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Sample records for aldol condensation reactions

  1. Simultaneous Upgrading of Furanics and Phenolics through Hydroxyalkylation/Aldol Condensation Reactions.

    PubMed

    Bui, Tuong V; Sooknoi, Tawan; Resasco, Daniel E

    2017-04-10

    The simultaneous conversion of cyclopentanone and m-cresol has been investigated on a series of solid-acid catalysts. Both compounds are representative of biomass-derived streams. Cyclopentanone can be readily obtained from sugar-derived furfurals through Piancatelli rearrangement under reducing conditions. Cresol represents a family of phenolic compounds, typically obtained from the depolymerization of lignin. In the first biomass conversion strategy proposed here, furfural is converted in high yields and selectivity to cyclopentanone (CPO) over metal catalysts such as Pd-Fe/SiO2 at 600 psi (∼4.14 MPa) H2 and 150 °C. Subsequently, CPO and cresol are further converted through acid-catalyzed hydroxyalkylation. This C-C coupling reaction may be used to generate products in the molecular weight range that is appropriate for transportation fuels. As molecules beyond this range may be undesirable for fuel production, a catalyst with a suitable porous structure may be advantageous for controlling the product distribution in the desirable range. If Amberlyst resins were used as a catalyst, C12 -C24 products were obtained whereas when zeolites with smaller pore sizes were used, they selectively produced C10 products. Alternatively, CPO can undergo the acid-catalyzed self-aldol condensation to form C10 bicyclic adducts. As an illustration of the potential for practical implementation of this strategy for biofuel production, the long-chain oxygenates obtained from hydroxyalkylation/aldol condensation were successfully upgraded through hydrodeoxygenation to a mixture of linear alkanes and saturated cyclic hydrocarbons, which in practice would be direct drop-in components for transportation fuels. Aqueous acidic environments, which are typically encountered during the liquid-phase upgrading of bio-oils, would inhibit the efficiency of base-catalyzed processes. Therefore, the proposed acid-catalyzed upgrading strategy is advantageous for biomass conversion in terms of

  2. Theoretical insights into the sites and mechanisms for base catalyzed esterification and aldol condensation reactions over Cu.

    PubMed

    Neurock, Matthew; Tao, Zhiyuan; Chemburkar, Ashwin; Hibbitts, David D; Iglesia, Enrique

    2017-03-23

    Condensation and esterification are important catalytic routes in the conversion of polyols and oxygenates derived from biomass to fuels and chemical intermediates. Previous experimental studies show that alkanal, alkanol and hydrogen mixtures equilibrate over Cu/SiO2 and form surface alkoxides and alkanals that subsequently promote condensation and esterification reactions. First-principle density functional theory (DFT) calculations were carried out herein to elucidate the elementary paths and the corresponding energetics for the interconversion of propanal + H2 to propanol and the subsequent C-C and C-O bond formation paths involved in aldol condensation and esterification of these mixtures over model Cu surfaces. Propanal and hydrogen readily equilibrate with propanol via C-H and O-H addition steps to form surface propoxide intermediates and equilibrated propanal/propanol mixtures. Surface propoxides readily form via low energy paths involving a hydrogen addition to the electrophilic carbon center of the carbonyl of propanal or via a proton transfer from an adsorbed propanol to a vicinal propanal. The resulting propoxide withdraws electron density from the surface and behaves as a base catalyzing the activation of propanal and subsequent esterification and condensation reactions. These basic propoxides can readily abstract the acidic Cα-H of propanal to produce the CH3CH((-))CH2O* enolate, thus initiating aldol condensation. The enolate can subsequently react with a second adsorbed propanal to form a C-C bond and a β-alkoxide alkanal intermediate. The β-alkoxide alkanal can subsequently undergo facile hydride transfer to form the 2-formyl-3-pentanone intermediate that decarbonylates to give the 3-pentanone product. Cu is unique in that it rapidly catalyzes the decarbonylation of the C2n intermediates to form C2n-1 3-pentanone as the major product with very small yields of C2n products. This is likely due to the absence of Brønsted acid sites, present on

  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. 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…

  7. An Asymmetric Organocatalytic Quadruple Domino Reaction Employing a Vinylogous Friedel-Crafts/Michael/Michael/Aldol Condensation Sequence.

    PubMed

    Philipps, Arne R; Fritze, Lars; Erdmann, Nico; Enders, Dieter

    2015-04-02

    An organocatalytic quadruple cascade initiated by a Friedel-Crafts-type reaction is described. The (S)-diphenylprolinol trimethylsilyl ether catalyzed reaction yields highly functionalized cyclohexenecarbaldehydes bearing a 1,1-bis[4-(dialkylamino)phenyl]ethene moiety and three contiguous stereogenic centers. The reaction tolerates various functional groups and all products are obtained with very good diastereoselectivity and with virtually complete enantiomeric excess.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. One-pot lipase-catalyzed aldol reaction combination of in situ formed acetaldehyde.

    PubMed

    Wang, Na; Zhang, Wei; Zhou, Long-Hua; Deng, Qing-Feng; Xie, Zong-Bo; Yu, Xiao-Qi

    2013-12-01

    A facile tandem route to α,β-unsaturated aldehydes was developed by combining the two catalytic activities of the same enzyme in a one-pot strategy for the aldol reaction and in situ generation of acetaldehyde. Lipase from Mucor miehei was found to have conventional and promiscuous catalytic activities for the hydrolysis of vinyl acetate and aldol condensation with in situ formed acetaldehyde. The first reaction continuously provided material for the second reaction, which effectively reduced the volatilization loss, oxidation, and polymerization of acetaldehyde, as well as avoided a negative effect on the enzyme of excessive amounts of acetaldehyde. After optimizing the process, several substrates participated in the reaction and provided the target products in moderate to high yields using this single lipase-catalyzed one-pot biotransformation.

  13. 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

  14. 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

  15. 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…

  16. Discovery-Oriented Approach To Organic Synthesis: Tandem Aldol Condensation-Michael Addition Reactions. Identifying Diastereotopic Hydrogens in an Achiral Molecule by NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wachter-Jurcsak, Nanette; Reddin, Kendra

    2001-09-01

    We have found a beautiful example of anisochrony of diastereotopic acyclic methylene hydrogens in a symmetric diketone, synthesized by techniques traditionally performed in an introductory organic laboratory course. Synthesis of the diketone is high-yielding and easy to carry out, and the products can be directly isolated with a good degree of purity with no need of further manipulation. The reaction can be accomplished in a single laboratory session.

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

    PubMed

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

    2016-06-08

    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.

  18. Chiral picolylamines for Michael and aldol reactions: probing substrate boundaries.

    PubMed

    Nugent, Thomas C; Bibi, Ahtaram; Sadiq, Abdul; Shoaib, Mohammad; Umar, M Naveed; Tehrani, Foad N

    2012-12-14

    Here we report on inroads concerning increased substrate breadth via the picolylamine organocatalyst template, a vicinal chiral diamine based on a pyridine-primary amine motif. The addition of cyclohexanone to β-nitrostyrene has many catalyst solutions, but cyclopentanone and isobutyraldehyde additions continue to be challenging. PicAm-3 (10 mol%) readily allows the Michael addition of cyclopentanone or isobutyraldehyde (5.0 equiv.) to β-nitrostyrene derivatives. By contrast, PicAm-1 (7.0 mol%) is optimal for catalyzing the aldol reaction of cyclohexanone or cycloheptanone (3.3 equiv.) with aromatic aldehydes. Eighteen products are reported and for each reaction type new products are reported (4b-d, 9c). Very good yields and stereoselectivities are generally noted. The reactions, which require an acid additive, proceed via a transient chiral enamine and a mechanistic case is put forth for a bifunctional catalysis model.

  19. 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.

  20. 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.

  1. Aldol reactions in multicomponent reaction based domino pathways: a multipurpose enabling tool in heterocyclic chemistry.

    PubMed

    Xu, Zhigang; De Moliner, Fabio; Cappelli, Alexandra P; Hulme, Christopher

    2013-06-07

    The aldol reaction has been evaluated in combination with the Ugi multicomponent reaction to assemble richly decorated mono- and polycyclic systems via expeditious cascade pathways. A small collection of pyrrolinones was generated thereof, and the scarcely accessible pyridoquinoxalinedione scaffold was also prepared by designing an additional nucleophilic substitution step in this domino sequence requiring minimal operational effort.

  2. Picolylamine as an organocatalyst template for highly diastereo- and enantioselective aqueous aldol reactions.

    PubMed

    Nugent, Thomas C; Umar, M Naveed; Bibi, Ahtaram

    2010-09-21

    A pyridine based 1,2-diamine containing only one stereogenic center has been identified for fast aldol reactions (16-48 h). Using 2-5 mol% of (R)- or (S)-PicAm-2, cyclohexanone (3.3 equiv) readily undergoes aldol reactions with o-, m-, and p-substituted aromatic aldehyde partners (limiting reagent), including the poor electrophile 4-methylbenzaldehyde (95-99% ee). Furthermore, functionalized cyclic ketone substrates have been converted into four aldol products 9-12 using the lowest catalyst loading (5.0 mol%) to date with the highest yield and enantioselectivity.

  3. Enantioselective desymmetrization of prochiral cyclohexanone derivatives via the organocatalytic direct Aldol reaction.

    PubMed

    Jiang, Jun; He, Long; Luo, Shi-Wei; Cun, Lin-Feng; Gong, Liu-Zhu

    2007-02-21

    Asymmetric desymmetrization of 4-substituted cyclohexanones using proline amide-catalyzed direct aldol reaction afforded beta-hydroxyketones with three stereogenic centers in high enantioselectivities of up to >99% ee.

  4. 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.

  5. 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

    2015-10-02

    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%).

  6. A Tandem Michael-Aldol Reaction Sequence: An Undergraduate Research Organic Experiment.

    ERIC Educational Resources Information Center

    Coutlangus, Marilyn L.; And Others

    1989-01-01

    Presents a short reaction sequence that allows the student to determine by spectroscopic methods the constitution and stereochemistry of the reaction products. Reports the interpretations needed to illustrate the usefulness of the spectroscopic method. Notes the products of the Michael-Aldol reaction have not been reported in the literature. (MVL)

  7. Origins of Stereoselectivity of Chiral Vicinal Diamine-Catalyzed Aldol Reactions.

    PubMed

    Simon, Adam; Yeh, Alexander J; Lam, Yu-Hong; Houk, K N

    2016-12-16

    The sources of asymmetric induction in aldol reactions catalyzed by cinchona alkaloid-derived amines, and chiral vicinal diamines in general, have been determined by density functional theory calculations. Four vicinal diamine-catalyzed aldol reactions were examined. The cyclic transition states of these reactions involve nine-membered hydrogen-bonded rings in distinct conformations. Using nomenclature from eight-membered cycloalkanes, the heavy atoms of the low-energy transition states are in crown (chair-chair) and chair-boat conformations. The factors that control which of these are favored have been identified.

  8. Rhodium-catalysed hydroacylation or reductive aldol reactions: a ligand dependent switch of reactivity.

    PubMed

    Osborne, James D; Willis, Michael C

    2008-10-28

    The pathway for the combination of enones and beta-S-substituted aldehydes using Rh-catalysis can be switched between a hydroacylation reaction or a reductive aldol reaction by simple choice of the phosphine ligand; this catalyst controlled switch allows access to new ketone hydroacylation products; useful 1,4-diketone intermediates for the synthesis of N-, S- and O-heterocycles.

  9. Aldol Reactions in MCR-Based Domino Pathways: a Multipurpose Enabling Tool in Heterocyclic Chemistry

    PubMed Central

    Xu, Zhigang; De Moliner, Fabio; Cappelli, Alexandra P.

    2013-01-01

    The aldol reaction has been evaluated in combination with the Ugi multicomponent reaction to assemble richly decorated mono- and polycyclic systems via expeditious cascade pathways. A small collection of pyrrolinones was generated thereof, and the scarcely accessible pyridoquinoxalinedione scaffold was also prepared by designing an additional nucleophilic substitution step in this domino sequence requiring minimal operational effort. PMID:23718233

  10. Hammett correlation of nornicotine analogues in the aqueous aldol reaction: implications for green organocatalysis.

    PubMed

    Rogers, Claude J; Dickerson, Tobin J; Brogan, Andrew P; Janda, Kim D

    2005-04-29

    [reaction: see text] A series of meta- and para-substituted 2-arylpyrrolidines were synthesized and examined for their ability to catalyze an aqueous aldol reaction under buffered conditions. Kinetic analysis of arylpyrrolidine-catalyzed reactions displayed a linear Hammett correlation with rho = 1.14 (R(2) = 0.996), indicating that the reaction is accelerated by electron-withdrawing aryl rings. These results show promise for the development of a synthetically viable aqueous organo-catalyst.

  11. 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...

  12. Brønsted acid catalyzed asymmetric aldol reaction: a complementary approach to enamine catalysis.

    PubMed

    Pousse, Guillaume; Le Cavelier, Fabien; Humphreys, Luke; Rouden, Jacques; Blanchet, Jérôme

    2010-08-20

    A syn-enantioselective aldol reaction has been developed using Brønsted acid catalysis based on H(8)-BINOL-derived phosphoric acids. This method affords an efficient synthesis of various beta-hydroxy ketones, some of which could not be synthesized using enamine organocatalysis.

  13. Chitosan aerogel: a recyclable, heterogeneous organocatalyst for the asymmetric direct aldol reaction in water.

    PubMed

    Ricci, Alfredo; Bernardi, Luca; Gioia, Claudio; Vierucci, Simone; Robitzer, Mike; Quignard, Françoise

    2010-09-14

    Aerogel microspheres of chitosan, an abundant biopolymer obtained from marine crustaceans, have been successfully applied to catalyze the asymmetric aldol reaction in water, providing the products in high yields and with good stereoselectivity (up to 93% ee) and recyclability (up to 4 runs). Yields were favourably affected by additives such as DNP and stearic acid.

  14. 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...

  15. 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.

  16. 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.

  17. 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.

  18. Stereoselective titanium-mediated aldol reactions of a chiral lactate-derived ethyl ketone with ketones.

    PubMed

    Alcoberro, Sandra; Gómez-Palomino, Alejandro; Solà, Ricard; Romea, Pedro; Urpí, Fèlix; Font-Bardia, Mercè

    2014-01-17

    Aldol reactions of titanium enolates of lactate-derived ethyl ketone 1 with other ketones proceed in a very efficient and stereocontrolled manner provided that a further equivalent of TiCl4 is added to the reacting mixture. The scope of these reactions encompasses simple ketones such as acetone or cyclohexanone as well as other ketones that contain potential chelating groups such as pyruvate esters or α- and β-hydroxy ketones.

  19. Transition state models for probing stereoinduction in Evans chiral auxiliary-based asymmetric aldol reactions.

    PubMed

    Shinisha, C B; Sunoj, Raghavan B

    2010-09-08

    The use of chiral auxiliaries is one of the most fundamental protocols employed in asymmetric synthesis. In the present study, stereoselectivity-determining factors in a chiral auxiliary-based asymmetric aldol reaction promoted by TiCl(4) are investigated by using density functional theory methods. The aldol reaction between chiral titanium enolate [derived from Evans propionyl oxazolidinone (1a) and its variants oxazolidinethione (1b) and thiazolidinethione (1c)] and benzaldehyde is examined by using transition-state modeling. Different stereochemical possibilities for the addition of titanium enolates to aldehyde are compared. On the basis of the coordination of the carbonyl/thiocarbonyl group of the chiral auxiliary with titanium, both pathways involving nonchelated and chelated transition states (TSs) are considered. The computed relative energies of the stereoselectivity-determining C-C bond formation TSs in the nonchelated pathway, for both 1a and 1c, indicate a preference toward Evans syn aldol product. The presence of a ring carbonyl or thiocarbonyl group in the chiral auxiliary renders the formation of neutral TiCl(3)-enolate, which otherwise is energetically less favored as compared to the anionic TiCl(4)-enolate. Hence, under suitable conditions, the reaction between titanium enolate and aldehyde is expected to be viable through chelated TSs leading to the selective formation of non-Evans syn aldol product. Experimentally known high stereoselectivity toward Evans syn aldol product is effectively rationalized by using the larger energy differences between the corresponding diastereomeric TSs. In both chelated and nonchelated pathways, the attack by the less hindered face of the enolate on aldehyde through a chair-like TS with an equatorial disposition of the aldehydic substituent is identified as the preferred mode. The steric hindrance offered by the isopropyl group and the possible chelation are identified as the key reasons behind the interesting

  20. Accurate Reaction Enthalpies and Sources of Error in DFT Thermochemistry for Aldol, Mannich, and α-Aminoxylation Reactions

    NASA Astrophysics Data System (ADS)

    Wheeler, Steven E.; Moran, Antonio; Pieniazek, Susan N.; Houk, K. N.

    2009-08-01

    Enthalpies for bond-forming reactions that are subject to organocatalysis have been predicted using the high-accuracy CBS-QB3 model chemistry and six DFT functionals. Reaction enthalpies were decomposed into contributions from changes in bonding and other intramolecular effects via the hierarchy of homodesmotic reactions. The order of the reaction exothermicities (aldol < Mannich ≈ α-aminoxylation) arises primarily from changes in formal bond types mediated by contributions from secondary intramolecular interactions. In each of these reaction types, methyl substitution at the β- and γ-positions stabilizes the products relative to the unsubstituted case. The performance of six DFT functionals (B3LYP, B3PW91, B1B95, MPW1PW91, PBE1PBE, and M06-2X), MP2, and SCS-MP2 has been assessed for the prediction of these reaction enthalpies. Even though the PBE1PBE and M06-2X functionals perform well for the aldol and Mannich reactions, errors roughly double when these functionals are applied to the α-aminoxylation reactions. B3PW91 and B1B95, which offer modest accuracy for the aldol and Mannich reactions, yield reliable predictions for the two α-aminoxylation reactions. The excellent performance of the M06-2X and PBE1PBE functionals for aldol and Mannich reactions stems from the cancellation of sizable errors arising from inadequate descriptions of the underlying bond transformations and intramolecular interactions. SCS-MP2/cc-pVTZ performs most consistently across these three classes of reactions, although the reaction exothermicities are systematically underestimated by 1-3 kcal mol-1. Conventional MP2, when paired with the cc-pVTZ basis set, performs somewhat better than SCS-MP2 for some of these reactions, particularly the α-aminoxylations. Finally, the merits of benchmarking DFT functionals for the set of simple chemically meaningful transformations underlying all bond-forming reactions are discussed.

  1. Sc(III)-doped zeolites as new heterogeneous catalysts: mukaiyama aldol reaction.

    PubMed

    Olmos, Andrea; Alix, Aurélien; Sommer, Jean; Pale, Patrick

    2009-10-26

    Sc(III)-doped solids based on zeolite materials have been investigated for the first time as catalysts in organic synthesis. Sc(III)-USY zeolite proved to be a novel and very efficient heterogeneous catalyst for the Mukaiyama aldol reaction. This easy-to-prepare catalyst exhibited wide scope and compatibility with functional groups and is very simple to use, easy to remove (by simple filtration), and is recyclable (up to three times without loss of activity).

  2. Solvent-Induced Reversal of Activities between Two Closely Related Heterogeneous Catalysts in the Aldol Reaction

    SciTech Connect

    Kandel, Kapil; Althaus, Stacey M; Peeraphatdit, Chorthip; Kobayashi, Takeshi; Trewyn, Brian G; Pruski, Marek; Slowing, Igor I

    2013-01-11

    The relative rates of the aldol reaction catalyzed by supported primary and secondary amines can be inverted by 2 orders of magnitude, depending on the use of hexane or water as a solvent. Our analyses suggest that this dramatic shift in the catalytic behavior of the supported amines does not involve differences in reaction mechanism, but is caused by activation of imine to enamine equilibria and stabilization of iminium species. The effects of solvent polarity and acidity were found to be important to the performance of the catalytic reaction. This study highlights the critical role of solvent in multicomponent heterogeneous catalytic processes.

  3. Catalytic asymmetric aldol addition reactions of 3-fluoro-indolinone derived enolates.

    PubMed

    Zhang, Lijun; Zhang, Wenzhong; Mei, Haibo; Han, Jianlin; Soloshonok, Vadim A; Pan, Yi

    2017-01-04

    Reported herein is a Cu(i)/bisoxazoline ligand-catalyzed aldol reaction of unprotected tertiary enolates generated in situ from 3-(1,1-dihydroxy-2,2,2-trifluoroethyl)-substituted derivatives of 3-fluoro-2-oxindoles. A range of α-fluoro-β-aryl/hetaryl/alkyl-β-hydroxy-indolin-2-ones containing C-F quaternary stereogenic centers of high pharmaceutical importance were furnished in good yields and satisfactory diastereo- and enantioselectivities. The reactions were conducted under operationally convenient conditions and displayed wide substrate/functional group generality including unprotected N-H on the tertiary enolates, and aromatic, hetero-aromatic and aliphatic aldehydes.

  4. Preparation and characterization of Mg-Zr mixed oxide aerogels and their application as aldol condensation catalysts.

    PubMed

    Sádaba, Irantzu; Ojeda, Manuel; Mariscal, Rafael; Richards, Ryan; López Granados, Manuel

    2012-10-08

    A series of Mg-Zr mixed oxides with different nominal Mg/(Mg+Zr) atomic ratios, namely 0, 0.1, 0.2, 0.4, 0.85, and 1, is prepared by alcogel methodology and fundamental insights into the phases obtained and resulting active sites are studied. Characterization is performed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N(2) adsorption-desorption isotherms, and thermal and chemical analysis. Cubic Mg(x)Zr(1-x)O(2-x) solid solution, which results from the dissolution of Mg(2+) cations within the cubic ZrO(2) structure, is the main phase detected for the solids with theoretical Mg/(Mg+Zr) atomic ratio ≤0.4. In contrast, the cubic periclase (c-MgO) phase derived from hydroxynitrates or hydroxy precursors predominates in the solid with Mg/(Mg+Zr)=0.85. c-MgO is also incipiently detected in samples with Mg/(Mg+Zr)=0.2 and 0.4, but in these solids the c-MgO phase mostly arises from the segregation of Mg atoms out of the alcogel-derived c-Mg(x)Zr(1-x)O(2-x) phase during the calcination process, and therefore the species c-MgO and c-Mg(x)Zr(1-x)O(2-x) are in close contact. Regarding the intrinsic activity in furfural-acetone aldol condensation in the aqueous phase, these Mg-O-Zr sites located at the interface between c-Mg(x)Zr(1-x)O(2-x) and segregated c-MgO display a much larger intrinsic activity than the other noninterface sites that are present in these catalysts: Mg-O-Mg sites on c-MgO and Mg-O-Zr sites on c-Mg(x)Zr(1-x)O(2-x). The very active Mg-O-Zr sites rapidly deactivate in the furfural-acetone condensation due to the leaching of active phases, deposition of heavy hydrocarbonaceous compounds, and hydration of the c-MgO phase. Nonetheless, these Mg-Zr materials with very high specific surface areas would be suitable solid catalysts for other relevant reactions catalyzed by strong basic sites in nonaqueous environments.

  5. Bicyclic proline analogues as organocatalysts for stereoselective aldol reactions: an in silico DFT study.

    PubMed

    Shinisha, C B; Sunoj, Raghavan B

    2007-04-21

    Density functional theory has been employed in investigating the efficiency of a series of bicyclic analogues of proline as stereoselective organocatalysts for the aldol reaction. Three classes of conformationally restricted proline analogues, as part of either a [2.2.1] or [2.1.1] bicyclic framework, have been studied. Transition states for the stereoselective C-C bond formation between enamines derived from [2.2.1] and [2.1.1] bicyclic amino acids and p-nitrobenzaldehyde, leading to enantiomeric products, have been identified. Analysis of the transition state geometries revealed that the structural rigidity of catalysts, improved transition state organization as well as other weak interactions influence the relative stabilities of diastereomeric transition states and help contribute to the overall stereoselectivity in the aldol reaction. These bicyclic catalysts are predicted to be substantially more effective in improving the enantiomeric excess than the widely used organocatalyst proline. Enantiomeric excesses in the range 82-95% are predicted for these bicyclic catalysts when a sterically unbiased substrate such as p-nitrobenzaldehyde is employed for the asymmetric aldol reaction. More interestingly, introduction of substituents, as simple as a methyl group, at the ortho position of the aryl aldehyde bring about an increase in the enantiomeric excess to values greater than 98%. The reasons behind the vital energy separation between diastereomeric transition states has been rationalized with the help of a number of weak interactions such as intramolecular hydrogen bonding and Coulombic interactions operating on the transition states. These predictions could have wider implications for the rational design of improved organocatalysts for stereoselective carbon-carbon bond-forming reactions.

  6. Noninnocent role of N-methyl pyrrolidinone in thiazolidinethione-promoted asymmetric aldol reactions.

    PubMed

    Sreenithya, A; Sunoj, Raghavan B

    2012-11-16

    The origin of stereoselectivity in the reaction between α-azido titanium enolate derived from chiral auxiliary N-acyl thiazolidinethione and benzaldehyde is established using the DFT(B3LYP) method. A nonchelated transition state with N-methyl-2-pyrrolidinone (NMP) bound to a TiCl(3) enolate is found to be energetically the most preferred model responsible for the formation of an Evans syn aldol product. The TS model devoid of NMP, although of higher energy, is found to be successful in predicting the right stereochemical outcome.

  7. 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.

  8. Gallium(III)- and calcium(II)-catalyzed Meyer-Schuster rearrangements followed by intramolecular aldol condensation or endo-Michael addition.

    PubMed

    Presset, M; Michelet, B; Guillot, R; Bour, C; Bezzenine-Lafollée, S; Gandon, V

    2015-03-28

    The first gallium- and calcium-catalyzed Meyer-Schuster rearrangements are described. Under substrate control, the incipient conjugated ketones can be trapped intramolecularly by β-keto esters or amides to yield cyclic products after aldol condensation or endo-Michael addition. An interesting additive effect that promotes the latter tandem process with calcium has been found.

  9. 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.…

  10. 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

    Ignatenko, Vasily A; Han, Yong; Tochtrop, Gregory P

    2013-12-06

    In an effort to access biologically relevant chemical space, a complex natural product derived nonsymmetrical 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.

  11. Strong counteranion effects on the catalytic activity of cationic silicon Lewis acids in Mukaiyama aldol and Diels-Alder reactions.

    PubMed

    Hara, Kenji; Akiyama, Ryuto; Sawamura, Masaya

    2005-12-08

    [chemical reaction: see text]. A toluene-coordinated silyl borate, [Et3Si(toluene)]B(C6F5)4, demonstrated catalytic activities significantly higher than those of Me3SiOTf and Me3SiNTf2 in Mukaiyama aldol and Diels-Alder reactions.

  12. 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.

  13. 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.

  14. 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.

  15. Organocatalytic Asymmetric Synthesis of Functionalized 1,3,5-Triarylpyrrolidin-2-ones via an Aza-Michael/Aldol Domino Reaction

    PubMed Central

    Joie, Céline; Deckers, Kristina; Enders, Dieter

    2014-01-01

    The organocatalytic asymmetric synthesis of functionalized 1,3,5-triarylpyrrolidin-2-ones bearing three contiguous stereocenters through an aza-Michael/aldol domino reaction of α-ketoamides with α,β-unsaturated aldehydes is described. The domino products were further derivatized by aldehyde olefination under one-pot conditions. The reaction proceeds with excellent diastereoselectivities (>20:1) and good to excellent enantioselectivities (60–96% ee). PMID:25278634

  16. 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.

  17. Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation.

    PubMed

    Malik, Michał; Jarosz, Sławomir

    2016-01-01

    Synthesis of novel polyhydroxylated derivatives of decalin is described. The presented methodology consists in a one-pot copper-catalyzed 1,4-addition of vinylmagnesium bromide to sugar-derived cyclohexenone, followed by an aldol reaction with a derivative of but-3-enal. The obtained diene is then subjected to an assisted tandem catalytic sequence: ring-closing metathesis with the subsequent reuse of the Ru-catalyst in the syn-dihydroxylation. The stereochemical outcome of these reactions is discussed.

  18. Asymmetric synthesis of dihydropyranones from ynones by sequential copper(I)-catalyzed direct aldol and silver(I)-catalyzed oxy-Michael reactions.

    PubMed

    Shi, Shi-Liang; Kanai, Motomu; Shibasaki, Masakatsu

    2012-04-16

    Ynones as diene surrogates: the asymmetric synthesis of enantiomerically enriched substituted dihydropyranones is described. The products are obtained in two steps by a copper(I)-catalyzed direct aldol reaction of ynones followed by a silver-catalyzed oxy-Michael reaction. This easy method is compatible with both aromatic and aliphatic substrates, and provides excellent chemoselectivity under mild reaction conditions.

  19. 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.

  20. Improving the Catalytic Performance of (S)-Proline as Organocatalyst in Asymmetric Aldol Reactions in the Presence of Solvate Ionic Liquids: Involvement of a Supramolecular Aggregate.

    PubMed

    Obregón-Zúñiga, Arturo; Milán, Mario; Juaristi, Eusebio

    2017-03-03

    For the first time, a highly efficient and stereoselective asymmetric aldol reaction employing (S)-proline in the presence of solvate ionic liquids is reported. The reaction seems to proceed via a supramolecular aggregate of (S)-proline, the solvate ionic liquid, and water, affording high yields and excellent stereoselectivities with low catalyst loadings.

  1. An Aldol Reaction-Based Iridium(III) Chemosensor for the Visualization of Proline in Living Cells

    NASA Astrophysics Data System (ADS)

    Liu, Jin-Biao; Liu, Li-Juan; Dong, Zhen-Zhen; Yang, Guan-Jun; Leung, Chung-Hang; Ma, Dik-Lung

    2016-11-01

    A long-lived aldol reaction-based iridium(III) chemosensor [Ir(ppy)2(5-CHOphen)]PF6 (1, where ppy = 2-phenylpyridine and 5-CHOphen = 1,10-phenanthroline-5-carbaldehyde) for proline detection has been synthesized. The iridium(III) complex 1, incorporating an aldehyde group in N^N donor ligand, can take part in aldol reaction with acetone mediated by proline. The transformation of the sp2-hybridized carbonyl group into a sp3-hybridized alcohol group influences the metal-to-ligand charge-transfer (MLCT) state of the iridium(III) complex, resulting in a change in luminescence in response to proline. The interaction of the iridium(III) complex 1 with proline was investigated by 1H NMR, HRMS and emission titration experiments. Upon the addition of proline to a solution of iridium(III) complex 1, a maximum 8-fold luminescence enhancement was observed. The luminescence signal of iridium(III) complex 1 could be recognized in strongly fluorescent media using time-resolved emission spectroscopy (TRES). The detection of proline in living cells was also demonstrated.

  2. Equilibrium between a vinylogous ylide and a phosphonium dienolate zwitterion: vinylogous Wittig olefination versus vinylogous aldol-type reaction

    PubMed Central

    Khong, San N.; Tran, Yang S.; Kwon, Ohyun

    2010-01-01

    This paper describes the equilibrium established between a phosphonium dienolate zwitterion and a vinylogous phosphorus ylide, and their reactions with aldehydes. The reactions between ethyl 2-methyl-2,3-butadienoate and various aldehydes occur through either a phosphonium dienolate or a vinylogous ylide intermediate, depending on the presence/absence of a Lewis acid and the nature of the phosphine. We observed a rare vinylogous Wittig olefination from the reaction between ethyl 2-methyl-2,3-butadienoate and an electron-deficient aromatic aldehyde in the presence of a stoichiometric amount of an electron-deficient triarylphosphine and a catalytic amount of a Lewis acid (e.g., BF3·Et2O). On the other hand, the use of triphenylphosphine, in the absence of a Lewis acid, facilitated vinylogous aldol addition, accompanied by a rare 1,2-aryl phosphorus-to-carbon migration. PMID:21359169

  3. Chiral bis(oxazoline) copper(II) complexes: versatile catalysts for enantioselective cycloaddition, Aldol, Michael, and carbonyl ene reactions.

    PubMed

    Johnson, J S; Evans, D A

    2000-06-01

    A bis(oxazoline) (box) copper(II) complex and its hydrated counterpart (1 and 2) function as enantioselective Lewis acid catalysts for carbocyclic and hetero Diels-Alder, aldol, Michael, ene, and amination reactions with substrates capable of chelation through six- and five-membered rings. X-ray crystallography of the chiral complexes reveals a propensity for the formation of distorted square planar or square pyramidal geometries. The sense of asymmetric induction is identical for all the processes catalyzed by [Cu((S,S)-t-Bu-box)](X)(2) complexes 1 and 2 (X = OTf and SbF) resulting from the intervention of a distorted square planar catalyst-substrate binary complex. These catalyzed processes exhibit excellent temperature-selectivity profiles. Reactions catalyzed by [Cu(S,S-Ph-pybox)](SbF(6))(2) and their derived chelation complexes are also discussed.

  4. TANDEM BIS-ALDOL REACTION OF KETONES: A FACILE ONE-POT SYNTHESIS OF 1,3-DIOXANES IN AQUEOUS MEDIUM

    EPA Science Inventory

    A novel tandem bis-aldol reaction of ketone with paraformaldehyde catalyzed by polystyrenesulfonic acid in aqueous medium delivers 1,3-dioxanes in high yield. This one pot, operationally simple microwave-assisted synthetic protocol proceeds efficiently in water in the absence of ...

