substituted 2-pyrrolidinones was synthesized through a one-pot ruthenium alkylidene-catalyzed tandem RCM/isomerization/nucleophilic addition sequence. The intermediates resulting from RCM/isomerization showed reactivity toward electrophiles in aldol condensation reactions which provided a new entry for the total synthesis of the antileukemic natural product violacein.

  14. Dicarboxylic acid anhydride condensation with compounds containing active methylene groups. 4: Some 4-nitrophthalic anhydride condensation reactions

    NASA Technical Reports Server (NTRS)

    Oskaja, V.; Rotberg, J.

    1985-01-01

    By 4-nitrophthalic anhydride condensation with acetoacetate in acetic anhydride and triethylamine solution with subsequent breakdown of the intermediate condensation product, 5-nitroindanedione-1,3 was obtained. A 4-nitrophthalic anhydride with acetic anhydride, according to reaction conditions, may yield two products: in the presence of potassium acetate and at high temperatures 4-(or 5-)-nitro-2-acetylbenzoic acid is formed: in the presence of triethylamine and at room temperature 5-( or 6-)-nitrophthalic acetic acid is isolated. A 4-nitrophthalic anhydride and malonic acid in pyridine solution according to temperature yield either 5-( or 6-)-nitrophthalic acetic acid or 4-(or 5-)-nitro-2-acetylbenzoic acid.

  15. The effects of water on beta-D-xylose condensation reactions.

    PubMed

    Dong, Haitao; Nimlos, Mark R; Himmel, Michael E; Johnson, David K; Qian, Xianghong

    2009-07-30

    Car-Parrinello-based ab initio molecular dynamics simulations (CPMD) combined with metadynamics (MTD) simulations were used to determine the reaction energetics for the beta-D-xylose condensation reaction to form beta-1,4-linked xylobiose in a dilute acid solution. Protonation of the hydroxyl group on the xylose molecule and the subsequent breaking of the C-O bond were found to be the rate-limiting step during the xylose condensation reaction. Water and water structure was found to play a critical role in these reactions due to the proton's high affinity for water molecules. The reaction free energy and reaction barrier were determined using CPMD-MTD. We found that solvent reorganization due to proton partial desolvation must be taken into account in order to obtain the correct reaction activation energy. Our calculated reaction free energy and reaction activation energy compare well with available experimental results. PMID:19572686

  16. Enantioselective Multicomponent Condensation Reactions of Phenols, Aldehydes, and Boronates Catalyzed by Chiral Biphenols.

    PubMed

    Barbato, Keith S; Luan, Yi; Ramella, Daniele; Panek, James S; Schaus, Scott E

    2015-12-01

    Chiral diols and biphenols catalyze the multicomponent condensation reaction of phenols, aldehydes, and alkenyl or aryl boronates. The condensation products are formed in good yields and enantioselectivities. The reaction proceeds via an initial Friedel-Crafts alkylation of the aldehyde and phenol to yield an ortho-quinone methide that undergoes an enantioselective boronate addition. A cyclization pathway was discovered while exploring the scope of the reaction that provides access to chiral 2,4-diaryl chroman products, the core of which is a structural motif found in natural products. PMID:26576776

  17. Chemical Probes Allow Structural Insight into the Condensation Reaction of Nonribosomal Peptide Synthetases.

    PubMed

    Bloudoff, Kristjan; Alonzo, Diego A; Schmeing, T Martin

    2016-03-17

    Nonribosomal peptide synthetases (NRPSs) synthesize a vast variety of small molecules, including antibiotics, antitumors, and immunosuppressants. The NRPS condensation (C) domain catalyzes amide bond formation, the central chemical step in nonribosomal peptide synthesis. The catalytic mechanism and substrate determinants of the reaction are under debate. We developed chemical probes to structurally study the NRPS condensation reaction. These substrate analogs become covalently tethered to a cysteine introduced near the active site, to mimic covalent substrate delivery by carrier domains. They are competent substrates in the condensation reaction and behave similarly to native substrates. Co-crystal structures show C domain-substrate interactions, and suggest that the catalytic histidine's principle role is to position the α-amino group for nucleophilic attack. Structural insight provided by these co-complexes also allowed us to alter the substrate specificity profile of the reaction with a single point mutation.

  18. The possible role of solid surface area in condensation reactions during chemical evolution - Reevaluation

    NASA Technical Reports Server (NTRS)

    Lahav, N.; Chang, S.

    1976-01-01

    Using surface concentration and reaction rate as the main criteria for the feasibility of condensation reactions, four types of prebiotic environments were analyzed: (1) an ocean-sediment system, (2) a dehydrated lagoon bed produced by evaporation, (3) the surface of a frozen sediment, and (4) a fluctuating system where hydration (rainstorms, tidal variations, flooding) and dehydration (evaporation) take place in a cyclic manner. With the possible exception of nucleotides, low adsorption of organomonomers on sediment surfaces of a prebiotic ocean (pH 8) is expected, and significant condensation is considered unlikely. In dehydrated and frozen systems, high surface concentrations are probable and condensation is more likely. In fluctuating environments, condensation rates will be enhanced and the size distribution of the oligomers formed during dehydration may be influenced by a 'redistribution mechanism' in which adsorbed oligomers and monomers are desorbed and redistributed on the solid surface during the next hydration-dehydration cycle.

  19. Elemental sulfur disproportionation in the redox condensation reaction between o-halonitrobenzenes and benzylamines.

    PubMed

    Nguyen, Thanh Binh; Ermolenko, Ludmila; Retailleau, Pascal; Al-Mourabit, Ali

    2014-12-01

    The disproportionation of elemental sulfur at moderate temperatures is investigated in the redox condensation involving o-halonitrobenzenes 1 and benzylamines 2. As a redox moderator, elemental sulfur plays the dual role of both electron donor and acceptor, generating its lowest and highest oxidation states: S(-2) (sulfide equivalent) in benzothiazole 3 and S(+6) (sulfate equivalent) in sulfamate 4, and filling the electron gap of the global redox condensation process. Along with this process, a cascade of reactions of reduction of the nitro group of 1, oxidation of the aminomethyl group of 2, metal-free aromatic halogen substitution, and condensation finally led to 2-arylbenzothiazoles 3.

  20. Analytical solution for transient partitioning and reaction of a condensing vapor species in a droplet

    NASA Astrophysics Data System (ADS)

    Liu, Albert Tianxiang; Zaveri, Rahul A.; Seinfeld, John H.

    2014-06-01

    We present the exact analytical solution of the transient equation of gas-phase diffusion of a condensing vapor to, and diffusion and reaction in, an aqueous droplet. Droplet-phase reaction is represented by first-order chemistry. The solution facilitates study of the dynamic nature of the vapor uptake process as a function of droplet size, Henry's law coefficient, and first-order reaction rate constant for conversion in the droplet phase.

  1. Initial Reaction Steps in the Condensed-Phase Decomposition of Propellants

    SciTech Connect

    Melius, C F; Piqueras, M C

    2001-12-11

    Understanding the reaction mechanisms for the decomposition of energetic materials in the condensed phase is critical to our development of detailed kinetic models of propellant combustion. To date, the reaction mechanisms in the condensed phase have been represented by global, reactions. The detailed elementary reactions subsequent to the initial NO{sub 2} bond scissioning are not known. Using quantum chemical calculations, we have investigated the possible early steps in the decomposition of energetic materials that can occur in the condensed phase. We have used methylnitrate, methylnitramine, and nitroethane as prototypes for O-NO{sub 2}, N-NO{sub 2} and C-NO{sub 2} nitro compounds. We find the energetic radicals formed from the initial NO{sub 2} bond scissioning can be converted to unsaturated non-radical intermediates as an alternative to the unzipping of the energetic radical. We propose a new, prompt oxidation mechanism in which the trapped HONO can add back onto the energetic molecule. This produces oxidation products in the condensed phase that normally would not be produced until much later in the flame. We have shown that this prompt oxidation mechanism is a general feature of both nitramines and nitrate esters. The resulting HONO formed by the H-atom abstraction will be strongly influenced by the cage effect of the condensed phase. The applicability of this mechanism is demonstrated for decomposition of ethylnitrate, illustrating the importance of the cage effect in enabling this mechanism to occur at low temperatures.

  2. First observation of a mass independent isotopic fractionation in a condensation reaction

    NASA Technical Reports Server (NTRS)

    Thiemens, M. H.; Nelson, R.; Dong, Q. W.; Nuth, Joseph A., III

    1994-01-01

    Thiemens and Heidenreich (1983) first demonstrated that a chemically produced mass independent isotopic fractionation process could produce an isotopic composition which is identical to that observed in Allende inclusions. This raised the possibility that the meteoritic components could be produced by chemical, rather than nuclear processes. In order to develop a mechanistic model of the early solar system, it is important that relevant reactions be studied, particularly, those which may occur in the earliest condensation reactions. The isotopic results for isotopic fractionations associated with condensation processes are reported. A large mass independent isotopic fractionation is observed in one of the experiments.

  3. Condensed Matter Deuterium Cluster Target for Study of Pycnonuclear Reactions

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoling; George, Miley

    2009-11-01

    Fusion reactions have two main classes: thermonuclear and the pycnonuclear. Thermonuclear fusion occurs in low density high temperature plasmas, and is very sensitive to the ion temperature due to Columbic repulsion effects. As the density increases, the Columbic potential barrier is depressed by increased electron screening, allowing fusion at lower temperatures. This type of nuclear reaction is termed a pycnonuclear fusion and is the basis for astrophysical fusion. Ichimarua [1] proposed a laboratory study of this process using explosive mechanical compression of H/D to metallic densities, which would be extremely difficult to implement. Instead, our recent research suggests that metallic-like H/D ``clusters'' can be formed in dislocation loops of thin Palladium foils through electrochemical processes. [2] If this technique is used as a laser compression target, the compressed cluster density would allow study of pycnonuclear reactions. This provides a means of studying astrophysical fusion process, and could also lead to an important non-cryogenic ICF target. [2] [4pt] [1] S. Ichimaru, H. Kitamura. Phys. Plasmas, 6, 2649 (1999) [0pt] [2] G. Miley and X. Yang, Deuterium Cluster Target for Ultra-High Density, 18TH TOFE, San Francisco, CA Sep. 28 -- Oct. 2, 2008

  4. Contribution from 3 α-Condensed States to the Triple-Alpha Reaction

    NASA Astrophysics Data System (ADS)

    Katō, Kiyoshi; Kurokawa, Chie; Arai, Koji

    2010-06-01

    The α-condensed state in nuclear systems has been proposed by Tohsaki et al. and has given rise to interesting discussions. The Hoyle state of 12C has been studied as the most typical example of such an α-condensed state. A new resonant 03+ state (Er = 1.66 MeV, Γ = 1.48 MeV) is predicted as an excited α-condensed state in addition to the second 0+ state of the Hoyle state by calculations of the 3 α orthogonality condition model (3 α OCM) using the complex scaling method. Based on this result, the breakup strengths of the inversion reaction for sequential (8Be+α-->12C+γ) and direct (α+α+α-->12C+γ) processes are calculated. It is discussed that a large reaction strength calculated recently by Ogata et al. in non-resonant energies is considered as a contribution from the excited 03+ state.

  5. A biocompatible condensation reaction for controlled assembly of nanostructures in living cells

    NASA Astrophysics Data System (ADS)

    Liang, Gaolin; Ren, Hongjun; Rao, Jianghong

    2010-01-01

    Through controlled synthesis and molecular assembly, biological systems are able to organize molecules into supramolecular structures that carry out sophisticated processes. Although chemists have reported a few examples of supramolecular assembly in water, the controlled covalent synthesis of large molecules and structures in vivo has remained challenging. Here we report a condensation reaction between 1,2-aminothiol and 2-cyanobenzothiazole that occurs in vitro and in living cells under the control of either pH, disulfide reduction or enzymatic cleavage. In vitro, the size and shape of the condensation products, and the nanostructures subsequently assembled, were different in each case and could thus be controlled by tuning the structure of the monomers. Direct imaging of the products obtained in the cells revealed their locations-near the Golgi bodies under enzymatic cleavage control-demonstrating the feasibility of a controlled and localized reaction in living cells. This intracellular condensation process enabled the imaging of the proteolytic activity of furin.

  6. An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields

    SciTech Connect

    Miknis, F.P.

    1992-10-01

    Changes in coal structure that occur during coal drying and steam pretreatments will be measured in order to determine what effect water has on retrograde/condensation reactions, and to determine how water enhances coal reactivity toward liquefaction. Coal drying experiments were begun using thermal, microwave, and chemical methods; NMR data were collected. A stirred microautoclave reactor system was acquired.

  7. Probing the Rate-Determining Step of the Claisen-Schmidt Condensation by Competition Reactions

    ERIC Educational Resources Information Center

    Mak, Kendrew K. W.; Chan, Wing-Fat; Lung, Ka-Ying; Lam, Wai-Yee; Ng, Weng-Cheong; Lee, Siu-Fung

    2007-01-01

    Competition experiments are a useful tool for preliminary study of the linear free energy relationship of organic reactions. This article describes a physical organic experiment for upper-level undergraduates to identify the rate-determining step of the Claisen-Schmidt condensation of benzaldehyde and acetophenone by studying the linear free…

  8. Dynamic Kinetic Asymmetric Transformations of β-Stereogenic-α-Keto Esters via Direct Aldolization

    PubMed Central

    Corbett, Michael T.; Johnson, Jeffrey S.

    2014-01-01

    Dynamic kinetic asymmetric transformations (DyKAT) of racemic β-bromo-α-keto esters via direct aldolization of nitromethane and acetone provide access to fully substituted α-glycolic acid derivatives bearing a β-stereocenter. The aldol adducts are obtained in excellent yield with high relative and absolute stereocontrol under mild reaction conditions. Mechanistic studies determined that the reactions proceed through a facile catalyst-mediated racemization of the β-bromo-α-keto esters under a DyKAT Type I manifold. PMID:24222195

  9. The role of boronic acids in accelerating condensation reactions of α-effect amines with carbonyls.

    PubMed

    Gillingham, Dennis

    2016-08-10

    A broad palette of bioconjugation reactions are available for chemical biologists, but an area that still requires investigation is high-rate constant reactions. These are indispensable in certain applications, particularly for in vivo labelling. Appropriately positioned boronic acids accelerate normally sluggish Schiff base condensations of α-effect nucleophiles by five orders of magnitude - providing a new entry to the rare set of reactions that have a rate constant above 100 M(-1) s(-1) under physiological conditions. I summarize here a number of recent reports, including work from my own group, and outline a mechanistic picture that explains the differing behaviour of seemingly similar substrate classes.

  10. Mixtures of Charged Bosons Confined in Harmonic Traps and Bose-Einstein Condensation Mechanism for Low-Energy Nuclear Reactions and Transmutation Processes in Condensed Matters

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Zubarev, Alexander L.

    2006-02-01

    A mixture of two different species of positively charged bosons in harmonic traps is considered in the mean-field approximation. It is shown that depending on the ratio of parameters, the two components may coexist in same regions of space, in spite of the Coulomb repulsion between the two species. Application of this result is discussed for the generalization of the Bose-Einstein condensation mechanism for low-energy nuclear reaction (LENR) and transmutation processes in condensed matters. For the case of deutron-lithium (d + Li) LENR, the result indicates that (d + 6Li) reactions may dominate over (d + d) reactions in LENR experiments.

  11. Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step

    PubMed Central

    Fronert, Jeanne; Bisschops, Tom; Boeck, Florian

    2012-01-01

    Summary The first organocatalytic asymmetric synthesis of smyrindiol, by using an (S)-proline catalyzed enantioselective intramolecular aldol reaction as the key step, is described. Smyrindiol was synthesized from commercially available 2,4-dihydroxybenzaldehyde in 15 steps, with excellent stereoselectivity (de = 99%, ee = 99%). In the course of this total synthesis a new and mild coumarin assembly was developed. PMID:23019438

  12. A Study on the Base–Catalyzed Reverse Vinylogous Aldol Reaction of (4aβ,5β)-4,4a,5,6,7,8-Hexahydro-5-hydroxy-1,4a-dimethylnaphthalen-2(3H)-one under Robinson Annulation Conditions

    PubMed Central

    Payette, Joshua N.; Honda, Tadashi; Yoshizawa, Hidenori; Favaloro, Frank G.; Gribble, Gordon W.

    2008-01-01

    We have proposed a pathway of the base–catalyzed reverse vinylogous aldol reaction of (−)-(4aβ,5β)-4,4a,5,6,7,8-hexahydro-5-hydroxy-1,4a-dimethylnaphthalen-2(3H)-one ((−)-8) under Robinson annulation conditions. For confirmation, 4-(2,6-dimethyl-3-oxocyclohex-1-enyl)butanal (11) and 4-(2,6-dimethyl-5-oxocyclohex-1-enyl)butanal (12), both of which potentially produce enolate I, were synthesized regioselectively. Unexpectedly, 11 gave a complex mixture including only a trace amount of (±)-8 (less than 5% yield) under these basic conditions. To the contrary, 12 cleanly afforded (±)-8 in 66% yield. This result provides evidence for our proposed mechanism of the above reaction. PMID:16388674

  13. Interaction of yeasts with the products resulting from the condensation reaction between (+)-catechin and acetaldehyde.

    PubMed

    Lopez-Toledano, Azahara; Villaño-Valencia, Debora; Mayen, Manuel; Merida, Julieta; Medina, Manuel

    2004-04-21

    The condensation reaction between (+)-catechin and acetaldehyde was studied in model solutions in the presence and absence yeasts in order to evaluate its contribution to color changes in fermented drinks such as white wine. On the basis of the results, the yeasts retain the oligomers produced in the reaction, their retention ability increasing for higher polymerization degrees. As a result, the color of model solutions, measured as the absorbance at 420 nm, was found to decrease after the addition of yeasts. On the other hand, the yeasts exhibited no inhibitory effect on the condensation reaction, which took place at the same rate in their presence and absence. At acidity levels and reactant concentrations similar to those in wine, with acetaldehyde in high concentration as it is present in sherry wines, the reaction was found to occur very slowly. Taking into account that Yeasts are present during most of the winemaking process; consequently, they retain oligomers, and the studied reaction could mainly contribute to the alteration of the color of white wine after bottling. PMID:15080649

  14. Gas-Phase Condensation Reactions of SixOyHz- Oxyanions with H2O

    SciTech Connect

    Groenewold, Gary Steven; Scott, Jill Rennee; Gianotto, Anita Kay; Hodges, Brittany DM; Kessinger, Glen Frank; Benson, Michael Timothy; Wright, J. B.

    2001-09-01

    Water was reacted with gas-phase oxyanions having the general composition SixOyHz- that were formed and isolated in an ion trap-secondary ion mass spectrometer (IT-SIMS). The radical SiO2- reacted slowly with H2O to abstract HO, forming SiO3H-, at a rate of 8 × 10-13 cm3 molecule-1 s-1, corresponding to an efficiency of about 0.03% compared with the theoretical collision rate constant (average dipole orientation). The product ion SiO3H- underwent a consecutive condensation reaction with H2O to form SiO4H3- at a rate that was approximately 0.4-0.7% efficient. SiO4H3- did not undergo further reaction with water. The multiple reaction pathways by which radical SiO3- reacted with H2O were kinetically modeled using a stochastic approach. SiO3- reacted with water by three parallel reaction pathways: (1) abstraction of a radical H to form SiO3H-, which then reacted with a second H2O to form SiO4H3-; (2) abstraction of a radical OH to form SiO4H-, which further reacted by consecutive H abstractions to form SiO4H2- and then SiO4H3-; and (3) condensation with H2O to form SiO4H2-, which subsequently abstracted a radical H from a second H2O to form SiO4H3-. In all of these reactions, the rate constants were determined to be very slow, as determined by both direct measurement and stochastic modeling. For comparison, the even electron ion Si2O5H- was also investigated: it underwent condensation with H2O to form Si2O6H3-, with a rate constant corresponding to 50% efficiency. The reactions were also modeled using ab initio calculations at the UB3LYP/6-311+G(2d,p) level. Addition of H2O to SiO3-, SiO3H-, and Si2O5H- was calculated to be approximately 42, 45, and 55 kcal mol-1 exothermic, respectively, and encountered low activation barriers. Modeling of SiO2- and SiO3- reactions with H2O failed to produce radical abstraction reaction pathways observed in the IT-SIMS, possibly indicating that alternative reaction mechanisms are operative.

  15. Toward a reaction rate model of condensed-phase RDX decomposition under high temperatures

    NASA Astrophysics Data System (ADS)

    Schweigert, Igor

    2015-06-01

    Shock ignition of energetic molecular solids is driven by microstructural heterogeneities, at which even moderate stresses can result in sufficiently high temperatures to initiate material decomposition and chemical energy release. Mesoscale modeling of these ``hot spots'' requires a reaction rate model that describes the energy release with a sub-microsecond resolution and under a wide range of temperatures. No such model is available even for well-studied energetic materials such as RDX. In this presentation, I will describe an ongoing effort to develop a reaction rate model of condensed-phase RDX decomposition under high temperatures using first-principles molecular dynamics, transition-state theory, and reaction network analysis. This work was supported by the Naval Research Laboratory, by the Office of Naval Research, and by the DoD High Performance Computing Modernization Program Software Application Institute for Multiscale Reactive Modeling of Insensitive Munitions.

  16. Toward a reaction rate model of condensed-phase RDX decomposition under high temperatures

    NASA Astrophysics Data System (ADS)

    Schweigert, Igor

    2014-03-01

    Shock ignition of energetic molecular solids is driven by microstructural heterogeneities, at which even moderate stresses can result in sufficiently high temperatures to initiate material decomposition and the release of the chemical energy. Mesoscale modeling of these ``hot spots'' requires a chemical reaction rate model that describes the energy release with a sub-microsecond resolution and under a wide range of temperatures. No such model is available even for well-studied energetic materials such as RDX. In this presentation, I will describe an ongoing effort to develop a reaction rate model of condensed-phase RDX decomposition under high temperatures using first-principles molecular dynamics, transition-state theory, and reaction network analysis. This work was supported by the Naval Research Laboratory, by the Office of Naval Research, and by the DOD High Performance Computing Modernization Program Software Application Institute for Multiscale Reactive Modeling of Insensitive Munitions.

  17. Monte Carlo simulation of hyaluronidase reaction involving hydrolysis, transglycosylation and condensation.

    PubMed Central

    Nakatani, Hiroshi

    2002-01-01

    The action of hyaluronidase on oligosaccharides from hyaluronan is complicated due to branched reaction paths containing hydrolysis, transglycosylation and condensation. The unit component of hyaluronan is a disaccharide, namely GlcA-(beta 1-->3)-GlcNAc where GlcA and GlcNAc are d-glucuronic acid and d-N-acetylglucosamine respectively. Hyaluronan is the linear polymer formed by these disaccharide units, linked together with beta 1-->4 glycosidic bonds. Bovine testicular hyaluronidase acts only at beta 1-->4 glycosidic bonds of hyaluronan. The progress of product distribution from short oligosaccharides was simulated with the Monte Carlo method using the probabilistic model. The model consists only of a single enzyme molecule and a finite number of substrate and water molecules. The simulation is based on a simple reaction scheme and proceeds via an algorithm with minimum adjustable parameters generating random numbers and probabilities. The experimental data for bovine testicular hyaluronidase using [GlcA-(beta 1-->3)-GlcNAc](4) as the starting substrate were quantitatively simulated with only three adjustable parameters. The simulated data for [GlcA-(beta 1-->3)-GlcNAc](3) and [GlcA-(beta 1-->3)-GlcNAc](5) as the starting substrates agreed semi-quantitatively with experimental data using the same parameters. The mechanism of the hyaluronidase reaction is a combination of branched probabilistic cycles. The condensation reaction is much weaker than the transglycosylation reaction but contributes to product distribution at the final stage of the reaction, preventing complete hydrolysis of the substrates. PMID:11965243

  18. Traceless OH-Directed Wacker Oxidation-Elimination, an Alternative to Wittig Olefination/Aldol Condensation: One-Pot Synthesis of α,β-Unsaturated and Nonconjugated Ketones from Homoallyl Alcohols.

    PubMed

    Bethi, Venkati; Fernandes, Rodney A

    2016-09-16

    A new method for one-pot synthesis of β-substituted and β,β-disubstituted α,β-unsaturated methyl ketones from homoallyl alcohols by sequential PdCl2/CrO3-promoted Wacker process followed by an acid-mediated dehydration reaction has been developed. Remarkably, internal homoallyl alcohols delivered regioselectively nonconjugated unsaturated carbonyl compounds under the same protocol. A new starting material-based synthesis of α,β-unsaturated and nonconjugated methyl ketones is demonstrated.

  19. Classical Keggin Intercalated into Layered Double Hydroxides: Facile Preparation and Catalytic Efficiency in Knoevenagel Condensation Reactions.

    PubMed

    Jia, Yueqing; Fang, Yanjun; Zhang, Yingkui; Miras, Haralampos N; Song, Yu-Fei

    2015-10-12

    The family of polyoxometalate (POM) intercalated layered double hydroxide (LDH) composite materials has shown great promise for the design of functional materials with numerous applications. It is known that intercalation of the classical Keggin polyoxometalate (POM) of [PW12 O40 ](3-) (PW12 ) into layered double hydroxides (LDHs) is very unlikely to take place by conventional ion exchange methods due to spatial and geometrical restrictions. In this paper, such an intercalated compound of Mg0.73 Al0.22 (OH)2 [PW12 O40 ]0.04 ⋅0.98 H2 O (Mg3 Al-PW12 ) has been successfully obtained by applying a spontaneous flocculation method. The Mg3 Al-PW12 has been fully characterized by using a wide range of methods (XRD, SEM, TEM, XPS, EDX, XPS, FT-IR, NMR, BET). XRD patterns of Mg3 Al-PW12 exhibit no impurity phase usually observed next to the (003) diffraction peak. Subsequent application of the Mg3 Al-PW12 as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z-CH2 -Z' type substrates (ethyl cyanoacetate and malononitrile) at 60 °C in mixed solvents (V2-propanol :Vwater =2:1) demonstrated highly efficient catalytic activity. The synergistic effect between the acidic and basic sites of the Mg3 Al-PW12 composite proved to be crucial for the efficiency of the condensation reactions. Additionally, the Mg3 Al-PW12 -catalyzed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate demonstrated the highest turnover number (TON) of 47 980 reported so far for this reaction.

  20. Traceless OH-Directed Wacker Oxidation-Elimination, an Alternative to Wittig Olefination/Aldol Condensation: One-Pot Synthesis of α,β-Unsaturated and Nonconjugated Ketones from Homoallyl Alcohols.

    PubMed

    Bethi, Venkati; Fernandes, Rodney A

    2016-09-16

    A new method for one-pot synthesis of β-substituted and β,β-disubstituted α,β-unsaturated methyl ketones from homoallyl alcohols by sequential PdCl2/CrO3-promoted Wacker process followed by an acid-mediated dehydration reaction has been developed. Remarkably, internal homoallyl alcohols delivered regioselectively nonconjugated unsaturated carbonyl compounds under the same protocol. A new starting material-based synthesis of α,β-unsaturated and nonconjugated methyl ketones is demonstrated. PMID:27562136

  1. Condensation Reactions and Formation of Amides, Esters, and Nitriles Under Hydrothermal Conditions

    NASA Astrophysics Data System (ADS)

    Rushdi, Ahmed I.; Simoneit, Bernd R. T.

    2004-06-01

    Hydrothermal pyrolysis experiments were performed to assess condensation (dehydration) reactions to amide, ester, and nitrile functionalities from lipid precursors. Beside product formation, organic compound alteration and stability were also evaluated. Mixtures of nonadecanoic acid, hexadecanedioic acid, or hexadecanamide with water, ammonium bicarbonate, and oxalic acid were heated at 300°C for 72 h. In addition, mixtures of ammonium bicarbonate and oxalic acid solutions were used to test the abiotic formation of organic nitrogen compounds at the same temperature. The resulting products were condensation compounds such as amides, nitriles, and minor quantities of N-methylalkyl amides, alkanols, and esters. Mixtures of alkyl amide in water or oxalic acid yielded mainly hydrolysis and dehydration products, and with ammonium bicarbonate and oxalic acid the yield of condensation products was enhanced. The synthesis experiments with oxalic acid and ammonium bicarbonate solutions yielded homologous series of alkyl amides, alkyl amines, alkanes, and alkanoic acids, all with no carbon number predominances. These organic nitrogen compounds are stable and survive under the elevated temperatures of hydrothermal fluids.

  2. Quantum and Molecular Mechanical (QM/MM) Monte Carlo Techniques for Modeling Condensed-Phase Reactions

    PubMed Central

    Jorgensen, Wiliiam L.

    2014-01-01

    A recent review (Acc. Chem. Res. 2010, 43:142–151) examined our use and development of a combined quantum and molecular mechanical (QM/MM) technique for modelling organic and enzymatic reactions. Advances included the PDDG/PM3 semiempirical QM (SQM) method, computation of multi-dimensional potentials of mean force (PMF), incorporation of on-the-fly QM in Monte Carlo simulations, and a polynomial quadrature method for rapidly treating proton-transfer reactions. The current article serves as a follow up on our progress. Highlights include new reactions, alternative SQM methods, a polarizable OPLS force field, and novel solvent environments, e.g., “on water” and room temperature ionic liquids. The methodology is strikingly accurate across a wide range of condensed-phase and antibody-catalyzed reactions including substitution, decarboxylation, elimination, isomerization, and pericyclic classes. Comparisons are made to systems treated with continuum-based solvents and ab initio or density functional theory (DFT) methods. Overall, the QM/MM methodology provides detailed characterization of reaction paths, proper configurational sampling, several advantages over implicit solvent models, and a reasonable computational cost. PMID:25431625

  3. Quantum and Molecular Mechanical (QM/MM) Monte Carlo Techniques for Modeling Condensed-Phase Reactions.

    PubMed

    Acevedo, Orlando; Jorgensen, Wiliiam L

    2014-09-01

    A recent review (Acc. Chem. Res. 2010, 43:142-151) examined our use and development of a combined quantum and molecular mechanical (QM/MM) technique for modelling organic and enzymatic reactions. Advances included the PDDG/PM3 semiempirical QM (SQM) method, computation of multi-dimensional potentials of mean force (PMF), incorporation of on-the-fly QM in Monte Carlo simulations, and a polynomial quadrature method for rapidly treating proton-transfer reactions. The current article serves as a follow up on our progress. Highlights include new reactions, alternative SQM methods, a polarizable OPLS force field, and novel solvent environments, e.g., "on water" and room temperature ionic liquids. The methodology is strikingly accurate across a wide range of condensed-phase and antibody-catalyzed reactions including substitution, decarboxylation, elimination, isomerization, and pericyclic classes. Comparisons are made to systems treated with continuum-based solvents and ab initio or density functional theory (DFT) methods. Overall, the QM/MM methodology provides detailed characterization of reaction paths, proper configurational sampling, several advantages over implicit solvent models, and a reasonable computational cost. PMID:25431625

  4. Closure of the condensed-phase organic-nitrate reaction USQ at hanford

    SciTech Connect

    COWLEY, W.L.

    1999-06-24

    A discovery Unreviewed Safety Question (USQ) was declared on the underground waste storage tanks at the Hanford Site in May 1996. The USQ was for condensed-phase organic-nitrate reactions (sometimes called organic complexant reactions) in the tanks. This paper outlines the steps taken to close the USQ, and resolve the related safety issue. Several processes were used at the Hanford Site to extract and/or process plutonium. These processes resulted in organic complexants (for chelating multivalent cations) and organic extraction solvents being sent to the underground waste storage tanks. This paper addresses the organic complexant hazard. The organic complexants are in waste matrices that include inert material, diluents, and potential oxidizers. In the presence of oxidizing material, the complexant salts can be made to react exothermically by heating to high temperatures or by applying an external ignition source of sufficient energy. The first organic complexant hazard assessments focused on determining whether a hulk runaway reaction could occur, similar to the 1957 accident at Kyshtm (a reprocessing plant in the former U.S.S.R.). Early analyses (1977 through 1994) examined organic-nitrate reaction onset temperatures and concluded that a bulk runaway reaction could not occur at the Hanford Site because tank temperatures were well below that necessary for bulk runaway. Therefore, it was believed that organic-nitrate reactions were adequately described in the then current Authorization Basis (AB). Subsequent studies examined a different accident scenario, propagation resulting from an external ignition source (e.g., lightning or welding slag) that initiates a combustion front that propagates through the organic waste. A USQ evaluation determined that localized high energy ignition sources were credible, and that point source ignition of organic complexant waste was not adequately addressed i n the then existing AB. Consequently, the USQ was declared on the

  5. Alternative Interpretation of Low-Energy Nuclear Reaction Processes with Deuterated Metals Based on the Bose-Einstein Condensation Mechanism

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Passell, Thomas O.

    2006-02-01

    Recently, a generalization of the Bose-Einstein condensation (BEC) mechanism has been made to a ground-state mixture of two different species of positively charged bosons in harmonic traps. The theory has been used to describe (D + Li) reactions in the low energy nuclear reaction (LENR) processes in condensed matter and predicts that the (D + Li) reaction rates can be larger than (D + D) reaction rates by as much as a factor of ~50, implying that (D + Li) reactions may be occuring in addition to the (D + D) reactions. A survey of the existing data from LENR experiments is carried out to check the validity of the theoretical prediction. We conclude that there is compelling experimental evidence which support the theoretical prediction. New experimental tests of the theoretical prediction are suggested.

  6. Molecular Mechanism by which One Enzyme Catalyzes Two Reactions

    NASA Astrophysics Data System (ADS)

    Nishimasu, Hiroshi; Fushinobu, Shinya; Wakagi, Takayoshi

    Unlike ordinary enzymes, fructose-1,6-bisphosphate (FBP) aldolase/phosphatase (FBPA/P) catalyzes two distinct reactions : (1) the aldol condensation of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate to FBP, and (2) the dephosphorylation of FBP to fructose-6-phosphate. We solved the crystal structures of FBPA/P in complex with DHAP (its aldolase form) and FBP (its phosphatase form). The crystal structures revealed that FBPA/P exhibits the dual activities through a dramatic conformational change in the active-site architecture. Our findings expand the conventional concept that one enzyme catalyzes one reaction.

  7. Technical Note: Analytical Solution for Transient Partitioning and Reaction of a Condensing Vapor Species in a Droplet

    SciTech Connect

    Liu, Albert T.; Zaveri, Rahul A.; Seinfeld, John H.

    2014-03-28

    We present the exact analytical solution of the transient equation of gas-phase diffusion of a condensing vapor to, and diffusion and reaction in, an aqueous droplet. Droplet-phase reaction is represented by first-order chemistry. The solution facilitates study of the dynamic nature of the vapor uptake process as a function of droplet size, Henry’s law coefficient, and first-order reaction rate constant for conversion in the droplet phase.

  8. Free energy landscape for glucose condensation and dehydration reactions in dimethyl sulfoxide and the effects of solvent.

    PubMed

    Qian, Xianghong; Liu, Dajiang

    2014-03-31

    The mechanisms and free energy surfaces (FES) for the initial critical steps during proton-catalyzed glucose condensation and dehydration reactions were elucidated in dimethyl sulfoxide (DMSO) using Car-Parrinello molecular dynamics (CPMD) coupled with metadynamics (MTD) simulations. Glucose condensation reaction is initiated by protonation of C1--OH whereas dehydration reaction is initiated by protonation of C2--OH. The mechanisms in DMSO are similar to those in aqueous solution. The DMSO molecules closest to the C1--OH or C2--OH on glucose are directly involved in the reactions and act as proton acceptors during the process. However, the energy barriers are strongly solvent dependent. Moreover, polarization from the long-range electrostatic interaction affects the mechanisms and energetics of glucose reactions. Experimental measurements conducted in various DMSO/Water mixtures also show that energy barriers are solvent dependent in agreement with our theoretical results. PMID:24631668

  9. Synthesis of the Cores of Hypocrellin and Shiraiachrome: Diastereoselective 1,8-Diketone Aldol Cyclization

    PubMed Central

    O’Brien, Erin M.; Li, Jingxian; Carroll, Patrick J.

    2009-01-01

    Intramolecular 1,8-diketone aldol reactions were studied as a tool for the construction of the 7-membered rings of hypocrellin and shiraiachrome. Conditions were identified to obtain the relative stereochemistries present in the two natural products with excellent diastereoselectivity. In addition, a nine-membered ring congener, which has yet to be observed in nature, formed with high selectivity when a hindered amine was used in conjunction with silazide bases. PMID:19894740

  10. Charge constrained density functional molecular dynamics for simulation of condensed phase electron transfer reactions

    SciTech Connect

    Oberhofer, Harald; Blumberger, Jochen

    2009-08-14

    We present a plane-wave basis set implementation of charge constrained density functional molecular dynamics (CDFT-MD) for simulation of electron transfer reactions in condensed phase systems. Following the earlier work of Wu and Van Voorhis [Phys. Rev. A 72, 024502 (2005)], the density functional is minimized under the constraint that the charge difference between donor and acceptor is equal to a given value. The classical ion dynamics is propagated on the Born-Oppenheimer surface of the charge constrained state. We investigate the dependence of the constrained energy and of the energy gap on the definition of the charge and present expressions for the constraint forces. The method is applied to the Ru{sup 2+}-Ru{sup 3+} electron self-exchange reaction in aqueous solution. Sampling the vertical energy gap along CDFT-MD trajectories and correcting for finite size effects, a reorganization free energy of 1.6 eV is obtained. This is 0.1-0.2 eV lower than a previous estimate based on a continuum model for solvation. The smaller value for the reorganization free energy can be explained by the fact that the Ru-O distances of the divalent and trivalent Ru hexahydrates are predicted to be more similar in the electron transfer complex than for the separated aqua ions.

  11. Charge constrained density functional molecular dynamics for simulation of condensed phase electron transfer reactions

    NASA Astrophysics Data System (ADS)

    Oberhofer, Harald; Blumberger, Jochen

    2009-08-01

    We present a plane-wave basis set implementation of charge constrained density functional molecular dynamics (CDFT-MD) for simulation of electron transfer reactions in condensed phase systems. Following the earlier work of Wu and Van Voorhis [Phys. Rev. A 72, 024502 (2005)], the density functional is minimized under the constraint that the charge difference between donor and acceptor is equal to a given value. The classical ion dynamics is propagated on the Born-Oppenheimer surface of the charge constrained state. We investigate the dependence of the constrained energy and of the energy gap on the definition of the charge and present expressions for the constraint forces. The method is applied to the Ru2+-Ru3+ electron self-exchange reaction in aqueous solution. Sampling the vertical energy gap along CDFT-MD trajectories and correcting for finite size effects, a reorganization free energy of 1.6 eV is obtained. This is 0.1-0.2 eV lower than a previous estimate based on a continuum model for solvation. The smaller value for the reorganization free energy can be explained by the fact that the Ru-O distances of the divalent and trivalent Ru hexahydrates are predicted to be more similar in the electron transfer complex than for the separated aqua ions.

  12. Equation of state and reaction rate for condensed-phase explosives

    NASA Astrophysics Data System (ADS)

    Wescott, B. L.; Stewart, D. Scott; Davis, W. C.

    2005-09-01

    The wide-ranging equation of state is a nonideal equation of state based on empirical fitting forms argued from thermodynamic considerations that yield the proper physical features of detonation. The complete equation of state forms are presented and the equation of state and a reaction rate are calibrated for the condensed-phase explosive PBX-9502. Experimental overdriven Hugoniot data are used to calibrate the products equation of state off the principal isentrope passing through the Chapman-Jouguet state. Shock Hugoniot data are used to calibrate the reactants equation of state. The normal detonation shock speed-shock curvature data (Dn-κ) from rate-stick measurements and shock initiation data from wedge tests are used to calibrate the reaction rate. Simulations are carried out that predict detailed particle velocity transients that are measured experimentally with embedded electromagnetic gauge measurements from gas-gun experiments. Multidimensional simulations of steady detonation in a right circular cylinder rate stick are carried out and compared with experiment.

  13. An Investigation of the Solid-State Condensation Polymerization Reaction in Vapor-Deposited Poly(amic acid)

    NASA Astrophysics Data System (ADS)

    Anthamatten, Mitchell; Letts, Stephan A.; Day, Katherine; Cook, Robert C.; Gies, Anthony P.; Nonidez, William K.

    2004-03-01

    The condensation polymerization reaction of 4,4'-oxydianiline (ODA) with pyromellitic dianhydride (PMDA) to form poly(amic acid) and the subsequent imidization reaction to form polyimide were investigated for films prepared using vapor deposition polymerization techniques. Fourier-transform infrared spectroscopy (FTIR), thermal analysis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of films prepared at different temperatures indicate that additional solid-state polymerization occurs prior to imidization reactions. Experiments suggest that poly(amic acid) oligomers form upon vapor-deposition and have a number-average molecular weights of about 1500 Daltons. Between 100-130 °C these chains undergo additional condensation reactions to form slightly higher molecular weight oligomers. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  14. An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields

    SciTech Connect

    Miknis, F.P.

    1993-01-01

    The overall objectives of this work are to conduct research that will provide the basis for an improved liquefaction process, and to facilitate our understanding of those processes that occur when coals are initially dissolved. Changes in coal structure that occur during coal drying and steam pretreatments will be measured in order to determine what effect water has on retrograde/condensation reactions, and to determine the mechanism by which water enhances coal reactivity toward liquefaction. Different methods for coal drying wig be investigated to determine if drying can be accomplished without destroying coal reactivity toward liquefaction, thereby making coal drying a relatively economical and efficient method for coal pretreatment. Coal drying methods will include conventional thermal drying, microwave drying, and chemical drying at low temperature. State-of-the-art solid-state nuclear magnetic resonance (NMR) techniques using combined rotation and multiple pulse spectroscopy (CRAMPS) and cross polarization with magic-angle spinning (CP/MAS) will be employed: (1) to measures changes in coal structure brought about by the different methods of drying and by low temperature oxidation, and (2) to obtain direct measurements of changes in the aromatic hydrogen-to-carbon ratio of the solid/semisolid material formed or remaining during pretreatment and the initial stages of liquefaction.

  15. Modeling reaction histories to study chemical pathways in condensed phase detonation

    NASA Astrophysics Data System (ADS)

    Scott Stewart, D.; Hernández, Alberto; Lee, Kibaek

    2016-03-01

    The estimation of pressure and temperature histories, which are required to understand chemical pathways in condensed phase explosives during detonation, is discussed. We argue that estimates made from continuum models, calibrated by macroscopic experiments, are essential to inform modern, atomistic-based reactive chemistry simulations at detonation pressures and temperatures. We present easy to implement methods for general equation of state and arbitrarily complex chemical reaction schemes that can be used to compute reactive flow histories for the constant volume, the energy process, and the expansion process on the Rayleigh line of a steady Chapman-Jouguet detonation. A brief review of state-of-the-art of two-component reactive flow models is given that highlights the Ignition and Growth model of Lee and Tarver [Phys. Fluids 23, 2362 (1980)] and the Wide-Ranging Equation of State model of Wescott, Stewart, and Davis [J. Appl. Phys. 98, 053514 (2005)]. We discuss evidence from experiments and reactive molecular dynamic simulations that motivate models that have several components, instead of the two that have traditionally been used to describe the results of macroscopic detonation experiments. We present simplified examples of a formulation for a hypothetical explosive that uses simple (ideal) equation of state forms and detailed comparisons. Then, we estimate pathways computed from two-component models of real explosive materials that have been calibrated with macroscopic experiments.

  16. Polarizabilities in the condensed phase and the local fields problem: A direct reaction field formulation

    NASA Astrophysics Data System (ADS)

    van Duijnen, Piet Th.; de Vries, Alex H.; Swart, Marcel; Grozema, Ferdinand

    2002-11-01

    A consistent derivation is given for local field factors to be used for correcting measured or calculated static (hyper)polarizabilities in the condensed phases. We show how local fields should be used in the coupled perturbative Hartree-Fock or finite field methods for calculating these properties, specifically for the direct reaction field (DRF) approach, in which a quantum chemically treated "solute" is embedded in a classical "solvent" mainly containing discrete molecules. The derivation of the local fields is based on a strictly linear response of the classical parts and they are independent of any quantum mechanical method to be used. In applications to two water dimers in two basis sets it is shown that DRF matches fully quantum mechanical results quite well. For acetone in eleven different solvents we find that if the solvent is modeled by only a dielectric continuum (hyper)polarizabilities increase with respect to their vacuum values, while with the discrete model they decrease. We show that the use of the Lorentz field factor for extracting (hyper)polarizabilities from experimental susceptibilities may lead to serious errors.

  17. Gold catalyzed double condensation reaction: Synthesis, antimicrobial and cytotoxicity of spirooxindole derivatives.

    PubMed

    Parthasarathy, K; Praveen, Chandrasekar; Jeyaveeran, J C; Prince, A A M

    2016-09-01

    Microwave assisted synthesis of spirooxindoles via tandem double condensation between isatins and 4-hydroxycoumarin under gold catalysis is reported. The reaction is practical to perform, since the products can be isolated by simple filtration without requiring tedious column chromatography. The scope of this chemistry is exemplified by preparing structurally diverse spirooxindoles (22 examples) in excellent yields. Antimicrobial evaluation of the synthesized compounds revealed that three compounds (3a, 3f and 3s) exhibited significant MIC values in comparison to the standard drugs. Molecular docking studies of these compounds with AmpC-β-lactamase receptor revealed that 3a exhibited minimum binding energy (-117.819kcal/mol) indicating its strong affinity towards amino acid residues via strong hydrogen bond interaction. All compounds were also evaluated for their in vitro cytotoxicity against COLO320 cancer cells. Biological assay and molecular docking studies demonstrated that 3g is the most active compound in terms of its low IC50 value (50.0μM) and least free energy of binding (-8.99kcal/mol) towards CHK1 receptor, respectively. PMID:27476145

  18. Intramolecular condensation reactions of {alpha}, {omega}- bis(triethoxy-silyl)alkanes. Formation of cyclic disilsesquioxanes

    SciTech Connect

    Loy, D.A.; Carpenter, J.P.; Myers, S.A.; Assink, R.A.; Small, J.H.; Greaves, J.; Shea, K.J.

    1996-08-01

    Under acidic sol-gel polymerization conditions, 1,3-bis(triethoxysilyl)-propane (1) and 1,4-bis(triethoxysilyl)butane (2) were shown to preferentially form cyclic disilsesquioxanes 3 and 4 rather than the expected 1,3-propylene- and 1,4-butylene-bridged polysilsesquioxane gels. Formation of 3 and 4 is driven by a combination of an intramolecular cyclization to six and seven membered rings, and a pronounced reduction in reactivity under acidic conditions as a function of increasing degree of condensation. The ease with which these relatively unreactive cyclic monomers and dimers are formed (under acidic conditions) helps to explain the difficulties in forming gels from 1 and 2. The stability of cyclic disilsesquioxanes was confirmed withe the synthesis of 3 and 4 in gram quantities; the cyclic disilsesquioxanes react slowly to give tricyclic dimers containing a thermodynamically stable eight membered siloxane ring. Continued reactions were shown to perserve the cyclic structure, opening up the possibility of utilizing cyclic disilsesquioxanes as sol-gel monomers. Preliminary polymerization studies with these new, carbohydrate-like monomers revealed the formation of network poly(cyclic disilsesquioxanes) under acidic conditions and polymerization with ring-opening under basic conditions.

  19. Golden rule kinetics of transfer reactions in condensed phase: the microscopic model of electron transfer reactions in disordered solid matrices.