  5. Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

    PubMed Central

    2016-01-01

    Synthesis of novel polyhydroxylated derivatives of decalin is described. The presented methodology consists in a one-pot copper-catalyzed 1,4-addition of vinylmagnesium bromide to sugar-derived cyclohexenone, followed by an aldol reaction with a derivative of but-3-enal. The obtained diene is then subjected to an assisted tandem catalytic sequence: ring-closing metathesis with the subsequent reuse of the Ru-catalyst in the syn-dihydroxylation. The stereochemical outcome of these reactions is discussed. PMID:28144329

  6. Organocatalyzed aldol reaction between pyridine-2-carbaldehydes and α-ketoacids: a straightforward route towards indolizidines and isotetronic acids.

    PubMed

    Liautard, Virginie; Jardel, Damien; Davies, Clotilde; Berlande, Muriel; Buffeteau, Thierry; Cavagnat, Dominique; Robert, Frédéric; Vincent, Jean-Marc; Landais, Yannick

    2013-10-18

    Enantioselective aldol reactions between substituted pyridine carbaldehydes and α-ketoacids were shown to provide isotetronic acids or their corresponding pyridinium salts, depending on the nature of the substituents on the pyridine ring. The pyridinium salts were generated through nucleophilic attack of the pyridine nitrogen atom onto the reactive keto functional group. Moderate-to-good yields of both compounds were typically obtained and high levels of enantioselectivity were observed by using benzimidazole pyrrolidine I as a catalyst. Hydrogenation of the resulting pyridinium salts led to new indolizidines with high ee values and diastereocontrol. X-ray diffraction studies allowed the determination of the relative configuration of the products. Finally, DFT calculations were performed to rationalize the divergent pathway as a function of the pyridine substituents.

  7. 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.

  8. 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

    2016-09-02

    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.

  9. 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.

  10. 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

  11. Isotope Probing of the UDP‐Apiose/UDP‐Xylose Synthase Reaction: Evidence of a Mechanism via a Coupled Oxidation and Aldol Cleavage

    PubMed Central

    Eixelsberger, Thomas; Horvat, Doroteja; Gutmann, Alexander; Weber, Hansjörg

    2017-01-01

    Abstract The C‐branched sugar d‐apiose (Api) is essential for plant cell‐wall development. An enzyme‐catalyzed decarboxylation/pyranoside ring‐contraction reaction leads from UDP‐α‐d‐glucuronic acid (UDP‐GlcA) to the Api precursor UDP‐α‐d‐apiose (UDP‐Api). We examined the mechanism of UDP‐Api/UDP‐α‐d‐xylose synthase (UAXS) with site‐selectively 2H‐labeled and deoxygenated substrates. The analogue UDP‐2‐deoxy‐GlcA, which prevents C‐2/C‐3 aldol cleavage as the plausible initiating step of pyranoside‐to‐furanoside conversion, did not give the corresponding Api product. Kinetic isotope effects (KIEs) support an UAXS mechanism in which substrate oxidation by enzyme‐NAD+ and retro‐aldol sugar ring‐opening occur coupled in a single rate‐limiting step leading to decarboxylation. Rearrangement and ring‐contracting aldol addition in an open‐chain intermediate then give the UDP‐Api aldehyde, which is intercepted via reduction by enzyme‐NADH. PMID:28102965

  12. Selective Fluorescence Detection of Cysteine over Homocysteine and Glutathione Based on a Cysteine-Triggered Dual Michael Addition/Retro-aza-aldol Cascade Reaction.

    PubMed

    Liu, Yawei; Lv, Xin; Hou, Min; Shi, Yawei; Guo, Wei

    2015-11-17

    In this work, a cysteine (Cys)-triggered dual Michael addition/retro-aza-aldol cascade reaction has been exploited and utilized to construct a fluorescent probe for Cys for the first time. The resulting fluorescent probe 8-alkynylBodipy 1 contains an activated alkynyl unit as Michael receptor and a Bodipy dye as fluorescence reporter and can highly selectively detect Cys over homocysteine (Hcy)/glutathione (GSH) as well as other amino acids with a significant fluorescence off-on response (∼4500-fold) and an ultralow detection limit (0.38 nM). The high selectivity of 1 for Cys could be attributed to a kinetically favored five-membered cyclic intermediate produced by the dual Michael addition of Cys with the activated alkynyl unit of 1. The big fluorescence off-on response is due to the subsequent retro-aza-aldol reaction of the five-membered cyclic intermediate that results in the release of a highly fluorescent 8-methylBodipy dye 2. The probe has been successfully used to detect and image Cys in serum and cells, respectively.

  13. Hydrolysis/dehydration/aldol-condensation/hydrogenation of lignocellulosic biomass and biomass-derived carbohydrates in the presence of Pd/WO3-ZrO2 in a single reactor.

    PubMed

    Dedsuksophon, W; Faungnawakij, K; Champreda, V; Laosiripojana, N

    2011-01-01

    Hydrolysis/dehydration/aldol-condensation/hydrogenation of lignocellulosic-biomass (corncobs) and biomass-derived carbohydrates (tapioca flour) to produce water-soluble C5-C15 compounds was developed in a single reactor system. WO3-ZrO2 efficiently catalyzed the hydrolysis/dehydration of these feedstocks to 5-hydroxymethylfurfural and furfural, while the impregnation of WO3-ZrO2 with Pd allowed sequential aldolcondensation/hydrogenation of these furans to C5-C15 compounds. The highest C5-C15 yields of 14.8-20.3% were observed at a hydrolysis/dehydration temperature of 573 K for 5 min, an aldol-condensation temperature of 353 K for 30 h, and a hydrogenation temperature of 393 K for 6 h. The C5-C15 yield from tapioca flour was higher than that from corncobs (20.3% compared to 14.8%). Tapioca flour produced more C6/C9/C15, whereas corncobs generated more C5/C8/C13 compounds due to the presence of hemicellulose in the corncobs. These water-soluble organic compounds can be further converted to liquid alkanes with high cetane numbers for replacing diesel fuel in transportation applications.

  14. 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.

  15. Multicomponent Condensation Reactions via ortho-Quinone Methides.

    PubMed

    Allen, Emily E; Zhu, Calvin; Panek, James S; Schaus, Scott E

    2017-03-30

    Iron(III) salts promote the condensation of aldehydes or acetals with electron-rich phenols to generate ortho-quinone methides that undergo Diels-Alder condensations with alkenes. The reaction sequence occurs in a single vessel to afford benzopyrans in up to 95% yield. The reaction was discovered while investigating a two-component strategy using 2-(hydroxy(phenyl)methyl)phenols to access the desired ortho-quinone methide in a Diels-Alder condensation. The two-component condensation also afforded the corresponding benzopyran products in yields up to 97%. Taken together, the two- and three-component strategies using ortho-quinone methide intermediates provide efficient access to benzopyrans in good yields and selectivities.

  16. rac-9-ethyl-12a-hydroxytetradecahydrotriphenylene-1,5(2H,4bH)-dione: stabilization of a new isomer of a functionalized perhydrotriphenylene through a tandem Michael addition-aldol reaction.

    PubMed

    García, Luis Arturo; Bernès, Sylvain; Anaya de Parrodi, Cecilia

    2008-06-01

    The title compound, C20H30O3, is a new functionalized perhydrotriphenylene derivative formed via a tandem Michael addition-aldol reaction. The structural study reveals that the system of fused rings approximates a C2 point symmetry, with trans-cis-cis ring junctions, while highly symmetric all-trans perhydrotriphenylene, previously characterized, approximates a D3 symmetry. The perhydrotriphenylene nucleus of the title compound corresponds to the third stable stereoisomer isolated for this polycyclic system. Considering that the C(s) isomer was obtained recently through a similar tandem reaction, a general strategy is proposed which may help to obtain other stable stereoisomers of perhydrotriphenylene.

  17. 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).

  18. 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…

  19. Bis(oxazoline) Lewis acid catalyzed aldol reactions of pyridine N-oxide aldehydes--synthesis of optically active 2-(1-hydroxyalkyl)pyridine derivatives: development, scope, and total synthesis of an indolizine alkaloid.

    PubMed

    Landa, Aitor; Minkkilä, Anna; Blay, Gonzalo; Jørgensen, Karl Anker

    2006-04-24

    A new, short, and simplified procedure for the synthesis of optically active pyridine derivatives from pro-chiral pyridine-N-oxides is presented. The catalytic and asymmetric Mukaiyama aldol reaction between ketene silyl acetals and 1-oxypyridine-2-carbaldehyde derivatives catalyzed by chiral copper(II)-bis(oxazoline) complexes gave optically active 2-(hydroxyalkyl)- and 2-(anti-1,2-dihydroxyalkyl)pyridine derivatives in good yields and diastereoselectivities, and in excellent enantioselectivities-up to 99 % enantiomeric excess. As a synthetic application of the developed method, a full account for the asymmetric total synthesis of a nonnatural indolizine alkaloid is provided.

  20. Modeling reaction fronts of separated condensed phase reactants

    NASA Astrophysics Data System (ADS)

    Koundinyan, Sushilkumar; Stewart, D. Scott; Matalon, Moshe

    2017-01-01

    We present a Gibbs free energy approach to modeling reaction fronts in condensed phase reactive materials. The current interest is in chemical reactions of condensed phase reactants that are initially separated. In energetic materials such reactions are observed to occur extremely fast and at relatively sharp fronts. The condensed phase combustion process differs in several aspects from classical gaseous combustion due to the disparity between the characteristic thermal conductivity length and the mass diffusion lengths and a volume, temperature, stress, mass fraction equation of state that principally depends only on the component reference volumes and the current mixture composition. To retain a simple planar configuration, we consider the two reactants, in solid phase, are in motion towards each other characterized by counter-flow geometry. We apply the model to a simplified Titanium-Boron system and present the analysis of reaction zone length for various strain rates. The numerical results are validated with asymptotic approximations at the Burke-Schumann (complete combustion) limit.

  1. 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

  2. Shock-Induced Chemical Reactions in Condensed Matter.

    DTIC Science & Technology

    1982-08-01

    Technical, 4/1/78 - 6/30/82 Matter 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(s) S. CONTRACT OR GRANT NUMUER(e) George E. Duvall, Principal Investigator...CHEMICAL REACTIONS IN CONDENSED MATTER George E. Duvall, Principal Investigator Stephen A. Sheffield* Kendal M. OgilvieT 4 C. Robert Wilson Paul...Temperture," in Sixth Symposium (International on Detonation (Office of Naval Research, Arlington, 1976), ACR-Z21, p. 36. 24. G. Gamow , "Tentative

  3. Modeling reaction fronts of separated condensed phase reactants

    NASA Astrophysics Data System (ADS)

    Koundinyan, Sushilkumar; Matalon, Moshe; Stewart, D. Scott; Bdzil, John

    2015-06-01

    We present a Gibbs free energy approach to modeling reaction fronts in condensed phase reactive materials. The current interest is in chemical reactions of condensed phase reactants that are initially separated. In energetic materials such reactions are observed to occur extremely fast and at relatively sharp fronts. The solid-to-solid combustion process differs in several aspects from classical gaseous combustion due to the disparity between the characteristic thermal conductivity length and the mass diffusion lengths and a volume, temperature, stress, mass fraction equation of state that principally depends only on the component reference volumes and the current mixture composition. To retain a simple planar configuration, we consider the two reactants, in solid phase, are in motion towards each other characterized by counter-flow geometry. We apply the model to a simplified Titanium-Boron system and present the analysis of reaction zone length for various strain rates. The numerical results are validated with asymptotic approximations at the Burke-Schumann limit. Supported by HDTRA1-10-1-0020 (DTRA), AF Sub MO C00039417-1 (AFOSR/TRE).

  4. The pivotal role of chelation as a stereochemical control element in non-Evans anti aldol product formation.

    PubMed

    Shinisha, C B; Sunoj, Raghavan B

    2010-06-18

    The origin of stereoselective formation of Evans syn and non-Evans anti aldol products in the reaction between titanium enolate derived from N-succinyloxazolidinone and benzaldehyde is established by using transition-state modeling. The chelated transition-state model is found to hold the key to otherwise less likely non-Evans anti aldol product, whereas the nonchelated model offers a convincing rationalization toward Evans syn aldol product. The computed results are in agreement with the reported experimental observations.

  5. Selective epimerization of rapamycin via a retroaldol/aldol mechanism mediated by titanium tetraisopropoxide.

    PubMed

    Yang, W; Digits, C A; Hatada, M; Narula, S; Rozamus, L W; Huestis, C M; Wong, J; Dalgarno, D; Holt, D A

    1999-12-16

    We describe the efficient and selective epimerization of the immunosuppressant rapamycin to 28-epirapamycin under mild conditions. The mechanism of epimerization involves an equilibrium of the four C28/C29 diastereomers through a two-step retroaldol/aldol (macrocycle ring-opening/ring-closing) sequence. This retroaldol/aldol equilibration is not restricted to rapamycin but is also applicable to acyclic beta-hydroxyketones. A potentially useful extension of the method--the use of beta-hydroxyketones as enolate synthons for effecting inter- or intramolecular aldol reactions under neutral conditions--is demonstrated.

  6. Mining chemical reactions using neighborhood behavior and condensed graphs of reactions approaches.

    PubMed

    de Luca, Aurélie; Horvath, Dragos; Marcou, Gilles; Solov'ev, Vitaly; Varnek, Alexandre

    2012-09-24

    This work addresses the problem of similarity search and classification of chemical reactions using Neighborhood Behavior (NB) and Condensed Graphs of Reaction (CGR) approaches. The CGR formalism represents chemical reactions as a classical molecular graph with dynamic bonds, enabling descriptor calculations on this graph. Different types of the ISIDA fragment descriptors generated for CGRs in combination with two metrics--Tanimoto and Euclidean--were considered as chemical spaces, to serve for reaction dissimilarity scoring. The NB method has been used to select an optimal combination of descriptors which distinguish different types of chemical reactions in a database containing 8544 reactions of 9 classes. Relevance of NB analysis has been validated in generic (multiclass) similarity search and in clustering with Self-Organizing Maps (SOM). NB-compliant sets of descriptors were shown to display enhanced mapping propensities, allowing the construction of better Self-Organizing Maps and similarity searches (NB and classical similarity search criteria--AUC ROC--correlate at a level of 0.7). The analysis of the SOM clusters proved chemically meaningful CGR substructures representing specific reaction signatures.

  7. 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.

  8. A Solvent-Free Claisen Condensation Reaction for the Organic Laboratory

    NASA Astrophysics Data System (ADS)

    Esteb, John J.; Stockton, Matthew B.

    2003-12-01

    An experiment involving the Claisen condensation reaction for a first-year organic chemistry laboratory is presented. Claisen condensations are routinely covered in organic textbooks but owing to the long reaction times required to reach equilibrium in solution they are seldom explored in the undergraduate teaching laboratory. In this experiment, potassium tert-butoxide and ethyl phenylacetate are heated to 100 °C for 30 minutes under solvent-free conditions to produce 2,4-diphenyl acetoacetate in 80% yield. The solvent-free nature of this procedure greatly reduces the quantity of waste generated by students relative to typical carbonyl condensation experiments.

  9. 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.

  10. Selective Michael-aldol reaction by use of sterically hindered aluminum aryloxides as Lewis acids: an easy approach to cyclobutane amino acids.

    PubMed

    Avenoza, Alberto; Busto, Jesús H; Canal, Noelia; Peregrina, Jesús M; Pérez-Fernández, Marta

    2005-08-04

    A formal [2 + 2] cycloaddition of 2-amidoacrylates with monosubstituted donor olefins, including its asymmetric version, is described. The stereoselectivity of this reaction can be modulated by the use of sterically hindered aluminum aryloxides or methylaluminoxane as Lewis acids. The reaction was applied to the synthesis of both stereoisomers of 2-benzyloxycyclobutane-alpha-amino acid, which are protected serine analogues c(4)Ser(OBn).

  11. Chitosan as a reusable solid base catalyst for Knoevenagel condensation reaction.

    PubMed

    Sakthivel, Balasubramanian; Dhakshinamoorthy, Amarajothi

    2017-01-01

    In the present work, the commercially available chitosan is reported as a heterogeneous solid base catalyst for Knoevenagel condensation reaction of carbonyl compounds with malononitrile under mild reaction conditions. Chitosan is characterized by powder XRD, IR and elemental analysis. The catalytic activity of chitosan is evaluated in Knoevenagel condensation reaction of benzaldehyde and malononitrile as model substrates and the optimized reaction conditions are further used to expand its activity with various substrates. In addition, the catalyst stability is also examined by performing reusability, leaching experiments and it is observed that the catalyst can be reused for four times with no significant drop in its activity.

  12. Michael, Michael-aldol and Michael-Michael reactions of enolate equivalents of butane-2,3-diacetal protected glycolic acid derivatives.

    PubMed

    Ley, Steven V; Dixon, Darren J; Guy, Richard T; Rodríguez, Félix; Sheppard, Tom D

    2005-11-21

    Consecutive coupling reactions of butane-2,3-diacetal protected glycolic acid derivatives with Michael acceptors and aldehydes are reported. An enantiopure sample of this building block was used to kinetically resolve a chiral Michael acceptor present as a racemic mixture of enantiomers.

  13. 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

    2015-12-04

    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.

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

    PubMed Central

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

    2015-01-01

    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

  15. 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.

  16. 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.

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

    PubMed

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

    2014-12-08

    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.

  18. 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.

  19. 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.

  20. The possible role of solid surface area in condensation reactions during chemical evolution: reevaluation.

    PubMed

    Lahav, N; Chang, S

    1976-12-30

    Published data on adsorption and condensation of amino acids, purine and pyrimidine bases, sugars, nucleosides, and nucleotides are analyzed in connection with Bernal's hypothesis that clays and other minerals may have provided the most likely surface for adsorption and condensation of these molecules in prebiotic times. 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 dehysration (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.

  1. A biocompatible condensation reaction for controlled assembly of nanostructures in live cells

    PubMed Central

    Liang, Gaolin; Ren, Hongjun; Rao, Jianghong

    2011-01-01

    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 pH, disulfide reduction and enzymatic cleavage. In vitro, the size and shape of the condensation products, and 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. PMID:21124381

  2. 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.

  3. 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.

  4. 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…

  5. Highly efficient and recyclable basic mesoporous zeolite catalyzed condensation, hydroxylation, and cycloaddition reactions.

    PubMed

    Sarmah, Bhaskar; Satpati, Biswarup; Srivastava, Rajendra

    2017-05-01

    Crystalline mesoporous ZSM-5 zeolite was prepared in the presence of 1,4-diazabicyclo[2.2.2]octane derived multi-cationic structure directing agent. The calcined form of the mesoprous zeolite was treated with NH4OH to obtain basic mesoporous ZSM-5. Catalyst was characterized by the complementary combination of X-ray diffraction, N2-adsorption, electron microscopes, and temperature programme desorption techniques. Catalytic activity of the basic mesoporous ZSM-5 was systematically assessed using Knoevenagel condensation reaction for the synthesis a wide range of substituted styrene. Applications of the catalyst were investigated in the benzamide hydroxylation for the synthesis of carbinolamides and one-pot, multi-component condensation reaction for the synthesis of naphthopyrans. Finally, the catalyst was evaluated in the cycloaddition of CO2 to epoxide for the synthesis of cyclic carbonates. Recycling study shows that no significant decrease in the catalytic activity was observed after five recycles.

  6. 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.

  7. Stereoselectivities of Histidine-Catalyzed Asymmetric Aldol Additions and Contrasts with Proline Catalysis: A Quantum Mechanical Analysis

    PubMed Central

    Lam, Yu-hong; Houk, K. N.; Scheffler, Ulf; Mahrwald, Rainer

    2012-01-01

    Quantum mechanical calculations reveal the origin of diastereo- and enantioselectivities of aldol reactions between aldehydes catalyzed by histidine, and differences between related reactions catalyzed by proline. A stereochemical model that explains both the sense and the high levels of the experimentally observed stereoselectivity is proposed. The computations suggest that both the imidazolium and the carboxylic acid functionalities of histidine are viable hydrogen-bond donors that can stabilize the cyclic aldolization transition state. The stereoselectivity is proposed to arise from minimization of gauche interactions around the forming C–C bond. PMID:22458689

  8. Contribution from 3 alpha-Condensed States to the Triple-Alpha Reaction

    SciTech Connect

    Kato, Kiyoshi; Kurokawa, Chie; Arai, Koji

    2010-06-01

    The alpha-condensed state in nuclear systems has been proposed by Tohsaki et al. and has given rise to interesting discussions. The Hoyle state of {sup 12}C has been studied as the most typical example of such an alpha-condensed state. A new resonant 0{sub 3}{sup +} state (E{sub r} = 1.66 MeV, GAMMA = 1.48 MeV) is predicted as an excited alpha-condensed state in addition to the second 0{sup +} state of the Hoyle state by calculations of the 3 alpha orthogonality condition model (3 alpha OCM) using the complex scaling method. Based on this result, the breakup strengths of the inversion reaction for sequential ({sup 8}Be+alpha->{sup 12}C+gamma) and direct (alpha+alpha+alpha->{sup 12}C+gamma) 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 0{sub 3}{sup +} state.

  9. Two-step synthesis of hexaammonium triptycene: an air-stable building block for condensation reactions to extended triptycene derivatives.

    PubMed

    Mastalerz, Michael; Sieste, Stefanie; Cenić, Mila; Oppel, Iris M

    2011-08-05

    A simple two-step synthesis of an air-stable hexaammoniumtriptycene is introduced, which can be used for a variety of transformations by condensation reactions, e.g., to benzimidazole, benzotriazole, and quinoxaline derivatives in high yields.

  10. 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.

  11. Combustion Characteristics of Condensed Phase Reactions in Sub-Centimeter Geometries

    DTIC Science & Technology

    2012-06-10

    reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of...condensed phase reactions Ti/C, Ni/Al, and 3Ni/Al. Several other thermochemical codes ( Cheetah v6.0 [6], NASA CEA [7] and “thermo program” [8]) were...Glaesemann, K.R.; Howard, W.M;, Souers, P.C.; Vitello, P.A. CHEETAH 4.0 User’s Manual, Technical Report for Lawrence Livermore National Laboratory

  12. Progress toward the syntheses of (+)-GB 13, (+)-himgaline, and himandridine. new insights into intramolecular imine/enamine aldol cyclizations.

    PubMed

    Evans, David A; Adams, Drew J; Kwan, Eugene E

    2012-05-16

    A full account of our total synthesis of the galbulimima alkaloids GB 13 and himgaline is provided. Using a strategy adapted from the proposed biosynthesis of the GB alkaloid family, a linear precursor underwent successive intramolecular Diels-Alder, Michael, and imine aldol cyclizations to form the polycyclic alkaloid core. We now show that modification of this strategy can also deliver an advanced intermediate en route to the related alkaloid himandridine. The success of the key imine aldol cyclization is acutely sensitive to substrate structure and solvent, including a case in which cyclization was spontaneous in protic solvents. A detailed computational investigation of the course of the reaction closely correlates with, and suggests a rationale for, the observed patterns of imine aldol reactivity.

  13. Synthesis of the cores of hypocrellin and shiraiachrome: diastereoselective 1,8-diketone aldol cyclization.

    PubMed

    O'Brien, Erin M; Li, Jingxian; Carroll, Patrick J; Kozlowski, Marisa C

    2010-01-01

    Intramolecular 1,8-diketone aldol reactions were studied as a tool for the construction of the seven-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.

  14. 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

  15. 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.

  16. Progress toward chemcial accuracy in the computer simulation of condensed phase reactions

    SciTech Connect

    Bash, P.A.; Levine, D.; Hallstrom, P.; Ho, L.L.; Mackerell, A.D. Jr.

    1996-03-01

    A procedure is described for the generation of chemically accurate computer-simulation models to study chemical reactions in the condensed phase. The process involves (1) the use of a coupled semiempirical quantum and classical molecular mechanics method to represent solutes and solvent, respectively; (2) the optimization of semiempirical quantum mechanics (QM) parameters to produce a computationally efficient and chemically accurate QM model; (3) the calibration of a quantum/classical microsolvation model using ab initio quantum theory; and (4) the use of statistical mechanical principles and methods to simulate, on massively parallel computers, the thermodynamic properties of chemical reactions in aqueous solution. The utility of this process is demonstrated by the calculation of the enthalpy of reaction in vacuum and free energy change in aqueous solution for a proton transfer involving methanol, methoxide, imidazole, and imidazolium, which are functional groups involved with proton transfers in many biochemical systems. An optimized semiempirical QM model is produced, which results in the calculation of heats of formation of the above chemical species to within 1.0 kcal/mol of experimental values. The use of the calibrated QM and microsolvation QM/MM models for the simulation of a proton transfer in aqueous solution gives a calculated free energy that is within 1.0 kcal/mol (12.2 calculated vs. 12.8 experimental) of a value estimated from experimental pKa`s of the reacting species.

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

    SciTech Connect

    Miknis, F.P.

    1992-07-01

    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 will 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/semi-solid material formed or remaining during pretreatment and the initial stages of liquefaction. The aromatic hydrogen-to-carbon ratios are difficult, if not impossible, to measure without the use of solid-state NMR, and as a result this ratio will be used to monitor the retrograde/condensation reactions that take place during coal liquefaction in the presence and absence of steam and various inert gases.

  18. 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.

  19. 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.

  20. 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

    2009-01-02

    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.

  1. Condensation reaction between carbohydrazide and salicylaldehyde: in-line vibrational spectroscopy monitoring and characterization of the reaction products in solution and solid state.

    PubMed

    Jednačak, Tomislav; Novak, Predrag; Hodzic, Aden; Scheibelhofer, Otto; Khinast, Johannes G; Plavec, Janez; Sket, Primož; Parlov, Vuković Jelena

    2014-01-01

    The condensation reaction between carbohydrazide and salicylaldehyde was monitored in-line by using vibrational NIR and Raman spectroscopies and statistical methods. Prior to in-line data analysis the reaction products were fully characterized in solution and solid state in order to check the potential of the in-line approach as a tool for in-process Schiff bases reaction control. It was demonstrated that a combination of vibrational spectroscopy and principal component analysis made it possible to detect and identify the reaction products, e.g. mono(salicylidene)carbohydrazide (1) and bis(salicylidene)carbohydrazide (2) in different solvents, and to determine the reaction end points in real time. Owing to complexity of the reaction mixtures and band overlapping, it was not possible to determine the relative ratio of the reaction products in-line. The off-line analysis showed that 1 was predominant in methanol while the highest portion of 2 was obtained in ethanol.

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  5. 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.

  6. 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

  7. 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.

  8. Di- and triheteroarylalkanes via self-condensation and intramolecular Friedel-Crafts type reaction of heteroaryl alcohols.

    PubMed

    Dhiman, Seema; Ramasastry, S S V

    2013-12-14

    An efficient synthetic approach to diheteroarylmethanes and 1,3-diheteroarylpropenes has been developed via Yb(III)-catalyzed sequential self-condensation of 2-furfuryl (or 2-thienyl or 3-indolyl) alcohols followed by intramolecular Friedel-Crafts type reaction and elimination of an aldehyde. This method offers a powerful entry and a potential alternative to the traditional synthesis of diheteroarylalkanes, which are precursors to the synthesis of several intriguing heteroaryls and more significantly, to the synthesis of biofuels.

  9. 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

  10. 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.

  11. 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.

  12. Oxidative condensation reactions of (diethylenetriamine)cobalt(III) complexes with substituted bis(pyridin-2-yl)methane ligands

    NASA Astrophysics Data System (ADS)

    Zhou, Xiangting; Hockless, David C. R.; Willis, Anthony C.; Jackson, W. Gregory

    2005-04-01

    The synthesis and characterisation of Co(III) complexes derived from a condensation reaction with a central or terminal nitrogen of a dien ligand and the α-carbon of a range of substituted bis(pyridin-2-yl)methane ligands are described. Aerial oxidation of bpm {bis(pyridin-2-yl)methane with Co(II)/dien or direct reaction with Co(dien)Cl 3 provided in low yield a single C-N condensation product 1 (at the primary terminal NH 2) after the pyridyl -CH 2- is formally oxidised to -CH +-. The methyl substituted ligand bpe {1,1-bis(pyridin-2-yl)ethane} behaves likewise, except both terminal (prim) and central (sec) amines condense to yield isomeric products 2 and 3. Two of these three materials have been characterised by single crystal X-ray crystallography. The corresponding reactions for the bis(pyridyl) ligand bpk {bis(pyridin-2-yl)ketone} provided C-N condensation products without the requirement for oxidation at the α-C center; two carbinolamine complexes in different geometrical configurations resulted, mer-anti-[Co(dienbpc)Cl]ZnCl 4, 5, and unsym- fac-[Co(dienbpc)Cl]ZnCl 4, 6, {dienbpc=[2-(2-aminoethylamino)-ethylamino]-di-pyridin-2-yl-methanol}. In addition, a novel complex, [Co(bpk)(bpd-OH)Cl]ZnCl 4, 4, in which one bidentate N, N-bonded bpk ligand and one tridentate N, O, N-bonded bpd (the diol from bpk+OH -) were coordinated, was obtained via the Co(II)/O 2 synthetic route. When the bpc ligand (bpc=bis(pyridin-2-yl)methanol) was employed directly as a reagent along with dien, no condensation reactions were observed, but rather a single isomeric complex [Co(dien)(bpc)]Cl.ZnCl 4, 7, in which the ligand bpc acted as a N,N,O-bonded tridentate ligand rather than as a N,N-bidentate ligand was isolated. 13C, 1D and 2D 1H NMR studies are reported for all the complexes; they establish the structures unambiguously.

  13. Sequential Norrish type II photoelimination and intramolecular aldol cyclization of α-diketones: synthesis of polyhydroxylated cyclopentitols by ring contraction of hexopyranose carbohydrate derivatives.

    PubMed

    Alvarez-Dorta, Dimitri; León, Elisa I; Kennedy, Alan R; Martín, Angeles; Pérez-Martín, Inés; Riesco-Fagundo, Concepción; Suárez, Ernesto

    2013-07-29

    The excitation of the innermost carbonyl of nono-2,3-diulose derivatives by irradiation with visible-light initiates a sequential Norrish type II photoelimination and aldol cyclization process that finally gives polyfunctionalized cyclopentitols. The rearrangement has been confirmed by the isolation of stable acyclic photoenol intermediates that can be independently cyclized by a thermal 5-(enolexo)-exo-trig uncatalyzed aldol reaction with high diastereoselectivity. In this last step, the large deuterium kinetic isotope effect found for the 1,5-hydrogen atom transfer seems to indicate that the aldol reaction runs through a concerted pericyclic mechanism. Owing to the ready availability of pyranose sugars of various configurations, this protocol has been used to study the influence of pyranose ring-substituents on the diastereoselectivity of the aldol cyclization reaction. In contrast with other pyranose ring contraction methodologies no transition-metal reagents are needed and the sequential rearrangement occurs simply by using visible light and moderate heating (0 to 60 °C).

  14. 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.

  15. Synthesis of novel dendritic 2,2'-bipyridine ligands and their application to Lewis acid-catalyzed diels-alder and three-component condensation reactions.

    PubMed

    Muraki, Takahito; Fujita, Ken-ichi; Kujime, Masato

    2007-10-12

    A series of dendritic ligands with a 2,2'-bipyridine core was synthesized through the coupling of 4,4'-dihydroxy-2,2'-bipyridine with poly(aryl ether) dendrons. The corresponding dendritic Cu(OTf)2 catalysts were used for Diels-Alder and three-component condensation reactions. The dendritic Cu(OTf)2-catalyzed Diels-Alder reaction proceeded smoothly, and these dendritic catalysts could be recycled without deactivation by reprecipitation. Three-component condensation reactions such as Mannich-type reactions also proceeded not only in dichloromethane but also in water. Furthermore, a positive dendritic effect on chemical yields was observed in both Diels-Alder reactions and aqueous-media three-component condensation reactions.

  16. Rate-promoting vibrations and coupled hydrogen-electron transfer reactions in the condensed phase: A model for enzymatic catalysis

    NASA Astrophysics Data System (ADS)

    Mincer, Joshua S.; Schwartz, Steven D.

    2004-04-01

    A model is presented for coupled hydrogen-electron transfer reactions in condensed phase in the presence of a rate promoting vibration. Large kinetic isotope effects (KIEs) are found when the hydrogen is substituted with deuterium. While these KIEs are essentially temperature independent, reaction rates do exhibit temperature dependence. These findings agree with recent experimental data for various enzyme-catalyzed reactions, such as the amine dehydrogenases and soybean lipoxygenase. Consistent with earlier results, turning off the promoting vibration results in an increased KIE. Increasing the barrier height increases the KIE, while increasing the rate of electron transfer decreases it. These results are discussed in light of other views of vibrationally enhanced tunneling in enzymes.

  17. 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.

  18. Energy- and carbon-efficient synthesis of functionalized small molecules in bacteria using non-decarboxylative Claisen condensation reactions.

    PubMed

    Cheong, Seokjung; Clomburg, James M; Gonzalez, Ramon

    2016-05-01

    Anabolic metabolism can produce an array of small molecules, but yields and productivities are low owing to carbon and energy inefficiencies and slow kinetics. Catabolic and fermentative pathways, on the other hand, are carbon and energy efficient but support only a limited product range. We used carbon- and energy-efficient non-decarboxylative Claisen condensation reactions and subsequent β-reduction reactions, which can accept a variety of functionalized primers and functionalized extender units and operate in an iterative manner, to synthesize functionalized small molecules. Using different ω- and ω-1-functionalized primers and α-functionalized extender units in combination with various termination pathways, we demonstrate the synthesis of 18 products from 10 classes, including ω-phenylalkanoic, α,ω-dicarboxylic, ω-hydroxy, ω-1-oxo, ω-1-methyl, 2-methyl, 2-methyl-2-enolic and 2,3-dihydroxy acids, β-hydroxy-ω-lactones, and ω-1-methyl alcohols.

  19. Reactions of pulsed laser produced boron and nitrogen atoms in a condensing argon stream

    NASA Astrophysics Data System (ADS)

    Andrews, Lester; Hassanzadeh, Parviz; Burkholder, Thomas R.; Martin, J. M. L.

    1993-01-01

    Reactions of pulsed laser produced B and N atoms at high dilution in argon favored diboron species. At low laser power with minimum radiation, the dominant reaction with N2 gave BBNN (3Π). At higher laser power, reactions of N atoms contributed the B2N (2B2), BNB (2Σu+), NNBN (1Σ+), and BNBN (3Π) species. These new transient molecules were identified from mixed isotopic patterns, isotopic shifts, and ab initio calculations of isotopic spectra.

  20. 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

  1. 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

  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.

    PubMed

    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

    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 (1)H 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

  4. 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

  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 Matrix Calculations in Neutron Matter with Alternating-Layer-Spin Structure under π0 Condensation. II ---Numerical Results---

    NASA Astrophysics Data System (ADS)

    Tamiya, K.; Tamagaki, R.

    1981-10-01

    Results obtained by applying a formulation based on the reaction matrix theory developed in I are given. Calculations by making use of a modified realistic potential, the Reid soft-core potential with the OPEP-part enhanced due to the isobar (Δ)-mixing, show that the transition to the [ALS] phase of quasi-neutrons corresponding to a typical π0 condensation occurs in the region of (2 ˜ 3) times the nuclear density. The most important ingredients responsible for this transition are the growth of the attractive 3P2 + 3F2 contribution mainly from the spin-parallel pairs in the same leyers and the reduction of the repulsive 3P1 contribution mainly from the spin-antiparallel pairs in the nearest layers; these mainfest themselves as the [ALS]-type localization develops. Properties of the matter under the new phase thus obtained such as the shape of the Fermi surface and the effective mass are discussed.

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

    SciTech Connect

    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. The authors have modeled diagenetic changes in a biomineral by heating at 90C 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 (1,281 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 authors roughly estimate that, at the global scale, 2.4 {times} 10{sup 6} tons 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.

  8. Highly efficient aldol additions of DHA and DHAP to N-Cbz-amino aldehydes catalyzed by L-rhamnulose-1-phosphate and L-fuculose-1-phosphate aldolases in aqueous borate buffer.

    PubMed

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

    2011-12-21

    Aldol addition reactions of dihydroxyacetone (DHA) to N-Cbz-amino aldehydes catalyzed by L-rhamnulose-1-phosphate aldolase (RhuA) in the presence of borate buffer are reported. High yields of aldol adduct (e.g. 70-90%) were achieved with excellent (>98 : 2 syn/anti) stereoselectivity for most S or R configured acceptors, which compares favorably to the reactions performed with DHAP. The stereochemical outcome was different and depended on the N-Cbz-amino aldehyde enantiomer: the S acceptors gave the syn (3R,4S) aldol adduct whereas the R ones gave the anti (3R,4R) diastereomer. Moreover, the tactical use of Cbz protecting group allows simple and efficient elimination of borate and excess of DHA by reverse phase column chromatography or even by simple extraction. This, in addition to the use of unphosphorylated donor nucleophile, makes a useful and expedient methodology for the synthesis of structurally diverse iminocyclitols. The performance of aldol additions of dihydroxyacetone phosphate (DHAP) to N-Cbz-amino aldehydes using RhuA and L-fuculose-1-phosphate aldolase (FucA) catalyst in borate buffer was also evaluated. For FucA catalysts, including FucA F131A, the initial velocity of the aldol addition reactions using DHAP were between 2 and 10 times faster and the yields between 1.5 and 4 times higher than those in triethanolamine buffer. In this case, the retroaldol velocities measured for some aldol adducts were lower than those without borate buffer indicating some trapping effect that could explain the improvement of yields.

  9. Cd-Based metal-organic frameworks from solvothermal reactions involving in situ aldimine condensation and the highly sensitive detection of Fe(3+) ions.

    PubMed

    Zhang, Xin; Wang, Zhong-Jie; Chen, Shu-Guang; Shi, Zhen-Zhen; Chen, Jin-Xi; Zheng, He-Gen

    2017-02-14

    Four Cd(ii)-based compounds (1-4) were synthesized from solvothermal reactions involving the in situ aldimine condensation of an o-diamino-functionalized precursor 3,6-di(4H-imidazol-4-yl)benzene-1,2-diamine (L), Cd(NO3)2·4H2O and aldehyde. Two modes of cycloaddition ([4 + 1] cycloaddition and [4 + 2] cycloaddition) occurred during condensation, causing the in situ generation of two benzimidazole derivative ligands (L1 and L3) and a quinoxaline derivative ligand (L2). Furthermore, the chemical selectivity of the condensation was studied, where the condensation of o-diamino and the aldehyde is more stable and easy to operate. This strategy enriches the synthesis method of MOFs. Additionally, compound 2 containing uncoordinated quinoxaline N atoms showed excellent luminescent sensitivity for Fe(3+) detection.

  10. 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

  11. A microscopic frictional theory for reactions in condensed phases: Influence of nonlinear couplings

    NASA Astrophysics Data System (ADS)

    Nagaoka, Masataka; Yoshida, Naoto; Yamabe, Tokio

    1996-10-01

    On the assumption of external bath equilibrium, a set of simultaneous linear generalized Langevin equations (GLE) for a microscopic Hamiltonian is derived, whose potential function includes cubic (i.e., nonlinear) coupling terms, which are linear in internal coordinates but quadratic in external bath coordinates. Furthermore, on the linear GLE treatment, a closed expression of time-dependent friction coefficient and a rate constant in the Grote-Hynes theory (GHT) are derived microscopically, reflecting the reactant and solvent structures. By comparing the rate constant of GHT with that of the multidimensional transition-state theory (TST) for the whole solution system, we conclude that these rate expressions are different from each other and the deviation is due to the dynamic effect via the nonlinear coupling among the reaction, internal, and external normal coordinates. Moreover, the friction coefficient depends on temperature and the deviation becomes larger with temperature increasing. By the second-order perturbation theory, we have estimated the deviation which is approximately equal to a transmission coefficient κ, for a real cluster reaction system: the formic acid-water-water system. We have obtained κ of 0.92, which is smaller than unity. A mode analysis shows that two hindered translational motions of the solvent with low frequencies prevent the reaction from proceeding. Besides, we have investigated the isotope effect of a medium water molecule and found that the dynamic isotope effect for the reaction is quite large, i.e., κ for heavy water is much smaller than that for light water. Not the change of the reactive frequency on the free energy surface but that of the frictional effect in the deuterium substitution mainly contributes to the isotope effect. Further, the temperature dependence of κ for the reaction has been estimated and it is found that κ becomes smaller with temperature increasing and the change of the frictional effect in

  12. The Role of Metal Oxides in Nanothermite Reactions: Evidence of Condensed Phase Initiation

    DTIC Science & Technology

    2010-01-01

    Al/WO3, and Al/ Bi2O3 were all tested with this system along with 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES The...Fe2O3, Al/WO3, and Al/ Bi2O3 were all tested with this system along with the neat Al and metal oxide powders. High speed imaging was also used to...visually compare reaction rates of each sample showing that, contradictory to some previous works, Al/ Bi2O3 reacts much faster than the other

  13. 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.

  14. Numerical study of the evaporation/condensation phase transition of droplets for an irreversible reaction model

    NASA Astrophysics Data System (ADS)

    Loscar, E. S.; Albano, E. V.

    2009-02-01

    The ZGB model (Ziff M. R., Gulari E. and Barshad Y., Phys. Rev. Lett., 56 (1986) 2553) for a monomer-dimer catalytic reaction exhibits both second-order and first-order irreversible phase transitions. We report a numerical simulation study of the ZGB model close to coexistence, performed by using the constant-coverage monomer ensemble (CC). By means of CC stationary measurements we found that, in the super-saturated region, there is a phase-transition-like behaviour, for finite systems, between a super-saturated state and a phase where solid monomer droplets coexist with the super-saturated state. Also, we show that the transition point converges, according to a power law behaviour, towards coexistence, so that it is no longer possible to measure any (thermodynamic) spinodal point by using the CC stationary approach. However, by using a dynamic CC ensemble, evidence of the upper spinodal point can clearly be identified: scale invariance of the monomer-droplet size distribution and a maximum in the susceptibility. It is also discussed how to define a spinodal point in the thermodynamic limit for this model.

  15. 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.

  16. Reaction Matrix Calculations in Neutron Matter with Alternating-Layer-Spin Structure under π0 Condensation. I ---Formulation---

    NASA Astrophysics Data System (ADS)

    Tamiya, K.; Tamagaki, R.

    1981-09-01

    Based on the viewpoint that a typical π0 condensation is realized with the [ALS] (Alternating-Layer-Spin) structure of nucleon system, a framework to calculate the energy of neutron matter under such a new phase is presented in the reaction matrix theory. This enables us to treat both effects on equal footing; the long-range effect dominated by the OPEP tensor component with the enhancement due to the mixing of Δ(1236MeV) and the sort-range effect much influenced by repulsive core and spin-orbit force. Starting with the [ALS] model wave function constructed on the Bloch basis which assures to take the limit of no localization, we have the expressions for energy quantities expressed by the partial-wave contributions. This scheme provides a way to understand the mechanism of energy gain in the new phase, by making use of the notions of the ordinary unclear matter theory such as the potential picture and the partial waves. Some numerical examples are shown.

  17. 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.

  18. 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.

  19. Synthesis of oxazolidine-2,4-diones by a tandem phosphorus-mediated carboxylative condensation-cyclization reaction using atmospheric carbon dioxide.

    PubMed

    Zhang, Wen-Zhen; Xia, Tian; Yang, Xu-Tong; Lu, Xiao-Bing

    2015-04-11

    The oxazolidine-2,4-dione motif is found frequently in biologically important compounds. A tandem phosphorus-mediated carboxylative condensation of primary amines and α-ketoesters/base-catalyzed cyclization reaction have been developed. These processes provide a novel and convenient access to various oxazolidine-2,4-diones in a one-pot fashion using atmospheric carbon dioxide and readily available substrates under very mild and transition-metal-free conditions.

  20. 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.

  1. 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.

  2. Relation of the number of cross-links and mechanical properties of multi-walled carbon nanotube films formed by a dehydration condensation reaction.

    PubMed

    Ogino, Shin-Ichi; Sato, Yoshinori; Yamamoto, Go; Sasamori, Kenichiro; Kimura, Hisamichi; Hashida, Toshiyuki; Motomiya, Kenichi; Jeyadevan, Balachandran; Tohji, Kazuyuki

    2006-11-23

    Multi-walled carbon nanotube (MWCNT) films were prepared by employing a condensation reaction utilizing 1,3-dicyclohexylcarbodiimide (DCC) to cross-link each MWCNT with carboxylic acid and hydroxyl groups. 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 17 mm in diameter and 20 microm in thickness, and the apparent density was 0.59 g/cm(3). 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 (cm(3)) of condensed-MWCNT films was 5.27 x 10(-3) using thermogravimetric analysis (TGA). The tensile strength and Vickers hardness of condensed-MWCNT films achieved an average of 15 and 9.2 MPa, respectively, and were greater than those of free-standing MWCNT films without ester bond.

  3. Combined QM/MM Molecular Dynamics Study on a Condensed-Phase SN2 Reaction at Nitrogen:  The Effect of Explicitly Including Solvent Polarization.

    PubMed

    Geerke, Daan P; Thiel, Stephan; Thiel, Walter; van Gunsteren, Wilfred F

    2007-07-01

    In a previous combined QM/MM molecular dynamics (MD) study from our laboratory on the identity SN2 reaction between a chloride anion and an amino chloride in liquid dimethyl ether (DME), an increase in the free energy activation barrier was observed in the condensed phase when compared to the gas-phase activation energy. Here we reproduce these findings, but when comparing the condensed-phase potential of mean force (PMF) with the free energy profile in the gas phase (obtained from Monte Carlo simulations), we observe a smaller solvent effect on the activation barrier of the reaction. In a next step, we introduce an explicit description of electronic polarization in the MM (solvent) part of the system. A polarizable force field for liquid DME was developed based on the charge-on-spring (COS) model, which was calibrated to reproduce thermodynamic properties of the nonpolarizable model in classical MD simulations. The COS model was implemented into the MNDO/GROMOS interface in a special version of the QM/MM software ChemShell, which was used to investigate the effect of solvent polarization on the free energy profile of the reaction under study. A higher activation barrier was obtained using the polarizable solvent model than with the nonpolarizable force field, due to a better solvation of and a stronger polarization of solvent molecules around the separate reactants. The obtained PMFs were subjected to an energy-entropy decomposition of the relative solvation free energies of the reactant complex along the reaction coordinate, to investigate in a quantitative manner whether the solvent (polarization) effects are mainly due to favorable QM-MM (energetic) interactions.

  4. Zinc Oxide Nanoparticles Catalyzed Condensation Reaction of Isocoumarins and 1,7-Heptadiamine in the Formation of Bis-Isoquinolinones

    PubMed Central

    Krishnakumar, Varadhan; Mohan Kumar, Kesarla; Mandal, Badal Kumar; Khan, Fazlur-Rahman Nawaz

    2012-01-01

    The diversified bis-isoquinolinones were obtained in two steps, utilizing homophthalic acid and various acid chlorides providing 3-substituted isocoumarins in the first step which on further condensation with 1,7-heptadiamine involving C–N bond formation from the lactone in the presence of 10 mol% zinc oxide nanoparticles (ZnO NPs) (<150 nm) afforded the desired bis-isoquinolinones in high yield and purity. The synthesized compounds were then characterized using FTIR, 1H NMR, 13C NMR, and HRMS techniques. PMID:22536149

  5. Condensation of chondrules

    NASA Technical Reports Server (NTRS)

    Blander, M.

    1983-01-01

    Analysis of current experimental results concerned with the kinetic constraints on chondrule formation showed that the major physical properties of chondrules could have been produced by direct condensation of metastable liquid silicates droplets from a hot gas in the primordial nebula. It is argued that such a condensation process would have to be followed by crystallization, accretion, and partial comminution of the droplets. The chemical mechanisms driving this process are described, including: nucleation constraints on comminution and crystallization; slow transformations and chemical reactions in chain silicates; and the slow diffusion of ions. It is shown that the physical mechanisms for chondrule condensation are applicable to a broad spectrum of chondrule sources.

  6. Control of reaction efficiency by two-color two-pulse excitation: Photoisomerization of indocyanine green in condensed phase

    NASA Astrophysics Data System (ADS)

    Fuyuki, Masanori; Furuta, Koichi; Wada, Akihide

    2011-07-01

    In cyanine dye, photoisomerization paths involving multiphoton processes were found by two-color two-pulse correlation of ultrafast transient absorption spectroscopy. The reaction efficiency depended on the interval between two pump pulses, UV and NIR pulses, as well as the fluence of the NIR pulse, but was little dependent on that of the UV pulse. These results indicate that the new photoisomerization paths involve the NIR multiphoton process and/or the UV one-photon process. The difference in two-pulse correlation between positive and negative time regions revealed a new reaction path that had the highest branching ratio of cis isomer to other leuco forms.

  7. Mechanistic Investigation of Catalyst-Transfer Suzuki-Miyaura Condensation Polymerization of Thiophene-Pyridine Biaryl Monomers with the Aid of Model Reactions.

    PubMed

    Tokita, Yu; Katoh, Masaru; Ohta, Yoshihiro; Yokozawa, Tsutomu

    2016-11-21

    We have investigated the requirements for efficient Pd-catalyzed Suzuki-Miyaura catalyst-transfer condensation polymerization (Pd-CTCP) reactions of 2-alkoxypropyl-6-(5-bromothiophen-2-yl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (12) as a donor-acceptor (D-A) biaryl monomer. As model reactions, we first carried out the Suzuki-Miyaura coupling reaction of X-Py-Th-X' (Th=thiophene, Py=pyridine, X, X'=Br or I) 1 with phenylboronic acid ester 2 by using tBu3 PPd(0) as the catalyst. Monosubstitution with a phenyl group at Th-I mainly took place in the reaction of Br-Py-Th-I (1 b) with 2, whereas disubstitution selectively occurred in the reaction of I-Py-Th-Br (1 c) with 2, indicating that the Pd catalyst is intramolecularly transferred from acceptor Py to donor Th. Therefore, we synthesized monomer 12 by introduction of a boronate moiety and bromine into Py and Th, respectively. However, examination of the relationship between monomer conversion and the Mn of the obtained polymer, as well as the matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra, indicated that Suzuki-Miyaura coupling polymerization of 12 with (o-tolyl)tBu3 PPdBr initiator 13 proceeded in a step-growth polymerization manner through intermolecular transfer of the Pd catalyst. To understand the discrepancy between the model reactions and polymerization reaction, Suzuki-Miyaura coupling reactions of 1 c with thiopheneboronic acid ester instead of 2 were carried out. This resulted in a decrease of the disubstitution product. Therefore, step-growth polymerization appears to be due to intermolecular transfer of the Pd catalyst from Th after reductive elimination of the Th-Pd-Py complex formed by transmetalation of polymer Th-Br with (Pin)B-Py-Th-Br monomer 12 (Pin=pinacol). Catalysts with similar stabilization energies of metal-arene η(2) -coordination for D and A monomers may be needed for CTCP reactions of biaryl D-A monomers.

  8. 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

    2016-09-06

    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).

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

    SciTech Connect

    Miknis, F.P.

    1992-07-01

    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 will 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/semi-solid material formed or remaining during pretreatment and the initial stages of liquefaction. The aromatic hydrogen-to-carbon ratios are difficult, if not impossible, to measure without the use of solid-state NMR, and as a result this ratio will be used to monitor the retrograde/condensation reactions that take place during coal liquefaction in the presence and absence of steam and various inert gases.

  10. The kinetics of the bimolecular A+B --> 0 reaction in condensed matter: Effects of non-equilibrium charge screening

    NASA Astrophysics Data System (ADS)

    Kuzovkov, V. N.; Kotomin, E. A.; von Niessen, W.

    1996-12-01

    The kinetics of the bimolecular A+B→0 reaction between charged reactants is studied in two dimensions, i.e., on a surface. The theory is based on the Kirkwood superposition approximation for three-particle densities and the self-consistent treatment of the electrostatic interactions defined by the non-uniform spatial distribution of similar and dissimilar reactants. Special attention is paid to pattern formation and many-particle effects arising from reaction-induced formation of loose domains containing similar reactants only. It is shown that the critical exponent α characterizing the algebraic concentration decay law, n(t)∝t-α, differs strongly between symmetric (DA=DB) and asymmetric (DA=0) reactant mobilities. This effect is abnormal from the point of view of standard chemical kinetics. It arises directly from the specific spatial distribution in the system as in ``raisins A in a dough B.'' At long reaction times the asymptotics of the interaction potentials is of non-equilibrium type at large relative distances. The accumulation kinetics in the presence of a permanent source is studied. Results of the microscopic formalism are compared with a previous mesoscopic theory.

  11. Acid-catalyzed condensed-phase reactions of limonene and terpineol and their impacts on gas-to-particle partitioning in the formation of organic aerosols.

    PubMed

    Li, Yong Jie; Cheong, Gema Y L; Lau, Arthur P S; Chan, Chak K

    2010-07-15

    We investigated the condensed-phase reactions of biogenic VOCs with C double bond C bonds (limonene, C(10)H(16), and terpineol, C(10)H(18)O) catalyzed by sulfuric acid by both bulk solution (BS) experiments and gas-particle (GP) experiments using a flow cell reactor. Product analysis by gas chromatography-mass spectrometry (GC-MS) showed that cationic polymerization led to dimeric and trimeric product formation under conditions of relative humidity (RH) <20% (in the GP experiments) and a sulfuric acid concentration of 57.8 wt % (in the BS experiments), while hydration occurred under conditions of RH > 20% (in the GP experiments) and sulfuric acid concentrations of 46.3 wt % or lower (in the BS experiments). Apparent partitioning coefficients (K(p,rxn)) were estimated from the GP experiments by including the reaction products. Only under extremely low RH conditions (RH < 5%) did the values of K(p,rxn) ( approximately 5 x 10(-6) m(3)/microg for limonene and approximately 2 x 10(-5) m(3)/microg for terpineol) substantially exceed the physical partitioning coefficients (K(p) = 6.5 x 10(-8) m(3)/microg for limonene and =2.3 x 10(-6) m(3)/microg for terpineol) derived from the absorptive partitioning theory. At RH higher than 5%, the apparent partitioning coefficients (K(p,rxn)) of both limonene and terpineol were in the same order of magnitude as the K(p) values derived from the absorptive partitioning theory. Compared with other conditions including VOC concentration and degree of neutralization (by ammonium) of acidic particles, RH is a critical parameter that influences both the reaction mechanisms and the uptake ability (K(p,rxn) values) of these processes. The finding suggests that RH needs to be considered when taking the effects of acid-catalyzed reactions into account in estimating organic aerosol formation from C double bond C containing VOCs.

  12. 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.

  13. 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.

  14. 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)

  15. 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...

  16. Mathematical model for aldol addition catalyzed by two D-fructose-6-phosphate aldolases variants overexpressed in E. coli.

    PubMed

    Sudar, Martina; Findrik, Zvjezdana; Vasić-Rački, Durđa; Clapés, Pere; Lozano, Carles

    2013-09-10

    Two D-fructose-6-phosphate aldolase variants namely, single variant FSA A129S and double variant FSA A129S/A165G, were used as catalysts in the aldol addition of dihydroxyacetone (DHA) to N-Cbz-3-aminopropanal. Mathematical model for reaction catalyzed by both enzymes, consisting of kinetic and mass balance equations, was developed. Kinetic parameters were estimated from the experimental data gathered by using the initial reaction rate method. The model was validated in the batch and continuously operated ultrafiltration membrane reactor (UFMR). The same type of kinetic model could be applied for both enzymes. The operational stability of the aldolases was assessed by measuring enzyme activity during the experiments. FSA A129S/A165G had better operational stability in the batch reactor (half-life time 26.7 h) in comparison to FSA A129S (half-life time 5.78 h). Both variants were unstable in the continuously operated UFMR in which half-life times were 1.99 and 3.64 h for FSA A129S and FSA A129S/A165G, respectively.

  17. 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.

  18. 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.

  19. Lewis base catalyzed, enantioselective aldol addition of methyl trichlorosilyl ketene acetal to ketones.

    PubMed

    Denmark, Scott E; Fan, Yu; Eastgate, Martin D

    2005-06-24

    The catalytic enantioselective addition of an acetate enolate equivalent to ketones is described. Methyl trichlorosilyl ketene acetal reacts with a wide range of ketones in the presence of pyridine N-oxide to afford the aldol addition products in excellent yields. Chiral 2,2'-pyridyl bis-N-oxides bearing various substituents at the 3,3'- and 6,6'-positions also provide excellent yields of the aldol products with variable enantioselectivities ranging from 94/6 er for aromatic ketones to nearly racemic for aliphatic ketones. An X-ray crystal structure of the complex between a catalyst and silicon tetrachloride (((P)-(R,R)-19.SiCl(4))) has been obtained. Extensive computational analysis provides a stereochemical rationale for the observed trends in enantioselectivities.

  20. Identification of 4-methylspinaceamine, a pictet-spengler condensation reaction product of histamine with acetaldehyde, in fermented foods and its metabolite in human urine.

    PubMed

    Ohya, Takeshi

    2006-09-06

    Previous study demonstrated that 4-methylspinaceamine (4-methyl-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine), a Pictet-Spengler condensation reaction product of histamine with acetaldehyde, is present in human urine. The current study sought to determine whether 4-methylspinaceamine is present in fermented foods; its presence might be expected since both histamine and acetaldehyde are often present in these foods. Soy sauce, fish sauce, cheese, and shao hsing wine (Chinese wine) were found to contain 4-methylspinaceamine. The concentration of 4-methylspinaceamine excreted in human urine was greatly elevated after ingestion of a meal containing soy sauce as a dietary source of 4-methylspinaceamine, demonstrating that the level of 4-methylspinaceamine in human urine was affected by dietary foods. In addition, a metabolite of 4-methylspinaceamine in human urine was investigated. An enhanced peak in the HPLC chromatogram of human urine samples after ingestion of 4-methylspinaceamine-containing foods was observed. A peak at the same retention time was also observed from a human urine sample after administration of 4-methylspinaceamine, suggesting that the peak was due to a metabolite. By comparison with the newly synthesized authentic compound, the metabolite was identified as 1,4-dimethylspinaceamine.

  1. 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.

  2. 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.

  3. 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...

  4. 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...

  5. 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.

  6. 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.

  7. Copper-catalyzed cascade reactions of α,β-unsaturated esters with keto esters

    PubMed Central

    Wang, Chongnian; Li, Zengchang

    2015-01-01

    Summary A copper-catalyzed cascade reaction of α,β-unsaturated esters with keto esters is reported. It features a copper-catalyzed reductive aldolization followed by a lactonization. This method provides a facile approach to prepare γ-carboxymethyl-γ-lactones and δ-carboxymethyl-δ-lactones under mild reaction conditions. PMID:25815072

  8. 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

  9. Rapid construction of the aza-propellane core of acutumine via a photochemical [2 + 2] cycloaddition reaction.

    PubMed

    Navarro, Raul; Reisman, Sarah E

    2012-09-07

    Synthetic efforts toward the chlorinated aza-propellane alkaloid acutumine (1) are described. The key vicinal quaternary centers were constructed by a photochemical [2 + 2] cycloaddition reaction of a furanyl-tetrahydroindolone. Dihydroxylation of the [2 + 2] product enabled a tandem retro-aldol/intramolecular ketalization reaction, which revealed the aza-propellane core of 1 while generating an unusual, caged, pentacyclic hemiketal product.

  10. Enantioselective Formal [3 + 1 + 1] Cycloaddition Reaction by Ru(II)/Iminium Cocatalysis for Construction of Multisubstituted Pyrrolidines.

    PubMed

    Li, Mingfeng; Chu, Rui; Chen, Jianghui; Wu, Xiang; Zhao, Yun; Liu, Shunying; Hu, Wenhao

    2017-03-01

    A Ru(II)/iminium cocatalyzed asymmetric formal [3 + 1 + 1] cycloaddition reaction of diazoacetophenones, anilines, and enals is disclosed to construct multisubstituted pyrrolidines in one step with excellent diastereoselectivity and enantioselectivity. The reaction mechanism was postulated as a successful trapping of Ru(II)-associated ammonium ylides via a selective 1,4-addition to chiral amine activated enals followed by a tandem aza-aldol process. The control experiments and theoretical density functional theory investigation revealed that the reversible NaOAc-facilitated aza-aldol process led to the diastereomeric conversion to provide a stable product.

  11. Kinetic heterogeneity of F-actin polymers. Further evidence that the elongation reaction may occur through condensation of the actin filaments with small aggregates.

    PubMed Central

    Grazi, E; Magri, E

    1987-01-01

    We have shown that F-actin, polymerized in 50 mM-KCl at 20 degrees C and pH 8.0, can be resolved by centrifugation into two polymer populations, which differ morphologically as well as kinetically. The first population represents about 10% of the overall polymer and is composed of small amorphous aggregates. It rapidly exchanges the bound nucleotide with free ATP in the medium, either directly or through the monomers. The second population is composed of long actin filaments. These are labelled by free ATP in the medium only through condensation with labelled small amorphous aggregates. Images Fig. 1. PMID:3435480

  12. Stereoselective synthesis of 1,3-anti diols by an Ipc-mediated domino aldol-coupling/reduction sequence.

    PubMed

    Dieckmann, Michael; Menche, Dirk

    2013-01-04

    A novel domino process for 1,3-anti diol synthesis by the union of a methyl ketone with an aldehyde is described. The operationally simple procedure is based on an Ipc-boron-aldol coupling and subsequent Ipc-mediated reduction of the intermediate β-hydroxy-ketone. The sequence proceeds with excellent anti-selectivities and enables the rapid construction of complex polyketide fragments.

  13. 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)

  14. 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.

  15. Catalytic conversion of bio-oil to oxygen-containing fuels by simultaneous reactions with 1-butanol and 1-octene over solid acids: Model compound studies and reaction pathways.

    PubMed

    Zhang, Zhi-Jun; Sui, Shu-Juan; Tan, Shun; Wang, Qing-Wen; Pittman, Charles U

    2013-02-01

    Upgrading bio-oil by addition reactions across olefins represents a route to refine bio-oil to combustible and stable oxygen-containing fuels. Development and application of highly active strong solid acid catalysts with good hydrothermal stability has become a key determinant for success, because bio-oil's complexity includes large amounts of water. Temperatures of 120°C or more are needed for satisfactory kinetics. Batch upgrading of a model bio-oil (phenol/water/acetic acid/acetaldehyde/hydroxyacetone/d-glucose/2-hydroxymethylfuran) over five water-tolerant solid acid catalysts (Dowex50WX2, Amberlyst15, Amberlyst36, silica sulfuric acid (SSA) and Cs(2.5)H(0.5)PW(12)O(40) supported on K-10 clay (Cs(2.5)/K-10, 30wt.%)) with 1-octene/1-butanol were studied at 120°C/3h. SSA, , exhibited the highest water tolerance and activity. Upgrading using olefin/1-butanol is complex, involving many simultaneous competing esterification, etherification, olefin hydration, phenol alkylation, aldol condensation, sugar dehydration etc. reactions.

  16. 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.

  17. Sorption of tylosin A, D, and A-aldol and degradation of tylosin A in soils.

    PubMed

    Sassman, Stephen A; Sarmah, Ajit K; Lee, Linda S

    2007-08-01

    Heightened concerns regarding the potential impact on soil and water quality of veterinary antibiotics warrant a better understanding of the environmental fate of antibiotics in soil. Sorption of the macrolides tylosin A (TA), tylosin D, and TA-aldol was measured in several soils and evaluated with respect to soil pH, organic matter content, percentage clay, and cation-exchange capacity (CEC). Tylosin and related compounds exhibit similar sorption characteristics and generally are strongly sorbed, with sorption being well and positively correlated to surface area, clay content, and CEC. Sorption coefficients normalized by CEC were within a narrow range (10(4.1+/-0.21 L/molc) for all but one soil; however, good extraction recoveries with only methanol for most soils suggested that hydrophobic processes also contribute to sorption. Aerobic degradation of TA over a three-month period in two freshly collected agricultural soils and 60Co-irradiated soils indicated that both abiotic and microbial processes contribute to TA transformation. The abiotic process was much slower and dominated in the first two weeks, followed by rapid microbial degradation within 3 d. Three primary degradation products were identified using liquid chromatography with full-scan mass spectrometry, with unconfirmed identifications of TA having the aldehyde group oxidized to an acid (m/z = 932) in both soils and tyslosin B (m/z = 772) as well as tylosin B having the aldehyde group oxidized to an acid (m/z = 788) in the sandy soil.

  18. A novel acyclic oligomycin A derivative formed via retro-aldol rearrangement of oligomycin A.

    PubMed

    Lysenkova, Lyudmila N; Turchin, Konstantin F; Korolev, Alexander M; Bykov, Evgenyi E; Danilenko, Valery N; Bekker, Olga B; Trenin, Alexey S; Elizarov, Sergei M; Dezhenkova, Lyubov G; Shtil, Alexander A; Preobrazhenskaya, Maria N

    2012-08-01

    The antibiotic oligomycin A in the presence of K(2)CO(3) and n-Bu(4)NHSO(4) in chloroform in phase-transfer conditions afforded a novel derivative through the initial retro-aldol fragmentation of the 8,9 bond, followed by further transformation of the intermediate aldehyde. NMR, MS and quantum chemical calculations showed that the novel compound is the acyclic oligomycin A derivative, in which the 8,9 carbon bond is disrupted and two polyfunctional branches are connected with spiroketal moiety in positions C-23 and C-25. The tri-O-acetyl derivative of the novel derivative was prepared. The acyclic oligomycin A derivative retained the ability to induce apoptosis in tumor cells at low micromolar concentrations, whereas its antimicrobial potencies decreased substantially. The derivative virtually lost the inhibitory activity against F(0)F(1) ATP synthase-containing proteoliposomes, strongly suggesting the existence of the target(s) beyond F(0)F(1) ATP synthase that is important for the antitumor potency of oligomycin A.