    PubMed

    Basilevsky, M V; Odinokov, A V; Titov, S V; Mitina, E A

    2013-12-21

    postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode∕medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems. PMID:24359347

  20. Golden rule kinetics of transfer reactions in condensed phase: the microscopic model of electron transfer reactions in disordered solid matrices.

    PubMed

    Basilevsky, M V; Odinokov, A V; Titov, S V; Mitina, E A

    2013-12-21

    postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode∕medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.

  1. Controlling reaction specificity in pyridoxal phosphate enzymes

    PubMed Central

    Toney, Michael D.

    2012-01-01

    Pyridoxal 5'-phosphate enzymes are ubiquitous in the nitrogen metabolism of all organisms. They catalyze a wide variety of reactions including racemization, transamination, decarboxylation, elimination, retro-aldol cleavage, Claisen condensation, and others on substrates containing an amino group, most commonly α-amino acids. The wide variety of reactions catalyzed by PLP enzymes is enabled by the ability of the covalent aldimine intermediate formed between substrate and PLP to stabilize carbanionic intermediates at Cα of the substrate. This review attempts to summarize the mechanisms by which reaction specificity can be achieved in PLP enzymes by focusing on three aspects of these reactions: stereoelectronic effects, protonation state of the external aldimine intermediate, and interaction of the carbanionic intermediate with the protein side chains present in the active site. PMID:21664990

  2. Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions.

    PubMed

    Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Cejka, Jiří

    2013-01-01

    Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of β-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite beta and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)beta < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)beta and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of β-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate.

  3. Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions

    PubMed Central

    Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Čejka, Jiří

    2013-01-01

    Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of β-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite beta and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)beta < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)beta and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of β-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate. PMID:24790940

  4. Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions

    NASA Astrophysics Data System (ADS)

    Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Čejka, Jiří

    2013-08-01

    Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of β-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite BEA and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)BEA < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)BEA and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of β-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate.

  5. Probing the chemical structure of monolayer covalent-organic frameworks grown via Schiff-base condensation reactions.

    PubMed

    Hu, Ya; Goodeal, Niall; Chen, Ying; Ganose, Alex M; Palgrave, Robert G; Bronstein, Hugo; Blunt, Matthew O

    2016-08-01

    Two-dimensional covalent-organic frameworks (2D-COFs) on surfaces offer a facile route to new 2D materials. Schiff-base condensation reactions have proven to be an effective fabrication route for such materials. We present scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) studies of porphyrin 2D-COFs grown at a solid-vapour interface. XPS shows that covalent links between porphyrins consist of a mixture of imines and hemiaminals, a non-conjugated intermediate in the Schiff-base condensation reaction. These results demonstrate that environmental conditions during growth can have an important impact on the chemical composition of Schiff-base 2D-COFs.

  6. Anomalous nuclear reactions in condensed matter: Recent results and open questions

    NASA Astrophysics Data System (ADS)

    Jones, S. E.; Palmer, E. P.; Czirr, J. B.; Decker, D. L.; Jensen, G. L.; Thorne, J. M.; Taylor, S. F.; Rafelski, J.

    1990-06-01

    We have observed clear signatures for neutron emission during deuteron infusion into metals, implying the occurrence of nuclear fusion in condensed matter near room temperature. The low-level nuclear phenomenon has been demonstrated in collaborative experiments at Brigham Young University, at the Gran Sasso laboratory in Italy, and at the Los Alamos National Laboratory. We have shown that neutron emission can be induced in metals using both electrochemical and variational temperature/pressure means to generate non-equilibrium conditions. Observed average neutron emission rates are approximately 0.04-0.4 no/ s. Current efforts focus on trying to understand and control the phenomenon. In particular, we wish to understand the correlation of neutron yields with parameters such as hydrogen/metal ion ratio, pressure (induced, for example, by electrical field or gas pressure or mechanical pressure), temperature variation, hydride phase changes, and surface conditions, e.g., a palladium coating on titanium. We want to know if fusion arises due to the close proximity of the deuterons in the lattice (piezonuclear fusion), or possibly from “microscopic hot fusion”, accompanying strong electric fields at propagating cracks in the hydride. The latter interpretation would imply neutron emission in bursts. Our experiments show clear evidence for emission of ˜102 neutrons in bursts lasting <128 μs, although random neutron-singles emissions were also observed. Experiments now underway to compare the d-d, and p-d, and d-t reaction rates will be important to a consistent description of the new phenomenon. Careful scrutiny of this effect could increase our understanding of heat, helium-3, and tritium production in the earth, other planets, and even the stars.

  7. Stereopentads derived from a sequence of Mukaiyama aldolization and free radical reduction on alpha-methyl-beta-alkoxy aldehydes: a general strategy for efficient polypropionate synthesis.

    PubMed

    Brazeau, Jean-François; Mochirian, Philippe; Prévost, Michel; Guindon, Yvan

    2009-01-01

    In a stereodivergent manner, all 16 diastereomeric stereopentads 7-22 were synthesized starting with alpha-methyl-beta-alkoxy aldehydes 25 and 27. We designed an approach based on a sequence of a Mukaiyama aldolization with enoxysilane 24 followed by a hydrogen transfer reaction. Recent advancements concerning these reactions are described, and novel key intermediates are characterized in the aldol step. The synthesis of C(1)-C(11) fragment 60 of zincophorin, which contains a synthetically challenging stereopentad unit, is described attesting the usefulness of our strategy.

  8. Synthesis of 1,5-Benzodiazepine and Its Derivatives by Condensation Reaction Using H-MCM-22 as Catalyst

    PubMed Central

    Majid, Sheikh Abdul; Khanday, Waheed Ahmad; Tomar, Radha

    2012-01-01

    A simple and versatile method for the synthesis of 1,5-benzodiazepines is via condensation of o-phenylenediamines (OPDA) and ketones in the presence of catalytic amount of H-MCM-22 using acetonitrile as solvent at room temperature. In all the cases, the reactions are highly selective and are completed within 1–3 h. The method is applicable to both cyclic and acyclic ketones without significant differences. The reaction proceeds efficiently under ambient conditions with good-to-excellent yields. PMID:22570531

  9. Quantum chemical approach for condensed-phase thermochemistry (II): Applications to formation and combustion reactions of liquid organic molecules

    NASA Astrophysics Data System (ADS)

    Ishikawa, Atsushi; Nakai, Hiromi

    2015-03-01

    The harmonic solvation model (HSM), which was recently developed for evaluating condensed-phase thermodynamics by quantum chemical calculations (Nakai and Ishikawa, 2014), was applied to formation and combustion reactions of simple organic molecules. The conventional ideal gas model (IGM) considerably overestimated the entropies of the liquid molecules. The HSM could significantly improve this overestimation; mean absolute deviations for the Gibbs energies of the formation and combustion reactions were (49.6, 26.7) for the IGM and (9.7, 5.4) for the HSM in kJ/mol.

  10. Origin of saline, neutral-pH, reduced epithermal waters by reaction of acidic magmatic gas condensates with wall rock

    SciTech Connect

    Reed, M.H. . Dept. of Geological Sciences)

    1993-04-01

    Fluid inclusions in quartz and sphalerite of epithermal veins containing galena, sphalerite and chalcopyrite with silver sulfides and electrum commonly have salinities of 2 to 10 weight percent NaCl equivalent. Examples include Bohemia, OR, Comstock, NV, and Creede, CO. Salinities in such base metal-rich systems are apparently greater than those in gold-adularia, base metal-poor systems such as Sleeper, NV, Republic, WA, and Hishikare, Kyushu. Saline epithermal fluids are commonly assumed to have been derived from saline magmatic brines, from local host formations, as has been suggested for Creede, or from evaporative concentration (boiling) of more dilute meteoric ground water. Another possibility, which may be the most common origin, is reaction of wall rocks with magmatic gas condensates rich in HCl and sulfuric acid. A mixture of one part Augustine Volcanic gas condensate in 10 parts cold ground water has a pH of 0.7 and the dominant cation is H[sup +] by a factor of 10[sup 4]. Calculated reaction of this condensate mixture with andesite at 300 C to a water/rock ratio (w/r) of 4.6 yields an NaCl-dominated fluid with a total salinity of 2.1 wt %. and pH 3.7. Further reaction, to w/r 0.14 yields a fluid salinity of 2.6 wt % and pH of 5.7; this fluid is in equilibrium with a propylitic alteration assemblage. Aqueous sulfide accumulates during the rock reaction as sulfate is reduced to sulfide when ferrous iron is oxidized to ferric iron. Sulfide concentration in the latter fluid is 32 ppm, far exceeding sulfate concentration. In the overall reaction, hydrogen ion is exchanged for base cations (including base metals) and sulfate is reduced to sulfide.

  11. Mechanism of the intramolecular Claisen condensation reaction catalyzed by MenB, a crotonase superfamily member.

    PubMed

    Li, Huei-Jiun; Li, Xiaokai; Liu, Nina; Zhang, Huaning; Truglio, James J; Mishra, Shambhavi; Kisker, Caroline; Garcia-Diaz, Miguel; Tonge, Peter J

    2011-11-01

    MenB, the 1,4-dihydroxy-2-naphthoyl-CoA synthase from the bacterial menaquinone biosynthesis pathway, catalyzes an intramolecular Claisen condensation (Dieckmann reaction) in which the electrophile is an unactivated carboxylic acid. Mechanistic studies on this crotonase family member have been hindered by partial active site disorder in existing MenB X-ray structures. In the current work the 2.0 Å structure of O-succinylbenzoyl-aminoCoA (OSB-NCoA) bound to the MenB from Escherichia coli provides important insight into the catalytic mechanism by revealing the position of all active site residues. This has been accomplished by the use of a stable analogue of the O-succinylbenzoyl-CoA (OSB-CoA) substrate in which the CoA thiol has been replaced by an amine. The resulting OSB-NCoA is stable, and the X-ray structure of this molecule bound to MenB reveals the structure of the enzyme-substrate complex poised for carbon-carbon bond formation. The structural data support a mechanism in which two conserved active site Tyr residues, Y97 and Y258, participate directly in the intramolecular transfer of the substrate α-proton to the benzylic carboxylate of the substrate, leading to protonation of the electrophile and formation of the required carbanion. Y97 and Y258 are also ideally positioned to function as the second oxyanion hole required for stabilization of the tetrahedral intermediate formed during carbon-carbon bond formation. In contrast, D163, which is structurally homologous to the acid-base catalyst E144 in crotonase (enoyl-CoA hydratase), is not directly involved in carbanion formation and may instead play a structural role by stabilizing the loop that carries Y97. When similar studies were performed on the MenB from Mycobacterium tuberculosis, a twisted hexamer was unexpectedly observed, demonstrating the flexibility of the interfacial loops that are involved in the generation of the novel tertiary and quaternary structures found in the crotonase superfamily. This

  12. Path-integral calculations of heavy atom kinetic isotope effects in condensed phase reactions using higher-order Trotter factorizations.

    PubMed

    Vardi-Kilshtain, Alexandra; Azuri, Asaf; Major, Dan Thomas

    2012-02-01

    A convenient approach to compute kinetic isotope effects (KIEs) in condensed phase chemical reactions is via path integrals (PIs). Usually, the primitive approximation is used in PI simulations, although such quantum simulations are computationally demanding. The efficiency of PI simulations may be greatly improved, if higher-order Trotter factorizations of the density matrix operator are used. In this study, we use a higher-order PI method, in conjunction with mass-perturbation, to compute heavy-atom KIE in the decarboxylation of orotic acid in explicit sulfolane solvent. The results are in good agreement with experiment and show that the mass-perturbation higher-order Trotter factorization provides a practical approach for computing condensed phase heavy-atom KIE.

  13. Purification and Characterization of OleA from Xanthomonas campestris and Demonstration of a Non-decarboxylative Claisen Condensation Reaction

    SciTech Connect

    Frias, JA; Richman, JE; Erickson, JS; Wackett, LP

    2011-03-25

    OleA catalyzes the condensation of fatty acyl groups in the first step of bacterial long-chain olefin biosynthesis, but the mechanism of the condensation reaction is controversial. In this study, OleA from Xanthomonas campestris was expressed in Escherichia coli and purified to homogeneity. The purified protein was shown to be active with fatty acyl-CoA substrates that ranged from C(8) to C(16) in length. With limiting myristoyl-CoA (C(14)), 1 mol of the free coenzyme A was released/mol of myristoyl-CoA consumed. Using [(14)C] myristoyl-CoA, the other products were identified as myristic acid, 2-myristoylmyristic acid, and 14-heptacosanone. 2-Myristoylmyristic acid was indicated to be the physiologically relevant product of OleA in several ways. First, 2-myristoylmyristic acid was the major condensed product in short incubations, but over time, it decreased with the concomitant increase of 14-heptacosanone. Second, synthetic 2-myristoylmyristic acid showed similar decarboxylation kinetics in the absence of OleA. Third, 2-myristoylmyristic acid was shown to be reactive with purified OleC and OleD to generate the olefin 14-heptacosene, a product seen in previous in vivo studies. The decarboxylation product, 14-heptacosanone, did not react with OleC and OleD to produce any demonstrable product. Substantial hydrolysis of fatty acyl-CoA substrates to the corresponding fatty acids was observed, but it is currently unclear if this occurs in vivo. In total, these data are consistent with OleA catalyzing a non-decarboxylative Claisen condensation reaction in the first step of the olefin biosynthetic pathway previously found to be present in at least 70 different bacterial strains.

  14. Beyond Chemoselectivity: Catalytic Site-Selective Aldolization of Diketones and Exploitation for Enantioselective Alzheimer's Drug Candidate Synthesis.

    PubMed

    Nugent, Thomas C; Najafian, Foad Tehrani; Hussein, Hussein Ali El Damrany; Hussain, Ishtiaq

    2016-09-26

    Site selectivity, differentiating instances of the same functional group type on one substrate, represents a forward-looking theme within chemistry: reduced dependence on protection/deprotection protocols for increased overall yield and step-efficiency. Despite these potential benefits and the expanded tactical advantages afforded to synthetic design, site selectivity remains elusive and especially so for ketone-based substrates. Herein, site-selective intermolecular mono-aldolization has been demonstrated for an array of prochiral 4-keto-substituted cyclohexanones with concomitant regio-, diastereo-, and enantiocontrol. Importantly, the aldol products allow rapid access to molecularly complex ketolactones or keto-1,3-diols, respectively containing three and four stereogenic centers. The reaction conditions are of immediate practical value and general enough to be applicable to other reaction types. These findings are applied in the first enantioselective, formal, synthesis of a leading Alzheimer's research drug, a γ-secretase modulator (GSM), in the highest known yield. PMID:27546719

  15. The synthesis of a bifunctional copper metal organic framework and its application in the aerobic oxidation/Knoevenagel condensation sequential reaction.

    PubMed

    Miao, Zongcheng; Luan, Yi; Qi, Chao; Ramella, Daniele

    2016-09-21

    A novel one-pot aerobic oxidation/Knoevenagel condensation reaction system was developed employing a Cu(ii)/amine bifunctional, basic metal-organic framework (MOF) as the catalyst. The sequential aerobic alcohol oxidation/Knoevenagel condensation reaction was efficiently promoted by the Cu3TATAT MOF catalyst in the absence of basic additives. The benzylidenemalononitrile product was produced in high yield and selectivity from an inexpensive benzyl alcohol starting material under an oxygen atmosphere. The role of the basic functionality was studied to demonstrate its role in the aerobic oxidation and Knoevenagel condensation reactions. The reaction progress was monitored in order to identify the reaction intermediate and follow the accumulation of the desired product. Lastly, results showed that the yield was not significantly compromised by the reuse of a batch of catalyst, even after more than five cycles.

  16. The synthesis of a bifunctional copper metal organic framework and its application in the aerobic oxidation/Knoevenagel condensation sequential reaction.

    PubMed

    Miao, Zongcheng; Luan, Yi; Qi, Chao; Ramella, Daniele

    2016-09-21

    A novel one-pot aerobic oxidation/Knoevenagel condensation reaction system was developed employing a Cu(ii)/amine bifunctional, basic metal-organic framework (MOF) as the catalyst. The sequential aerobic alcohol oxidation/Knoevenagel condensation reaction was efficiently promoted by the Cu3TATAT MOF catalyst in the absence of basic additives. The benzylidenemalononitrile product was produced in high yield and selectivity from an inexpensive benzyl alcohol starting material under an oxygen atmosphere. The role of the basic functionality was studied to demonstrate its role in the aerobic oxidation and Knoevenagel condensation reactions. The reaction progress was monitored in order to identify the reaction intermediate and follow the accumulation of the desired product. Lastly, results showed that the yield was not significantly compromised by the reuse of a batch of catalyst, even after more than five cycles. PMID:27523776

  17. The Formation Of Glycerol Monodecanoate By A Dehydration Condensation Reaction: Increasing The Chemical Complexity Of Amphiphiles On The Early Earth

    NASA Astrophysics Data System (ADS)

    Apel, Charles L.; Deamer, David W.

    2005-08-01

    Dehydration/condensation reactions between organic molecules in the prebiotic environment increased the inventory and complexity of organic compounds available for self-assembly into primitive cellular organisms. As a model of such reactions and to demonstrate this principle, we have investigated the esterification reaction between glycerol and decanoic acid that forms glycerol monodecanoate (GMD). This amphiphile enhances robustness of self-assembled membranous structures of carboxylic acids to the potentially disruptive effects of pH, divalent cation binding and osmotic stress. Experimental variables included temperature, water activity and hydrolysis of the resulting ester product, providing insights into the environmental conditions that would favor the formation and stability of this more evolved amphiphile. At temperatures exceeding 50 ∘C, the ester product formed even in the presence of bulk water, suggesting that the reaction occurs at the liquid interface of the two reactants and that the products segregate in the two immiscible layers, thereby reducing hydrolytic back reactions. This implies that esterification reactions were likely to be common in the prebiotic environment as reactants underwent cycles of wetting and drying on rare early landmasses at elevated temperatures

  18. Effects of water on reactions for waste treatment, organic synthesis, and bio-refinery in sub- and supercritical water.

    PubMed

    Akizuki, Makoto; Fujii, Tatsuya; Hayashi, Rumiko; Oshima, Yoshito

    2014-01-01

    Current research analyzing the effects of water in the field of homogeneous and heterogeneous reactions of organics in sub- and supercritical water are reviewed in this article. Since the physical properties of water (e.g., density, ion product and dielectric constants) can affect the reaction rates and mechanisms of various reactions, understanding the effects that water can have is important in controlling reactions. For homogeneous reactions, the effects of water on oxidation, hydrolysis, aldol condensation, Beckman rearrangement and biomass refining were introduced including recent experimental results up to 100 MPa using special pressure-resistance equipment. For heterogeneous reactions, the effects of ion product on acid/base-catalyzed reactions, such as hydrothermal conversion of biomass-related compounds, organic synthesis in the context of bio-refinery, and hydration of olefins were described and how the reaction paths are controlled by the concentration of water and hydrogen ions was summarized.

  19. Au@Cu(II)-MOF: Highly Efficient Bifunctional Heterogeneous Catalyst for Successive Oxidation-Condensation Reactions.

    PubMed

    Wang, Jing-Si; Jin, Fa-Zheng; Ma, Hui-Chao; Li, Xiao-Bo; Liu, Ming-Yang; Kan, Jing-Lan; Chen, Gong-Jun; Dong, Yu-Bin

    2016-07-01

    A new composite Au@Cu(II)-MOF catalyst has been synthesized via solution impregnation and full characterized by HRTEM, SEM-EDS, XRD, gas adsorption-desorption, XPS, and ICP analysis. It has been shown here that the Cu(II)-framework can be a useful platform to stabilize and support gold nanoparticles (Au NPs). The obtained Au@Cu(II)-MOF exhibits a bifunctional catalytic behavior and is able to promote selective aerobic benzyl alcohol oxidation-Knoevenagel condensation in a stepwise way. PMID:27322613

  20. Linked strategy for the production of fuels via formose reaction

    PubMed Central

    Deng, Jin; Pan, Tao; Xu, Qing; Chen, Meng-Yuan; Zhang, Ying; Guo, Qing-Xiang; Fu, Yao

    2013-01-01

    Formose reaction converts formaldehyde to carbohydrates. We found that formose reaction can be used linking the biomass gasification with the aqueous-phase processing (APP) to produce liquid transportation fuel in three steps. First, formaldehyde from syn-gas was converted to triose. This was followed by aldol condensation and dehydration to 4-hydroxymethylfurfural (4-HMF). Finally, 4-HMF was hydrogenated to produce 2,4-dimethylfuran (2,4-DMF) or C9-C15 branched-chain alkanes as liquid transportation fuels. In the linked strategy, high energy-consuming pretreatment as well as expensive and polluting hydrolysis of biomass were omitted, but the high energy recovery of APP was inherited. In addition, the hexoketoses via formose reaction could be converted to HMFs directly without isomerization. A potential platform molecule 4-HMF was formed simultaneously in APP. PMID:23393625

  1. Linked strategy for the production of fuels via formose reaction.

    PubMed

    Deng, Jin; Pan, Tao; Xu, Qing; Chen, Meng-Yuan; Zhang, Ying; Guo, Qing-Xiang; Fu, Yao

    2013-01-01

    Formose reaction converts formaldehyde to carbohydrates. We found that formose reaction can be used linking the biomass gasification with the aqueous-phase processing (APP) to produce liquid transportation fuel in three steps. First, formaldehyde from syn-gas was converted to triose. This was followed by aldol condensation and dehydration to 4-hydroxymethylfurfural (4-HMF). Finally, 4-HMF was hydrogenated to produce 2,4-dimethylfuran (2,4-DMF) or C(9)-C(15) branched-chain alkanes as liquid transportation fuels. In the linked strategy, high energy-consuming pretreatment as well as expensive and polluting hydrolysis of biomass were omitted, but the high energy recovery of APP was inherited. In addition, the hexoketoses via formose reaction could be converted to HMFs directly without isomerization. A potential platform molecule 4-HMF was formed simultaneously in APP. PMID:23393625

  2. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

    PubMed Central

    Van Wyngarden, A. L.; Pérez-Montaño, S.; Bui, J. V. H.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.

    2016-01-01

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40–80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance–Fourier transform infrared (ATR-FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and

  3. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

    NASA Astrophysics Data System (ADS)

    Van Wyngarden, A. L.; Pérez-Montaño, S.; Bui, J. V. H.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.

    2014-11-01

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, Attenuated Total Reflectance-Fourier Transform Infrared and 1H Nuclear Magnetic Resonance spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene, which was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence for products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and methylglyoxal

  4. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

    NASA Astrophysics Data System (ADS)

    Van Wyngarden, A. L.; Pérez-Montaño, S.; Bui, J. V. H.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.

    2015-04-01

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt%) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and

  5. Models of glycolysis: Glyceraldehyde as a source of energy and monomers for prebiotic condensation reactions

    NASA Technical Reports Server (NTRS)

    Weber, A. L.

    1986-01-01

    All organisms require energy in a chemical form for maintenance and growth. In contemporary life this chemical energy is obtained by the synthesis of the phosphoanhydride bonds of ATP. Among the biological processes that yield ATP, fermentation is generally considered primitive, because it operates under anaerobic conditions by substrate-level phosphorylation which does not require compartmentation by membranes. Fermentation by the glycolytic pathway, which is found in almost every living cell, is an especially attractive energy source for primitive life. Glycolysis not only produces useful chemical energy (ATP), but intermediates of this pathway are also involved in amino acid synthesis and photosynthetic carbon-fixation. It is believed that energy and substrates needed for the origin of life were provided by nonenzymatic chemical reactions that resemble the enzyme-mediated reactions of glycolysis. These nonenzymatic reactions would have provided a starting point for the evolutionary development of glycolysis.

  6. Reaction engineering of co-condensing (methyl)ethoxysilane mixtures: Kinetic characterization and modeling

    SciTech Connect

    RANKIN,STEPHEN E.; MCCORMICK,ALON V.

    2000-01-26

    Molecular homogeneity frequently plays a decisive role in the effective application of organically modified silicate copolymers. However, methods of directly characterizing copolymerization extent in siloxanes generated from mixed alkoxysilanes are not always available or convenient. The authors present an alternative tool for determining kinetic parameters for models of alkoxysilane hydrolytic copolycondensation. Rather than restricting attention to single step batch reactors, they use a semibatch reactor with varying time of injection of one component. They describe the fitting method and show that all necessary kinetic parameters can be determined from a series of ordinary {sup 29}Si NMR data in a straightforward case study: copolymerization of dimethyldiethoxy silane and trimethylethoxysilane. Under conditions providing no direct {sup 29}Si NMR signature of copolymerization, they find kinetic trends consistent with those previously reported. As further validation, the results of a new series of experiments (varying the ratio of mono-functional to difunctional monomer) are predicted by the semibatch copolymerization model and measured parameters. Based on these results, they are able to calculate the molecular homogeneity in the copolymer products investigated. Even for this relatively simple system, the optimal injection time is a complex function of residence time, but early injection of the faster-condensing monomer gives the best homogeneity at long residence times.

  7. Gold-catalyzed construction of two adjacent quaternary stereocenters via sequential C-H functionalization and aldol annulation.

    PubMed

    Yu, Zhunzhun; Qiu, Haile; Liu, Lu; Zhang, Junliang

    2016-02-01

    Herein, a novel and efficient gold-catalyzed intermolecular C(sp(2))-H functionalization (Friedel-Crafts alkylation) and aldol annulation strategy is presented. This cascade process allows the synthesis of a series of indanol and tetrahydronaphthalenol derivatives with two adjacent quaternary stereocenters. The attractive reaction features are the use of readily available starting materials, good diastereoselectivity, good functional-group tolerance and mild reaction conditions. Furthermore, preliminary results indicate that this transformation is amenable to enantioselectivitive synthesis with further chiral ligand screening and design. PMID:26725981

  8. High-pressure matrix isolation of heterogeneous condensed phase chemical reactions under extreme conditions

    NASA Astrophysics Data System (ADS)

    Rice, Jane K.; Russell, T. P.

    1995-03-01

    A new technique which combines high-pressure and thermal-shock conditions with low-temperature matrix isolation in a gem anvil cell is presented. This serves to partially quench or arrest the reaction sequence of an energetic material. New chemical species are observed which indicate that intermediates are trapped in addition to final products. This combination of high pressure and low temperature helps elucidate the complicated reaction pathways in the deflagration to detonation regime. We have applied this technique to hexanitrohexaazaisowurtzitane (HNIW, chemical name: 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0 5,9.0 3,11]dodecane). Products are identified using infrared spectroscopy and comparisons are made to previously reported data taken under thermal, ambient pressure conditions.

  9. Condensation reactions of guanidines with bis-electrophiles: Formation of highly nitrogenous heterocyclesa

    PubMed Central

    Arnold, David M.; LaPorte, Matthew G.; Anderson, Shelby M.; Wipf, Peter

    2013-01-01

    2-Amino-1,4-dihydropyrimidines were reacted with bis-electrophiles to produce novel fused bi-pyrimidine, pyrimido-aminotriazine, and pyrimido-sulfonamide scaffolds. In addition, a quinazoline library was constructed using a guanidine Atwal-Biginelli reaction with 1-(quinazolin-2-yl)guanidines. The product heterocycles have novel constitutions with high nitrogen atom counts and represent valuable additions to screening libraries for the discovery of new modulators of biological targets. PMID:23976798

  10. Experimental evidence for condensation reactions between sugars and proteins in carbonate skeletons

    NASA Astrophysics Data System (ADS)

    Collins, M. J.; Westbroek, P.; Muyzer, G.; de Leeuw, J. W.

    1992-04-01

    Melanoidins, condensation products formed from protein and polysaccharide precursors, were once thought to be an important geological sink for organic carbon. The active microbial recycling of the precursors, coupled with an inability to demonstrate the formation of covalent linkages between amino acids and sugars in melanoidins, has shaped a powerful argument against this view. Yet, melanoidins may still be an abundant source of macromolecules in fossil biominerals such as shells, in which the proteins and polysaccharides are well protected from microbial degradation. We have modelled diagenetic changes in a biomineral by heating at 90°C mixtures of protein, polysaccharides and finely ground calcite crystals in sealed glass vials. Changes to the protein bovine serum albumin (BSA, fraction V) were monitored by means of gel electrophoresis and immunology. In the presence of water, BSA was rapidly hydrolyzed and remained immunologically reactive for less than 9 h. Under anhydrous conditions the protein was immunologically reactive for the whole period of the experiment (1281 h), unless mono- or disaccharide sugars were also present. In the presence of these reactive sugars, browning, a discrete increase in molecular weight of the protein and a concomitant loss of antigenicity confirmed that the sugars were attaching covalently to the protein, forming melanoidins. The de novo formation of products cross-reactive with antibodies raised against organic matter isolated from the shells of a fossil mollusc ( Mercenaria mercenaria) indicated that at least in part the model simulated natural diagenesis. We roughly estimate that, at the global scale, 2.4 × 10 6 tonnes of calcified tissue matrix glycoproteins is processed annually through the melanoidin pathway. This amount would be equivalent to 7 per mil of the total flux of organic carbon into marine sediments.

  11. Possible mechanism of structural incorporation of Al into diatomite during the deposition process I. Via a condensation reaction of hydroxyl groups.

    PubMed

    Liu, Dong; Yu, Wenbin; Deng, Liangliang; Yuan, Weiwei; Ma, Lingya; Yuan, Peng; Du, Peixin; He, Hongping

    2016-01-01

    The structural incorporation of aluminium (Al) into diatomite is investigated by preparing several Al-diatomite composites by loading an Al precursor, hydroxyl aluminum polymer (Al13), onto the surface of diatomite and heating at various temperatures. The results indicate that Al was incorporated and implanted into the structure of diatomite by the condensation reaction of the hydroxyl groups of Al13 and diatomite, and the Si-O-Al(OH) groups were formed during the condensation reaction. Al incorporation by the condensation reaction of hydroxyl groups of Al13 with single silanols of diatomite occurred more readily than that with geminal silanols. The Al incorporation increased solid acidity of diatomite after Al incorporation. The acidity improvement was various for different types of acid sites, depending on the preparation temperature of the Al-incorporated diatomite. Both Brønsted and Lewis acid sites increased greatly after heating at 250 and 350 °C, but only L acid sites significantly improved after heating at 500 °C. These results demonstrate that the structural incorporation of Al(3+) ions into diatomite can occur by the condensation reaction of the hydroxyl groups of the Al precursors and diatomite. Moreover, the rich solid acid sites of Al-incorporated diatomite show its promising application as a solid acid catalyst.

  12. An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Quarterly progress report, July 1, 1992--September 30, 1992

    SciTech Connect

    Miknis, F.P.

    1992-10-01

    Changes in coal structure that occur during coal drying and steam pretreatments will be measured in order to determine what effect water has on retrograde/condensation reactions, and to determine how water enhances coal reactivity toward liquefaction. Coal drying experiments were begun using thermal, microwave, and chemical methods; NMR data were collected. A stirred microautoclave reactor system was acquired.

  13. Vapor-phase reaction of acetophenone with methanol or dimethyl carbonate on magnesium oxide and magnesium phosphates

    SciTech Connect

    Aramendia, M.A.; Borau, V.; Jimenez, C.; Marinas, J.M.; Romero, F.J.

    1999-04-01

    The vapor-phase reaction of acetophenone with methanol on magnesium oxide, various magnesium phosphates, and combinations of the two types of catalysts was studied. The process was found to involve the Meerwein-Ponndorf-Verley reaction, aldol condensations, dehydrations, and hydrogenations. The presence of basic sites is indispensable for the reaction to develop; however, acid sites also play an active role. The selectivity for each reaction product depends on the particular catalyst used. The total conversion is maximal with the catalysts containing the largest populations of acid and basic sites. Also, catalysts with large numbers of acid sites exhibit an increased selectivity towards the corresponding alkenes. The use of dimethyl carbonate instead of methanol alters the reaction selectivity to an extent dependent on the particular catalyst and operating conditions. However, this also results in markedly decreased total conversion in some instances.

  14. Intramolecular condensation reactions of {alpha},{omega}-bis(triethoxysilyl)alkanes. Formation of cyclic disilsesquioxanes

    SciTech Connect

    Loy, D.A.; Carpenter, J.P.; Myers, S.A.; Assink, R.A.; Small, J.H.; Greaves, J.; Shea, K.J.

    1996-09-04

    In this paper, we used mass spectrometry and {sup 29}Si NMR spectroscopy to discover that the length of the alkylene-bridging groups had a pronounced effect on the competition between cyclization and polymerization of {alpha},{omega}-bis(triethoxysilyl)alkanes and on the formation of polymeric gels. While the intramolecular reaction clearly slows gelation, the cyclic disilsesquioxanes are still tetrafunctional monomers theoretically capable of forming polymeric gels. If the ring structures, which bear a striking resemblence to carbohydrates, are preserved through the polymerization, the resulting poly(cyclic disilsesquioxane) gels may have structural similarities to branched or cross-linked carbohydrates, such as cellulose or chitosan. Under base-catalyzed sol-gel polymerization conditions, 3 and 4 (six- and seven-membered cyclic disilsesquioxanes, respectively) quickly reacted to give gels with significant ring opening as determined from the {sup 29}Si chemical shifts in solid-state (CP MAS) NMR spectra. However, gels prepared under acidic conditions reveal some or all of the cyclic disilsesquioxane functionality was preserved in the polymers. 13 refs., 1 fig.

  15. Catalytic solid substrate room temperature phosphorimetry for the determination of trace rhamnose based on its condensation reaction with calcein

    NASA Astrophysics Data System (ADS)

    Liu, Jia-Ming; Lin, Li-Ping; Wang, Hong-Xin; Lin, Shao-Qin; Zhang, Li-Hong; Cai, Wen-Lian; Lin, Xuan; Pan, You-Zhu; Wang, Xin-Xing; Li, Zhi-Ming; Jiao, Li; Cui, Ma-Lin

    2011-12-01

    Calcein (R) could not only emit strong and stable room temperature phosphorescence (RTP) on filter paper using I - as perturber, but also could be oxidized by H 2O 2 to form a non-phosphorescence compound (R'), resulting in the quenching of RTP signal of R. Moreover, the ortho-hydrogen of phenolic hydroxyl in R took condensation reaction with rhamnose (Rha) to produce non-phosphorescence compound (R-Rha) causing the RTP signal of R to further quench, and R-Rha was oxidized by H 2O 2 to form R' and Rha, bringing about the sharp RTP signal quenching of R. Thus, a new solid substrate room temperature phosphorimetry (SSRTP) for the determination of trace Rha based on its strong catalytic effect on H 2O 2 oxidizing R has been established, with the detection limit (LD) of 7.8 zg spot -1 (corresponding concentration: 2.0 × 10 -17 g ml -1, sample volume: 0.40 μl spot -1). This method has been applied to determine trace Rha in cigarettes and jujubes, with the results coinciding well with those determined by a high performance liquid chromatography (HPLC). The component of R-Rha also was analyzed by means of HPLC, mass spectrometer and nuclear magnetic resonance (NMR) measurements. The mechanism of catalytic SSRTP for the determination of trace Rha was discussed.

  16. Prediction of Activity Cliffs Using Condensed Graphs of Reaction Representations, Descriptor Recombination, Support Vector Machine Classification, and Support Vector Regression.

    PubMed

    Horvath, Dragos; Marcou, Gilles; Varnek, Alexandre; Kayastha, Shilva; de la Vega de León, Antonio; Bajorath, Jürgen

    2016-09-26

    Activity cliffs (ACs) are formed by structurally similar compounds with large differences in activity. Accordingly, ACs are of high interest for the exploration of structure-activity relationships (SARs). ACs reveal small chemical modifications that result in profound biological effects. The ability to foresee such small chemical changes with significant biological consequences would represent a major advance for drug design. Nevertheless, only few attempts have been made so far to predict whether a pair of analogues is likely to represent an AC-and even fewer went further to quantitatively predict how "deep" a cliff might be. This might be due to the fact that such predictions must focus on compound pairs. Matched molecular pairs (MMPs), defined as pairs of structural analogs that are only distinguished by a chemical modification at a single site, are a preferred representation of ACs. Herein, we report new strategies for AC prediction that are based upon two different approaches: (i) condensed graphs of reactions, which were originally introduced for modeling of chemical reactions and were here adapted to encode MMPs, and, (ii) plain descriptor recombination-a strategy used for quantitative structure-property relationship (QSPR) modeling of nonadditive mixtures (MQSPR). By applying these concepts, ACs were encoded as single descriptor vectors used as input for support vector machine (SVM) classification and support vector regression (SVR), yielding accurate predictions of AC status (i.e., cliff vs noncliff) and potency differences, respectively. The latter were predicted in a compound order-sensitive manner returning the signed value of expected potency differences between AC compounds. PMID:27564682

  17. Prediction of Activity Cliffs Using Condensed Graphs of Reaction Representations, Descriptor Recombination, Support Vector Machine Classification, and Support Vector Regression.

    PubMed

    Horvath, Dragos; Marcou, Gilles; Varnek, Alexandre; Kayastha, Shilva; de la Vega de León, Antonio; Bajorath, Jürgen

    2016-09-26

    Activity cliffs (ACs) are formed by structurally similar compounds with large differences in activity. Accordingly, ACs are of high interest for the exploration of structure-activity relationships (SARs). ACs reveal small chemical modifications that result in profound biological effects. The ability to foresee such small chemical changes with significant biological consequences would represent a major advance for drug design. Nevertheless, only few attempts have been made so far to predict whether a pair of analogues is likely to represent an AC-and even fewer went further to quantitatively predict how "deep" a cliff might be. This might be due to the fact that such predictions must focus on compound pairs. Matched molecular pairs (MMPs), defined as pairs of structural analogs that are only distinguished by a chemical modification at a single site, are a preferred representation of ACs. Herein, we report new strategies for AC prediction that are based upon two different approaches: (i) condensed graphs of reactions, which were originally introduced for modeling of chemical reactions and were here adapted to encode MMPs, and, (ii) plain descriptor recombination-a strategy used for quantitative structure-property relationship (QSPR) modeling of nonadditive mixtures (MQSPR). By applying these concepts, ACs were encoded as single descriptor vectors used as input for support vector machine (SVM) classification and support vector regression (SVR), yielding accurate predictions of AC status (i.e., cliff vs noncliff) and potency differences, respectively. The latter were predicted in a compound order-sensitive manner returning the signed value of expected potency differences between AC compounds.

  18. Engineering stereocontrol into an aldolase-catalysed reaction.

    PubMed

    Lamble, Henry J; Danson, Michael J; Hough, David W; Bull, Steven D

    2005-01-01

    A novel thermostable aldolase has been developed for synthetic application, and substrate engineering has been used to induce stereocontrol into aldol reactions of this naturally-promiscuous enzyme. PMID:15614394

  19. Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions.

    PubMed

    Brun, Elodie; Safer, Abdelmounaim; Carreaux, François; Bourahla, Khadidja; L'helgoua'ch, Jean-Martial; Bazureau, Jean-Pierre; Villalgordo, Jose Manuel

    2015-06-23

    We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups.

  20. One-Pot Synthesis of N-(α-Peroxy)Indole/Carbazole via Chemoselective Three-Component Condensation Reaction in Open Atmosphere.

    PubMed

    Wang, Xinbo; Pan, Yupeng; Huang, Kuo-Wei; Lai, Zhiping

    2015-11-20

    A facile one-pot synthesis of N-(α-peroxy)indole and N-(α-peroxy)carbazole has been developed using metal-free, organo-acid-catalyzed three-component condensation reactions of indole/carbazole, aldehyde, and peroxide. Based on the reaction discovered, a new synthetic proposal for Fumitremorgin A and Verruculogen is introduced. Such a protocol could be easily handled and scaled up in an open atmosphere with a wide substrate scope, enabling the construction of a new molecule library. PMID:26541059

  1. Interstellar silicate analogs for grain-surface reaction experiments: Gas-phase condensation and characterization of the silicate dust grains

    SciTech Connect

    Sabri, T.; Jäger, C.; Gavilan, L.; Lemaire, J. L.; Vidali, G.; Henning, T.

    2014-01-10

    Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destruction of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4}, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H{sub 2} formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4} described in this paper will be the topic of the next paper of this series.

  2. Rational nanoconjugation improves biocatalytic performance of enzymes: aldol addition catalyzed by immobilized rhamnulose-1-phosphate aldolase.

    PubMed

    Ardao, Inés; Comenge, Joan; Benaiges, M Dolors; Álvaro, Gregorio; Puntes, Víctor F

    2012-04-17

    Gold nanoparticles (AuNPs) are attractive materials for the immobilization of enzymes due to several advantages such as high enzyme loading, absence of internal diffusion limitations, and Brownian motion in solution, compared to the conventional immobilization onto porous macroscopic supports. The affinity of AuNPs to different groups present at the protein surface enables direct enzyme binding to the nanoparticle without the need of any coupling agent. Enzyme activity and stability appear to be improved when the biocatalyst is immobilized onto AuNPs. Rhamnulose-1-phosphate aldolase (RhuA) was selected as model enzyme for the immobilization onto AuNPs. The enzyme loading was characterized by four different techniques: surface plasmon resonance (SPR) shift and intensity, dynamic light scattering (DLS), and transmission electron microscopy (TEM). AuNPs-RhuA complexes were further applied as biocatalyst of the aldol addition reaction between dihydroxyacetone phosphate (DHAP) and (S)-Cbz-alaninal during two reaction cycles. In these conditions, an improved reaction yield and selectivity, together with a fourfold activity enhancement were observed, as compared to soluble RhuA. PMID:22428999

  3. Transport-induced shifts in condensate dew-point and composition in multicomponent systems with chemical reaction

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Nagarajan, R.

    1985-01-01

    Partial heterogeneous condensation phenomena in multicomponent reacting systems are analyzed taking into consideration the chemical element transport phenomena. It is demonstrated that the dew-point surface temperature in chemically reactive systems is not a purely thermodynamic quantity, but is influenced by the multicomponent diffusion and Soret-mass diffusion phenomena. Several distinct dew-points are shown to exist in such systems and, as a result of transport constraints, the 'sharp' locus between two chemically distinct condensates is systematically moved to a difference mainstream composition.

  4. Preparation and confinement effect of a heterogeneous 9-amino-9-deoxy-epi-cinchonidine organocatalyst for asymmetric aldol addition in aqueous medium.

    PubMed

    Wang, Wei; Ma, Xuebing; Wan, Jingwei; Cao, Jun; Tang, Qian

    2012-05-14

    A series of novel porous zirconium phosphonate-supported 9-amino-9-deoxy-epi-cinchonidines of general formulae Zr(OH)(4-2x)(O(3)PR)(x)·nH(2)O and Zr(HPO(4))(2-x)(O(3)PR)(x)·nH(2)O with the different arm chain lengths (n = 2-6) and mean diameters of approximately 20-40 nm have been prepared as heterogeneous organocatalysts. The different microtextures of zirconium phosphonates were also obtained by using template guest molecules, such as Et(3)N, NaH(2)PO(4) and sodium dodecyl benzene sulfonate. In the heterogeneous asymmetric aldol addition of p-nitrobenzaldehyde to cyclohexanone, excellent catalytic properties were achieved, especially in an aqueous medium. After completing the reaction, those zirconium phosphonate-supported 9-amino-9-deoxy-epi-cinchonidine organocatalysts could be readily recovered in quantitative yield by centrifugation or filtration, and reused for five consecutive runs without significant loss in catalytic performance. In particular, due to the steric confinement effect of the inorganic backbone, the single different configuration among possible four stereo-isomers in aldol adducts were favorably obtained, respectively depending on the interaction between the o-, m- or p-position of nitrobenzaldehyde and the backbone, which was never observed in homogeneous aldol addition.

  5. NUMERICAL TECHNIQUES TO SOLVE CONDENSATIONAL AND DISSOLUTIONAL GROWTH EQUATIONS WHEN GROWTH IS COUPLED TO REVERSIBLE REACTIONS (R823186)

    EPA Science Inventory

    Noniterative, unconditionally stable numerical techniques for solving condensational and
    dissolutional growth equations are given. Growth solutions are compared to Gear-code solutions for
    three cases when growth is coupled to reversible equilibrium chemistry. In all cases, ...

  6. The formation of glycerol monodecanoate by a dehydration/condensation reaction: increasing the chemical complexity of amphiphiles on the early earth

    NASA Astrophysics Data System (ADS)

    Apel, C. L.; Deamer, D. W.

    Dehydration/condensation reactions between organic molecules in the prebiotic environment increased the inventory and complexity of organic compounds available for self-assembly into protocellular structures. As a model of such reactions, we have investigated the esterification reaction between glycerol and decanoic acid that forms glycerol monodecanoate. This amphiphile enhances robustness of self-assembled membranous structures of carboxylic acids to the potentially disruptive effects of pH, divalent cation binding and osmotic stress. Experimental variables included temperature, water activity and hydrolysis of the resulting ester product, providing insights into the environmental conditions that would favour the formation and stability of this more evolved amphiphile. At temperatures exceeding 500 C, the ester product formed even in the presence of bulk water, suggesting that the reaction occurs at the liquid interface of the two reactants and that the products segregate in the two immiscible layers, thereby reducing the rate of the hydrolytic back reaction. This suggests that esterification reactions were likely to commonly occur in the prebiotic environment as available reactants underwent cycles of wetting and drying on early landmasses at elevated temperatures.

  7. Estimation of the Number of Cross-Links of Multi-walled Carbon Nanotube Films Formed by a Dehydration Condensation Reaction

    NASA Astrophysics Data System (ADS)

    Ogino, S.; Sato, Y.; Yamamoto, G.; Sasamori, K.; Kimura, H.; Hashida, T.; Motomiiya, K.; Jeyadevan, B.; Tohji, K.

    2007-03-01

    Preparation procedure of multi-walled carbon nanotube (MWCNT) films shows as follows. First, as-grown MWCNTs heated in the air and treated with hydrochloric acid to remove amorphous carbon and catalytic metal particles respectively. Then, the o1btained MWCNT samples were treated with nitric acid at 373K to add carboxylic acid and hydroxyl groups on their surface. Finally, MWCNT films were prepared by employing a condensation reaction utilizing 1,3-dicyclohexylcarbodiimide (DCC) to cross-link each MWCNT with chemical bonds. Morphological changes in the resultant MWCNT films were monitored using scanning electron microscopy, and showed that the MWCNTs were randomly intertwined in the films. The prepared MWCNT films were 17mm in diameter and 20μm in thickness, and the apparent density was 0.59 g/cm3. Fourier transform-infrared spectroscopy confirmed that each MWCNT modified with carboxylic acid and hydroxyl groups was cross-linked through the ester bond. It was found that the ratio of the number of ester cross-links and carbon atoms of the nanotubes per unit apparent volume (cm3) of condensed-MWCNT films was 5.23×10-3 using TGA. The tensile strength and Vickers hardness of condensed-MWCNT films achieved an average of 15MPa and 9.2MPa, respectively, and was greater than those of free-standing MWCNT films without ester bond.

  8. Diastereo- and Enantioselective Reductive Aldol Addition of Vinyl Ketones via Catalytic Hydrogenation

    PubMed Central

    Han, Soo Bong; Hassan, Abbas; Krische, Michael J.