  19. Asymmetric synthesis of chiral dihydrothiopyrans via an organocatalytic enantioselective formal thio [3 + 3] cycloaddition reaction with binucleophilic bisketone thioethers.

    PubMed

    Wang, Shengzheng; Zhang, Yongqiang; Dong, Guoqiang; Wu, Shanchao; Zhu, Shiping; Miao, Zhenyuan; Yao, Jianzhong; Li, Hao; Li, Jian; Zhang, Wannian; Sheng, Chunquan; Wang, Wei

    2013-11-01

    An unprecedented organocatalytic highly enantioselective approach to a 3,4-dihydro-2H-thiopyran scaffold with two contiguous stereogenic centers has been implemented through a formal thio [3 + 3] cycloaddition process involving a Michael-aldol condensation cascade sequence. Notably, a new class of binucleophilic bisketone thioethers is designed for the process. Furthermore, the fine-tuning of their reactivity enables the cascade process to proceed with highly regioselectively.

  20. Synthesis of pyrazole containing α-amino acids via a highly regioselective condensation/aza-Michael reaction of β-aryl α,β-unsaturated ketones.

    PubMed

    Gilfillan, Lynne; Artschwager, Raik; Harkiss, Alexander H; Liskamp, Rob M J; Sutherland, Andrew

    2015-04-21

    A synthetic approach for the preparation of a new class of highly conjugated unnatural α-amino acids bearing a 5-arylpyrazole side-chain has been developed. Horner-Wadsworth-Emmons reaction of an aspartic acid derived β-keto phosphonate ester with a range of aromatic aldehydes gave β-aryl α,β-unsaturated ketones. Treatment of these with phenyl hydrazine followed by oxidation allowed the regioselective synthesis of pyrazole derived α-amino acids. As well as evaluating the fluorescent properties of the α-amino acids, their synthetic utility was also explored with the preparation of a sulfonyl fluoride derivative, a potential probe for serine proteases.

  1. Condensed imidazo-1,2,4-azines. 15. Reaction of 1,2-diaminobenzimidazole with 5-phenyl-2,3-dihydrofuran-2,3-dione

    SciTech Connect

    Kruglenko, V.P.; Gnidets, V.P.; Klyuev, N.A.; Povstyanoi, M.V.

    1987-10-01

    The reaction of 1,2-diaminobenzimidazole with 5-phenyl-2,3-dihydrofuran-2,3-dione in acetic acid gave a mixture of 2-benzoylmethyl-1,2,4-triazino (2,3-..cap alpha..)-benzimidazol-4H-3-one and 3-benzoylmethyl-1,2,4-triazino(2,3-..cap alpha..)benzimidazol-1H-2-one, the intramolecular cyclization of which gave isomeric 2-phenylfuro-(5,4-e)- and 2-phenylfuro(4,5-e)-1,2,4-triazino(2,3-..cap alpha..)benzimidazoles. Only the corresponding furo(4,5-e)-1,2,4-triazino(2,3-..cap alpha..)benzimidazole was isolated when the reaction was carried out in sulfuric acid. The IR spectra of KBr pellets of the compounds were recorded with a UR-20 spectrometer. The electronic absorption spectra of solutions in dioxane were obtained with a Specord UV-vis spectrophotometer. The mass spectra were recorded with a Varian MAT-311a spectrometer. The quantum-chemical calculations were made by the Pariser-Parr-Pople (PPP) method with the standard parametrization.

  2. Condensate Mixtures and Tunneling

    SciTech Connect

    Timmermans, E.

    1998-09-14

    The experimental study of condensate mixtures is a particularly exciting application of the recently developed atomic-trap Bose-Einstein condensate (BEC) technology: such multiple condensates represent the first laboratory systems of distinguishable boson superfluid mixtures. In addition, as the authors point out in this paper, the possibility of inter-condensate tunneling greatly enhances the richness of the condensate mixture physics. Not only does tunneling give rise to the oscillating particle currents between condensates of different chemical potentials, such as those studied extensively in the condensed matter Josephson junction experiments, it also affects the near-equilibrium dynamics and stability of the condensate mixtures. In particular, the stabilizing influence of tunneling with respect to spatial separation (phase separation) could be of considerable practical importance to the atomic trap systems. Furthermore, the creation of mixtures of atomic and molecular condensates could introduce a novel type of tunneling process, involving the conversion of a pair of atomic condensate bosons into a single molecular condensate boson. The static description of condensate mixtures with such type of pair tunneling suggests the possibility of observing dilute condensates with the liquid-like property of a self-determined density.

  3. 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.

  4. Sulfided heterogeneous, bimetallic RuMo catalysts derived from mixtures of Ru{sub 3}(CO){sub 12} (or RuCl{sub 3}) and a molybdenum heteropolyanion. The reactions of ethanol with tetrahydroquinoline

    SciTech Connect

    Koo, Sang-Man; Ryan, D.; Laine, R.M.

    1992-09-01

    Efforts have been made to develop Ru/Mo bimetallic catalyst systems for hydrodenitrogenation (HDN) of tetrahydroquinoline (THQ)- In the course of these studies, it was discovered that in ethanol, under H{sub 2} and in the presence Of CS2, Precatalyst solutions containing Ru [as Ru{sub 3} (CO){sub 12} or RuCl{sub 3}] and Mo [as the H{sub 3}PMO{sub 12}0{sub 40} heteropolyanion (HPA)] decompose to form bimetallic, sulfided particles. Particle diameters run from 0.1 to 5 {mu}m depending on the rate of stirring. Catalyst particles with sizes ranging from 0.1--1 {mu}m can be prepared reproducibly. BET measured surface areas for these size particles ranged from 2 to 20 m2/g. These sulfided particles were found to catalyze, at temperatures of 200--250{degrees}C and hydrogen pressures of 200--1000 psig H{sub 2}, the N-ethylation of THQ to form NEt-THQ; rather than the formation of propylcyclohexane or propylbenzene, reaction products expected for HDN of THQ. Monometallic heterogeneous catalysts prepared from the individual precatalyst complexes, under identical conditions, show minimal activity for N-ethylation by comparison with the bimetallic catalyst. In the absence of H{sub 2}, the reaction proceeds such that THQ is converted to Q, N-EtTHQ, N-C{sub 6}H{sub 9}-THQ, and N-C{sub 6}H{sub 13}-THQ. The latter products appear to arise via acetaldehyde, formed as an intermediate by dehydrogenation of ethanol. Acetaldehyde either condenses with THQ to form N-Et-THQ, or self condenses (aldol condensation) prior to reaction with THQ thereby giving higher homolog alkylation products.

  5. Sulfided heterogeneous, bimetallic RuMo catalysts derived from mixtures of Ru sub 3 (CO) sub 12 (or RuCl sub 3 ) and a molybdenum heteropolyanion. The reactions of ethanol with tetrahydroquinoline

    SciTech Connect

    Koo, Sang-Man; Ryan, D.; Laine, R.M.

    1992-01-01

    Efforts have been made to develop Ru/Mo bimetallic catalyst systems for hydrodenitrogenation (HDN) of tetrahydroquinoline (THQ)- In the course of these studies, it was discovered that in ethanol, under H{sub 2} and in the presence Of CS2, Precatalyst solutions containing Ru (as Ru{sub 3} (CO){sub 12} or RuCl{sub 3}) and Mo (as the H{sub 3}PMO{sub 12}0{sub 40} heteropolyanion (HPA)) decompose to form bimetallic, sulfided particles. Particle diameters run from 0.1 to 5 {mu}m depending on the rate of stirring. Catalyst particles with sizes ranging from 0.1--1 {mu}m can be prepared reproducibly. BET measured surface areas for these size particles ranged from 2 to 20 m2/g. These sulfided particles were found to catalyze, at temperatures of 200--250{degrees}C and hydrogen pressures of 200--1000 psig H{sub 2}, the N-ethylation of THQ to form NEt-THQ; rather than the formation of propylcyclohexane or propylbenzene, reaction products expected for HDN of THQ. Monometallic heterogeneous catalysts prepared from the individual precatalyst complexes, under identical conditions, show minimal activity for N-ethylation by comparison with the bimetallic catalyst. In the absence of H{sub 2}, the reaction proceeds such that THQ is converted to Q, N-EtTHQ, N-C{sub 6}H{sub 9}-THQ, and N-C{sub 6}H{sub 13}-THQ. The latter products appear to arise via acetaldehyde, formed as an intermediate by dehydrogenation of ethanol. Acetaldehyde either condenses with THQ to form N-Et-THQ, or self condenses (aldol condensation) prior to reaction with THQ thereby giving higher homolog alkylation products.

  6. 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.

  7. 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.

  8. Asymmetric Morita-Baylis-Hillman Reaction: Catalyst Development and Mechanistic Insights Based on Mass Spectrometric Back-Reaction Screening.

    PubMed

    Isenegger, Patrick G; Bächle, Florian; Pfaltz, Andreas

    2016-12-05

    An efficient protocol for the evaluation of catalysts for the asymmetric Morita-Baylis-Hillman (MBH) reaction was developed. By mass spectrometric back-reaction screening of quasi-enantiomeric MBH products, an efficient bifunctional phosphine catalyst was identified that outperforms literature-known catalysts in the MBH reaction of methyl acrylate with aldehydes. The close match between the selectivities measured for the forward and back reaction and kinetic measurements provided strong evidence that the aldol step and not the subsequent proton transfer is rate- and enantioselectivity-determining.

  9. [Development of highly stereoselective reactions utilizing heteroatoms--asymmetric synthesis of alpha-substituted serines].

    PubMed

    Sano, S

    2000-01-01

    This article reviews the efficient methods for diastereoselective and enantioselective syntheses of alpha-substituted serines. A newly designed bislactim ether, ethyl (5S)- or (5R)-3,6-diethoxy-2,5-dihydro-5-isopropyl-2-pyrazinecarboxylate, was treated with base or Lewis acid-tertiary amine to generate an enolate or enaminate (imine anion, metalloenamine). Alkylation or aldol-type reaction with the resultant enolate or enaminate proceeded in a highly diastereoselective manner to give the corresponding alkylated or aldol products, respectively. Reduction of these products with diisobutylaluminum hydride (DIBAL) followed by hydrolysis with hydrochloric acid afforded the desirable alpha-substituted serines. The enantioselective aldol-type reaction of an achiral bislactim ether, ethyl 3,6-diethoxy-2,5-dihydro-2-pyrazinecarboxylate, was also investigated by employing Sn(OSO2CF3)2-triethylamine in the presence of an external chiral ligand, (--)-sparteine. Not only a stoichiometric amount, but also a catalytic amount of (--)-sparteine promoted the highly enantioselective aldol-type reactions. Interestingly, the stereoselective outcome of the Sn(II)-mediated reaction differed from that of the Mg(II)-mediated one in the aldol-type reaction of the bislactim ethers with aliphatic aldehydes. On the other hand, chemoenzymatic synthesis of enantiomerically pure alpha-substituted serines must also be a convenient and useful procedure. Porcine liver esterase (PLE) or rabbit liver esterase (RLE) catalyzed hydrolysis of the pro-S ester group of diethyl alpha-alkyl-alpha-(benzyloxycarbonylamino)malonates to afford (R)-ethyl alpha-alkyl-alpha-(benzyloxycarbonylamino)malonates each in excellent enantiomeric excess. Enantiodivergent reductions of these acid esters readily proceeded to furnish both the corresponding enantiomeric alpha-substituted serines. Finally, the application of these methodologies mentioned above to a total synthesis of ISP-I (a potent immunosuppressive principle in

  10. 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.

  11. 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.

  12. Sub-Equimolar Hydrolysis and Condensation of Organophosphates

    DOE PAGES

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

    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.

  13. EPRI condensate polisher guidelines

    SciTech Connect

    Larkin, B.A.; Webb, L.C.; Sawochka, S.G.; Crits, G.J.; Pocock, F.J.; Wirth, L.

    1995-01-01

    Cycle chemistry is one of the most important contributors to the loss of availability of generating units. Condensate polishing can significantly improve cycle chemistry by improving cycle water quality and minimizing the transport of contaminants in the power cycle. The EPRI-funded project described in this paper developed comprehensive guidelines for condensate polishing based upon information gathered from utility surveys, equipment vendors, and resin suppliers. Existing literature was also surveyed for pertinent input. Comprehensive guidelines which outline guidance for design, operation, maintenance, surveillance, management, and retrofitting of condensate polishing systems were developed. Economics of condensate polishing were evaluated and a roadmap for economic evaluation for utilities to follow was produced.

  14. 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...

  15. 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...

  16. 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

  17. 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.

  18. 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.

  19. Formation of activated biomolecules by condensation on mineral surfaces--a comparison of peptide bond formation and phosphate condensation.

    PubMed

    Georgelin, Thomas; Jaber, Maguy; Bazzi, Houssein; Lambert, Jean-François

    2013-10-01

    Many studies have reported condensation reactions of prebiotic molecules, such as the formation of peptide bonds between amino acids, to occur to some degree on mineral surfaces. We have studied several such reactions on the same divided silica. When drying steps are applied, the equilibria of peptide formation from glycine, and polyphosphate formation from monophosphate, are displaced to the right because these reactions are dehydrating condensations, accompanied by the emission of water. In contrast, the equilibrium of AMP dismutation is not significantly favored by drying. The silica surface plays little role (if any) in the thermochemistry of the condensation reactions, but is does play a significant kinetic role by acting as a catalyst, lowering the condensation temperatures with respect to bulk solids. Of course, the surface also catalyzes the inverse hydrolysis reactions.

  20. Rapid Construction of the Aza-Propellane Core of Acutumine via a Photochemical [2+2] Cycloaddition Reaction

    PubMed Central

    Navarro, Raul; Reisman, Sarah E.

    2012-01-01

    Synthetic efforts toward the chlorinated propellane alkaloid acutumine (1) are described. The key vicinal quaternary centers were constructed by a photochemical [2+2] cycloaddition reaction of a furanyl-tetrahydroindolone. Dihydroxylation of the [2+2] product enabled a tandem retro-aldol/intramolecular ketalization reaction, which revealed the aza-propellane core of 1 while generating an unusual, caged, pentacyclic hemi-ketal product. PMID:22891873

  1. Chiral BINOL-derived phosphoric acids: privileged Brønsted acid organocatalysts for C-C bond formation reactions.

    PubMed

    Zamfir, Alexandru; Schenker, Sebastian; Freund, Matthias; Tsogoeva, Svetlana B

    2010-12-07

    BINOL-derived phosphoric acids have emerged during the last five years as powerful chiral Brønsted acid catalysts in many enantioselective processes. The most successful transformations carried out with chiral BINOL phosphates include C-C bond formation reactions. The recent advances have been reviewed in this article with a focus being placed on hydrocyanations, aldol-type, Mannich, Friedel-Crafts, aza-ene-type, Diels-Alder, as well as cascade and multi-component reactions.

  2. A four-component reaction involving in situ generated organometallic reagents: straightforward access to β-amino esters.

    PubMed

    Le Gall, Erwan; Léonel, Eric

    2013-04-22

    Four in one: A straightforward synthesis of β(2,3)-amino esters is described through a new zinc-mediated, cobalt-catalyzed four-component reaction between organic bromides, alkyl acrylates, amines, and aldehydes (see scheme). Synthesis involves a Mannich-related conjugate addition/aza-aldol domino sequence, allowing the formation of three single bonds in one step. A reaction mechanism, emphasizing the crucial role of zinc salts, is described.

  3. 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

  4. A Rh(ii)-catalyzed three-component reaction of 3-diazooxindoles with N,N-disubstituted anilines and glyoxylates for the synthesis of 3-aryl-3-substituted oxindoles.

    PubMed

    Jia, Shi-Kun; Song, Long-Long; Lei, Yu-Bing; Gopi Krishna Reddy, A; Xing, Dong; Hu, Wen-Hao

    2016-11-02

    A simple and effective method for the synthesis of 3-aryl-3-substituted oxindole derivatives via a [Rh]-catalyzed three-component reaction of 3-diazooxindoles with N,N-disubstituted anilines and glyoxylates is developed. This transformation is proposed to proceed through an intermolecular aldol-type trapping of zwitterionic intermediates.

  5. 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.

  6. Key condenser failure mechanisms

    SciTech Connect

    Buecker, B.

    2009-04-15

    Eight practical lessons highlight many of the factors that can influence condenser tube corrosion at coal-fired utilities and the effects contaminant in-leakage can have on steam generating units. 1 ref., 4 figs.

  7. 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.

  8. Molecular equilibrium with condensation

    NASA Astrophysics Data System (ADS)

    Sharp, C. M.; Huebner, W. F.

    1990-02-01

    Minimization of the Gibbs energy of formation for species of chemical elements and compounds in their gas and condensed phases determines their relative abundances in a mixture in chemical equilibrium. The procedure is more general and more powerful than previous abundance determinations in multiphase astrophysical mixtures. Some results for astrophysical equations of state are presented, and the effects of condensation on opacity are briefly indicated.

  9. 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.

  10. Isoxazole-embedded allylic zinc reagent for the diastereoselective preparation of highly functionalized aldol-type derivatives bearing a stereocontrolled quaternary center.

    PubMed

    Klier, Lydia; Diène, Coura R; Schickinger, Manuel; Metzger, Albrecht; Wagner, Andreas J; Karaghiosoff, Konstantin; Marek, Ilan; Knochel, Paul

    2014-10-20

    Highly functionalized aldol-type products bearing a β-quaternary center and a stereoselectively controlled γ-hydroxy function are readily prepared by the diastereoselective addition of an allylic zinc reagent embedded in an isoxazole ring to various aromatic and heteroaromatic aldehydes, in the presence of Lewis acids, such as MgCl2 or LaCl3⋅2 LiCl. After reductive cleavage of the N-O bond by using Fe, NH4Cl, aldol-type products bearing a stereocontrolled β-quaternary center and a γ-hydroxy group were observed. The benzylic reactivity of the isoxazolylmethylzinc reagent towards other electrophiles, such as acid chlorides, aryl and allylic halides, as well as aldehydes in the presence of BF3⋅OEt2 are also described.

  11. 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.

  12. 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.

  13. Simple simulations of DNA condensation.

    PubMed Central

    Stevens, M J

    2001-01-01

    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 phenomenon 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. PMID:11159388

  14. 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.

  15. 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

  16. 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.

  17. Nanostructure-induced DNA condensation

    NASA Astrophysics Data System (ADS)

    Zhou, Ting; Llizo, Axel; Wang, Chen; Xu, Guiying; Yang, Yanlian

    2013-08-01

    The control of the DNA condensation process is essential for compaction of DNA in chromatin, as well as for biological applications such as nonviral gene therapy. This review endeavours to reflect the progress of investigations on DNA condensation effects of nanostructure-based condensing agents (such as nanoparticles, nanotubes, cationic polymer and peptide agents) observed by using atomic force microscopy (AFM) and other techniques. The environmental effects on structural characteristics of nanostructure-induced DNA condensates are also discussed.

  18. 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.

  19. Recovery of condensate water quality in power generator's surface condenser

    NASA Astrophysics Data System (ADS)

    Kurniawan, Lilik Adib

    2017-03-01

    In PT Badak NGL Plant, steam turbines are used to drive major power generators, compressors, and pumps. Steam exiting the turbines is condensed in surface condensers to be returned to boilers. Therefore, surface condenser performance and quality of condensate water are very important. One of the recent problem was caused by the leak of a surface condenser of Steam Turbine Power Generator. Thesteam turbine was overhauled, leaving the surface condenser idle and exposed to air for more than 1.5 years. Sea water ingress due to tube leaks worsens the corrosionof the condenser shell. The combination of mineral scale and corrosion product resulting high conductivity condensate at outlet condenser when we restarted up, beyond the acceptable limit. After assessing several options, chemical cleaning was the best way to overcome the problem according to condenser configuration. An 8 hour circulation of 5%wt citric acid had succeed reducing water conductivity from 50 μmhos/cm to below 5 μmhos/cm. The condensate water, then meets the required quality, i.e. pH 8.3 - 9.0; conductivity ≤ 5 μmhos/cm, therefore the power generator can be operated normally without any concern until now.

  20. 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.

  1. 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.

  2. Gravitational vacuum condensate stars

    PubMed Central

    Mazur, Pawel O.; Mottola, Emil

    2004-01-01

    A new final state of gravitational collapse is proposed. By extending the concept of Bose–Einstein condensation to gravitational systems, a cold, dark, compact object with an interior de Sitter condensate pv = -ρv and an exterior Schwarzschild geometry of arbitrary total mass M is constructed. These regions are separated by a shell with a small but finite proper thickness ℓ of fluid with equation of state p = +ρ, replacing both the Schwarzschild and de Sitter classical horizons. The new solution has no singularities, no event horizons, and a global time. Its entropy is maximized under small fluctuations and is given by the standard hydrodynamic entropy of the thin shell, which is of the order kBℓMc/, instead of the Bekenstein–Hawking entropy formula, SBH = 4πkBGM2/c. Hence, unlike black holes, the new solution is thermodynamically stable and has no information paradox. PMID:15210982

  3. Sidestream condensate polishing for PWRs

    SciTech Connect

    Shor, S.W.W.; Yim, S.L.; Rios, J.; Liu, J.

    1986-06-01

    Condensate polishers are used in power plant condensate system to remove both particulate matter and ionized corrodents. Their conventional location is just downstream of the hotwell pumps (condensate pumps). Most polisher installations have enough flow capacity to polish 100% of the condensate. This inline configuration has some disadvantage, including a flow that varies with unit load and tends to disturb the polisher beds and reduce their effectiveness, and a potential for interrupting flow to the feedwater pumps. An alternate arrangement where water is extracted from either the condenser or the condensate system, polished and returned to the system, has been used in a few plants. Three different ways of doing this have been used: divide the condenser hotwell into two parts, one of which receives condensate from the tube bundles and the other of which is sheltered. Take unpolished condensate from the first part, purify it and return it to the other part from which the condensate pumps take suction; take unpolished condensate from one end of a divided header on the suction side of the hotwell pumps and after polishing it return it to the other end; and take unpolished condensate from a header on the discharge side of the condensate pumps, purify it and return it to the condensate system a short distance downstream. The three variants are analyzed in this report. It is concluded that the variant where the connections are on the discharge side of the condensate pumps is the most desirable for retrofitting, in all cases being far easier to retrofit than an inline polisher. In many cases it will be most desirable for new construction.

  4. 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.

  5. Asymmetric condensed dark matter

    SciTech Connect

    Aguirre, Anthony; Diez-Tejedor, Alberto E-mail: alberto.diez@fisica.ugto.mx

    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.

  6. 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.

  7. New technology in condensate polishing

    SciTech Connect

    Kunin, R.; Salem, E.; Libutti, B. . Water Div.)

    1992-08-01

    Sulfonic acid ion exchange resins. when carried into a boiler or steam generator, thermally decompose releasing large amounts of corrosive, sulfates. Replacement of the sulfonic acid resin with a carboxylic acid resin would eliminate this source of contamination. The sulfonic acid resin is a strong acid: the carboxylic acid resin is a weak acid. The carboxylic acid resin alone is not capable of splitting salts which limits its use to mixed resin beds or to its use in single or individual beds with feeds of high alkalinity or high pH values. Laboratory, pilot plant and full scale plant tests compared the two resins in precoat filters. When the resins in mixed beds were in the acid form, the weakly acid resin was almost as effective in removing sodium ion as the strongly acid resin. In the ammonium form. the weakly acid resin was generally more effective in removing sodium than the strongly acid resin. Condensate polishing reduced the sodium ion to a few parts per billion (ppB). Complete resin separation before regeneration is more important for the weakly acid resin than for the strongly acid resin. Another development found that the hydrazine reaction with oxygen could be catalyzed by powdered activated carbon combined with microfibers on a Powdex substrate. The carbon should be thoroughly washed to reduce its residual sodium content. In plant tests, the carbon reduced the oxygen concentration in condensate about 50% during startup. In preliminary tests believed to be typical, carbon lowered the oxygen concentration below 10 ppB in about 6 hours compared to 18 hours without the carbon. Oxygen is also reduced during normal operation.

  8. 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

  9. 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.

  10. 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.

  11. Nanocarbon condensation in detonation

    NASA Astrophysics Data System (ADS)

    Bastea, Sorin

    2017-02-01

    We analyze the definition of the Gibbs free energy of a nanoparticle in a reactive fluid environment, and propose an approach for predicting the size of carbon nanoparticles produced by the detonation of carbon-rich explosives that regards their condensation as a nucleation process and takes into account absolute entropy effects of the cluster population. The results are consistent with experimental observations and indicate that such entropy considerations are important for determining chemical equilibrium states in energetic materials that contain an excess of carbon. The analysis may be useful for other applications that deal with the nucleation of nanoparticles under reactive conditions.

  12. 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.

  13. Nanocarbon condensation in detonation

    PubMed Central

    Bastea, Sorin

    2017-01-01

    We analyze the definition of the Gibbs free energy of a nanoparticle in a reactive fluid environment, and propose an approach for predicting the size of carbon nanoparticles produced by the detonation of carbon-rich explosives that regards their condensation as a nucleation process and takes into account absolute entropy effects of the cluster population. The results are consistent with experimental observations and indicate that such entropy considerations are important for determining chemical equilibrium states in energetic materials that contain an excess of carbon. The analysis may be useful for other applications that deal with the nucleation of nanoparticles under reactive conditions. PMID:28176827

  14. 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.

  15. 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

  16. New Developments in Chiral Cooperative Ion Pairing Organocatalysis by Means of Ammonium Oxyanions and Fluorides: From Protonation to Deprotonation Reactions.

    PubMed

    Legros, Fabien; Oudeyer, Sylvain; Levacher, Vincent

    2016-10-13

    This personal account summarizes our contribution to the ion pairing organocatalysis mainly by use of chiral quaternary or tertiary ammonium fluorides, aryloxides and carboxylates. Starting from an experimental observation, we were able to develop several approaches for the enantioselective protonation of silyl enolates and enol esters giving rise to chiral carbonyl compounds bearing a stereogenic center at the α-position. Moving from protonation to deprotonation reactions, chiral ammonium ion pair catalysts were successfully applied to several asymmetric transformations such as an Henry reaction or a direct vinylogous aldol reaction to cite a few. An outlook of further possible developments in this field of research will also be discussed.

  17. An acidic layered clay is combined with a basic layered clay for one-pot sequential reactions.

    PubMed

    Motokura, Ken; Fujita, Noriaki; Mori, Kohsuke; Mizugaki, Tomoo; Ebitani, Kohki; Kaneda, Kiyotomi

    2005-07-13

    A Ti4+-exchanged montmorillonite (Ti4+-mont) and a hydrotalcite (HT) are strong solid Brønsted acid and base, and these two clay catalysts could be used in a single reactor without neutralization of active sites. Because the Ti4+-mont have active acid site in the narrow interlayers, the base sites of large HT particles show no interaction with the acid sites. A variety of acid and base reactions, such as esterification, acetalization, deacetalization, aldol reaction, Michael reaction, and epoxidation, proceeded using both the Ti4+-mont and the HT in a single reactor.

  18. Cosmic curvature and condensation

    NASA Technical Reports Server (NTRS)

    Harwit, Martin

    1992-01-01

    It is shown that the universe may consist of a patchwork of domains with different Riemann curvature constants k = 0, +/-1. Features of a phase transition in which flat space breaks up in a transition 2k0 - k(-) + k(+) with initial scale factors R(-) = R(+) are postulated and explored. It is shown that such a transition is energetically permitted, has the equivalent of a Curie temperature, and can lead in a natural way to the formation of voids and galaxies. It is predicted that, if the ambient universe on average is well fitted by a purely k(-) space, with only occasional domains of k(+) containing galaxies, a density parameter of (A(z sub c + 1)) super -1 should be expected, where z sub c represents the redshift of the earliest objects to have condensed, and A takes on values ranging from about 5 to 3. Present observations of quasars would suggest a density of about 0.03 or 0.05, respectively, but it could be lower if earlier condensation took place.

  19. Pion condensation in holographic QCD

    SciTech Connect

    Albrecht, Dylan; Erlich, Joshua

    2010-11-01

    We study pion condensation at zero temperature in a hard-wall holographic model of hadrons with isospin chemical potential. We find that the transition from the hadronic phase to the pion condensate phase is first order except in a certain limit of model parameters. Our analysis suggests that immediately across the phase boundary the condensate acts as a stiff medium approaching the Zel'dovich limit of equal energy density and pressure.

  20. Condensation heat transfer in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Chow, L. C.; Parish, R. C.

    1986-01-01

    In the present treatment of the condensation heat transfer process in a microgravity environment, two mechanisms for condensate removal are analyzed in light of two problems: (1) film condensation on a flat, porous plate, with condensate being removed by wall suction; and (2) the analytical prediction of the heat transfer coefficient of condensing annular flows, where the condensate film is driven by vapor shear. Both suction and vapor shear can effectively drain the condensate, ensuring continuous operation in microgravity.

  1. Pd-Catalyzed Autotandem Reactions with N-Tosylhydrazones. Synthesis of Condensed Carbo- and Heterocycles by Formation of a C-C Single Bond and a C═C Double Bond on the Same Carbon Atom.

    PubMed

    Paraja, Miguel; Valdés, Carlos

    2017-04-05

    A new Pd-catalyzed autotandem reaction is introduced that consists of the cross-coupling of a benzyl bromide with a N-tosylhydrazone followed by an intramolecular Heck reaction with an aryl bromide. During the process, a single and a double C-C bond are formed on the same carbon atom. Two different arrangements for the reactive functional groups are possible, rendering great flexibility to the transformation. The same strategy led to 9-methylene-9H-fluorenes, 9-methylene-9H-xanthenes, 9-methylene-9,10-dihydroacridines, and also dihydropyrroloisoquinoline and dihydroindoloisoquinoline derivatives.

  2. Condenser for photolithography system

    DOEpatents

    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.

  3. 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.

  4. TiCl4-promoted Baylis-Hillman reaction: mechanistic rationale toward product distribution and stereoselectivity.

    PubMed

    Patel, Chandan; Sunoj, Raghavan B

    2010-01-15

    The mechanism of TiCl(4)-promoted Baylis-Hillman reaction between methyl vinyl ketone (MVK) and acetaldehyde, in the absence of any base, is studied using the mPW1K density functional theory. The study focuses on several mechanistic intricacies as well as selectivity issues at each step of the reaction. The minimum energy pathway for this reaction involves three major steps such as a chloride transfer resulting in a chloro-enolate, titanium-mediated aldol reaction, and elimination of HCl or HOTiCl(3). Both s-cis and s-trans conformers of MVK are considered along with various modes of chloride transfer involving different complexes between TiCl(4), aldehyde, and MVK. Chloride transfer is found to be kinetically more favored for s-cis-MVK than for s-trans-MVK. The diastereoselectivity in the next step, i.e., Ti-mediated aldol reaction between the enolate and aldehyde, is found to be dependent on the geometry of the enolate, wherein anti and syn BH products are predicted for Z and E enolates, respectively. An interesting secondary orbital interaction between the oxygen atoms of the enolate and aldehyde moieties in the transition states for the C-C bond formation is identified as one of the contributing factors toward the predicted diastereoselectivity in the formation of the alpha-chloromethyl aldol product (P2). It has earlier been reported that under different experimental conditions, any of the three products such as (i) a normal BH product (P1), (ii) 2-(chloromethyl)vinyl ketones (P3), and (iii) alpha-chloro methyl aldol could be generated (Scheme 1 ). The present study offers valuable insights toward rationalizing the observed product distribution as well as diastereoselectivity in TiCl(4)-promoted BH reaction under base-free conditions. The computed energetics indicate that when MVK is employed as the Michael acceptor, the formation of 2-(choromethyl)vinyl ketone is the preferred product rather than the corresponding normal BH product, consistent with the known

  5. 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.

  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. Chromatin condensation during terminal erythropoiesis.

    PubMed

    Zhao, Baobing; Yang, Jing; Ji, Peng

    2016-09-02

    Mammalian terminal erythropoiesis involves gradual but dramatic chromatin condensation steps that are essential for cell differentiation. Chromatin and nuclear condensation is followed by a unique enucleation process, which is believed to liberate more spaces for hemoglobin enrichment and enable the generation of a physically flexible mature red blood cell. Although these processes have been known for decades, the mechanisms are still unclear. Our recent study reveals an unexpected nuclear opening formation during mouse terminal erythropoiesis that requires caspase-3 activity. Major histones, except H2AZ, are partially released from the opening, which is important for chromatin condensation. Block of the nuclear opening through caspase inhibitor or knockdown of caspase-3 inhibits chromatin condensation and enucleation. We also demonstrate that nuclear opening and histone release are cell cycle regulated. These studies reveal a novel mechanism for chromatin condensation in mammalia terminal erythropoiesis.

  8. Artificial Force Induced Reaction (AFIR) Method for Exploring Quantum Chemical Potential Energy Surfaces.

    PubMed

    Maeda, Satoshi; Harabuchi, Yu; Takagi, Makito; Taketsugu, Tetsuya; Morokuma, Keiji

    2016-10-01

    In this account, a technical overview of the artificial force induced reaction (AFIR) method is presented. The AFIR method is one of the automated reaction-path search methods developed by the authors, and has been applied extensively to a variety of chemical reactions, such as organocatalysis, organometallic catalysis, and photoreactions. There are two modes in the AFIR method, i.e., a multicomponent mode and a single-component mode. The former has been applied to bimolecular and multicomponent reactions and the latter to unimolecular isomerization and dissociation reactions. Five numerical examples are presented for an Aldol reaction, a Claisen rearrangement, a Co-catalyzed hydroformylation, a fullerene structure search, and a nonradiative decay path search in an electronically excited naphthalene molecule. Finally, possible applications of the AFIR method are discussed.