    2011-01-01

    An overview of studies on hydrogenative reductive aldol addition is presented. By simply hydrogenating enones in the presence of aldehydes at ambient temperature and pressure, aldol adducts are generated under neutral conditions in the absence of any stoichiometric byproducts. Using cationic rhodium complexes modified by tri(2-furyl)phosphine, highly syn-diastereoselective reductive aldol additions of vinyl ketones are achieved. Finally, using novel monodentate TADDOL-like phosphonite ligands, the first highly diastereo- and enantioselective reductive aldol couplings of vinyl ketones were devised. These studies, along with other works from our laboratory, demonstrate that organometallics arising transiently in the course of catalytic hydrogenation offer byproduct-free alternatives to preformed organometallic reagents employed in classical carbonyl addition processes. PMID:21866204

  9. Flow injection spectrophotometric determination of formaldehyde based on its condensation with hydroxylamine and subsequent redox reaction with iron(III)-ferrozine complex.

    PubMed

    Teshima, Norio; Fernández, Sara Keiko Murase; Ueda, Minoru; Nakai, Hirokazu; Sakai, Tadao

    2011-06-15

    A flow injection (FI) spectrophotometric method is proposed for the determination of low concentration of formaldehyde (HCHO) in liquid media. It is based on the condensation of HCHO with hydroxylamine sulfate, followed by the reduction reaction of iron(III)-ferrozine complex with the residual hydroxylamine to form a purple iron(II)-ferrozine complex (λ(max)=562 nm). In the first reaction, hydroxylamine decreases proportionally to the concentration of HCHO, and therefore the produced purple iron(II)-ferrozine complex decreases with increasing HCHO (a negative FI peak is obtained). The detection limit (S/N=3) was 1.6 μg L(-1). The method can be applied to the determination of HCHO in industrial wastewater.

  10. Synergistic Effects in Bimetallic Palladium-Copper Catalysts Improve Selectivity in Oxygenate Coupling Reactions.

    PubMed

    Goulas, Konstantinos A; Sreekumar, Sanil; Song, Yuying; Kharidehal, Purnima; Gunbas, Gorkem; Dietrich, Paul J; Johnson, Gregory R; Wang, Y C; Grippo, Adam M; Grabow, Lars C; Gokhale, Amit A; Toste, F Dean

    2016-06-01

    Condensation reactions such as Guerbet and aldol are important since they allow for C-C bond formation and give higher molecular weight oxygenates. An initial study identified Pd-supported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO. PMID:27195582

  11. CYCLODEXTRIN-BASED CLASS I ALDOLASE ENZYME MIMICS TO CATALYZE CROSSED ALDOL CONDENSATIONS. (R826653)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  12. Bifunctional building blocks in the Ugi-azide condensation reaction: A general strategy toward exploration of new molecular diversity†

    PubMed Central

    Gunawan, Steven; Hulme, Christopher

    2013-01-01

    1,5-disubstituted tetrazoles are an important drug-like scaffold known for their ability to mimic the cis-amide bond conformation. The scaffold is readily accessible via substitution of the carboxylic acid component of the Ugi multi-component reaction (MCR) with TMSN3 in what is herein denoted the Ugi-azide reaction. This full paper presents a concise, novel, general strategy to access a plethora of new heterocylic scaffolds utilizing tethered aldo/keto-acids/esters in the Ugi-azide reaction followed by a ring closing event that generates novel highly complex bis-heterocyclic lactam-tetrazoles. PMID:23912086

  13. Ti-direct, powerful, stereoselective aldol-type additions of esters and thioesters to carbonyl compounds: application to the synthesis and evaluation of lactone analogs of jasmone perfumes.

    PubMed

    Nagase, Ryohei; Matsumoto, Noriaki; Hosomi, Kohei; Higashi, Takahiro; Funakoshi, Syunsuke; Misaki, Tomonori; Tanabe, Yoo

    2007-01-01

    An efficient TiCl(4)-Et(3)N or Bu(3)N-promoted aldol-type addition of phenyl and thiophenyl esters or thioaryl esters with aldehydes and ketones was performed (total 46 examples). The present method is advantageous from atom-economical and cost-effective viewpoints; good to excellent yields, moderate to good syn-selectivity, substrate variations, reagent availability, and simple procedures. Utilizing the present reaction as the key step, an efficient short synthesis of three lactone [2(5H)-furanone] analogs of jasmine perfumes was performed. Among them, the lactone analog of cis-jasmone had a unique perfume property (tabac).

  14. Charge-dependent non-bonded interaction methods for use in quantum mechanical modeling of condensed phase reactions

    NASA Astrophysics Data System (ADS)

    Kuechler, Erich R.

    Molecular modeling and computer simulation techniques can provide detailed insight into biochemical phenomena. This dissertation describes the development, implementation and parameterization of two methods for the accurate modeling of chemical reactions in aqueous environments, with a concerted scientific effort towards the inclusion of charge-dependent non-bonded non-electrostatic interactions into currently used computational frameworks. The first of these models, QXD, modifies interactions in a hybrid quantum mechanical/molecular (QM/MM) mechanical framework to overcome the current limitations of 'atom typing' QM atoms; an inaccurate and non-intuitive practice for chemically active species as these static atom types are dictated by the local bonding and electrostatic environment of the atoms they represent, which will change over the course of the simulation. The efficacy QXD model is demonstrated using a specific reaction parameterization (SRP) of the Austin Model 1 (AM1) Hamiltonian by simultaneously capturing the reaction barrier for chloride ion attack on methylchloride in solution and the solvation free energies of a series of compounds including the reagents of the reaction. The second, VRSCOSMO, is an implicit solvation model for use with the DFTB3/3OB Hamiltonian for biochemical reactions; allowing for accurate modeling of ionic compound solvation properties while overcoming the discontinuous nature of conventional PCM models when chemical reaction coordinates. The VRSCOSMO model is shown to accurately model the solvation properties of over 200 chemical compounds while also providing smooth, continuous reaction surfaces for a series of biologically motivated phosphoryl transesterification reactions. Both of these methods incorporate charge-dependent behavior into the non-bonded interactions variationally, allowing the 'size' of atoms to change in meaningful ways with respect to changes in local charge state, as to provide an accurate, predictive and

  15. Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction

    PubMed Central

    Tóth, László; Fu, Yan; Zhang, Hai Yan; Mándi, Attila; Kövér, Katalin E; Illyés, Tünde-Zita; Kiss-Szikszai, Attila; Balogh, Balázs; Kurtán, Tibor

    2014-01-01

    Summary Condensed O,N-heterocycles containing tetrahydro-1,4-benzoxazepine and tetrahydroquinoline moieties were prepared by a regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction of a 4-aryl-2-phenyl-1,4-benzoxazepine derivative obtained from flavanone. The relative configuration of products were determined by the correlation of 3 J H,H coupling data with the geometry of major conformers accessed by DFT conformational analysis. Separated enantiomers of the products were characterized by HPLC-ECD data, which allowed their configurational assignment on the basis of TDDFT-ECD calculation of the solution conformers. Two compounds showed neuroprotective activities against hydrogen peroxide (H2O2) or β-amyloid25–35 (Aβ25–35)-induced cellular injuries in human neuroblastoma SH-SY5Y cells in the range of those of positive controls. PMID:25550721

  16. CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Nanoporous AlN particle production from a solid-state metathesis reaction

    NASA Astrophysics Data System (ADS)

    Yan, Guo-Jun; Chen, Guang-De; Wu, Ye-Long

    2009-07-01

    This paper reports that nanoporous AlN particles are synthesized from solid-state metathesis reactions using AlCl3 and Mg3N2 as reactants. The samples are characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction, high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-vis) absorption spectroscopy and Raman spectroscopy. The results show that samples with walls 10 nm in thickness and pores between 10 nm and 100 nm in diameter were produced successfully from these reactions, and their band gap and vibration modes agree with those of AlN bulk crystal.

  17. Condensation cyclization reactions of electron deficient aromatics. 4: Tricyclic nitropropene nitronates from the reaction of phloroglucinol and cycloalkanones with sym-trinitrobenzene

    NASA Technical Reports Server (NTRS)

    Strauss, M. J.; Taylor, S. P. B.; Shindo, H.

    1972-01-01

    Interesting similarities have been shown between the reactions of sym-trinitrobenzene with cycloalkanones, and with phloroglucinol. Previously unsuspected common intermediates have been shown to intervene. The structurally similar products in each case are tricyclic nitropropene nitronates. Protonation of these yields the corresponding nitronic acids in certain instances.

  18. Steam generators, turbines, and condensers. Volume six

    SciTech Connect

    Not Available

    1986-01-01

    Volume six covers steam generators (How steam is generated, steam generation in a PWR, vertical U-tube steam generators, once-through steam generators, how much steam do steam generators make.), turbines (basic turbine principles, impulse turbines, reaction turbines, turbine stages, turbine arrangements, turbine steam flow, steam admission to turbines, turbine seals and supports, turbine oil system, generators), and condensers (need for condensers, basic condenser principles, condenser arrangements, heat transfer in condensers, air removal from condensers, circulating water system, heat loss to the circulating water system, factors affecting condenser performance, condenser auxiliaries).

  19. Understanding the mechanism of stereoselective synthesis of cyclopentenes via N-heterocyclic carbene catalyzed reactions of enals with enones.

    PubMed

    Domingo, Luis R; Zaragozá, Ramón J; Arnó, Manuel

    2010-11-01

    The N-heterocyclic carbene (NHC) catalyzed addition of enals to enones to yield trans-cyclopentenes has been investigated using DFT methods at B3LYP/6-31G** computational level. This NHC catalyzed reaction comprises several steps. The first one is the formation of a Breslow intermediate, which nucleophilically attacks to the conjugated position of the enone to yield an enol-enolate. This second step is responsible for the trans relationship at the final cyclopentene. An intramolecular aldolic condensation allows for the formation of the alkoxy cyclopentane intermediate, that by intramolecular nucleophilic attack on the carbonyl group yields a bicyclic ether. The extrusion of the NHC catalyst affords a bicyclic lactone, yielding by CO(2) elimination, the final trans-cyclopentene.

  20. Heterogeneous ceria catalyst with water-tolerant Lewis acidic sites for one-pot synthesis of 1,3-diols via Prins condensation and hydrolysis reactions.

    PubMed

    Wang, Yehong; Wang, Feng; Song, Qi; Xin, Qin; Xu, Shutao; Xu, Jie

    2013-01-30

    The use of a heterogeneous Lewis acid catalyst, which is insoluble and easily separable during the reaction, is a promising option for hydrolysis reactions from both environmental and practical viewpoints. In this study, ceria showed excellent catalytic activity in the hydrolysis of 4-methyl-1,3-dioxane to 1,3-butanediol in 95% yield and in the one-pot synthesis of 1,3-butanediol from propylene and formaldehyde via Prins condensation and hydrolysis reactions in an overall yield of 60%. In-depth investigations revealed that ceria is a water-tolerant Lewis acid catalyst, which has seldom been reported previously. The ceria catalysts showed rather unusual high activity in hydrolysis, with a turnover number (TON) of 260, which is rather high for bulk oxide catalysts, whose TONs are usually less than 100. Our conclusion that ceria functions as a Lewis acid catalyst in hydrolysis reactions is firmly supported by thorough characterizations with IR and Raman spectroscopy, acidity measurements with IR and (31)P magic-angle-spinning NMR spectroscopy, Na(+)/H(+) exchange tests, analyses using the in situ active-site capping method, and isotope-labeling studies. A relationship between surface vacancy sites and catalytic activity has been established. CeO(2)(111) has been confirmed to be the catalytically active crystalline facet for hydrolysis. Water has been found to be associatively adsorbed on oxygen vacancy sites with medium strength, which does not lead to water dissociation to form stable hydroxides. This explains why the ceria catalyst is water-tolerant. PMID:23228093

  1. Development of a Simple Adjustable Zinc Acid/Base Hybrid Catalyst for C-C and C-O Bond-Forming and C-C Bond-Cleavage Reactions.

    PubMed

    Yamashita, Yasuhiro; Minami, Kodai; Saito, Yuki; Kobayashi, Shū

    2016-09-01

    A newly designed zinc Lewis acid/base hybrid catalyst was developed. By adjusting the Lewis acidity of the zinc center, aldol-type additions of 2-picolylamine Schiff base to aldehydes proceeded smoothly to afford syn-aldol adduct equivalents, trans-N,O-acetal adducts, in high yields with high selectivities. NMR experiments, including microchanneled cell for synthesis monitoring (MICCS) NMR analysis, revealed that anti-aldol adducts were formed at the initial stage of the reactions under kinetic control, but the final products were the trans-(syn)-N,O-acetal adducts that were produced through a retro-aldol process under thermodynamic control. In the whole reaction process, the zinc catalyst played three important roles: i) promotion of the aldol process (C-C bond formation), ii) cyclization process to the N,O-acetal product (C-O bond formation), and iii) retro-aldol process from the anti-aldol adduct to the syn-aldol adduct (C-C bond cleavage and C-C bond formation).

  2. Condensed Matter Cluster Reactions in LENR Power Cells for a Radical New Type of Space Power Source

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoling; Miley, George H.; Hora, Heinz

    2009-03-01

    This paper reviews previous theoretical and experimental study on the possibility of nuclear events in multilayer thin film electrodes (Lipson et al., 2004 and 2005; Miley et al., 2007), including the correlation between excess heat and transmutations (Miley and Shrestha, 2003) and the cluster theory that predicts it. As a result of this added understanding of cluster reactions, a new class of electrodes is under development at the University of Illinois. These electrodes are designed to enhance cluster formation and subsequent reactions. Two approaches are under development. The first employs improved loading-unloading techniques, intending to obtain a higher volumetric density of sites favoring cluster formation. The second is designed to create nanostructures on the electrode where the cluster state is formed by electroless deposition of palladium on nickel micro structures. Power units employing these electrodes should offer unique advantages for space applications. This is a fundamental new nuclear energy source that is environmentally compatible with a minimum of radiation involvement, high specific power, very long lifetime, and scalable from micro power to kilowatts.

  3. Condensed Matter Cluster Reactions in LENR Power Cells for a Radical New Type of Space Power Source

    SciTech Connect

    Yang Xiaoling; Miley, George H.; Hora, Heinz

    2009-03-16

    This paper reviews previous theoretical and experimental study on the possibility of nuclear events in multilayer thin film electrodes (Lipson et al., 2004 and 2005; Miley et al., 2007), including the correlation between excess heat and transmutations (Miley and Shrestha, 2003) and the cluster theory that predicts it. As a result of this added understanding of cluster reactions, a new class of electrodes is under development at the University of Illinois. These electrodes are designed to enhance cluster formation and subsequent reactions. Two approaches are under development. The first employs improved loading-unloading techniques, intending to obtain a higher volumetric density of sites favoring cluster formation. The second is designed to create nanostructures on the electrode where the cluster state is formed by electroless deposition of palladium on nickel micro structures. Power units employing these electrodes should offer unique advantages for space applications. This is a fundamental new nuclear energy source that is environmentally compatible with a minimum of radiation involvement, high specific power, very long lifetime, and scalable from micro power to kilowatts.

  4. Iron Oxide-Supported Copper Oxide Nanoparticles (Nanocat-Fe-CuO): Magnetically Recyclable Catalysts for the Synthesis of Pyrazole Derivatives, 4-Methoxyaniline, and Ullmann-type Condensation Reactions

    EPA Science Inventory

    An efficient and benign protocol is reported for the synthesis of 4-methoxyaniline, medicinally important pyrazole derivatives, and Ullmann-type condensation reaction using magnetically separable and reusable magnetite-supported copper (nanocat-Fe-CuO) nanoparticles under mild co...

  5. Condensed-phase pyrolysis of n-tetradecane at elevated pressures for long duration -- Product distribution and reaction mechanisms

    SciTech Connect

    Song, C.; Lai, W.C.; Schobert, H.H. . Fuel Science Program)

    1994-03-01

    For pyrolysis of n-tetradecane at 450 C under elevated pressures (about 2--9 MPa) for 6--480 min, the major products in the early stage are n-alkanes in the carbon number range of C[sub 1]-C[sub 11] and 1-alkenes in the carbon number range of C[sub 2]-C[sub 14]. Formation of the olefinic product with 13 carbon atoms is very limited, but 1-C[sub 12]H[sub 24] is as abundant as the 1-alkenes in the range of C[sub 2]-C[sub 11]. As compared to the well-known gas-phase pyrolysis, the molar ratios of alkenes to alkanes are much smaller ([le]1), except the ratio for the group with 12 carbon atoms where the 1-C[sub 12]H[sub 24]/n-C[sub 12]H[sub 26] ratio can be as high as 9 in the early stage. This is because 1-C[sub 12]H[sub 24] is produced from [beta]-scission of a secondary 4-C[sub 14]H[sub 29] radical, whereas n-C[sub 12]H[sub 26] is formed from a primary 1-C[sub 14]H[sub 29] radical, whose population is much less than the secondary radical due to both higher activation energy and the competing isomerization reaction. There appeared a preferential formation of 1-C[sub 6]H[sub 12] and 1-C[sub 5]H[sub 10] among the 1-alkenes formed after 12 min. This may be attributed to the 1,5-shift and 1,4-shift isomerization of primary radicals formed during tetradecane pyrolysis. The peak of carbon number distribution shifts toward 2 for paraffinic products and toward 3 for olefinic products, and the ratios of alkenes to alkanes decrease with increasing residence time up to 60 min. The general reaction mechanism is characterized by the one-step decomposition of secondary radicals and the 1,5 and 1,4-shift isomerization of primary radicals to secondary radicals. The substrate alkane molecules are the source for hydrogen abstraction in the early stage, but in the later stages the olefinic products also undergo the H-abstraction reactions, which lead to the formation of cyclic alkenes/alkanes and alkylaromatics.

  6. An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Final report

    SciTech Connect

    Miknis, F.P.; Netzel, D.A.; Wallace, J.C. Jr.; Butcher, C.H.; Mitzel, J.M.; Turner, T.F.

    1995-02-01

    While great strides have been made in developing the technology of coal liquefaction processes in recent years, many unsolved problems still remain before a viable and economical process can be achieved. The technological problems that still exist can be solved through a more fundamental understanding of the chemistry associated with each stage of the coal liquefaction process, starting with any pretreatment steps that may be carried out on the coal itself. Western Research Institute, under the a contract from the US Department of Energy, has conducted a study of different methods of coal drying as pretreatment steps before liquefaction. The results of that study are the subject of this report. Coals that were dried or partially dried thermally and with microwaves had lower liquefaction conversions than coals containing equilibrium moisture contents. However, chemically dried coals had conversions equal to or greater than the premoisturized coals. The conversion behavior is consistent with changes in the physical structure and cross linking reactions because of drying. Thermal and microwave drying appear to cause a collapse in the pore structure, thus preventing donor solvents such as tetralin from contacting reactive sites inside the coals. Chemical dehydration does not appear to collapse the pore structure. From the study of the kinetics of the chemical dehydration of coals, it was possible to quantify the amount of water on the surface, the amount readily accessible in pores, and the amount more strongly bonded in the internal structure of the coals. The results indicate that high-rank coals have proportionally less surface and easily accessible water than the lower rank coals.

  7. CONDENSATION CAN

    DOEpatents

    Booth, E.T. Jr.; Pontius, R.B.; Jacobsohn, B.A.; Slade, C.B.

    1962-03-01

    An apparatus is designed for condensing a vapor to a solid at relatively low back pressures. The apparatus comprises a closed condensing chamber, a vapor inlet tube extending to the central region of the chamber, a co-axial tubular shield surrounding the inlet tube, means for heating the inlet tube at a point outside the condensing chamber, and means for refrigeratirg the said chamber. (AEC)

  8. An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Quarterly progress report, October 1, 1992--December 31, 1992

    SciTech Connect

    Miknis, F.P.

    1993-01-01

    The overall objectives of this work are to conduct research that will provide the basis for an improved liquefaction process, and to facilitate our understanding of those processes that occur when coals are initially dissolved. Changes in coal structure that occur during coal drying and steam pretreatments will be measured in order to determine what effect water has on retrograde/condensation reactions, and to determine the mechanism by which water enhances coal reactivity toward liquefaction. Different methods for coal drying wig be investigated to determine if drying can be accomplished without destroying coal reactivity toward liquefaction, thereby making coal drying a relatively economical and efficient method for coal pretreatment. Coal drying methods will include conventional thermal drying, microwave drying, and chemical drying at low temperature. State-of-the-art solid-state nuclear magnetic resonance (NMR) techniques using combined rotation and multiple pulse spectroscopy (CRAMPS) and cross polarization with magic-angle spinning (CP/MAS) will be employed: (1) to measures changes in coal structure brought about by the different methods of drying and by low temperature oxidation, and (2) to obtain direct measurements of changes in the aromatic hydrogen-to-carbon ratio of the solid/semisolid material formed or remaining during pretreatment and the initial stages of liquefaction.

  9. Amine catalyzed condensation of tetraethylorthosilicate

    NASA Technical Reports Server (NTRS)

    Jones, S.

    2001-01-01

    The catalysis of the condensation of hydrolyzed metal alkoxides by amines has been mentioned in the literature, but there has been no systematic study of their influence on the rate of the condensation reaction of the alkoxide and the microstructure of the resultant gel.

  10. Adsorption and Reaction of Acetaldehyde on Stoichiometric and Defective SrTiO₃(100) Surfaces

    SciTech Connect

    Wang, Li Q.; Ferris, Kim F.; Azad, Samina; Engelhard, Mark H.; Peden, Charles HF.

    2004-02-05

    The adsorption and reaction of acetaldehyde (CH{sub 3}CHO), on stoichiometric (TiO{sub 2}-terminated) and reduced SrTiO{sub 3}(100) surfaces, have been investigated using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Acetaldehyde adsorbs molecularly on the stoichiometric SrTiO{sub 3}(100) surface that contains predominantly Ti{sup 4+} cations. The Ti{sup 4+} sites on the stoichiometric SrTiO{sub 3}(100) surface are not sufficiently active for surface reactions such as aldol condensation, as opposed to the Ti{sup 4+} ions on the TiO{sub 2}(001) surface. However, decomposition and redox reactions of acetaldehyde occur in the presence of surface defects created by Ar{sup +} sputtering. The decomposition products following reactions of acetaldehyde on the defective surface include H{sub 2}, C{sub 2}H{sub 4}, CO, C{sub 4}H{sub 6}, and C{sub 4}H{sub 8}. Reductive coupling, to produce C{sub 2}H{sub 4} and C{sub 4}H{sub 8} is the main reaction pathway for decomposition of acetaldehyde on the sputter reduced SrTiO{sub 3}(100) surface.

  11. Formation of C-C and C-O bonds and oxygen removal in reactions of alkanediols, alkanols, and alkanals on copper catalysts.

    PubMed

    Sad, María E; Neurock, Matthew; Iglesia, Enrique

    2011-12-21

    This study reports evidence for catalytic deoxygenation of alkanols, alkanals, and alkanediols on dispersed Cu clusters with minimal use of external H(2) and with the concurrent formation of new C-C and C-O bonds. These catalysts selectively remove O-atoms from these oxygenates as CO or CO(2) through decarbonylation or decarboxylation routes, respectively, that use C-atoms present within reactants or as H(2)O using H(2) added or formed in situ from CO/H(2)O mixtures via water-gas shift. Cu catalysts fully convert 1,3-propanediol to equilibrated propanol-propanal intermediates that subsequently form larger oxygenates via aldol-type condensation and esterification routes without detectable involvement of the oxide supports. Propanal-propanol-H(2) equilibration is mediated by their chemisorption and interconversion at surfaces via C-H and O-H activation and propoxide intermediates. The kinetic effects of H(2), propanal, and propanol pressures on turnover rates, taken together with measured selectivities and the established chemical events for base-catalyzed condensation and esterification reactions, indicate that both reactions involve kinetically relevant bimolecular steps in which propoxide species, acting as the base, abstract the α-hydrogen in adsorbed propanal (condensation) or attack the electrophilic C-atom at its carbonyl group (esterification). These weakly held basic alkoxides render Cu surfaces able to mediate C-C and C-O formation reactions typically catalyzed by basic sites inherent in the catalyst, instead of provided by coadsorbed organic moieties. Turnover rates for condensation and esterification reactions decrease with increasing Cu dispersion, because low-coordination corner and edge atoms prevalent on small clusters stabilize adsorbed intermediates and increase the activation barriers for the bimolecular kinetically relevant steps required for both reactions. PMID:22023723

  12. Adsorption and Reaction of Acetaldehyde on Stoichiometric and Defective SrTiO{sub 3}(100) Surfaces

    SciTech Connect

    Wang, Li Q.; Ferris, Kim F.; Azad, Samina; Engelhard, Mark H.; Peden, Charles HF.

    2004-02-05

    The adsorption and reaction of acetaldehyde (CH{sub 3}CHO), on stoichiometric (TiO{sub 2}-terminated) and reduced SrTiO{sub 3}(100) surfaces, have been investigated using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Acetaldehyde adsorbs molecularly on the stoichiometric SrTiO{sub 3}(100) surface that contains predominantly Ti{sup 4+} cations. The Ti{sup 4+} sites on the stoichiometric SrTiO{sub 3}(100) surface are not sufficiently active for surface reactions such as aldol condensation, as opposed to the Ti{sup 4+} ions on the TiO{sub 2}(001) surface. However, decomposition and redox reactions of acetaldehyde occur in the presence of surface defects created by Ar{sup +} sputtering. The decomposition products following reactions of acetaldehyde on the defective surface include H{sub 2}, C{sub 2}H{sub 4}, CO, C{sub 4}H{sub 6} and C{sub 4}H{sub 8}. Reductive coupling, to produce C{sub 2}H{sub 4} and C{sub 4}H{sub 8}, is the main reaction pathway for decomposition of acetaldehyde on the sputter reduced SrTiO{sub 3}(100) surface.

  13. Condensation polyimides

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M.

    1989-01-01

    Polyimides belong to a class of polymers known as polyheterocyclics. Unlike most other high temperature polymers, polyimides can be prepared from a variety of inexpensive monomers by several synthetic routes. The glass transition and crystalline melt temperature, thermooxidative stability, toughness, dielectric constant, coefficient of thermal expansion, chemical stability, mechanical performance, etc. of polyimides can be controlled within certain boundaries. This versatility has permitted the development of various forms of polyimides. These include adhesives, composite matrices, coatings, films, moldings, fibers, foams and membranes. Polyimides are synthesized through both condensation (step-polymerization) and addition (chain growth polymerization) routes. The precursor materials used in addition polyimides or imide oligomers are prepared by condensation method. High molecular weight polyimide made via polycondensation or step-growth polymerization is studied. The various synthetic routes to condensation polyimides, structure/property relationships of condensation polyimides and composite properties of condensation polyimides are all studied. The focus is on the synthesis and chemical structure/property relationships of polyimides with particular emphasis on materials for composite application.

  14. Glucose and fructose decomposition in subcritical and supercritical water: Detailed reaction pathway, mechanisms, and kinetics

    SciTech Connect

    Kabyemela, B.M.; Adschiri, T.; Malaluan, R.M.; Arai, K.

    1999-08-01

    The authors are developing a new catalyst-free process of cellulose decomposition in supercritical water. In their initial study on the cellulose decomposition in supercritical water, the main products of cellulose decomposition were found to be oligomers of glucose (cellobiose, cellotriose, etc.) and glucose at short residence times (400 C, 25 MPa, 0.05 s). The kinetics of glucose at these conditions can be useful in understanding the reaction pathways of cellulose. Experiments were performed on the products of glucose decomposition at short residence times to elucidate the reaction pathways and evaluate kinetics of glucose and fructose decomposition in sub- and supercritical water. The conditions were a temperature of 300--400 C and pressure of 25--40 MPa for extremely short residence times between 0.02 and 2 s. The products of glucose decomposition were fructose, a product of isomerization, 1,6-anhydroglucose, a product of dehydration, and erythrose and glyceraldehyde, products of C-C bond cleavage. Fructose underwent reactions similar to glucose except that it did not form 1,6-anhydroglucose and isomerization to glucose is negligible. The mechanism for the products formed from C-C bond cleavage could be explained by reverse aldol condensation and the double-bond rule of the respective enediols formed during the Lobry de Bruyn Alberda van Ekenstein transformation. The differential equations resulting from the proposed pathways were fit to experimental results to obtain the kinetic rate constants.

  15. Epimerization in peptide thioester condensation.

    PubMed

    Teruya, Kenta; Tanaka, Takeyuki; Kawakami, Toru; Akaji, Kenichi; Aimoto, Saburo

    2012-11-01

    Peptide segment couplings are now widely utilized in protein chemical synthesis. One of the key structures for the strategy is the peptide thioester. Peptide thioester condensation, in which a C-terminal peptide thioester is selectively activated by silver ions then condensed with an amino component, is a powerful tool. But the amino acid adjacent to the thioester is at risk of epimerization. During the preparation of peptide thioesters by the Boc solid-phase method, no substantial epimerization of the C-terminal amino acid was detected. Epimerization was, however, observed during a thioester-thiol exchange reaction and segment condensation in DMSO in the presence of a base. In contrast, thioester-thiol exchange reactions in aqueous solutions gave no epimerization. The epimerization during segment condensation was significantly suppressed with a less polar solvent that is applicable to segments in thioester peptide condensation. These results were applied to a longer peptide thioester condensation. The epimer content of the coupling product of 89 residues was reduced from 27% to 6% in a condensation between segments of 45 and 44 residues for the thioester and the amino component, respectively.

  16. Development of detonation reaction engine

    NASA Technical Reports Server (NTRS)

    Lange, O. H.; Stein, R. J.; Tubbs, H. E.

    1968-01-01

    Reaction engine operates on the principle of a controlled condensed detonation. In this engine the gas products that are expelled from the engine to produce thrust are generated by the condensed detonation reaction. The engine is constructed of two basic sections consisting of a detonation wave generator section and a condensed detonation reaction section.

  17. ALDOL REACTION VIA IN SITU OLEFIN MIGRATION IN WATER. (R828129)

    EPA Science Inventory

    Mingwen Wang and Chao-Jun LiCorresponding Author Contact Information

    Department of Chemistry, Tulane University, Ne...

  18. An Exercise on Structure Elucidation Based on a Tricky Aldol Reaction

    ERIC Educational Resources Information Center

    Sierra, Manuel Gonzalez; Pellegrinet, Silvina C.; Colombo, Maria I.; Ruveda, Edmundo A.

    2008-01-01

    An exercise on structure elucidation for advanced undergraduate students is described. To determine the structure of an unknown product, students are required to use spectra together with an organic chemistry mechanism. This exercise exemplifies the procedure commonly used in research, thus helping students develop problem-solving skills. In…

  19. ALDOL- AND MANNICH-TYPE REACTIONS VIA IN SITU OLEFIN MIGRATION IN IONIC LIQUID. (R828129)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  20. Amine-catalyzed direct aldol reactions of hydroxy- and dihydroxyacetone: biomimetic synthesis of carbohydrates.

    PubMed

    Popik, Oskar; Pasternak-Suder, Monika; Leśniak, Katarzyna; Jawiczuk, Magdalena; Górecki, Marcin; Frelek, Jadwiga; Mlynarski, Jacek

    2014-06-20

    This article presents comprehensive studies on the application of primary, secondary, and tertiary amines as efficient organocatalysts for the de novo synthesis of ketoses and deoxyketoses. Mimicking the actions of aldolase enzymes, the synthesis of selected carbohydrates was accomplished in aqueous media by using proline- and serine-based organocatalysts. The presented methodology also provides direct access to unnatural L-carbohydrates from the (S)-glyceraldehyde precursor. Determination of the absolute configuration of all obtained sugars was feasible using a methodology consisting of concerted ECD and VCD spectroscopy.

  1. Polariton condensates

    SciTech Connect

    Snoke, David; Littlewood, Peter

    2010-08-15

    Most students of physics know about the special properties of Bose-Einstein condensates (BECs) as demonstrated in the two best-known examples: superfluid helium-4, first reported in 1938, and condensates of trapped atomic gases, first observed in 1995. (See the article by Wolfgang Ketterle in PHYSICS TODAY, December 1999, page 30.) Many also know that superfluid {sup 3}He and superconducting metals contain BECs of fermion pairs. An underlying principle of all those condensed-matter systems, known as quantum fluids, is that an even number of fermions with half-integer spin can be combined to make a composite boson with integer spin. Such composite bosons, like all bosons, have the property that below some critical temperature--roughly the temperature at which the thermal de Broglie wavelength becomes comparable to the distance between the bosons--the total free energy is minimized by having a macroscopic number of bosons enter a single quantum state and form a macroscopic, coherent matter wave. Remarkably, the effect of interparticle repulsion is to lead to quantum mechanical exchange interactions that make that state robust, since the exchange interactions add coherently.

  2. A DFT analysis of thermal decomposition reactions important to natural products.

    PubMed

    Setzer, William N

    2010-07-01

    The thermal decomposition reactions of several important natural flavor and fragrance chemicals have been investigated using density functional theory (DFT, B3LYP/6-31G*). Retro-aldol reactions of glucose, fructose, hernandulcin, epihernandulcin, [3]-gingerol, and [4]-isogingerol; retro-carbonyl-ene reactions of isopulegol, lavandulol, isolyratol, and indicumenone; and pyrolytic syn elimination reactions of linalyl acetate, alpha-terpinyl acetate, and bornyl acetate, have been carried out. The calculations indicate activation enthalpies of around 30 kcal/mol for the retro-aldol reactions and for retro-carbonyl-ene reactions, comparable to pericyclic reactions such as the Cope rearrangement and electrocyclic reactions, and therefore important reactions at elevated temperatures (e.g., boiling aqueous solutions, gas-chromatograph injection ports). Activation enthalpies for pyrolytic eliminations are around 40 kcal/mol and are unlikely to occur during extraction or GC analysis. PMID:20734926

  3. Secondary organic aerosol formation by self-reactions of methylglyoxal and glyoxal in evaporating droplets.

    PubMed

    De Haan, David O; Corrigan, Ashley L; Tolbert, Margaret A; Jimenez, Jose L; Wood, Stephanie E; Turley, Jacob J

    2009-11-01

    Glyoxal and methylglyoxal are scavenged by clouds, where a fraction of these compounds are oxidized during the lifetime of the droplet. As a cloud droplet evaporates, the remaining glyoxal and methylglyoxal must either form low-volatility compounds such as oligomers and remain in the aerosol phase, or transfer back to the gas phase. A series of experiments on evaporating aqueous aerosol droplets indicates that over the atmospherically relevant concentration range for clouds and fog (4-1000 microM), 33 +/- 11% of glyoxal and 19 +/- 13% of methylglyoxal remains in the aerosol phase while the remainder evaporates. Measurements of aerosol density and time-dependent AMS signal changes are consistent with the formation of oligomers by each compound during the drying process. Unlike glyoxal, which forms acetal oligomers, exact mass AMS data indicates that the majority of methylglyoxal oligomers are formed by aldol condensation reactions, likely catalyzed by pyruvic acid, formed from methylglyoxal disproportionation. Our measurements of evaporation fractions can be used to estimate the global aerosol formation potential of glyoxal and methylglyoxal via self-reactions at 1 and 1.6 Tg C yr(-1), respectively. This is a factor of 4 less than the SOA formed by these compounds if their uptake is assumed to be irreversible. However, these estimates are likely lower limits for their total aerosol formation potential because oxidants and amines will also react with glyoxal and methylglyoxal to form additional low-volatility products.

  4. Rh(III)-catalyzed dehydrogenative alkylation of (hetero)arenes with allylic alcohols, allowing aldol condensation to indenes.

    PubMed

    Shi, Zhuangzhi; Boultadakis-Arapinis, Mélissa; Glorius, Frank

    2013-07-25

    Efficient Rh(III)-catalyzed C-H activation of different classes of (hetero)arenes such as 2-phenylpyridine, indoles, aryl ketones and acetanilide and their dehydrogenative cross-coupling with allylic alcohols are described. Several important skeletons such as β-aryl aldehydes and ketones, 2-acetylindenes, 3,4-dihydro-1H-quinolin-2-one and quinoline could be produced using this protocol. PMID:23765402

  5. Stereocontrolled synthesis of syn-β-Hydroxy-α-amino acids by direct aldolization of pseudoephenamine glycinamide.

    PubMed

    Seiple, Ian B; Mercer, Jaron A M; Sussman, Robin J; Zhang, Ziyang; Myers, Andrew G

    2014-04-25

    β-Hydroxy-α-amino acids figure prominently as chiral building blocks in chemical synthesis and serve as precursors to numerous important medicines. Reported herein is a method for the synthesis of β-hydroxy-α-amino acid derivatives by aldolization of pseudoephenamine glycinamide, which can be prepared from pseudoephenamine in a one-flask protocol. Enolization of (R,R)- or (S,S)-pseudoephenamine glycinamide with lithium hexamethyldisilazide in the presence of LiCl followed by addition of an aldehyde or ketone substrate affords aldol addition products that are stereochemically homologous with L- or D-threonine, respectively. These products, which are typically solids, can be obtained in stereoisomerically pure form in yields of 55-98 %, and are readily transformed into β-hydroxy-α-amino acids by mild hydrolysis or into 2-amino-1,3-diols by reduction with sodium borohydride. This new chemistry greatly facilitates the construction of novel antibiotics of several different classes. PMID:24692320

  6. Stereocontrolled Synthesis of Syn-β-Hydroxy-α-Amino Acids by Direct Aldolization of Pseudoephenamine Glycinamide

    PubMed Central

    Seiple, Ian B.; Mercer, Jaron A. M.; Sussman, Robin J.; Zhang, Ziyang

    2014-01-01

    β-Hydroxy-α-amino acids figure prominently as chiral building blocks in chemical synthesis, serving as precursors to numerous important medicines. We have developed and here report a method for the synthesis of β-hydroxy-α-amino acid derivatives by aldolization of pseudoephenamine glycinamide, which can be prepared from pseudoephenamine in a one-flask protocol. Enolization of (R,R)- or (S,S)-pseudoephenamine glycinamide with lithium hexamethyldisilazide in the presence of lithium chloride followed by addition of an aldehyde or ketone substrate affords aldol addition products that are stereochemically homologous with L- or D-threonine, respectively. These products, which are typically solids, can be obtained in stereoisomerically pure form in yields of 55–98%, and are readily transformed into β-hydroxy-α-amino acids by mild hydrolysis or into 2-amino-1,3-diols by reduction with sodium borohydride. This new chemistry greatly facilitates the construction of novel antibiotics of several different classes. PMID:24692320

  7. Condensed Matter Nuclear Science

    NASA Astrophysics Data System (ADS)

    Biberian, Jean-Paul

    2006-02-01

    1. General. A tribute to gene Mallove - the "Genie" reactor / K. Wallace and R. Stringham. An update of LENR for ICCF-11 (short course, 10/31/04) / E. Storms. New physical effects in metal deuterides / P. L. Hagelstein ... [et al.]. Reproducibility, controllability, and optimization of LENR experiments / D. J. Nagel -- 2. Experiments. Electrochemistry. Evidence of electromagnetic radiation from Ni-H systems / S. Focardi ... [et al.]. Superwave reality / I. Dardik. Excess heat in electrolysis experiments at energetics technologies / I. Dardik ... [et al.]. "Excess heat" during electrolysis in platinum/K[symbol]CO[symbol]/nickel light water system / J. Tian ... [et al.]. Innovative procedure for the, in situ, measurement of the resistive thermal coefficient of H(D)/Pd during electrolysis; cross-comparison of new elements detected in the Th-Hg-Pd-D(H) electrolytic cells / F. Celani ... [et al.]. Emergence of a high-temperature superconductivity in hydrogen cycled Pd compounds as an evidence for superstoihiometric H/D sites / A. Lipson ... [et al.]. Plasma electrolysis. Calorimetry of energy-efficient glow discharge - apparatus design and calibration / T. B. Benson and T. O. Passell. Generation of heat and products during plasma electrolysis / T. Mizuno ... [et al.]. Glow discharge. Excess heat production in Pd/D during periodic pulse discharge current in various conditions / A. B. Karabut. Beam experiments. Accelerator experiments and theoretical models for the electron screening effect in metallic environments / A. Huke, K. Czerski, and P. Heide. Evidence for a target-material dependence of the neutron-proton branching ratio in d+d reactions for deuteron energies below 20keV / A. Huke ... [et al.]. Experiments on condensed matter nuclear events in Kobe University / T. Minari ... [et al.]. Electron screening constraints for the cold fusion / K. Czerski, P. Heide, and A. Huke. Cavitation. Low mass 1.6 MHz sonofusion reactor / R. Stringham. Particle detection. Research

  8. Temperature- and pH-dependent aqueous-phase kinetics of the reactions of glyoxal and methylglyoxal with atmospheric amines and ammonium sulfate

    NASA Astrophysics Data System (ADS)

    Sedehi, Nahzaneen; Takano, Hiromi; Blasic, Vanessa A.; Sullivan, Kristin A.; De Haan, David O.

    2013-10-01

    Reactions of glyoxal (Glx) and methylglyoxal (MG) with primary amines and ammonium salts may produce brown carbon and N-containing oligomers in aqueous aerosol. 1H NMR monitoring of reactant losses and product appearance in bulk aqueous reactions were used to derive rate constants and quantify competing reaction pathways as a function of pH and temperature. Glx + ammonium sulfate (AS) and amine reactions generate products containing C-N bonds, with rates depending directly on pH: rate = (70 ± 60) M-1 s-1fAld [Glx]totfAm [Am]tot, where fAld is the fraction of aldehyde with a dehydrated aldehyde functional group, and fAm is the fraction of amine or ammonia that is deprotonated at a given pH. MG + amine reactions generate mostly aldol condensation products and exhibit less pH dependence: rate = 10[(0.36 ± 0.06) × pH - (3.6 ± 0.3)] M-1 s-1fAld [MG]tot [Am]tot. Aldehyde + AS reactions are less temperature-dependent (Ea = 18 ± 8 kJ mol-1) than corresponding amine reactions (Ea = 50 ± 11 kJ mol-1). Using aerosol concentrations of [OH] = 10-12 M, [amine]tot = [AS] = 0.1 M, fGlx = 0.046 and fMG = 0.09, we estimate that OH radical reactions are normally the major aerosol-phase sink for both dicarbonyl compounds. However, reactions with AS and amines together can account for up to 12 and 45% of daytime aerosol-phase glyoxal and methylglyoxal reactivity, respectively, in marine aerosol at pH 5.5. Reactions with AS and amines become less important in acidic or non-marine aerosol, but may still be significant atmospheric sources of brown carbon, imidazoles, and nitrogen-containing oligomers.

  9. Proposal for New Experimental Tests of the Bose-Einstein Condensation Mechanism for Low-Energy Nuclear Reaction and Transmutation Processes in Deuterium Loaded - and Nano-Scale Cavities

    NASA Astrophysics Data System (ADS)

    Kim, Yeong E.; Koltick, David S.; Reifenberger, Ronald G.; Zubarev, Alexander L.

    2006-02-01

    Most of experimental results of low-energy nuclear reaction (LENR) reported so far cannot be reproduced on demand. There have been persistent experimental results indicating that the LENR and transmutation processes in condensed matters (LENRTPCM) are surface phenomena rather than bulk phenomena. Recently proposed Bose-Einstein condensation (BEC) mechanism may provide a suitable theoretical description of the surface phenomena. New experiments are proposed and described for testing the BEC mechanism for LENR and transmutation processes in micro- and nano-scale traps. (1) We propose the use of micro- or nano-porous conducting materials as a cathode in electrolysis experiments with heavy water with or without Li in order to stabilize the active surface spots and to enhance the effect for the purpose of improving the reproducibility of excess heat generation and nuclear emission. (2) We propose new experimental tests of the BEC mechanism by measuring the pressure and temperature dependence of LENR events using deuterium gas and these deuterated metals with or without Li. If the LENRTPCM are surface phenomena, the proposed use of micro-/nano-scale porous materials is expected to enhance and scale up the LENRTPCM effects by many order of magnitude, and thus may lead to better reproductivity and theoretical understanding of the phenomena.

  10. Continuous detonation reaction engine

    NASA Technical Reports Server (NTRS)

    Lange, O. H.; Stein, R. J.; Tubbs, H. E.

    1968-01-01

    Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity.

  11. Condensation heat transfer

    NASA Astrophysics Data System (ADS)

    Rose, J. W.

    The paper gives a brief description of some of the better understood aspects of condensation heat transfer and includes discussion of the liquid-vapour interface, natural and forced convection laminar film condensation and dropwise condensation.

  12. A new fatty aldol ester from the aerial part of Mimosa invisa (Mimosaceae).

    PubMed

    Nana, Frederic; Sandjo, Louis Pergaud; Keumedjio, Felix; Kuete, Victor; Ngadjui, Bonaventure Tchaleu

    2012-01-01

    A new aldol ester named 17-O-triacontanoylheptadecanal (1) was isolated from the aerial part of Mimosa invisa (Mimosaceae) together with eight known compounds identified as β-sitosterol (2), α-amyrine (3), lupeol (4), 4'-O-methylepinumisoflavone (5), alpinumisoflavone (6), betulinic acid (7), 3-O-β-D-glucopyranoside of sitosterol (8) and epirobinetinidol (9). The structures of compounds were determined on the basis of NMR and mass spectrometry data as well as by comparing the data reported in the literatures. The antimicrobial activities of the crude extract and compounds 1 and 9 were investigated against seven microbial species. The natural products showed moderate activities compared to that of the crude extract.

  13. Clusters: Elucidating the dynamics of ionization events and ensuing reactions in the condensed phase. Final technical report, March 1, 1991--February 28, 1994

    SciTech Connect

    Castleman, A.W. Jr.

    1994-10-01

    Chemical reactions that proceed following either a photophysical or ionizing event, are directly influenced by the mechanisms of energy transfer and dissipation away from the site of absorption. Neighboring solvent or solute molecules can affect this by collisional deactivation (removal of energy), through effects in which dissociating molecules are kept in relatively close proximity for comparatively long periods of time due to the presence of the solvent, and in other ways where the solvent influences the energetics of the reaction coordinate. Research on clusters offers promise of elucidating the molecular details of these processes. The studies have focused on providing critical information on problems in radiation biology through investigations of reactions of molecules which simulate functional groups in biological systems, as they proceed following the absorption of ionizing radiation. The overall objective of the program has been to undertake basic underpinning research that contributes to a quantification of the behavior of radionuclides and pollutants associated with advanced energy activities after these materials emanate from their source and are transferred through the environment to the biota and human receptor. Some of the studies have dealt with the interaction of electromagnetic radiation with matter yielding new data that finds value in assessing photoinduced transformation of pollutants including reactions which take place on aerosol particles, as well as those of species which become transformed into aerosols as a result of their chemical and physical interactions.

  14. Condensation model for the ESBWR passive condensers

    SciTech Connect

    Revankar, S. T.; Zhou, W.; Wolf, B.; Oh, S.

    2012-07-01

    In the General Electric's Economic simplified boiling water reactor (GE-ESBWR) the passive containment cooling system (PCCS) plays a major role in containment pressure control in case of an loss of coolant accident. The PCCS condenser must be able to remove sufficient energy from the reactor containment to prevent containment from exceeding its design pressure following a design basis accident. There are three PCCS condensation modes depending on the containment pressurization due to coolant discharge; complete condensation, cyclic venting and flow through mode. The present work reviews the models and presents model predictive capability along with comparison with existing data from separate effects test. The condensation models in thermal hydraulics code RELAP5 are also assessed to examine its application to various flow modes of condensation. The default model in the code predicts complete condensation well, and basically is Nusselt solution. The UCB model predicts through flow well. None of condensation model in RELAP5 predict complete condensation, cyclic venting, and through flow condensation consistently. New condensation correlations are given that accurately predict all three modes of PCCS condensation. (authors)

  15. PqsBC, a Condensing Enzyme in the Biosynthesis of the Pseudomonas aeruginosa Quinolone Signal: CRYSTAL STRUCTURE, INHIBITION, AND REACTION MECHANISM.