  9. 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.

  10. 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.

  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. Steam condenser thermal design theories

    NASA Astrophysics Data System (ADS)

    Davidson, B. J.

    Test data and prediction methods for condensation in steam condenser tube banks are reviewed. Standards for thermal rating; effect of vapor velocity; vapor shear and inundation in tube banks; correction factors to the Nusselt equation; and equations for the combined effect of vapor shear and inundation are discussed. Effects of noncondensible gases; tube side heat transfer; and expressions for combined tube side and shell side heat transfer are considered. Frictional, gravitational, momentum, and pressure drop trends; and the role of access lanes to reduce pressure drop are outlined. Computer models of condensers, including algebraic representations of the field equations, are summarized.

  13. Condensation heat transfer under a microgravity environment

    NASA Technical Reports Server (NTRS)

    Chow, L. C.

    1986-01-01

    A description of the condensation heat transfer process in microgravity is given. A review of the literature is also reported. The most essential element of condensation heat transfer in microgravity is the condensate removal mechanism. Two mechanisms for condensate removal are analyzed by looking into two problems. The first problem is concerned with film condensation on a flat porous plate with the condensate being removed by suction at the wall. The second problem is an analytical prediction of the heat transfer coefficient for condensing annular flows with the condensate film driven by the vapor shear. It is concluded that both suction and vapor shear can effectively drain the condensate to ensure continuous operation of the condensers operated under a microgravity environment. It is recommended that zero-g flight experiments be carried out to verify the prediction made in the present report. The results contained in this report should also aid in the design of future space condensers.

  14. Monitoring by Control Technique - Condensers

    EPA Pesticide Factsheets

    Stationary source emissions monitoring is required to demonstrate that a source is meeting the requirements in Federal or state rules. This page is about condenser control techniques used to reduce pollutant emissions.

  15. 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...

  16. 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.

  17. 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.

  18. Towards the development of continuous, organocatalytic, and stereoselective reactions in deep eutectic solvents

    PubMed Central

    Brenna, Davide; Massolo, Elisabetta; Puglisi, Alessandra; Rossi, Sergio; Celentano, Giuseppe; Capriati, Vito

    2016-01-01

    Different deep eutectic solvent (DES) mixtures were studied as reaction media for the continuous synthesis of enantiomerically enriched products by testing different experimental set-ups. L-Proline-catalysed cross-aldol reactions were efficiently performed in continuo, with high yield (99%), anti-stereoselectivity, and enantioselectivity (up to 97% ee). Moreover, using two different DES mixtures, the diastereoselectivity of the process could be tuned, thereby leading to the formation, under different experimental conditions, to both the syn- and the anti-isomer with very high enantioselectivity. The excess of cyclohexanone was recovered and reused, and the reaction could be run and the product isolated without the use of any organic solvent by a proper choice of DES components. The dramatic influence of the reaction media on the reaction rate and stereoselectivity of the process suggests that the intimate architecture of DESs deeply influences the reactivity of different species involved in the catalytic cycle. PMID:28144332

  19. 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

  20. Controlling condensation and frost growth with chemical micropatterns

    DOE PAGES

    Boreyko, Jonathan B.; Hansen, Ryan R.; Murphy, Kevin R.; ...

    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

  1. Controlling condensation and frost growth with chemical micropatterns

    SciTech Connect

    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 of 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.

  2. Advances in shell side condensation for refrigerants

    NASA Astrophysics Data System (ADS)

    Webb, Ralph L.

    The design of shell and tube condensers used in air conditioning and refrigeration applications is discussed. The geometry of interest involves condensation on the shell side of a horizontal tube bundle. Enhanced heat transfer geometries are typically used for condensation on the shell side. The heat transfer is removed by water on the tube side, which typically have tube side enhancement. Single tube and row effect condensation data are presented. Thermal design methods for sizing of the condenser are outlined.

  3. Bose-Einstein condensate strings

    NASA Astrophysics Data System (ADS)

    Harko, Tiberiu; Lake, Matthew J.

    2015-02-01

    We consider the possible existence of gravitationally bound general relativistic strings consisting of Bose-Einstein condensate (BEC) matter which is described, in the Newtonian limit, by the zero temperature time-dependent nonlinear Schrödinger equation (the Gross-Pitaevskii equation), with repulsive interparticle interactions. In the Madelung representation of the wave function, the quantum dynamics of the condensate can be formulated in terms of the classical continuity equation and the hydrodynamic Euler equations. In the case of a condensate with quartic nonlinearity, the condensates can be described as a gas with two pressure terms, the interaction pressure, which is proportional to the square of the matter density, and the quantum pressure, which is without any classical analogue, though, when the number of particles in the system is high enough, the latter may be neglected. Assuming cylindrical symmetry, we analyze the physical properties of the BEC strings in both the interaction pressure and quantum pressure dominated limits, by numerically integrating the gravitational field equations. In this way we obtain a large class of stable stringlike astrophysical objects, whose basic parameters (mass density and radius) depend sensitively on the mass and scattering length of the condensate particle, as well as on the quantum pressure of the Bose-Einstein gas.

  4. 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.

  5. Self-condensation of activated dinucleotides on polynucleotide templates with alternating sequences

    NASA Technical Reports Server (NTRS)

    Lohrmann, R.; Orgel, L. E.

    1979-01-01

    Substantial quantities of the alternating polymers poly(U-G) and poly(C-A) have been prepared and used as templates for the self-condensation of ImpApC, ImpCpA, ImpGpU and ImpUpG. It is found that the condensation of ImpGpu and ImpUpG on poly(C-A) is efficient, the condensation of ImpCpA on poly(U-G) is moderately efficient, while the condensation of ImpApC on poly(U-C) proceeds poorly. In many cases, the product is predominantly 3'-5'-linked. These reactions demonstrate unequivocally, for the first time, that template-directed reactions occur in double-helical structures. Furthermore, they describe for the first time a pair of reactions in which each of two complementary polymers facilitates the synthesis of the other. The prebiotic significance of these findings is discussed.

  6. 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...

  7. Fate of catechols in coal gasification condensate waters

    SciTech Connect

    Uhrich, K.E.

    1986-02-01

    Even after the wastewater has been subjected to rigorous cleaning, many chemicals still remain. In order to remove these compounds, they must be identified. Catechol is a compound which appears in the condensate water and, because its concentration changes, its fate is somewhat uncertain. In recent experiments modeling the condensate water conditions, catechol solutions were aerated in the presence of ammonia. Upon acidification of the solutions, a polymer precipitates. This polymer was compared to the black compound isolated from the condensate water by spectral and elemental analyses. The structures of the two polymers were reasonably similar. The kinetics of oxidation, as determined by the uptake of oxygen, indicates that the reaction was first order in catechol and oxygen. The rate was significantly enhanced by an increase in pH. Assuming that catechol is the only subunit of the polymers isolated from the different condensate waters, calculations would indicate that the initial catechol concentration varies from 440 to 1700 ppM. An attempt is being made to account for all of the carbon that appears in the water from the gasification process. Presently, only 60% to 70% of the carbon-containing products have been identified. Part of the remaining total organic carbon can be accounted for by the catechol polymer. Studying the fate of catechol in the coal gasification condensate water will help to develop an environmentally and financially feasible treatment of the wastewater. 4 refs.

  8. 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.

  9. 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).

  10. 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).

  11. Neuroamine condensations in human subjects.

    PubMed

    Collins, M A

    1980-01-01

    Non-enzymatic products of neuroamines and endogenous carbonyl compounds are apparent "normal" products in human metabolism, and their levels become increased during pathological conditions. DA condensation products--salsolinol, its O-methylated derivative, and methylated derivatives of 1-carboxyl-THP--are found normally in human urine, and the last TIQ is in human brain. Potential beta-carboline condensation products also occur in (aging) human lens tissue. Chronic drinking in alcoholics causes significant increases in urinary salsolinol and O-methyl-salsolinol, presumably due to the increased AcH which is made available. L-DOPA therapy (in Parkinson's disease) elevates urinary and tissue levels of the carboxylated THP derivatives, as well as of salsolinol and THP itself; hyperphenylalaninemia during PKU also increases tissue levels of a DA/phenylpyruvate-derived TIQ and an imine condensate of phenylethylamine and vitamin B6. These unusual products may interfere with neural dynamic processes, and produce cytotoxic metabolites.

  12. 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.

  13. 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.

  14. Scrutinizing the pion condensed phase

    NASA Astrophysics Data System (ADS)

    Carignano, Stefano; Lepori, Luca; Mammarella, Andrea; Mannarelli, Massimo; Pagliaroli, Giulia

    2017-02-01

    When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low-density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to that of quantum magnets. By integrating out the "radial" fluctuations we obtain a soft Lagrangian in terms of the Nambu-Goldstone bosons arising from the breaking of the pion number symmetry. Finally, we test the robustness of the second-order transition between the normal and the pion condensed phase when next-to-leading-order chiral corrections are included. We determine the range of parameters for turning the second-order phase transition into a first-order one, finding that the currently accepted values of these corrections are unlikely to change the order of the phase transition.

  15. 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

  16. 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.

  17. Condensed Matter Physics - Biology Resonance

    NASA Astrophysics Data System (ADS)

    Baskaran, G.

    The field of condensed matter physics had its genesis this century and it has had a remarkable evolution. A closer look at its growth reveals a hidden aim in the collective consciousness of the field - a part of the development this century is a kind of warm up exercise to understand the nature of living condensed matter, namely the field of biology, by a growing new breed of scientists in the coming century. Through some examples the vitality of this interaction will be pointed out.

  18. Tripol condensate polishing - operational experience

    SciTech Connect

    Swainsbury, D.

    1995-01-01

    This paper gives a brief outline of the Mission Energy Management Australia Company who operate and maintain the Loy Yang B Power Station in the Latrobe Valley, Victoria, Australia. Details of the plant configuration, the water/steam circuit and cycle chemistry are discussed. The arrangement of the TRIPOL Condensate Polishing Plant and it`s operational modes are examined. Results of the first twelve months operation of the TRIPOL plant are detailed. Levels of crud removal during early commissioning phases employing the pre-filter are presented. Typical parameters achieved during a simulated condenser leak and an operational run beyond the ammonia break point are also documented.

  19. Andreev Reflection in Bosonic Condensates

    SciTech Connect

    Zapata, I.; Sols, F.

    2009-05-08

    We study the bosonic analog of Andreev reflection at a normal-superfluid interface where the superfluid is a boson condensate. We model the normal region as a zone where nonlinear effects can be neglected. Against the background of a decaying condensate, we identify a novel contribution to the current of reflected atoms. The group velocity of this Andreev reflected component differs from that of the normally reflected one. For a three-dimensional planar or two-dimensional linear interface Andreev reflection is neither specular nor conjugate.

  20. [A novel and practical synthesis of (+)-biotin via Fukuyama coupling reaction].

    PubMed

    Shimizu, Toshiaki

    2003-02-01

    (+)-Biotin (1) was synthesized from readily accessible L-aspartic acid (4). The contiguous asymmetric centers at C-3a and C-6a were formed through a diastereoselective aldol reaction of N-Cbz-3-amino-4-butanolide 5 to provide trans-disubstituted lactone 6 with high stereoselectivity (trans/cis = 12:1). The imidazolidin-2-one moiety of 1 was constructed by a stereoselective Hofmann rearrangement of beta-substituted asparagine derivative 7 to provide cyclic urea 8. This reaction proceeds with complete retention of stereochemistry. Removal of the protective groups of 8 and subsequent dibenzylation and thionation provided thiolactone 2. The installation of the C-4 side chain of 1 was performed through a Pd/C-catalyzed coupling reaction of 2 with ethoxycarbonylbutylzinc iodide 14a (Fukuyama coupling reaction), which permitted the synthesis of 1 from 2 under industrially applicable mild conditions in three steps.

  1. Visualization of early chromosome condensation

    PubMed Central

    Kireeva, Natashe; Lakonishok, Margot; Kireev, Igor; Hirano, Tatsuya; Belmont, Andrew S.

    2004-01-01

    Current models of mitotic chromosome structure are based largely on the examination of maximally condensed metaphase chromosomes. Here, we test these models by correlating the distribution of two scaffold components with the appearance of prophase chromosome folding intermediates. We confirm an axial distribution of topoisomerase IIα and the condensin subunit, structural maintenance of chromosomes 2 (SMC2), in unextracted metaphase chromosomes, with SMC2 localizing to a 150–200-nm-diameter central core. In contrast to predictions of radial loop/scaffold models, this axial distribution does not appear until late prophase, after formation of uniformly condensed middle prophase chromosomes. Instead, SMC2 associates throughout early and middle prophase chromatids, frequently forming foci over the chromosome exterior. Early prophase condensation occurs through folding of large-scale chromatin fibers into condensed masses. These resolve into linear, 200–300-nm-diameter middle prophase chromatids that double in diameter by late prophase. We propose a unified model of chromosome structure in which hierarchical levels of chromatin folding are stabilized late in mitosis by an axial “glue.” PMID:15353545

  2. Magnetofermionic condensate in two dimensions

    PubMed Central

    Kulik, L. V.; Zhuravlev, A. S.; Dickmann, S.; Gorbunov, A. V.; Timofeev, V. B.; Kukushkin, I. V.; Schmult, S.

    2016-01-01

    Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibrium ensemble of long-lived triplet magnetoexcitons exhibits both a drastic reduction in the viscosity and a steep enhancement in the response to the external electromagnetic field. The observed effects are related to formation of a super-absorbing state interacting coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level form a super-emitting state. The effects are explicable from the viewpoint of a coherent condensate phase in a non-equilibrium system of two-dimensional fermions with a fully quantized energy spectrum. The condensation occurs in the space of vectors of magnetic translations, a property providing a completely new landscape for future physical investigations. PMID:27848969

  3. Linker DNA destabilizes condensed chromatin.

    PubMed

    Green, G R; Ferlita, R R; Walkenhorst, W F; Poccia, D L

    2001-01-01

    The contribution of the linker region to maintenance of condensed chromatin was examined in two model systems, namely sea urchin sperm nuclei and chicken red blood cell nuclei. Linkerless nuclei, prepared by extensive digestion with micrococcal nuclease, were compared with Native nuclei using several assays, including microscopic appearance, nuclear turbidity, salt stability, and trypsin resistance. Chromatin in the Linkerless nuclei was highly condensed, resembling pyknotic chromatin in apoptotic cells. Linkerless nuclei were more stable in low ionic strength buffers and more resistant to trypsin than Native nuclei. Analysis of histones from the trypsinized nuclei by polyacrylamide gel electrophoresis showed that specific histone H1, H2B, and H3 tail regions stabilized linker DNA in condensed nuclei. Thermal denaturation of soluble chromatin preparations from differentially trypsinized sperm nuclei demonstrated that the N-terminal regions of histones Sp H1, Sp H2B, and H3 bind tightly to linker DNA, causing it to denature at a high temperature. We conclude that linker DNA exerts a disruptive force on condensed chromatin structure which is counteracted by binding of specific histone tail regions to the linker DNA. The inherent instability of the linker region may be significant in all eukaryotic chromatins and may promote gene activation in living cells.

  4. Magnetofermionic condensate in two dimensions.

    PubMed

    Kulik, L V; Zhuravlev, A S; Dickmann, S; Gorbunov, A V; Timofeev, V B; Kukushkin, I V; Schmult, S

    2016-11-16

    Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibrium ensemble of long-lived triplet magnetoexcitons exhibits both a drastic reduction in the viscosity and a steep enhancement in the response to the external electromagnetic field. The observed effects are related to formation of a super-absorbing state interacting coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level form a super-emitting state. The effects are explicable from the viewpoint of a coherent condensate phase in a non-equilibrium system of two-dimensional fermions with a fully quantized energy spectrum. The condensation occurs in the space of vectors of magnetic translations, a property providing a completely new landscape for future physical investigations.

  5. 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…

  6. Magnetofermionic condensate in two dimensions

    NASA Astrophysics Data System (ADS)

    Kulik, L. V.; Zhuravlev, A. S.; Dickmann, S.; Gorbunov, A. V.; Timofeev, V. B.; Kukushkin, I. V.; Schmult, S.

    2016-11-01

    Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibrium ensemble of long-lived triplet magnetoexcitons exhibits both a drastic reduction in the viscosity and a steep enhancement in the response to the external electromagnetic field. The observed effects are related to formation of a super-absorbing state interacting coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level form a super-emitting state. The effects are explicable from the viewpoint of a coherent condensate phase in a non-equilibrium system of two-dimensional fermions with a fully quantized energy spectrum. The condensation occurs in the space of vectors of magnetic translations, a property providing a completely new landscape for future physical investigations.

  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. 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.

  9. 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.

  10. 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

  11. 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.

  12. Selective synthesis of alpha,beta-unsaturated ketones by dibutyltin dimethoxide-catalyzed condensation of aldehydes with alkenyl trichloroacetates.

    PubMed

    Yanagisawa, Akira; Goudu, Riku; Arai, Takayoshi

    2004-11-11

    Various alpha,beta-unsaturated ketones were stereoselectively synthesized in high yields up to 94% by a condensation reaction between alkenyl trichloroacetates and aldehydes using dibutyltin dimethoxide as a catalyst in the presence of methanol. This process is superior to the classical Claisen-Schmidt condensation with respect to mildness of the base catalyst and product selectivity.

  13. Internally drained condenser for spacecraft thermal management

    NASA Technical Reports Server (NTRS)

    Valenzuela, Javier A.; Drew, Brian C.

    1989-01-01

    This paper presents the results obtained to date in a program to develop a high heat flux condenser for use in two-phase spacecraft thermal management loops. The objective is to obtain a several fold increase in condensation heat transfer coefficient over those which can be achieved with shear-controlled or capillary-wick condensers. The internally drained condenser relies on shaped fins to develop a capillary pressure gradient over the surface of the fins and drive the condensate toward narrow drainage grooves separating the fins. The condensate then flows through a drainage network embedded in the condenser walls. Heat transfer coefficients of up to 8 W/sq cm C were measured in steam, providing a heat transfer enhancement ratio greater than a factor of 8. In the paper the proof-of-concept experiments are described and simplified models to predict the performance of the internally drained condenser are presented.

  14. 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.

  15. 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.

  16. Exciton-polaritons condensate in a microwire

    NASA Astrophysics Data System (ADS)

    Kamoun, O.; Jaziri, S.

    2013-12-01

    Recently, polariton condensation has been claimed in microwires. Numerical solutions of the time-dependent Gross-Pitaevskii equation that describes the behavior of the condensate in a trap and exciton-polariton interaction, have been obtained. In this work we study theoretically exciton-polariton one dimensional condensation in several quantized states.

  17. Automatic Reaction Pathway Search via Combined Molecular Dynamics and Coordinate Driving Method.

    PubMed

    Yang, Manyi; Zou, Jingxiang; Wang, Guoqiang; Li, Shuhua

    2017-02-16

    We proposed and implemented a combined molecular dynamics and coordinate driving (MD/CD) method for automatically searching multistep reaction pathways of chemical reactions. In this approach, the molecular dynamic (MD) method at the molecular mechanics (MM) or semiempirical quantum mechanical (QM) level is employed to explore the conformational space of the minimum structures, and the modified coordinate driving (CD) method is used to build reaction pathways for representative conformers. The MD/CD method is first applied to two model reactions (the Claisen rearrangement and the intermolecular aldol reaction). By comparing the obtained results with those of the existing methods, we found that the MD/CD method has a comparable performance in searching low-energy reaction pathways. Then, the MD/CD method is further applied to investigate two reactions: the electrocyclic reaction of benzocyclobutene-7-carboxaldehyde and the intramolecular Diels-Alder reaction of ketothioester with 11 effectively rotatable single bonds. For the first reaction, our results can correctly account for its torquoselectivity. For the second one, our method predicts eight reaction channels, leading to eight different stereo- and regioselective products. The MD/CD method is expected to become an efficient and cost-effective theoretical tool for automatically searching low-energy reaction pathways for relatively complex chemical reactions.

  18. 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

  19. Polymer Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Castellanos, E.; Chacón-Acosta, G.

    2013-05-01

    In this work we analyze a non-interacting one-dimensional polymer Bose-Einstein condensate in a harmonic trap within the semiclassical approximation. We use an effective Hamiltonian coming from the polymer quantization that arises in loop quantum gravity. We calculate the number of particles in order to obtain the critical temperature. The Bose-Einstein functions are replaced by series, whose high order terms are related to powers of the polymer length. It is shown that the condensation temperature presents a shift respect to the standard case, for small values of the polymer scale. In typical experimental conditions, it is possible to establish a bound for λ2 up to ≲10-16 m2. To improve this bound we should decrease the frequency of the trap and also decrease the number of particles.

  20. Reactivity of Free Malondialdehyde during In Vitro Simulated Gastrointestinal Digestion.

    PubMed

    Vandemoortele, Angelique; Babat, Pinar; Yakubu, Mariam; De Meulenaer, Bruno

    2017-03-15

    An aqueous buffer, a saturated glycerol triheptanoate oil, and a Tween 20 stabilized fully hydrogenated coconut oil-in-water emulsion, all spiked with malondialdehyde, were subjected to in vitro digestion. A dynamic equilibrium between malondialdehyde, its aldol self-condensation products, and its hydrolytic cleavage products was observed. This equilibrium depended upon the kind of sample and the temperature at which these samples were preincubated during 24 h. The presence of oil during gastric digestion protected the aldol self-condensation and cleavage products from conversion to malondialdehyde, which occurred in the aqueous acidic gastric chyme. In parallel, the presence of oil enhanced the reactivity of malondialdehyde throughout the gastrointestinal digestion process. Malondialdehyde recoveries after digestion varied between 42 and 90%, depending upon the model system studied, with the aldol self-condensation as the main reaction pathway. In conclusion, this study revealed that malondialdehyde is a very reactive molecule whose reactivity does not stop at the point of ingestion.

  1. 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.

  2. Efficient and economical access to substituted benzothiazoles: copper-catalyzed coupling of 2-haloanilides with metal sulfides and subsequent condensation.

    PubMed

    Ma, Dawei; Xie, Siwei; Xue, Peng; Zhang, Xiaojing; Dong, Jinhua; Jiang, Yongwen

    2009-01-01

    Don't tell azole: The first metal-catalyzed direct coupling of metal sulfides with aryl halides and subsequent intramolecular condensation provided substituted benzothiazoles (see scheme). A wide range of functional groups are tolerated under the reaction conditions.

  3. 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.

  4. 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.

  5. Condensation on Slippery Asymmetric Bumps

    NASA Astrophysics Data System (ADS)

    Park, Kyoo-Chul; Kim, Philseok; Aizenberg, Joanna

    2016-11-01

    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.

  6. New technology in condensate polishing. Final report

    SciTech Connect

    Kunin, R.; Salem, E.; Libutti, B.

    1992-08-01

    Sulfonic acid ion exchange resins. when carried into a boiler or steam generator, thermally decompose releasing large amounts of corrosive, sulfates. Replacement of the sulfonic acid resin with a carboxylic acid resin would eliminate this source of contamination. The sulfonic acid resin is a strong acid: the carboxylic acid resin is a weak acid. The carboxylic acid resin alone is not capable of splitting salts which limits its use to mixed resin beds or to its use in single or individual beds with feeds of high alkalinity or high pH values. Laboratory, pilot plant and full scale plant tests compared the two resins in precoat filters. When the resins in mixed beds were in the acid form, the weakly acid resin was almost as effective in removing sodium ion as the strongly acid resin. In the ammonium form. the weakly acid resin was generally more effective in removing sodium than the strongly acid resin. Condensate polishing reduced the sodium ion to a few parts per billion (ppB). Complete resin separation before regeneration is more important for the weakly acid resin than for the strongly acid resin. Another development found that the hydrazine reaction with oxygen could be catalyzed by powdered activated carbon combined with microfibers on a Powdex substrate. The carbon should be thoroughly washed to reduce its residual sodium content. In plant tests, the carbon reduced the oxygen concentration in condensate about 50% during startup. In preliminary tests believed to be typical, carbon lowered the oxygen concentration below 10 ppB in about 6 hours compared to 18 hours without the carbon. Oxygen is also reduced during normal operation.

  7. 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.

  8. Mitotic chromatin condensation in vitro using somatic cell extracts and nuclei with variable levels of endogenous topoisomerase II

    PubMed Central

    1990-01-01

    We report the development of a new method for producing mitotic extracts from tissue culture cells. These extracts reproducibly promote the condensation of chromatin in vitro when incubated with purified interphase nuclei. This condensation reaction is not species specific, since nuclei from chicken, human, and hamster cell lines all undergo chromatin condensation upon incubation with the extract. We have used this extract to investigate the role of DNA topoisomerase II (topo II) in the chromosome condensation process. Chromatin condensation does not require the presence of soluble topo II in the mitotic extract. However, the extent of formation of discrete chromosome-like structures correlates with the level of endogenous topo II present in the interphase nuclei. Our results further suggest that chromatin condensation in this extract may involve two processes: chromatin compaction and resolution into discrete chromosomes. PMID:2176652

  9. Total synthesis of the anti-inflammatory and pro-resolving lipid mediator MaR1n-3 DPA utilizing an sp(3) -sp(3) Negishi cross-coupling reaction.

    PubMed

    Tungen, Jørn Eivind; Aursnes, Marius; Dalli, Jesmond; Arnardottir, Hildur; Serhan, Charles Nicholas; Hansen, Trond Vidar

    2014-11-03

    The first total synthesis of the lipid mediator MaR1n-3 DPA (5) has been achieved in 12 % overall yield over 11 steps. The stereoselective preparation of 5 was based on a Pd-catalyzed sp(3) -sp(3) Negishi cross-coupling reaction and a stereocontrolled Evans-Nagao acetate aldol reaction. LC-MS/MS results with synthetic material matched the biologically produced 5. This novel lipid mediator displayed potent pro-resolving properties stimulating macrophage efferocytosis of apoptotic neutrophils.

  10. 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.

  11. 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.

  12. Condensation on slippery asymmetric bumps.

    PubMed

    Park, Kyoo-Chul; Kim, Philseok; Grinthal, Alison; He, Neil; Fox, David; Weaver, James C; Aizenberg, Joanna

    2016-03-03

    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

  13. 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

  14. Marine Steam Condenser Design Optimization.

    DTIC Science & Technology

    1983-12-01

    Rerf . 61. !kS 2XLI: Those parametars which the opti heztion proqran ms--faitted to change in order to improre’the esign. Pesin variablis appear oely on...subroutine SEC& LC is called. 5. jZ.~ This subroutine determines all the parameters of each of the sectors in the condenser by row. The first...force the pressure losses to converge to a single value. Once steam flow to the sectors has been adjusted, the sector and row analysis in SEC& LC is

  15. Direct condensation by humid air

    NASA Astrophysics Data System (ADS)

    Schwab, S.; Schiebelsberger, B.

    1980-12-01

    The practicability of direct condensation with humid air (DKFL) for waste heat removal from thermal power plants was investigated with regard to technical, economical and environmental aspects. The adjustment of a uniform trickling-water film was examined. A vertical test tube was erected to study the phenomenon of a trickling-water film. A pilot plant with a vertical tube-bundle was installed to evaluate the main process parameters. The applicability of the cooling system is judged. A theoretical model was derived for the design of a DKFL apparatus. A vertical geometry for the test tube has essential operational and economical advantages in comparison with a horizontal one.

  16. 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.

  17. 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.

  18. 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.

  19. DNA condensation in one dimension

    NASA Astrophysics Data System (ADS)

    Pardatscher, Günther; Bracha, Dan; Daube, Shirley S.; Vonshak, Ohad; Simmel, Friedrich C.; Bar-Ziv, Roy H.

    2016-12-01

    DNA can be programmed to assemble into a variety of shapes and patterns on the nanoscale and can act as a template for hybrid nanostructures such as conducting wires, protein arrays and field-effect transistors. Current DNA nanostructures are typically in the sub-micrometre range, limited by the sequence space and length of the assembled strands. Here we show that on a patterned biochip, DNA chains collapse into one-dimensional (1D) fibres that are 20 nm wide and around 70 µm long, each comprising approximately 35 co-aligned chains at its cross-section. Electron beam writing on a photocleavable monolayer was used to immobilize and pattern the DNA molecules, which condense into 1D bundles in the presence of spermidine. DNA condensation can propagate and split at junctions, cross gaps and create domain walls between counterpropagating fronts. This system is inherently adept at solving probabilistic problems and was used to find the possible paths through a maze and to evaluate stochastic switching circuits. This technique could be used to propagate biological or ionic signals in combination with sequence-specific DNA nanotechnology or for gene expression in cell-free DNA compartments.

  20. 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)

  1. Ultra-low threshold polariton condensation

    NASA Astrophysics Data System (ADS)

    Steger, Mark; Fluegel, Brian; Alberi, Kirstin; Snoke, David W.; Pfeiffer, Loren N.; West, Ken; Mascarenhas, Angelo

    2017-03-01

    We demonstrate condensation of microcavity polaritons with a very sharp threshold occuring at two orders of magnitude lower pump intensity than previous demonstrations of condensation. The long cavity-lifetime and trapping and pumping geometries are crucial to the realization of this low threshold. Polariton condensation, or "polariton lasing" has long been proposed as a promising source of coherent light at lower threshold than traditional lasing, and these results suggest methods to bring this threshold even lower.

  2. 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.

  3. Ultra-low threshold polariton condensation.

    PubMed

    Steger, Mark; Fluegel, Brian; Alberi, Kirstin; Snoke, David W; Pfeiffer, Loren N; West, Ken; Mascarenhas, Angelo

    2017-03-15

    We demonstrate the condensation of microcavity polaritons with a very sharp threshold occurring at a two orders of magnitude pump intensity lower than previous demonstrations of condensation. The long cavity lifetime and trapping and pumping geometries are crucial to the realization of this low threshold. Polariton condensation, or "polariton lasing" has long been proposed as a promising source of coherent light at a lower threshold than traditional lasing, and these results indicate some considerations for optimizing designs for lower thresholds.

  4. Stereoselective synthesis of (E)-4-alkylidenecyclopent-2-en-1-ones by a tandem ring closure-Michael addition-elimination.

    PubMed

    Ballini, R; Bosica, G; Fiorini, D; Gil, M V; Petrini, M

    2001-05-03

    Reaction of (Z)-1,4-diketones with various functionalized nitroalkanes in the presence of DBU gives 4-alkylidenecyclopent-2-en-1-ones with E selectivity. A cyclopentadienone intermediate is probably formed by intramolecular aldol condensation, and this reacts with a nitroalkane giving a Michael addition-elimination.

  5. Highly efficient C-C bond-forming reactions in aqueous media catalyzed by monomeric vanadate species in an apatite framework.

    PubMed

    Hara, Takayoshi; Kanai, Satoko; Mori, Kohsuke; Mizugaki, Tomoo; Ebitani, Kohki; Jitsukawa, Koichiro; Kaneda, Kiyotomi

    2006-09-15

    A calcium vanadate apatite (VAp), in which PO4(3-) of hydroxyapatite (HAP), Ca10(PO4)6(OH)2, is completely substituted by VO4(3-) in the apatite framework, was synthesized. Physicochemical analysis of the VAp reveals the presence of isolated VO4 tetrahedron units with a pentavalent oxidation state. The VAp acts as a high-performance heterogeneous base catalyst for various carbon-carbon bond-forming reactions such as Michael and aldol reactions in aqueous media and the H-D exchange reactions using deuterium oxide. For example, a 200-mmol-scale Michael reaction under triphasic conditions proceeded rapidly, with an extremely high turnover number of up to 260 400 and an excellent turnover frequency of 48 s(-1). No vanadium leaching was detected during the above reactions, and the catalyst was readily recycled with no loss of activity.

  6. FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS AND CARBONACEOUS SOLIDS IN GAS-PHASE CONDENSATION EXPERIMENTS

    SciTech Connect

    Jaeger, C.; Huisken, F.; Henning, Th.; Mutschke, H.; Jansa, I. Llamas

    2009-05-01

    Carbonaceous grains represent a major component of cosmic dust. In order to understand their formation pathways, they have been prepared in the laboratory by gas-phase condensation reactions such as laser pyrolysis and laser ablation. Our studies demonstrate that the temperature in the condensation zone determines the formation pathway of carbonaceous particles. At temperatures lower than 1700 K, the condensation by-products are mainly polycyclic aromatic hydrocarbons (PAHs) that are also the precursors or building blocks for the condensing soot grains. The low-temperature condensates contain PAH mixtures that are mainly composed of volatile three to five ring systems. At condensation temperatures higher than 3500 K, fullerene-like carbon grains and fullerene compounds are formed. Fullerene fragments or complete fullerenes equip the nucleating particles. Fullerenes can be identified as soluble components. Consequently, condensation products in cool and hot astrophysical environments such as cool and hot asymptotic giant branch stars or Wolf-Rayet stars should be different and should have distinct spectral properties.

  7. 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.

  8. Evaporative condensing minimizes system power requirements

    SciTech Connect

    Knebel, D.E.

    1997-04-01

    Evaporative condensing is a heat-rejection technology widely applied with industrial refrigeration. When employed with HVAC systems it can reduce electrical energy and demand consumption of an HVAC system by 20 to 40%, depending on location, compared to air-cooled condensing. Evaporative condensing allows direct-expansion (DX) systems to achieve energy and demand consumption comparable to the most efficient chilled water central plant systems. As the industry focuses its attention on solving the problems of energy conservation, demand reduction, and global warming, high-efficiency air conditioning systems utilizing evaporative condensing provide a reliable and cost-effective solution today. This article addresses the advantages of evaporative condensing over air-cooled and water-cooled condensing in DX packaged systems as well as chiller/cooling tower systems. A review of condensing methods and standard system operating characteristics will be used as examples to illustrate the thermodynamic benefits of evaporative condensing. Requirements for successful operation of evaporative condensers will be discussed.

  9. Vapor condensation on a turbulent liquid interface

    NASA Technical Reports Server (NTRS)

    Helmick, M. R.; Khoo, B. C.; Sonin, A. A.

    1987-01-01

    An experimental investigation which seeks the fundamental relationship between the interfacial condensation rate and the parameters which control it when the liquid side is turbulent is discussed. The scaling laws for free-surface condensation are discussed for this case. It is argued that the condensation of cryogenic liquids can, in principle, be simulated in experiments using steam and water. Data are presented for the condensation rate in terms of the dimensionless scaling parameters which involve the fluid properties and the liquid-side turbulence velocity and length scales.

  10. 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.

  11. Combined boiler feed and condensate pump

    SciTech Connect

    Paul Cooper, Titusville, N.J.

    1993-06-01

    A pump for drawing the condensate from a condenser and feeding it to a steam boiler is described, the combination comprising: an elongate casing adapted to be connected in a pipeline having an inlet for receiving the condensate from a steam condenser and an outlet for feeding the condensate to a steam boiler; a pump shaft mounted in said casing rotating in a pair of bearings spaced along said shaft and fixed in said casing; an electric motor mounted in said casing connected to one end of said shaft for driving it; control means for operating said electric motor; an inducer pump mounted at the other end of said shaft, driven by said shaft; a multiple stage centrifugal feed pump located in said casing driven by said shaft and receiving condensate from the inducer pump, pumping said condensate to a higher pressure suitable for feeding a steam boiler and delivering said condensate to the outlet of said pump, the multiple stage centrifugal feed pump being located adjacent said inducer pump; and said inducer pump being of the type to produce sufficient positive pressure for properly feeding condensate to said feed pump.

  12. Freeze Enhanced Halate Halide Reactions

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Weaver, K.; Broderick, A.

    2014-12-01

    Relatively little is known about halate ion species (XO3-; X = I, Br, Cl) in atmospheric condensed phases. It was initial thought that iodate was a terminal stable species upon iodide oxidation. However, it is becoming increasingly recognized that reactions involving iodate can lead to reactive iodine, and this chemistry is accelerated under acidic conditions. The environmental concentrations and chemistry of bromate and chlorate are largely unexplored in environmental ices. We present results from a series of aqueous phase halate ion reactions with halides under acidic conditions, showing that the kinetics are strongly enhanced upon freezing. The products of these reactions are reactive halogens, which have important implications to marine boundary layer chemistry.

  13. 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...

  14. 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.

  15. Unraveling high precision stereocontrol in a triple cascade organocatalytic reaction.

    PubMed

    Shinisha, C B; Sunoj, Raghavan B

    2008-11-07

    The mechanism and stereoselectivity in an organocatalyzed triple cascade reaction between an aldehyde, electron deficient olefin and an alpha,beta-unsaturated aldehyde are investigated for the first time using density functional theory. The factors responsible for high levels of observed stereoselectivity (Enders et al., Nature, 2006, 441, 861) towards the generation of cyclohexene carbaldehyde with four contiguous stereocentres are unravelled. The triple cascade reaction, comprising a Michael, Michael and aldol sequence as the key elementary reactions, is studied by identifying the corresponding transition states for the stereoselective C-C bond-formation. In the first Michael addition step between the enamine (derived from the chiral catalyst and propanal) and nitrostyrene, energetically the most preferred mode of addition is found to be between the si-face of (E)-anti-enamine on the si-face of nitrostyrene. The addition of the si-face of the nitroalkane anion on the re-face of the iminium ion (formed between the enal and the catalyst) is the lowest energy pathway for the second Michael addition step. The high level of asymmetric induction is rationalized with the help of relative activation barriers associated with the competitive diastereomeric pathways. Interesting weak interactions, along with the steric effects offered by the bulky alpha-substituent on the pyrrolidine ring, are identified as critical to the stereoselectivity in this triple cascade reaction. The predicted stereoselectivities using computed energetics are found to be in perfect harmony with the experimental stereoselectivities.

  16. Demonstration of Nautilus Centripetal Capillary Condenser Technology

    NASA Technical Reports Server (NTRS)

    Wheeler, RIchard; Tang, Linh; Wambolt, Spencer; Golliher, Eric; Agui, Juan

    2016-01-01

    This paper describes the results of a proof of concept effort for development of a Nautilus Centripetal Capillary Condenser (NCCC or NC3) used for microgravity compatible water recovery from moist air with integral passive phase separation. Removal of liquid condensate from the air stream exiting a condenser is readily performed here on Earth. In order to perform this function in space however, without gravity or mechanical action, other tactics including utilization of inertial, drag and capillary forces are required. Within the NC3, liquid water forms via condensation on cold condenser surfaces as humid air passes along multiple spiral channels, each in its own plane, all together forming a stacked plate assembly. Non-mechanical inertial forces are employed to transfer condensate, as it forms, via centripetal action to the outer perimeter of each channel. A V-shaped groove, constructed on this outer edge of the spiral channel, increases local capillary forces thereby retaining the liquid. Air drag then pulls the liquid along to a collection region near the center of the device. Dry air produced by each parallel spiral channel is combined in a common orthogonal, out-of-plane conduit passing down the axial center of the stacked device. Similarly, the parallel condensate streams are combined and removed from the condenser/separator through yet another out-of-plane axial conduit. NC3 is an integration of conventional finned condenser operation, combined with static phase separation and capillary transport phenomena. A Mars' transit mission would be a logical application for this technology where gravity is absent and the use of vibrating, energy-intensive, motor-driven centrifugal separators is undesired. Here a vapor stream from either the Heat Melt Compactor or the Carbon dioxide Reduction Assembly, for example, would be dried to a dew point of 10 deg using a passive NC3 condenser/separator with the precious water condensate recycled to the water bus.

  17. An Experimental Study of Filmwise Condensation on Horizontal Enhanced Condenser Tubing.

    DTIC Science & Technology

    1979-12-01

    with a 51 mm thick sheet of Johns - Manville Aerotube insulation. 22 D. CONDENSATE AND FEEDWATER SYSTEMS The condensate and feedwater systems are shown...desuperheater. The condensate and feedwater lines are insulated with 25.4 mm thick Johns - Manville Aerotube insulation. E. COOLING WATER SYSTEM The cooling

  18. Counterion condensation on heparin oligomers.

    PubMed

    Minsky, Burcu Baykal; Atmuri, Anand; Kaltashov, Igor A; Dubin, Paul L

    2013-04-08

    The electropherogram of native heparin shows a broad distribution of mobilities μ, which truncates abruptly at a notably high μ = 4.7 × 10(-4) cm(2) V(-1) s(-1). This highly skewed mobility distribution is also found for the 20-saccharide chain, which shows from mass spectrometry a more uniform (symmetrical) with respect to sulfation level. Since a partially degraded heparin exhibits oligomer peaks with μ> 5 × 10(-4) cm(2) V(-1) s(-1) (appearing to escape the limitation of the mobility value for native heparin), we examined the electrophoretic behavior of chain-length monodisperse heparin oligomers. Their mobilities varied inversely with the logarithm of the contour length, L, for L from 3 to 10 nm and reached an asymptotic limit for L > 20 nm. The generality of this effect was indicated by similar behavior for oligomers of poly(styrene sulfonate). A recent theory of polyelectrolyte end effects (Manning, G. S. Macromolecules2008, 41, 6217-6227), in which chain termini exhibit reduced counterion condensation was found to quantitatively account for these results. A qualitative explanation for the anomalously high value of μ of native heparin, 10-20% higher than those seen for synthetic polyelectrolytes of higher linear charge density, is suggested on the basis of similar junction effects (Manning, G. S. Macromolecules2008, 41, 6217-6227), which reduce counterion condensation at the interfaces of regions of high and low sulfation. We suggest that these effects should be considered in models for the biofunctionality of the regulated high and low sulfation (NS/NA) domains of heparan sulfate.

  19. 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

  20. 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).

  1. 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

  2. Photochemical Processes in the Condensed Haze of Titan's Atmosphere

    NASA Astrophysics Data System (ADS)

    Gudipati, M. S.; Couturier, I.; Jacovi, R.; Lignell, A.

    2013-12-01

    Recently we have shown that condensed-phase photochemical processes continue to occur at altitudes where gas-phase photochemistry would not be significant due to extinction of higher energy short-wavelength photons and availability of only longer wavelength low-energy photons (>250 nm). Accretion of Titan's molecules into weakly bound van der Waals aggregates would trigger new channels of photochemical reaction pathways that are not available for gas-phase isolated molecules. Laboratory studies carried out at JPL and AMU will be discussed. Nature of Titan's haze aerosol particles will be extrapolated in the light of these laboratory studies. Ref: Gudipati et al., Nat. Commun. 4 (2013) 1648

  3. Dynamic Condensation of Mass and Stiffness Matrices

    NASA Astrophysics Data System (ADS)

    Zhang, N.

    1995-12-01

    Details are given of a procedure for condensing the mass and stiffness matrices of a structure for dynamic analysis. The condensed model is based on choosing ncnatural frequencies and the corresponding modes of original model. The model is constructed so that (1) it has ncnatural frequencies equal to those of the original model, (2) the modes φ ifcless than i,j = 1, 2, . . . , ncare the same as those for the master co-ordinates in the corresponding modes of the original and (3) the responses of the condensed system at the co-ordinates Xcdue to forces at these co-ordinates, at one particular chosen frequency, are the same as those of the original system. The natural frequencies, the corresponding modes and the dynamic responses used for the condensation can be obtained from finite element analysis of the original structure. The method has been applied to the modelling of two common structures to examine its applicability. Comparisons between the performance of the condensed models obtained by means of the dynamic condensation method and that of the models obtained by the Guyan method have been conducted. The results of the example show that the condensed models determined by the dynamic condensation method retain the natural frequencies and modal shapes and perform better in describing the dynamic responses of the structures than do the corresponding models obtained by the Guyan method.

  4. Drinking influences exhaled breath condensate acidity.

    PubMed

    Kullmann, Tamás; Barta, Imre; Antus, Balázs; Horváth, Ildikó

    2008-01-01

    Exhaled breath condensate analysis is a developing method for investigating airway pathology. Impact of food and drink on breath condensate composition has not been systematically addressed. The aim of the study was to follow exhaled breath condensate pH after drinking an acidic and a neutral beverage. Breath condensate, capillary blood, and urine of 12 healthy volunteers were collected before and after drinking either 1 l of coke or 1 l of mineral water. The pH of each sample was determined with a blood gas analyzer. The mean difference between the pH of two breath condensate samples collected within 15 min before drinking was 0.13+/-0.03. Condensate pH decreased significantly from 6.29+/-0.02 to 6.24+/-0.02 (p<0.03) after drinking coke and from 6.37+/-0.03 to 6.22+/-0.04 (p<0.003) after drinking water. Drinking coke induced significant changes in blood and urine pH as well. Drinking influences exhaled breath condensate composition and may contribute to the variability of exhaled breath condensate pH.

  5. 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.

  6. Nephron induction revisited: from caps to condensates.

    PubMed

    Sariola, Hannu

    2002-01-01

    Conversion of mesenchyme to epithelium in the metanephric kidney is clearly a multimolecular, multistep and partly redundant process. The present short review focuses on a neglected morphological aspect of kidney differentiation: the development of two transitory mesenchymal condensations that precede epithelial differentiation of nephrons. The first appearing condensate covers the tips of the collecting ducts and is termed a cap condensate. In the early kidney rudiment this structure has been referred to as a primary or early condensate. A few cells of the cap condensate (maybe only four to six cells), situated at the lateral edge of the cap, start proliferating rapidly and form a pretubular aggregate (or pretubular condensate), which converts to secretory nephron epithelia and finally segregates to different tubule segments. Throughout nephrogenesis, the cap condensates and pretubular aggregates are clearly distinguishable structures that show only partly overlapping gene expression profiles. Apart from being the source for the pretubular aggregates, the role of the cap condensate is unknown. It is now proposed that the cap regulates ureteric branching morphogenesis.

  7. 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.

  8. Fragmentation of Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Mueller, Erich J.; Ho, Tin-Lun; Ueda, Masahito; Baym, Gordon

    2006-09-01

    We present the theory of bosonic systems with multiple condensates, providing a unified description of various model systems that are found in the literature. We discuss how degeneracies, interactions, and symmetries conspire to give rise to this unusual behavior. We show that as degeneracies multiply, so do the varieties of fragmentation, eventually leading to strongly correlated states with no trace of condensation.

  9. Enhancement of Condensation on a Vertical Plate

    NASA Astrophysics Data System (ADS)

    Chu, Rencai; Hatanaka, Tsutomu; Nishio, Shigefumi

    In previous study, the characteristic of the condensation heat transfer on the dispersed vertical surface were investigated experimentally for the application of the finned surface to the thermoelectric generator utilizing boiling and condensation as the electrodes of the thermoelectric module. A prediction model for this diapered finned surface was proposed, based on Adamek-Webb model of the condensation on a finned tube. In this study, a condensation heat transfer experiment on a vertical dispersed finned surfaces using FC5312 was carried out, in order to enhance the condensation heat transfer coefficient by optimizing the fin size on a dispersed heat transfer surface. Experimental parameters were the fin width, thickness, height and the dispersed fin length. As the results, it was found from the experiment there was a dispersed fin length corresponding to the condensation at the maximum and its value was 1.75 mm. As the characteristic, the condensation changed from slowly increasing to rapidly increasing and then decreasing at a steep grade, with decreasing the dispersed fin length. In addition, the fin height did not affect this optimum dispersed fin length and the dispersed fin length affects the dependence of the condensation on different fin thickness. Further, the prediction values have a good agreement with the experimental data except the case of short dispersed fin length.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Analytic Approximation of Carbon Condensation Issues in Type ii Supernovae

    NASA Astrophysics Data System (ADS)

    Clayton, Donald D.

    2013-01-01

    I present analytic approximations for some issues related to condensation of graphite, TiC, and silicon carbide in oxygen-rich cores of supernovae of Type II. Increased understanding, which mathematical analysis can support, renders researchers more receptive to condensation in O-rich supernova gases. Taking SN 1987A as typical, my first analysis shows why the abundance of CO molecules reaches an early maximum in which free carbon remains more abundant than CO. This analysis clarifies why O-rich gas cannot oxidize C if 56Co radioactivity is as strong as in SN 1987A. My next analysis shows that the CO abundance could be regarded as being in chemical equilibrium if the CO molecule is given an effective binding energy rather than its laboratory dissociation energy. The effective binding energy makes the thermal dissociation rate of CO equal to its radioactive dissociation rate. This preserves possible relevance for the concept of chemical equilibrium. My next analysis shows that the observed abundances of CO and SiO molecules in SN 1987A rule out frequent suggestions that equilibrium condensation of SUNOCONs has occurred following atomic mixing of the He-burning shell with more central zones in such a way as to reproduce roughly the observed spectrum of isotopes in SUNOCONs while preserving C/O > 1. He atoms admixed along with the excess carbon would destroy CO and SiO molecules, leaving their observed abundances unexplained. The final analysis argues that a chemical quasiequilibrium among grains (but not gas) may exist approximately during condensation, so that its computational use is partially justified as a guide to which mineral phases would be stable against reactions with gas. I illustrate this point with quasiequilibrium calculations by Ebel & Grossman that have shown that graphite is stable even when O/C >1 if prominent molecules are justifiably excluded from the calculation of chemical equilibrium.

  17. Reactions of cresol in hot aqueous borate solutions

    SciTech Connect

    Tsao, L.; Weres, O.

    1992-04-01

    Phenol and methylphenol (cresol) are constituents of certain waste streams being considered for underground injection. We studied reactions of these compounds in solutions with other constituents of the waste streams and suspended clay at concentrations and temperatures higher than expected in natural situations, i.e. at 200{degrees}C and 250{degrees}C. Under these conditions, the predominant reaction was the demethylation of cresol to form phenol. This reaction was catalyzed strongly by clay. We were able to quantify phenol production. Other important reactions were a variety of condensation reactions in which two cresol molecules fuse. We found evidence of the intermolecular migration of methyl groups from the molecular weights of some of these condensation reactions. By digesting a sample of reacted clay with hydrofluoric acid we determined that under these conditions phenol and cresol did not bind appreciably to clay but that the condensation products did.

  18. DETAIL VIEW OF MARISCAL WORKS CONDENSER STACK, THE END OF ...

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

    DETAIL VIEW OF MARISCAL WORKS CONDENSER STACK, THE END OF THE CONDENSING SYSTEM, REUSED BY VIVIANNA WORKS AS THE END OF THEIR CONDENSING SYSTEM, LOOKING SOUTHWEST. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  19. 26. DETAIL VIEW OF MARISCAL WORKS CONDENSER STACK, THE END ...

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

    26. DETAIL VIEW OF MARISCAL WORKS CONDENSER STACK, THE END OF THE CONDENSING SYSTEM, REUSED BY VIVIANNA WORKS AS THE END OF THEIR CONDENSING SYSTEM, LOOKING SOUTHWEST. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  20. Enhancing dropwise condensation through bioinspired wettability patterning.

    PubMed

    Ghosh, Aritra; Beaini, Sara; Zhang, Bong June; Ganguly, Ranjan; Megaridis, Constantine M

    2014-11-04

    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.

  1. 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.

  2. 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%.

  3. 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.

  4. 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.

  5. Interactions of nucleic acids with fluorescent dyes: spectral properties of condensed complexes.

    PubMed

    Kapuscinski, J

    1990-09-01

    Interaction of cations with nucleic acids (NA) often results in condensation of the product. The driving force of aromatic cation-induced condensation is the cooperative interaction between ligand and single-stranded (ss) NA. This type of reaction is highly specific with regard to the primary and secondary structure of NA, and results in destabilization of the latter. The spectral properties of fluorescent intercalating and non-intercalating ligands [acridine orange, pyronin Y(G), DAPI, Hoechst 33258, and Hoechst 33342]-NA complexes were studied in both the relaxed and condensed form. The changes in absorption, excitation, and fluorescence emission spectra and fluorescence yield that followed the condensation were examined. Although some of these effects can be explained by changes in solvation of the fluorophore and its interaction with NA bases and the solvent, the overall effect of condensation on spectral properties of the complex is unpredictable. In particular, no correlation was found between these effects and the ds DNA binding mode of these ligands. Nevertheless, the spectral data associated with polymer condensation can yield information about the composition and structure of NA and can explain some nonspecific interactions of these probes.

  6. 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.

  7. 12. ANGLED VIEW OF THE SCOTT FURNACE WITH PRIMARY CONDENSER ...

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

    12. ANGLED VIEW OF THE SCOTT FURNACE WITH PRIMARY CONDENSER AND SOUTH SECONDARY CONDENSER IN BACKGROUND, LOOKING SOUTHWEST. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  8. 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

  9. 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

  10. Heterogeneous Vapor Condensation in Boundary Layers

    SciTech Connect

    Bonilla, L. L.; Carpio, A.; Neu, J. C.

    2008-09-01

    We consider heterogeneous condensation of vapors mixed with a carrier gas in stagnation point boundary layer flow near a cold wall in the presence of solid particles much larger than the mean free path of vapor particles. The supersaturated vapor condenses on the particles by diffusion, particles and droplets are thermophoretically attracted to the wall. We sketch three asymptotic theories of the condensation process, calculate the flow-induced shift in the dew point interface, vapor density profile and deposition rates at the wall, and compare them to direct numerical simulation.

  11. Microscopic theory of equilibrium polariton condensates

    NASA Astrophysics Data System (ADS)

    Xue, Fei; Wu, Fengcheng; Xie, Ming; Su, Jung-Jung; MacDonald, A. H.

    2016-12-01

    We present a microscopic theory of the equilibrium polariton condensate state of a semiconductor quantum well in a planar optical cavity. The theory accounts for the adjustment of matter excitations to the presence of a coherent photon field, predicts effective polariton-polariton interaction strengths that are weaker and condensate exciton fractions that are smaller than in the commonly employed exciton-photon model, and yields effective Rabi coupling strengths that depend on the detuning of the cavity-photon energy relative to the bare exciton energy. The dressed quasiparticle bands that appear naturally in the theory provide a mechanism for electrical manipulation of polariton condensates.

  12. Condensed Matter Theories: Volume 25

    NASA Astrophysics Data System (ADS)

    Ludeña, Eduardo V.; Bishop, Raymond F.; Iza, Peter

    2011-03-01

    dynamics and density functional theory. Exchange-correlation functionals from the identical-particle Ornstein-Zernike equation: Basic formulation and numerical algorithms / R. Cuevas-Saavedra and P. W. Ayers. Features and catalytic properties of RhCu: A review / S. Gonzalez, C. Sousa and F. Illas. Kinetic energy functionals: Exact ones from analytic model wave functions and approximate ones in orbital-free molecular dynamics / V. V. Karasiev ... [et al.]. Numerical analysis of hydrogen storage in carbon nanopores / C. Wexler ... [et al.] -- pt. F. Superconductivity. Generalized Bose-Einstein condensation in superconductivity / M. de Llano. Kohn anomaly energy in conventional superconductors equals twice the energy of the superconducting gap: How and why? / R. Chaudhury and M. P. Das. Collective excitations in superconductors and semiconductors in the presence of a condensed phase / Z. Koinov. Thermal expansion of ferromagnetic superconductors: Possible application to UGe[symbol] / N. Hatayama and R. Konno. Generalized superconducting gap in a Boson-Fermion model / T. A. Mamedov and M. de Llano. Influence of domain walls in the superconductor/ferromagnet proximity effect / E. J. Patino. Spin singlet and triplet superconductivity induced by correlated hopping interactions / L. A. Perez, J. S. Millan and C. Wang -- pt. G. Statistical mechanics, relativistic quantum mechanics. Boltzmann's ergodic hypothesis: A meeting place for two cultures / M. H. Lee. Electron-electron interaction in the non-relativistic limit / F. B. Malik.

  13. Deuteron disintegration in condensed media

    NASA Astrophysics Data System (ADS)

    Ragheb, M.; Miley, G. H.

    1990-12-01

    We discuss the Oppenheimer-Phillips process as a possible phenomenon leading to deuteron disintegration due to polarization in the Coulomb field of a target nucleus. This reaction may be possible in the context of electrochemically compressed deuterons in a palladium cathode. The process is exothermic and may lead to neutron capture from the deuterons into the palladium isotopes, as well as between the deuterons themselves. In the last case, the equivalent of the proton branch of the D-D fusion reaction occurs in preference to the neutron branch. Such a process could provide a model for the processes involved in the observed energy release and tritium production in conjunction with neutron suppression in recent experiments. Possible interactions with Be and fertile isotopes are discussed in the context of breeding fissile isotopes in subcritical configurations.

  14. The condensation of water on adsorbed viruses.

    PubMed

    Alonso, José María; Tatti, Francesco; Chuvilin, Andrey; Mam, Keriya; Ondarçuhu, Thierry; Bittner, Alexander M

    2013-11-26

    The wetting and dewetting behavior of biological nanostructures and to a greater degree single molecules is not well-known even though their contact with water is the basis for all biology. Here, we show that environmental electron microscopy (EM) can be applied as a means of imaging the condensation of water onto viruses. We captured the formation of submicrometer water droplets and filaments on single viral particles by environmental EM and by environmental transmission EM. The condensate structures are compatible with capillary condensation between adsorbed virus particles and with known droplet shapes on patterned surfaces. Our results confirm that such droplets exist down to <50 nm. The viruses preserved their shape after a condensation/evaporation cycle as expected from their stability in air and water. Moreover we developed procedures that overcome problems of beam damage and of resolving structures with a low atomic number.

  15. Nonlinear interactions in an organic polariton condensate.

    PubMed

    Daskalakis, K S; Maier, S A; Murray, R; Kéna-Cohen, S

    2014-03-01

    Under the right conditions, cavity polaritons form a macroscopic condensate in the ground state. The fascinating nonlinear behaviour of this condensate is largely dictated by the strength of polariton-polariton interactions. In inorganic semiconductors, these result principally from the Coulomb interaction between Wannier-Mott excitons. Such interactions are considerably weaker for the tightly bound Frenkel excitons characteristic of organic semiconductors and were notably absent in the first reported demonstration of organic polariton lasing. In this work, we demonstrate the realization of an organic polariton condensate, at room temperature, in a microcavity containing a thin film of 2,7-bis[9,9-di(4-methylphenyl)-fluoren-2-yl]-9,9-di(4-methylphenyl)fluorene. On reaching threshold, we observe the spontaneous formation of a linearly polarized condensate, which exhibits a superlinear power dependence, long-range order and a power-dependent blueshift: a clear signature of Frenkel polariton interactions.

  16. Scanning Tunneling Microscopy Observation of Phonon Condensate.

    PubMed

    Altfeder, Igor; Voevodin, Andrey A; Check, Michael H; Eichfeld, Sarah M; Robinson, Joshua A; Balatsky, Alexander V

    2017-02-22

    Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formation of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature.

  17. 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.

  18. Ferromagnetic properties of charged vector boson condensate

    SciTech Connect

    Dolgov, Alexander D.; Lepidi, Angela; Piccinelli, Gabriella E-mail: lepidi@fe.infn.it

    2010-08-01

    Bose-Einstein condensation of W bosons in the early universe is studied. It is shown that, in the broken phase of the standard electroweak theory, the condensed W bosons form a ferromagnetic state with aligned spins. In this case the primeval plasma may be spontaneously magnetized inside macroscopically large domains and form magnetic fields which may be the seeds for the observed today galactic and intergalactic fields. However, in a modified theory, e.g. in a theory with stronger quartic self interactions of gauge bosons e.g. due to a smaller value of the weak mixing angle, antiferromagnetic condensation is possible. In the latter case W bosons form scalar condensate with macroscopically large electric charge density i.e. with a large average value of the bilinear product of W-vector fields but with microscopically small average value of the field itself.

  19. 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.

  20. Ghost Condensation in N=1 Supergravity

    NASA Astrophysics Data System (ADS)

    Koehn, Michael; Lehners, Jean-Luc; Ovrut, Burt

    We present the theory of an N=1 supersymmetric ghost condensate coupled to supergravity using a general formalism for constructing locally supersymmetric higher-derivative chiral superfield actions. The theory admits a ghost condensate vacuum in de Sitter spacetime. Expanded around this vacuum, the scalar sector is shown to be ghost-free with no spatial gradient instabilities. The fermion sector is found to consist of a massless chiral fermion and a massless gravitino. The ghost condensate vacuum spontaneously breaks local supersymmetry with the chiral field as the Goldstone fermion. Although potentially able to get a mass through the super-Higgs effect, the vanishing superpotential in the ghost condensate theory renders the gravitino massless.

  1. 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)

  2. Scanning Tunneling Microscopy Observation of Phonon Condensate

    PubMed Central

    Altfeder, Igor; Voevodin, Andrey A.; Check, Michael H.; Eichfeld, Sarah M.; Robinson, Joshua A.; Balatsky, Alexander V.

    2017-01-01

    Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formation of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature. PMID:28225066

  3. Condensed-matter trio scoop Dirac prize

    NASA Astrophysics Data System (ADS)

    Durrani, Matin

    2012-09-01

    Three condensed-matter physicists, who have advanced our understanding of a strange type of material known as a "topological insulator", have won this year's Dirac medal from the International Centre for Theoretical Physics (ICTP) in Trieste, Italy.

  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. Passive control of unsteady condensation shock wave

    NASA Astrophysics Data System (ADS)

    Setoguchi, Toshiaki; Matsuo, Shigeru; Shimamoto, Katsumi; Yasugi, Shinichi; Yu, Shen

    2000-12-01

    A rapid expansion of moist air or steam in a supersonic nozzle gives rise to nonequilibrium condensation phenomena. Thereby, if the heat released by condensation of water vapour exceeds a certain quantity, the flow will become unstable and periodic flow oscillations of the unsteady condensation shock wave will occur. For the passive control of shock-boundary layer interaction using the porous wall with a plenum underneath, many papers have been presented on the application of the technique to transonic airfoil flows. In this paper, the passive technique is applied to three types of oscillations of the unsteady condensation shock wave generated in a supersonic nozzle in order to suppress the unsteady behavior. As a result, the effects of number of slits and length of cavity on the aspect of flow field have been clarified numerically using a 3rd-order MUSCL type TVD finite-difference scheme with a second-order fractional-step for time integration.

  6. 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.

  7. Molecular equilibrium with condensation. [in astrophysics

    NASA Technical Reports Server (NTRS)

    Sharp, C. M.; Huebner, W. F.

    1990-01-01

    Minimization of the Gibbs energy of formation for species of chemical elements and compounds in their gas and condensed phases determines their relative abundances in a mixture in chemical equilibrium. The procedure is more general and more powerful than previous abundance determinations in multiphase astrophysical mixtures. Some results for astrophysical equations of state are presented, and the effects of condensation on opacity are briefly indicated.

  8. 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.

  9. 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.

  10. Enhancement of Condensation on a Vertical Plate

    NASA Astrophysics Data System (ADS)

    Chu, Rencai; Hatanaka, Tsutomu; Nishio, Shigefumi

    In previous study, the characteristic of the condensation heat transfer on the dispersed vertical surface were investigated experimentally for the application of the finned surface to the thermoelectric generator utilizing boiling and condensation as the electrodes of the thermoelectric module. A prediction model for this diapered finned surface was proposed, based on Adamek-Webb model of the condensation on a finned tube. In this study, a condensation heat transfer experiment on a vertical dispersed finned surfaces using FC5312 was carried out, in order to enhance the condensation heat transfer coefficient by optimizing the fin size on a dispersed heat transfer surface. The object of the experiment was limited to the rectangular fin with the height of 3 mm. Experimental parameters were the temperature difference, the fin groove width, the fin thickness and the dispersing size on the vertical direction. As the results, it was found from the experiment that the dependence of the condensation heat transfer coefficient on the dispersed size is controlled by the fin groove width. That is, the condensation heat transfer coefficient will increase for a smaller fin groove width and will decrease for a larger fin groove width, with decreasing of the dispersing size. Moreover, there is an optimum fin thickness at which the condensation heat transfer coefficient becomes the maximum in the case of constant fin groove width for both size of the fin groove width. This effect of the fin thickness is more significant for the smaller fin groove width. Further, the prediction values exhibit a good agreement with the experimental data in the present experiment.

  11. Dual condensates at finite isospin chemical potential

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao; Miao, Qing

    2016-02-01

    The dual observables as order parameters for center symmetry are tested at finite isospin chemical potential μI in a Polyakov-loop enhanced chiral model of QCD with physical quark masses. As a counterpart of the dressed Polyakov-loop, the first Fourier moment of pion condensate is introduced for μI >mπ / 2 under the temporal twisted boundary conditions for quarks. We demonstrate that this dual condensate exhibits the similar temperature dependence as the conventional Polyakov-loop. We confirm that its rapid increase with T is driven by the evaporating of pion condensation. On the other hand, the dressed Polyakov-loop shows abnormal thermal behavior, which even decreases with T at low temperatures due to the influence of pion condensate. We also find that the dressed Polyakov-loop always rises most steeply at the chiral transition temperature, which is consistent with the previous results in Nambu-Jona-Lasinio (NJL) model and its variants without considering the center symmetry. Since both quantities are strongly affected by the chiral symmetry and pion condensation, we conclude that it is difficult to clarify the deconfinement transition from the dual condensates in this situation within this model.

  12. Interstitial Condensation Risk at Thermal Rehabilitated Buildings

    NASA Astrophysics Data System (ADS)

    Baran, I.; Bliuc, I.; Iacob, A.; Dumitrescu, L.; Pescaru, R. A.; Helepciuc, C.