    PubMed

    Drees, Steffen Lorenz; Li, Chan; Prasetya, Fajar; Saleem, Muhammad; Dreveny, Ingrid; Williams, Paul; Hennecke, Ulrich; Emsley, Jonas; Fetzner, Susanne

    2016-03-25

    Pseudomonas aeruginosaproduces a number of alkylquinolone-type secondary metabolites best known for their antimicrobial effects and involvement in cell-cell communication. In the alkylquinolone biosynthetic pathway, the β-ketoacyl-(acyl carrier protein) synthase III (FabH)-like enzyme PqsBC catalyzes the condensation of octanoyl-coenzyme A and 2-aminobenzoylacetate (2-ABA) to form the signal molecule 2-heptyl-4(1H)-quinolone. PqsBC, a potential drug target, is unique for its heterodimeric arrangement and an active site different from that of canonical FabH-like enzymes. Considering the sequence dissimilarity between the subunits, a key question was how the two subunits are organized with respect to the active site. In this study, the PqsBC structure was determined to a 2 Å resolution, revealing that PqsB and PqsC have a pseudo-2-fold symmetry that unexpectedly mimics the FabH homodimer. PqsC has an active site composed of Cys-129 and His-269, and the surrounding active site cleft is hydrophobic in character and approximately twice the volume of related FabH enzymes that may be a requirement to accommodate the aromatic substrate 2-ABA. From physiological and kinetic studies, we identified 2-aminoacetophenone as a pathway-inherent competitive inhibitor of PqsBC, whose fluorescence properties could be used forin vitrobinding studies. In a time-resolved setup, we demonstrated that the catalytic histidine is not involved in acyl-enzyme formation, but contributes to an acylation-dependent increase in affinity for the second substrate 2-ABA. Introduction of Asn into the PqsC active site led to significant activity toward the desamino substrate analog benzoylacetate, suggesting that the substrate 2-ABA itself supplies the asparagine-equivalent amino function that assists in catalysis.

  16. Conversion of acetyl-coenzyme A into 3-hydroxy-3-methylglutaryl-coenzyme A in radish seedlings. Evidence of a single monomeric protein catalyzing a FeII/quinone-stimulated double condensation reaction.

    PubMed

    Weber, T; Bach, T J

    1994-02-10

    We solubilized from radish membranes and purified to apparent homogeneity a monomeric protein (55.5 kDa) capable of catalyzing the two-step conversion of acetyl-CoA into 3-hydroxy-3-methylglutaryl(HMG)-CoA. Unlike the situation described for other eukaryotes (yeast, animals), both enzyme activities needed for HMG-CoA synthesis (acetoacetyl-CoA thiolase, AACT and HMG-CoA synthase, HMGS) appear to be localized on a single polypeptide. Thus, the enzyme system is further referred to as AACT/HMGS. The reaction as catalyzed by purified AACT/HMGS is strongly stimulated in vitro in presence of FeII-chelates (namely EDTA) and of quinone cofactors with pyrroloquinoline quinone (PQQ) being by far the most effective one studied so far. Whereas the FeII stimulation is apparently due to a Vmax effect, PQQ increases the affinity of the enzyme system towards acetyl-CoA (1.9 microM vs. 5.9 microM, at 50 microM FeII, 100 microM EDTA, 20 microM PQQ). Stimulation by naphthoquinone (NQ) can be overcome in the presence of halogenated NQ-derivatives, while activation by PQQ remains unaffected, possibly indicating a much more specific-binding of the latter cofactor. Gel filtration experiments of enzyme after preincubation in presence of PQQ indicate that there is no covalent-binding of the quinone cofactor to the enzyme. As is also shown with partially purified enzyme from maize membranes, phenylhydrazine, known to react with PQQ as the prosthetic group of quinoproteins (see van der Meer et al. (1987) FEBS Lett. 221, 299-304), efficiently inhibits the reaction. The data lead us to suggest a reaction mechanism that involves radical formation by the redox couple FeII/PQQ, thereby possibly facilitating the energetically unfavorable Claisen condensation as catalyzed during the first partial (AACT) reaction.

  17. Theory and Modeling of Asymmetric Catalytic Reactions.

    PubMed

    Lam, Yu-Hong; Grayson, Matthew N; Holland, Mareike C; Simon, Adam; Houk, K N

    2016-04-19

    Modern density functional theory and powerful contemporary computers have made it possible to explore complex reactions of value in organic synthesis. We describe recent explorations of mechanisms and origins of stereoselectivities with density functional theory calculations. The specific functionals and basis sets that are routinely used in computational studies of stereoselectivities of organic and organometallic reactions in our group are described, followed by our recent studies that uncovered the origins of stereocontrol in reactions catalyzed by (1) vicinal diamines, including cinchona alkaloid-derived primary amines, (2) vicinal amidophosphines, and (3) organo-transition-metal complexes. Two common cyclic models account for the stereoselectivity of aldol reactions of metal enolates (Zimmerman-Traxler) or those catalyzed by the organocatalyst proline (Houk-List). Three other models were derived from computational studies described in this Account. Cinchona alkaloid-derived primary amines and other vicinal diamines are venerable asymmetric organocatalysts. For α-fluorinations and a variety of aldol reactions, vicinal diamines form enamines at one terminal amine and activate electrophilically with NH(+) or NF(+) at the other. We found that the stereocontrolling transition states are cyclic and that their conformational preferences are responsible for the observed stereoselectivity. In fluorinations, the chair seven-membered cyclic transition states is highly favored, just as the Zimmerman-Traxler chair six-membered aldol transition state controls stereoselectivity. In aldol reactions with vicinal diamine catalysts, the crown transition states are favored, both in the prototype and in an experimental example, shown in the graphic. We found that low-energy conformations of cyclic transition states occur and control stereoselectivities in these reactions. Another class of bifunctional organocatalysts, the vicinal amidophosphines, catalyzes the (3 + 2) annulation

  18. Multiple Condensation Reactions Involving Pt(II) /Pd(II) -OH2 , Pt-NH3 , and Cytosine-NH2 Groups: New Twists in Cisplatin-Nucleobase Chemistry.

    PubMed

    Yin-Bandur, Lu; Sanz Miguel, Pablo J; Rodríguez-Santiago, Luis; Sodupe, Mariona; Berghaus, Melanie; Lippert, Bernhard

    2016-09-12

    The coordination chemistry of the antitumor agent cisplatin and related complexes with DNA and its constituents, that is, the nucleobases, appears to be dominated by 1:1 and 1:2 adducts of the types cis-[Pta2 (nucleobase)X] and cis-[Pta2 (nucleobase)2 ] (a=NH3 or amine; a2 =diamine or diimine; X=Cl, OH or OH2 ). Here, we have studied the interactions of the putative 1:1 adducts cis-[Pta2 (1-MeC-N3)(OH2 )](2+) (with a=NH3 , a2 =2,2'-bpy (2,2'-bipyridine), 1-MeC=model nucleobase 1-methylcytosine) with additional cis-[Pt(NH3 )2 (OH2 )2 ](2+) or its kinetically superior analogues [Pd(en)(OH2 )2 ](2+) (en=ethylenediamine) and [Pd(2,2'-bpy)(OH2 )2 ](2+) . Depending upon the conditions applied different compounds of different nuclearity are formed. Without exception they represent condensation products of the components, containing μ-1-MeC-H , μ-OH(-) , as well as μ-NH2 (-) bridges. In the presence of Ag(+) ions, the isolated products in several cases display additionally Pt→Ag dative bonds. On the basis of the cytosine-containing structures established by X-ray crystallography, it is proposed that any of the feasible initial 1:1 nucleobase adducts of cisplatin could form dinuclear Pt complexes upon reaction with additional hydrolyzed cisplatin, thereby generating nucleobase adducts other than the presently established ones. Two findings appear to be of particular significance: First, hydrolyzed cisplatin can have a moderately accelerating effect on the formation of a secondary nucleobase product. Second, NH3 ligands of the cisplatin moiety can be converted into bridging amido ligands following condensation with the diaqua species of cisplatin.

  19. Radical addition-initiated domino reactions of conjugated oxime ethers.

    PubMed

    Ueda, Masafumi

    2014-01-01

    The application of conjugated oxime ethers to the synthesis of complex chemical scaffolds using domino radical reactions has been described in detail. The triethylborane-mediated hydroxysulfenylation reaction allows for the regioselective construction of a carbon-sulfur bond and a carbon-oxygen bond in a single operation for the formation of β-hydroxy sulfides. This reaction proceeds via a radical pathway involving regioselective thiyl addition and the subsequent trapping of the resulting α-imino radical with O₂, where the imino group enhances the stability of the intermediate radical. Hydroxyalkylation reactions that occur via a carbon radical addition reaction followed by the hydroxylation of the resulting N-borylenamine with O₂ have also been developed. We investigated sequential radical addition aldol-type reactions in detail to explore the novel domino reactions that occur via the generation of N-borylenamine. The radical reaction of a conjugated oxime ether with triethylborane in the presence of an aldehyde affords γ-butyrolactone via sequential processes including ethyl radical addition, the generation of N-borylenamine, an aldol-type reaction with an aldehyde, and a lactonization reaction. A novel domino reaction has also been developed involving the [3,3]-sigmatropic rearrangement of N-boryl-N-phenoxyenamine. The triethylborane-mediated domino reactions of O-phenyl-conjugated oxime ethers afforded the corresponding benzofuro[2,3-b]pyrrol-2-ones via a radical addition/[3,3]-sigmatropic rearrangement/cyclization/lactamization cascade.

  20. (1)H NMR: A Novel Approach To Determining the Thermodynamic Properties of Acetaldehyde Condensation Reactions with Glycerol, (+)-Catechin, and Glutathione in Model Wine.

    PubMed

    Peterson, Ana L; Waterhouse, Andrew L

    2016-09-14

    As wine oxidizes, ethanol is converted to acetaldehyde, but its accumulation is not predictable, due to poorly characterized reactions with alcohols, SO2, thiols, flavanols, and others. Measurement of these components has been thwarted by equilibria into the other forms during sample preparation. NMR spectra can be taken on intact samples and is thus ideal for this situation. Equilibria of acetaldehyde with glycerol, (+)-catechin, and glutathione were studied separately in model wine solutions at pH 3-4 by (1)H NMR and 2D ((1)H-(1)H) COSY spectra. Glycerol acetals had equilibrium constants between 1.14 ± 0.056 and 2.53 ± 0.043 M(-1), whereas ethylidene-bridged (+)-catechin dimers and glutathione thiohemiacetals had more favorable equilibria: from (3.92 ± 0.13) × 10(3) to (6.13 ± 0.32) × 10(3) M(-2) and from 10.18 ± 0.22 to 11.17 ± 0.47 M(-1), respectively. These data can be used to create accurate measures of acetaldehyde in its various forms and, consequently, offer insight into wine oxidation. PMID:27580067

  1. An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Quarterly progress report, January 1, 1994--March 31, 1994

    SciTech Connect

    Miknis, F.P.; Netzel, D.A.

    1994-04-01

    The results of coal swelling measurements using 1,4-dioxane as the swelling reagent for premoisturized coals (raw) and coal dried thermally, chemically, and with microwave radiation are presented. An increase in the swelling ratio relative to raw coal indicates a decrease in the amount of cross-linking in the coal. Conversely, a decrease in the ratio indicates an increase in cross-linking. The extent of cross-linking (as measured by 1,4-dioxane) for Texas, Black Thunder, and Eagle Butte Coals are about the same. Illinois {number_sign}6 coal appears to have less cross-linking relative to the other three coals. These results are expected on the basis of coal rank. The increase in cross linking is most pronounced for coals dried thermally and with microwave radiation. A decrease in the swelling ratios for all four coals suggests that cross-linking had occurred possibly due to partial devolatilization process. However, low temperature, chemical dehydration of the coals causes only a small or no change in the internal structure for Texas and Illinois {number_sign}6 coals whereas a significant decrease in the cross-linking structure for the Black Thunder and Eagle Butte coals is observed. It is possible that the solvent (CH{sub 3}OH) and products resulting from the chemical dehydrating (acetone and methanol) occupy the surface sites that water had before the reaction and thus preventing cross-linking to occur. These reagents can also promote swelling of coals and may account for some of the decrease in the cross-linking of the coal structure observed for the chemically dried coals.

  2. Condensates in Jovian Atmospheres

    NASA Technical Reports Server (NTRS)

    West, R.

    1999-01-01

    Thermochemical equilibrium theory which starts with temperature/pressure profiles, compositional information and thermodynamic data for condensable species in the jovian planet atmospheres predicts layers of condensate clouds in the upper troposphere.

  3. Sub-Equimolar Hydrolysis and Condensation of Organophosphates

    DOE PAGESBeta

    Alam, Todd M.; Kinnan, Mark K.; Wilson, Brendan W.; Wheeler, David R.

    2016-07-16

    We characterized the in-situ hydrolysis and subsequent condensation reaction of the chemical agent simulant diethyl chlorophosphate (DECP) by high-resolution 31P NMR spectroscopy following the addition of water in sub-equimolar concentrations. Moreover, the identification and quantification of the multiple pyrophosphate and larger polyphosphate chemical species formed through a series of self-condensation reactions are reported. Finally, the DECP hydrolysis kinetics and distribution of breakdown species was strongly influenced by the water concentration and reaction temperature.

  4. Condensed phase preparation of 2,3-pentanedione

    DOEpatents

    Miller, D.J.; Perry, S.M.; Fanson, P.T.; Jackson, J.E.

    1998-11-03

    A condensed phase process for the preparation of purified 2,3-pentanedione from lactic acid and an alkali metal lactate is described. The process uses elevated temperatures between about 200 to 360 C for heating a reaction mixture of lactic acid and an alkali metal lactate to produce the 2,3-pentanedione in a reaction vessel. The 2,3-pentanedione produced is vaporized from the reaction vessel and condensed with water. 5 figs.

  5. Condensed phase preparation of 2,3-pentanedione

    DOEpatents

    Miller, Dennis J.; Perry, Scott M.; Fanson, Paul T.; Jackson, James E.

    1998-01-01

    A condensed phase process for the preparation of purified 2,3-pentanedione from lactic acid and an alkali metal lactate is described. The process uses elevated temperatures between about 200.degree. to 360.degree. C. for heating a reaction mixture of lactic acid and an alkali metal lactate to produce the 2,3-pentanedione in a reaction vessel. The 2,3-pentanedione produced is vaporized from the reaction vessel and condensed with water.

  6. Divergent Synthesis of Multisubstituted Tetrahydrofurans and Pyrrolidines via Intramolecular Aldol-type Trapping of Onium Ylide Intermediates.

    PubMed

    Jing, Changcheng; Xing, Dong; Gao, Lixin; Li, Jia; Hu, Wenhao

    2015-12-21

    This paper reports a divergent strategy for the synthesis of multisubstituted tetrahydrofurans and pyrrolidines, starting from easily accessible β-hydroxyketones or β-aminoketones to react with diazo compounds. Under Rh(II) catalysis, this transformation is proposed to proceed through a metal-carbene-induced oxonium ylide or ammonium ylide formation followed by an intramolecular aldol-type trapping of these active intermediates. A series of highly substituted tetrahydrofurans and pyrrolidines are synthesized in high yields with good to excellent diastereoselectivities. Preliminary biological evaluations revealed that both types of heterocycles show good PTP1B inhibitory activities. PMID:26592374

  7. Condensed Matter Nuclear Science

    NASA Astrophysics Data System (ADS)

    Biberian, Jean-Paul

    2006-02-01

    1. General. A tribute to gene Mallove - the "Genie" reactor / K. Wallace and R. Stringham. An update of LENR for ICCF-11 (short course, 10/31/04) / E. Storms. New physical effects in metal deuterides / P. L. Hagelstein ... [et al.]. Reproducibility, controllability, and optimization of LENR experiments / D. J. Nagel -- 2. Experiments. Electrochemistry. Evidence of electromagnetic radiation from Ni-H systems / S. Focardi ... [et al.]. Superwave reality / I. Dardik. Excess heat in electrolysis experiments at energetics technologies / I. Dardik ... [et al.]. "Excess heat" during electrolysis in platinum/K[symbol]CO[symbol]/nickel light water system / J. Tian ... [et al.]. Innovative procedure for the, in situ, measurement of the resistive thermal coefficient of H(D)/Pd during electrolysis; cross-comparison of new elements detected in the Th-Hg-Pd-D(H) electrolytic cells / F. Celani ... [et al.]. Emergence of a high-temperature superconductivity in hydrogen cycled Pd compounds as an evidence for superstoihiometric H/D sites / A. Lipson ... [et al.]. Plasma electrolysis. Calorimetry of energy-efficient glow discharge - apparatus design and calibration / T. B. Benson and T. O. Passell. Generation of heat and products during plasma electrolysis / T. Mizuno ... [et al.]. Glow discharge. Excess heat production in Pd/D during periodic pulse discharge current in various conditions / A. B. Karabut. Beam experiments. Accelerator experiments and theoretical models for the electron screening effect in metallic environments / A. Huke, K. Czerski, and P. Heide. Evidence for a target-material dependence of the neutron-proton branching ratio in d+d reactions for deuteron energies below 20keV / A. Huke ... [et al.]. Experiments on condensed matter nuclear events in Kobe University / T. Minari ... [et al.]. Electron screening constraints for the cold fusion / K. Czerski, P. Heide, and A. Huke. Cavitation. Low mass 1.6 MHz sonofusion reactor / R. Stringham. Particle detection. Research

  8. Proceedings: Condenser technology conference

    SciTech Connect

    Tsou, J.L. ); Mussalli, Y.G. )

    1991-08-01

    Seam surface condenser and associated systems performance strongly affects availability and heat rate in nuclear and fossil power plants. Thirty-six papers presented at a 1990 conference discuss research results, industry experience, and case histories of condenser problems and solutions. This report contains papers on life extension, performance improvement, corrosion and failure analysis, fouling prevention, and recommendation for future R D. The information represents recent work on condenser problems and solutions to improve the procurement, operation, and maintenance functions of power plant personnel. Several key points follow: A nuclear and a fossil power plant report show that replacing titanium tube bundles improves condenser availability and performance. One paper reports 10 years of experience with enhanced heat transfer tubes in utility condensers. The newly developed enhanced condenser tubes could further improve condensing heat transfer. A new resistance summation method improves the accuracy of condenser performance prediction, especially for stainless steel and titanium tubed condensers. Several papers describe improved condenser fouling monitoring techniques, including a review of zebra mussel issues.

  9. Cooling and condensing of sulfur and water from claus process gas

    SciTech Connect

    Palm, J. W.; Kunkel, L. V.

    1985-07-02

    The Claus process gas is cooled in a condenser to condense most of the sulfur vapor in solid form. The gas leaving the condenser is then further cooled to condense water without producing substantially any sulfur in an undesirable form. The resulting gas of reduced water content is useful in Claus reaction, particularly the low temperature Claus reaction in which the product sulfur is adsorbed on the catalyst.

  10. Condensed Matter Nuclear Science

    NASA Astrophysics Data System (ADS)

    Takahashi, Akito; Ota, Ken-Ichiro; Iwamura, Yashuhiro

    Preface -- 1. General. Progress in condensed matter nuclear science / A. Takahashi. Summary of ICCF-12 / X. Z. Li. Overview of light water/hydrogen-based low-energy nuclear reactions / G. H. Miley and P. J. Shrestha -- 2. Excess heat and He detection. Development of "DS-reactor" as the practical reactor of "cold fusion" based on the "DS-cell" with "DS-cathode" / Y. Arata and Y.-C. Zhang. Progress in excess of power experiments with electrochemical loading of deuterium in palladium / V. Violante ... [et al.]. Anomalous energy generation during conventional electrolysis / T. Mizuno and Y. Toriyabe. "Excess heat" induced by deuterium flux in palladium film / B. Liu ... [et al.]. Abnormal excess heat observed during Mizuno-type experiments / J.-F. Fauvarque, P. P. Clauzon and G. J.-M. Lallevé. Seebeck envelope calorimetry with a Pd|D[symbol]O + H[symbol]SO[symbol] electrolytic cell / W.-S. Zhang, J. Dash and Q. Wang. Observation and investigation of nuclear fusion and self-induced electric discharges in liquids / A. I. Koldamasov ... [et al.]. Description of a sensitive seebeck calorimeter used for cold fusion studies / E. Storms. Some recent results at ENEA / M. Apicella ... [et al.]. Heat measurement during plasma electrolysis / K. Iizumi ... [et al.]. Effect of an additive on thermal output during electrolysis of heavy water with a palladium cathode / Q. Wang and J. Dash. Thermal analysis of calorimetric systems / L. D'Aulerio ... [et al.]. Surface plasmons and low-energy nuclear reactions triggering / E. Castagna ... [et al.]. Production method for violent TCB jet plasma from cavity / F. Amini. New results and an ongoing excess heat controversy / L. Kowalski ... [et al.] -- 3. Transmutation. Observation of surface distribution of products by X-ray fluorescence spectrometry during D[symbol] gas permeation through Pd Complexes / Y. Iwamura ... [et al.]. Discharge experiment using Pd/CaO/Pd multi-layered cathode / S. Narita ... [et al.]. Producing transmutation

  11. A NOVEL CHIRAL GALLIUM LEWIS ACID CATALYST WITH SEMI-CROWN LIGAND IN AQUEOUS ASYMMETRIC MUKAIYAMA ALDOL REACTIONS. (R828129)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  12. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN WATER AND PROTIC SOLVENT. (R828129)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  13. Measure Guideline: Evaporative Condensers

    SciTech Connect

    German, A; Dakin, B.; Hoeschele, M.

    2012-03-01

    This measure guideline on evaporative condensers provides information on properly designing, installing, and maintaining evaporative condenser systems as well as understanding the benefits, costs, and tradeoffs. This is a prescriptive approach that outlines selection criteria, design and installation procedures, and operation and maintenance best practices.

  14. Geothermal steam condensate reinjection

    NASA Technical Reports Server (NTRS)

    Chasteen, A. J.

    1974-01-01

    Geothermal electric generating plants which use condensing turbines and generate and excess of condensed steam which must be disposed of are discussed. At the Geysers, California, the largest geothermal development in the world, this steam condensate has been reinjected into the steam reservoir since 1968. A total of 3,150,000,000 gallons of steam condensate has been reinjected since that time with no noticeable effect on the adjacent producing wells. Currently, 3,700,000 gallons/day from 412 MW of installed capacity are being injected into 5 wells. Reinjection has also proven to be a satisfactory method of disposing of geothermal condensate a Imperial Valley, California, and at the Valles Caldera, New Mexico.

  15. Freeze-Tolerant Condensers

    NASA Technical Reports Server (NTRS)

    Crowley, Christopher J.; Elkouhk, Nabil

    2004-01-01

    Two condensers designed for use in dissipating heat carried by working fluids feature two-phase, self-adjusting configurations such that their working lengths automatically vary to suit their input power levels and/or heat-sink temperatures. A key advantage of these condensers is that they can function even if the temperatures of their heat sinks fall below the freezing temperatures of their working fluids and the fluids freeze. The condensers can even be restarted from the frozen condition. The top part of the figure depicts the layout of the first condenser. A two-phase (liquid and vapor) condenser/vapor tube is thermally connected to a heat sink typically, a radiatively or convectively cooled metal panel. A single-phase (liquid) condensate-return tube (return artery) is also thermally connected to the heat sink. At intervals along their lengths, the condenser/vapor tube and the return artery are interconnected through porous plugs. This condenser configuration affords tolerance of freezing, variable effective thermal conductance (such that the return temperature remains nearly constant, independently of the ultimate sink temperature), and overall pressure drop smaller than it would be without the porous interconnections. An additional benefit of this configuration is that the condenser can be made to recover from the completely frozen condition either without using heaters, or else with the help of heaters much smaller than would otherwise be needed. The second condenser affords the same advantages and is based on a similar principle, but it has a different configuration that affords improved flow of working fluid, simplified construction, reduced weight, and faster recovery from a frozen condition.

  16. Sedimentary condensation and authigenesis

    NASA Astrophysics Data System (ADS)

    Föllmi, Karl

    2016-04-01

    Most marine authigenic minerals form in sediments, which are subjected to condensation. Condensation processes lead to the formation of well individualized, extremely thin (< 1m) beds, which were accumulated during extremely long time periods (> 100ky), and which experienced authigenesis and the precipitation of glaucony, verdine, phosphate, iron and manganese oxyhydroxides, iron sulfide, carbonate and/or silica. They usually show complex internal stratigraphies, which result from an interplay of sediment accumulation, halts in sedimentation, sediment winnowing, erosion, reworking and bypass. They may include amalgamated faunas of different origin and age. Hardgrounds may be part of condensed beds and may embody strongly condensed beds by themselves. Sedimentary condensation is the result of a hydrodynamically active depositional regime, in which sediment accumulation, winnowing, erosion, reworking and bypass are processes, which alternate as a function of changes in the location and intensity of currents, and/or as the result of episodic high-energy events engendered by storms and gravity flow. Sedimentary condensation has been and still is a widespread phenomenon in past and present-day oceans. The present-day distribution of glaucony and verdine-rich sediments on shelves and upper slopes, phosphate-rich sediments and phosphorite on outer shelves and upper slopes, ferromanganese crusts on slopes, seamounts and submarine plateaus, and ferromanganese nodules on abyssal seafloors is a good indication of the importance of condensation processes today. In the past, we may add the occurrence of oolitic ironstone, carbonate hardgrounds, and eventually also silica layers in banded iron formations as indicators of the importance of condensation processes. Besides their economic value, condensed sediments are useful both as a carrier of geochemical proxies of paleoceanographic and paleoenvironmental change, as well as the product of episodes of paleoceanographic and

  17. Electrolyte vapor condenser

    DOEpatents

    Sederquist, Richard A.; Szydlowski, Donald F.; Sawyer, Richard D.

    1983-01-01

    A system is disclosed for removing electrolyte from a fuel cell gas stream. The gas stream containing electrolyte vapor is supercooled utilizing conventional heat exchangers and the thus supercooled gas stream is passed over high surface area passive condensers. The condensed electrolyte is then drained from the condenser and the remainder of the gas stream passed on. The system is particularly useful for electrolytes such as phosphoric acid and molten carbonate, but can be used for other electrolyte cells and simple vapor separation as well.

  18. Electrolyte vapor condenser

    DOEpatents

    Sederquist, R.A.; Szydlowski, D.F.; Sawyer, R.D.

    1983-02-08

    A system is disclosed for removing electrolyte from a fuel cell gas stream. The gas stream containing electrolyte vapor is supercooled utilizing conventional heat exchangers and the thus supercooled gas stream is passed over high surface area passive condensers. The condensed electrolyte is then drained from the condenser and the remainder of the gas stream passed on. The system is particularly useful for electrolytes such as phosphoric acid and molten carbonate, but can be used for other electrolyte cells and simple vapor separation as well. 3 figs.

  19. High Resolution Reaction Intermediates of rabbit Muscle Fructose-1,6-bisphosphate Aldolase: Substrate Cleavage and Induced Fit

    SciTech Connect

    St-Jean,M.; Lafrance-Vanasse, J.; Liotard, B.; Sygusch, J.

    2005-01-01

    Crystal structures were determined to 1.8-Angstrom resolution of the glycolytic enzyme fructose-1, 6-bis(phosphate) aldolase trapped in complex with its substrate and a competitive inhibitor, mannitol-1, 6-bis(phosphate). The enzyme substrate complex corresponded to the postulated Schiff base intermediate and has reaction geometry consistent with incipient C3-C4 bond cleavage catalyzed by Glu-187, which is adjacent to the Schiff base forming Lys-229. Atom arrangement about the cleaved bond in the reaction intermediate mimics a pericyclic transition state occurring in non-enzymatic aldol condensations. Lys-146 hydrogen bonds the substrate C4 hydroxyl and assists substrate cleavage by stabilizing the developing negative charge on the C4 hydroxyl during proton abstraction. Mannitol-1, 6-bis(phosphate) forms a non-covalent complex in the active site whose binding geometry mimics the covalent carbinolamine precursor. Glu-187 hydrogen bonds the C2 hydroxyl of the inhibitor in the enzyme complex substantiating a proton transfer role by Glu-187 in catalyzing the conversion of the carbinolamine intermediate to Schiff base. Modeling of the acyclic substrate configuration into the active site shows Glu-187, in acid form, hydrogen bonding both substrate C2 carbonyl and C4 hydroxyl, thereby aligning the substrate ketose for nucleophilic attack by Lys-229. The multi-functional role by Glu-187 epitomizes a canonical mechanistic feature conserved in Schiff base forming aldolases catalyzing carbohydrate metabolism. Trapping of tagatose-1, 6-bis(phosphate), a diastereoisomer of fructose-1, 6-bis(phosphate), displayed stereospecific discrimination and reduced ketohexose binding specificity. Each ligand induces homologous conformational changes in two adjacent a-helical regions that promote phosphate binding in the active site.

  20. Condensed Matter Nuclear Science

    NASA Astrophysics Data System (ADS)

    Takahashi, Akito; Ota, Ken-Ichiro; Iwamura, Yashuhiro

    Preface -- 1. General. Progress in condensed matter nuclear science / A. Takahashi. Summary of ICCF-12 / X. Z. Li. Overview of light water/hydrogen-based low-energy nuclear reactions / G. H. Miley and P. J. Shrestha -- 2. Excess heat and He detection. Development of "DS-reactor" as the practical reactor of "cold fusion" based on the "DS-cell" with "DS-cathode" / Y. Arata and Y.-C. Zhang. Progress in excess of power experiments with electrochemical loading of deuterium in palladium / V. Violante ... [et al.]. Anomalous energy generation during conventional electrolysis / T. Mizuno and Y. Toriyabe. "Excess heat" induced by deuterium flux in palladium film / B. Liu ... [et al.]. Abnormal excess heat observed during Mizuno-type experiments / J.-F. Fauvarque, P. P. Clauzon and G. J.-M. Lallevé. Seebeck envelope calorimetry with a Pd|D[symbol]O + H[symbol]SO[symbol] electrolytic cell / W.-S. Zhang, J. Dash and Q. Wang. Observation and investigation of nuclear fusion and self-induced electric discharges in liquids / A. I. Koldamasov ... [et al.]. Description of a sensitive seebeck calorimeter used for cold fusion studies / E. Storms. Some recent results at ENEA / M. Apicella ... [et al.]. Heat measurement during plasma electrolysis / K. Iizumi ... [et al.]. Effect of an additive on thermal output during electrolysis of heavy water with a palladium cathode / Q. Wang and J. Dash. Thermal analysis of calorimetric systems / L. D'Aulerio ... [et al.]. Surface plasmons and low-energy nuclear reactions triggering / E. Castagna ... [et al.]. Production method for violent TCB jet plasma from cavity / F. Amini. New results and an ongoing excess heat controversy / L. Kowalski ... [et al.] -- 3. Transmutation. Observation of surface distribution of products by X-ray fluorescence spectrometry during D[symbol] gas permeation through Pd Complexes / Y. Iwamura ... [et al.]. Discharge experiment using Pd/CaO/Pd multi-layered cathode / S. Narita ... [et al.]. Producing transmutation

  1. Ghost condensate busting

    SciTech Connect

    Bilic, Neven; Tupper, Gary B; Viollier, Raoul D E-mail: gary.tupper@uct.ac.za

    2008-09-15

    Applying the Thomas-Fermi approximation to renormalizable field theories, we construct ghost condensation models that are free of the instabilities associated with violations of the null-energy condition.

  2. THE COLOR GLASS CONDENSATE.

    SciTech Connect

    MCLERRAN,L.

    2001-08-26

    The Color Glass Condensate is a state of high density gluonic matter which controls the high energy limit of hadronic interactions. Its properties are important for the initial conditions for matter produced at RHIC.

  3. Measure Guideline: Evaporative Condensers

    SciTech Connect

    German, A.; Dakin, B.; Hoeschele, M.

    2012-03-01

    The purpose of this measure guideline on evaporative condensers is to provide information on a cost-effective solution for energy and demand savings in homes with cooling loads. This is a prescriptive approach that outlines selection criteria, design and installation procedures, and operation and maintenance best practices. This document has been prepared to provide a process for properly designing, installing, and maintaining evaporative condenser systems as well as understanding the benefits, costs, and tradeoffs.

  4. Condensate dark matter stars

    SciTech Connect

    Li, X.Y.; Harko, T.; Cheng, K.S. E-mail: harko@hkucc.hku.hk

    2012-06-01

    We investigate the structure and stability properties of compact astrophysical objects that may be formed from the Bose-Einstein condensation of dark matter. Once the critical temperature of a boson gas is less than the critical temperature, a Bose-Einstein Condensation process can always take place during the cosmic history of the universe. Therefore we model the dark matter inside the star as a Bose-Einstein condensate. In the condensate dark matter star model, the dark matter equation of state can be described by a polytropic equation of state, with polytropic index equal to one. We derive the basic general relativistic equations describing the equilibrium structure of the condensate dark matter star with spherically symmetric static geometry. The structure equations of the condensate dark matter stars are studied numerically. The critical mass and radius of the dark matter star are given by M{sub crit} ≈ 2(l{sub a}/1fm){sup 1/2}(m{sub χ}/1 GeV){sup −3/2}M{sub s}un and R{sub crit} ≈ 1.1 × 10{sup 6}(l{sub a}/1 fm){sup 1/2}(m{sub χ}/1 GeV){sup −3/2} cm respectively, where l{sub a} and m{sub χ} are the scattering length and the mass of dark matter particle, respectively.

  5. The Evans Aldol-Prins cyclization: a general and stereoselective method for the synthesis of 2,3,4,5,6-pentasubstituted tetrahydropyrans.

    PubMed

    Álvarez-Méndez, Sergio J; García, Celina; Martín, Víctor S

    2016-02-25

    A general and stereoselective method to synthesize 2,3,4,5,6-pentasubstituted tetrahydropyrans in three steps starting from three different aldehydes is described. Key substrates β,γ-unsaturated N-acyloxazolidin-2-ones were subjected to an "Evans Aldol-Prins" protocol to generate five σ-bonds and five stereocenters in only a one-pot process with yields up to 60% and excellent stereoselectivities.

  6. Chemical remediation of beech condensates.

    PubMed

    Irmouli, Mohammed; Haluk, Jean Pierre

    2005-01-01

    In the present work, beech wood condensates are separated from the aqueous phase. Experimental results reveal an electrostatic interaction between the oppositely charged wood extracts after oxidation and Ca(OH)(2). The increase in aqueous phase pH resulted in enhanced removal of wood extracts from water. The polarographic assays were carried out at 25 degrees C using a Gilson oxygraph equipped with a Clark electrode in order to determine the oxygen uptake during the oxidation reaction. The effect of pH is explained based on oxygen uptake. The organic compounds found in the aqueous effluent are responsible for the brown color. The objective of this study is to find the optimum pH to eliminate the wood extracts from the liquid effluents. PMID:15567404

  7. Transient nucleation in condensed systems

    NASA Technical Reports Server (NTRS)

    Kelton, K. F.; Greer, A. L.; Thompson, C. V.

    1983-01-01

    Using classical nucleation theory we consider transient nucleation occurring in a one-component, condensed system under isothermal conditions. We obtain an exact closed-form expression for the time dependent cluster populations. In addition, a more versatile approach is developed: a numerical simulation technique which models directly the reactions by which clusters are produced. This simulation demonstrates the evolution of cluster populations and nucleation rate in the transient regime. Results from the simulation are verified by comparison with exact analytical solutions for the steady state. Experimental methods for measuring transient nucleation are assessed, and it is demonstrated that the observed behavior depends on the method used. The effect of preexisting cluster distributions is studied. Previous analytical and numerical treatments of transient nucleation are compared to the solutions obtained from the simulation. The simple expressions of Kashchiev are shown to give good descriptions of the nucleation behavior.

  8. Keeping condensers clean

    SciTech Connect

    Wicker, K.

    2006-04-15

    The humble condenser is among the biggest contributors to a steam power plant's efficiency. But although a clean condenser can provide great economic benefit, a dirty one can raise plant heat rate, resulting in large losses of generation revenue and/or unnecessarily high fuel bills. Conventional methods for cleaning fouled tubes range form chemicals to scrapers to brushes and hydro-blasters. This article compares the available options and describes how one power station, Omaha Public Power District's 600 MW North Omaha coal-fired power station, cleaned up its act. The makeup and cooling water of all its five units comes from the Missouri River. 6 figs.

  9. Simple Simulations of DNA Condensation

    SciTech Connect

    STEVENS,MARK J.

    2000-07-12

    Molecular dynamics simulations of a simple, bead-spring model of semiflexible polyelectrolytes such as DNA are performed. All charges are explicitly treated. Starting from extended, noncondensed conformations, condensed structures form in the simulations with tetravalent or trivalent counterions. No condensates form or are stable for divalent counterions. The mechanism by which condensates form is described. Briefly, condensation occurs because electrostatic interactions dominate entropy, and the favored Coulombic structure is a charge ordered state. Condensation is a generic phenomena and occurs for a variety of polyelectrolyte parameters. Toroids and rods are the condensate structures. Toroids form preferentially when the molecular stiffness is sufficiently strong.

  10. Detail of Bright Angel stone vault, containing condenser, Hoffman condensation ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of Bright Angel stone vault, containing condenser, Hoffman condensation pump, Jennings vacuum heating pump, and misc. pipes and valves. - Grand Canyon Village Utilities, Grand Canyon National Park, Grand Canyon Village, Coconino County, AZ

  11. Computational Catalysis Using the Artificial Force Induced Reaction Method.

    PubMed

    Sameera, W M C; Maeda, Satoshi; Morokuma, Keiji

    2016-04-19

    The artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy is an automatic approach to explore all important reaction paths of complex reactions. Most traditional methods in computational catalysis require guess reaction paths. On the other hand, the AFIR approach locates local minima (LMs) and transition states (TSs) of reaction paths without a guess, and therefore finds unanticipated as well as anticipated reaction paths. The AFIR method has been applied for multicomponent organic reactions, such as the aldol reaction, Passerini reaction, Biginelli reaction, and phase-transfer catalysis. In the presence of several reactants, many equilibrium structures are possible, leading to a number of reaction pathways. The AFIR method in the GRRM strategy determines all of the important equilibrium structures and subsequent reaction paths systematically. As the AFIR search is fully automatic, exhaustive trial-and-error and guess-and-check processes by the user can be eliminated. At the same time, the AFIR search is systematic, and therefore a more accurate and comprehensive description of the reaction mechanism can be determined. The AFIR method has been used for the study of full catalytic cycles and reaction steps in transition metal catalysis, such as cobalt-catalyzed hydroformylation and iron-catalyzed carbon-carbon bond formation reactions in aqueous media. Some AFIR applications have targeted the selectivity-determining step of transition-metal-catalyzed asymmetric reactions, including stereoselective water-tolerant lanthanide Lewis acid-catalyzed Mukaiyama aldol reactions. In terms of establishing the selectivity of a reaction, systematic sampling of the transition states is critical. In this direction, AFIR is very useful for performing a systematic and automatic determination of TSs. In the presence of a comprehensive description of the transition states, the selectivity of the reaction can be calculated more accurately

  12. Computational Catalysis Using the Artificial Force Induced Reaction Method.

    PubMed

    Sameera, W M C; Maeda, Satoshi; Morokuma, Keiji

    2016-04-19

    The artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy is an automatic approach to explore all important reaction paths of complex reactions. Most traditional methods in computational catalysis require guess reaction paths. On the other hand, the AFIR approach locates local minima (LMs) and transition states (TSs) of reaction paths without a guess, and therefore finds unanticipated as well as anticipated reaction paths. The AFIR method has been applied for multicomponent organic reactions, such as the aldol reaction, Passerini reaction, Biginelli reaction, and phase-transfer catalysis. In the presence of several reactants, many equilibrium structures are possible, leading to a number of reaction pathways. The AFIR method in the GRRM strategy determines all of the important equilibrium structures and subsequent reaction paths systematically. As the AFIR search is fully automatic, exhaustive trial-and-error and guess-and-check processes by the user can be eliminated. At the same time, the AFIR search is systematic, and therefore a more accurate and comprehensive description of the reaction mechanism can be determined. The AFIR method has been used for the study of full catalytic cycles and reaction steps in transition metal catalysis, such as cobalt-catalyzed hydroformylation and iron-catalyzed carbon-carbon bond formation reactions in aqueous media. Some AFIR applications have targeted the selectivity-determining step of transition-metal-catalyzed asymmetric reactions, including stereoselective water-tolerant lanthanide Lewis acid-catalyzed Mukaiyama aldol reactions. In terms of establishing the selectivity of a reaction, systematic sampling of the transition states is critical. In this direction, AFIR is very useful for performing a systematic and automatic determination of TSs. In the presence of a comprehensive description of the transition states, the selectivity of the reaction can be calculated more accurately

  13. Condensate removal device

    DOEpatents

    Maddox, James W.; Berger, David D.

    1984-01-01

    A condensate removal device is disclosed which incorporates a strainer in unit with an orifice. The strainer is cylindrical with its longitudinal axis transverse to that of the vapor conduit in which it is mounted. The orifice is positioned inside the strainer proximate the end which is remoter from the vapor conduit.

  14. Inflation from gravitino condensates

    NASA Astrophysics Data System (ADS)

    Mavromatos, Nick E.

    2015-07-01

    We review work on the formation of gravitino condensates via the super-Higgs effect in the early Universe. This is a scenario for both inflating the early universe and breaking local supersymmetry(supergravity), entirely independent of any coupling to external matter. The goldstino mode associated with the breaking of (global) supersymmetry is “eaten” by the gravitino field, which becomes massive (via its own vacuum condensation) and breaks supergravity dynamically. The most natural association of gravitino condensates with inflation proceeds in an indirect way, via a Starobinsky-type inflation, in the massive gravitino phase. This inflationary phase is associated with scalar modes hidden in the higher order curvature corrections of the effective action arising from integrating out massive gravitino degrees of freedom. The scenario is in agreement with Planck data phenomenology in a natural and phenomenologically-relevant range of parameters, namely Grand-Unified-Theory values for the supersymmetry breaking energy scale and dynamically-induced gravitino mass. A hill-top inflation, on the other hand, which could also occur in the model, whereby the role of the inflaton field is played by the gravitino condensate itself, would require significant fine tuning in the inflaton's wave function renormalisation and thus may be discarded on naturalness grounds.

  15. [Development of new methods in asymmetric reactions and their applications].

    PubMed

    Node, Manabu

    2002-01-01

    Several novel methods using chiral reagents and biocatalysts for asymmetric reactions are described. Among those reactions, asymmetric reduction via a novel tandem Michael addition/Meerwein-Ponndorf-Verley reduction of acyclic alpha,beta-unsaturated ketones using a chiral mercapto alcohol, asymmetric synthesis of allene-1,3-dicarboxylate via crystallization induced asymmetric transformation, and improved asymmetric nitroolefination of lactones and lactames at alpha-carbon using new chiral reagents were developed. In the reactions using biocatalysts, asymmetric dealkoxycarbonylation of bicyclic beta-keto diesters having sigma-symmetry with lipase or esterase to give optically active beta-keto esters, the asymmetric reduction of bicyclic 1,3-diketones having sigma-symmetry with Baker's yeast to give optically active keto alcohols, and the asymmetric aldol reaction of glycine with threonine aldolase were also developed. The above mentioned products were effectively utilized as chiral building blocks for the asymmetric synthesis of natural products and drugs.

  16. Organolanthanide reagents and the Mukaiyama reaction

    SciTech Connect

    Gong, L.

    1989-01-01

    The bis(pentamethylcyclopentadienyl) lutetium halide complex ((C/sub 5/Me/sub 5/)/sub 2/LuCl/center dot/THF) was synthesized and characterized. The crystal structure of this complex shows that the Lu is at the center of a distorted tetrahedron consisting of the centroids of two cyclopentadienyl rings, the oxygen atom of a tetrahydrofuran molecule and a chlorine atom. /sup 1/H NMR studies of toluene-d/sub 8/ solutions of (C/sub 5/Me/sub 5/LuCl(THF) + THF, (TMS/sub 2/CP)/sub 2/LuCl(THF) + THF, and (MeCp)/sub 2/LuCl(THF) + THF at various temperatures showed exchange processes between co- ordinated THF and free THF with average values of ..delta..G/sup ne/ of 13.0 /+-/ 0.3 kcal/mol, 11.1 /+-/ 0.1 kcal/mol and <11 kcal/mol at 0/degree/C, respectively. It has been found that under the influence of a catalytic amount (1--5 mol %) of (TMS/sub 2/Cp)/sub 2/YbCl dimer, silyl enol ethers (R/sub 1/R/sub 2/C = C(OR/sub 3/)OSiMe/sub 3/)) react with benzaldehyde smoothly in dichloromethane at room temperature, giving >99% of the aldol silyl ether (isolated yield: 90%) within 3 h. At /minus/78/degrees/C, the reaction gives kinetically controlled diastereoselectivity, which was not observed in the TiCl/sub 4/-mediated aldol reaction. The use of organoytterbium enolates shows promise result with respect to increased stereoselectivity, and indicates the importance of the bulky ligands on the metal center. In addition, Yb(III) species can retard retroaldol reaction owing to its mild Lewis acidity. 118 refs., 14 figs., 30 tabs.

  17. Highly selective condensation of biomass-derived methyl ketones as a source of aviation fuel.

    PubMed

    Sacia, Eric R; Balakrishnan, Madhesan; Deaner, Matthew H; Goulas, Konstantinos A; Toste, F Dean; Bell, Alexis T

    2015-05-22

    Aviation fuel (i.e., jet fuel) requires a mixture of C9 -C16 hydrocarbons having both a high energy density and a low freezing point. While jet fuel is currently produced from petroleum, increasing concern with the release of CO2 into the atmosphere from the combustion of petroleum-based fuels has led to policy changes mandating the inclusion of biomass-based fuels into the fuel pool. Here we report a novel way to produce a mixture of branched cyclohexane derivatives in very high yield (>94 %) that match or exceed many required properties of jet fuel. As starting materials, we use a mixture of n-alkyl methyl ketones and their derivatives obtained from biomass. These synthons are condensed into trimers via base-catalyzed aldol condensation and Michael addition. Hydrodeoxygenation of these products yields mixtures of C12 -C21 branched, cyclic alkanes. Using models for predicting the carbon number distribution obtained from a mixture of n-alkyl methyl ketones and for predicting the boiling point distribution of the final mixture of cyclic alkanes, we show that it is possible to define the mixture of synthons that will closely reproduce the distillation curve of traditional jet fuel.

  18. Pd/NbOPO₄ multifunctional catalyst for the direct production of liquid alkanes from aldol adducts of furans.

    PubMed

    Xia, Qi-Neng; Cuan, Qian; Liu, Xiao-Hui; Gong, Xue-Qing; Lu, Guan-Zhong; Wang, Yan-Qin

    2014-09-01

    Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256 h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1) The noble metal (in this case Pd) is the active center for hydrogenation; 2) NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3) a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions. PMID:25045056

  19. Orientation Dependence of Jumping Droplet Condensation

    NASA Astrophysics Data System (ADS)

    Berrier, Austin; Boreyko, Jonathan; Nature-Inspired Fluids; Interfaces Team

    2015-11-01

    On nanostructured superhydrophobic surfaces, microscopic condensate exhibits out-of-plane jumping that minimizes the average droplet size for maximal phase-change heat transfer. This jumping-droplet phenomenon occurs independently of gravity and is due to surface energy being partially converted to kinetic energy upon coalescence events. Although the initial departure of the jumping droplets is independent of gravity, the subsequent trajectories exhibit a dependence upon the orientation of the substrate. The drop size distribution of jumping-droplet condensation growing on a superhydrophobic substrate was characterized for both horizontal and vertical surface orientations. With the horizontal orientation, jumping condensate returns to the substrate by gravity. While this can result in chain reactions with other droplets to trigger further jumping events, eventually the rebounding droplets become too large to jump and are stuck on the surface. In contrast, droplets jumping off a vertically oriented surface do not return to the substrate. For this reason, the maximum droplet diameters during condensation growth were found to be significantly larger on the horizontally oriented superhydrophobic surface than on the vertical orientation.

  20. Photon condensation: A new paradigm for Bose-Einstein condensation

    NASA Astrophysics Data System (ADS)

    Rajan, Renju; Ramesh Babu, P.; Senthilnathan, K.

    2016-10-01

    Bose-Einstein condensation is a state of matter known to be responsible for peculiar properties exhibited by superfluid Helium-4 and superconductors. Bose-Einstein condensate (BEC) in its pure form is realizable with alkali atoms under ultra-cold temperatures. In this paper, we review the experimental scheme that demonstrates the atomic Bose-Einstein condensate. We also elaborate on the theoretical framework for atomic Bose-Einstein condensation, which includes statistical mechanics and the Gross-Pitaevskii equation. As an extension, we discuss Bose-Einstein condensation of photons realized in a fluorescent dye filled optical microcavity. We analyze this phenomenon based on the generalized Planck's law in statistical mechanics. Further, a comparison is made between photon condensate and laser. We describe how photon condensate may be a possible alternative for lasers since it does not require an energy consuming population inversion process.

  1. Uptake and Reactions of Formaldehyde, Acetaldehyde, Acetone, Propanal and Ethanol in Sulfuric Acid solutions at 200-240 K: Implications for upper tropospheric aerosol composition

    NASA Astrophysics Data System (ADS)

    Iraci, L. T.; Williams, M. B.; Axson, J.; Michelsen, R.

    2007-12-01

    The production of light absorbing, organic material in aerosol that is normally considered to be transparent in the UV and visible wavelength regions has significant implications for biogeochemical cycling and climate modelling. Production mechanisms likely involve carbonyl compounds such as formaldehyde, acetone, acetaldehyde and propanal that are present in significant quantities in the upper troposphere (UT). In this study, we have performed experiments focusing on a class of acid catalyzed carbonyl reactions, the formation of acetals. R2C=O + 2R'OH --> R2C(OR')2 + H2O Using a Knudsen cell apparatus, we have measured the rate of uptake of formaldehyde, acetaldehyde, acetone, propanal, and ethanol into sulfuric acid solutions ranging between 40-70 wt% of acid, containing 0-0.1 M of ethanol, acetone or formaldehyde at temperatures of 220-250 K. For all reactant pairs, the aldol condensation path, including self reaction, should be insignificant at the acidities studied. Evidence for reaction between organics was observed for all pairs, except those involving propanal which were likely limited by the very low solubility. We attribute enhanced uptake to the formation of acetals, such as 1,1-diethoxyethane and 2,2- diethoxypropane, among others. Enhanced uptake was observed to proceed on timescales > 1 hour and sometimes shows complex dependence on acidity that is likely related to speciation of the individual carbonyls in acidic solution. The acetal products do not absorb in the visible but are less volatile than parent molecules, allowing for accumulation in sulfuric acid particles, and enhanced uptake. Cross reactions of carbonyls with alcohols in sulfuric acid medium have not been previously measured, yet methanol and ethanol show high solubility and are present at significant concentrations in the UT. Thus even at slow reaction rates, the acetal reaction has ample starting material and proceeds under conditions common to the UT. We will present results for the

  2. Construction of highly functionalized diazoacetoacetates via catalytic Mukaiyama-Michael reactions.

    PubMed

    Liu, Yu; Zhang, Yu; Jee, Noel; Doyle, Michael P

    2008-04-17

    Functionalized diazo acetoacetates are prepared by an efficient Mukaiyama-Michael reaction between methyl 3-(trialkylsilanoxy)-2-diazo-3-butenoate and alpha,beta-unsaturated enones. Vinyl ether and ketone derivatives are both accessible in good to excellent yield through this methodology. The mild Lewis acid zinc(II) triflate is the optimal catalyst, and its loading can be as low as 0.1 mol %. In addition, zinc triflate was also found to be a superior catalyst for the related Mukaiyama-aldol reaction.

  3. 'Super Silyl' Group for Diastereoselective Sequential Reactions: Access to Complex Chiral Architecture in One Pot

    SciTech Connect

    Boxer, Matthew B.; Yamamoto, Hisashi

    2008-04-02

    We have shown that the tris(trimethylsilyl)silyl (TTMSS) silyl enol ether of acetaldehyde undergoes aldehyde cross-aldol reactions with high selectivity and the extremely low catalyst loading (0.05 mol % of HNTf{sub 2}) allows for one-pot sequential reactions where acidic or basic nucleophiles can be subsequently added. Various ketone-derived silyl enol ethers, Grignard reagents, and dienes succeeded, generating relatively complex molecular architectures in a single step. This represents the first case where, in a single pot, highly acidic conditions followed by very basic conditions were tolerated to give products with high diastereoselectivities and good yields.

  4. Synthesis of 2,3-anti-3,4-anti and 2,3-anti-3,4-syn propionate motifs: a diastereoselective tandem sequence of Mukaiyama and free-radical-based hydrogen transfer reactions.

    PubMed

    Guindon, Yvan; Prévost, Michel; Mochirian, Philippe; Guérin, Brigitte

    2002-03-21

    [reaction: see text] Reported herein is a strategy employing a Mukaiyama reaction in tandem with a hydrogen transfer reaction for the elaboration of 2,3-anti-3,4-anti and 2,3-anti-3,4-syn propionate motifs. The mode of complexation is controlled through monodentate or chelate pathways for the Mukaiyama reaction to give access to either syn or anti aldol products, precursors of the free-radical reduction reaction. Boron Lewis acid is used to control the free-radical reaction through the exocyclic pathway.

  5. Gravity triggered neutrino condensates

    SciTech Connect

    Barenboim, Gabriela

    2010-11-01

    In this work we use the Schwinger-Dyson equations to study the possibility that an enhanced gravitational attraction triggers the formation of a right-handed neutrino condensate, inducing dynamical symmetry breaking and generating a Majorana mass for the right-handed neutrino at a scale appropriate for the seesaw mechanism. The composite field formed by the condensate phase could drive an early epoch of inflation. We find that to the lowest order, the theory does not allow dynamical symmetry breaking. Nevertheless, thanks to the large number of matter fields in the model, the suppression by additional powers in G of higher order terms can be compensated, boosting them up to their lowest order counterparts. This way chiral symmetry can be broken dynamically and the infrared mass generated turns out to be in the expected range for a successful seesaw scenario.

  6. Feshbach-Einstein Condensates

    SciTech Connect

    Rousseau, V. G.; Denteneer, P. J. H.

    2009-01-09

    We investigate the phase diagram of a two-species Bose-Hubbard model describing atoms and molecules on a lattice, interacting via a Feshbach resonance. We identify a region where the system exhibits an exotic super-Mott phase and regions with phases characterized by atomic and/or molecular condensates. Our approach is based on a recently developed exact quantum Monte Carlo algorithm: the stochastic Green function algorithm with tunable directionality. We confirm some of the results predicted by mean-field studies, but we also find disagreement with these studies. In particular, we find a phase with an atomic but no molecular condensate, which is missing in all mean-field phase diagrams.

  7. Multilayer graphene condenser microphone

    NASA Astrophysics Data System (ADS)

    Todorović, Dejan; Matković, Aleksandar; Milićević, Marijana; Jovanović, Djordje; Gajić, Radoš; Salom, Iva; Spasenović, Marko

    2015-12-01

    Vibrating membranes are the cornerstone of acoustic technology, forming the backbone of modern loudspeakers and microphones. Acoustic performance of a condenser microphone is derived mainly from the membrane’s size, surface mass and achievable static tension. The widely studied and available nickel has been a dominant membrane material for professional microphones for several decades. In this paper we introduce multilayer graphene as a membrane material for condenser microphones. The graphene device outperforms a high end commercial nickel-based microphone over a significant part of the audio spectrum, with a larger than 10 dB enhancement of sensitivity. Our experimental results are supported with numerical simulations, which also show that a 300 layer thick graphene membrane under maximum tension would offer excellent extension of the frequency range, up to 1 MHz.

  8. Chondrules as condensation products

    NASA Technical Reports Server (NTRS)

    Wood, J. A.; Mcsween, H. Y., Jr.

    1977-01-01

    The formation of meteoritic chondrules via condensation from the primordial solar nebula is discussed. Chondrule formation in regions where the gas/dust ratio was enhanced, and where transient high energy events heated the gas and temporarily vaporized the dust, is advocated. The observed diversity of chondrule types can be understood as resulting from local variations in the initial gas/dust proportions and other parameters.

  9. Bose-Einstein Condensation

    SciTech Connect

    El-Sherbini, Th.M.

    2005-03-17

    This article gives a brief review of Bose-Einstein condensation. It is an exotic quantum phenomenon that was observed in dilute atomic gases for the first time in 1995. It exhibits a new state of matter in which a group of atoms behaves as a single particle. Experiments on this form of matter are relevant to many different areas of physics- from atomic clocks and quantum computing to super fluidity, superconductivity and quantum phase transition.

  10. Design of chiral urea-quaternary ammonium salt hybrid catalysts for asymmetric reactions of glycine Schiff bases†

    PubMed Central

    Tiffner, Maximilian; Novacek, Johanna; Busillo, Alfonso; Gratzer, Katharina; Massa, Antonio; Waser, Mario

    2015-01-01

    Bifunctional chiral urea-containing quaternary ammonium salts can be straightforwardly synthesised in good yield and with high structural diversity via a scalable and operationally simple highly telescoped sequence starting from trans-1,2-cyclohexanediamine. These novel hybrid catalysts were systematically investigated for their potential to control glycine Schiff bases in asymmetric addition reactions. It was found that Michael addition reactions and the herein presented aldol-initiated cascade reaction can be carried out to provide enantiomeric ratios up to 95 : 5 and good yields under mild conditions at room temperature. PMID:26504516

  11. Asymmetric condensed dark matter

    NASA Astrophysics Data System (ADS)

    Aguirre, Anthony; Diez-Tejedor, Alberto

    2016-04-01

    We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate must be lighter than a few tens of eV so that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of decoupling to the scale of the QCD phase transition or above. This requires large dark matter-to-photon ratios and very weak interactions with standard model particles.

  12. Effect of spontaneous condensation on condensation heat transfer in the presence of non-condensable gases

    SciTech Connect

    Karl, J.; Hein, D.

    1999-07-01

    The presence of non condensable gases like nitrogen or air reduces the condensation heat transfer during condensation of binary steam mixtures. The non condensable gas accumulates in the vapor phase boundary layer and causes a high heat transfer resistance. Especially with high pressures and low water temperatures spontaneous condensation reduces heat transfer additionally. Fog forms within the steam-nitrogen boundary layer and the steam condenses on the water droplets of the fog layer. The convective mass transfer to the cooling water interface diminishes. Raman spectroscopy and film theory are used to quantify this effect locally. The calculation of overall condensation rates in large steam nitrogen systems requires to use three dimensional CFD codes. The paper presents equations to predict fog formation in the boundary layer which can be implemented in CFD codes.

  13. Confinement Contains Condensates

    SciTech Connect

    Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

    2012-03-12

    Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass-scales that fill all spacetime, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence, and incidentally expose misconceptions in a recent Comment.

  14. Expansion in condensates

    SciTech Connect

    Chakrabarti, J.; Sajjad Zahir, M.

    1985-03-01

    We show that the product of local current operators in quantum chromodynamics (QCD), when expanded in terms of condensates, such as psi-barpsi, G/sup a//sub munu/ G/sup a//sub munu/, psi-barGAMMA psipsi-barGAMMApsi, f/sub a/bcG/sup a//sub munu/G/sup b//sub nualpha/ x G/sup c//sub alphamu/, etc., yields a series in Planck's constant. This, however, provides no hint that the higher terms in such an expansion may be less significant.

  15. Condensed Plasmas under Microgravity

    NASA Technical Reports Server (NTRS)

    Morfill, G. E.; Thomas, H. M.; Konopka, U.; Rothermel, H.; Zuzic, M.; Ivlev, A.; Goree, J.; Rogers, Rick (Technical Monitor)

    1999-01-01

    Experiments under microgravity conditions were carried out to study 'condensed' (liquid and crystalline) states of a colloidal plasma (ions, electrons, and charged microspheres). Systems with approximately 10(exp 6) microspheres were produced. The observed systems represent new forms of matter--quasineutral, self-organized plasmas--the properties of which are largely unexplored. In contrast to laboratory measurements, the systems under microgravity are clearly three dimensional (as expected); they exhibit stable vortex flows, sometimes adjacent to crystalline regions, and a central 'void,' free of microspheres.

  16. Evaporation and condensation at a liquid surface. I. Argon

    NASA Astrophysics Data System (ADS)

    Yasuoka, Kenji; Matsumoto, Mitsuhiro; Kataoka, Yosuke

    1994-11-01

    Molecular dynamics computer simulations were carried out to investigate the dynamics of evaporation and condensation for argon at the temperature of 80 and 100 K. From the decrease of the survival probability of vapor molecules, the ratio of self reflection to collision is estimated to be 12%-15%, only weakly dependent on the temperature. This suggests that argon vapor molecules are in the condition of almost complete capture, and the condensation is considered to be a barrierless process. The total ratio of reflection which is evaluated with the flux correlation of condensation and evaporation is 20% at both temperature. The difference between these two ratios of reflection is ascribed to a phenomenon that vapor molecules colliding with the surface drive out other liquid molecules. This molecule exchange at the surface is as important as the self-reflection, and the conventional picture of condensation as a unimolecular chemical reaction is not appropriate.

  17. Quantitative assessment of DNA condensation.

    PubMed

    Trubetskoy, V S; Slattum, P M; Hagstrom, J E; Wolff, J A; Budker, V G

    1999-02-15

    A fluorescent method is proposed for assessing DNA condensation in aqueous solutions with variety of condensing agents. The technique is based on the effect of concentration-dependent self-quenching of covalently bound fluorophores upon DNA collapse. The method allows a more precise determination of charge equivalency in titration experiments with various polycations. The technique's ability to determine the number of DNA molecules that are condensed together in close proximity is under further investigation.

  18. Mitotic chromosome structure and condensation.

    PubMed

    Belmont, Andrew S

    2006-12-01

    Mitotic chromosome structure has been the cell biology equivalent of a 'riddle, wrapped in a mystery, inside an enigma'. Observations that genetic knockout or knockdown of condensin subunits or topoisomerase II cause only minimal perturbation in overall chromosome condensation, together with analysis of early stages of chromosome condensation and effects produced by histone H1 depletion, suggest a need to reconsider textbook models of mitotic chromosome condensation and organization. PMID:17046228

  19. Strange Disoriented Chiral Condensates

    NASA Astrophysics Data System (ADS)

    Abdel-Aziz, Mohamed; Gavin, Sean

    2002-10-01

    Enhancement of omega and anti-omega baryon production in Pb+Pb collisions at the CERN SPS can be explained by the formation of many small regions of disordered chiral condensate. This explanation implies that neutral and charged kaons as well as pions must exhibit novel isospin fluctuations. Fluctuations due to transient behavior of the Polyakov Loop condensate can produce similar phenomena. Kapusta and Gavin have computed the distribution of the fraction of neutral pions and kaons from such regions. We proposed robust statistical observables that can be used to extract the novel isospin fluctuations from background contributions in neutral/charged pion and K-short/K-charged correlation measurements at RHIC and LHC. The STAR experiment is currently examining K-short/K-charged correlations. Note that Pruneau, Voloshin and Gavin have proposed similar observables to study net-charge fluctuations. To obtain a baseline for comparison to RHIC and SPS experiments, Abdel-Aziz and Gavin compute these observables using numerical simulations using HIJING and URQMD event generators. We also obtain limits on the size and number of disordered regions by comparing to photon and charged-pion searches from WA98 and other SPS experiments. We will compare to the first results from STAR K-short/K-charged analysis.

  20. Kaon Condensation with Lattice QCD

    SciTech Connect

    Detmold, Will; Detmold, William; Detmold, Will; Detmold, William; Savage, Martin; Walker-Loud, Andre; Orginos, Konstantinos; Torok, Aaron

    2008-09-01

    doi: http://dx.doi.org/10.1103/PhysRevD.78.054514
    Kaon condensation may play an important role in the structure of hadronic matter at densities greater than that of nuclear matter, as exist in the interior of neutron stars. We present the results of the first lattice QCD calculation of kaon condensation obtained by studying systems containing up to twelve charged kaons. Surprisingly, the equation of state of the condensate is remarkably well reproduced by leading order chiral perturbation theory. We determine the three-kaon interaction from the multi-kaon systems and update our results for pion condensates.

  1. Potentially Prebiotic Syntheses of Condensed Phosphates

    NASA Technical Reports Server (NTRS)

    Keefe, Anthony D.; Miller, Stanley L.

    1996-01-01

    In view of the importance of a prebiotic source of high energy phosphates, we have investigated a number of potentially prebiotic processes to produce condensed phosphates from orthophosphate and cyclic trimetaphosphate from tripolyphosphate. The reagents investigated include polymerizing nitriles, acid anhydrides, lactones, hexamethylene tetramine and carbon suboxide. A number of these processes give substantial yields of pyrophosphate from orthophosphate and trimetaphosphate from tripolyphosphate. Although these reactions may have been applicable in local areas, they are not sufficiently robust to have been of importance in the prebiotic open ocean.

  2. Condensation Processes in Geothermal Systems

    NASA Astrophysics Data System (ADS)

    Norman, D. I.; Moore, J. N.

    2005-12-01

    We model condensation processes in geothermal systems to understand how this process changes fluid chemistry. We assume two processes operate in geothermal systems: 1) condensation of a vapor phase derived by boiling an aqueous geothermal fluid into a cool near surface water and 2) condensation of a magmatic vapor by a deep circulating meteoric thermal fluid. It is assumed that the condensation process has two stages. Initially the condensing fluid is under saturated in gaseous species. Condensation of the vapor phase continues until the pressure on the fluid equals the sum of the partial pressures of water and the dissolved gaseous species. At that time bubbles flux through the condensing fluid. In time the fluid and fluxing gas phase come to equilibrium. Calculation shows that during the second stage of the condensation process the liquid phase becomes enriched in more soluble gaseous species like CO2 and H2S, and depleted in less soluble species like CH4 and N2. Stage 2 condensation processes can therefore be monitored by ratios of more and less condensable species like CO2/N2. Condensation of vapor released by boiling geothermal fluids results in liquids with high concentrations of H2S and CO2 like is seen in geothermal system steam-heated waters. Condensation of a magmatic vapor into circulating meteoric water has been proposed, but not well demonstrated. We compare to our models the Cerro Prieto, Mexico gas analysis data set collected over twelve years time by USGS personnel. It was assumed for modeling that the Cerro Prieto geothermal fluids are circulating meteoritic fluids with N2/Ar ratios about 40 to which is added a magmatic vapor with N2/Ar ratio = 400. The Cerro Prieto analyses show a strong correlation between N2/Ar and CO2/N2 as predicted by calculation. Two dimensional image plots of well N2/Ar + CO2/N2 show a bull's-eye pattern on the geothermal field. Image plots of analyses collected over a year or less time show N2/Ar and CO2/N2 hot spots

  3. Selective condensation of DNA by aminoglycoside antibiotics.

    PubMed

    Kopaczynska, M; Schulz, A; Fraczkowska, K; Kraszewski, S; Podbielska, H; Fuhrhop, J H

    2016-05-01

    The condensing effect of aminoglycoside antibiotics on the structure of double-stranded DNA was examined. The selective condensation of DNA by small molecules is an interesting approach in biotechnology. Here, we present the interaction between calf thymus DNA and three types of antibiotic molecules: tobramycin, kanamycin, and neomycin. Several techniques were applied to study this effect. Atomic force microscopy, transmission electron microscopy images, and nuclear magnetic resonance spectra showed that the interaction of tobramycin with double-stranded DNA caused the rod, toroid, and sphere formation and very strong condensation of DNA strands, which was not observed in the case of other aminoglycosides used in the experiment. Studies on the mechanisms by which small molecules interact with DNA are important in understanding their functioning in cells, in designing new and efficient drugs, or in minimizing their adverse side effects. Specific interactions between tobramycin and DNA double helix was modeled using molecular dynamics simulations. Simulation study shows the aminoglycoside specificity to bend DNA double helix, shedding light on the origins of toroid formation. This phenomenon may lighten the ototoxicity or nephrotoxicity issues, but also other adverse reactions of aminoglycoside antibiotics in the human body.

  4. Condenser for photolithography system

    SciTech Connect

    Sweatt, William C.

    2004-03-02

    A condenser for a photolithography system, in which a mask image from a mask is projected onto a wafer through a camera having an entrance pupil, includes a source of propagating radiation, a first mirror illuminated by the radiation, a mirror array illuminated by the radiation reflected from said first mirror, and a second mirror illuminated by the radiation reflected from the array. The mirror array includes a plurality of micromirrors. Each of the micromirrors is selectively actuatable independently of each other. The first mirror and the second mirror are disposed such that the source is imaged onto a plane of the mask and the mirror array is imaged into the entrance pupil of the camera.

  5. Microgravity condensing heat exchanger

    NASA Technical Reports Server (NTRS)

    Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

    2011-01-01

    A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

  6. APPARATUS FOR CONDENSATION AND SUBLIMATION

    DOEpatents

    Schmidt, R.J.; Fuis, F. Jr.

    1958-10-01

    An apparatus is presented for the sublimation and condensation of uranium compounds in order to obtain an improved crystalline structure of this material. The apparatus comprises a vaporizing chamber and condensing structure connected thereto. There condenser is fitted with a removable liner having a demountable baffle attached to the liner by means of brackets and a removable pin. The baffle is of spiral cross-section and is provided with cooling coils disposed between the surfaces of the baffle for circulation of a temperature controlling liquid within the baffle. The cooling coll provides for controlllng the temperature of the baffle to insure formatlon of a satisfactory condensate, and the removable liner facilitates the removal of condensate formed during tbe sublimation process.

  7. MICROWAVE-ACCELERATED MULTICOMPONENT REACTIONS UNDER SOLVENT-FREE CONDITIONS

    EPA Science Inventory

    The application of microwave-accelerated solventless synthetic protocols in multicomponent (MCC) reactions will be exemplified by several condensation and cyclization reactions including the rapid one-pot assembly of valuable heterocyclic compounds from in situ generated intermed...

  8. Condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Yamanaka, Junpei; Inomata, Katsuhiko; Yamagata, Yukio

    1988-09-01

    The dehydration condensation of glycine with trimetaphosphate in aqueous solution has been reinvestigated. Although it has been reported that the condensation of glycine under the alkaline conditions was brought about through the formation of cyclic acylphosphoramidate and hence the condensation of polyglycines could not occur, we found that the condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solution are possible through the formation of their acylphosphates under the neutral or weak acidic conditions. Aqueous solutions of 1.0 M glycylglycine and 1.0 M trimetaphosphate in the various pH from 4.0 to 9.0 were incubated at 38 °C. The solutions were analyzed by HPLC with ninhydrin reaction system. Tetraglycine and hexaglycine were detected and their maximum yields were given in the reaction carried out around pH 7. They are approximately 15% and 4% after 30 days, respectively. Analogous experiments were performed with tetrametaphosphate. The results showed a similar pH dependence for the condensation, but the yields were about one-tenth of those of corresponding experiments with trimetaphosphate. Relative rates of dimerization of glycine, diglycine and triglycine in the equimolar concentration were also investigated at pH 6.0 at 38 °C. The rates for digylcine and triglycine were approximately twice and four times as large as that for glycine. Relevance of the experiments to chemical evolution is discussed.

  9. Integrated Rig for the Production of Boron Nitride Nanotubes via the Pressurized Vapor-Condenser Method

    NASA Technical Reports Server (NTRS)

    Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor)

    2014-01-01

    An integrated production apparatus for production of boron nitride nanotubes via the pressure vapor-condenser method. The apparatus comprises: a pressurized reaction chamber containing a continuously fed boron containing target having a boron target tip, a source of pressurized nitrogen and a moving belt condenser apparatus; a hutch chamber proximate the pressurized reaction chamber containing a target feed system and a laser beam and optics.

  10. Integrated rig for the production of boron nitride nanotubes via the pressurized vapor-condenser method

    DOEpatents

    Smith, Michael W; Jordan, Kevin C

    2014-03-25

    An integrated production apparatus for production of boron nitride nanotubes via the pressure vapor-condenser method. The apparatus comprises: a pressurized reaction chamber containing a continuously fed boron containing target having a boron target tip, a source of pressurized nitrogen and a moving belt condenser apparatus; a hutch chamber proximate the pressurized reaction chamber containing a target feed system and a laser beam and optics.

  11. Water condensation: a multiscale phenomenon.

    PubMed

    Jensen, Kasper Risgaard; Fojan, Peter; Jensen, Rasmus Lund; Gurevich, Leonid

    2014-02-01

    The condensation of water is a phenomenon occurring in multiple situations in everyday life, e.g., when fog is formed or when dew forms on the grass or on windows. This means that this phenomenon plays an important role within the different fields of science including meteorology, building physics, and chemistry. In this review we address condensation models and simulations with the main focus on heterogeneous condensation of water. The condensation process is, at first, described from a thermodynamic viewpoint where the nucleation step is described by the classical nucleation theory. Further, we address the shortcomings of the thermodynamic theory in describing the nucleation and emphasize the importance of nanoscale effects. This leads to the description of condensation from a molecular viewpoint. Also presented is how the nucleation can be simulated by use of molecular models, and how the condensation process is simulated on the macroscale using computational fluid dynamics. Finally, examples of hybrid models combining molecular and macroscale models for the simulation of condensation on a surface are presented.

  12. Condensation in Nanoporous Packed Beds.

    PubMed

    Ally, Javed; Molla, Shahnawaz; Mostowfi, Farshid

    2016-05-10

    In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed. Direct visualization allows the extent of condensation to be observed, as well as inference of the pore geometry from Bragg diffraction. We show experimentally that capillary condensation depends on pore geometry and wettability because these factors determine the shape of the menisci that coalesce when pore filling occurs, contrary to the typical assumption that all pore structures can be modeled as cylindrical and perfectly wetting. We also observe capillary condensation at higher pressures than has been done previously, which is important because many applications involving this phenomenon occur well above atmospheric pressure, and there is little, if any, experimental validation of capillary condensation at such pressures, particularly with direct visualization.

  13. Characterization of spacecraft humidity condensate

    NASA Technical Reports Server (NTRS)

    Muckle, Susan; Schultz, John R.; Sauer, Richard L.

    1994-01-01

    When construction of Space Station Freedom reaches the Permanent Manned Capability (PMC) stage, the Water Recovery and Management Subsystem will be fully operational such that (distilled) urine, spent hygiene water, and humidity condensate will be reclaimed to provide water of potable quality. The reclamation technologies currently baselined to process these waste waters include adsorption, ion exchange, catalytic oxidation, and disinfection. To ensure that the baseline technologies will be able to effectively remove those compounds presenting a health risk to the crew, the National Research Council has recommended that additional information be gathered on specific contaminants in waste waters representative of those to be encountered on the Space Station. With the application of new analytical methods and the analysis of waste water samples more representative of the Space Station environment, advances in the identification of the specific contaminants continue to be made. Efforts by the Water and Food Analytical Laboratory at JSC were successful in enlarging the database of contaminants in humidity condensate. These efforts have not only included the chemical characterization of condensate generated during ground-based studies, but most significantly the characterization of cabin and Spacelab condensate generated during Shuttle missions. The analytical results presented in this paper will be used to show how the composition of condensate varies amongst enclosed environments and thus the importance of collecting condensate from an environment close to that of the proposed Space Station. Although advances were made in the characterization of space condensate, complete characterization, particularly of the organics, requires further development of analytical methods.

  14. The evolutionary design of condensers

    NASA Astrophysics Data System (ADS)

    Bejan, A.; Lee, J.; Lorente, S.; Kim, Y.

    2015-03-01

    Condensers are flow architectures needed to provide high rates of condensation (or cooling) per unit volume, in enclosures with fixed volume. Their design has not changed from configurations consisting of the banks of horizontal tubes. In this paper, we outline a free path to evolving the design by exploring new features of flow configuration: flattened tubes, multiple tube sizes, arrays of flattened tubes, vertical tubes with turbulent film flow, forced convection condensation instead of gravity driven condensation, and the optimal length of a horizontal tube, i.e., the number of tubes in a column aligned with vapor cross flow. We show that the condensation density can be increased sizably by varying freely and without bias the morphology of the flow system: the shapes and arrangement of the cooled surfaces on which condensation occurs. The evolution of technology is described in terms of the special time direction of the useful (purposeful) changes in the configuration (shapes, arrangements) of surfaces on which flow/condensation occurs. This explains what "evolution" means. It is an important step for physics, not just technology.

  15. Condensation in Nanoporous Packed Beds.

    PubMed

    Ally, Javed; Molla, Shahnawaz; Mostowfi, Farshid

    2016-05-10

    In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed. Direct visualization allows the extent of condensation to be observed, as well as inference of the pore geometry from Bragg diffraction. We show experimentally that capillary condensation depends on pore geometry and wettability because these factors determine the shape of the menisci that coalesce when pore filling occurs, contrary to the typical assumption that all pore structures can be modeled as cylindrical and perfectly wetting. We also observe capillary condensation at higher pressures than has been done previously, which is important because many applications involving this phenomenon occur well above atmospheric pressure, and there is little, if any, experimental validation of capillary condensation at such pressures, particularly with direct visualization. PMID:27115446

  16. Control of VOCs emissions by condenser pre-treatment in a semiconductor fab.

    PubMed

    Lin, Yu-Chih; Chang, Feng-Tang; Bai, Hsunling; Pei, Bau-Shei

    2005-04-11

    The performance of a modified design of local condensers to pre-treat a variety of volatile organic compounds (VOCs) emitted from the stripping process of a semiconductor fab was tested in this study. The reaction temperature of the condensers was controlled at around 10 degrees C, it is relatively higher than the traditional condenser reaction temperature. Both VOCs and water vapors were condensed and formed liquid films. This resulted in an enhancement of the VOCs removals, especially for VOCs of high boiling points or solubility. This can help to prevent the follow up zeolite concentrator from damage. The performance of the integrated system of condenser/zeolite concentrator could, therefore, remain highly efficient for a longer operation time. Its annualized cost would also be lower than installing the zeolite concentrator only. PMID:15811658

  17. Coulomb interactions and fermion condensation

    SciTech Connect

    Capstick, S.; Cutkosky, R.E.; Joensen, M.A. ); Wang, K.C. )

    1990-08-15

    The influence of the Coulomb interaction in states containing massless and flavorless fermion-antifermion pairs is studied, using a continuum formulation within the finite volume {ital S}{sup 3}. Several different forms for the Coulomb interaction are examined, including confining potentials as well as nonconfining potentials. The calculations show that if the interaction is strong enough, the Coulomb interaction leads to condensation of pairs, and that this condensation has a chiral character. The condensation does not depend on whether the interaction is confining. It is found that simplified variational approximations are not accurate enough for an adequate description of the states.

  18. Neonatal hygroscopic condenser humidifier.

    PubMed

    Gedeon, A; Mebius, C; Palmer, K

    1987-01-01

    A hygroscopic condenser humidifier was developed for neonates on mechanical ventilation and was evaluated by laboratory tests and clinically. Humidification provided by the unit was measured in the 10- to 50-ml tidal-volume range at ambient temperatures of 24 degrees C and 38 degrees C. The effect of a leaking patient connection on device performance was investigated. Leakage rates were measured routinely in a neonatal ICU and surgery to determine the clinical significance. In the entire tidal volume and temperature range, the unit provided an inspiratory water content in excess of 30 g/m3 when the leak fraction (volume leaked/volume delivered at Y-piece) was less than 15%. This was found in three out of four cases. In about one out of ten cases, the leak exceeded 30%, which invariably led to corrective action, such as repositioning or changing the endotracheal tube. However, even at a 30% leak, a water content of about 26 g/m3 was still available for humidifying the inspired gas, which corresponds to normal physiologic conditions found in the trachea for nasal breathing of room air.

  19. Studies of the condensation of sulfones with ketones and aldehydes.

    PubMed

    Garst, Michael E; Dolby, Lloyd J; Esfandiari, Shervin; Okrent, Rachel A; Avey, Alfred A

    2006-01-20

    [reaction: see text] The condensation of ketones or aldehydes with sulfones was shown to give a variety of products. Condensation of 2-methylcyclohexanone with dimethyl sulfone using potassium t-butoxide as base gave useful yields of 1,2-dimethylenecyclohexane. Under the same conditions, cycloheptanone, 3-methyl-2-butanone, and 2-butanone were converted to dienes. Remarkably, these reaction conditions converted acetophenone into p-terphenyl (10%) and (E)-1,4-diphenyl-3-penten-1-one (44%). Propiophenone was converted to 2'-methyl-p-terphenyl (61%). Using alpha-tetralone produced 1-methynaphthalene and naphthalene. No reaction took place with beta-tetralone. Using diethyl sulfone with alpha-tetralone lead to pure naphthalene. Condensation of isobutyraldehyde and dimethyl sulfone using potassium t-butoxide gave isoprene in low yield. Using benzaldehyde and benzyl phenyl sulfone in N,N-dimethylacetamide gave 1,2-diphenyl-1-phenylsulfonylethylene, N,N-dimethylcinnamide, and a complex condensation product. Only 1,2-diphenyl-1-phenylsulfonylethylene was obtained when the solvent was THF. PMID:16408963

  20. Using condenser performance measurements to optimize condenser cleaning

    SciTech Connect

    Wolff, P.J.; March, A.; Pearson, H.S.

    1996-05-01

    Because plant personnel perform condenser monitoring primarily to determine cleaning schedules, the accuracy and repeatability of a technique should be viewed within the context of a condenser cleaning schedule. Lower accuracy is acceptable if the cleaning schedule arising from that system is identical to a cleaning schedule arising from a technique with higher accuracy. Three condenser performance monitors were implemented and compared within the context of a condenser cleaning schedule to determine the relative advantages of different condenser monitoring techniques. These systems include a novel on-line system that consists of an electromagnetic flowmeter and an RTD mounted in a compact waterproof cylinder, an overall on-line system, and routine plant tests. The fouling measurements from each system are used in an optimization program which automatically computes a cleaning schedule that minitrack the combined cost of cleaning and the cost of increased fuel consumption caused by condenser fouling. The cleaning schedules resulting from each system`s measurements are compared. The optimization routine is also used to evaluate the sensitivity of optimal cleaning schedules to fouling rate and of the cost in dollars for non-optimal cleaning.

  1. Hierarchical condensation near phase equilibrium

    NASA Astrophysics Data System (ADS)

    Olemskoi, A. I.; Yushchenko, O. V.; Borisyuk, V. N.; Zhilenko, T. I.; Kosminska, Yu. O.; Perekrestov, V. I.

    2012-06-01

    A novel mechanism of new phase formation is studied both experimentally and theoretically in the example of quasi-equilibrium stationary condensation in an ion-plasma sputterer. Copper condensates are obtained to demonstrate that a specific network structure is formed as a result of self-assembly in the course of deposition. The fractal pattern related is inherent in the phenomena of diffusion limited aggregation. Condensate nuclei are shown to form statistical ensemble of hierarchically subordinated objects distributed in ultrametric space. The Langevin equation and the Fokker-Planck equation related are found to describe stationary distribution of thermodynamic potential variations at condensation. Time dependence of the formation probability of branching structures is found to clarify the experimental situation.

  2. Nonequilibrium thermodynamics of wealth condensation

    NASA Astrophysics Data System (ADS)

    Braun, Dieter

    2006-09-01

    We analyze wealth condensation for a wide class of stochastic economy models on the basis of the economic analog of thermodynamic potentials, termed transfer potentials. The economy model is based on three common transfers modes of wealth: random transfer, profit proportional to wealth and motivation of poor agents to work harder. The economies never reach steady state. Wealth condensation is the result of stochastic tunneling through a metastable transfer potential. In accordance with reality, both wealth and income distribution transiently show Pareto tails for high-income subjects. For metastable transfer potentials, exponential wealth condensation is a robust feature. For example with 10% annual profit 1% of the population owns 50% of the wealth after 50 years. The time to reach such a strong wealth condensation is a hyperbolic function of the annual profit rate.

  3. Flow Boiling and Condensation Experiment

    NASA Video Gallery

    The Flow Boiling and Condensation Experiment is another investigation that examines the flow of a mixture of liquids and the vapors they produce when in contact with hot space system equipment. Coo...

  4. Synthesis, double-helix formation, and higher-assembly formation of chiral polycyclic aromatic compounds: conceptual development of polyketide aldol synthesis.

    PubMed

    Yamaguchi, Masahiko; Shigeno, Masanori; Saito, Nozomi; Yamamoto, Koji

    2014-02-01

    Polycyclic aromatic compounds are an important group of substances in chemistry, and the study of their properties is a subject of interest in the development of drugs and materials. We have been conducting studies to develop chiral polycyclic aromatic compounds, i.e., helicenes and equatorenes. These helical molecules showed notable aggregate-forming properties and the capability for chiral recognition exerted by noncovalent bond interactions, which were not observed in compounds with central chirality. Homo- and hetero-double-helix-forming helicene oligomers were developed, and the latter self-assembled to form gels and vesicles. In this article, we describe such hierarchical studies of polycyclic aromatic compounds, which were started from polyketide aldol synthesis.

  5. Controlling condensation and frost growth with chemical micropatterns.

    PubMed

    Boreyko, Jonathan B; Hansen, Ryan R; Murphy, Kevin R; Nath, Saurabh; Retterer, Scott T; Collier, C Patrick

    2016-01-01

    In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events. PMID:26796663

  6. Controlling condensation and frost growth with chemical micropatterns.

    PubMed

    Boreyko, Jonathan B; Hansen, Ryan R; Murphy, Kevin R; Nath, Saurabh; Retterer, Scott T; Collier, C Patrick

    2016-01-22

    In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events.

  7. Functionalization of arrays of silica nanochannels by post-condensation.

    PubMed

    Zucchetto, N; Brühwiler, D

    2016-09-28

    Functionalized arrays of silica nanochannels (ASNCs) were prepared by post-condensation of amino-functional alkoxysilanes (NH-silanes). The method of post-condensation combines postsynthetic grafting and co-condensation - the classical pathways for the functionalization of mesoporous silica - to afford a convenient one-pot reaction in aqueous medium. The structure of the NH-silanes determines the distribution of the surface-bound groups in the ASNCs. Accumulation at the channel entrances was observed by confocal laser scanning microscopy in the case of sterically hindered NH-silanes, whereas smaller NH-silanes led to a more uniform distribution. In all cases, the channels remained accessible for additional postsynthetic treatment or introduction of guests after extraction of the structure-directing agent. The particle size and morphology, as well as the pore size and the degree of ordering of the amino-functionalized ASNCs were comparable to pristine ASNCs. PMID:27545508

  8. Controlling condensation and frost growth with chemical micropatterns

    NASA Astrophysics Data System (ADS)

    Boreyko, Jonathan B.; Hansen, Ryan R.; Murphy, Kevin R.; Nath, Saurabh; Retterer, Scott T.; Collier, C. Patrick

    2016-01-01

    In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events.

  9. Controlling condensation and frost growth with chemical micropatterns

    DOE PAGESBeta

    Boreyko, Jonathan B.; Hansen, Ryan R.; Murphy, Kevin R.; Nath, Saurabh; Retterer, Scott T.; Collier, C. Patrick

    2016-01-22

    Frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of frost across the population of supercooled condensate. Here, we demonstrate that when the nucleation sites for supercooled condensate are properly controlled with chemical micropatterns, the speed of frost growth can be slowed and even halted entirely. This stoppage of frost growth is attributed to the large interdroplet separation between condensate upon the onset ofmore » freezing, which was controlled by the pitch of the chemical patterns and by deliberately triggering an early freezing event. Lastly, these findings reveal that frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and/or temporally control the onset of freezing events.« less

  10. Controlling condensation and frost growth with chemical micropatterns

    PubMed Central

    Boreyko, Jonathan B.; Hansen, Ryan R.; Murphy, Kevin R.; Nath, Saurabh; Retterer, Scott T.; Collier, C. Patrick

    2016-01-01

    In-plane frost growth on chilled hydrophobic surfaces is an inter-droplet phenomenon, where frozen droplets harvest water from neighboring supercooled liquid droplets to grow ice bridges that propagate across the surface in a chain reaction. To date, no surface has been able to passively prevent the in-plane growth of ice bridges across the population of supercooled condensate. Here, we demonstrate that when the separation between adjacent nucleation sites for supercooled condensate is properly controlled with chemical micropatterns prior to freezing, inter-droplet ice bridging can be slowed and even halted entirely. Since the edge-to-edge separation between adjacent supercooled droplets decreases with growth time, deliberately triggering an early freezing event to minimize the size of nascent condensation was also necessary. These findings reveal that inter-droplet frost growth can be passively suppressed by designing surfaces to spatially control nucleation sites and by temporally controlling the onset of freezing events. PMID:26796663

  11. Rapid Drop Dynamics During Superhydrophobic Condensation

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Boreyko, Jonathan; Chen, Chuan-Hua

    2008-11-01

    Rapid drop motion is observed on superhydrophobic surfaces during condensation; condensate drops with diameter of order 10 μm can move at above 100G and 0.1 m/s. When water vapor condenses on a horizontal superhydrophobic surface, condensate drops move in a seemingly random direction. The observed motion is attributed to the energy released through coalescence of neighboring condensate drops. A scaling analysis captured the initial acceleration and terminal velocity. Our work is a step forward in understanding the dynamics of superhydrophobic condensation occurring in both natural water-repellant plants and engineered dropwise condensers.

  12. Condensation of anhydrides or dicarboxylic acids with compounds containing active methylene groups. Part 19: Condensation of phthalic and substituted phthalic anhydrides with benzoylacetic ester

    NASA Technical Reports Server (NTRS)

    Rotberg, Y. T.; Oshkaya, V. P.

    1985-01-01

    Phthalylbenzoylacetic ester and its nitro and halogen derivatives were prepared through condensation of phthalic anhydride, nitrophthalic anhydride, and phthalic halide anhydride with benzoylacetic ester in a solution of acetic anhydride and triethylamine. The condensation of hemipinic acid anhydride proceeds similarly, but under more drastic conditions. Derivatives of indan-1,3-dione are also formed, with a small yield, in the reaction of nitrophthalic anhydrides with benzoylacetic ester in the presence of increased quantities of triethylamine.

  13. Chemical transformations during rectification of products of hydroformylation of propylene

    SciTech Connect

    Kuz'mina, L.S.; Maiorova, L.V.; Kharisov, M.A.

    1988-09-10

    The occurrence of reactions related to losses of the target products, aldehydes and alcohols, was established in continuous rectification of the products of hydroformylation of propylene. The sections of the zone of primary occurrence of the reactions of aldol condensation, formation of acetals, and esterification of butyl alcohols with butyric acids were determined in the rectification column. It was shown that with increase in temperature in the rectification column still the degree of aldehyde and alcohol conversion in the overall rectification system decreases with respect to aldol condensation and acetal formation, while increasing with respect to alcohol esterification.

  14. Polariton condensates at room temperature

    NASA Astrophysics Data System (ADS)

    Guillet, Thierry; Brimont, Christelle

    2016-10-01

    We review the recent developments of the polariton physics in microcavities featuring the exciton-photon strong coupling at room temperature, and leading to the achievement of room-temperature polariton condensates. Such cavities embed active layers with robust excitons that present a large binding energy and a large oscillator strength, i.e. wide bandgap inorganic or organic semiconductors, or organic molecules. These various systems are compared, in terms of figures of merit and of common features related to their strong oscillator strength. The various demonstrations of polariton laser are compared, as well as their condensation phase diagrams. The room-temperature operation indeed allows a detailed investigation of the thermodynamic and out-of-equilibrium regimes of the condensation process. The crucial role of the spatial dynamics of the condensate formation is discussed, as well as the debated issue of the mechanism of stimulated relaxation from the reservoir to the condensate under non-resonant excitation. Finally the prospects of polariton devices are presented.

  15. Condensation modes in magnetized plasmas

    NASA Technical Reports Server (NTRS)

    An, Chang-Hyuk

    1986-01-01

    Condensation modes in magnetized cylindrical plasmas, with concentration on how magnetic field affects the stability were studied. It is found that the effects of magnetic field (shear, twist, and strength) on the condensation modes are different depending on the wave vector. For modes whose wave vector is not perpendicular to magnetic field lines the plasma motion is mainly along the field lines; the effects of magnetic field on the modes are negligible except on the heat flow parallel to the field line. For a mode which is localized near a surface where the wave vector is perpendicular to the field line, the plasma moves perpendicular to the line carrying the field line into the condensed region; magnetic field affects the mode by building up magnetic pressure in the condensed region. The stability of condensation modes strongly depends on how density and temperature vary with field twist. The stable nature of global quiescent prominence magnetic configurations implies that prominences form for low field twist for which ideal MHD modes are stable; plasma temperature should increase with field twist for stable prominence formation.

  16. On the onset of surface condensation: formation and transition mechanisms of condensation mode

    PubMed Central

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-01-01

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the ‘classical hypotheses’ of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation. PMID:27481071

  17. On the onset of surface condensation: formation and transition mechanisms of condensation mode

    NASA Astrophysics Data System (ADS)

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-08-01

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the ‘classical hypotheses’ of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation.

  18. On the onset of surface condensation: formation and transition mechanisms of condensation mode.

    PubMed

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-08-02

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the 'classical hypotheses' of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation.

  19. On the onset of surface condensation: formation and transition mechanisms of condensation mode.

    PubMed

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-01-01

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the 'classical hypotheses' of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation. PMID:27481071

  20. Spacecraft Crew Cabin Condensation Control

    NASA Technical Reports Server (NTRS)

    Carrillo, Laurie Y.; Rickman, Steven L.; Ungar, Eugene K.

    2013-01-01

    A report discusses a new technique to prevent condensation on the cabin walls of manned spacecraft exposed to the cold environment of space, as such condensation could lead to free water in the cabin. This could facilitate the growth of mold and bacteria, and could lead to oxidation and weakening of the cabin wall. This condensation control technique employs a passive method that uses spacecraft waste heat as the primary wallheating mechanism. A network of heat pipes is bonded to the crew cabin pressure vessel, as well as the pipes to each other, in order to provide for efficient heat transfer to the cabin walls and from one heat pipe to another. When properly sized, the heat-pipe network can maintain the crew cabin walls at a nearly uniform temperature. It can also accept and distribute spacecraft waste heat to maintain the pressure vessel above dew point.

  1. Condensed hydrogen for thermonuclear fusion

    SciTech Connect

    Kucheyev, S. O.; Hamza, A. V.