    2016-11-01

    The increasing thermal insulation degree of existing residential buildings, aiming to reduce the energy requirements for ensuring the indoor comfort, has as expected effect the elimination of condensation risk. However, in some cases this phenomenon occurs, both on the inner surface of the closing element and also in its structure. The surface condensation causes can be identified and can be easily removed. Instead, the causes and even the presence of interstitial condensation are more difficult to be observed. But the moistening of the insulation materials and the reduction of thermal insulation capacity or even its total degradation, contravene into a large extent or totally to the main purpose of the additional thermal protection. To avoid such situations, it is necessary to respect some principles concerning the structure, resulted from the knowledge of the water vapour diffusion behaviour of various materials. It is known that condensation vulnerability is higher for the additional thermal protection solutions by disposing the insulating material on the inside surface of the closing element. But practice has shown that the condensation phenomenon is not totally excluded neither in the case of outside thermal insulation - which is the current solution applied to the rehabilitation works - if the principles mentioned above are not known and respected. In this paper two models are compared on which the risk of interstitial condensation can be checked. The analysis made on two structures of exterior walls with thermal insulation demonstrates the need for additional verifications before proposing a solution for thermal rehabilitation of the envelope elements.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  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. 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

  1. 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

  2. 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

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 46 CFR 56.50-35 - Condensate pumps.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 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...

  8. 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.

  9. 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.

  10. Nanoscopic structure of DNA condensed for gene delivery.

    PubMed Central

    Dunlap, D D; Maggi, A; Soria, M R; Monaco, L

    1997-01-01

    Scanning force microscopy was used to examine DNA condensates prepared with varying stoichiometries of lipospermine or polyethylenimine in physiological solution. For the first time, individual DNA strands were clearly visualized in incomplete condensates without drying. Using lipospermine at sub-saturating concentrations, discrete nuclei of condensation were observed often surrounded by folded loops of DNA. Similar packing of DNA loops occurred for polyethylenimine-induced condensation. Increasing the amount of the condensing agent led to the progressive coalescence or aggregation of initial condensation nuclei through folding rather than winding the DNA. At over-saturating charge ratios of the cationic lipid or polymer to DNA, condensates had sizes smaller than or equal to those measured previously in electron micrographs. Polyethylenimine condensates were more compact than lipospermine condensates and both produced more homogeneously compacted plasmids when used in a 2-4-fold charge excess. The size and morphology of the condensates may affect their efficiency in transfection. PMID:9224610

  11. 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.

  12. Protonation, Hydrolysis, and Condensation of Mono- and Trifunctional Silanes at the Air/Water Interface

    PubMed Central

    Britt, David W.; Hlady, Vladimir

    2012-01-01

    The protonation, hydrolysis, and condensation kinetics of octadecyldimethylmethoxysilane (OMMS) and octadecyltrimethoxysilane (OTMS) at the air/water interface were investigated using a monolayer trough. OTMS chemical condensation within physically condensed phases was observed in transferred monolayers using fluorescence microscopy. Molecular area increases and decreases attributed to protonation and hydrolysis, respectively, of silane methoxy groups were measured by a surface balance. These area changes at constant surface pressure suggested a stepwise protonation and hydrolysis of the three OTMS methoxy groups. In contrast, only a single protonation and hydrolysis event was observed for monofunctional OMMS. The influences of monolayer spreading time, silane packing density, and subphase pH on the reaction kinetics are presented. PMID:25147424

  13. GENOTOXICITY OF TEN CIGARETTE SMOKE CONDENSATES IN FOUR TEST SYSTEMS: COMPARISONS BETWEEN ASSAYS AND CONDENSATES

    EPA Science Inventory

    What is the study?
    This the first assessment of a set of cigarette smoke condensates from a range of cigarette types in a variety (4) of short-term genotoxicity assays.
    Why was it done?
    No such comparative study of cigarette smoke condensates has been reported. H...

  14. Click with a boronic acid handle: a neighboring group-assisted click reaction that allows ready secondary functionalization.

    PubMed

    Draganov, Alexander B; Wang, Ke; Holmes, Jalisa; Damera, Krishna; Wang, Danzhu; Dai, Chaofeng; Wang, Binghe

    2015-10-21

    The feasibility of a neighboring boronic acid-facilitated facile condensation of an aldehyde is described. This reaction is bio-orthogonal, complete at room temperature within minutes, and suitable for bioconjugation chemistry. The boronic acid group serves the dual purpose of catalyzing the condensation reaction and being a handle for secondary functionalization.

  15. Structure of vacuum Cu–Ta condensates

    NASA Astrophysics Data System (ADS)

    Zubkov, A. I.; Zubarev, E. N.; Sobol', O. V.; Hlushchenko, M. A.; Lutsenko, E. V.

    2017-02-01

    The structure of vacuum condensate foils (separated from substrates) of the binary Cu-Ta system has been investigated both in the initial condensed state and after annealings at temperatures of up to 1000°C. It has been shown that the alloying of a vapor flow of the matrix metal (copper) with tantalum to 0.5 at % makes it possible to reduce the grain size from 3 μm to 50 nm. Depending on the tantalum concentration, condensates exhibit a broad spectrum of structural states, i.e., single- and two-phase, a supersaturated solution of tantalum in the fcc lattice of copper, etc. The structure of the objects possesses a high thermal stability. The temperature of the start of grain growth in the copper matrix depends on the tantalum content and can reach 900°C. The dispersion of the structure of copper condensates and its thermal stability is due to the formation of segregates of tantalum atoms at the boundaries of grains of the copper matrix both in the process of condensation and upon subsequent annealing.

  16. Laser Isotope Separation Employing Condensation Repression

    SciTech Connect

    Eerkens, Jeff W.; Miller, William H.

    2004-09-15

    Molecular laser isotope separation (MLIS) techniques using condensation repression (CR) harvesting are reviewed and compared with atomic vapor laser isotope separation (AVLIS), gaseous diffusion (DIF), ultracentrifuges (UCF), and electromagnetic separations (EMS). Two different CR-MLIS or CRISLA (Condensation Repression Isotope Separation by Laser Activation) approaches have been under investigation at the University of Missouri (MU), one involving supersonic super-cooled free jets and dimer formation, and the other subsonic cold-wall condensation. Both employ mixtures of an isotopomer (e.g. {sup i}QF{sub 6}) and a carrier gas, operated at low temperatures and pressures. Present theories of VT relaxation, dimerization, and condensation are found to be unsatisfactory to explain/predict experimental CRISLA results. They were replaced by fundamentally new models that allow ab-initio calculation of isotope enrichments and predictions of condensation parameters for laser-excited and non-excited vapors which are in good agreement with experiment. Because of supersonic speeds, throughputs for free-jet CRISLA are a thousand times higher than cold-wall CRISLA schemes, and thus preferred for large-quantity Uranium enrichments. For small-quantity separations of (radioactive) medical isotopes, the simpler coldwall CRISLA method may be adequate.

  17. Infrared applications for steam turbine condenser systems

    NASA Astrophysics Data System (ADS)

    Lanius, Mark A.

    2000-03-01

    Infrared inspection of the main steam condensers at the Peach Bottom Atomic Power Station has been utilized successfully in detecting condenser air in-leakage problems. Air in-leakage lowers the condenser's vacuum, thus decreasing the condenser's efficiency. This creates backpressure on the turbine which lowers its efficiency, resulting in fewer megawatts generated. Air in-leakage also creates an increase in off-gas flow which is a radiological concern for both the plant and the public. Inspections are normally performed on the condenser's manway covers and rupture disks prior to an outage during coast down and post outage. The optimum conditions are 100% power and temperature, however, a high radiation field prevents the inspection until reactor power is down to 65% or less. Anomalies are typically indicated by cooling in the effected areas of the air in-leakage. The anomalies are not limited to air in-leakage. Intermittent water out-leakage, due to a heater dump valve cycling, has been detected when visual inspections field nothing.

  18. Why double-stranded RNA resists condensation.

    PubMed

    Tolokh, Igor S; Pabit, Suzette A; Katz, Andrea M; Chen, Yujie; Drozdetski, Aleksander; Baker, Nathan; Pollack, Lois; Onufriev, Alexey V

    2014-01-01

    The addition of small amounts of multivalent cations to solutions containing double-stranded DNA leads to inter-DNA attraction and eventual condensation. Surprisingly, the condensation is suppressed in double-stranded RNA, which carries the same negative charge as DNA, but assumes a different double helical form. Here, we combine experiment and atomistic simulations to propose a mechanism that explains the variations in condensation of short (25 base-pairs) nucleic acid (NA) duplexes, from B-like form of homopolymeric DNA, to mixed sequence DNA, to DNA:RNA hybrid, to A-like RNA. Circular dichroism measurements suggest that duplex helical geometry is not the fundamental property that ultimately determines the observed differences in condensation. Instead, these differences are governed by the spatial variation of cobalt hexammine (CoHex) binding to NA. There are two major NA-CoHex binding modes--internal and external--distinguished by the proximity of bound CoHex to the helical axis. We find a significant difference, up to 5-fold, in the fraction of ions bound to the external surfaces of the different NA constructs studied. NA condensation propensity is determined by the fraction of CoHex ions in the external binding mode.

  19. The NSF Condensed Matter Physics Program

    NASA Astrophysics Data System (ADS)

    Sokol, Paul

    The Condensed Matter Physics (CMP) program in the NSF Division of Materials Research (DMR) supports experimental, as well as combined experiment and theory projects investigating the fundamental physics behind phenomena exhibited by condensed matter systems. CMP is the largest Individual Investigator Award program in DMR and supports a broad portfolio of research spanning both hard and soft condensed matter. Representative research areas include: 1) phenomena at the nano- to macro-scale including: transport, magnetic, and optical phenomena; classical and quantum phase transitions; localization; electronic, magnetic, and lattice structure or excitations; superconductivity; topological insulators; and nonlinear dynamics. 2) low-temperature physics: quantum fluids and solids; 1D & 2D electron systems. 3) soft condensed matter: partially ordered fluids, granular and colloid physics, liquid crystals, and 4) understanding the fundamental physics of new states of matter as well as the physical behavior of condensed matter under extreme conditions e.g., low temperatures, high pressures, and high magnetic fields. In this talk I will review the current CMP portfolio and discuss future funding trends for the program. I will also describe recent activities in the program aimed at addressing the challenges facing current and future principal investigators.

  20. Diurnal and nocturnal variance between condensation, evaporation and transpiration under high altitude conditions

    NASA Astrophysics Data System (ADS)

    de Jong, C.; Mundelius, M.

    2003-04-01

    Several important parameters of the water cycle, such as condensation, evaporation and transpiration have been largely neglected in mountain areas, even though they are important for ecology, hydrology and meteorology. Estimations and extrapolations do not adequately cover the spatial and temporal heterogeneity of these parameters in steep, higher altitude terrain, nor is the occurrence of special components such as condensation considered. Diurnal and nocturnal variance between the processes of condensation, evaporation and transpiration are important as a basis for modelling and understanding the regional dynamics of water fluxes. Intensive field experiments using automatically-recording lysimeters and evaporation pans during the snow-free period above the tree-line form the basis of this study. Investigation areas include the humid Dischma valley in E. Switzerland and the heavily fog-influenced Reifträger catchment in the Giant mountains in Poland. Directly measured water flux data from sites within alpine shrubs, grass and pasture are coupled with climatic information for each site. Differences in condensation between vegetated and non-vegetated surfaces are highest in reaction to early morning and late evening plant dynamics coupled with extreme temperature changes. Variance between evaporation and transpiration is lower, depending on plant type, valley shape and climatic influences. Diurnal and nocturnal water losses from non-vegetated surfaces are slightly delayed with respect to vegetated surfaces. The results are modelled using an extended Priestley-Taylor approach for evaporation and transpiration and a conceptual model for condensation.

  1. The role of organic condensation on ultrafine particle growth during nucleation events

    NASA Astrophysics Data System (ADS)

    Patoulias, D.; Fountoukis, C.; Riipinen, I.; Pandis, S. N.

    2015-06-01

    A new aerosol dynamics model (DMANx) has been developed that simulates aerosol size/composition distribution and includes the condensation of organic vapors on nanoparticles through the implementation of the recently developed volatility basis set framework. Simulations were performed for Hyytiälä (Finland) and Finokalia (Greece), two locations with different organic sources where detailed measurements were available to constrain the new model. We investigate the effect of condensation of organics and chemical aging reactions of secondary organic aerosol (SOA) precursors on ultrafine particle growth and particle number concentration during a typical springtime nucleation event in both locations. This work highlights the importance of the pathways of oxidation of biogenic volatile organic compounds and the production of extremely low volatility organics. At Hyytiälä, organic condensation dominates the growth process of new particles. The low-volatility SOA contributes to particle growth during the early growth stage, but after a few hours most of the growth is due to semi-volatile SOA. At Finokalia, simulations show that organics have a complementary role in new particle growth, contributing 45% to the total mass of new particles. Condensation of organics increases the number concentration of particles that can act as CCN (cloud condensation nuclei) (N100) by 13% at Finokalia and 25% at Hyytiälä during a typical spring day with nucleation. The sensitivity of our results to the surface tension used is discussed.

  2. Semisynthesis of sperm whale myoglobin by fragment condensation.

    PubMed

    Simmerman, H K; Wang, C C; Horwitz, E M; Berzofsky, J A; Gurd, F R

    1982-12-01

    Reconstruction of the sperm whale myoglobin structure was accomplished by a series of aqueous condensations of suitably protected synthetic myoglobin fragments to a large fragment prepared from the native protein. Reaction of N alpha,N epsilon 19-acetimidomyoglobin with 3-bromo-2-(2-nitrophenylsulfenyl)skatole (BNPS-skatole) yielded the fragment corresponding to residues 15-153. The covalent structure was reformed by sequential coupling of the N-hydroxysuccinimide esters of o-nitrophenylsulfenyl-L-tryptophan (residue 14) and selectively protected peptides corresponding to residues 1-5 and 6-13, which were synthesized by the solid-phase method and removed from the resin by methoxide-catalyzed methanolysis. A mixed aqueous solvent system containing methanol and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine/trifluoroacetic acid buffer (Quadrol) solubilized the peptide and protein fragments during the condensations. Replacement of the heme moiety and immunoaffinity chromatography made possible the isolation and purification of the reconstructed native molecule. The development of this nondestructive synthetic procedure allows investigation of the structural and functional significance of individual residues by isotopic enrichment or selective amino acid substitutions.

  3. Condensation of activated diguanylates on a poly(C) template.

    PubMed

    Lohrmann, R; Bridson, P K; Orgel, L E

    1981-01-01

    We have studied the metal-ion catalysis of a number of reactions of the isomers of ImpGpG on a poly(C) template. In the absence of a catalytic metal ion, oligomers at least up to (pG)20 are obtained from the ImpGpG isomers in a 1-methylimidazole buffer. The Pb2+ ion improves the yield of longer oligomers and changes substantially the distribution of linkage isomers. The Pb2+ ion greatly improves the yield of longer oligomers obtained from G and ImpGpG on a poly(C) template. The self-condensation of ImpGpG in a 2, 6-lutidine buffer is much less efficient than in a 1-methylimidazole buffer. The Zn2+ greatly increases the yield of products from the [3'-5']-linked dimer, but fails to catalyze the formation of long oligomers from the [2'-5']-linked dimer. The bonds formed in the Zn2+-catalyzed self-condensation of ImpG3pG on poly(C) are mainly [3'-5']-linked.

  4. Acid-base bifunctional catalysis of silica-alumina-supported organic amines for carbon-carbon bond-forming reactions.

    PubMed

    Motokura, Ken; Tomita, Mitsuru; Tada, Mizuki; Iwasawa, Yasuhiro

    2008-01-01

    Acid-base bifunctional heterogeneous catalysts were prepared by the reaction of an acidic silica-alumina (SA) surface with silane-coupling reagents possessing amino functional groups. The obtained SA-supported amines (SA-NR2) were characterized by solid-state 13C and 29Si NMR spectroscopy, FT-IR spectroscopy, and elemental analysis. The solid-state NMR spectra revealed that the amines were immobilized by acid-base interactions at the SA surface. The interactions between the surface acidic sites and the immobilized basic amines were weaker than the interactions between the SA and free amines. The catalytic performances of the SA-NR2 catalysts for various carbon-carbon bond-forming reactions, such as cyano-ethoxycarbonylation, the Michael reaction, and the nitro-aldol reaction, were investigated and compared with those of homogeneous and other heterogeneous catalysts. The SA-NR2 catalysts showed much higher catalytic activities for the carbon-carbon bond-forming reactions than heterogeneous amine catalysts using other supports, such as SiO2 and Al2O3. On the other hand, homogeneous amines hardly promoted these reactions under similar reaction conditions, and the catalytic behavior of SA-NR2 was also different from that of MgO, which was employed as a typical heterogeneous base. An acid-base dual-activation mechanism for the carbon-carbon bond-forming reactions is proposed.

  5. Dropwise condensation over superhydrophobic aluminium surfaces

    NASA Astrophysics Data System (ADS)

    Parin, R.; Del, D., Col; Bortolin, S.; Martucci, A.

    2016-09-01

    Superhydrophobic aluminum surfaces have been analyzed being a promising solution to promote dropwise condensation. Superhydrophobicity has been obtained on an aluminum substrate by etching it with two different reagents and by depositing a fluorosilane film over them to lower the surface energy. The samples are characterized by means of contact angle measurements and Scanning Electron Microscopy (SEM). Experimental tests of pure steam condensation have been carried out on the samples and DWC has been visualized. Images of the dropwise condensation have been captured with high speed camera and, furthermore, the phenomenon of the jumping droplets has been observed. A heat transfer coefficient higher than 50 kW m-2 K-1 has been measured over the samples.

  6. Vector meson condensation in a pion superfluid

    NASA Astrophysics Data System (ADS)

    Brauner, Tomáš; Huang, Xu-Guang

    2016-11-01

    We revisit the suggestion that charged ρ -mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu-Jona-Lasinio (NJL) model, we conclude that ρ -meson condensation is either avoided or postponed to isospin chemical potentials much higher than the ρ -meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and ρ -mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.

  7. Preoperational test report, recirculation condenser cooling systems

    SciTech Connect

    Clifton, F.T.

    1997-11-04

    This represents a preoperational test report for Recirculation Condenser Systems, Project W-030. Project W-030 provides a ventilation upgrade for the four Aging Waste Facility tanks. The four system provide condenser cooling water for vapor space cooling of tanks AY1O1, AY102, AZ1O1, AZ102. Each system consists of a valved piping loop, a pair of redundant recirculation pumps, a closed-loop evaporative cooling tower, and supporting instrumentation; equipment is located outside the farm on concrete slabs. Piping is routed to the each ventilation condenser inside the farm via below-grade concrete trenches. The tests verify correct system operation and correct indications displayed by the central Monitor and Control System.

  8. Quantum Langevin model for nonequilibrium condensation

    NASA Astrophysics Data System (ADS)

    Chiocchetta, Alessio; Carusotto, Iacopo

    2014-08-01

    We develop a quantum model for nonequilibrium Bose-Einstein condensation of photons and polaritons in planar microcavity devices. The model builds on laser theory and includes the spatial dynamics of the cavity field, a saturation mechanism, and some frequency dependence of the gain: quantum Langevin equations are written for a cavity field coupled to a continuous distribution of externally pumped two-level emitters with a well-defined frequency. As an example of application, the method is used to study the linearized quantum fluctuations around a steady-state condensed state. In the good-cavity regime, an effective equation for the cavity field only is proposed in terms of a stochastic Gross-Pitaevskii equation. Perspectives in view of a full quantum simulation of the nonequilibrium condensation process are finally sketched.

  9. DROPWISE CONDENSATION ON MICRO- AND NANOSTRUCTURED SURFACES

    SciTech Connect

    Enright, R; Miljkovic, N; Alvarado, JL; Kim, K; Rose, JW

    2014-07-23

    In this review we cover recent developments in the area of surface-enhanced dropwise condensation against the background of earlier work. The development of fabrication techniques to create surface structures at the micro-and nanoscale using both bottom-up and top-down approaches has led to increased study of complex interfacial phenomena. In the heat transfer community, researchers have been extensively exploring the use of advanced surface structuring techniques to enhance phase-change heat transfer processes. In particular, the field of vapor-to-liquid condensation and especially that of water condensation has experienced a renaissance due to the promise of further optimizing this process at the micro-and nanoscale by exploiting advances in surface engineering developed over the last several decades.

  10. Comparison of sugar molecule decomposition through glucose and fructose: a high-level quantum chemical study.

    SciTech Connect

    Assary, R. S.; Curtiss, L. A.

    2012-02-01

    Efficient chemical conversion of biomass is essential to produce sustainable energy and industrial chemicals. Industrial level conversion of glucose to useful chemicals, such as furfural, hydroxymethylfurfural, and levulinic acid, is a major step in the biomass conversion but is difficult because of the formation of undesired products and side reactions. To understand the molecular level reaction mechanisms involved in the decomposition of glucose and fructose, we have carried out high-level quantum chemical calculations [Gaussian-4 (G4) theory]. Selective 1,2-dehydration, keto-enol tautomerization, isomerization, retro-aldol condensation, and hydride shifts of glucose and fructose molecules were investigated. Detailed kinetic and thermodynamic analyses indicate that, for acyclic glucose and fructose molecules, the dehydration and isomerization require larger activation barriers compared to the retro-aldol reaction at 298 K in neutral medium. The retro-aldol reaction results in the formation of C2 and C4 species from glucose and C3 species from fructose. The formation of the most stable C3 species, dihydroxyacetone from fructose, is thermodynamically downhill. The 1,3-hydride shift leads to the cleavage of the C-C bond in the acyclic species; however, the enthalpy of activation is significantly higher (50-55 kcal/mol) than that of the retro-aldol reaction (38 kcal/mol) mainly because of the sterically hindered distorted four-membered transition state compared to the hexa-membered transition state in the retro-aldol reaction. Both tautomerization and dehydration are catalyzed by a water molecule in aqueous medium; however, water has little effect on the retro-aldol reaction. Isomerization of glucose to fructose and glyceraldehyde to dihydroxyacetone proceeds through hydride shifts that require an activation enthalpy of about 40 kcal/mol at 298 K in water medium. This investigation maps out accurate energetics of the decomposition of glucose and fructose molecules

  11. Why double-stranded RNA resists condensation

    SciTech Connect

    Tolokh, Igor S.; Pabit, Suzette; Katz, Andrea M.; Chen, Yujie; Drozdetski, Aleksander; Baker, Nathan A.; Pollack, Lois; Onufriev, Alexey

    2014-09-15

    The addition of small amounts of multivalent cations to solutions containing double-stranded DNA leads to attraction between the negatively charged helices and eventually to condensation. Surprisingly, this effect is suppressed in double-stranded RNA, which carries the same charge as the DNA, but assumes a different double helical form. However, additional characterization of short (25 base-pairs) nucleic acid (NA) duplex structures by circular dichroism shows that measured differences in condensation are not solely determined by duplex helical geometry. Here we combine experiment, theory, and atomistic simulations to propose a mechanism that connects the observed variations in condensation of short NA duplexes with the spatial variation of cobalt hexammine (CoHex) binding at the NA duplex surface. The atomistic picture that emerged showed that CoHex distributions around the NA reveals two major NA-CoHex binding modes -- internal and external -- distinguished by the proximity of bound CoHex to the helical axis. Decreasing trends in experimentally observed condensation propensity of the four studied NA duplexes (from B-like form of homopolymeric DNA, to mixed sequence DNA, to DNA:RNA hybrid, to A-like RNA) are explained by the progressive decrease of a single quantity: the fraction of CoHex ions in the external binding mode. Thus, while NA condensation depends on a complex interplay between various structural and sequence features, our coupled experimental and theoretical results suggest a new model in which a single parameter connects the NA condensation propensity with geometry and sequence dependence of CoHex binding.

  12. Condensation of gauge interacting massless fermions

    SciTech Connect

    Siringo, Fabio

    2004-09-15

    A single massless fermionic field with an Abelian U(1) gauge interaction (electrodynamics of a massless Dirac fermion) is studied by a variational method. Even without the insertion of any extra interaction the vacuum is shown to be unstable towards a particle-antiparticle condensate. The single particle excitations do acquire a mass and behave as massive Fermi particles. An explicit low-energy gap equation has been derived and numerically solved. Some consequences of condensation and mass generation are discussed in the framework of the standard model.

  13. Condenser optic with sacrificial reflective surface

    DOEpatents

    Tichenor, Daniel A.; Kubiak, Glenn D.; Lee, Sung Hun

    2007-07-03

    Employing collector optics that has a sacrificial reflective surface can significantly prolong the useful life of the collector optics and the overall performance of the condenser in which the collector optics are incorporated. The collector optics is normally subject to erosion by debris from laser plasma source of radiation. The presence of an upper sacrificial reflective surface over the underlying reflective surface effectively increases the life of the optics while relaxing the constraints on the radiation source. Spatial and temporally varying reflectivity that results from the use of the sacrificial reflective surface can be accommodated by proper condenser design.

  14. Condenser optic with sacrificial reflective surface

    DOEpatents

    Tichenor, Daniel A.; Kubiak, Glenn D.; Lee, Sang Hun

    2006-07-25

    Employing collector optics that have a sacrificial reflective surface can significantly prolong the useful life of the collector optics and the overall performance of the condenser in which the collector optics are incorporated. The collector optics are normally subject to erosion by debris from laser plasma source of radiation. The presence of an upper sacrificial reflective surface over the underlying reflective surface effectively increases the life of the optics while relaxing the constraints on the radiation source. Spatial and temporally varying reflectivity that results from the use of the sacrificial reflective surface can be accommodated by proper condenser design.

  15. Colored condensates deep inside neutron stars

    NASA Astrophysics Data System (ADS)

    Blaschke, David

    2014-09-01

    It is demonstrated how in the absence of solutions for QCD under conditions deep inside compact stars an equation of state can be obtained within a model that is built on the basic symmetries of the QCD Lagrangian, in particular chiral symmetry and color symmetry. While in the vacuum the chiral symmetry is spontaneously broken, it gets restored at high densities. Color symmetry, however, gets broken simultaneously by the formation of colorful diquark condensates. It is shown that a strong diquark condensate in cold dense quark matter is essential for supporting the possibility that such states could exist in the recently observed pulsars with masses of 2 Mʘ.

  16. Dynamic condensation blocking in cryogenic refueling

    NASA Astrophysics Data System (ADS)

    Osipov, V. V.; Muratov, C. B.

    2008-12-01

    We demonstrate that a negative feedback between vapor pressure and condensation rate may be established in two-phase systems during vapor compression with rates of practical importance. As a result, dynamic condensation blocking occurs. The effect is studied numerically in the case of filling a no-vent insulated tank by liquid hydrogen. It is shown that the filling dynamics quite sensitively depends on the filling rate, and for sufficiently fast filling rates consist of a fast stage dominated by gas compression and a slow stage governed by heat conduction in the liquid.

  17. Bose-Einstein condensation. Twenty years after

    DOE PAGES

    Bagnato, V. S.; Frantzeskakis, D. J.; Kevrekidis, P. G.; ...

    2015-02-23

    The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.

  18. Geometric approach to condensates in holographic QCD

    SciTech Connect

    Hirn, Johannes; Rius, Nuria; Sanz, Veronica

    2006-04-15

    An SU(N{sub f})xSU(N{sub f}) Yang-Mills theory on an extra-dimensional interval is considered, with appropriate symmetry-breaking boundary conditions on the IR brane. UV-brane to UV-brane correlators at high energies are compared with the OPE of two-point functions of QCD quark currents. Condensates correspond to departure from the AdS metric of the (different) metrics felt by vector and axial combinations, away from the UV brane. Their effect on hadronic observables is studied: the extracted condensates agree with the signs and orders of magnitude expected from QCD.

  19. Condensation-induced jumping water drops.

    PubMed

    Narhe, R D; Khandkar, M D; Shelke, P B; Limaye, A V; Beysens, D A

    2009-09-01

    Water droplets can jump during vapor condensation on solid benzene near its melting point. This phenomenon, which can be viewed as a kind of micro scale steam engine, is studied experimentally and numerically. The latent heat of condensation transferred at the drop three phase contact line melts the substrate during a time proportional to R (the drop radius). The wetting conditions change and a spontaneous jump of the drop results in random direction over length approximately 1.5R , a phenomenon that increases the coalescence events and accelerates the growth. Once properly rescaled by the jump length scale, the growth dynamics is, however, similar to that on a solid surface.

  20. Condensation-induced jumping water drops

    NASA Astrophysics Data System (ADS)

    Narhe, R. D.; Khandkar, M. D.; Shelke, P. B.; Limaye, A. V.; Beysens, D. A.

    2009-09-01

    Water droplets can jump during vapor condensation on solid benzene near its melting point. This phenomenon, which can be viewed as a kind of micro scale steam engine, is studied experimentally and numerically. The latent heat of condensation transferred at the drop three phase contact line melts the substrate during a time proportional to R (the drop radius). The wetting conditions change and a spontaneous jump of the drop results in random direction over length ˜1.5R , a phenomenon that increases the coalescence events and accelerates the growth. Once properly rescaled by the jump length scale, the growth dynamics is, however, similar to that on a solid surface.

  1. Atomic Phase Conjugation From a Bose Condensate

    PubMed Central

    Goldstein, Elena V.; Plättner, Katja; Meystre, Pierre

    1996-01-01

    We discuss the possibility of observing atomic phase conjugation from Bose condensates, and using it as a diagnostic tool to access the spatial coherence properties and to measure the lifetime of the condensate. We argue that since phase conjugation results from the scattering of a partial matter wave off the spatial grating produced by two other waves, it offers a natural way to directly measure such properties, and as such provides an attractive alternative to the optical methods proposed in the past. PMID:27805111

  2. Neutron star cooling and pion condensation

    NASA Technical Reports Server (NTRS)

    Umeda, Hideyuki; Nomoto, Ken'ichi; Tsuruta, Sachiko; Muto, Takumi; Tatsumi, Toshitaka

    1994-01-01

    The nonstandard cooling of a neutron star with the central pion core is explored. By adopting the latest results from the pion condensation theory, neutrino emissivity is calulated for both pure charged pions and a mixture of charged and neutral pions, and the equations of state are constructed for the pion condensate. The effect of superfluidity on cooling is investigated, adopting methods more realistic than in previous studies. Our theoretical models are compared with the currently updated observational data, and possible implications are explored.

  3. Experimental Investigation of Flow Condensation in Microgravity

    NASA Technical Reports Server (NTRS)

    Lee, Hyoungsoon; Park, Ilchung; Konishi, Christopher; Mudawar, Issam; May, Rochelle I.; Juergens, Jeffery R.; Wagner, James D.; Hall, Nancy R.; Nahra, Henry K.; Hasan, Mohammed M.; Mackey, Jeffery R.

    2013-01-01

    Future manned missions to Mars are expected to greatly increase the space vehicle's size, weight, and heat dissipation requirements. An effective means to reducing both size and weight is to replace single-phase thermal management systems with two-phase counterparts that capitalize upon both latent and sensible heat of the coolant rather than sensible heat alone. This shift is expected to yield orders of magnitude enhancements in flow boiling and condensation heat transfer coefficients. A major challenge to this shift is a lack of reliable tools for accurate prediction of two-phase pressure drop and heat transfer coefficient in reduced gravity. Developing such tools will require a sophisticated experimental facility to enable investigators to perform both flow boiling and condensation experiments in microgravity in pursuit of reliable databases. This study will discuss the development of the Flow Boiling and Condensation Experiment (FBCE) for the International Space Station (ISS), which was initiated in 2012 in collaboration between Purdue University and NASA Glenn Research Center. This facility was recently tested in parabolic flight to acquire condensation data for FC-72 in microgravity, aided by high-speed video analysis of interfacial structure of the condensation film. The condensation is achieved by rejecting heat to a counter flow of water, and experiments were performed at different mass velocities of FC-72 and water and different FC-72 inlet qualities. It is shown that the film flow varies from smooth-laminar to wavy-laminar and ultimately turbulent with increasing FC-72 mass velocity. The heat transfer coefficient is highest near the inlet of the condensation tube, where the film is thinnest, and decreases monotonically along the tube, except for high FC-72 mass velocities, where the heat transfer coefficient is enhanced downstream. This enhancement is attributed to both turbulence and increased interfacial waviness. One-ge correlations are shown to

  4. Particle Size Controls on Water Adsorption and Condensation Regimes at Mineral Surfaces

    PubMed Central

    Yeşilbaş, Merve; Boily, Jean-François

    2016-01-01

    Atmospheric water vapour interacting with hydrophilic mineral surfaces can produce water films of various thicknesses and structures. In this work we show that mineral particle size controls water loadings achieved by water vapour deposition on 21 contrasting mineral samples exposed to atmospheres of up to ~16 Torr water (70% relative humidity at 25 °C). Submicrometer-sized particles hosted up to ~5 monolayers of water, while micrometer-sized particles up to several thousand monolayers. All films exhibited vibrational spectroscopic signals akin to liquid water, yet with a disrupted network of hydrogen bonds. Water adsorption isotherms were predicted using models (1- or 2- term Freundlich and Do-Do models) describing an adsorption and a condensation regime, respectively pertaining to the binding of water onto mineral surfaces and water film growth by water-water interactions. The Hygroscopic Growth Theory could also account for the particle size dependence on condensable water loadings under the premise that larger particles have a greater propensity of exhibiting of surface regions and interparticle spacings facilitating water condensation reactions. Our work should impact our ability to predict water film formation at mineral surfaces of contrasting particle sizes, and should thus contribute to our understanding of water adsorption and condensation reactions occuring in nature. PMID:27561325

  5. Particle Size Controls on Water Adsorption and Condensation Regimes at Mineral Surfaces

    NASA Astrophysics Data System (ADS)

    Yeşilbaş, Merve; Boily, Jean-François

    2016-08-01

    Atmospheric water vapour interacting with hydrophilic mineral surfaces can produce water films of various thicknesses and structures. In this work we show that mineral particle size controls water loadings achieved by water vapour deposition on 21 contrasting mineral samples exposed to atmospheres of up to ~16 Torr water (70% relative humidity at 25 °C). Submicrometer-sized particles hosted up to ~5 monolayers of water, while micrometer-sized particles up to several thousand monolayers. All films exhibited vibrational spectroscopic signals akin to liquid water, yet with a disrupted network of hydrogen bonds. Water adsorption isotherms were predicted using models (1- or 2- term Freundlich and Do-Do models) describing an adsorption and a condensation regime, respectively pertaining to the binding of water onto mineral surfaces and water film growth by water-water interactions. The Hygroscopic Growth Theory could also account for the particle size dependence on condensable water loadings under the premise that larger particles have a greater propensity of exhibiting of surface regions and interparticle spacings facilitating water condensation reactions. Our work should impact our ability to predict water film formation at mineral surfaces of contrasting particle sizes, and should thus contribute to our understanding of water adsorption and condensation reactions occuring in nature.