    2010-11-15

    Inertial confinement fusion (ICF) power, in either pure fusion or fission-fusion hybrid reactors, is a possible solution for future world's energy demands. Formation of uniform layers of a condensed hydrogen fuel in ICF targets has been a long standing materials physics challenge. Here, we review the progress in this field. After a brief discussion of the major ICF target designs and the basic properties of condensed hydrogens, we review both liquid and solid layering methods, physical mechanisms causing layer nonuniformity, growth of hydrogen single crystals, attempts to prepare amorphous and nanostructured hydrogens, and mechanical deformation behavior. Emphasis is given to current challenges defining future research areas in the field of condensed hydrogens for fusion energy applications.

  2. Condensed astatine: monatomic and metallic.

    PubMed

    Hermann, Andreas; Hoffmann, Roald; Ashcroft, N W

    2013-09-13

    The condensed matter properties of the nominal terminating element of the halogen group with atomic number 85, astatine, are as yet unknown. In the intervening more than 70 years since its discovery significant advances have been made in substrate cooling and the other techniques necessary for the production of the element to the point where we might now enquire about the key properties astatine might have if it attained a condensed phase. This subject is addressed here using density functional theory and structural selection methods, with an accounting for relativistic physics that is essential. Condensed astatine is predicted to be quite different in fascinating ways from iodine, being already at 1 atm a metal, and monatomic at that, and possibly a superconductor (as is dense iodine). PMID:24074111

  3. Condensed astatine: monatomic and metallic.

    PubMed

    Hermann, Andreas; Hoffmann, Roald; Ashcroft, N W

    2013-09-13

    The condensed matter properties of the nominal terminating element of the halogen group with atomic number 85, astatine, are as yet unknown. In the intervening more than 70 years since its discovery significant advances have been made in substrate cooling and the other techniques necessary for the production of the element to the point where we might now enquire about the key properties astatine might have if it attained a condensed phase. This subject is addressed here using density functional theory and structural selection methods, with an accounting for relativistic physics that is essential. Condensed astatine is predicted to be quite different in fascinating ways from iodine, being already at 1 atm a metal, and monatomic at that, and possibly a superconductor (as is dense iodine).

  4. Condensed Astatine: Monatomic and Metallic

    NASA Astrophysics Data System (ADS)

    Hermann, Andreas; Hoffmann, Roald; Ashcroft, N. W.

    2013-09-01

    The condensed matter properties of the nominal terminating element of the halogen group with atomic number 85, astatine, are as yet unknown. In the intervening more than 70 years since its discovery significant advances have been made in substrate cooling and the other techniques necessary for the production of the element to the point where we might now enquire about the key properties astatine might have if it attained a condensed phase. This subject is addressed here using density functional theory and structural selection methods, with an accounting for relativistic physics that is essential. Condensed astatine is predicted to be quite different in fascinating ways from iodine, being already at 1 atm a metal, and monatomic at that, and possibly a superconductor (as is dense iodine).

  5. Introduction. Cosmology meets condensed matter.

    PubMed

    Kibble, T W B; Pickett, G R

    2008-08-28

    At first sight, low-temperature condensed-matter physics and early Universe cosmology seem worlds apart. Yet, in the last few years a remarkable synergy has developed between the two. It has emerged that, in terms of their mathematical description, there are surprisingly close parallels between them. This interplay has been the subject of a very successful European Science Foundation (ESF) programme entitled COSLAB ('Cosmology in the Laboratory') that ran from 2001 to 2006, itself built on an earlier ESF network called TOPDEF ('Topological Defects: Non-equilibrium Field Theory in Particle Physics, Condensed Matter and Cosmology'). The articles presented in this issue of Philosophical Transactions A are based on talks given at the Royal Society Discussion Meeting 'Cosmology meets condensed matter', held on 28 and 29 January 2008. Many of the speakers had participated earlier in the COSLAB programme, but the strength of the field is illustrated by the presence also of quite a few new participants.

  6. Gravity Effects in Condensing and Evaporating Films

    NASA Technical Reports Server (NTRS)

    Hermanson, J. C.; Som, S. M.; Allen, J. S.; Pedersen, P. C.

    2004-01-01

    A general overview of gravity effects in condensing and evaporating films is presented. The topics include: 1) Research Overview; 2) NASA Recognizes Critical Need for Condensation & Evaporation Research to Enable Human Exploration of Space; 3) Condensation and Evaporation Research in Reduced Gravity is Enabling for AHST Technology Needs; 4) Differing Role of Surface Tension on Condensing/Evaporating Film Stability; 5) Fluid Mechanisms in Condensing and Evaporating Films in Reduced Gravity; 6) Research Plan; 7) Experimental Configurations for Condensing Films; 8) Laboratory Condensation Test Cell; 9) Aircraft Experiment; 10) Condensation Study Current Test Conditions; 11) Diagnostics; 12) Shadowgraph Images of Condensing n- pentane Film in Unstable (-1g) Configuration; 13) Condensing n-Pentane Film in Normal Gravity (-1g) at Constant Pressure; 14) Condensing n-Pentane Film in Normal Gravity (-1g) with Cyclic Pressure; 15) Non-condensing Pumped Film in Normal Gravity (-1g); 16) Heat Transfer Coefficient in Developing, Unstable Condensing Film in Normal Gravity; 17) Heat Transfer for Unsteady Condensing Film (-1g); 18) Ultrasound Measurement of Film Thickness N-pentane Film, Stable (+1g) Configuration; and 19) Ultrasound Measurement of Film Thickness N-pentane Film, Unstable (-1g) Configuration.

  7. Catalytic Routes for the Conversion of Biomass Derivatives to Hydrocarbons and/or Platform Chemicals

    SciTech Connect

    Silks, III, Louis A.

    2015-10-07

    Unprotected carbohydrates were reacted in amine-catalyzed cascade reactions with various methyl ketones to give a direct access to C-glycosides by an operationally simple protocol. As the reaction mechanism,an aldol condensation followed by an intramolecular conjugate addition is assumed.

  8. Turbulent mixing condensation nucleus counter

    NASA Astrophysics Data System (ADS)

    Mavliev, Rashid

    The construction and operating principles of the Turbulent Mixing Condensation Nucleus Counter (TM CNC) are described. Estimations based on the semiempirical theory of turbulent jets and the classical theory of nucleation and growth show the possibility of detecting particles as small as 2.5 nm without the interference of homogeneous nucleation. This conclusion was confirmed experimentally during the International Workshop on Intercomparison of Condensation Nuclei and Aerosol Particle Counters (Vienna, Austria). Number concentration, measured by the Turbulent Mixing CNC and other participating instruments, is found to be essentially equal.

  9. Condensation in Titan's lower atmosphere

    NASA Astrophysics Data System (ADS)

    Lavvas, P.; Griffith, C. A.; Yelle, R. V.

    2011-10-01

    We present a self-consistent description of Titan's aerosols-clouds-gases system and compare our results with the optical properties retrieved from measurements made by the Descent Imager / Spectral Radiometer (DISR) experiment on the Huygens probe [4]. Our calculations include the condensation of methane, ethane and hydrogen cyanide on photochemical aerosols produced in the thermosphere. Our results suggest that the two distinct extinction layers observed by DISR below 80 km are produced by HCN and methane condensation, respectively, while for the Huygens' equatorial conditions simulated here, the contribution of ethane clouds to the total opacity is negligible

  10. Adiabatic preparation of Floquet condensates

    NASA Astrophysics Data System (ADS)

    Heinisch, Christoph; Holthaus, Martin

    2016-10-01

    We argue that a Bose-Einstein condensate can be transformed into a Floquet condensate, that is, into a periodically time-dependent many-particle state possessing the coherence properties of a mesoscopically occupied single-particle Floquet state. Our reasoning is based on the observation that the denseness of the many-body system's quasienergy spectrum does not necessarily obstruct effectively adiabatic transport. Employing the idealized model of a driven bosonic Josephson junction, we demonstrate that only a small amount of Floquet entropy is generated when a driving force with judiciously chosen frequency and maximum amplitude is turned on smoothly.

  11. The prebiotic synthesis of deoxythymidine oligonucleotides. II - Comparison of condensing agents

    NASA Technical Reports Server (NTRS)

    Odom, D. G.; Brady, J. T.

    1975-01-01

    A reaction which oligomerizes nucleotides under possible prebiotic conditions has been characterized. Nucleoside monophosphate in the presence of cyanamide at acid pH condenses to form dithymidine pyrophosphate and phosphodiester bonded compounds. Imidazole compounds and activated precursors such as nucleoside triphosphate are not necessary for this oligomerization reaction which produces primarily cyclic oligonucleotides.

  12. Diastereoselective one-pot Knoevenagel condensation/Corey-Chaykovsky cyclopropanation.

    PubMed

    Clemens, Jeremy J; Asgian, Juliana L; Busch, Brett B; Coon, Timothy; Ernst, Justin; Kaljevic, Leonard; Krenitsky, Paul J; Neubert, Timothy D; Schweiger, Edwin J; Termin, Andreas; Stamos, Dean

    2013-01-18

    Efforts to substitute the cyclopropane ring in a series of aryl cyclopropylnitriles led to the discovery of an operationally simple one-pot method for Knoevenagel condensation and subsequent Corey-Chaykovsky cyclopropanation giving diastereomerically pure products as a racemic mixture of enantiomers. Method development and results for variably substituted aryl acetonitriles and aldehydes in the reaction are reported. A concise synthesis of (±)-bicifadine in two steps is provided to demonstrate the utility of the method. PMID:23252964

  13. Wettability modified nanoporous ceramic membrane for simultaneous residual heat and condensate recovery

    PubMed Central

    Hu, H. W.; Tang, G. H.; Niu, D.

    2016-01-01

    Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed. PMID:27270997

  14. Wettability modified nanoporous ceramic membrane for simultaneous residual heat and condensate recovery

    NASA Astrophysics Data System (ADS)

    Hu, H. W.; Tang, G. H.; Niu, D.

    2016-06-01

    Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed.

  15. Influence of iodine on the treatment of spacecraft humidity condensate to produce potable water

    NASA Technical Reports Server (NTRS)

    Symons, James M.; Muckle, Susan V.

    1990-01-01

    Several compounds in the ersatz humidity condensate do react with iodine to form iodine-substituted organic compounds (TOI), most notably phenol, acetaldehyde, ethanol, and sodium formate. Iodination of the ersatz humidity condensate produced 3.0 to 3.5 mg/L of TOI within 24 hours. The TOI that was produced by the passage of the ersatz humidity condensate through the first iodinated resin (IR) in the adsorption system was removed by the granular activated carbon that followed. TOI detected in the final effluent was formed by the reaction of the non-adsorbable condensate compounds with the final IR in the treatment series. The activated carbon bed series in the adsorption system performed poorly in its removal of TOC. The rapid breakthrough of TOC was not surprising, as the ersatz humidity condensate contained several highly soluble organic compounds, alcohols and organic acids.

  16. Wettability modified nanoporous ceramic membrane for simultaneous residual heat and condensate recovery.

    PubMed

    Hu, H W; Tang, G H; Niu, D

    2016-01-01

    Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed. PMID:27270997

  17. Wettability modified nanoporous ceramic membrane for simultaneous residual heat and condensate recovery.

    PubMed

    Hu, H W; Tang, G H; Niu, D

    2016-06-07

    Recovery of both latent heat and condensate from boiler flue gas is significant for improving boiler efficiency and water conservation. The condensation experiments are carried out to investigate the simultaneous heat and mass transfer across the nanoporous ceramic membranes (NPCMs) which are treated to be hydrophilic and hydrophobic surfaces using the semicontinuous supercritical reactions. The effects of typical parameters including coolant flow rate, vapor/nitrogen gas mixture temperature, water vapor volume fraction and transmembrane pressure on heat and mass transfer performance are studied. The experimental results show that the hydrophilic NPCM exhibits higher performances of condensation heat transfer and condensate recovery. However, the hydrophobic modification results in remarkable degradation of heat and condensate recovery from the mixture. Molecular dynamics simulations are conducted to establish a hydrophilic/hydrophobic nanopore/water liquid system, and the infiltration characteristics of the single hydrophilic/hydrophobic nanopore is revealed.

  18. Basic Program Plan. Condensed Version.

    ERIC Educational Resources Information Center

    Stanford Univ., CA. Stanford Center for Research and Development in Teaching.

    This condensed version of the Basic Program Plan for the Stanford Center for Research and Development in Teaching (SCDRT) outlines the proposed plans of substantive programs over the next several years (beginning December 1, 1972). Information on projected costs and the Center's institutional capabilities for administering, reviewing, and…

  19. Approaching Bose-Einstein Condensation

    ERIC Educational Resources Information Center

    Ferrari, Loris

    2011-01-01

    Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…

  20. Condensing Algebra for Technical Mathematics.

    ERIC Educational Resources Information Center

    Greenfield, Donald R.

    Twenty Algebra-Packets (A-PAKS) were developed by the investigator for technical education students at the community college level. Each packet contained a statement of rationale, learning objectives, performance activities, performance test, and performance test answer key. The A-PAKS condensed the usual sixteen weeks of algebra into a six-week…

  1. Unfolding Reactions.

    ERIC Educational Resources Information Center

    Streitberger, H. Eric

    1997-01-01

    Describes how students use paper-strip molecules in hands-on activities to show the synthesis of larger organic molecules from smaller molecules. Focuses initially on condensation molecules involving the functional groups in alcohol and carboxylic acids. (DDR)

  2. N-cyanoimidazole and diimidazole imine: water-soluble condensing agents for the formation of the phosphodiester bond

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Huang, C. H.; Hagan, W. J. Jr

    1989-01-01

    The reaction of BrCN with imidazole results in the formation of N-cyanoimidazole and diimidazole imine. These compounds were shown to be useful condensing agents for the formation of the phosphodiester bound in aqueous solution.

  3. Condensation during Titan's Polar Winter

    NASA Astrophysics Data System (ADS)

    de Kok, Remco; Irwin, P. G.; Teanby, N. A.; Fletcher, L. N.; Howett, C. J.; Calcutt, S. B.; Bowles, N. E.; Taylor, F. W.

    2007-10-01

    Titan is currently experiencing winter in its northern hemisphere and the lower atmosphere of its north polar region has been in prolonged darkness since the solstice in October 2002. As a result, the north polar region is currently characterised by cold stratospheric temperatures and there is enrichment of trace gases due to downward atmospheric motion (e.g. Teanby et al., Icarus 181 pp. 243-255, 2006). These conditions make the polar winter very suitable for cloud formation in the stratosphere. A simple transport and condensation model has been made to explore condensation processes in Titan's northern stratosphere. In the model, the atmosphere is advected downwards and clouds are formed as the saturation pressure of various gases is reached. Upper limits of the gases C4N2 and propionitrile (C2H5CN) were determined from Cassini Composite Infrared Spectrometer data to assess scenarios of chemical disequilibrium where the gas phase is far less abundant than the solid phase. The upper limit for C4N2 is 9e-9, which discounts the massive C4N2 build-up in the polar winter proposed by Samuelson et al. (PSS 45, pp. 941-948, 1997) to explain the observed C4N2 cloud at the Voyager epoch. The propionitrile upper limit is 8e-9, which is several orders of magnitude less than needed to create the condensate feature at 220 cm-1 of Khanna (Icarus 177, pp. 116-121) and de Kok et al. (Icarus, in press), assuming it is propionitrile ice, under the steady-state conditions explored by the aformentioned model. HCN ice seems to play an important role in the formation of a massive polar cloud (Haze B in de Kok et al., Icarus, in press), because of the unavailability of sufficient condensable gas other than HCN (and possibly HC3N) to produce the condensate features seen in far-infrared spectra at 220 cm-1.

  4. The effect of imidazole, cyanamide, and polyornithine on the condensation of nucleotides in aqueous systems.

    NASA Technical Reports Server (NTRS)

    Ibanez, J.; Kimball, A. P.; Oro, J.

    1971-01-01

    Development of two models for the condensation of nucleotides under possibly prebiotic conditions. In the first of these models this type of reaction is promoted by the presence of imidazole and substituted imidazole compounds. The second model involves the condensation of mononucleotides with cyanamide in the presence and absence of a prototemplate such as polyornithine. A tentative mechanism for the role of imidazole catalysis in phosphodiester bond formation between adjacent TMP molecules is suggested.

  5. Secondary decomposition reactions in nitramines

    NASA Astrophysics Data System (ADS)

    Schweigert, Igor

    Thermal decomposition of nitramines is known to proceed via multiple, competing reaction branches, some of which are triggered by secondary reactions between initial decomposition products and unreacted nitramine molecules. Better mechanistic understanding of these secondary reactions is needed to enable extrapolations of measured rates to higher temperatures and pressures relevant to shock ignition. I will present density functional theory (DFT) based simulations of nitramines that aim to re-evaluate known elementary mechanisms and seek alternative pathways in the gas and condensed phases. This work was supported by the Office of Naval Research, both directly and through the Naval Research Laboratory.

  6. Proceedings: 2000 Workshop on Condensate Polishing

    SciTech Connect

    2001-06-01

    Condensate polishing maintains control of impurities in the nuclear power plant and allows the unit to operate more reliably. This report presents proceedings of EPRI's 2000 Workshop on Condensate Polishing, where 30 papers were presented on current issues and utility experience involving condensate polishing at both pressurized water reactor (PWR) and boiling water reactor (BWR) plants.

  7. Film condensation in a horizontal rectangular duct

    NASA Technical Reports Server (NTRS)

    Lu, Qing; Suryanarayana, N. V.

    1992-01-01

    Condensation heat transfer in an annular flow regime with and without interfacial waves was experimentally investigated. The study included measurements of heat transfer rate with condensation of vapor flowing inside a horizontal rectangular duct and experiments on the initiation of interfacial waves in condensation, and adiabatic air-liquid flow. An analytical model for the condensation was developed to predict condensate film thickness and heat transfer coefficients. Some conclusions drawn from the study are that the condensate film thickness was very thin (less than 0.6 mm). The average heat transfer coefficient increased with increasing the inlet vapor velocity. The local heat transfer coefficient decreased with the axial distance of the condensing surface, with the largest change at the leading edge of the test section. The interfacial shear stress, which consisted of the momentum shear stress and the adiabatic shear stress, appeared to have a significant effect on the heat transfer coefficients. In the experiment, the condensate flow along the condensing surface experienced a smooth flow, a two-dimensional wavy flow, and a three-dimensional wavy flow. In the condensation experiment, the local wave length decreased with the axial distance of the condensing surface and the average wave length decreased with increasing inlet vapor velocity, while the wave speed increased with increasing vapor velocity. The heat transfer measurements are reliable. And, the ultrasonic technique was effective for measuring the condensate film thickness when the surface was smooth or had waves of small amplitude.

  8. Femtosecond quantum control of molecular dynamics in the condensed phase.

    PubMed

    Nuernberger, Patrick; Vogt, Gerhard; Brixner, Tobias; Gerber, Gustav

    2007-05-28

    We review the progress in controlling quantum dynamical processes in the condensed phase with femtosecond laser pulses. Due to its high particle density the condensed phase has both high relevance and appeal for chemical synthesis. Thus, in recent years different methods have been developed to manipulate the dynamics of condensed-phase systems by changing one or multiple laser pulse parameters. Single-parameter control is often achieved by variation of the excitation pulse's wavelength, its linear chirp or its temporal subpulse separation in case of pulse sequences. Multiparameter control schemes are more flexible and provide a much larger parameter space for an optimal solution. This is realized in adaptive femtosecond quantum control, in which the optimal solution is iteratively obtained through the combination of an experimental feedback signal and an automated learning algorithm. Several experiments are presented that illustrate the different control concepts and highlight their broad applicability. These fascinating achievements show the continuous progress on the way towards the control of complex quantum reactions in the condensed phase.

  9. Condensed matter analogues of cosmology

    NASA Astrophysics Data System (ADS)

    Kibble, Tom; Srivastava, Ajit

    2013-10-01

    It is always exciting when developments in one branch of physics turn out to have relevance in a quite different branch. It would be hard to find two branches farther apart in terms of energy scales than early-universe cosmology and low-temperature condensed matter physics. Nevertheless ideas about the formation of topological defects during rapid phase transitions that originated in the context of the very early universe have proved remarkably fruitful when applied to a variety of condensed matter systems. The mathematical frameworks for describing these systems can be very similar. This interconnection has led to a deeper understanding of the phenomena in condensed matter systems utilizing ideas from cosmology. At the same time, one can view these condensed matter analogues as providing, at least in a limited sense, experimental access to the phenomena of the early universe for which no direct probe is possible. As this special issue well illustrates, this remains a dynamic and exciting field. The basic idea is that when a system goes through a rapid symmetry-breaking phase transition from a symmetric phase into one with spontaneously broken symmetry, the order parameter may make different choices in different regions, creating domains that when they meet can trap defects. The scale of those domains, and hence the density of defects, is constrained by the rate at which the system goes through the transition and the speed with which order parameter information propagates. This is what has come to be known as the Kibble-Zurek mechanism. The resultant scaling laws have now been tested in a considerable variety of different systems. The earliest experiments illustrating the analogy between cosmology and condensed matter were in liquid crystals, in particular on the isotropic-to-nematic transition, primarily because it is very easy to induce the phase transition (typically at room temperature) and to image precisely what is going on. This field remains one of the

  10. Anderson and Condensed Matter Physics

    NASA Astrophysics Data System (ADS)

    Ramakrishnan, T. V.

    The legacy of P. W. Anderson, perhaps the most fertile and influential condensed matter physicist of the second half of the twentieth century, is briefly mentioned here. I note three pervasive values. They are: emergence with its constant tendency to surprise us and to stretch our imagination, the Baconian emphasis on the experimental moorings of modern science, and mechanism as the explanatory core. Out of his work, which is spread over more than six decades and in many ways has charted modern condensed matter physics, nearly a dozen seminal contributions, chosen idiosyncratically, are mentioned at the risk of leaving out many which may also have started subfields. Some of these are: antiferromagnestism and broken symmetry, superexchange and strong electron correlations, localization in disordered systems, gauge invariance and mass, and the resonating valence bond in magnetic systems as well as in high-temperature superconductivity...

  11. Wealth condensation in pareto macroeconomies.

    PubMed

    Burda, Z; Johnston, D; Jurkiewicz, J; Kamiński, M; Nowak, M A; Papp, G; Zahed, I

    2002-02-01

    We discuss a Pareto macroeconomy (a) in a closed system with fixed total wealth and (b) in an open system with average mean wealth, and compare our results to a similar analysis in a super-open system (c) with unbounded wealth [J.-P. Bouchaud and M. Mézard, Physica A 282, 536 (2000)]. Wealth condensation takes place in the social phase for closed and open economies, while it occurs in the liberal phase for super-open economies. In the first two cases, the condensation is related to a mechanism known from the balls-in-boxes model, while in the last case, to the nonintegrable tails of the Pareto distribution. For a closed macroeconomy in the social phase, we point to the emergence of a "corruption" phenomenon: a sizeable fraction of the total wealth is always amassed by a single individual.

  12. Wealth condensation in pareto macroeconomies

    NASA Astrophysics Data System (ADS)

    Burda, Z.; Johnston, D.; Jurkiewicz, J.; Kamiński, M.; Nowak, M. A.; Papp, G.; Zahed, I.

    2002-02-01

    We discuss a Pareto macroeconomy (a) in a closed system with fixed total wealth and (b) in an open system with average mean wealth, and compare our results to a similar analysis in a super-open system (c) with unbounded wealth [J.-P. Bouchaud and M. Mézard, Physica A 282, 536 (2000)]. Wealth condensation takes place in the social phase for closed and open economies, while it occurs in the liberal phase for super-open economies. In the first two cases, the condensation is related to a mechanism known from the balls-in-boxes model, while in the last case, to the nonintegrable tails of the Pareto distribution. For a closed macroeconomy in the social phase, we point to the emergence of a ``corruption'' phenomenon: a sizeable fraction of the total wealth is always amassed by a single individual.

  13. Spatial coherence of a polariton condensate.

    PubMed

    Deng, Hui; Solomon, Glenn S; Hey, Rudolf; Ploog, Klaus H; Yamamoto, Yoshihisa

    2007-09-21

    We perform Young's double-slit experiment to study the spatial coherence properties of a two-dimensional dynamic condensate of semiconductor microcavity polaritons. The coherence length of the system is measured as a function of the pump rate, which confirms a spontaneous buildup of macroscopic coherence in the condensed phase. An independent measurement reveals that the position and momentum uncertainty product of the condensate is close to the Heisenberg limit. An experimental realization of such a minimum uncertainty wave packet of the polariton condensate opens a door to coherent matter-wave phenomena such as Josephson oscillation, superfluidity, and solitons in solid state condensate systems.

  14. Atomistic modeling of dropwise condensation

    NASA Astrophysics Data System (ADS)

    Sikarwar, B. S.; Singh, P. L.; Muralidhar, K.; Khandekar, S.

    2016-05-01

    The basic aim of the atomistic modeling of condensation of water is to determine the size of the stable cluster and connect phenomena occurring at atomic scale to the macroscale. In this paper, a population balance model is described in terms of the rate equations to obtain the number density distribution of the resulting clusters. The residence time is taken to be large enough so that sufficient time is available for all the adatoms existing in vapor-phase to loose their latent heat and get condensed. The simulation assumes clusters of a given size to be formed from clusters of smaller sizes, but not by the disintegration of the larger clusters. The largest stable cluster size in the number density distribution is taken to be representative of the minimum drop radius formed in a dropwise condensation process. A numerical confirmation of this result against predictions based on a thermodynamic model has been obtained. Results show that the number density distribution is sensitive to the surface diffusion coefficient and the rate of vapor flux impinging on the substrate. The minimum drop radius increases with the diffusion coefficient and the impinging vapor flux; however, the dependence is weak. The minimum drop radius predicted from thermodynamic considerations matches the prediction of the cluster model, though the former does not take into account the effect of the surface properties on the nucleation phenomena. For a chemically passive surface, the diffusion coefficient and the residence time are dependent on the surface texture via the coefficient of friction. Thus, physical texturing provides a means of changing, within limits, the minimum drop radius. The study reveals that surface texturing at the scale of the minimum drop radius does not provide controllability of the macro-scale dropwise condensation at large timescales when a dynamic steady-state is reached.

  15. Condensation on Slippery Asymmetric Bumps

    NASA Astrophysics Data System (ADS)

    Park, Kyoo-Chul; Kim, Philseok; Aizenberg, Joanna

    Controlling dropwise condensation by designing surfaces that enable droplets to grow rapidly and be shed as quickly as possible is fundamental to water harvesting systems, thermal power generation, distillation towers, etc. However, cutting-edge approaches based on micro/nanoscale textures suffer from intrinsic trade-offs that make it difficult to optimize both growth and transport at once. Here we present a conceptually different design approach based on principles derived from Namib desert beetles, cacti, and pitcher plants that synergistically couples both aspects of condensation and outperforms other synthetic surfaces. Inspired by an unconventional interpretation of the role of the beetle's bump geometry in promoting condensation, we show how to maximize vapor diffusion flux at the apex of convex millimetric bumps by optimizing curvature and shape. Integrating this apex geometry with a widening slope analogous to cactus spines couples rapid drop growth with fast directional transport, by creating a free energy profile that drives the drop down the slope. This coupling is further enhanced by a slippery, pitcher plant-inspired coating that facilitates feedback between coalescence-driven growth and capillary-driven motion. We further observe an unprecedented six-fold higher exponent in growth rate and much faster shedding time compared to other surfaces. We envision that our fundamental understanding and rational design strategy can be applied to a wide range of phase change applications.

  16. Extreme-UV lithography condenser

    DOEpatents

    Sweatt, William C.; Sweeney, Donald W.; Shafer, David; McGuire, James

    2001-01-01

    Condenser system for use with a ringfield camera in projection lithography where the condenser includes a series of segments of a parent aspheric mirror having one foci at a quasi-point source of radiation and the other foci at the radius of a ringfield have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ringfield camera about one of the beams and fall onto the ringfield radius as a coincident image as an arc of the ringfield. The condenser has a set of correcting mirrors with one of the correcting mirrors of each set, or a mirror that is common to said sets of mirrors, from which the radiation emanates, is a concave mirror that is positioned to shape a beam segment having a chord angle of about 25 to 85 degrees into a second beam segment having a chord angle of about 0 to 60 degrees.

  17. Properties of fragmented repulsive condensates

    SciTech Connect

    Streltsov, Alexej I.; Cederbaum, Lorenz S.

    2005-06-15

    Repulsive Bose-Einstein condensates immersed into a double-well trap potential are studied within the framework of the recently introduced mean-field approach which allows for bosons to reside in several different orthonormal orbitals. In the case of a one-orbital mean-field theory (Gross-Pitaevskii) the ground state of the system reveals a bifurcation scenario at some critical values of the interparticle interaction and/or the number of particles. At about the same values of the parameters the two-orbital mean field predicts that the system becomes twofold fragmented. By applying the three-orbital mean field we verify numerically that for the double-well external potential studied here the overall best mean field is achieved with two orbitals. The variational principle minimizes the energy at a vanishing population of the third orbital. To discuss the energies needed to remove a boson from and the energies gained by adding a boson to the condensate, we introduce boson ionization potentials and boson affinities and relate them to the chemical potentials. The impact of the finite number of bosons in the condensate on these quantities is analyzed. We recall that within the framework of the multiorbital mean-field theory each fragment is characterized by its own chemical potential. Finally, the stability of fragmented states is discussed in terms of the boson transfer energy which is the energy needed to transfer a boson from one fragment to another.

  18. Process for gasifying carbonaceous material from a recycled condensate slurry

    DOEpatents

    Forney, Albert J.; Haynes, William P.

    1981-01-01

    Coal or other carbonaceous material is gasified by reaction with steam and oxygen in a manner to minimize the problems of effluent water stream disposal. The condensate water from the product gas is recycled to slurry the coal feed and the amount of additional water or steam added for cooling or heating is minimized and preferably kept to a level of about that required to react with the carbonaceous material in the gasification reaction. The gasification is performed in a pressurized fluidized bed with the coal fed in a water slurry and preheated or vaporized by indirect heat exchange contact with product gas and recycled steam. The carbonaceous material is conveyed in a gas-solid mixture from bottom to top of the pressurized fluidized bed gasifier with the solids removed from the product gas and recycled steam in a supported moving bed filter of the resulting carbonaceous char. Steam is condensed from the product gas and the condensate recycled to form a slurry with the feed coal carbonaceous particles.

  19. Condensation shocks in hypersonic nitrogen tunnels

    NASA Technical Reports Server (NTRS)

    Hudson, Susan T.; Griffith, Wayland C.; Lederer, Melissa; Ragsdale, William C.; Yanta, William J.

    1990-01-01

    Experimental observations and a theoretical model for the onset and disappearance of condensation are provided for hypersonic flows of pure nitrogen at M = 10, 14, and 18. A method for analyzing the thermodynamic and flow properties of a partially condensed mixture from known supply conditions and measured Pitot pressure yields the local static pressure and temperature, mass fraction of the nitrogen condensed, and the Mach number of the partially condensed flow based on frozen sound speed. The transition between partially condensed-supercooled flow is found to occur at 22-25 K isobaric supercooling with the corresponding mass fraction condensed being 12-14 percent over a range of two orders of magnitude in local static pressure. The heat released and vapor mass removed during condensation ultimately raise the local pressure and temperature and reduce the flow Mach number.

  20. Activated alkene dependent one-pot, three-component aza-Morita-Baylis-Hillman reaction of ferrocenealdehyde: synthesis of highly functionalized diverse ferrocene derivatives.

    PubMed

    Madhavan, Suchithra; Shanmugam, Ponnusamy

    2011-04-01

    Activated alkene dependent one-pot, three-component aza-Morita-Baylis-Hillman (aza-MBH) reaction of ferrocenealdehyde afforded simple aza-MBH adduct of ferrocenealdehyde, unusual piperidine, β-amino acid residue, and γ-ketoester derivatives of ferrocene in good yield. The synthetic protocol with MVK has led to an unexpected ferrocenyl piperidine derivative in an excellent yield via diastereoselective domino aza-Michael/double Aldol pathway. Plausible mechanisms for the formation of unusual products and diastereoselectivity have also been described. The products can be used for the concise synthesis of ferrocenyl nitrogen heterocycles and bioconjugates.

  1. Copper-catalyzed chlorination and condensation of acetylene and dichloroacetylene.

    PubMed

    Taylor, P H; Wehrmeier, A; Sidhu, S S; Lenoir, D; Schramm, K W; Kettrup, A

    2000-06-01

    The chlorination and condensation of acetylene at low temperatures is demonstrated using copper chlorides as chlorinated agents coated to model borosilicate surfaces. Experiments with and without both a chlorine source and borosilicate surfaces indicate the absence of gas-phase and gas-surface reactions. Chlorination and condensation occur only in the presence of the copper catalyst. C2 through C8 organic products were observed in the effluent; PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed that is consistent with the observed product distributions. Similar experiments with dichloroacetylene indicate greater reactivity in the absence of the copper catalyst. Reaction is observed in the gas-phase and in the presence of borosilicate surfaces at low temperatures. The formation of hexachlorobenzene is only observed in the presence of a copper catalyst. PCDD/F were only observed from extraction of the borosilicate surfaces. A global reaction model is proposed for the formation of hexachlorobenzene from dichloroacetylene. PMID:10789968

  2. Unraveling the Concerted Reaction Mechanism of the Noncatalyzed Mukaiyama Reaction between C,O,O-Tris(trimethylsilyl)ketene Acetal and Aldehydes Using Density Functional Theory.

    PubMed

    Hadj Mohamed, Slim; Trabelsi, Mahmoud; Champagne, Benoît

    2016-07-21

    The uncatalyzed Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes bearing alkyl, vinyl, and aromatic substituents has been studied theoretically using density functional theory with the M06-2X exchange-correlation functional. These DFT calculations mostly demonstrate that (i) the syn product is both kinetically and thermodynamically favored, (ii) the diastereoselectivity of the uncatalyzed reaction is larger than observed for the reaction catalyzed by HgI2 and it is inverted with respect to the latter, (iii) solvents with larger dielectric constants increase the activation barrier but reduce the diastereoselectivity, (iv) the concerted reaction is preferred over the stepwise reaction, and (v) the OSiMe3 group in geminal lowers the activation barrier and increases the energy of reaction. Analyzing the concerted mechanism unravels four types of cyclic transition states, two pro-anti and two pro-syn. Then, the relative energy of the most stable transition state of each type as well as of the corresponding anti and syn products shows that the syn reaction path is located at lower Gibbs enthalpy than the anti reaction path for all substituents.

  3. Io's Atmospheric Freeze-out Dynamics in the Presence of a Non-condensable Species

    SciTech Connect

    Moore, Chris H.; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.; Stewart, Benedicte D.; Walker, Andrew C.

    2008-12-31

    One dimensional direct simulation Monte Carlo (DSMC) simulations are used to examine the effect of a trace non-condensable species on the freeze-out dynamics of Io's sulfur dioxide sublimation atmosphere during eclipse and egress. Due to finite ballistic times, essentially no collapse occurs during the first 10 minutes of eclipse at altitudes above {approx}100 km, and hence immediately after ingress auroral emission morphology above 100 km should resemble that of the immediate pre-eclipse state. In the absence of a non-condensable species the sublimation SO2 atmosphere will freeze-out (collapse) during eclipse as the surface temperature drops. However, rapid collapse is prevented by the presence of even a small amount of a perfect non-condensable species due to the formation of a static diffusion layer several mean free paths thick near the surface. The higher the non-condensable mole fraction, the longer the collapse time. The effect of a weakly condensable gas species (non-zero sticking/reaction coefficient) was examined since real gas species may not be perfectly non-condensable at realistic surface temperatures. It is found that even a small sticking coefficient dramatically reduces the effect of the diffusion layer on the dynamics. If the sticking coefficient of the non-condensable exceeds {approx}0.25 the collapse dynamics are effectively the same as if there was no non-condensable present. This sensitivity results because the loss of non-condensable to the surface reduces the effective diffusion layer size and the formation of an effective diffusion layer requires that the layer be stationary which does not occur if the surface is a sink. As the surface temperature increases during egress from eclipse the sublimating SO2 gas pushes the non-condensable diffusion layer up to higher altitudes once it becomes dense enough to be collisional. This vertical species stratification should alter the auroral emissions after egress.

  4. Condensing efficiency of the truncated cone condenser and its comparison with the Winston cone condenser in terahertz region

    NASA Astrophysics Data System (ADS)

    Aoki, Makoto; Hiromoto, Norihisa

    2015-01-01

    The angle-dependent condensing efficiency of a truncated cone condenser (TCC) in the terahertz (THz) region has been examined by 2D ray tracing and 3D electromagnetic simulation. The condensing efficiency in the THz region is transferred to that in the optical region by theoretical dispersive reflection from a rough surface, and it is confirmed that the latter is consistent with the measured condensing efficiency in the optical region. Although the TCC has a gradual field of view (FOV) compared with the Winston cone condenser (WCC), we improved the steepness of the FOV by adding a baffle before the input aperture of the TCC. We also proved that the TCC has a high condensing efficiency at around normal incidence in comparison with the WCC in the THz region.

  5. CDW-Exciton Condensate Competition and a Condensate Driven Force

    NASA Astrophysics Data System (ADS)

    Özgün, Ege; Hakioğlu, Tuğrul

    2016-08-01

    We examine the competition between the charge-density wave (CDW) instability and the excitonic condensate (EC) in spatially separated layers of electrons and holes. The CDW and the EC order parameters (OPs), described by two different mechanisms and hence two different transition temperatures TcCDW and TcEC, are self-consistently coupled by a microscopic mean field theory. We discuss the results in our model specifically focusing on the transition-metal dichalcogenides which are considered as the most typical examples of strongly coupled CDW/EC systems with atomic layer separations where the electronic energy scales are large with the critical temperatures in the range TcEC ˜ TcCDW ˜ 100-200 K. An important consequence of this is that the excitonic energy gap, hence the condensed free energy, vary with the layer separation resulting in a new type of force FEC. We discuss the possibility of this force as the possible driver of the structural lattice deformation observed in some TMDCs with a particular attention on the 1T-TiSe2 below 200 K.

  6. Condensation on slippery asymmetric bumps

    NASA Astrophysics Data System (ADS)

    Park, Kyoo-Chul; Kim, Philseok; Grinthal, Alison; He, Neil; Fox, David; Weaver, James C.; Aizenberg, Joanna

    2016-03-01

    Controlling dropwise condensation is fundamental to water-harvesting systems, desalination, thermal power generation, air conditioning, distillation towers, and numerous other applications. For any of these, it is essential to design surfaces that enable droplets to grow rapidly and to be shed as quickly as possible. However, approaches based on microscale, nanoscale or molecular-scale textures suffer from intrinsic trade-offs that make it difficult to optimize both growth and transport at once. Here we present a conceptually different design approach—based on principles derived from Namib desert beetles, cacti, and pitcher plants—that synergistically combines these aspects of condensation and substantially outperforms other synthetic surfaces. Inspired by an unconventional interpretation of the role of the beetle’s bumpy surface geometry in promoting condensation, and using theoretical modelling, we show how to maximize vapour diffusion fluxat the apex of convex millimetric bumps by optimizing the radius of curvature and cross-sectional shape. Integrating this apex geometry with a widening slope, analogous to cactus spines, directly couples facilitated droplet growth with fast directional transport, by creating a free-energy profile that drives the droplet down the slope before its growth rate can decrease. This coupling is further enhanced by a slippery, pitcher-plant-inspired nanocoating that facilitates feedback between coalescence-driven growth and capillary-driven motion on the way down. Bumps that are rationally designed to integrate these mechanisms are able to grow and transport large droplets even against gravity and overcome the effect of an unfavourable temperature gradient. We further observe an unprecedented sixfold-higher exponent of growth rate, faster onset, higher steady-state turnover rate, and a greater volume of water collected compared to other surfaces. We envision that this fundamental understanding and rational design strategy can be

  7. Condensation on slippery asymmetric bumps.

    PubMed

    Park, Kyoo-Chul; Kim, Philseok; Grinthal, Alison; He, Neil; Fox, David; Weaver, James C; Aizenberg, Joanna

    2016-03-01

    Controlling dropwise condensation is fundamental to water-harvesting systems, desalination, thermal power generation, air conditioning, distillation towers, and numerous other applications. For any of these, it is essential to design surfaces that enable droplets to grow rapidly and to be shed as quickly as possible. However, approaches based on microscale, nanoscale or molecular-scale textures suffer from intrinsic trade-offs that make it difficult to optimize both growth and transport at once. Here we present a conceptually different design approach--based on principles derived from Namib desert beetles, cacti, and pitcher plants--that synergistically combines these aspects of condensation and substantially outperforms other synthetic surfaces. Inspired by an unconventional interpretation of the role of the beetle's bumpy surface geometry in promoting condensation, and using theoretical modelling, we show how to maximize vapour diffusion fluxat the apex of convex millimetric bumps by optimizing the radius of curvature and cross-sectional shape. Integrating this apex geometry with a widening slope, analogous to cactus spines, directly couples facilitated droplet growth with fast directional transport, by creating a free-energy profile that drives the droplet down the slope before its growth rate can decrease. This coupling is further enhanced by a slippery, pitcher-plant-inspired nanocoating that facilitates feedback between coalescence-driven growth and capillary-driven motion on the way down. Bumps that are rationally designed to integrate these mechanisms are able to grow and transport large droplets even against gravity and overcome the effect of an unfavourable temperature gradient. We further observe an unprecedented sixfold-higher exponent of growth rate, faster onset, higher steady-state turnover rate, and a greater volume of water collected compared to other surfaces. We envision that this fundamental understanding and rational design strategy can be

  8. Condensation on slippery asymmetric bumps.

    PubMed

    Park, Kyoo-Chul; Kim, Philseok; Grinthal, Alison; He, Neil; Fox, David; Weaver, James C; Aizenberg, Joanna

    2016-03-01

    Controlling dropwise condensation is fundamental to water-harvesting systems, desalination, thermal power generation, air conditioning, distillation towers, and numerous other applications. For any of these, it is essential to design surfaces that enable droplets to grow rapidly and to be shed as quickly as possible. However, approaches based on microscale, nanoscale or molecular-scale textures suffer from intrinsic trade-offs that make it difficult to optimize both growth and transport at once. Here we present a conceptually different design approach--based on principles derived from Namib desert beetles, cacti, and pitcher plants--that synergistically combines these aspects of condensation and substantially outperforms other synthetic surfaces. Inspired by an unconventional interpretation of the role of the beetle's bumpy surface geometry in promoting condensation, and using theoretical modelling, we show how to maximize vapour diffusion fluxat the apex of convex millimetric bumps by optimizing the radius of curvature and cross-sectional shape. Integrating this apex geometry with a widening slope, analogous to cactus spines, directly couples facilitated droplet growth with fast directional transport, by creating a free-energy profile that drives the droplet down the slope before its growth rate can decrease. This coupling is further enhanced by a slippery, pitcher-plant-inspired nanocoating that facilitates feedback between coalescence-driven growth and capillary-driven motion on the way down. Bumps that are rationally designed to integrate these mechanisms are able to grow and transport large droplets even against gravity and overcome the effect of an unfavourable temperature gradient. We further observe an unprecedented sixfold-higher exponent of growth rate, faster onset, higher steady-state turnover rate, and a greater volume of water collected compared to other surfaces. We envision that this fundamental understanding and rational design strategy can be

  9. Stereoselective synthesis of the C13-C22 fragment of callystatin A by a non-aldol approach.

    PubMed

    Raghavan, Sadagopan; Rajendar, Sheelamanthula

    2015-05-01

    An efficient synthetic route to the C13-C22 subunit of callystatin A is reported. The key features include diastereoselective alkylation, using Myers auxiliary, for the preparation of the three carbon synthon 7, stereo- and regioselective oxidative vicinal functionalization of an electron deficient trisubstituted (Z)-olefin using an intramolecular sulfinyl group as the nucleophile, diastereoselective radical debromination of a bromohydrin derivative using Guindon's protocol to prepare the C16-C18 anti-anti stereotriad, Lewis acid promoted crotylation following Keck's protocol to create C19, C20 stereocenters and the use of the Pummerer reaction to reveal an aldehyde for the extension of two carbons by Wittig olefination. PMID:25827465

  10. Tachyon condensation on brane sphalerons

    NASA Astrophysics Data System (ADS)

    Brito, Francisco A.

    2005-08-01

    We consider a sphaleron solution in field theory that provides a toy model for unstable D-branes of string theory. We investigate the tachyon condensation on a Dp-brane. The localized modes, including a tachyon, arise in the spectrum of a sphaleron solution of a phi4 field theory on Bbb Mp+1 × S1. We use these modes to find a multiscalar tachyon potential living on the sphaleron world-volume. A complete cancelation between brane tension and the minimum of the tachyon potential is found as the size of the circle becomes small.

  11. Turbulent Distortion of Condensate Accretion

    NASA Technical Reports Server (NTRS)

    Hazoume, R.; Orou Chabi, J.; Johnson, J. A., III

    1997-01-01

    When a simple model for the relationship between the density-temperature fluctuation correlation and mean values is used, we determine that the rate of change of turbulent intensity can influence directly the accretion rate of droplets. Considerable interest exists in the accretion rate for condensates in nonequilibrium flow with icing and the potential role which reactant accretion can play in nonequilibrium exothermic reactant processes. Turbulence is thought to play an important role in such flows. It has already been experimentally determined that turbulence influences the sizes of droplets in the heterogeneous nucleation of supersaturated vapors. This paper addresses the issue of the possible influence of turbulence on the accretion rate of droplets.

  12. Predictive thermodynamics for condensed phases.

    PubMed

    Glasser, Leslie; Jenkins, H Donald Brooke

    2005-10-01

    Thermodynamic information is central to assessment of the stability and reactivity of materials. However, because of both the demanding nature of experimental thermodynamics and the virtually unlimited number of conceivable compounds, experimental data is often unavailable or, for hypothetical materials, necessarily impossible to obtain. We describe simple procedures for thermodynamic prediction for condensed phases, both ionic and organic covalent, principally via formula unit volumes (or density); our volume-based approach (VBT) provides a new thermodynamic tool for such assessment. These methods, being independent of detailed knowledge of crystal structures, are applicable to liquids and amorphous materials as well as to crystalline solids. Examples of their use are provided. PMID:16172676

  13. Velocity Condensation for Magnetotactic Bacteria

    NASA Astrophysics Data System (ADS)

    Rupprecht, Jean-François; Waisbord, Nicolas; Ybert, Christophe; Cottin-Bizonne, Cécile; Bocquet, Lydéric

    2016-04-01

    Magnetotactic swimmers tend to align along magnetic field lines against stochastic reorientations. We show that the swimming strategy, e.g., active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics. The latter can exhibit a velocity condensation whereby the alignment probability density diverges. As a consequence, we find that the swimming strategy affects the nature of the phase transition to collective motion, indicating that Lévy run-and-tumble walks can outperform active Brownian processes as strategies to trigger collective behavior.

  14. Asymmetric catalytic synthesis of the proposed structure of trocheliophorolide B.

    PubMed

    Trost, Barry M; Quintard, Adrien

    2012-09-01

    A concise catalytic asymmetric synthesis of the proposed structure of trocheliophorolide B is reported. The synthetic sequence notably features an asymmetric acetaldehyde alkynylation, a Ru-catalyzed alder-ene reaction, and a Zn-ProPhenol ynone aldol condensation. Comparison with the reported data suggests a misassignment of the natural product structure.