  6. Experiments on condensation over in-line and staggered condenser tubes in the presence of non-condensable gases

    NASA Astrophysics Data System (ADS)

    Ramadan, Abdulghani; Yamali, Cemil

    2013-12-01

    The problem of the forced film condensation heat transfer of pure steam and steam-air mixture flowing downward a tier of horizontal cylinders is investigated experimentally. An experimental setup was manufactured and mounted at Middle East Technical University workshop. A set of experiments were conducted to observe the condensation heat transfer phenomenon and to verify the theoretical results. The results of the experimental investigation are presented to show the effect of different parameters on the film condensation heat transfer phenomenon over bundle of tubes. These parameters include; free stream velocity, free stream non-condensable gas (air) mass fractions, free stream temperature to wall temperature difference, the angle of inclination. heat transfer coefficients are evaluated at different working conditions for both inline and staggered arrangements. Results show that; a remarked reduction in the vapor side heat transfer coefficient is noticed when very small amounts of air mass fractions present in the vapor. In addition, it decreases by increasing the temperature difference. On the other hand, it increases by increasing the free stream velocity (Reynolds number). Average heat transfer coefficient at the middle and the bottom cylinders increases by increasing the angle of inclination, whereas, no significant change is observed for that of the upper cylinder. Although some discrepancies are noticed, the present study results are inline and in a reasonable agreement with the theory and experiment in the literature.

  7. Crossover from nucleation to spinodal decomposition in a condensing vapor.

    PubMed

    Wedekind, Jan; Chkonia, Guram; Wölk, Judith; Strey, Reinhard; Reguera, David

    2009-09-21

    The mechanism controlling the initial step of a phase transition has a tremendous influence on the emerging phase. We study the crossover from a purely nucleation-controlled transition toward spinodal decomposition in a condensing Lennard-Jones vapor using molecular dynamics simulations. We analyze both the kinetics and at the same time the thermodynamics by directly reconstructing the free energy of cluster formation. We estimate the location of the spinodal, which lies at much deeper supersaturations than expected. Moreover, the nucleation barriers we find differ only by a constant from the classical nucleation theory predictions and are in very good agreement with semiempirical scaling relations. In the regime from very small barriers to the spinodal, growth controls the rate of the transition but not its nature because the activation barrier has not yet vanished. Finally, we discuss in detail the influence of the chosen reaction coordinate on the interpretation of such simulation results.

  8. Slag condensation kinetics in the channel of an MHD generator: Explosive condensation

    SciTech Connect

    Zhukhovitskii, D.I.; Khrapak, A.G.; Yakubov, I.T.

    1983-09-01

    A study has been made of the bulk condensation of the inorganic part of combustion products in the channel of an MHD generator. An analytic solution has been obtained to the equations describing the process. A physical interpretation is given for the various stages. It is known that the condensation consists of several slightly overlapping stages. First there is the explosive formation of nuclei, which then grow rapidly, and a quasistationary stage of condensation sets in. A calculation is performed for particular conditions in an MHD generator.

  9. Enhancing Condensers for Geothermal Systems: the Effect of High Contact Angles on Dropwise Condensation Heat Transfer

    SciTech Connect

    Kennedy, John M.; Kim, Sunwoo; Kim, Kwang J.

    2009-10-06

    Phase change heat transfer is notorious for increasing the irreversibility of, and therefore decreasing the efficiency of, geothermal power plants. Its significant contribution to the overall irreversibility of the plant makes it the most important source of inefficiency in the process. Recent studies here have shown the promotion of drop wise condensation in the lab by means of increasing the surface energy density of a tube with nanotechnology. The use of nanotechnology has allowed the creation of surface treatments which discourage water from wetting a tube surface during a static test. These surface treatments are unique in that they create high- contact angles on the condensing tube surfaces to promote drop wise condensation.

  10. Condensation Enhancement by Surface Porosity: Three-Stage Mechanism.

    PubMed

    Yarom, Michal; Marmur, Abraham

    2015-08-18

    Surface defects, such as pores, cracks, and scratches, are naturally occurring and commonly found on solid surfaces. However, the mechanism by which such imperfections promote condensation has not been fully explored. In the current paper we thermodynamically analyze the ability of surface porosity to enhance condensation on a hydrophilic solid. We show that the presence of a surface-embedded pore brings about three distinct stages of condensation. The first is capillary condensation inside the pore until it is full. This provides an ideal hydrophilic surface for continuing the condensation. As a result, spontaneous condensation and wetting can be achieved at lower vapor pressure than on a smooth surface.

  11. Dropwise condensation on a cold gradient substrate

    NASA Astrophysics Data System (ADS)

    Macner, Ashley; Daniel, Susan; Steen, Paul

    2012-11-01

    Distributions of drops that arise from dropwise condensation evolve by nucleation, growth, and coalescence of drops. An understanding of how surface-energy gradients applied to the substrate affect drop growth and coalescence is needed for design of effective surfaces for large-scale dropwise condensation. Transient dropwise condensation from a vapor phase onto a cold and chemically treated surface is reported. The surfaces were treated to deliver either a uniform contact-angle or a gradient of contact-angles by silanization. The time evolution of drop-size and number-density distributions is reported. For a typical condensation experiment, the drop distributions advance through two stages: an increase in drop density as a result of nucleation and a decrease in drop density as a result of larger scale coalescence events. Because the experiment is transient in nature, the shape of the distribution can be used to predict the number of drop generations and their stage of development. Preliminary results for gradient surfaces will be discussed and compared against observations of behavior on uniformly coated surfaces. NASA Space Technology Research Fellowship (NSTRF).

  12. ISOSPIN BREAKING AND THE CHIRAL CONDENSATE.

    SciTech Connect

    CREUTZ, M.

    2005-07-25

    With two degenerate quarks, the chiral condensate exhibits a jump as the quark masses pass through zero. I discuss how this single transition splits into two Ising like transitions when the quarks are made non-degenerate. The order parameter is the expectation of the neutral pion field. The transitions represent long distance coherent phenomena occurring without the Dirac operator having vanishingly small eigenvalues.

  13. Ultrafine Condensation Particle Counter Instrument Handbook

    SciTech Connect

    Kuang, C.

    2016-02-01

    The Model 3776 Ultrafine Condensation Particle Counter (UCPC; pictured in Appendix A) is designed for researchers interested in airborne particles smaller than 20 nm. With sensitivity to particles down to 2.5 nm in diameter, this UCPC is ideally suited for atmospheric and climate research, particle formation and growth studies, combustion and engine exhaust research, and nanotechnology research.

  14. 242-A evaporator vacuum condenser system

    SciTech Connect

    Smith, V.A.

    1994-09-28

    This document is written for the 242-A evaporator vacuum condenser system (VCS), describing its purpose and operation within the evaporator. The document establishes the operating parameters specifying pressure, temperature, flow rates, interlock safety features and interfacing sub-systems to support its operation.

  15. Condensate-removal device for heat exchangers

    NASA Technical Reports Server (NTRS)

    Trusch, R. B.; Oconnor, E. W.

    1973-01-01

    Device comprises array of perforated tubes manifolded together and connected to a vacuum suction device. Vacuum applied to these tubes pulls mixture of condensate and effluent gas through perforations and along length of tubes to discharge device. Discharge device may be a separator which separates water vapor from effluent air and allows recirculation of both of them.

  16. Tachyon condensation and black hole entropy.

    PubMed

    Dabholkar, Atish

    2002-03-04

    String propagation on a cone with deficit angle 2pi(1-1 / N) is considered for the purpose of computing the entropy of a large mass black hole. The entropy computed using the recent results on condensation of twisted-sector tachyons in this theory is found to be in precise agreement with the Bekenstein-Hawking entropy.

  17. Capillary condensation as a morphological transition.

    PubMed

    Kornev, Konstantin G; Shingareva, Inna K; Neimark, Alexander V

    2002-02-25

    The process of capillary condensation/evaporation in cylindrical pores is considered within the idea of symmetry breaking. Capillary condensation/evaporation is treated as a morphological transition between the wetting film configurations of different symmetry. We considered two models: (i) the classical Laplace theory of capillarity and (ii) the Derjaguin model which takes into account the surface forces expressed in terms of the disjoining pressure. Following the idea of Everett and Haynes, the problem of condensation/evaporation is considered as a transition from bumps/undulations to lenses. Using the method of phase portraits, we discuss the mathematical mechanisms of this transition hidden in the Laplace and Derjaguin equations. Analyzing the energetic barriers of the bump and lens formation, it is shown that the bump formation is a prerogative of capillary condensation: for the vapor-liquid transition in a pore, the bump plays the same role as the spherical nucleus in a bulk fluid. We show also that the Derjaguin model admits a variety of interfacial configurations responsible for film patterning at specific conditions.

  18. Condensing Organic Aerosols in a Microphysical Model

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Tsigaridis, K.; Bauer, S.

    2015-12-01

    The condensation of organic aerosols is represented in a newly developed box-model scheme, where its effect on the growth and composition of particles are examined. We implemented the volatility-basis set (VBS) framework into the aerosol mixing state resolving microphysical scheme Multiconfiguration Aerosol TRacker of mIXing state (MATRIX). This new scheme is unique and advances the representation of organic aerosols in models in that, contrary to the traditional treatment of organic aerosols as non-volatile in most climate models and in the original version of MATRIX, this new scheme treats them as semi-volatile. Such treatment is important because low-volatility organics contribute significantly to the growth of particles. The new scheme includes several classes of semi-volatile organic compounds from the VBS framework that can partition among aerosol populations in MATRIX, thus representing the growth of particles via condensation of low volatility organic vapors. Results from test cases representing Mexico City and a Finish forrest condistions show good representation of the time evolutions of concentration for VBS species in the gas phase and in the condensed particulate phase. Emitted semi-volatile primary organic aerosols evaporate almost completely in the high volatile range, and they condense more efficiently in the low volatility range.

  19. Convection in Condensible-rich Atmospheres

    NASA Astrophysics Data System (ADS)

    Ding, F.; Pierrehumbert, R. T.

    2016-05-01

    Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO2 is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

  20. Free convective condensation in a vertical enclosure

    SciTech Connect

    Fox, R.J.; Peterson, P.F.; Corradini, M.L.; Pernsteiner, A.P.

    1995-09-01

    Free convective condensation in a vertical enclosure was studied numerically and the results were compared with experiments. In both the numerical and experimental investigations, mist formation was observed to occur near the cooling wall, with significant droplet concentrations in the bulk. Large recirculation cells near the end of the condensing section were generated as the heavy noncondensing gas collecting near the cooling wall was accelerated downward. Near the top of the enclosure the recirculation cells became weaker and smaller than those below, ultimately disappearing near the top of the condenser. In the experiment the mist density was seen to be highest near the wall and at the bottom of the condensing section, whereas the numerical model predicted a much more uniform distribution. The model used to describe the formation of mist was based on a Modified Critical Saturation Model (MCSM), which allows mist to be generated once the vapor pressure exceeds a critical value. Equilibrium, nonequilibrium, and MCSM calculations were preformed, showing the experimental results to lie somewhere in between the equilibrium and nonequilibrium predictions of the numerical model. A single adjustable constant (indicating the degree to which equilibrium is achieved) is used in the model in order to match the experimental results.

  1. Condensation in a two-phase pool

    SciTech Connect

    Duffey, R.B. ); Hughes, E.D. )

    1991-01-01

    We consider the case of vapor condensation in a liquid pool, when the heat transfer is controlled by heat losses through the walls. The analysis is based on drift flux theory for phase separation in the pool, and determines the two-phase mixture height for the pool. To our knowledge this is the first analytical treatment of this classic problem that gives an explicit result, previous work having established the result for the evaporative case. From conservation of mass and energy in a one-dimensional steady flow, together with a void relation between the liquid and vapor fluxes, we determine the increase in the mixture level from the base level of the pool. It can be seen that the thermal and hydrodynamic influences are separable. Thus, the thermal influence of the wall heat transfer appears through its effect on the condensing length L*, so that at high condensation rates the pool is all liquid, and at low rates overflows (the level swell or foaming effect). Similarly, the phase separation effect hydrodynamically determines the height via the relative velocity of the mixture to the entering flux. We examine some practical applications of this result to level swell in condensing flows, and also examine some limits in ideal cases.

  2. Condensation in a two-phase pool

    SciTech Connect

    Duffey, R.B.; Hughes, E.D.

    1991-12-31

    We consider the case of vapor condensation in a liquid pool, when the heat transfer is controlled by heat losses through the walls. The analysis is based on drift flux theory for phase separation in the pool, and determines the two-phase mixture height for the pool. To our knowledge this is the first analytical treatment of this classic problem that gives an explicit result, previous work having established the result for the evaporative case. From conservation of mass and energy in a one-dimensional steady flow, together with a void relation between the liquid and vapor fluxes, we determine the increase in the mixture level from the base level of the pool. It can be seen that the thermal and hydrodynamic influences are separable. Thus, the thermal influence of the wall heat transfer appears through its effect on the condensing length L*, so that at high condensation rates the pool is all liquid, and at low rates overflows (the level swell or foaming effect). Similarly, the phase separation effect hydrodynamically determines the height via the relative velocity of the mixture to the entering flux. We examine some practical applications of this result to level swell in condensing flows, and also examine some limits in ideal cases.

  3. Spermine Condenses DNA, but Not RNA Duplexes

    SciTech Connect

    Katz, Andrea M.; Tolokh, Igor S.; Pabit, Suzette A.; Baker, Nathan; Onufriev, Alexey V.; Pollack, Lois

    2017-01-01

    Interactions between the polyamine spermine and nucleic acids drive important cellular processes. Spermine condenses DNA, and some RNAs such as poly(rA):poly(rU). A large fraction of the spermine present in cells is bound to RNA, but apparently does not condense it. Here, we study the effect of spermine binding to short duplex RNA and DNA and compare our findings with predictions of molecular dynamics simulations. When small numbers of spermine are introduced, RNA with a designed sequence, containing a mixture of 14 GC pairs and 11 AU pairs, resists condensation relative to DNA of an equivalent sequence or to 25 base pair poly(rA):poly(rU) RNA. Comparison of wide-angle x-ray scattering profiles with simulation suggests that spermine is sequestered deep within the major groove of mixed sequence RNA, preventing condensation by limiting opportunities to bridge to other molecules as well as stabilizing the RNA by locking it into a particular conformation. In contrast, for DNA, simulations suggest that spermine binds external to the duplex, offering opportunities for intermolecular interaction. The goal of this study is to explain how RNA can remain soluble, and available for interaction with other molecules in the cell, despite the presence of spermine at concentrations high enough to precipitate DNA.

  4. Counterion condensation and release in micellar solutions

    NASA Astrophysics Data System (ADS)

    Hsiao, Chin Chieh; Wang, Tzu-Yu; Tsao, Heng-Kwong

    2005-04-01

    Counterion condensation and release in micellar solutions are investigated by direct measurement of counterion concentration with ion-selective electrode. Monte Carlo simulations based on the cell model are also performed to analyze the experimental results. The degree of counterion condensation is indicated by the concentration ratio of counterions in the bulk to the total ionic surfactant added, α⩽1. The ionic surfactant is completely dissociated below the critical micelle concentration (cmc). However, as cmc is exceeded, the free counterion ratio α declines with increasing the surfactant concentration and approaches an asymptotic value owing to counterion condensation to the surface of the highly charged micelles. Micelle formation leads to much stronger electrostatic attraction between the counterion and the highly charged sphere in comparison to the attraction of single surfactant ion with its counterion. A simple model is developed to obtain the true degree of ionization, which agrees with our Monte Carlo results. Upon addition of neutral polymer or monovalent salts, some of the surfactant counterions are released to the bulk. The former is due to the decrease of the intrinsic charge (smaller aggregation number) and the degree of ionization is increased. The latter is attributed to competitive counterion condensation, which follows the Hefmeister series. This consequence indicates that the specific ion effect plays an important role next to the electrostatic attraction.

  5. Activity, purification, and analysis of condensed tannins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a class of plant polyphenolic compounds contained in some forages (i.e., sanfoin, big trefoil, birdfoot trefoil), condensed tannins (CTs), also referred to as proanthocyanidins (PAs), exhibit a variety of biological effects on ruminants and on the dairy farm nitrogen cycle. Interest in CTs stems ...

  6. Condensation in Saturn's Stratospheric Haze Layers

    NASA Astrophysics Data System (ADS)

    Barth, Erika L.; Moses, Julianne I.

    2016-10-01

    Haze particles in Saturn's stratosphere can be seen in the visible limb images of Cassini's Imaging Science Subsystem (ISS). These hazes are likely a mix of particles, including solid organics formed as a result of methane photolysis and electron deposition, as well as the condensation of water and hydrocarbon ices. We have examined data from both Cassini and Voyager to study the detailed vertical structure of absorbing/scattering particulates in Saturn's stratosphere and developed a Saturn version of the Community Aerosol and Radiation Model for Atmospheres (CARMA), adding a large database of hydrocarbons that are observed or expected to be present in Saturn's atmosphere.Our modeling indicates that water ice condenses independently of the hydrocarbons to form a thin layer above the 0.1 mbar pressure level. Between about 5 and 50 mbar, the hydrocarbons reach their condensation levels (in order of increasing pressure level): C6H6, C5H12, C4H2, C4H10, and C2H2. Because of the proximity of their condensation levels and due to the gravitational settling of the particles, the hydrocarbons are likely condensing on one another and forming a thicker layer of mixed composition. Interestingly, butane (C4H10) has a triple point around 135 K which is much lower than most of the other condensing species we've explored. Given an approximate condensation level of 10 mbar and the observed temperature changes at this pressure level following the December 2010 northern-hemisphere storm (stratospheric temperatures were elevated by as much as 50-70 K in a region near 40° N latitude.), melting and further nucleation of droplets could be occurring.A number of factors including temperature profile, vapor pressure equation, volatile abundance, nucleation critical saturation, and coagulation efficiency will affect the altitudes of the individual ice layers. We will present a summary of results following the nucleation and growth of compounds in order to quantify the likely size and

  7. Homogeneous cosmologies as group field theory condensates

    NASA Astrophysics Data System (ADS)

    Gielen, Steffen; Oriti, Daniele; Sindoni, Lorenzo

    2014-06-01

    We give a general procedure, in the group field theory (GFT) formalism for quantum gravity, for constructing states that describe macroscopic, spatially homogeneous universes. These states are close to coherent (condensate) states used in the description of Bose-Einstein condensates. The condition on such states to be (approximate) solutions to the quantum equations of motion of GFT is used to extract an effective dynamics for homogeneous cosmologies directly from the underlying quantum theory. The resulting description in general gives nonlinear and nonlocal equations for the `condensate wavefunction' which are analogous to the Gross-Pitaevskii equation in Bose-Einstein condensates. We show the general form of the effective equations for current quantum gravity models, as well as some concrete examples. We identify conditions under which the dynamics becomes linear, admitting an interpretation as a quantum-cosmological Wheeler-DeWitt equation, and give its semiclassical (WKB) approximation in the case of a kinetic term that includes a Laplace-Beltrami operator. For isotropic states, this approximation reproduces the classical Friedmann equation in vacuum with positive spatial curvature. We show how the formalism can be consistently extended from Riemannian signature to Lorentzian signature models, and discuss the addition of matter fields, obtaining the correct coupling of a massless scalar in the Friedmann equation from the most natural extension of the GFT action. We also outline the procedure for extending our condensate states to include cosmological perturbations. Our results form the basis of a general programme for extracting effective cosmological dynamics directly from a microscopic non-perturbative theory of quantum gravity.

  8. Cloud Condensation in Titan's Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Romani, Paul N.; Anderson, Carrie M.

    2011-01-01

    A 1-D condensation model is developed for the purpose of reproducing ice clouds in Titan's lower stratosphere observed by the Composite Infrared Spectrometer (CIRS) onboard Cassini. Hydrogen cyanide (HCN), cyanoacetylene (HC3N), and ethane (C2H6) vapors are treated as chemically inert gas species that flow from an upper boundary at 500 km to a condensation sink near Titan's tropopause (-45 km). Gas vertical profiles are determined from eddy mixing and a downward flux at the upper boundary. The condensation sink is based upon diffusive growth of the cloud particles and is proportional to the degree of supersaturation in the cloud formation regIOn. Observations of the vapor phase abundances above the condensation levels and the locations and properties of the ice clouds provide constraints on the free parameters in the model. Vapor phase abundances are determined from CIRS mid-IR observations, whereas cloud particle sizes, altitudes, and latitudinal distributions are derived from analyses of CIRS far-IR observations of Titan. Specific cloud constraints include: I) mean particle radii of2-3 J.lm inferred from the V6 506 cm- band of HC3N, 2) latitudinal abundance distributions of condensed nitriles, inferred from a composite emission feature that peaks at 160/cm , and 3) a possible hydrocarbon cloud layer at high latitudes, located near an altitude of 60 km, which peaks between 60 and 80 cm l . Nitrile abundances appear to diminish substantially at high northern latitudes over the time period 2005 to 2010 (northern mid winter to early spring). Use of multiple gas species provides a consistency check on the eddy mixing coefficient profile. The flux at the upper boundary is the net column chemical production from the upper atmosphere and provides a constraint on chemical pathways leading to the production of these compounds. Comparison of the differing lifetimes, vapor phase transport, vapor phase loss rate, and particle sedimentation, sheds light on temporal stability

  9. Oxidation-Reduction Condensation of Diazaphosphites for Carbon-Heteroatom Bond Formation Based on Mitsunobu Mechanism.

    PubMed

    Huang, Hai; Kang, Jun Yong

    2017-02-03

    An efficient oxidation-reduction condensation reaction of diazaphosphites with various nonacidic pronucleophiles in the presence of DIAD as a weak oxidant has been developed for carbon-heteroatom bond formation. This mild process affords structurally diverse tertiary amines, secondary amines, esters, ethers, and thioethers in moderate to excellent yields. The selective synthesis of secondary amines from primary amines has been achieved. Importantly, a practical application to the synthesis of antiparkinsonian agent piribedil has been demonstrated.

  10. Model Condensation for Non-Classically Damped SYSTEMS—PART i: Static Condensation

    NASA Astrophysics Data System (ADS)

    Qu, Z.-Q.; Jung, Y.; Selvam, R. P.

    2003-09-01

    Three condensation methods for the model reduction of non-classically damped systems are presented. One is defined in the displacement space and the other two are defined in the state space. Since the damping and inertia forces on all degrees of freedom of the full model are ignored, these algorithms are considered as the static condensation. One advantage of these condensation methods is that the explicit forms of the reduced stiffness, mass, and damping matrices can be directly obtained from the reduced model. These explicit reduced system matrices are very useful in further dynamic analyses. These approaches are compared from the assumptions, condensation matrices, computational work and the reduced system matrices. With the introduction of the generalised inverse of matrix, the method defined in the displacement space is extended and one variant is derived. Numerical examples, one three-degree-of-freedom discrete system and one floating raft isolation system, are applied to demonstrate the features of these methods.

  11. The effect of condensate inundation on steam condensation heat transfer to wire-wrapped tubing

    NASA Astrophysics Data System (ADS)

    Kanakis, G. D.

    1983-06-01

    Steam condensation heat transfer measurements were made in a 5-tube test condenser having an additional perforated tube to simulate up to 30 active tubes. Results were obtained for smooth tubes and roped tubes wrapped with wire. A Sieder-Tate equation was used to correlate the inside heat-transfer coefficient. For smooth tubes, a leading coefficient of 0.029 was found, while it was 0.061 for the roped tubes. The average condensing coefficient measured for 30 smooth tubes was 0.59 times the Nusselt coefficient calculated for the first tube. When the smooth tubes were wrapped with wire, this ratio increased up to 0.86. Further, roped tubes without wire experienced a ratio of 0.63, while roped tubes wrapped with wire resulted in a ratio of 0.86. These preliminary data show that wire-wrapped tubes may lead to a significant reduction in condenser surface area.

  12. Reactions of buffers in cyanogen bromide-induced ligations.

    PubMed

    Vogel, Heike; Gerlach, Claudia; Richert, Clemens

    2013-01-01

    Rapid, template-directed ligation reactions between a phosphate-terminated oligonucleotide and an unphosphorylated reaction partner may be induced by cyanogen bromide (BrCN). Frequently, however, the reaction is low yielding, and even a large excess of the condensing agent can fail to induce quantitative conversions. In this study, we used BrCN to induce chemical primer extension reactions. Here, we report that buffers containing hydroxyl groups react with short oligodeoxynucleotides in the presence of BrCN. One stable adduct between HEPBS buffer and cytosine was characterized by mass spectrometry and NMR after HPLC purification, indicating that a side reaction occurred at this nucleobase. Further, a first example of a primer extension reaction between an unmodified oligodeoxynucleotide as primer and dGMP is reported. Together, our results shed light on the potency, as well as the drawbacks of BrCN as a highly reactive condensing reagent for the ligation of unmodified nucleic acids.

  13. Condensation of water vapor in the gravitational field

    SciTech Connect

    Gorshkov, V. G.; Makarieva, A. M.; Nefiodov, A. V.

    2012-10-15

    Physical peculiarities of water vapor condensation under conditions of hydrostatic equilibrium are considered. The power of stationary dynamic air fluxes and the vertical temperature distribution caused by condensation on large horizontal scales are estimated.

  14. 39. GENERAL VIEW OF VIVIANNA WORKS CONDENSING CHANNEL CONNECTING TO ...

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

    39. GENERAL VIEW OF VIVIANNA WORKS CONDENSING CHANNEL CONNECTING TO MARISCAL WORKS STACK BEING REUSED AS FINAL CONDENSER LOOKING EAST, NORTHEAST. STONE STRUCTURE IN FOREGROUND UNKNOWN. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  15. Microwave-assisted and efficient solvent-free knoevenagel condensation. A sustainable protocol using porous calcium hydroxyapatite as catalyst.

    PubMed

    Mallouk, Siham; Bougrin, Khalid; Laghzizil, Abdelaziz; Benhida, Rachid

    2010-02-04

    A sustainable Knoevenagel condensation of a series of aldehydes with malononitrile and ethyl cyanoacetate is described. The process is based on the combination of microwave activation and hydroxyapatite catalysis under solvent-free conditions. Products are obtained in and high yields after short reaction times. The effects of the specific surface of porous calcium hydroxyapatite and microwave activation are discussed.

  16. Bose-Einstein condensates form in heuristics learned by ciliates deciding to signal 'social' commitments.

    PubMed

    Clark, Kevin B

    2010-03-01

    Fringe quantum biology theories often adopt the concept of Bose-Einstein condensation when explaining how consciousness, emotion, perception, learning, and reasoning emerge from operations of intact animal nervous systems and other computational media. However, controversial empirical evidence and mathematical formalism concerning decoherence rates of bioprocesses keep these frameworks from satisfactorily accounting for the physical nature of cognitive-like events. This study, inspired by the discovery that preferential attachment rules computed by complex technological networks obey Bose-Einstein statistics, is the first rigorous attempt to examine whether analogues of Bose-Einstein condensation precipitate learned decision making in live biological systems as bioenergetics optimization predicts. By exploiting the ciliate Spirostomum ambiguum's capacity to learn and store behavioral strategies advertising mating availability into heuristics of topologically invariant computational networks, three distinct phases of strategy use were found to map onto statistical distributions described by Bose-Einstein, Fermi-Dirac, and classical Maxwell-Boltzmann behavior. Ciliates that sensitized or habituated signaling patterns to emit brief periods of either deceptive 'harder-to-get' or altruistic 'easier-to-get' serial escape reactions began testing condensed on initially perceived fittest 'courting' solutions. When these ciliates switched from their first strategy choices, Bose-Einstein condensation of strategy use abruptly dissipated into a Maxwell-Boltzmann computational phase no longer dominated by a single fittest strategy. Recursive trial-and-error strategy searches annealed strategy use back into a condensed phase consistent with performance optimization. 'Social' decisions performed by ciliates showing no nonassociative learning were largely governed by Fermi-Dirac statistics, resulting in degenerate distributions of strategy choices. These findings corroborate

  17. Determination of methadone in exhaled breath condensate by liquid chromatography-tandem mass spectrometry.

    PubMed

    Beck, Olof; Sandqvist, Sören; Eriksen, Paul; Franck, Johan; Palmskog, Göran

    2011-04-01

    Within the field of toxicology exhaled breath is used as specimen only for determination of alcohol. However, it was recently discovered that when using sensitive liquid chromatography-mass spectrometry (LC-MS) technique, amphetamine, methamphetamine, and methadone are detectable in exhaled breath following intake by drug addicts. We therefore undertook to develop a method for determination of methadone in exhaled breath condensate from patients undergoing methadonemaintenance treatment. Exhaled breath condensate was collected from 14 patients after intake of the daily methadone dose. The exhaled breath condensate was collected for 10 min using an Ecoscreen instrument. After extraction of any trapped methadone from the condensate by solid-phase extraction, the final extract was analyzed by a combined LC-MS-MS method. Recovery of methadone from breath condensate in the solid-phase extraction was 104%, no significant matrix effects were observed, and the quantification using methadone-d(3) as internal standard was accurate (10% bias) and precise (coefficient of variation 6.2%). Methadone was indisputably identified by means of the MS technique in exhaled breath condensate from all 14 patients. Identification was based on monitoring two product ions in selected reaction monitoring mode with correct relative ratio (± 20%) and correct retention time. Excretion rates ranged from 23.6 to 275 pg/min. No methadone was detected in five control subjects (< 2 pg/min). This finding confirms that methadone is present in exhaled breath from patients in methadone treatment. Collection of exhaled breath specimen is likely to be complementary to other matrices presently in use in testing for drugs-of-abuse.

  18. Spatial dynamics, thermalization, and gain clamping in a photon condensate

    NASA Astrophysics Data System (ADS)

    Keeling, Jonathan; Kirton, Peter

    2016-01-01

    We study theoretically the effects of pump-spot size and location on photon condensates. By exploring the inhomogeneous molecular excitation fraction, we make clear the relation between spatial equilibration, gain clamping, and thermalization in a photon condensate. This provides a simple understanding of several recent experimental results. We find that as thermalization breaks down, gain clamping is imperfect, leading to "transverse spatial hole burning" and multimode condensation. This opens the possibility of engineering the gain profile to control the condensate structure.

  19. New practical synthesis of indazoles via condensation of o-fluorobenzaldehydes and their O-methyloximes with hydrazine.

    PubMed

    Lukin, Kirill; Hsu, Margaret C; Fernando, Dilinie; Leanna, M Robert

    2006-10-13

    The reaction of o-fluorobenzaldehydes and their O-methyloximes with hydrazine has been developed as a new practical synthesis of indazoles. Utilization of the methyloxime derivatives of benzaldehydes (in the form of the major E-isomers) in this condensation effectively eliminated a competitive Wolf-Kishner reduction to fluorotoluenes, which was observed in the direct preparations of indazoles from aldehydes. Reaction of Z-isomers of methyloximes with hydrazine resulted in the formation of 3-aminoindazoles via a benzonitrile intermediate.

  20. Cloud condensation nuclei (CCN) activity of aliphatic amine secondary aerosol

    NASA Astrophysics Data System (ADS)

    Tang, X.; Price, D.; Praske, E.; Vu, D. N.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

    2014-06-01

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g., hydroxyl radical and nitrate radical). The particle can contain both secondary organic aerosol (SOA) and inorganic salts. The ratio of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ, ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3) contains less volatile compounds than the primary aliphatic amine (BA) aerosol. As relative humidity (RH) increases, inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. The humid BA + N2O5 aerosol products were found to be very sensitive to the temperature at which the measurements were made within the streamwise continuous-flow thermal gradient CCN counter; κ ranges from 0.4 to 0.7 dependent on the instrument supersaturation (ss) settings. The variance of the measured aerosol κ values indicates that simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems' κ ranges within 0.2 < κ < 0.7. This work indicates that aerosols formed via nighttime reactions with amines are likely to produce hygroscopic and volatile aerosol, whereas photochemical reactions with OH produce secondary organic aerosol of lower CCN activity. The contributions of semivolatile secondary organic and inorganic material from aliphatic amines must be considered for accurate hygroscopicity and CCN predictions from aliphatic amine systems.