  15. Bio-oil fractionation and condensation

    DOEpatents

    Brown, Robert C; Jones, Samuel T; Pollard, Anthony

    2013-07-02

    A method of fractionating bio-oil vapors which involves providing bio-oil vapors comprising bio-oil constituents is described. The bio-oil vapors are cooled in a first stage which comprises a condenser having passages for the bio-oil separated by a heat conducting wall from passages for a coolant. The coolant in the condenser of the first stage is maintained at a substantially constant temperature, set at a temperature in the range of 75 to 100.degree. C., to condense a first liquid fraction of liquefied bio-oil constituents in the condenser of the first stage. The first liquid fraction of liquified bio-oil constituents from the condenser in the first stage is collected. Also described are steps for subsequently recovering further liquid fractions of liquefied bio-oil constituents. Particular compositions of bio-oil condensation products are also described.

  16. Axions: Bose Einstein condensate or classical field?

    NASA Astrophysics Data System (ADS)

    Davidson, Sacha

    2015-05-01

    The axion is a motivated dark matter candidate, so it would be interesting to find features in Large Scale Structures specific to axion dark matter. Such features were proposed for a Bose Einstein condensate of axions, leading to confusion in the literature (to which I contributed) about whether axions condense due to their gravitational interactions. This note argues that the Bose Einstein condensation of axions is a red herring: the axion dark matter produced by the misalignment mechanism is already a classical field, which has the distinctive features attributed to the axion condensate (BE condensates are described as classical fields). This note also estimates that the rate at which axion particles condense to the field, or the field evaporates to particles, is negligible.

  17. Investigation of thermochemistry associated with the carbon-carbon coupling reactions of furan and furfural using ab initio methods.

    PubMed

    Liu, Cong; Assary, Rajeev S; Curtiss, Larry A

    2014-06-26

    Upgrading furan and small oxygenates obtained from the decomposition of cellulosic materials via formation of carbon-carbon bonds is critical to effective conversion of biomass to liquid transportation fuels. Simulation-driven molecular level understanding of carbon-carbon bond formation is required to design efficient catalysts and processes. Accurate quantum chemical methods are utilized here to predict the reaction energetics for conversion of furan (C4H4O) to C5-C8 ethers and the transformation of furfural (C5H6O2) to C13-C26 alkanes. Furan can be coupled with various C1 to C4 low molecular weight carbohydrates obtained from the pyrolysis via Diels-Alder type reactions in the gas phase to produce C5-C8 cyclic ethers. The computed reaction barriers for these reactions (∼25 kcal/mol) are lower than the cellulose activation or decomposition reactions (∼50 kcal/mol). Cycloaddition of C5-C8 cyclo ethers with furans can also occur in the gas phase, and the computed activation energy is similar to that of the first Diels-Alder reaction. Furfural, obtained from biomass, can be coupled with aldehydes or ketones with α-hydrogen atoms to form longer chain aldol products, and these aldol products can undergo vapor phase hydrocycloaddition (activation barrier of ∼20 kcal/mol) to form the precursors of C26 cyclic hydrocarbons. These thermochemical studies provide the basis for further vapor phase catalytic studies required for upgrading of furans/furfurals to longer chain hydrocarbons. PMID:24902118

  18. Investigation of thermochemistry associated with the carbon-carbon coupling reactions of furan and furfural using ab initio methods.

    PubMed

    Liu, Cong; Assary, Rajeev S; Curtiss, Larry A

    2014-06-26

    Upgrading furan and small oxygenates obtained from the decomposition of cellulosic materials via formation of carbon-carbon bonds is critical to effective conversion of biomass to liquid transportation fuels. Simulation-driven molecular level understanding of carbon-carbon bond formation is required to design efficient catalysts and processes. Accurate quantum chemical methods are utilized here to predict the reaction energetics for conversion of furan (C4H4O) to C5-C8 ethers and the transformation of furfural (C5H6O2) to C13-C26 alkanes. Furan can be coupled with various C1 to C4 low molecular weight carbohydrates obtained from the pyrolysis via Diels-Alder type reactions in the gas phase to produce C5-C8 cyclic ethers. The computed reaction barriers for these reactions (∼25 kcal/mol) are lower than the cellulose activation or decomposition reactions (∼50 kcal/mol). Cycloaddition of C5-C8 cyclo ethers with furans can also occur in the gas phase, and the computed activation energy is similar to that of the first Diels-Alder reaction. Furfural, obtained from biomass, can be coupled with aldehydes or ketones with α-hydrogen atoms to form longer chain aldol products, and these aldol products can undergo vapor phase hydrocycloaddition (activation barrier of ∼20 kcal/mol) to form the precursors of C26 cyclic hydrocarbons. These thermochemical studies provide the basis for further vapor phase catalytic studies required for upgrading of furans/furfurals to longer chain hydrocarbons.

  19. Decomposition of condensed phase energetic materials: interplay between uni- and bimolecular mechanisms.

    PubMed

    Furman, David; Kosloff, Ronnie; Dubnikova, Faina; Zybin, Sergey V; Goddard, William A; Rom, Naomi; Hirshberg, Barak; Zeiri, Yehuda

    2014-03-19

    Activation energy for the decomposition of explosives is a crucial parameter of performance. The dramatic suppression of activation energy in condensed phase decomposition of nitroaromatic explosives has been an unresolved issue for over a decade. We rationalize the reduction in activation energy as a result of a mechanistic change from unimolecular decomposition in the gas phase to a series of radical bimolecular reactions in the condensed phase. This is in contrast to other classes of explosives, such as nitramines and nitrate esters, whose decomposition proceeds via unimolecular reactions both in the gas and in the condensed phase. The thermal decomposition of a model nitroaromatic explosive, 2,4,6-trinitrotoluene (TNT), is presented as a prime example. Electronic structure and reactive molecular dynamics (ReaxFF-lg) calculations enable to directly probe the condensed phase chemistry under extreme conditions of temperature and pressure, identifying the key bimolecular radical reactions responsible for the low activation route. This study elucidates the origin of the difference between the activation energies in the gas phase (~62 kcal/mol) and the condensed phase (~35 kcal/mol) of TNT and identifies the corresponding universal principle. On the basis of these findings, the different reactivities of nitro-based organic explosives are rationalized as an interplay between uni- and bimolecular processes.

  20. Compressible Heating in the Condense Phase due to Pore Collapse in HMX

    NASA Astrophysics Data System (ADS)

    Zhang, Ju; Jackson, Thomas

    Axisymmetric pore collapse in HMX is studied numerically by solving multi-phase reactive Euler equations. The generation of hot spots in the condense phase due to compressible heating is examined. The motivation is to improve the understanding of the role of embedded cavities in the initiation of reaction in explosives, and to investigate the effect of hot spots in the condense phase due to compressible heating alone, complementing previous study on hot spots due to the reaction in the gas phase and at the interface. It is found that the shock-cavity interaction results in pressures and thus temperatures that are substantially higher than the post-shock values in the condense phase. However, these hot spots in the condense phase due to compressible heating alone do not seem to be sufficiently hot to lead to ignition at shock pressures of 1-3 GPa. Thus, compressible heating in the condense phase may be excluded as a mechanism for initiation of explosives. It should be pointed out that the ignition threshold for the temperature, the so-called ``switch-on'' temperature, of hot spots depend on chemistry kinetics parameters. Switch-on temperature is lower for faster reaction rate. The current chemistry kinetics parameters are based on previous experimental work. This work was supported in part by the Defense Threat Reduction Agency and by the U.S. Department of Energy.

  1. High-temperature condensates in carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Grossman, L.

    1977-01-01

    Equilibrium thermodynamic calculations of the sequence of condensation of minerals from a cooling gas of solar composition play an important role in explaining the mineralogy and trace element content of different types of inclusions in carbonaceous chondrites. Group IV B iron meteorites and enstatite chondrites may also be direct condensates from the solar nebula. Condensation theory provides a framework within which chemical fractionations between different classes of chondrites may be understood.

  2. Bose-Einstein condensation of cesium.

    PubMed

    Weber, Tino; Herbig, Jens; Mark, Michael; Nägerl, Hanns-Christoph; Grimm, Rudolf

    2003-01-10

    Bose-Einstein condensation of cesium atoms is achieved by evaporative cooling using optical trapping techniques. The ability to tune the interactions between the ultracold atoms by an external magnetic field is crucial to obtain the condensate and offers intriguing features for potential applications. We explore various regimes of condensate self-interaction (attractive, repulsive, and null interaction strength) and demonstrate properties of imploding, exploding, and non-interacting quantum matter. PMID:12471267

  3. Condensation induced water hammer safety

    SciTech Connect

    Gintner, M.A.

    1997-03-10

    Condensation induced water hammer events in piping systems can cause catastrophic steam system failures which can result in equipment damage, personal injury, and even death. As an industry, we have learned to become accustomed to the ''banging'' that we often hear in our steam piping systems, and complacent in our actions to prevent it. It is unfortunate that lives are lost needlessly, as this type of water hammer event is preventable if one only applies some basic principles when operating and maintaining their steam systems. At the U. S. Department of Energy's Hanford Site where I work, there was one such accident that occurred in 1993 which took the life of a former co-worker and friend of mine. Hanford was established as part of the Manhattan Project during World War II. it is a 560 square mile complex located along the banks of the Columbia River in Southeastern Washington State. For almost 45 years, hanford's mission was to produce weapons grade plutonium for our nations defense programs. Today, Hanford no longer produces plutonium, but is focused on site clean-up and economic diversification. Hanford still uses steam for heating and processing activities, utilizing over 20 miles of piping distribution systems similar to those found in industry. Although these aging systems are still sound, they cannot stand up to the extreme pressure pulses developed by a condensation induced water hammer.

  4. Enhanced condensation heat transfer with wettability patterning

    NASA Astrophysics Data System (ADS)

    Sinha Mahapatra, Pallab; Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

    2015-11-01

    Condensation of water vapor on metal surfaces is useful for many engineering applications. A facile and scalable method is proposed for removing condensate from a vertical plate during dropwise condensation (DWC) in the presence of non-condensable gases (NCG). We use wettability-patterned superhydrophilic tracks (filmwise condensing domains) on a mirror-finish (hydrophilic) aluminum surface that promotes DWC. Tapered, horizontal ``collection'' tracks are laid to create a Laplace pressure driven flow, which collects condensate from the mirror-finish domains and sends it to vertical ``drainage tracks'' for gravity-induced shedding. An optimal design is achieved by changing the fractional area of superhydrophilic tracks with respect to the overall plate surface, and augmenting capillary-driven condensate-drainage by adjusting the track spatial layout. The design facilitates pump-less condensate drainage and enhances DWC heat transfer on the mirror-finish regions. The study highlights the relative influences of the promoting and retarding effects of dropwise and filmwise condensation zones on the overall heat transfer improvement on the substrate. The study demonstrated ~ 34% heat transfer improvement on Aluminum surface for the optimized design.

  5. Reflux condensation in a closed tube

    SciTech Connect

    Tien, C.L.

    1984-10-01

    Reflux condensation which may have an appreciable effect on the reflood process in the reactor core during the loss-of-coolant accident is investigated experimentally and analytically in the present work using the vertical two-phase closed thermosyphon. The condensation heat transfer coefficients of the countercurrent vapor-liquid flows are locally measured along the condenser wall. The results indicate that Nusselt's solution for film condensation cannot interpret satisfactorily the observed trend. Further improvements are made to consider the effects of interfacial shear, waviness and non-condensable gas on condensation. The vapor shear retards the condensate flow and thus increases the film thickness, which results in lower heat transfer coefficients than those calculated from Nusselt theory. Modified Fanning friction factors which account for the augmentation of interfacial shear through phase change are used to evaluate the reduction of heat transfer by vapor shear. On the other hand, the waves appearing on the interface can enhance heat transfer rates. Such enhancement is determined by solving numerically the nonlinear equation for the wavy interface. When non-condensable gases are present in the system, they will accumulate at the condenser end forming a gas barrier to the vapor and shut off that portion. A two-dimensional model is developed to include both axial and radial diffusion of gas mass. This two-dimensional analysis indicates the inadequacy of the common one-dimensional diffuse-front model in considering only axial diffusion of gas in most physical systems.

  6. Advances in modelling of condensation phenomena

    SciTech Connect

    Liu, W.S.; Zaltsgendler, E.; Hanna, B.

    1997-07-01

    The physical parameters in the modelling of condensation phenomena in the CANDU reactor system codes are discussed. The experimental programs used for thermal-hydraulic code validation in the Canadian nuclear industry are briefly described. The modelling of vapour generation and in particular condensation plays a key role in modelling of postulated reactor transients. The condensation models adopted in the current state-of-the-art two-fluid CANDU reactor thermal-hydraulic system codes (CATHENA and TUF) are described. As examples of the modelling challenges faced, the simulation of a cold water injection experiment by CATHENA and the simulation of a condensation induced water hammer experiment by TUF are described.

  7. Water Condensation Kinetics on a Hydrophobic Surface

    NASA Astrophysics Data System (ADS)

    Linderoth, Trolle R.; Zhdanov, Vladimir P.; Kasemo, Bengt

    2003-04-01

    Employing thermal desorption spectroscopy, we show that the effective probability of water condensation at low water vapor pressure on an octane film is much below unity at 100 120K. This unusual finding is related to a small binding energy of H2O monomers on octane (≃0.08 eV), requiring the formation of critical water clusters for condensation to occur. This results in strong temperature and impingement-rate dependencies of the water condensation rate and a nonlinear uptake as a function of dose time. All these features are rationalized quantitatively by a kinetic model of water condensation.

  8. Treatment of evaporator condensates by pervaporation

    DOEpatents

    Blume, Ingo; Baker, Richard W.

    1990-01-01

    A pervaporation process for separating organic contaminants from evaporator condensate streams is disclosed. The process employs a permselective membrane that is selectively permeable to an organic component of the condensate. The process involves contacting the feed side of the membrane with a liquid condensate stream, and withdrawing from the permeate side a vapor enriched in the organic component. The driving force for the process is the in vapor pressure across the membrane. This difference may be provided for instance by maintaining a vacuum on the permeate side, or by condensing the permeate. The process offers a simple, economic alternative to other separation techniques.

  9. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT: NEW CONDENSATOR, INC.--THE CONDENSATOR DIESEL ENGINE RETROFIT CRANKCASE VENTILATION SYSTEM

    EPA Science Inventory

    EPA's Environmental Technology Verification Program has tested New Condensator Inc.'s Condensator Diesel Engine Retrofit Crankcase Ventilation System. Brake specific fuel consumption (BSFC), the ratio of engine fuel consumption to the engine power output, was evaluated for engine...

  10. A cis-prenyltransferase from Methanosarcina acetivorans catalyzes both head-to-tail and nonhead-to-tail prenyl condensation.

    PubMed

    Ogawa, Takuya; Emi, Koh-Ichi; Koga, Kazushi; Yoshimura, Tohru; Hemmi, Hisashi

    2016-06-01

    Cis-prenyltransferase usually consecutively catalyzes the head-to-tail condensation reactions of isopentenyl diphosphate to allylic prenyl diphosphate in the production of (E,Z-mixed) polyprenyl diphosphate, which is the precursor of glycosyl carrier lipids. Some recently discovered homologs of the enzyme, however, catalyze the nonhead-to-tail condensation reactions between allylic prenyl diphosphates. In this study, we characterize a cis-prenyltransferase homolog from a methanogenic archaeon, Methanosarcina acetivorans, to obtain information on the biosynthesis of the glycosyl carrier lipids within it. This enzyme catalyzes both head-to-tail and nonhead-to-tail condensation reactions. The kinetic analysis shows that the main reaction of the enzyme is consecutive head-to-tail prenyl condensation reactions yielding polyprenyl diphosphates, while the chain lengths of the major products seem shorter than expected for the precursor of glycosyl carrier lipids. On the other hand, a subsidiary reaction of the enzyme, i.e., nonhead-to-tail condensation between dimethylallyl diphosphate and farnesyl diphosphate, gives a novel diterpenoid compound, geranyllavandulyl diphosphate.

  11. Bose-Einstein-condensate heating by atomic losses

    SciTech Connect

    Dziarmaga, Jacek; Sacha, Krzysztof

    2003-10-01

    Atomic Bose-Einstein condensate is heated by atomic losses. The losses act as a heat reservoir for the condensate. The condensate is approaching a state of thermal equilibrium with a thermal depletion ranging from 1% for a uniform three-dimensional (3D) condensate to around 13% for a quasi-1D condensate in a harmonic trap.

  12. CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers.

    PubMed

    Li, Jun-De

    2013-02-01

    This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected.

  13. CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers

    PubMed Central

    Li, Jun-De

    2013-01-01

    This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected. PMID:24850953

  14. Drug Reactions

    MedlinePlus

    ... or diabetes. But medicines can also cause unwanted reactions. One problem is interactions, which may occur between ... more serious. Drug allergies are another type of reaction. They can be mild or life-threatening. Skin ...

  15. Diastereoselective self-condensation of dihydroxyfumaric acid in water: potential route to sugars.

    PubMed

    Naidu Sagi, Vasudeva; Karri, Phaneendrasai; Hu, Fang; Krishnamurthy, Ramanarayanan

    2011-08-22

    Jack of all trades: water-soluble salts of DHF underwent self-condensation to afford the threo diastereomer of pentulosonic acid, through differing reaction pathways contingent on the metal salt used. This transformation exemplifies the diverging roles of DHF as a nucleophile (a synthon for α-hydroxyacetyl anion) and an electrophile (an α-carboxyglycolaldehyde equivalent).

  16. Tunable Vapor-Condensed Nanolenses

    PubMed Central

    2015-01-01

    Nanostructured optical components, such as nanolenses, direct light at subwavelength scales to enable, among others, high-resolution lithography, miniaturization of photonic circuits, and nanoscopic imaging of biostructures. A major challenge in fabricating nanolenses is the appropriate positioning of the lens with respect to the sample while simultaneously ensuring it adopts the optimal size and shape for the intended use. One application of particular interest is the enhancement of contrast and signal-to-noise ratio in the imaging of nanoscale objects, especially over wide fields-of-view (FOVs), which typically come with limited resolution and sensitivity for imaging nano-objects. Here we present a self-assembly method for fabricating time- and temperature-tunable nanolenses based on the condensation of a polymeric liquid around a nanoparticle, which we apply to the high-throughput on-chip detection of spheroids smaller than 40 nm, rod-shaped particles with diameter smaller than 20 nm, and biofunctionalized nanoparticles, all across an ultralarge FOV of >20 mm2. Previous nanoparticle imaging efforts across similar FOVs have detected spheroids no smaller than 100 nm, and therefore our results demonstrate the detection of particles >15-fold smaller in volume, which in free space have >240 times weaker Rayleigh scattering compared to the particle sizes detected in earlier wide-field imaging work. This entire platform, with its tunable nanolens condensation and wide-field imaging functions, is also miniaturized into a cost-effective and portable device, which might be especially important for field use, mobile sensing, and diagnostics applications, including, for example, the measurement of viral load in bodily fluids. PMID:24979060

  17. Molecular attraction of condensed bodies

    NASA Astrophysics Data System (ADS)

    Derjaguin, B. V.; Abrikosova, I. I.; Lifshitz, E. M.

    2015-09-01

    From the Editorial Board. As a contribution to commemorating the 100th anniversary of the birth of Evgenii Mikhailovich Lifshitz, it was found appropriate by the Editorial Board of Uspekhi Fizicheskikh Nauk (UFN) [Physics-Uspekhi] journal that the materials of the jubilee-associated Scientific Session of the Physical Sciences Division of the Russian Academy of Sciences published in this issue (pp. 877-905) be augmented by the review paper "Molecular attraction of condensed bodies" reproduced from a 1958 UFN issue. Included in this review, in addition to an account by Evgenii Mikhailovich Lifshitz of his theory of molecular attractive forces between condensed bodies (first published in Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki (ZhETF) in 1955 and in its English translation Journal of Experimental and Theoretical Physics (JETP) in 1956), is a summary of a series of experimental studies beginning in 1949 by Irina Igorevna Abrikosova at the Institute of Physical Chemistry of the Academy of Sciences of the USSR in a laboratory led by Boris Vladimirovich Derjaguin (1902-1994), a Corresponding Member of the USSR Academy of Sciences. In 1958, however, UFN was not yet available in English translation, so the material of the review is insufficiently accessible to the present-day English-speaking reader. This is the reason why the UFN Editorial Board decided to contribute to celebrating the 100th anniversary of E M Lifshitz's birthday by reproducing on the journal's pages a 1958 review paper which contains both E M Lifshitz's theory itself and the experimental data that underpinned it (for an account of how Evgenii Mikhailovich Lifshitz was enlisted to explain the experimental results of I I Abrikosova and B V Derjaguin, see the letter to the editors N P Danilova on page 925 of this jubilee collection of publications).

  18. Proceedings: 2002 Workshop on Condensate Polishing

    SciTech Connect

    2002-06-01

    Condensate polishing aims to control impurities in a nuclear power plant, thus allowing the unit to operate more reliably. This report contains the work presented at EPRI's 2002 Workshop on Condensate Polishing, where 36 papers were presented on current issues, research, and utility experiences involving polishing issues at both pressurized water reactor (PWR) and boiling water reactor (BWR) units.

  19. Soliton resonance in bose-einstein condensate

    NASA Technical Reports Server (NTRS)

    Zak, Michail; Kulikov, I.

    2002-01-01

    A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

  20. Collision of Bose Condensate Dark Matter structures

    SciTech Connect

    Guzman, F. S.

    2008-12-04

    The status of the scalar field or Bose condensate dark matter model is presented. Results about the solitonic behavior in collision of structures is presented as a possible explanation to the recent-possibly-solitonic behavior in the bullet cluster merger. Some estimates about the possibility to simulate the bullet cluster under the Bose Condensate dark matter model are indicated.

  1. Hydrophilic structures for condensation management in appliances

    DOEpatents

    Kuehl, Steven John; Vonderhaar, John J.; Wu, Guolian; Wu, Mianxue

    2016-02-02

    An appliance that includes a cabinet having an exterior surface; a refrigeration compartment located within the cabinet; and a hydrophilic structure disposed on the exterior surface. The hydrophilic structure is configured to spread condensation. The appliance further includes a wicking structure located in proximity to the hydrophilic structure, and the wicking structure is configured to receive the condensation.

  2. Dual condensate and QCD phase transition

    SciTech Connect

    Zhang Bo; Bruckmann, Falk; Fodor, Zoltan; Szabo, Kalman K.; Gattringer, Christof

    2011-05-23

    The dual condensate is a new QCD phase transition order parameter, which connnects confinement and chiral symmetry breaking as different mass limits. We discuss the relation between the fermion spectrum at general boundary conditions and the dual condensate and show numerical results for the latter from unquenched SU(3) lattice configurations.

  3. Quantum metrology with Bose-Einstein condensates

    SciTech Connect

    Boixo, Sergio; Datta, Animesh; Davis, Matthew J.; Flammia, Steven T.; Shaji, Anil; Tacla, Alexandre B.; Caves, Carlton M.

    2009-04-13

    We show how a generalized quantum metrology protocol can be implemented in a two-mode Bose-Einstein condensate of n atoms, achieving a sensitivity that scales better than 1/n and approaches 1/n{sup 3/2} for appropriate design of the condensate.

  4. Condensation of liquid metals under low pressures

    SciTech Connect

    Elafify, M.M.

    1988-01-01

    The Direct Simulation Monte Carlo (DSMC) method is used to study one-dimensional condensation phenomena for a pure vapor or vapor/gas mixture. The results are fitted to an interpolation formula describing the condensation mass flux to provide a usable engineering correlation. For pure vapor, the DSMC results are compared with the available experimental data for condensation of mercury under low pressure. Results are compared also with some of the theoretical models. The comparison shows that the DSMC method is able to detect the qualitative behavior of the condensation mass flux, although it overestimates the mass flux by 20-30%. Compared with other introduced theoretical models, the DSMC method has the most-consistent representation of the qualitative behavior of the condensation mass flux. The method was also used to represent condensation in the presence of a noncondensable gas. A formal proof for choosing collision partners was introduced and applied in the case of condensation in the presence of a noncondensable gas. The method is applied to condensation of mercury in the presence of different monatomic noncondensable gases at different partial pressures.

  5. The Redox-A(3) Reaction.

    PubMed

    Seidel, Daniel

    2014-06-01

    This Highlight details the recent emergence of a new type of A(3) reaction (three-component condensation of an amine, an aldehyde and an alkyne). In contrast to the classic A(3) coupling process, the redox-A(3) reaction incorporates an iminium isomerization step and leads to amine α-alkynylation. The overall transformation is redox-neutral by virtue of a combined reductive N-alkylation/oxidative C-H bond functionalization.

  6. Condensed Matter Theories - Volume 22

    NASA Astrophysics Data System (ADS)

    Reinholz, Heidi; Röpke, Gerd; de Llano, Manuel

    2007-09-01

    pt. A. Fermi liquids. Pressure comparison between the spherical cellular model and the Thomas-Fermi model / G.A. Baker, Jr. Pair excitations and vertex corrections in Fermi fluids and the dynamic structure function of two-dimension 3He / H.M. Böhm, H. Godfrin, E. Krotscheck, H.J. Lauter, M. Meschke and M. Panholzer. Condensation of helium in wedges / E.S. Hernádez ... [et al.]. Non-Fermi liquid behavior from the Fermi-liquid approach / V.A. Khodel ... [et al.]. Theory of third sound and stability of thin 3He-4He superfluid films / E. Krotscheck and M.D. Miller. Pairing in asymmetrical Fermi systems / K.F. Quader and R. Liao. Ground-state properties of small 3He drops from quantum Monte Carlo simulations / E. Sola, J. Casulleras and J. Boronat. Ground-state energy and compressibility of a disordered two-dimensional electron gas / Tanatar ... [et al.]. Quasiexcitons in photoluminescence of incompressible quantum liquids / A. Wójs, A.G ladysiewicz and J.J. Quinn -- pt. B. Bose liquids. Quantum Boltzmann liquids / K.A. Gernoth, M L. Ristig and T. Lindenau. Condensate fraction in the dynamic structure function of Bose fluids / M. Saarela, F. Mazzanti and V. Apaja -- pt. C. Strongly-correlated electronic systems. Electron gas in high-field nanoscopic transport: metallic carbon nanotubes / F. Green and D. Neilson. Evolution and destruction of the Kondo effect in a capacitively coupled double dot system / D.E. Logan and M.R. Galpin. The method of increments-a wavefunction-based Ab-Initio correlation method for solids / B. Paulus. Fractionally charged excitations on frustrated lattices / E. Runge, F. Pollmann and P. Fulde. 5f Electrons in actinides: dual nature and photoemission spectra / G. Zwicknagl -- pt. D. Magnetism. Magnetism in disordered two-dimensional Kondo-Necklace / W. Brenig. On the de Haas-can Alphen oscillation in 2D / S. Fujita and D.L. Morabito. Dynamics in one-dimensional spin systems-density matrix reformalization group study / S. Nishimoto and M

  7. Synthesis of propionate motifs: diastereoselective tandem reactions involving anionic and free radical based processes.

    PubMed

    Guindon, Y; Houde, K; Prévost, M; Cardinal-David, B; Landry, S R; Daoust, B; Bencheqroun, M; Guérin, B

    2001-09-01

    Reported herein is a strategy employing a Mukaiyama reaction in tandem with a hydrogen transfer reaction for the elaboration of propionate motifs. The nature of the protecting groups on the chiral beta-alkoxy aldehyde and the type of Lewis acid used are varied to modulate the stereochemical outcome of the tandem reactions. The mode of complexation is thus controlled (monodentate or chelate) for the Mukaiyama reaction to give access to either syn or anti aldol products, precursors of the free radical reduction reaction. The endocyclic effect is subsequently capitalized upon to control the hydrogen transfer step so that the syn-reduced product may be achieved. Proceeding with excellent yield and diastereoselectivity, the synthetic sequence proposed gives access to syn-syn and syn-anti propionate motifs. Also considered is a complementary approach using a chelation-controlled Mukaiyama reaction in tandem with a free radical allylation reaction under the control of the endocyclic effect that leads to the anti-anti product.

  8. Bose-Einstein condensation of chromium.

    PubMed

    Griesmaier, Axel; Werner, Jörg; Hensler, Sven; Stuhler, Jürgen; Pfau, Tilman

    2005-04-29

    We report on the generation of a Bose-Einstein condensate in a gas of chromium atoms, which have an exceptionally large magnetic dipole moment and therefore underlie anisotropic long-range interactions. The preparation of the chromium condensate requires novel cooling strategies that are adapted to its special electronic and magnetic properties. The final step to reach quantum degeneracy is forced evaporative cooling of 52Cr atoms within a crossed optical dipole trap. At a critical temperature of T(c) approximately 700 nK, we observe Bose-Einstein condensation by the appearance of a two-component velocity distribution. We are able to produce almost pure condensates with more than 50,000 condensed 52Cr atoms.

  9. Film condensation in a horizontal rectangular duct

    NASA Technical Reports Server (NTRS)

    Lu, Qing; Suryanarayana, N. V.

    1993-01-01

    Condensation heat transfer in a horizontal rectangular duct was experimentally and analytically investigated. To prevent the dripping of condensate on the film, the experiment was conducted inside a horizontal rectangular duct with vapor condensing only on the bottom cooled plate of the duct. R-113 and FC-72 (Fluorinert Electronic Fluid developed by the 3M Company) were used as the condensing fluids. The experimental program included measurements of film thickness, local and average heat transfer coefficients, wave length, wave speed, and a study of wave initiation. The measured film thickness was used to obtain the local heat transfer coefficient. The wave initiation was studied both with condensation and with an adiabatic air-liquid flow. The test sections used in both experiments were identical.

  10. Low Energy Nuclear Reactions: 2007 Update

    NASA Astrophysics Data System (ADS)

    Krivit, Steven B.

    2007-03-01

    This paper presents an overview of low energy nuclear reactions, a subset of the field of condensed matter nuclear science. Condensed matter nuclear science studies nuclear effects in and/or on condensed matter, including low energy nuclear reactions, an entirely new branch of science that gained widespread attention and notoriety beginning in 1989 with the announcement of a previously unrecognized source of energy by Martin Fleischmann and Stanley Pons that came to be known as cold fusion. Two branches of LENR are recognized. The first includes a set of reactions like those observed by Fleischmann and Pons that use palladium and deuterium and yield excess heat and helium-4. Numerous mechanisms have been proposed to explain these reactions, however there is no consensus for, or general acceptance of, any of the theories. The claim of fusion is still considered speculative and, as such, is not an ideal term for this work. The other branch is a wide assortment of nuclear reactions that may occur with either hydrogen or deuterium. Anomalous nuclear transmutations are reported that involve light as well as heavy elements. The significant questions that face this field of research are: 1) Are LENRs a genuine nuclear reaction? 2) If so, is there a release of excess energy? 3) If there is, is the energy release cost-effective?

  11. Copper-catalyzed synthesis of substituted quinolines via C–N coupling/condensation from ortho-acylanilines and alkenyl iodides.

    PubMed

    Kong, Lingkai; Zhou, Yuanyuan; Huang, He; Yang, Yang; Liu, Yuanyuan; Li, Yanzhong

    2015-01-16

    An efficient cascade copper-catalyzed intermolecular Ullmann-type C–N coupling/enamine condensation reaction is described, in which ortho-acylanilines and alkenyl iodides converted to multisubstituted quinolines in good to excellent yields.

  12. Formation of pyrophosphate on hydroxyapatite with thioesters as condensing agents

    NASA Technical Reports Server (NTRS)

    Weber, A. L.

    1982-01-01

    'Energy-rich' thioesters are shown to act as condensing agents in the formation of pyrophosphate on hydroxyapatite in the presence of water at ambient temperature. The yield of pyrophosphate based on thioester ranges from 2.5% to 11.4% and depends upon the pH and concentration of reactants. Reaction of 0.130 M hydroxyapatite suspended in a solution of 0.08 M sodium phosphate and 0.20 M imidazole hydrochloride (pH 7.0) with 0.10 M N,S-diacetylcysteamine for 6 days gives the highest yield of pyrophosphate (11.4%). Pyrophosphate formation requires the presence of hydroxyapatite, sodium phosphate and the thioester, N,S-diacetylcysteamine. The related thioester, N,S-diacetylcysteine, also yields pyrophosphate in reactions on hydroxyapatite.

  13. Dynamics of condensation on lubricant impregnated surfaces

    NASA Astrophysics Data System (ADS)

    Anand, Sushant; Paxson, Adam; Rykaczewski, Konrad; Beysens, Daniel; Varanasi, Kripa

    2013-03-01

    Replacing the filmwise condensation mode with dropwise condensation promises large improvements in heat transfer that will lead to large cost savings in material, water consumption and decreased size of the systems. In this regards, use of superhydrophobic surfaces fabricated by texturing surfaces with nano/microstructures has been shown to lead decrease in contact line pinning of millimetric drops resulting in fast shedding. However, these useful properties are lost during condensation where droplets that nucleate within texture grow by virtue of condensation to large sized droplets while still adhering to the surface. Recently we have shown that liquid impregnated surfaces can overcome many limitations of conventional superhydrophobic surfaces during condensation. Here we discuss aspects related to condensation on lubricant surfaces, such as behavior of growing droplets. We compare the characteristics of droplets condensing on these surfaces with their behavior on conventional un-impregnated superhydrophobic surfaces and show how use of lubricant impregnated surfaces may lead to large enhancement in heat transfer and energy efficiencies.

  14. Enhancing dropwise condensation through bioinspired wettability patterning.

    PubMed

    Ghosh, Aritra; Beaini, Sara; Zhang, Bong June; Ganguly, Ranjan; Megaridis, Constantine M

    2014-11-01

    Dropwise condensation (DWC) heat transfer depends strongly on the maximum diameter (Dmax) of condensate droplets departing from the condenser surface. This study presents a facile technique implemented to gain control of Dmax in DWC within vapor/air atmospheres. We demonstrate how this approach can enhance the corresponding heat transfer rate by harnessing the capillary forces in the removal of the condensate from the surface. We examine various hydrophilic-superhydrophilic patterns, which, respectively, sustain and combine DWC and filmwise condensation on the substrate. The material system uses laser-patterned masking and chemical etching to achieve the desired wettability contrast and does not employ any hydrophobizing agent. By applying alternating straight parallel strips of hydrophilic (contact angle ∼78°) mirror-finish aluminum and superhydrophilic regions (etched aluminum) on the condensing surface, we show that the average maximum droplet size on the less-wettable domains is nearly 42% of the width of the corresponding strips. An overall improvement in the condensate collection rate, up to 19% (as compared to the control case of DWC on mirror-finish aluminum) was achieved by using an interdigitated superhydrophilic track pattern (on the mirror-finish hydrophilic surface) inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern design, particularly under higher humidity conditions in the presence of noncondensable gases (NCG), a condition that is more challenging for maintaining sustained DWC.

  15. Black holes in the ghost condensate

    SciTech Connect

    Mukohyama, Shinji

    2005-05-15

    We investigate how the ghost condensate reacts to black holes immersed in it. A ghost condensate defines a hypersurface-orthogonal congruence of timelike curves, each of which has the tangent vector u{sup {mu}}=-g{sup {mu}}{sup {nu}}{partial_derivative}{sub {nu}}{phi}. It is argued that the ghost condensate in this picture approximately corresponds to a congruence of geodesics. In other words, the ghost condensate accretes into a black hole just like a pressureless dust. Correspondingly, if the energy density of the ghost condensate at large distance is set to an extremely small value by cosmic expansion then the late-time accretion rate of the ghost condensate should be negligible. The accretion rate remains very small even if effects of higher derivative terms are taken into account, provided that the black hole is sufficiently large. It is also discussed how to reconcile the black-hole accretion with the possibility that the ghost condensate might behave like dark matter.

  16. Dispensing fuel with aspiration of condensed vapors

    SciTech Connect

    Butkovich, M.S.; Strock, D.J.

    1993-08-10

    A vapor recovery process is described, comprising the steps of: fueling a motor vehicle with gasoline by discharging gasoline into a fill opening or filler pipe of a tank of said vehicle through a fuel outlet conduit of a nozzle; emitting gasoline vapors from said tank during said fueling; substantially collecting said vapors during said fueling with a vapor return conduit of said nozzle and passing said vapors through said vapor return conduit in counter current flow relationship to said discharging gasoline in said fuel conduit; conveying said vapors from said vapor return conduit to a vapor return hose; at least some of said vapors condensing to form condensate in said vapor return hose; substantially removing said condensate from said vapor return hose during said fueling with a condensate pickup tube from said nozzle by passing said condensate through said condensate pickup tube in counter current flow relationship to said conveying vapors in said vapor return hose; sensing the presence of gasoline with a liquid sensing tube in said vapor return conduit of said nozzle between inner and outer spouts of said nozzle to detect when said tank of said vehicle is filled with said fuel conduit being within the inner spout of said nozzle; and automatically shutting off said fueling and condensate removing when said liquid sensing tube detects when said tank of said vehicle is filled and fuel enters said vapor return conduit.

  17. Boson condensation in topologically ordered quantum liquids

    NASA Astrophysics Data System (ADS)

    Neupert, Titus; He, Huan; von Keyserlingk, Curt; Sierra, Germán; Bernevig, B. Andrei

    2016-03-01

    Boson condensation in topological quantum field theories (TQFT) has been previously investigated through the formalism of Frobenius algebras and the use of vertex lifting coefficients. While general, this formalism is physically opaque and computationally arduous: analyses of TQFT condensation are practically performed on a case by case basis and for very simple theories only, mostly not using the Frobenius algebra formalism. In this paper, we provide a way of treating boson condensation that is computationally efficient. With a minimal set of physical assumptions, such as commutativity of lifting and the definition of confined particles, we can prove a number of theorems linking Boson condensation in TQFT with chiral algebra extensions, and with the factorization of completely positive matrices over Z+. We present numerically efficient ways of obtaining a condensed theory fusion algebra and S matrices; and we then use our formalism to prove several theorems for the S and T matrices of simple current condensation and of theories which upon condensation result in a low number of confined particles. We also show that our formalism easily reproduces results existent in the mathematical literature such as the noncondensability of five and ten layers of the Fibonacci TQFT.

  18. Enhancing dropwise condensation through bioinspired wettability patterning.

    PubMed

    Ghosh, Aritra; Beaini, Sara; Zhang, Bong June; Ganguly, Ranjan; Megaridis, Constantine M

    2014-11-01

    Dropwise condensation (DWC) heat transfer depends strongly on the maximum diameter (Dmax) of condensate droplets departing from the condenser surface. This study presents a facile technique implemented to gain control of Dmax in DWC within vapor/air atmospheres. We demonstrate how this approach can enhance the corresponding heat transfer rate by harnessing the capillary forces in the removal of the condensate from the surface. We examine various hydrophilic-superhydrophilic patterns, which, respectively, sustain and combine DWC and filmwise condensation on the substrate. The material system uses laser-patterned masking and chemical etching to achieve the desired wettability contrast and does not employ any hydrophobizing agent. By applying alternating straight parallel strips of hydrophilic (contact angle ∼78°) mirror-finish aluminum and superhydrophilic regions (etched aluminum) on the condensing surface, we show that the average maximum droplet size on the less-wettable domains is nearly 42% of the width of the corresponding strips. An overall improvement in the condensate collection rate, up to 19% (as compared to the control case of DWC on mirror-finish aluminum) was achieved by using an interdigitated superhydrophilic track pattern (on the mirror-finish hydrophilic surface) inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern design, particularly under higher humidity conditions in the presence of noncondensable gases (NCG), a condition that is more challenging for maintaining sustained DWC. PMID:25295388

  19. Umpolung Reactions of α-Imino Esters: Useful Methods for the Preparation of α-Amino Acid Frameworks.

    PubMed

    Mizota, Isao; Shimizu, Makoto

    2016-04-01

    This paper summarizes our recent efforts toward the development of tandem reactions utilizing umpolung reactions of α-imino esters. A highly diastereoselective tandem N-alkylation-Mannich reaction of α-imino esters was developed. A tandem N-alkylation-addition reaction of α-imino esters derived from ethyl glyoxylate with various aldehydes proceeded to give 1,2-amino alcohols. The same reaction also proceeded efficiently using a novel flow system comprising two connected microreactors. Novel syntheses of α-quaternary alkynyl amino esters and allenoates were developed through the use of umpolung N-addition to β,γ-alkynyl α-imino esters, followed by regioselective acylation. In addition, a highly regioselective tandem N-alkylation-vinylogous aldol reaction of β,γ-alkenyl α-imino esters was discovered. N-Alkylation of α-iminophosphonates followed by a Horner-Wadsworth-Emmons reaction with aldehydes occurred to afford enamines, which can be used in a four-component coupling reaction with methyl vinyl ketone. α-N-Acyloxyimino esters served as highly efficient substrates for the N,N,C-trialkylation reaction to introduce various nucleophiles at the imino nitrogen and carbon atoms.

  20. Methylene-carbonyl condensations of some CH acids with aldehydes under the conditions of phase-transfer catalysis or catalysis by the fluoride ion

    SciTech Connect

    Beletskaya, I.P.; Gulyukina, N.S.; Muhamed Ali Ali; Solov'yanov, A.A.; Reutov, O.A.

    1987-09-10

    The condensation of a series of CH acids (fluorene, phenylacetonitrile, ethene) with aromatic aldehydes was realized in the aqueous sodium hydroxide-organic solvent-phase-transfer catalyst system. 9-Substituted fluorenesdo not enter into condensation under the indicated conditions. The condensation of fluorene, PhCH/sub 2/CN, CH/sub 2/(CN)/sub 2/, and CH/sub 2/(CN)COOEt with benzaldehyde and also of CH/sub 2/(CN)COOEt with cyclohexanone was realized in the presence of tetrabutylammonium fluoride, deposited on silica gel. It was shown that the yield of the product from crotonic condensation in the reaction of CH/sub 2/(COOEt)/sub 2/ with benzaldehyde is small, and this is due to the instability of PhCh = C(COOEt)/sub 2/ under the reaction conditions. Sodiomalonic ester was condensed with benzaldehyde in the presence of titanium tetrachloride or aluminum chloride.

  1. Chemical reaction equilibrium in nanoporous materials: NO dimerization reaction in carbon slit nanopores.

    PubMed

    Lísal, Martin; Brennan, John K; Smith, William R

    2006-02-14

    We present a molecular-level simulation study of the effects of confinement on chemical reaction equilibrium in nanoporous materials. We use the reaction ensemble Monte Carlo (RxMC) method to investigate the effects of temperature, nanopore size, bulk pressure, and capillary condensation on the nitric oxide dimerization reaction in a model carbon slit nanopore in equilibrium with a bulk reservoir. In addition to the RxMC simulations, we also utilize the molecular-dynamics method to determine self-diffusion coefficients for confined nonreactive mixtures of nitric oxide monomers and dimers at compositions obtained from the RxMC simulations. We analyze the effects of the temperature, nanopore width, bulk pressure, and capillary condensation on the reaction equilibrium with respect to the reaction conversion, fluid structure, and self-diffusion coefficients. We show that the influence of the temperature, nanopore size, and capillary condensation on the confined reaction equilibrium is quite dramatic while the effect of the bulk pressure on the reaction equilibrium in the carbon slit nanopore is only moderate. This work is an extension of previous work by Turner et al. [J. Chem. Phys. 114, 1851 (2001)] on the confined reactive nitric oxide system.

  2. Dropwise condensation dynamics in humid air

    NASA Astrophysics Data System (ADS)

    Castillo Chacon, Julian Eduardo

    Dropwise condensation of atmospheric water vapor is important in multiple practical engineering applications. The roles of environmental factors and surface morphology/chemistry on the condensation dynamics need to be better understood to enable efficient water-harvesting, dehumidication, and other psychrometric processes. Systems and surfaces that promote faster condensation rates and self-shedding of condensate droplets could lead to improved mass transfer rates and higher water yields in harvesting applications. The thesis presents the design and construction of an experimental facility that allows visualization of the condensation process as a function of relative humidity. Dropwise condensation experiments are performed on a vertically oriented, hydrophobic surface at a controlled relative humidity and surface subcooling temperature. The distribution and growth of water droplets are monitored across the surface at different relative humidities (45%, 50%, 55%, and 70%) at a constant surface subcooling temperature of 15 °C below the ambient temperature. The droplet growth dynamics exhibits a strong dependency on relative humidity in the early stages during which there is a large population of small droplets on the surface and single droplet growth dominates over coalescence effects. At later stages, the dynamics of droplet growth is insensitive to relative humidity due to the dominance of coalescence effects. The overall volumetric rate of condensation on the surface is also assessed as a function of time and ambient relative humidity. Low relative humidity conditions not only slow the absolute rate of condensation, but also prolong an initial transient regime over which the condensation rate remains significantly below the steady-state value. The current state-of-the-art in dropwise condensation research indicates the need for systematic experimental investigations as a function of relative humidity. The improved understanding of the relative humidity

  3. Quasihole condensates in quantum Hall liquids

    SciTech Connect

    Suorsa, J.; Viefers, S.; Hansson, T. H.

    2011-06-15

    We develop a formalism to describe quasihole condensates in quantum Hall liquids and thereby extend the conformal field theory approach to the full hierarchy of spin-polarized Abelian states and to several classes of non-Abelian hierarchical states. Most previously proposed spin-polarized quantum Hall wave functions appear as special cases. In this paper we explain the physical motivations for the approach, and exemplify it by explicitly constructing the level-two quasihole condensate state at filling fraction 2/3, and the two level-three states at 5/13 and 5/7 which are built from combinations of quasielectron and quasihole condensates.

  4. Vortices and turbulence in trapped atomic condensates

    PubMed Central

    White, Angela C.; Anderson, Brian P.; Bagnato, Vanderlei S.

    2014-01-01

    After more than a decade of experiments generating and studying the physics of quantized vortices in atomic gas Bose–Einstein condensates, research is beginning to focus on the roles of vortices in quantum turbulence, as well as other measures of quantum turbulence in atomic condensates. Such research directions have the potential to uncover new insights into quantum turbulence, vortices, and superfluidity and also explore the similarities and differences between quantum and classical turbulence in entirely new settings. Here we present a critical assessment of theoretical and experimental studies in this emerging field of quantum turbulence in atomic condensates. PMID:24704880

  5. Deconfinement Phase Transition and the Quark Condensate

    SciTech Connect

    Fischer, Christian S.

    2009-07-31

    We study the dual quark condensate as a signal for the confinement-deconfinement phase transition of QCD. This order parameter for center symmetry has been defined recently by Bilgici et al. within the framework of lattice QCD. In this work we determine the ordinary and the dual quark condensate with functional methods using a formulation of the Dyson-Schwinger equations for the quark propagator on a torus. The temperature dependence of these condensates serves to investigate the interplay between the chiral and deconfinement transitions of quenched QCD.

  6. Bose-Einstein condensation of erbium.

    PubMed

    Aikawa, K; Frisch, A; Mark, M; Baier, S; Rietzler, A; Grimm, R; Ferlaino, F

    2012-05-25

    We report on the achievement of Bose-Einstein condensation of erbium atoms and on the observation of magnetic Feshbach resonances at low magnetic fields. By means of evaporative cooling in an optical dipole trap, we produce pure condensates of 168Er, containing up to 7×10(4) atoms. Feshbach spectroscopy reveals an extraordinary rich loss spectrum with six loss resonances already in a narrow magnetic-field range up to 3 G. Finally, we demonstrate the application of a low-field Feshbach resonance to produce a tunable dipolar Bose-Einstein condensate and we observe its characteristic d-wave collapse. PMID:23003221

  7. Orbital diamagnetic susceptibility in excitonic condensation phase

    NASA Astrophysics Data System (ADS)

    Sugimoto, Koudai; Ohta, Yukinori

    2016-08-01

    We study the orbital diamagnetic susceptibility in excitonic condensation phase using the mean-field approximation for a two-band model defined on a square lattice. We find that, in semiconductors, the excitonic condensation acquires a finite diamagnetic susceptibility due to spontaneous hybridization between the valence and the conduction bands, whereas in semimetals, the diamagnetic susceptibility in the normal phase is suppressed by the excitonic condensation. We also study the orbital diamagnetic and Pauli paramagnetic susceptibilities of Ta2NiSe5 using a two-dimensional three-band model and find that the calculated temperature dependence of the magnetic susceptibility is in qualitative agreement with experiment.

  8. Preoperational test report, primary ventilation condensate system

    SciTech Connect

    Clifton, F.T.

    1997-01-29

    Preoperational test report for Primary Ventilation Condensate System, Project W-030. Project W-030 provides a ventilation upgrade for the four Aging Waste Facility tanks. The system provides a collection point for condensate generated by the W-030 primary vent offgas cooling system serving tanks AYIOI, AY102, AZIOI, AZI02. The system is located inside a shielded ventilation equipment cell and consists of a condensate seal pot, sampling features, a drain line to existing Catch Tank 241-AZ-151, and a cell sump jet pump. The tests verify correct system operation and correct indications displayed by the central Monitor and Control System.

  9. Open string decoupling and tachyon condensation

    NASA Astrophysics Data System (ADS)

    Chalmers, Gordon

    2001-06-01

    The amplitudes in perturbative open string theory are examined as functions of the tachyon condensate parameter. The boundary state formalism demonstrates the decoupling of the open string modes at the non-perturbative minima of the tachyon potential via a degeneration of open world-sheets and identifies an independence of the coupling constants gs and gYM at general values of the tachyon condensate. The closed string sector is generated at the quantum level; it is also generated at the classical level perturbatively through the condensation of propagating open string modes on the D-brane degrees of freedom.

  10. Baryonic condensates on the conifold

    NASA Astrophysics Data System (ADS)

    Benna, Marcus K.; Dymarsky, Anatoly; Klebanov, Igor R.

    2007-08-01

    We provide new evidence for the gauge/string duality between the baryonic branch of the cascading SU(k(M+1)) × SU(kM) gauge theory and a family of type IIB flux backgrounds based on warped products of the deformed conifold and Bbb R3,1. We show that a Euclidean D5-brane wrapping all six deformed conifold directions can be used to measure the baryon expectation values, and present arguments based on κ-symmetry and the equations of motion that identify the gauge bundles required to ensure worldvolume supersymmetry of this object. Furthermore, we investigate its coupling to the pseudoscalar and scalar modes associated with the phase and magnitude, respectively, of the baryon expectation value. We find that these massless modes perturb the Dirac-Born-Infeld and Chern-Simons terms of the D5-brane action in a way consistent with our identification of the baryonic condensates. We match the scaling dimension of the baryon operators computed from the D5-brane action with that found in the cascading gauge theory. We also derive and numerically evaluate an expression that describes the variation of the baryon expectation values along the supergravity dual of the baryonic branch.

  11. Process of treating gas condensate

    SciTech Connect

    Hitzel, H.

    1984-11-06

    The sewage consists of gas condensates from coal-gasifying plants and/or coal chemical plants and contains the anions SO/sub 4/--, SCN-, NO/sub 3/-, Cl- and F- in a total of at least 2 mval/l and contains organic matter corresponding to a chemical oxygen demand of at least 1000 mg/l. The sewage is passed through a biological purification stage, and a succeeding fine purification stage. In an anion exchanger, strong anions are exchanged with hydrogen carbonate ions. The water leaving the anion exchange stage has an alkalinity of at least 2 mval/l and is passed at least in part through a cation exchanger before the water is recycled to the sewage. The water which has left the anion exchanger may be used as cooling water in a cooling tower before or after the cation exchanger. Organic acids are used for regeneration in the cation exchanger and the regeneration eluate is added to the sewage which is to be treated in the biological purification stage.

  12. Condensation Processes in Astrophysical Environments

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A., III; Rietmeijer, Frans J. M.; Hill, Hugh G. M.

    2002-01-01

    Astrophysical systems present an intriguing set of challenges for laboratory chemists. Chemistry occurs in regions considered an excellent vacuum by laboratory standards and at temperatures that would vaporize laboratory equipment. Outflows around Asymptotic Giant Branch (AGB) stars have timescales ranging from seconds to weeks depending on the distance of the region of interest from the star and, on the way significant changes in the state variables are defined. The atmospheres in normal stars may only change significantly on several billion-year timescales. Most laboratory experiments carried out to understand astrophysical processes are not done at conditions that perfectly match the natural suite of state variables or timescales appropriate for natural conditions. Experimenters must make use of simple analog experiments that place limits on the behavior of natural systems, often extrapolating to lower-pressure and/or higher-temperature environments. Nevertheless, we argue that well-conceived experiments will often provide insights into astrophysical processes that are impossible to obtain through models or observations. This is especially true for complex chemical phenomena such as the formation and metamorphism of refractory grains under a range of astrophysical conditions. Data obtained in our laboratory has been surprising in numerous ways, ranging from the composition of the condensates to the thermal evolution of their spectral properties. None of this information could have been predicted from first principals and would not have been credible even if it had.

  13. Ice-condenser aerosol tests

    SciTech Connect

    Ligotke, M.W.; Eschbach, E.J.; Winegardner, W.K. )

    1991-09-01

    This report presents the results of an experimental investigation of aerosol particle transport and capture using a full-scale height and reduced-scale cross section test facility based on the design of the ice compartment of a pressurized water reactor (PWR) ice-condenser containment system. Results of 38 tests included thermal-hydraulic as well as aerosol particle data. Particle retention in the test section was greatly influenced by thermal-hydraulic and aerosol test parameters. Test-average decontamination factor (DF) ranged between 1.0 and 36 (retentions between {approximately}0 and 97.2%). The measured test-average particle retentions for tests without and with ice and steam ranged between DF = 1.0 and 2.2 and DF = 2.4 and 36, respectively. In order to apparent importance, parameters that caused particle retention in the test section in the presence of ice were steam mole fraction (SMF), noncondensible gas flow rate (residence time), particle solubility, and inlet particle size. Ice-basket section noncondensible flows greater than 0.1 m{sup 3}/s resulted in stable thermal stratification whereas flows less than 0.1 m{sup 3}/s resulted in thermal behavior termed meandering with frequent temperature crossovers between flow channels. 10 refs., 66 figs., 16 tabs.

  14. Diquark Bose-Einstein condensation

    SciTech Connect

    Nawa, K.; Nakano, E.; Yabu, H.

    2006-08-01

    Bose-Einstein condensation of composite diquarks in quark matter (the color superconductor phase) is discussed using the quasichemical equilibrium theory at a relatively low-density region near the deconfinement phase transition, where dynamical quark-pair fluctuations are assumed to be described as bosonic degrees of freedom (diquarks). A general formulation is given for the diquark formation and particle-antiparticle pair-creation processes in the relativistic framework, and some interesting properties are shown, which are characteristic for the relativistic many-body system. Behaviors of transition temperature and phase diagram of the quark-diquark matter are generally presented in model parameter space, and their asymptotic behaviors are also discussed. As an application to the color superconductivity, the transition temperatures and the quark and diquark density profiles are calculated in case with constituent/current quarks, where the diquark is in the bound/resonant state. We obtained T{sub C}{approx}60-80 MeV for constituent quarks and T{sub C}{approx}130 MeV for current quarks at a moderate density ({rho}{sub b}{approx}3{rho}{sub 0}). The method is also developed to include interdiquark interactions into the quasichemical equilibrium theory within a mean-field approximation, and it is found that a possible repulsive diquark-diquark interaction lowers the transition temperature by {approx}50%.

  15. Green chemistry approaches to the synthesis of 5-alkoxycarbonyl-4-aryl-3,4- dihydropyrimidin-2(1H)-ones by a three-component coupling of one-pot condensation reaction: comparison of ethanol, water, and solvent-free conditions.

    PubMed

    Bose, D Subhas; Fatima, Liyakat; Mereyala, Hari Babu

    2003-01-24

    A general and practical green chemistry route to the Biginelli cyclocondensation reaction using cerium(III) chloride as the catalyst (25% mol) is described under three different sets of reaction conditions. This method provides an efficient and much improved modification of original Biginelli reaction reported in 1893, in terms of high yields, short reaction times, and simple work-up procedure, and it has the ability to tolerate a wide variety of substitutions in all three components, which is lacking in existing procedures. PMID:12530887

  16. Role of quantum statistics in the photoassociation of Bose-Einstein condensates

    SciTech Connect

    Olsen, M. K.; Plimak, L. I.

    2003-09-01

    We show that the photoassociation of an atomic Bose-Einstein condensate to form condensed molecules is a chemical process which not only does not obey the Arrhenius rules for chemical reactions, but that it can also depend on the quantum statistics of the reactants. Comparing the predictions of a truncated Wigner representation for different initial quantum states, we find that, even when the quantum prediction for an initial coherent state is close to the Gross-Pitaevskii prediction, other quantum states may result in very different dynamics.

  17. Chemistry and kinetics of I2 loss in urine distillate and humidity condensate

    NASA Technical Reports Server (NTRS)

    Atwater, James E.; Wheeler, Richard R., Jr.; Olivadoti, J. T.; Sauer, Richard L.

    1992-01-01

    Time-resolved molecular absorption spectrophotometry of iodinated ersatz humidity condensates and iodinated ersatz urine distillates across the UV and visible spectral regions are used to investigate the chemistry and kinetics of I2 loss in urine distillate and humidity condensate. Single contaminant systems at equivalent concentrations are also employed to study rates of iodine. Pseudo-first order rate constants are identified for ersatz contaminant model mixtures and for individual reactive constituents. The second order bimolecular reaction of elemental iodine with formic acid, producing carbon dioxide and iodine anion, is identified as the primary mechanism underlying the decay of residual I2 in ersatz humidity concentrate.

  18. Non-equilibrium effects on the chemistry of nebular condensates - Implications for the planets and asteroids

    NASA Technical Reports Server (NTRS)

    Blander, M.

    1979-01-01

    Kinetic effects, for example nucleation constraints and slow reactions, should have been important in nebular condensation. Consideration of these effects leads to the prediction of pressure-dependent compositions and physical properties of nebular condensates which is consistent with (1) the differences between different classes of chondritic meteorites, (2) some of the differences between planets, and (3) the presence of oxidized iron on the moon and in the eucrite parent body (presumably an asteroid) despite the low abundance of volatiles. Diffusion effects appear to be important for understanding oxygen isotope anomalies in refractory inclusions in Allende. The consideration of kinetic effects leads to more information concerning nebular processes than if equilibrium is assumed.

  19. Magnons in a box: Condensation and Application

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Olf, Ryan; Wu, Shun; Kadau, Holger; Marti, G. Edward; Stamper-Kurn, Dan

    2016-05-01

    Ultracold gases offer us a remarkable window into the quantum world, allowing direct access to a wide range of manybody and condensed matter phenomena at convenient macroscopic length and time scales. However, producing ultracold gases at ever lower entropy, and measuring statistical properties such as temperature in these low entropy regimes, is a persistent challenge. Magnons, gapless spin excitations of spinor Bose Einstein Condensate (BEC), are expected to behave like free particles. We show that magnons can be used to cool BEC in a deep trap and serve as a thermometer to measure temperatures at extremely low entropy-per-particle. Unlike atoms trapped in a harmonic trap, trapped magnons experience a box potential due to near exact cancellation of the trapping potential by the mean-field interaction within the condensate. We observe the quasi-condensation of magnon excitations within this nature-made box.

  20. Performance investigation of finned tube condensers

    SciTech Connect

    Mathur, G.D.

    1996-12-31

    A computer program has been developed to optimize the performance of finned tube condensers. The developed program is used to predict the thermal and hydrodynamic performance of finned tube condensers. The model is based on a steady-state finite difference model. The correlations for predicting the heat transfer and pressure drop are used from the literature. In this paper, the performance of a condenser of a 2-1/2 ton residential air conditioning system (split type) is optimized. The working fluid used in this investigation is R-22. ASHRAE`s condition A [Outside 95 F DBT/75 F WBT; Inside 80 F/67 F WBT] is used in this investigation. The predicted performance of the condenser is within {+-}5% of the experimental data.

  1. Condenser design for AMTEC power conversion

    NASA Technical Reports Server (NTRS)

    Crowley, Christopher J.

    1991-01-01

    The condenser and the electrodes are the two elements of an alkali metal thermal-to-electric conversion (AMTEC) cell which most greatly affect the energy conversion performance. A condenser is described which accomplishes two critical functions in an AMTEC cell: management of the fluid under microgravity conditions and optimization of conversion efficiency. The first function is achieved via the use of a controlled surface shape, along with drainage grooves and arteries to collect the fluid. Capillary forces manage the fluid in microgravity and dominate hydrostatic effects on the ground so the device is ground-testable. The second function is achieved via a smooth film of highly reflective liquid sodium on the condensing surface, resulting in minimization of parasitic heat losses due to radiation heat transfer. Power conversion efficiencies of 25 percent to 30 percent are estimated with this condenser using present technology for the electrodes.

  2. Condensation of Chondrules: Conditions for "Fiery Rain"

    NASA Astrophysics Data System (ADS)

    Grossman, L.; Fedkin, A. V.

    2012-09-01

    Equilibrium calculations at total pressures ≥1 bar in systems with CI dust enrichments of 1000 relative to solar composition, yield condensate assemblages whose olivine and coexisting silicate liquid have compositions found in primitive chondrules.

  3. Insulate Steam Distribution and Condensate Return Lines

    SciTech Connect

    Not Available

    2006-01-01

    This revised ITP tip sheet on insulating steam distribution and condensate return lines provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.

  4. Recent developments in Bose-Einstein condensation

    SciTech Connect

    Kalman, G.

    1997-09-22

    This paper contains viewgraphs on developments on Bose-Einstein condensation. Some topics covered are: strongly coupled coulomb systems; standard response functions of the first and second kind; dynamical mean field theory; quasi localized charge approximation; and the main equations.

  5. Condensation Front Migration in a Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Davis, Sanford S.

    2004-01-01

    Condensation front dynamics are investigated in the mid-solar nebula region. A quasi-steady model of the evolving nebula is combined with equilibrium vapor pressure curves to determine evolutionary condensation fronts for selected species. These fronts are found to migrate inwards from the far-nebula to final positions during a period of 10(exp 7) years. The physical process governing this movement is a combination of local viscous heating and luminescent heating from the central star. Two luminescent heating models are used and their effects on the ultimate radial position of the condensation front are discussed. At first the fronts move much faster than the nebular accretion velocity, but after a time the accreting gas and dust overtakes the slowing condensation front.

  6. Cold condensation of dust in the ISM.

    PubMed

    Rouillé, Gaël; Jäger, Cornelia; Krasnokutski, Serge A; Krebsz, Melinda; Henning, Thomas

    2014-01-01

    The condensation of complex silicates with pyroxene and olivine composition under conditions prevailing in molecular clouds has been experimentally studied. For this purpose, molecular species comprising refractory elements were forced to accrete on cold substrates representing the cold surfaces of surviving dust grains in the interstellar medium. The efficient formation of amorphous and homogeneous magnesium iron silicates at temperatures of about 12 K has been monitored by IR spectroscopy. The gaseous precursors of such condensation processes in the interstellar medium are formed by erosion of dust grains in supernova shock waves. In the laboratory, we have evaporated glassy silicate dust analogs and embedded the released species in neon ice matrices that have been studied spectroscopically to identify the molecular precursors of the condensing solid silicates. A sound coincidence between the 10 microm band of the interstellar silicates and the 10 microm band of the low-temperature siliceous condensates can be noted.

  7. Accretion of Ghost Condensate by Black Holes

    SciTech Connect

    Frolov, A

    2004-06-02

    The intent of this letter is to point out that the accretion of a ghost condensate by black holes could be extremely efficient. We analyze steady-state spherically symmetric flows of the ghost fluid in the gravitational field of a Schwarzschild black hole and calculate the accretion rate. Unlike minimally coupled scalar field or quintessence, the accretion rate is set not by the cosmological energy density of the field, but by the energy scale of the ghost condensate theory. If hydrodynamical flow is established, it could be as high as tenth of a solar mass per second for 10MeV-scale ghost condensate accreting onto a stellar-sized black hole, which puts serious constraints on the parameters of the ghost condensate model.

  8. Kaon condensation in dense stellar matter

    SciTech Connect

    Lee, Chang-Hwan; Rho, M. |

    1995-03-01

    This article combines two talks given by the authors and is based on Works done in collaboration with G.E. Brown and D.P. Min on kaon condensation in dense baryonic medium treated in chiral perturbation theory using heavy-baryon formalism. It contains, in addition to what was recently published, astrophysical backgrounds for kaon condensation discussed by Brown and Bethe, a discussion on a renormalization-group analysis to meson condensation worked out together with H.K. Lee and S.J. Sin, and the recent results of K.M. Westerberg in the bound-state approach to the Skyrme model. Negatively charged kaons are predicted to condense at a critical density 2 {approx_lt} {rho}/{rho}o {approx_lt} 4, in the range to allow the intriguing new phenomena predicted by Brown and Bethe to take place in compact star matter.

  9. Spatial density oscillations in trapped dipolar condensates

    SciTech Connect

    Lu, H.-Y.; Zhang, J.-N.; Qiu, R.-Z.; Yi, S.; Lu, H.; Pu, H.

    2010-08-15

    We investigated the ground-state wave function and the free expansion of a trapped dipolar condensate. We find that dipolar interaction may induce both biconcave and dumbbell density profiles in the pancake- and cigar-shaped traps, respectively. In the parameter plane of the interaction strengths, the oscillating density profile in a harmonically trapped dipolar condensate occurs only when the interaction parameters fall into certain isolated areas. The relation between the positions of these areas and the trap geometry is explored. When a box potential is used to confine the condensate, spatial density oscillation becomes a generic feature. By studying the free expansion of the condensate with an oscillating density profile, we show that the spatial density oscillation is detectable from the time-of-flight image.

  10. Condensation and Hydrolysis - An Optical Problem?

    ERIC Educational Resources Information Center

    Kellett, N. C.; Johnstone, A. H.

    1974-01-01

    Recent surveys have shown that pupils find the topics of esterification and condensation difficult. Reasons for the difficulty are not clear. Described is research designed to determine where the difficulties were visual or conceptual in origin. (RH)

  11. Bose condensates and the atom laser

    NASA Astrophysics Data System (ADS)

    Andrews, Michael R.

    In this thesis, I describe four classes of studies of cold, dilute vapors of atomic sodium. The in-situ nondestructive observation of a Bose condensate is presented in the broader context of imaging a cold polarized cloud. Two condensates were made to interfere, and a rudimentary ``atom laser'' was demonstrated. Excitations of a condensate were imaged in- situ and nondestructively, opening up the field of real- time dynamical studies. A related study attempting (unsuccessfully) to create and detect superfluid currents and vortices is discussed. Lastly, Feshbach resonances were used to modify the interactions in a Bose condensate, and the scattering length was observed to vary by over a factor of ten. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  12. Cold condensation of dust in the ISM.

    PubMed

    Rouillé, Gaël; Jäger, Cornelia; Krasnokutski, Serge A; Krebsz, Melinda; Henning, Thomas

    2014-01-01

    The condensation of complex silicates with pyroxene and olivine composition under conditions prevailing in molecular clouds has been experimentally studied. For this purpose, molecular species comprising refractory elements were forced to accrete on cold substrates representing the cold surfaces of surviving dust grains in the interstellar medium. The efficient formation of amorphous and homogeneous magnesium iron silicates at temperatures of about 12 K has been monitored by IR spectroscopy. The gaseous precursors of such condensation processes in the interstellar medium are formed by erosion of dust grains in supernova shock waves. In the laboratory, we have evaporated glassy silicate dust analogs and embedded the released species in neon ice matrices that have been studied spectroscopically to identify the molecular precursors of the condensing solid silicates. A sound coincidence between the 10 microm band of the interstellar silicates and the 10 microm band of the low-temperature siliceous condensates can be noted. PMID:25302393

  13. Experimental simulation of the condensation and metamorphism of seasonal CO2 condensates under martian conditions.

    NASA Astrophysics Data System (ADS)

    Grisolle, F.; Schmitt, B.; Beck, P.; Philippe, S.; Brissaud, O.

    2014-04-01

    An experimental set-up, CARBON-IR, has been developed in order to perform the condensation and metamorphism of CO2 condensates in various controlled martian conditions at, or out of, equilibrium. The sample texture is monitored and near-infrared reflectance spectra are recorded. We present a first set of experiments aimed to simulate the formation of compact translucent slabs by condensation of CO2 gas, the metamorphism of CO2 snow, as well as their sublimation.

  14. Probing the excitation spectrum of polariton condensates

    SciTech Connect

    Wouters, Michiel; Carusotto, Iacopo

    2009-03-15

    We propose a four-wave mixing experiment to probe the elementary excitation spectrum of a nonequilibrium Bose-Einstein condensate of exciton-polaritons under nonresonant pumping. Analytical calculations based on mean-field theory show that this method is able to reveal the characteristic negative energy feature of the Bogoliubov dispersion. Numerical simulations including the finite spatial profile of the excitation laser spot and a weak disorder confirm the practical utility of the method for realistic condensates.

  15. Proceedings: 2003 EPRI Workshop on Condensate Polishing

    SciTech Connect

    2004-02-01

    Successful condensate polishing operations maintain control of ionic and particulate impurity transport to the pressurized water reactor (PWR) steam generator and the boiling water reactor (BWR) reactor and recirculation system, thus allowing the units to operate more reliably. This report contains the work presented at EPRI's 2003 Workshop on Condensate Polishing, where 30 papers were presented on current issues, research, and utility experiences involving polishing issues at both PWR and BWR units.

  16. Condensate polishers add operating reliability and flexibility

    SciTech Connect

    Layman, C.M.; Bennett, L.L.

    2008-08-15

    Many of today's advanced steam generators favour either an all-volatile treatment or oxygenated treatment chemistry programme, both of which require strict maintenance of an ultra-pure boiler fedwater ro condensate system. Those requirements are many times at odds with the lower-quality water sources, such as greywater, available for plant makeup and cooling water. Adding a condensate polisher can be a simple, cost-effective solution. 4 figs.

  17. Dynamic simulation recalls condensate piping event

    SciTech Connect

    Farrell, R.J.; Reneberg, K.O. ); Moy, H.C. )

    1994-05-01

    This article describes how experience gained from simulating and reconstructing a condensate piping event will be used by Consolidated Edison to analyze control system problems. A cooperative effort by Con Edison and the Chemical Engineering Department at Polytechnic University used modular modeling system to investigate the probable cause of a Con Edison condensate piping event. Con Edison commissioned the work to serve as a case study for the more general problem of control systems analysis using dynamic simulation and MMS.

  18. Silicate condensation in Mira variables

    NASA Astrophysics Data System (ADS)

    Gail, Hans-Peter; Scholz, Michael; Pucci, Annemarie

    2016-06-01

    Context. The formation of dust in winds of cool and highly evolved stars and the rate of injection of dust into the interstellar medium is not yet completely understood, despite the importance of the process for the evolution of stars and galaxies. This holds in particular for oxygen-rich stars, where it is still not known which process is responsible for the formation of the necessary seed particles of their silicate dust. Aims: We study whether the condensation of silicate dust in Mira envelopes could be caused by cluster formation by the abundant SiO molecules. Methods: We solve the dust nucleation and growth equations in the co-moving frame of a fixed mass element for a simplified model of the pulsational motions of matter in the outer layers of a Mira variable, which is guided by a numerical model for Mira pulsations. It is assumed that seed particles form through the clustering of SiO. The calculation of the nucleation rate is based on published experimental data. The quantity of dust formed is calculated via a moment method and the calculation of radiation pressure on dusty gas is based on a dirty silicate model. Results: Dust nucleation occurs in the model at the upper culmination of the trajectory of a gas parcel where it stays for a considerable time at low temperatures. Subsequent dust growth occurs during the descending part of the motion and continues after the next shock reversed motion. It is found that sufficient dust forms that radiation pressure exceeds the gravitational pull of the stars such that the mass element is finally driven out of the star. Conclusions: Nucleation of dust particles by clustering of the abundant SiO molecules could be the mechanism that triggers silicate dust formation in Miras.

  19. Implementation of non-condensable gases condensation suppression model into the WCOBRA/TRAC-TF2 LOCA safety evaluation code

    SciTech Connect

    Liao, J.; Cao, L.; Ohkawa, K.; Frepoli, C.

    2012-07-01

    The non-condensable gases condensation suppression model is important for a realistic LOCA safety analysis code. A condensation suppression model for direct contact condensation was previously developed by Westinghouse using first principles. The model is believed to be an accurate description of the direct contact condensation process in the presence of non-condensable gases. The Westinghouse condensation suppression model is further revised by applying a more physical model. The revised condensation suppression model is thus implemented into the WCOBRA/TRAC-TF2 LOCA safety evaluation code for both 3-D module (COBRA-TF) and 1-D module (TRAC-PF1). Parametric study using the revised Westinghouse condensation suppression model is conducted. Additionally, the performance of non-condensable gases condensation suppression model is examined in the ACHILLES (ISP-25) separate effects test and LOFT L2-5 (ISP-13) integral effects test. (authors)

  20. An Aerosol Condensation Model for Sulfur Trioxide

    SciTech Connect

    Grant, K E

    2008-02-07

    This document describes a model for condensation of sulfuric acid aerosol given an initial concentration and/or source of gaseous sulfur trioxide (e.g. fuming from oleum). The model includes the thermochemical effects on aerosol condensation and air parcel buoyancy. Condensation is assumed to occur heterogeneously onto a preexisting background aerosol distribution. The model development is both a revisiting of research initially presented at the Fall 2001 American Geophysical Union Meeting [1] and a further extension to provide new capabilities for current atmospheric dispersion modeling efforts [2]. Sulfuric acid is one of the most widely used of all industrial chemicals. In 1992, world consumption of sulfuric acid was 145 million metric tons, with 42.4 Mt (mega-tons) consumed in the United States [10]. In 2001, of 37.5 Mt consumed in the U.S., 74% went into producing phosphate fertilizers [11]. Another significant use is in mining industries. Lawuyi and Fingas [7] estimate that, in 1996, 68% of use was for fertilizers and 5.8% was for mining. They note that H{sub 2}SO{sub 4} use has been and should continue to be very stable. In the United States, the elimination of MTBE (methyl tertiary-butyl ether) and the use of ethanol for gasoline production are further increasing the demand for petroleum alkylate. Alkylate producers have a choice of either a hydrofluoric acid or sulfuric acid process. Both processes are widely used today. Concerns, however, over the safety or potential regulation of hydrofluoric acid are likely to result in most of the growth being for the sulfuric acid process, further increasing demand [11]. The implication of sulfuric acid being a pervasive industrial chemical is that transport is also pervasive. Often, this is in the form of oleum tankers, having around 30% free sulfur trioxide. Although sulfuric acid itself is not a volatile substance, fuming sulfuric acid (referred to as oleum) is [7], the volatile product being sulfur trioxide

  1. Condensation of the air-steam mixture in a vertical tube condenser

    NASA Astrophysics Data System (ADS)

    Havlík, Jan; Dlouhý, Tomáš

    2016-03-01

    This paper deals with the condensation of water vapour in the presence of non-condensable air. Experimental and theoretical solutions of this problem are presented here. A heat exchanger for the condensation of industrial waste steam containing infiltrated air was designed. The condenser consists of a bundle of vertical tubes in which the steam condenses as it flows downwards with cooling water flowing outside the tubes in the opposite direction. Experiments with pure steam and with mixtures of steam with added air were carried out to find the dependence of the condensation heat transfer coefficient (HTC) on the air concentration in the steam mixture. The experimental results were compared with the theoretical formulas describing the cases. The theoretical determination of the HTC is based on the Nusselt model of steam condensation on a vertical wall, where the analogy of heat and mass transfer is used to take into account the behaviour of air in a steam mixture during the condensation process. The resulting dependencies obtained from the experiments and obtained from the theoretical model have similar results. The significant decrease in the condensation HTC, which begins at very low air concentrations in a steam mixture, was confirmed.

  2. Wettability Patterning for Enhanced Dropwise Condensation

    NASA Astrophysics Data System (ADS)

    Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

    2014-11-01

    Dropwise condensation (DwC), in order to be sustainable, requires removal of the condensate droplets. This removal is frequently facilitated by gravity. The rate of DwC heat transfer depends strongly on the maximum departing droplet diameter. Based on wettability patterning, we present a facile technique designed to control the maximum droplet size in DwC within vapor/air atmospheres, and demonstrate how this approach can be used to enhance the corresponding heat transfer rate. We examine various hydrophilic-superhydrophilic patterns, which, respectively sustain DwC and filmwise (FwC) condensation on the substrate. The fabrication method does notemploy any hydrophobizing agent. By juxtaposing parallel lines of hydrophilic (CA ~ 78°) and superhydrophilic (CA ~ 0°) regions on the condensing surface, we create alternating domains of DwC and FwC. The average droplet size on the DwC domain is reduced by ~ 60% compared to the theoretical maximum, which corresponds to the line width. We compare heat transfer rate between unpatternend DwC surfaces and patterned DwC surfaces. Even after sacrificing 40% of condensing area, we achieve up to 20% improvement in condensate collection rate using an interdigitated superhydrophilic pattern, inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern, particularly under higher vapor loadings in an air/vapor ambient atmosphere. NSF STTR Grant 1331817 via NBD Nano.

  3. Numerical simulation of condensation on structured surfaces.

    PubMed

    Fu, Xiaowu; Yao, Zhaohui; Hao, Pengfei

    2014-11-25

    Condensation of liquid droplets on solid surfaces happens widely in nature and industrial processes. This phase-change phenomenon has great effect on the performance of some microfluidic devices. On the basis of micro- and nanotechnology, superhydrophobic structured surfaces can be well-fabricated. In this work, the nucleating and growth of droplets on different structured surfaces are investigated numerically. The dynamic behavior of droplets during the condensation is simulated by the multiphase lattice Boltzmann method (LBM), which has the ability to incorporate the microscopic interactions, including fluid-fluid interaction and fluid-surface interaction. The results by the LBM show that, besides the chemical properties of surfaces, the topography of structures on solid surfaces influences the condensation process. For superhydrophobic surfaces, the spacing and height of microridges have significant influence on the nucleation sites. This mechanism provides an effective way for prevention of wetting on surfaces in engineering applications. Moreover, it suggests a way to prevent ice formation on surfaces caused by the condensation of subcooled water. For hydrophilic surfaces, however, microstructures may be submerged by the liquid films adhering to the surfaces. In this case, microstructures will fail to control the condensation process. Our research provides an optimized way for designing surfaces for condensation in engineering systems.

  4. SUBSTELLAR-MASS CONDENSATIONS IN PRESTELLAR CORES

    SciTech Connect

    Nakamura, Fumitaka; Kawabe, Ryohei; Takakuwa, Shigehisa

    2012-10-20

    We present combined Submillimeter Array and single-dish images of the (sub)millimeter dust continuum emission toward two prestellar cores, SM1 and B2-N5, in the nearest star-cluster-forming region, {rho} Ophiuchus. Our combined images indicate that SM1 and B2-N5 consist of three and four condensations, respectively, with masses of 10{sup -2}-10{sup -1} M{sub Sun} and sizes of a few hundred AU. The individual condensations have mean densities of 10{sup 8}-10{sup 9} cm{sup -3} and the masses are comparable to or larger than the critical Bonner-Ebert mass, indicating that self-gravity plays an important role in the dynamical evolution of the condensations. The coalescence timescale of these condensations is estimated to be about 10{sup 4} yr, which is comparable to the local gravitational collapse timescale, suggesting that merging of the condensations, instead of accretion, plays an essential role in the star formation process. These results challenge the standard theory of star formation, where a single, rather featureless, prestellar core collapses to form at most a couple of condensations, each of which potentially evolves into a protostar that is surrounded by a rotating disk where planets are created.

  5. Numerical simulation of condensation on structured surfaces.

    PubMed

    Fu, Xiaowu; Yao, Zhaohui; Hao, Pengfei

    2014-11-25

    Condensation of liquid droplets on solid surfaces happens widely in nature and industrial processes. This phase-change phenomenon has great effect on the performance of some microfluidic devices. On the basis of micro- and nanotechnology, superhydrophobic structured surfaces can be well-fabricated. In this work, the nucleating and growth of droplets on different structured surfaces are investigated numerically. The dynamic behavior of droplets during the condensation is simulated by the multiphase lattice Boltzmann method (LBM), which has the ability to incorporate the microscopic interactions, including fluid-fluid interaction and fluid-surface interaction. The results by the LBM show that, besides the chemical properties of surfaces, the topography of structures on solid surfaces influences the condensation process. For superhydrophobic surfaces, the spacing and height of microridges have significant influence on the nucleation sites. This mechanism provides an effective way for prevention of wetting on surfaces in engineering applications. Moreover, it suggests a way to prevent ice formation on surfaces caused by the condensation of subcooled water. For hydrophilic surfaces, however, microstructures may be submerged by the liquid films adhering to the surfaces. In this case, microstructures will fail to control the condensation process. Our research provides an optimized way for designing surfaces for condensation in engineering systems. PMID:25347594

  6. A 1949 outbreak of Pontiac fever-like illness in steam condenser cleaners.

    PubMed

    Armstrong, C W; Miller, G B

    1985-01-01

    A 1949 outbreak of flu-like illness in steam-turbine condenser cleaners was investigated in 1979. Clinical and epidemiologic features matched those in previously described outbreaks of nonpneumonic legionellosis (Pontiac fever). Titers by indirect immunofluorescence using polyvalent Legionella pneumophila antigen were significantly higher for late convalescent-phase serum samples from condenser workers than for control serum samples submitted to the Centers for Disease Control. Three workers who had cleaned the condensers on several occasions had experienced recurrent illness associated with these operations, which might support the theory that nonpneumonic legionellosis is caused by an immune reaction to an inhaled antigen or bacterial toxin of L. pneumophila, rather than a true infection. PMID:3888124

  7. Infinite statistics condensate as a model of dark matter

    SciTech Connect

    Ebadi, Zahra; Mirza, Behrouz; Mohammadzadeh, Hosein E-mail: b.mirza@cc.iut.ac.ir

    2013-11-01

    In some models, dark matter is considered as a condensate bosonic system. In this paper, we prove that condensation is also possible for particles that obey infinite statistics and derive the critical condensation temperature. We argue that a condensed state of a gas of very weakly interacting particles obeying infinite statistics could be considered as a consistent model of dark matter.

  8. 46 CFR 56.50-35 - Condensate pumps.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Condensate pumps. 56.50-35 Section 56.50-35 Shipping... APPURTENANCES Design Requirements Pertaining to Specific Systems § 56.50-35 Condensate pumps. Two means shall be provided for discharging the condensate from the main condenser, one of which shall be...

  9. 46 CFR 56.50-35 - Condensate pumps.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Condensate pumps. 56.50-35 Section 56.50-35 Shipping... APPURTENANCES Design Requirements Pertaining to Specific Systems § 56.50-35 Condensate pumps. Two means shall be provided for discharging the condensate from the main condenser, one of which shall be...

  10. 46 CFR 56.50-35 - Condensate pumps.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Condensate pumps. 56.50-35 Section 56.50-35 Shipping... APPURTENANCES Design Requirements Pertaining to Specific Systems § 56.50-35 Condensate pumps. Two means shall be provided for discharging the condensate from the main condenser, one of which shall be...

  11. 46 CFR 56.50-35 - Condensate pumps.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Condensate pumps. 56.50-35 Section 56.50-35 Shipping... APPURTENANCES Design Requirements Pertaining to Specific Systems § 56.50-35 Condensate pumps. Two means shall be provided for discharging the condensate from the main condenser, one of which shall be...

  12. Condensation and Evaporation of Solar System Materials

    NASA Astrophysics Data System (ADS)

    Davis, A. M.; Richter, F. M.

    2003-12-01

    It is widely believed that the materials making up the solar system were derived from a nebular gas and dust cloud that went through an early high-temperature stage during which virtually all of the material was in the gas phase. At one time, it was thought that the entire inner solar nebula was hot, but it is now believed that most material was processed through regions where high temperatures were achieved. Certainly some material, such as presolar grains (cf., Mendybaev et al., 2002a), has never been exposed to high temperatures. As the system cooled, solids and perhaps liquids began to condense, but at some point the partially condensed materials became isolated from the remaining gas. Various lines of evidence support this view. At the largest scale, there is the observation that the Earth, Moon, Mars, and all chondritic meteorites except for the CI chondrites are depleted to varying degrees in the abundances of moderately volatile elements relative to bulk solar system composition. The CI chondrites reflect the bulk composition of the solar system for all but hydrogen, carbon, nitrogen, oxygen, and the rare gases, the most volatile elements (see Chapter 1.03; Palme et al., 1988; McDonough and Sun, 1995; Humayun and Cassen, 2000). The depletions in moderately volatile elements are, to a significant degree, correlated with condensation temperature, suggesting progressive removal of gas as condensation proceeded ( Cassen, 1996). Additional observations that can be explained by partial condensation are that various particularly primitive components of meteorites (e.g., calcium-, aluminum-rich refractory inclusions, and certain metal grains) have mineralogy and/or details of their chemical composition that are remarkably similar to what is calculated for equilibrium condensates from a solar composition gas. For example, the calcium-, aluminum-rich inclusions (CAIs) in chondritic meteorites have compositions very similar to that calculated for the first 5% of total

  13. Reactions of intermetallic clusters

    NASA Astrophysics Data System (ADS)

    Farley, R. W.; Castleman, A. W., Jr.

    1990-02-01

    Reaction of bismuth-alkali clusters with closed-shell HX acids provides insight into the structures, formation, and stabilities of these intermetallic species. HC1 and HI are observed to quantitatively strip BixNay and BixKy, respectively, of their alkali component, leaving bare bismuth clusters as the only bismuth-containing species detected. Product bismuth clusters exhibit the same distribution observed when pure bismuth is evaporated in the source. Though evaporated simultaneously from the same crucible, this suggests alkali atoms condense onto existing bismuth clusters and have negligible effect on their formation and consequent distribution. The indistinguishibility of reacted and pure bismuth cluster distributions further argues against the simple replacement of alkali atoms with hydrogen in these reactions. This is considered further evidence that the alkali atoms are external to the stable bismuth Zintl anionic structures. Reactivities of BixNay clusters with HC1 are estimated to lie between 3×10-13 for Bi4Na, to greater than 4×10-11 for clusters possessing large numbers of alkali atoms. Bare bismuth clusters are observed in separate experiments to react significantly more slowly with rates of 1-9×10-14 and exhibit little variation of reactivity with size. The bismuth clusters may thus be considered a relatively inert substrate upon which the alkali overlayer reacts.

  14. Dropwise condensation on superhydrophobic surfaces with two-tier roughness

    NASA Astrophysics Data System (ADS)

    Chen, Chuan-Hua; Cai, Qingjun; Tsai, Chialun; Chen, Chung-Lung; Xiong, Guangyong; Yu, Ying; Ren, Zhifeng

    2007-04-01

    Dropwise condensation can enhance heat transfer by an order of magnitude compared to film condensation. Superhydrophobicity appears ideal to promote continued dropwise condensation which requires rapid removal of condensate drops; however, such promotion has not been reported on engineered surfaces. This letter reports continuous dropwise condensation on a superhydrophobic surface with short carbon nanotubes deposited on micromachined posts, a two-tier texture mimicking lotus leaves. On such micro-/nanostructured surfaces, the condensate drops prefer the Cassie state which is thermodynamically more stable than the Wenzel state. With a hexadecanethiol coating, superhydrophobicity is retained during and after condensation and rapid drop removal is enabled.

  15. Sulfur condensation in Claus catalyst

    SciTech Connect

    Schoffs, G.R.

    1985-02-01

    The heterogeneous reactions in which catalyst deactivation by pore plugging occur are listed and include: coke formation in petroleum processing, especially hydrocracking and hydrodesulfurization catalysts; steam reforming and methnation catalysts; ammonia synthesis catalyst; and automobile exhause catalysts. The authors explain how the Claus process converts hydrogen sulfide produced by petroleum desulfurization units and gas treatment processes into elemental sulfur and water. More than 15 million tons of sulfur are recovered annually by this process. Commercial Claus plants appear to operate at thermodynamic equilibrium. Depending on the H2S content of the feed and the number of reactors, total H2S conversion to elemental sulfur can exceed 95%.

  16. Improved Cloud Condensation Nucleus Spectrometer

    NASA Technical Reports Server (NTRS)

    Leu, Ming-Taun

    2010-01-01

    An improved thermal-gradient cloud condensation nucleus spectrometer (CCNS) has been designed to provide several enhancements over prior thermal- gradient counters, including fast response and high-sensitivity detection covering a wide range of supersaturations. CCNSs are used in laboratory research on the relationships among aerosols, supersaturation of air, and the formation of clouds. The operational characteristics of prior counters are such that it takes long times to determine aerosol critical supersaturations. Hence, there is a need for a CCNS capable of rapid scanning through a wide range of supersaturations. The present improved CCNS satisfies this need. The improved thermal-gradient CCNS (see Figure 1) incorporates the following notable features: a) The main chamber is bounded on the top and bottom by parallel thick copper plates, which are joined by a thermally conductive vertical wall on one side and a thermally nonconductive wall on the opposite side. b) To establish a temperature gradient needed to establish a supersaturation gradient, water at two different regulated temperatures is pumped through tubes along the edges of the copper plates at the thermally-nonconductive-wall side. Figure 2 presents an example of temperature and supersaturation gradients for one combination of regulated temperatures at the thermally-nonconductive-wall edges of the copper plates. c) To enable measurement of the temperature gradient, ten thermocouples are cemented to the external surfaces of the copper plates (five on the top plate and five on the bottom plate), spaced at equal intervals along the width axis of the main chamber near the outlet end. d) Pieces of filter paper or cotton felt are cemented onto the interior surfaces of the copper plates and, prior to each experimental run, are saturated with water to establish a supersaturation field inside the main chamber. e) A flow of monodisperse aerosol and a dilution flow of humid air are introduced into the main

  17. Buckling condensation in constrained growth

    NASA Astrophysics Data System (ADS)

    Dervaux, Julien; Ben Amar, Martine

    2011-03-01

    The multiple complexities inherent to living objects have motivated the search for abiotic substitutes, able to mimic some of their relevant physical properties. Hydrogels provide a highly monitorable counterpart and have thus found many applications in medicine and bioengineering. Recently, it has been recognized that their ability to swell could be used to unravel some of the universal physical processes at work during biological growth. However, it is yet unknown how the microscopic distinctions between swelling and biological growth affect macroscopic changes (shape, stresses) induced by volume variations. To answer this question, we focus on a clinically motivated example of growth. Some solid tumors such as melanoma or glioblastoma undergo a shape transition during their evolution. This bifurcation appears when growth is confined at the periphery of the tumor and is concomitant with the transition from the avascular to the vascular stage of the tumor evolution. To model this phenomenon, we consider in this paper the deformation of an elastic ring enclosing a core of different stiffness. When the volume of the outer ring increases, the system develops a periodic instability. We consider two possible descriptions of the volume variation process: either by imposing a homogeneous volumetric strain (biological growth) or through migration of solvent molecules inside a solid network (swelling). For thin rings, both theories are in qualitative agreement. When the interior is soft, we predict the emergence of a large wavelength buckling. Upon increasing the stiffness of the inner disc, the wavelength of the instability decreases until a condensation of the buckles occurs at the free boundary. This short wavelength pattern is independent of the stiffness of the disc and is only limited by the presence of surface tension. For thicker rings, two scenarios emerge. When a volumetric strain is prescribed, compressive stresses accumulate in the vicinity of the core and the

  18. Mitotic chromosome condensation in vertebrates

    SciTech Connect

    Vagnarelli, Paola

    2012-07-15

    Work from several laboratories over the past 10-15 years has revealed that, within the interphase nucleus, chromosomes are organized into spatially distinct territories [T. Cremer, C. Cremer, Chromosome territories, nuclear architecture and gene regulation in mammalian cells, Nat. Rev. Genet. 2 (2001) 292-301 and T. Cremer, M. Cremer, S. Dietzel, S. Muller, I. Solovei, S. Fakan, Chromosome territories-a functional nuclear landscape, Curr. Opin. Cell Biol. 18 (2006) 307-316]. The overall compaction level and intranuclear location varies as a function of gene density for both entire chromosomes [J.A. Croft, J.M. Bridger, S. Boyle, P. Perry, P. Teague,W.A. Bickmore, Differences in the localization and morphology of chromosomes in the human nucleus, J. Cell Biol. 145 (1999) 1119-1131] and specific chromosomal regions [N.L. Mahy, P.E. Perry, S. Gilchrist, R.A. Baldock, W.A. Bickmore, Spatial organization of active and inactive genes and noncoding DNA within chromosome territories, J. Cell Biol. 157 (2002) 579-589] (Fig. 1A, A'). In prophase, when cyclin B activity reaches a high threshold, chromosome condensation occurs followed by Nuclear Envelope Breakdown (NEB) [1]. At this point vertebrate chromosomes appear as compact structures harboring an attachment point for the spindle microtubules physically recognizable as a primary constriction where the two sister chromatids are held together. The transition from an unshaped interphase chromosome to the highly structured mitotic chromosome (compare Figs. 1A and B) has fascinated researchers for several decades now; however a definite picture of how this process is achieved and regulated is not yet in our hands and it will require more investigation to comprehend the complete process. From a biochemical point of view a vertebrate mitotic chromosomes is composed of DNA, histone proteins (60%) and non-histone proteins (40%) [6]. I will discuss below what is known to date on the contribution of these two different classes of

  19. Enhanced tubes for steam condensers. Volume 1, Summary of condensation and fouling; Volume 2, Detailed study of steam condensation

    SciTech Connect

    Webb, R.L.; Chamra, L.; Jaber, H.

    1992-02-01

    Electric utility steam condensers typically use plain tubes made of titanium, stainless steel, or copper alloys. Approximately two-thirds of the total thermal resistance is on the water side of the plain tube. This program seeks to conceive and develop a tube geometry that has special enhancement geometries on the tube (water) side and the steam (shell) side. This ``enhanced`` tube geometry, will provide increased heat transfer coefficients. The enhanced tubes will allow the steam to condense at a lower temperature. The reduced condensing temperature will reduce the turbine heat rate, and increase the plant peak load capability. Water side fouling and fouling control is a very important consideration affecting the choice of the tube side enhancement. Hence, we have consciously considered fouling potential in our selection of the tube side surface geometry. Using appropriate correlations and theoretical models, we have designed condensation and water side surface geometries that will provide high performance and be cleanable using sponge ball cleaning. Commercial tube manufacturers have made the required tube geometries for test purposes. The heat transfer test program includes measurement of the condensation and water side heat transfer coefficients. Fouling tests are being run to measure the waterside fouling resistance, and to the test the ability of the sponge ball cleaning system to clean the tubes.

  20. Condensate and feedwater systems, pumps, and water chemistry. Volume seven

    SciTech Connect

    Not Available

    1986-01-01

    Subject matter includes condensate and feedwater systems (general features of condensate and feedwater systems, condenser hotwell level control, condensate flow, feedwater flow), pumps (principles of fluid flow, types of pumps, centrifugal pumps, positive displacement pumps, jet pumps, pump operating characteristics) and water chemistry (water chemistry fundamentals, corrosion, scaling, radiochemistry, water chemistry control processes, water pretreatment, PWR water chemistry, BWR water chemistry, condenser circulating water chemistry.